Remi Julio
email: remi.julio@ensiacet.fr

Joël Albet

Claire Vialle

Carlos Vaca-Garcia

Caroline Sablayrolles

M Et Kamm

Sustainable design of biorefi nery processes: existing practices and new methodology

Keywords: Life Cycle Assessment, eco-design, sustainability, modeling, process simulation, biorefi nery, biomass, multi-objective optimization, decision-making process Figure 1. Analogy between petroleum refi ning and biorefi ning principles, from Kamm B

Nowadays, eco-designing products is increasingly practiced. The next challenge for sustain-ability is to optimize production processes. Biorefi neries are particularly concerned with this improve-ment, because they use renewable resources. To identify the contribution of transformation processes to the overall environmental impacts, Life Cycle Assessment (LCA) appears as the adequate method. A literature review highlights that LCA is mainly performed on biorefi neries to compare biomass feed-stocks between them and to a fossil reference. Another part of environmental LCA compares the impacts of different processing routes. Nevertheless, these evaluations concern already designed pro-cesses. Generally, processes are considered as a unique operation in assessments. However, some criteria like operating can notably modify environmental burdens. The eco-design of biorefi nery pro-cesses can be guided by coupling process simulation to LCA. This method has been emerging in the chemical sector in recent years. Consequently, this paper proposes a new methodological approach to assessing the complete sustainability of biorefi nery processes, since its fi rst design stages. In addi-tion to coupling process simulation and environmental LCA, the other pillars of sustainability will be assessed. Indeed, Life Cycle Costing and Social Life Cycle Assessment can be performed to obtain an integrated methodological framework. The simultaneous optimization of the environmental, economic, and social performances of the process can lead to antagonist ways of improving. Consequently, compromises should be realized. Thereby, the multiobjective optimization can be accomplished by a metaheuristic method supported by a decisionmaking tool. Finally, the main limits of this method and some perspectives and ways for improving are discussed.

Introduction

S

ince the beginning of the Industrial Revolution, worldwide development and the global economy have been based on the use of fossil resources, mainly petroleum, coal, and natural gas. For the fi rst time in the modern history of human society, this growth is threatened. Actually, the current way of development brings out two major issues: the depletion of fossil reserves and the constant increase of environmental damages. Consequently, one of the most important challenges is to establish the future of the global industry, which has to be based on the use of renewable resources, having a long-term vision and respecting the requirements of sustainability.

In 1987, a defi nition of sustainable development was proposed by the World Commission on Environment and Development (WECD): sustainable development is a development that meets the needs of the present without compromising the ability of future generations to meet their own needs. [START_REF] Brundtland | Our Common Future ('Brundtland report[END_REF] Basically, making a system more sustainable is to make it progress simultaneously on three dimensions: economy, social, and environment. [START_REF] Sikdar | Sustainable development and sustainability metrics[END_REF] To fi ght against the degradation of the environment, Life Cycle Assessment (LCA) seems to be the most powerful tool. [START_REF] Jolliet | Analyse du cycle de vie: Comprendre et réaliser un écobilan[END_REF] Indeed, sustainable development and LCA are closely linked. [START_REF] Keoleian | Sustainable development by design: review of life cycle design and related approaches[END_REF][START_REF] Jiménez-González | Bioprocesses: Modeling needs for process evaluation and sustainability assessment[END_REF] Moreover, biorefi neries appear as the most logical substitute of petroleum-based refi neries. Indeed, this emerging concept permits to develop a wide range of bio-based products, such as chemicals, fuels, base molecules for other applications, etc. Moreover, biorefi neries could be implemented everywhere, and plenty of current industries could be transformed into biorefi neries, as pulp and paper plants for instance [START_REF] Sixta | A new generation kraft process[END_REF] or sugar can industries. [START_REF] Martínez-Guido | Optimal reconfi guration of a sugar cane industry to yield an integrated biorefi nery[END_REF] However, the assessment of the environmental performances of these biorefi ning activities is crucial, to justify the expected benefi ts of such operations contrary to classical production routes.

Th is paper presents for the fi rst time the biorefi nery concept and the environmental LCA methodology. Th is section also highlights the interest of using LCA to assess biorefi neries. Secondly, a state-of-the-art environmental LCA of biorefi nery processes is detailed. Th is literature review off ers the opportunity to identify improvement opportunities, and so on to propose a new methodology to perform Life Cycle Sustainability Assessments (LCSA) of high-detailed biorefi ning processes. Th is methodology is based on coupling process simulation and LCA. Th e three dimensions of sustainable development are assessed, and a multi-objective optimization is performed. Finally, some of the future main challenges and limits of this new methodological framework are explored.

Assessing biorefi nery processes with LCA: a necessity

Biorefi nery concept

Nowadays, there is an urgent necessity to develop alternatives to fossil resources-based industry. [START_REF] Laurent | Le bioraffi nage, une alternative prometteuse à la pétrochimie[END_REF] Th ese nonrenewable materials not only provide energy, but also a wide variety of organic chemicals. Biomass appears like the most promising option to cover these applications. [START_REF] Ghatak | Biorefi neries from the perspective of sustainability: Feedstocks, products, and processes[END_REF][START_REF] Ragauskas | The path forward for biofuels and biomaterials[END_REF] Th e term biomass designates renewable organic matter, like trees, agricultural crops, algae, and various residues or wastes.

Th e emerging concept of industries able to create a large range of products from renewable resources is called biorefi ning. [START_REF] Gwehenberger | Sustainable processes-The challenge of the 21st century for chemical engineering[END_REF] Th is term puts in evidence the important similarities with petroleum refi neries. Indeed, multiple products can be generated from a biomass feedstock, which lead to maximize the utilization of raw materials. Th is analogy is represented in Fig. 1.

Th e working fi eld of biorefi nery systems started its development since the beginning of the 1990s. Th e biorefi nery concept was defi ned for the fi rst time in 1997: green biorefi neries represent complex (to fully integrated) systems of sustainable, environment and resource-friendly technologies for the comprehensive (holistic) utilization and the exploitation of biological raw materials in the form of green and residue biomass from a targeted sustainable regional land utilization. [START_REF] Kamm | The green biorefi nery, concept of technology[END_REF] A biorefi nery can also be defi ned as sustainable processing of biomass into a spectrum of marketable products (food, feed, materials, and chemicals) and energy (fuels, power, and heat). [START_REF] Sonnenberg | IEA Bioenergy Task 42 Biorefi nery[END_REF] Th e American National Renewable Energy Laboratory (NREL) published the defi nition: 'a biorefi nery is a facility that integrates biomass conversion processes and equipment to produce fuels, power, and chemicals from biomass. Th e biorefi nery concept is analogous to today's petroleum refi neries, which produce multiple fuels and products from petroleum. Industrial biorefi neries have been identifi ed as the most promising route to the creation of a new domestic bio-based industry.' [START_REF]Conceptual biorefi nery[END_REF] Depending on the type of raw materials used to produce biofuels [START_REF] Ogier | Ethanol production from lignocellulosie biomass[END_REF] and bio-based products, [START_REF] Fernando | Biorefi neries: current status, challenges, and future direction[END_REF][START_REF] Werpy | Top value added chemicals from biomass. Volume 1-Results of screening for potential candidates from sugars and synthesis gas[END_REF] biorefi neries can be classifi ed into three generations. Th erefore, fi rst-generation biorefi neries are based on the direct use of traditional forms of agricultural biomass, such as corn, maize, sugarcane, or soybean. Second-generation types use lignocellulosic feedstock, mainly composed of cellulose, hemicellulose, and lignin. Finally, industrial facilities which use agricultural residues, forestry, petroleum, and urban waste, or microalgae as feedstock biomass constitute the third generation. [START_REF] Parajuli | Biorefi ning in the prevailing energy and materials crisis: a review of sustainable pathways for biorefi nery value chains and sustainability assessment methodologies[END_REF][START_REF] Azapagic | Sustainability considerations for integrated biorefi neries[END_REF] In some publications, a fourth generation is described: the 'biorefi nery two-platform concept' , where biomass is treated simultaneously by a sugar and a syngas platform. [START_REF] Kamm | Biorefi neries -Multi Product Processes[END_REF] Currently, fi rst-generation biorefi neries are the most developed around the world, and particularly in the USA, Canada, and Brazil. Nevertheless, this type of biorefi nery is increasingly contested, for two main reasons: change of land use and competition with food production. As a consequence, there is a growing interest for lignocellulosic feedstock, which is low-priced and abundant. [START_REF] Kamm | Principles of biorefi neries[END_REF] Second-generation biorefi neries are mainly installed in the USA, China, and Canada. Nevertheless, there is a growing interest from Northern Europe countries. Microalgae biorefi neries are presently at a research and development stage. Nevertheless, some third-generation biorefi neries based on the use of waste (animal, food, and urban wastes) already exist in Europe. Another potential advantage of the development of biorefi neries is the availability of local raw materials. Th is point could be essential to avoid environmental impacts caused by transportation, and could stabilize the rural economy, which will be a major step toward sustainability. [START_REF] Van Dyne | A strategy for returning agriculture and rural America to long-term full employment using biomass refi neries[END_REF][START_REF] Clark | Green chemistry and the biorefi nery: a partnership for a sustainable future[END_REF] Moreover, the choice of raw materials to use is crucial, because it involves the choice of fi nal developed products. Indeed, biomass types can have strong composition diff erences, and in this way lead to create diff erent products. [START_REF] Cherubini | The biorefi nery concept: Using biomass instead of oil for producing energy and chemicals[END_REF] Figure 2 off ers a representation of the paramount potential of fi nal products which can be developed in a biorefi nery. [START_REF] Werpy | Top value added chemicals from biomass. Volume 1-Results of screening for potential candidates from sugars and synthesis gas[END_REF][START_REF] Kamm | Biorefi neries -Multi Product Processes[END_REF] To execute the transformation of the biomass, following diff erent steps, biorefi neries are constituted of physical, chemical, biological, and thermal processes. [START_REF] Ghatak | Biorefi neries from the perspective of sustainability: Feedstocks, products, and processes[END_REF][START_REF] Parajuli | Biorefi ning in the prevailing energy and materials crisis: a review of sustainable pathways for biorefi nery value chains and sustainability assessment methodologies[END_REF][START_REF] Kamm | Biorefi neries -Multi Product Processes[END_REF][START_REF] Abels | Membrane processes in biorefi nery applications[END_REF][START_REF] Da | Cradle-to-grave' assessment of existing lignocellulose pretreatment technologies[END_REF][START_REF] Sun | Hydrolysis of lignocellulosic materials for ethanol production: a review[END_REF] Th is wide variety of production processes is a necessity to transform biomass feedstock mixes, because the composition of these renewable resources can strongly vary from one sort to another. [START_REF]Biofuels: Alternative Feedstocks and Conversion Processes[END_REF] Literature largely describes the biorefi nery production processes. For instance, a detailed list of the diff erent separation processes which can be found in a biorefi nery has been developed by Huang et al. [START_REF] Huang | A review of separation technologies in current and future biorefi neries[END_REF] Moreover, biorefi ning involves an optimization of production processes, in order to make the most effi cient use of feedstocks and to maximize the economic situation of the facility. [START_REF] Kamm | Biorefi neries -Industrial Processes and Products[END_REF]

Life Cycle Assessment (LCA) methodology

LCA, as defi ned by the Society of Environmental Toxicology and Chemistry (SETAC), is 'a process to evaluate the environmental burdens associated with a product, process, or activity by identifying and quantifying energy and materials used and wastes released to the environment; to assess the impact of those energy and material uses and releases to the environment; and to identify and evaluate opportunities to eff ect environmental improvements'. [START_REF] Fava | A technical framework for life-cycle assessments[END_REF][START_REF] Consoli | Guidelines for Life-Cycle Assessment: A Code of Practice[END_REF] A detailed report of the chronological evolution of LCA since its beginning in the 1970s, and the future challenges have been performed by Guinée et al. [START_REF] Guinee | Life cycle assessment: past, present, and future †[END_REF] Initially, LAC was only practiced on products, but the methodology can also be applied to a process or a service, and to all sectors such as the automotive industry, agriculture, chemical industry, construction, etc. LCA of industrial processes can be used to choose the best solution during the design stage. [START_REF] Scipioni | LCA to choose among alternative design solutions: The case study of a new Italian incineration line[END_REF][START_REF] Burgess | Application of life cycle assessment to chemical processes[END_REF] Th e LCA methodological framework, normalized by two international standards (ISO 14040 and ISO 14044), [START_REF]ISO I, 14040: Environmental management-life cycle assessment-principles and framework[END_REF][START_REF]Environmental Management, Life Cycle Assessment, Requirements and Guidelines[END_REF] proposes to achieve LCA by completing four diff erent steps:

• Goal and scope defi nition: Th is step defi nes the objectives and the fi eld of the study, the function of the system, the functional unit, and the limits of the system. • Inventory analysis: Th is phase collects and quantifi es all inputs of the studied system (renewable and non-renewable raw materials and energy) and outputs (emissions in air, water, and soil) on the whole product life cycle. Several methods to perform the life cycle inventory compilation can be found in the literature. [START_REF] Suh | Methods for Life Cycle Inventory of a product[END_REF] • Impact assessment: Th is stage groups inputs and outputs to determine their relative contribution to envi-ronmental burdens and damages. Th is step is certainly the most complex, and a wide variety of impact assessment methods have been developed: ILCD 2011, [START_REF]International Reference Life Cycle Data System (ILCD) Handbook -General guide for Life Cycle Assessment -Detailed guidance[END_REF] IMPACT 2002+, [START_REF] Jolliet | IMPACT 2002+: A new life cycle impact assessment methodology[END_REF] ReCiPe 2008, [START_REF] Goedkoop | Life Cycle Impact Assess Method Which Comprises Harmon Categ Indic Midpoint Endpoint Level[END_REF] etc. Th e impact assessment can be realized at midpoint or endpoint levels. [START_REF] Hauschild | Identifying best existing practice for characterization modeling in life cycle impact assessment[END_REF] • Interpretation: Practitioners can identify improvement opportunities for the studied system. Moreover, a sensitivity analysis can be performed on the results of the LCA to identify the parameters or variables that have the strongest infl uence on environmental impacts. Knowledge of highly sensitive data or settings will guide the search for technical solutions to reduce environmental loads of the studied product. [START_REF] Groen | Sensitivity analysis in life cycle assessment[END_REF] Nowadays, the LCA community constantly expands, and there is a crucial need to work with robust methods and tools. With this objective, international or European working groups are more and more developed, such as the International Reference Life Cycle Data System (ILCD) which publish series of handbooks, [START_REF]International Reference Life Cycle Data System (ILCD) Handbook -General guide for Life Cycle Assessment -Detailed guidance[END_REF] or the European Life Cycle Database, a completely free database to generalize and grant a large access to LCA. Finnveden et al. [START_REF] Finnveden | Recent developments in Life Cycle Assessment[END_REF] proposed a synthesis of crucial developments in LCA, such as database development, methods enhancement, etc.

Interests of performing LCA on biorefi nery processes

Th e will of biorefi nery industrials to use biomass feedstock to practice an environmentally friendly manufacturing system is laudable, and a decisive step for the future. Nevertheless, producing more sustainable outputs can be complex and replacing fossils by renewable and green resources is not suffi cient to enable the transition to a clean and sustainable industry. Indeed, a particular attention is crucial on several points such as the choice of biomass feedstock or transformation processes. [START_REF] Ghatak | Biorefi neries from the perspective of sustainability: Feedstocks, products, and processes[END_REF] As a matter of fact, creating a product from biomass could require more energy or reagents than the fossil-based equivalent. [START_REF] Clancy | Changing from petroleum to wood-based materials: critical review of how product sustainability characteristics can be assessed and compared[END_REF] Th e importance of incorporating environmental considerations to Process System Engineering (PSE) fi eld, traditionally focused on economic and technical constraints, is emphasized in perspective works since the beginning of the twenty-fi rst century, [START_REF] Grossmann | Research challenges in process systems engineering[END_REF][START_REF] Harold | Process engineering in the evolving chemical industry[END_REF][START_REF] Allen | Green engineering: environmentally conscious design of chemical processes and products[END_REF] and some environmental or socials burdens are systematically assessed during the design phases of a process. For instance, health and safety issues and the control of emissions from the plant are generally taken into account. [START_REF] Azapagic | A methodology for integrating sustainability considerations into process design[END_REF] Nevertheless, plenty of crucial impacts are still neglected (acidifi cation, eutrophication, etc.). Environment problematic is currently considered as a non-priority and their improvements are considered when the process is operating.

However, to avoid potential pollution transfers from a life cycle phase to another, a life cycle approach is essential to assess the production processes. Using the LCA method appears like the most promising method, because it permits to consider the life cycle of the process itself, closely linked to the product life cycle, as illustrated in Fig. 3. Indeed, the life cycle of a process starts with research and development stage, followed by design and construction steps. Th e operational phase comes aft er. Th is is generally the most understood and assessed step. Finally, the endof-life of a process is generally composed of disassembly, decommission, and restoration steps. [START_REF] Allen | Green engineering: environmentally conscious design of chemical processes and products[END_REF][START_REF] Chevalier | Environmental assessment of fl ue gas cleaning processes of municipal solid waste incinerators by means of the life cycle assessment approach[END_REF][START_REF] Jacquemin | Life cycle assessment (LCA) applied to the process industry: a review[END_REF] Consequently, performing an environmental LCA leads to an expansion of the boundaries of the assessed system, by taking into account upstream and downstream processes [START_REF] Bakshi | The quest for sustainability: Challenges for process systems engineering[END_REF][START_REF] Kumar | Impact of pretreatment and downstream processing technologies on economics and energy in cellulosic ethanol production[END_REF] and not only consider the operational phase.

LCA of biorefi neries: literature review of existing practices

Commonly, process design only considers technical and economic criteria in most sectors, to guarantee the feasibility of a product and to maximize profi t. Th ese considerations are essential for biorefi neries, too. However, environmental criteria, assessed by environmental LCA are crucial and need to be integrated to the design of modern plants [START_REF] Azapagic | Process design for sustainability: the case of vinyl chloride monomer[END_REF] and particularly of biorefi neries. A signifi cant number of LCAs applied to biorefi ning facilities can be found in the literature. In this paper, these studies are separated into two main groups: LCA of biorefi nery inputs (raw materials) and products and LCA of biorefi nery processes. Th e fi rst group of studies generally takes into account the impacts on the environment of plant activities, but they are considered as a unique operation, without distinguishing and separating the diff erent processes parts encountered in the biorefi nery (pre-treatments, extractions, separations, purifi cations, and others). Th e second group focus on studies which off er a higher detail level, and permit to have a better understanding of the operational phases.

Environmental LCA for biomass feedstock choice

Even more than for other industrial sectors, the inclusion of upstream activities is essential for biorefi neries. Indeed, transformation processes used in the plant can operate with a large amount of diff erent biomass feedstocks. Consequently, the choice of raw materials is a crucial step in the environmental analysis of a biorefi nery. In this way, a large part of environmental LCAs of biorefi neries are focused on diff erences on environmental impacts induced by the choice of the biomass feedstock. For instance, Jeswani et al. 55 drive a comparative LCA of lignocellulosic biorefi neries which produce bioethanol using four diff erent inputs: wheat straw, poplar, Miscanthus, and forest residue. Th is study also compare these scenarios to ethanol production from fossil resources. As expected, they highlighted important reductions on eight environmental impacts among 12 assessed by using biomasses instead of fossil resources. Moreover, signifi cant variations exist Figure 3. Links between product and process life cycles, from Jacquemin et al. [START_REF] Jacquemin | Life cycle assessment (LCA) applied to the process industry: a review[END_REF] .

between renewable feedstocks too. Indeed, ethanol from forest residue appears like the most promising option, and ethanol from wheat straw as the worst, mainly due to the important burdens generated by land use change. Undeniably, land use change eff ects are a crucial point. [START_REF] Cherubini | LCA of a biorefi nery concept producing bioethanol, bioenergy, and chemicals from switchgrass[END_REF] Th e paper clearly explains that each option off ers reduced environmental impacts concerning greenhouse gas (GHG) emissions compared to fossil resources. Nevertheless, the paper puts in evidence that forest conversion to Miscanthus cultures leads to a raise of GHG emissions, because the sequestration potential of Miscanthus is less important than forests sequestration potential. In contrast, the conversion of grassland to poplar growth drives to additional GHG savings. Cherubini et al. [START_REF] Cherubini | LCA of a biorefi nery concept producing bioethanol, bioenergy, and chemicals from switchgrass[END_REF] also achieved an assessment of a biorefi nery based on switchgrass to produce ethanol, energy, and chemicals. Th is LCA compares results to a fossil reference system. In this case, too, a biorefi nery facility off ers better performance than the classic refi nery, with gains on GHG emissions notably. Nevertheless, two impacts are superior in the biorefi nery scenario: acidifi cation and eutrophication. In the same way, Mu et al. [START_REF] Mu | Comparative life cycle assessment of lignocellulosic ethanol production: biochemical versus thermochemical conversion[END_REF] compared the environmental impacts in these cases, for diff erent raw materials (wood chips, corn stover, waste paper, and wheat straw). Nevertheless, the assessment is focused on only three impacts: GHG emissions, water consumption and energy use, which are generally the main issues for industry. Several studies highlight the potential environmental benefi ts of second generation biofuels compared to fi rst generation biofuels. For instance, Mu et al. [START_REF] Lim | Parallel production of biodiesel and bioethanol in palm-oil-based biorefi neries: life cycle assessment on the energy and greenhouse gases emissions[END_REF] assessed the environmental burdens (energy consumption and GHG emissions) of a palmoil-based biorefi nery. Th ird-generation biorefi neries, based on the use of algal biomass, are still not very developed. However, they have a strong potential, because the cultivation of this biomass could bring to a more effi cient way to capture CO 2 emissions. Cherubini et al. [START_REF] Cherubini | Greenhouse gas (GHG) and energy analysis of a bioethanol oriented biorefi nery based on wood[END_REF] performed an LCA of a bioethanol biorefi nery based on wood, but considered only GHG emissions and energy consumption. Nonetheless, this paper shows the potential of biorefi neries. Indeed, this system could reduce GHG emissions by 40% and non-renewable energy savings by 84% in 2050. In addition, Uihlein and Schebek 60 performed comparative LCAs between variants of lignocellulosic biorefi neries and a fossil refi nery. Th is study exposes the signifi cant advantages of a biorefi nery compared to a classic way: a reduction of 40% of total environmental impacts for the production of lignin, ethanol and xylite instead of acrylic binder, gasoline, and sugar.

Consequently, the review of these papers highlights the importance of assessing and comparing feedstocks by LCA. Indeed, this approach permits identifi cation of the potential benefi ts of using biomass instead of fossil resources. Nevertheless, it also puts in evidence the strong disparity between the diff erent types of biomasses, some of whose cultures can lead to additional environmental burdens (eutrophication and acidifi cation for fi rst-generation biomass feedstocks cultures notably). However, a focus on biomass feedstock is not enough. Indeed, Singh et al. [START_REF] Singh | A critical review of biochemical conversion, sustainability and life cycle assessment of algal biofuels[END_REF] proposed a review of LCA of algal biofuels. Th is study puts in evidence the importance of understanding and assessing the process operations too. Indeed, some key issues such as the necessity of recycling the water used for harvests, or the signifi cant energy consumption of several unit operations such as drying and hexane extraction are identifi ed.

Comparative LCA of alternative processing routes

Another part of LCA of biorefi neries explore alternative processing routes. For example, Jeswani et al. 55 experimented with the comparison between thermochemical and biochemical conversions of biomass to ethanol. Th is assessment points the advantages of using a thermochemical route instead of a biochemical process to produce ethanol from poplar and forest residue. Th e comparison between these two alternative processing routes can be found in other publications, such as Mu et al. [START_REF] Mu | Comparative life cycle assessment of lignocellulosic ethanol production: biochemical versus thermochemical conversion[END_REF] Moreover, Cherubini et al. [START_REF] Cherubini | Crop residues as raw materials for biorefi nery systems -An LCA case study[END_REF] practiced an evaluation of corn stover and wheat straw conversion by thermochemical and biochemical treatments. Furthermore, Gilani et al. [START_REF] Gilani | Life cycle assessment of an integrated forest biorefi nery: hot water extraction process case study[END_REF] practiced a consequential LCA of fi ve diff erent processing routes for the extraction of hemicelluloses, and Kenthorai Raman et al. [START_REF] Raman | Life cycle assessment of biodiesel production using alkali, soluble and immobilized enzyme catalyst processes[END_REF] assessed three diff erent catalytic processes for biodiesel production. In both cases, diff erent scenarios were modeled, as classic LCA, and then compared to identify the best solution.

Uihlein et al. [START_REF] Uihlein | Environmental impacts of a lignocellulose feedstock biorefi nery system: An assessment[END_REF] experimented with a diff erent way to assess the environmental performance of a biorefi nery, in an eco-design and optimization objective. Indeed, they assessed six diff erent scenarios which represent possible variants for the processing route of the future biorefi nery. Th ese alternatives consider the possibility of adding acid or heat recoveries, or using lignin to provide heat or electricity. Th ese assessments reveal the main hotspots, i.e., the most contributing activities to environmental impacts. So, three processes generate the major part of environmental impacts: provision of straw (80% on carcinogenics, 88% on land occupation), acid (65% on total impact score), and heat (20% of total climate change). Furthermore, compari-son between the diff erent scenarios highlight the potential gains. Finally, this LCA also underlines potential improvements thanks to the establishment of recovery systems for acid and heat: with respective recovery rates of 95% and 80%, an additional reduction of the impacts appears, from 30% to 90% depending on assessed categories compared to the base case biorefi nery. In the same way, Jacquemin et al. [START_REF] Jacquemin | Evaluation of the technical and environmental performances of extraction and purifi cation processes of arabinoxylans from wheat straw and bran[END_REF] assessed the environmental impacts of a part of a biorefi ning process. Indeed, they determined water consumption and carbon dioxide emissions generated by the ultrafi ltration step of an extraction and purifi cation process of arabinoxylans. Th is study highlighted the paramount contribution of operating conditions to environmental impacts. Modahl et al. [START_REF] Modahl | Environmental assessment of chemical products from a Norwegian biorefi nery[END_REF] accomplished an LCA of a timber and woodchips based biorefi nery, which produce six diff erent products. Th ey avoided the allocation procedure by modeling processes at a detailed level. Consequently, they could identify the most contributive processing steps. Borrion et al. [START_REF] Borrion | Environmental life cycle assessment of lignocellulosic conversion to ethanol: A review[END_REF] reviewed the diff erent environmental LCAs of bioethanol from lignocellulosic biorefi neries. Finally, Brentner et al. [START_REF] Brentner | Combinatorial life cycle assessment to inform process design of industrial production of algal biodiesel[END_REF] carried out one of the most complete LCAs applied to biomass conversion processes. Indeed, the aim was to identify the most encouraging pathways to implement an environmentally responsible plant destined to produce biodiesel from algal biomass. For this purpose, the biorefi ning system is separated into fi ve processing stages: cultivation, harvesting, lipid extraction, conversion, and disposal or reuse. Moreover, diff erent technologies are considered for each step. Consequently, there are 160 diff erent combinations, i.e., possible paths. Th is cradle-to-gate study aims to identify the best design option. To simulate the plant, models are used, such as algae growth parameters, bioreactor design, harvesting, extraction and end-of-life of residue. Th e best promising global route is determined by assembling each unit process consuming less energy, by a single objective optimization. In a second time, a comparative LCA between the currently practiced scenario and the optimized route is achieved. Results put in evidence a global improvement of the environmental performance thanks to the establishment of the less energy consuming alternative. Indeed, the second scenario induces a reduction of 86% of greenhouse gases emissions. Moreover, water use is reduced by 48%, and land area requisitioned by 58%.

To conclude, in most cases, production processes are not modeled in LCAs. Th ey are considered as black boxes, i.e., a global and irremovable operation. Generally, there is a unique operation, named 'biorefi nery plant', [START_REF] Cherubini | LCA of a biorefi nery concept producing bioethanol, bioenergy, and chemicals from switchgrass[END_REF] which groups all engaged processes, such as pre-treatment, hydrolysis, fermentation, combustion, etc. Nevertheless, their complexity is well above it. Plant operations are a succession of unit operations (UO), which all have inputs and outputs. All these blocks are linked, and operate with synergy: a change on a unit operation will involve changes on the linked unit operations. [START_REF] Allen | Green engineering: environmentally conscious design of chemical processes and products[END_REF] Currently, scientifi c publications related to environmental LCAs does not completely highlight the specifi c contribution of each unit operation to environmental damages, despite the fact that it may lead to better optimizations of process chains. [START_REF] Igos | Life Cycle Assessment of water treatment: what is the contribution of infrastructure and operation at unit process level?[END_REF] Th is practice begins to emerge on some application fi elds: water treatment, chemical industry [START_REF] Azapagic | Life cycle assessment as a tool for improving process performance: a case study on boron products[END_REF][START_REF] Koroneos | Life cycle assessment of hydrogen fuel production processes[END_REF] or metallurgy [START_REF] Norgate | Assessing the environmental impact of metal production processes[END_REF] for instance. Jacquemin et al. [START_REF] Jacquemin | Life cycle assessment (LCA) applied to the process industry: a review[END_REF] proposed a review of LCA applied to processes in various sectors; nevertheless it is still not applied to biorefi neries.

Coupling LCA to process simulation tools

In this way, a preliminary LCA achieved at the fi rst design steps could permit identifi cation of the main potential hotspots, and then to have a particular attention to these critical points. [START_REF] Gasafi | Using life-cycle assessment in process design[END_REF] Moreover, the sustainability of a biorefi ning facility is actively related to an effi cient use of raw materials and to an optimal mix and arrangement of processes. A biorefi ning process sequence can be considered as a complex organization of physical, chemical, biochemical, or thermochemical processes. In this way, it is essential to identify the most promising alternative. [START_REF] Ghatak | Biorefi neries from the perspective of sustainability: Feedstocks, products, and processes[END_REF] Th is challenge can be performed by coupling LCA to process simulation tools like ProSimPlus®, Aspen®, Chemcad®, or SuperPro® for instance. Indeed, simulating the complete sequence of a process could allow a more detailed comprehension of industrial activities of a product life cycle. Undeniably, this innovative approach off ers the opportunity to understand the impact on the environment of a process, at the scale of unit operations, and to assess the contribution of operating conditions on environmental burdens. Indeed, two variables are generally the most infl uent on the economic, technical and environmental performances of a process: structure and operating variables. [START_REF] Sun | A multi-objective process optimization procedure under uncertainty for sustainable process design[END_REF] Coupling process fl ow-sheeting and LCA is an emerging practice. Th e aim is to simulate a process sequence to obtain mass and energy balances, which can aft er be used as data for the life cycle inventory step. [START_REF] Azapagic | The application of life cycle assessment to process optimisation[END_REF] It could be useful to avoid the recurrent issue of collecting complete and reliable data, for LCA realization. Azapagic et al. [START_REF] Azapagic | A methodology for integrating sustainability considerations into process design[END_REF] proposed a methodological framework based on these principles. Indeed, they detailed guidelines to realize Process Design for Sustainability (PDfS). Th e fi rst step is the project launch. During this step, it is crucial to identify all the assessed criteria, the possible alternatives, and the main stakeholders. Th en, the preliminary design phase can start. Process simulation is accomplished, to obtain mass and energy balances. Th en an LCA is practiced. In parallel, an economic evaluation is realized to evaluate the feasibility of the alternative. Finally, a detailed design step can be performed, with a full assessment of sustainability. Azapagic et al. [START_REF] Azapagic | Process design for sustainability: the case of vinyl chloride monomer[END_REF] practiced this methodological framework to a vinyl chloride monomer plant. Chemical industry had a pioneering role in the development of this methodology, probably encouraged by high stakes and reliable process simulation soft ware. Indeed, Alexander et al. [START_REF] Alexander | Process synthesis and optimisation tools for environmental design: methodology and structure[END_REF] applied this new methodology to a nitric acid plant. Th ey used Hysys® tool to model the facility, and to obtain mass and energy balance information. Th en, an LCA and an economic analysis (based on capital and operating costs) are performed. A multi-objective optimization determines the most promising options and eventual trade-off s. Guillén et al. [START_REF] Guillén-Gosálbez | Application of life cycle assessment to the structural optimization of process fl owsheets[END_REF] assessed the hydrodealkylation (HDA) of toluene process, with the aim of minimizing costs and environmental impacts. Th is same process has also been optimized by Ouattara et al. [START_REF] Ouattara | Economic and environmental strategies for process design[END_REF][START_REF] Ouattara | Economic and environmental impacts of the energy source for the utility production system in the HDA process[END_REF] with the minimization of costs and of fi ve environmental burdens. Furthermore, Fermeglia et al. [START_REF] Fermeglia | Computer aided design for sustainable industrial processes: Specifi c tools and applications[END_REF] developed a similar method by using PROII® or Aspen® and applied it to chemical industry (maleic anhydride production process). A similar approach has been practiced on milk concentration processes. [START_REF] Madoumier | Process simulation and life cycle analysis in the dairy industry-application to milk concentration[END_REF] Finally, Mery et al. [START_REF] Mery | An integrated "process modelling-life cycle assessment" tool for the assessment and design of water treatment processes[END_REF] experiment the link between process simulation soft ware and LCA to water-treatment processes. Th is assessment underlines the infl uence of unit operations and of operation conditions changes. A global tool has been developed by using Python programming language and the LCA soft ware Umberto® as a basis.

Th e link between Process System Engineering and environmental LCA is increasingly practiced in the chemical sector, as explained by Jacquemin et al. [START_REF] Jacquemin | Life cycle assessment (LCA) applied to the process industry: a review[END_REF] which compared 18 major research works on this fi eld. Th is approach also emerges in the biorefi ning area, but its application is more complex, due to diffi culties encountered to characterize solid biomass in soft ware developed for chemistry. Wang et al. [START_REF] Wang | Sustainable design and synthesis of hydrocarbon biorefi nery via gasifi cation pathway: Integrated life cycle assessment and technoeconomic analysis with multiobjective superstructure optimization[END_REF] experimented the search of an optimal and sustainable design of a biorefi nery based on a gasifi cation pathway. For this study, they performed a multi-objective optimization. Th e objectives are based on two aspects of sustainable development: economy and environment. Indeed, the aim of this application is to determine the optimal confi guration to minimize the environmental impact and to maximize the economic viability of the company. Th e economic objective is represented by the net present value (NPV), and the environmental goal by the minimization of global warming potential (GWP). To perform this work, Wang et al. [START_REF] Wang | Sustainable design and synthesis of hydrocarbon biorefi nery via gasifi cation pathway: Integrated life cycle assessment and technoeconomic analysis with multiobjective superstructure optimization[END_REF] created a superstructure which includes a wide range of models for several alternative functional blocks, for each step of the global process. GWP is calculated by a gate-to-gate LCA. Th e multi-objective optimization allows the evaluation of the best technologies for each unit operation, the most advantageous operating conditions, all the ideal fl ow rates, and the equipment sizes to maximize NPV and to minimize GWP. Jeswani et al. 55 practiced a comparative LCA of conceptual designs of a biorefi nery producing bioethanol. To accomplish this study, they implemented gasifi cation models developed by the NREL in Aspen Plus®. Th ey modeled four diff erent biorefi neries, depending on the dedicated feedstocks: wheat straw, forest residue, poplar, and Miscanthus. Th e comparison of the environmental profi les of the four biorefi ning options put in evidence the high potential of the ethanol production by thermochemical route applied to poplar and forest residue. Mayumi et al. [START_REF] Mayumi | Life cycle assessment of biomass-derived resin for sustainable chemical industry[END_REF] realized the assessment of a plant producing biomass-derived resins. Th ey used Aspen Hysys® to simulate the process operations, and then realized an LCA-based on mass and energy [START_REF] Azapagic | Life cycle assessment and its application to process selection, design and optimisation[END_REF] balances obtained before. A similar approach have been used by Morales Mendoza et al. [START_REF] Mendoza | Biodiesel Production from waste vegetable oils: combining process modelling, multiobjective optimization and life cycle assessment (LCA)[END_REF] to realize the eco-design of a bioethanol production facility, reusing waste vegetables. Indeed, this paper highlights the high interest of coupling LCA to a process simulation process. Morales Mendoza et al. [START_REF] Mendoza | Biodiesel Production from waste vegetable oils: combining process modelling, multiobjective optimization and life cycle assessment (LCA)[END_REF] used AspenHysys® and Ariane® to respectively simulate the biodiesel production process and the energy plant. So, the life cycle inventory is based on mass and energy balances obtained from the process simulation. Moreover, a cost estimation is realized, and a multi-objective optimization puts in evidence the optimal confi gurations to minimize the environmental damages (on human health, ecosystem quality, climate change and resources depletion) and to maximize profi t. Gerber et al. [START_REF] Gerber | A systematic methodology for the synthesis of unit process chains using Life Cycle Assessment and Industrial Ecology Principles[END_REF][START_REF] Gerber | A systematic methodology for the environomic design and synthesis of energy systems combining process integration, Life Cycle Assessment and industrial ecology[END_REF] also worked on the development of a superstructure to assess and improve production processes with a multi-objective optimization (minimization of global warming potential and production costs) applied to energy systems and to a Synthetic Natural Gas biorefi nery. [START_REF] Gerber | Proceedings of the 23rd International 55. Jeswani HK, Falano T and Azapagic A, Life cycle environmental sustainability of lignocellulosic ethanol produced in integrated thermo-chemical biorefi neries[END_REF][START_REF] Gerber | Integration of LCA in a thermo-economic model for multi-objective process optimization of SNG production from woody biomass[END_REF][START_REF] Gerber | Systematic integration of LCA in process systems design: Application to combined fuel and electricity production from lignocellulosic biomass[END_REF] Alvarado-Morales et al. [START_REF] Alvarado-Morales | Computer aided tools for sustainable design and analysis of bioethanol production[END_REF] worked on the LCA of a bioethanol biorefi nery, simulated on PROII®. So, a base case design is assessed fi rst, followed by alternative designs. Finally, Pereira et al. [START_REF] Pereira | Life cycle assessment of butanol production in sugarcane biorefi neries in Brazil[END_REF] assessed a sugarcane biorefi nery processes by using a process simulators to obtain mass and energy balances.

To conclude, coupling LCA and process simulation software to feed the life cycle inventory and to optimize the processing route (with the choice of unit operations and operating conditions) is an emerging and very promising method to enhance the environmental profi le of industries. Increasingly practiced in the chemical sector, this approach is increasingly used for the establishment of biorefi ning plants. A further step seems to be the integration of the other pillars of sustainable development: social and economic considerations. Table 1 summarizes these studies.

Th is section highlighted the impacts of raw materials and processing routes on the environmental performance of a biorefi nery. If the comparison of several biomass feedstocks is commonly performed, the high-detailed assessment of processing routes is a less-studied research topic. Commonly, the assessments of processes are performed on already in use production systems, based on plant data. Th is approach only allows the improvement and redesign of existing technologies. Moreover, the section put in evidence that realizing an LCA based on results of process simulation can be a powerful tool to propose an innovative solution before the process construction, and to really work on the eco-design of a process. So, it is crucial to assess environmental impacts since the beginning of a project, with technical constraints jointly, in an integrated path. [START_REF] Azapagic | Life cycle assessment and its application to process selection, design and optimisation[END_REF][START_REF] Azapagic | Sustainable development in practice[END_REF] Th e assessment of environmental performance at each design stage would unable a better optimization of the process. [START_REF] Allen | Green engineering: environmentally conscious design of chemical processes and products[END_REF] A new methodology to integrate sustainability considerations to the biorefi nery process eco-design Th e previous section put in evidence some strong improvements in process system engineering and LCA fi elds. Nevertheless, it also highlighted some lacks, to achieve sustainable assessments and sustainable design of biorefi nery processes. Th e objective of this section is to propose a new methodology to facilitate the eco-design and sustainable development of biorefi nery processes, dealing with possible diffi culties by assessing simultaneously the three dimensions of sustainability.

Application of multi-objective optimizations to biorefi neries

Nowadays, designing more sustainable processes is one of the key challenges for the development of a more environmentally friendly industry. Nevertheless, this aim can only be reached with a synergetic integration of social, economic, and environmental criteria, through a life cycle perspective. Th is vision should be applied to biorefi neries, because this type of industry which off er greener fuels and chemicals [START_REF] Azapagic | Sustainability considerations for integrated biorefi neries[END_REF] seems to be the most promising option to transit to this more sustainable society. [START_REF] Steffens | Multicriteria process synthesis for generating sustainable and economic bioprocesses[END_REF] Nevertheless, the optimization of a system on multiple objectives is complex, because criteria are generally antagonist. Moreover, categories have to be optimized in the same time, and not one aft er the other.

Historically, multi-objective optimization has been experimented by process system engineering practitioners in order to reduce wastes, [START_REF] Young | Designing sustainable processes with simulation: the waste reduction (WAR) algorithm[END_REF][START_REF] Young | The waste reduction (WAR) algorithm: environmental impacts, energy consumption, and engineering economics[END_REF] energy use and costs. Next, additional constraints, like technical and operability issues have been implemented. Finally, the adding of environmental impacts followed, with mitigate results. Indeed, one of the main challenges was to apply a life cycle approach to the environmental analysis, even if upstream and downstream activities cannot be governed by plant operators. [START_REF] Alexander | Process synthesis and optimisation tools for environmental design: methodology and structure[END_REF] Currently, the main challenge is to develop a tool which will be a help for the choice of the best processing route. Indeed, arbitrating and choosing between diff erent scenarios can be complex. Moreover, another crucial point is to perform a multi-objective optimization of environmental, economic, technical, and social considerations TETP, terrestrial ecotoxicity potential of a process. Some optimizations of one or two of these criteria already exist, and especially for biorefi ning activities. Economic and environmental optimizations are realized, such as the example of design of VCM plant, [START_REF] Khan | GreenPro: a new methodology for cleaner and greener process design[END_REF] or for absorption cooling systems. [START_REF] Gebreslassie | Design of environmentally conscious absorption cooling systems via multi-objective optimization and life cycle assessment[END_REF] Th ese assessments highlight the diffi culty to perform a complete evaluation of the sustainability of a process. Indeed, only a few studies consider the three pillars of sustainable development. Besides, these dimensions have to be evaluated with a life cycle approach.

A new methodological framework for the integrated assessment of the sustainability

Figure 5 exposes a global representation of the new methodology proposed for the sustainability optimization and design of biorefi nery processes. Th is schema highlights the importance of defi ning the most suitable parameters for each UO, which will lead to important changes on the three areas of sustainability. Th e following part describes each step of the new methodological framework in detail.

First of all, to assess the complete sustainability of processes, it is essential to determine which indicators will permit to attribute a score, a mark to the various scenarios. Th e best option to assess the sustainability aspects is to use life cycle oriented methods: Environmental Life Cycle Assessment, Life Cycle Costing (LCC), [START_REF] Parajuli | Biorefi ning in the prevailing energy and materials crisis: a review of sustainable pathways for biorefi nery value chains and sustainability assessment methodologies[END_REF][110][111][112] and Social Life Cycle Assessment. 104,113 A large choice of indicators to achieve these assessments is available. 114,115 For example, economic evaluation can be based on feedstocks and products costs, on capital costs or on return on investment. Internal costs such as budget for research and development or company costs can also be used as indicators. [START_REF] Clancy | Changing from petroleum to wood-based materials: critical review of how product sustainability characteristics can be assessed and compared[END_REF] Social assessment on the other hand can be assessed with metrics such as the number of jobs, health issues, land availability, gender equality, etc. [START_REF] Azapagic | Sustainability considerations for integrated biorefi neries[END_REF] Exactly like environmental LCA, social LCA, and LCC require large amount of data. Environmental LCA is fed by coupling with a process simulator, to obtain the required mass and energy balance. Generally, the data gathering is easily practicable for LCC. Nevertheless, Social LCA is an emerging methodology, still on development, and acquire information can be complex. Even if the interest of applying social LCA at the earlier design stages is obvious, this methodology is in reality oft en practiced at the end of the development, because more data are available. [START_REF] Clancy | Changing from petroleum to wood-based materials: critical review of how product sustainability characteristics can be assessed and compared[END_REF] So, environmental LCA, LCC, and social LCA appears like the most relevant methods. 116 An integrated methodology covering the three dimensions of sustainability can be initiated, similar to the LCSA. [START_REF] Clancy | Changing from petroleum to wood-based materials: critical review of how product sustainability characteristics can be assessed and compared[END_REF][117][118][119] Th e next step of the proposed methodology is the realization of a multi-objective optimization. Indeed, when the assessment of the three pillars of sustainable development has been achieved, it is necessary to identify a solution to optimize the process on these three categories (environment, economy, and social). Nevertheless, the choice of the best solution is complex due to the confl icting objectives. Th ereby, designing sustainable processes necessarily force engineers to make choices and agreements between the diff erent stakeholders, [START_REF] Allen | Green engineering: environmentally conscious design of chemical processes and products[END_REF] because optimizing many criteria simultaneously rarely brings to an ideal solution, which reaches maximum gains for each category. In most cases, these categories are antagonist. For instance, reduction of environmental impacts can involve a diminution of the maximal realizable profi t. Consequently, it is necessary to perform a multi-objective optimization [START_REF] Azapagic | Life cycle assessment and its application to process selection, design and optimisation[END_REF] to identify all the possible solutions to optimize simultaneously the three assessed dimensions (environment, economy, and social). So, the methodology consists of determining objectives functions for each criterion which needs to be optimized.

Th e optimization of such complex systems generally leads to an important number of practicable solutions, represented by Pareto frontiers or surfaces. [START_REF] Azapagic | The application of life cycle assessment to process optimisation[END_REF] Pareto fronts obtained for two-objective and three-objective optimizations are represented on Fig. 4.

Th e determination of these Pareto surface can be really complex, that is why a large part of studies which relate multi-objective optimization generally consider the environmental impacts as a single score, or with one burden, oft en climate change. Genetic algorithms can be used in order to reduce the optimizing time. 120,121 Another method is to identify indicators which vary with the same tendencies, and to fi nd independent variables. Indeed, Azapagic et al. [START_REF] Azapagic | The application of life cycle assessment to process optimisation[END_REF] optimized a boron product system, and discovered a link between diff erent impacts, such as GWP, acidifi cation and human toxicity. Consequently, the optimization can be realized with GWP only, and related impacts will decrease too.

Th e last part of the innovative methodology is the choice of a solution. For this step, it is crucial that stakeholders can understand and identify gains and losses for each solution. Indeed, it is important to understand that a multi-objective optimization permits to reach optima which are diff erent of the ones obtained with a single objective optimization. Consequently, environmental, economic, or social best scores determined separately will be unattainable by a multi-objective optimization. To facilitate the decision-making process and to permit to stakeholders to realize trade-off s, several tools can be used. A fi rst method consists in the attribution of diff erent weights to each criterion, depending on its importance [START_REF] Parajuli | Biorefi ning in the prevailing energy and materials crisis: a review of sustainable pathways for biorefi nery value chains and sustainability assessment methodologies[END_REF][START_REF] Alexander | Process synthesis and optimisation tools for environmental design: methodology and structure[END_REF] to calculate the best solution. Nevertheless, this method forces stakeholders to promote criteria. To avoid it, it is possible to assign the same weight to each criterion. Another solution is to choose the alternative for which all criteria diff er from their optimal values with the same percentage, as mentioned by Azapagic et al. for the assessment of the boron system. [START_REF] Azapagic | The application of life cycle assessment to process optimisation[END_REF] Decision-making can also be supported by the multi-attribute value theory method (MAVT) or by the analytical hierarchy process (AHP). 122 Wang et al. realized a review of decision-making methods. 123 To choose between the diff erent alternatives, it is essential for all the diff erent stakeholders to make trade-off s, and so to base the eco-design of the process on a global understanding of the system. [START_REF] Sun | A multi-objective process optimization procedure under uncertainty for sustainable process design[END_REF] Figure 5. Methodology for Sustainable LCA coupled to process simulation software.

Challenges and future trends

Th e implementation of this new methodology and its associated tools is subject to several barriers. Indeed, these limits can be classifi ed in several groups: barriers linked to the application of environmental LCA, limits related to biorefi ning processes simulation step, and concerns about the assessments of the other dimensions of sustainable development (social LCA and LCC). Finally, some refl ections are formulated as an opening to link this new methodological framework with other environmentally friendly methods, such as green chemistry.

Limits linked to environmental LCA

Choice of the functional unit and allocation issue

Nowadays, production processes can create a large range of products or energy simultaneously. One of the main issue with the LCA of multi-products processes is the choice of an adapted functional unit (FU), and by the way, the choice of an allocation method to determine the relative contribution of each fi nal product on the environmental burdens. 124 Assumptions are oft en decided, like considering one product as the main output, and all the others like co-products, wastes, or residues. However, biorefi neries produce high-value goods, such as chemical compounds, which cannot be considered as wastes. 125 To identify the most suitable FU, several methods can be tested. Cherubini et al. [START_REF] Cherubini | LCA of a biorefi nery concept producing bioethanol, bioenergy, and chemicals from switchgrass[END_REF] based their assessment on the amount of biomass treated per year (dry matter). A similar approach is used by Uihlein et al. [START_REF] Uihlein | Environmental impacts of a lignocellulose feedstock biorefi nery system: An assessment[END_REF] who base their works on the quantity of biomass entering the biorefi nery. Sometimes, assessments are realized by using various functional units. [START_REF] Parajuli | Biorefi ning in the prevailing energy and materials crisis: a review of sustainable pathways for biorefi nery value chains and sustainability assessment methodologies[END_REF] Th e choice of an FU is easier for biorefi neries producing energies exclusively. Indeed, the Renewable Energy Directive 125 bases every assessment on the same FU: 1 MJ of fuel. Nevertheless, this approach does not take into account the diff erent types of biofuels.

Moreover, the quality of the product is an important consideration and should be specifi ed in the functional unit. For instance, the production of a high purity cellulose at 95% will lead to diff erent operating conditions and so on diff erent environmental impacts than the production of 80% pure cellulose.

Th e choice of the allocation method is also a crucial step, because it will strongly impact the fi nal results of the LCA, [126][127][128][129] For instance, Luo et al. 130 compared LCA results obtained with diff erent allocation rules on a corn-stover-based biorefi nery. In this case, a mass and energy allocation shows a reduction of global warming potential compared to classic gasoline production. Nevertheless, the economic allocation suggests opposite conclusions. Th e international standards ISO 14040 and ISO 14044 [START_REF]ISO I, 14040: Environmental management-life cycle assessment-principles and framework[END_REF][START_REF]Environmental Management, Life Cycle Assessment, Requirements and Guidelines[END_REF] advise to avoid the allocation when it is possible. Th e best option is to increase the level of detail of the model, to separate a multifunctional process into several subprocesses. If this method is not practicable, an expansion of the system should be considered, by substitution or by enlargement. 131 To perform the LCA of a biorefi nery producing ethanol, Jeswani et al. 55 used the system expansion approach. If it is impossible, the allocation has to be based on physical properties of products (mass or energy typically), or on other links, such as an economic allocation for example. Nevertheless, an economic allocation is not fully reliable for the assessment of biorefi neries, because it is still an emerging sector, and raw materials and products prices could strongly vary. 132 Cherubini et al. [START_REF] Cherubini | Greenhouse gas (GHG) and energy analysis of a bioethanol oriented biorefi nery based on wood[END_REF] assessed bioethanol biorefi nery and proposed a comparison of results depending on the allocation procedure used. Brankatschk et al. 133 developed a new allocation method for LCA of agricultural activities. Indeed, they based this allocation procedure on the Cereal Unit, a common denominator from Germany used to compare diff erent agricultural products. Th is new method leads to intermediate results between mass/energy and economic allocations results. Ahlgren et al. 134 proposed a detailed paper on the allocation issues for biorefi neries. To conclude, defi ning a universal allocation method to apply is impossible. Th e allocation procedure has to be chosen and can be diff erent for each situation. 126

Assessment of the whole life cycle

Designing a sustainable biorefi nery process can be executed from three diff erent perspectives. First of all, the choice of the biomass feedstock is essential, to ensure a constant and enduring supply and to minimize the environmental impacts related to the upstream agricultural activities. Secondly, the process performances have to be enhanced, based on consumptions and emissions linked to the process chain. Finally, a complete assessment of fi nal products is compulsory, to determine its sustainability from environmental, economic, and social aspects. [START_REF] Parajuli | Biorefi ning in the prevailing energy and materials crisis: a review of sustainable pathways for biorefi nery value chains and sustainability assessment methodologies[END_REF] Consequently, a biorefi nery should be assessed with a cradle-to-grave approach, to take into account the complete life cycle, and not to neglect potentially primordial and signifi cant activities, such as transportation to and from the installation site, cultivation steps, and fi nal products end-of-life. [START_REF] Azapagic | Sustainability considerations for integrated biorefi neries[END_REF] Th e agricultural sector is one of the main contributors to climate change, via important GHG emissions. Consequently, it is compulsory to take these signifi cant impacts into account when assessing a plant linked to agricultural activities. A sustainable upstream agriculture must be organized, based on economic, environmental, and social considerations. 135 Nevertheless, a cradle-to-grave study is oft en diffi cult or even unrealizable, due to the wide range of fi nal products and usages. Consequently, data collection on the future of products at the output of the plant is complex. In this way, the cradleto-gate alternative is generally preferred to avoid this issue. For instance, Azapagic et al. [START_REF] Azapagic | Life cycle assessment as a tool for improving process performance: a case study on boron products[END_REF] realized a cradle-to-gate assessment of the system processing boron ores to make fi ve diff erent products, to identify the key unit processes and improvement possibilities.

In the literature, cradle-to-grave assessments of pulp and paper industry can be found. 136 Th is kind of industry is very similar to biorefi neries. 137 Indeed, pulp and paper factories can be considered as basic biorefi neries, and a large part of current biorefi neries are in reality former paper production plants. [START_REF] Ghatak | Biorefi neries from the perspective of sustainability: Feedstocks, products, and processes[END_REF]138 Consequently, assessing a biorefi nery on the whole life cycle is possible, and could permit to identify hotspots outside of the plant gates. Indeed, signifi cant impacts are caused by transportation or by cultivation methods. Moreover, LCAs of upstream activities could be used as an argument to choose the most environmentally friendly biomass for future biorefi ning applications. 139 For instance, woodchips are considered as one of the most encouraging feedstocks. Nevertheless, this apparent sustainability is highly correlated to the cultivation stage. Indeed, wood can be produced by natural or artifi cial regeneration methods. Artifi cial regeneration uses fertilizers especially, and consequently generates more environmental burdens (in particular acidifi cation and eutrophication, caused by nitrogen and phosphorous emissions). Th ereby, the choice of woodchips as feedstock has to be argued, because it is not systematically the best opportunity. 140 Additionally, important divergences exist concerning the way to quantify biogenic carbon linked to crops, i.e. the carbon which is sequestrated during the plant growth. [141][142][143][144][145][146] To conclude, performing a cradle-tograve LCA is crucial to assess a biorefi nery, to avoid pollution transfers and to take into account the complexities linked to biomass feedstocks.

Attributional or consequential LCA

One of the main diffi culties in the LCAs of industrial processes is the choice of the LCA type. [START_REF] Parajuli | Biorefi ning in the prevailing energy and materials crisis: a review of sustainable pathways for biorefi nery value chains and sustainability assessment methodologies[END_REF] Indeed, an LCA can be attributional or consequential. [START_REF] Finnveden | Recent developments in Life Cycle Assessment[END_REF]147 An attributional LCA is based on physical fl ows which are constant through the whole life cycle, whereas consequential LCA illustrates the change of fl ows to and from the environment, resulting from diff erent potential decisions. 134,148 Th ese two types of LCA generate important diff erences in the fi nal results. 149 As biorefi ning is an emerging fi eld, a consequential LCA could be interesting to determine eff ects of the market on the future of biorefi neries. Nevertheless, a comparison with an attributional LCA, which is well-established and reliable, will be necessary to avoid aberrant results.

Land-use change issues

Th e section Limits link to process simulation highlighted the interest in assessing a biorefi nery on the whole life cycle, and not only with a gate-to-gate approach. Indeed, a cultivation step is essential for biorefi neries. Nevertheless, harvesting biomass feedstocks for industries may lead to additional impacts. A major issue is land-use changes. Indeed, the increasingly important demand for biomass in biorefi neries induces the development of feedstock cultivation for fi rst-generation biofuels mainly. However, this intensive farming causes several issues. First of all, land availability is not infi nite and the continuous growth of the biofuels plant fi eld imposes a partition of land and water between biorefi neries feedstocks and food sector. 55 Moreover, intensive agriculture could decrease the soil quality and then aff ect production yields on a long-term approach. Finally, land-use changes can lead to a significant increase in GHG emissions. Indeed, even if the carbon sequestration eff ect occurs (biogenic carbon captured by the crop during its growth), additional GHG emissions can be caused. For instance, Azapagic [START_REF] Azapagic | Sustainability considerations for integrated biorefi neries[END_REF] assessed the GHG emissions for diff erent feedstocks. Th ereby, a land conversion to harvest Miscanthus for ethanol production in the United Kingdom generates 3.6 times more GHG emissions than petroleum-based ethanol production. Moreover, the carbon sequestration in soils has to be assessed with a long-term vision. Indeed, C is captured into three diff erent spheres: soil, vegetation, and wastes. A land-use change disturbs this equilibrium, which needs 20 years to be re-formed. During the fi rst 20 years following a land-use change, there is an important gain on GHG emissions due to the CO 2 sequestration in soils. Nevertheless, aft er 20 years, the land attains an equilibrium and cannot capture CO 2 anymore. [START_REF] Cherubini | LCA of a biorefi nery concept producing bioethanol, bioenergy, and chemicals from switchgrass[END_REF] Moreover, some cultures generate a reduction of GHG emissions, like switchgrass, but others can induce a signifi cant increase of emissions.

To conclude, the development of second-generation biorefi neries is essential, because land-use change issues could be avoided by the replacement of dedicated crops by woody biomass and wastes from agriculture or forestry activities. Furthermore, the eff ects of land-use change should be assessed systematically, 134 with an appropriate indicator, like GHG benefi t per unit of land. [START_REF] Cherubini | LCA of a biorefi nery concept producing bioethanol, bioenergy, and chemicals from switchgrass[END_REF] Moreover, a major use of existing local renewable resources should be applied as oft en as possible. Indeed, this approach could permit minimization of the environmental burdens caused by raw materials transportation. 150 Th e benefi ts of local supply of biomass are well-known, especially for the pulp and paper industrial sector. 151

Other environmental impacts uncertainties

One of the major benefi ts of LCA is to avoid focusing on a unique impact (generally climate change), to assess a wide range of impacts simultaneously. Th is particularity applied to biorefi neries highlights the quasi-systematic increase of two environmental impacts: eutrophication and acidifi cation. [START_REF] Uihlein | Environmental impacts of a lignocellulose feedstock biorefi nery system: An assessment[END_REF] Fertilizers based on nitrogen and used for crop cultivation appear to be the main cause of this phenomenon. [START_REF] Cherubini | LCA of a biorefi nery concept producing bioethanol, bioenergy, and chemicals from switchgrass[END_REF] Another paramount damage caused by the installation of biorefi neries is a loss of biodiversity. Indeed, this phenomenon can appear, induced by land transformation and a standardization of harvested crops. Nevertheless, the opposite eff ect can also be detected, by transforming degraded lands into cultivated fi elds. Th is change could lead to an increase of biodiversity. [START_REF] Azapagic | Sustainability considerations for integrated biorefi neries[END_REF] To go further, the water demand can be a signifi cant and crucial issue when a biorefi nery is developed. Indeed, water consumption is strongly correlated to the nature of the harvested biomass. [START_REF] Azapagic | Sustainability considerations for integrated biorefi neries[END_REF] Consequently, special attention is required for this indicator. Moreover, a distinction should be made between water streams and water quality. Indeed, a comparison of the quality of input and output water of a process could be a powerful indicator. Finally, there are strong uncertainties concerning the N 2 O emissions mainly caused by using fertilizers. Indeed, the Intergovernmental Panel on Climate Change (IPPC) guidelines advise to consider that 1.325% of N from a fertilizer is emitted as N in N 2 O. However, recent works suggest the use of higher factors, between 3 and 5%. [START_REF] Cherubini | LCA of a biorefi nery concept producing bioethanol, bioenergy, and chemicals from switchgrass[END_REF]152 Considering the signifi cant impacts associated with synthetic fertilizers, such a paramount uncertainty is a major issue. To conclude, it is essential to keep the paramount advantage of the environmental LCA: the multicriteria assessment. Indeed, the major part of optimizations only focus on climate change and thereby decrease the interest of LCA.

Limits linked to process simulation

Modeling complexities

An important barrier to the development of LCA coupled to process simulation soft ware method is certainly complexity to represent: to modelize the biorefi nery processes. Indeed, these models are still complicated to fi nd in literature, but are more and more developed, [START_REF] Huang | A review of separation technologies in current and future biorefi neries[END_REF]105,[153][154][155][156][157] and it is not always possible to create each model before an assessment. Nevertheless, some wood biorefi neries were originally pulp and paper industries, and changed to increase revenue by producing bioenergy and biomaterials in addition to wood, pulp, and paper products. 158,159 In these cases, the original processes -a Kraft process, for example -are oft en enhanced in order to change the activities. So, it can be useful to use Kraft process models from the literature. 160 Moreover, another fundamental issue is the diffi culty to establish models which take into account the heterogeneity of biomass raw materials. Indeed, feedstocks are generally a mix of diff erent species of biomass. Moreover, the major part of process simulation soft ware was originally destined for the petrochemical industry. Consequently, they only consider liquid or gaseous fl ows. A major diffi culty is then to model complex solid biomass feedstocks. To face this problem, Cohce et al. 161 worked on the gasifi cation of palm oil shell. Th ey worked with Aspen Plus®, which divides mass streams into three categories: mixed, solid, and non-conventional. Biomass is part of the third category. Non-conventional components are defi ned by supplying standard enthalpy of formation and the elementary composition (ultimate and proximate analyses) of the components may also be defi ned. Th is conversion of biomass into a mixture of carbon, hydrogen, oxygen, sulfur, nitrogen, and ash is used by Nikoo and Mahinpey 162 and Ramzan et al. 163 A similar approach is used by Miltner et al. 164 who consider biomass as a mixture of fi xed carbon, water, and volatile compounds. To describe a solid, three properties are required: heat of formation, heat capacity, and density. 165 Another approach is to consider solid biomass as a high molecular weight hydrocarbon that is present in the Aspen library. Th is approximation permits to obtain the essential macroscale thermal, fl ow, composition, and pressure dynamics. 166

Infl uence of operating conditions

As mentioned before, LCA coupled to process simulation tools is a powerful option to select, design, and optimize a process route with the most sustainable options. Th is method is useful as a decision-making tool for the choice of unit operations between several alternatives. For instance, this method could help to choose a lipid extraction method from biomass between diff erent technologies, such as solvent extraction, supercritical carbon dioxide extraction, and others. Moreover, this optimization could also allow to study the infl uence of operating conditions on the environmental impact scores (and on social and economic aspects). Indeed, a change of operating conditions during the process simulation will lead to a change in the obtained mass and energy balances. Consequently, a change of the environmental LCA results will occur, too. So, it is possible to directly understand and study the sensitivity of the environmental impacts to the changes of operating conditions, such as pressure, temperature, and so on. Indeed, Azapagic [START_REF] Azapagic | Life cycle assessment and its application to process selection, design and optimisation[END_REF] highlighted this infl uence with the assessment of volatile organic compounds abatement technologies at the end-of-pipe. In this study, diff erent LCA were compared, with xylene fl ow rates changes (from 1000 to 20 000 m 3 /h) and concentration changes (from 200 to 1200 mg/m 3 for xylene). Mery et al. [START_REF] Mery | An integrated "process modelling-life cycle assessment" tool for the assessment and design of water treatment processes[END_REF] assessed the environmental impacts linked to operation conditions. Indeed, these functioning conditions make a signifi cant contribution to the impacts of processes, and especially for ozonation processes. Moreover, Eliceche et al. 167 solved a multi-objective optimization with GAMS to determine the optimum operating conditions to apply to minimize the environmental impacts of an ethylene plant. Th ey found that pressure and temperature could have a strong infl uence on several impacts, such as global warming. Another example of the infl uence of operating conditions is the case of microfi ltration processes assessed by Tangsubkul et al. 168 Nevertheless, this practice is still not performed for biorefi neries. For instance, Mesa et al. 169 worked on the restructuring of a biorefi nery based on the use of sugarcane bagasse. Th e study intends to optimize furfural and xylose production. In this case, operating conditions are taken into account for the optimization. Indeed, models representing furfural variations induced by temperature, acid concentration, or reaction time were used. However, this optimization was focused on technical constraints, and therefore no LCA was achieved.

Limits linked to LCC and social LCA

One of the main problems to realize the LCC of a biorefi nery is the fact that is an emerging sector. Consequently, costs undergo important fl uctuations. Indeed, biomass feedstocks prices strongly vary. 103,134 Moreover, it is diffi cult to estimate with precision the infrastructure costs of a biorefi nery installation, due to the lack of background on these new processes. Another crucial point concerns the selling prices of products and co-products, which will undeniably fl uctuate during the following years, due to the increase of biorefi ning activities. Consequently, it is complicated to obtain reliable data to realize an LCC since the fi rst design phases. In the same way, the realization of a social LCA will encounter the same diffi culties concerning data collection. Finally, the absence of a common and harmonized framework for these two methodologies is a paramount obstacle to the development of these assessments.

Links with green chemistry

Previous section highlighted the fact that biorefi neries seem to be the most appropriate and the most environmentally-friendly alternative to petroleum based refi neries, on environmental and economic criteria (170). Moreover, Life Cycle Assessment, coupled to process system engineering tools such as process simulation soft ware, or integrated into a global methodological framework with social and economic assessments, is a powerful tool to assess the sustainability of biorefi neries.

To go further, it could be really interesting to use this methodology in synergy with other techniques used for sustainable development. Th ereby, producing more sustainable products should be possible by applying green chemistry principles to biorefi ning processes, as announced by Clark et al. [START_REF] Clark | Green chemistry and the biorefi nery: a partnership for a sustainable future[END_REF] In fact, some principles have already been put into practice such as the raw materials savings. Indeed, wastes from the food industry can be used as feedstocks for biorefi neries. Th e possibility to create links with other fi elds and industries is particularly interesting and promising. Furthermore, some green chemical technologies could be employed in biorefi ning process routes, such as supercritical fl uid extraction, microwave processing, or catalysis. Th e use of these technologies could lead to a more effi cient use of renewable resources. Indeed, wood contains a large variety of interesting substances: terpenes, sterols, and others which are still not valorized in biorefi neries. In the same idea, lignin is oft en underrated, due to its complex structure, 125 but microwave activation can be used to produce vanillin from lignin. [START_REF] Clark | Green chemistry and the biorefi nery: a partnership for a sustainable future[END_REF] Other promising ways deserve to be more developed, such as process intensifi cation, already used in the chemical industry. [START_REF] Bakshi | The quest for sustainability: Challenges for process systems engineering[END_REF] Moreover, some green metrics are already used to assess processing routes based on biomass, and could be associated with LCA. 171 Indeed, Juodeikiene et al. 172 worked on the production of polylactic acid with biomass, and applied four paramount metrics: material effi ciency, total energy effi ciency, economic added value, and land use. Th e application of green chemistry to biorefi neries could induce a substantial reduction of the environmental impacts and a maximization of potential profi ts. 173

Conclusion

During the last few decades, LCA has been increasingly applied to industrial products. Nevertheless, these evaluations did not highlight the exact contribution of manufacturing activities to global environmental impacts. Consequently, LCA applied to industrial processes have been tested in many sectors, mainly to chemical activities. Th ese new considerations permitted a complete and detailed comprehension of all the UOs included in a production process, i.e., the understanding of the infl uence of operating conditions and of the synergistic eff ects between the diff erent unit operations. Nevertheless, this approach was only achievable on already designed processes, to obtain a suffi cient amount of data essential to realizing the LCA. Th erefore, process simulation soft ware has been used to predict data and obtain mass and energy balances of the processes. Th e constant development of new biomassbased plants and the generalization of the application of LCA to processes presage signifi cant changes in the industrial sector. Indeed, worldwide societies realize the necessity of a transition toward more respectful production practices.

Th e fi rst part of the article is a literature review which underlined the diff erent works and studies related to LCA of biorefi neries. 39 publications have been identifi ed and detailed. Th e review can be separated into three parts: LCA of biorefi neries for feedstocks comparison, LCA of biorefi nery process alternatives and LCA coupled to process simulation for process assessments.

In the second part of the paper, a new methodology for a sustainable eco-design of biorefi ning processing routes has been proposed. Th is promising way for improving consists in an integrated assessment of economic, environmental, and social considerations of biorefi nery processes, on a life cycle perspective. Upstream of these analyses, a process simulator is used to facilitate data collection, for environmental LCA achievement. Finally, a multi-objective optimization of the process is performed, supported by a decision-making tool to identify the most sustainable designing way of a biorefi nery process. Some of the main limits and ways for improving of this methodology have been identifi ed and discussed. Th ese locks can relate to the application of LCA to bio-based products, to the process simulation, or to the assessments of economic and social dimensions.

Th is new framework could facilitate and develop sustainable design of biorefi nery processes and help to the construction of a more sustainable industry in the future.

Figure 2 .

 2 Figure 2. Simplifi ed model of a bio-based product fl ow-chart for biomass feedstock.17,20

Figure 4 .

 4 Figure 4. 2D and 3D Pareto curves obtained in multi-objective optimizations.[START_REF] Azapagic | Life cycle assessment and its application to process selection, design and optimisation[END_REF]

Table 1 . Application fields and characteristics of studies dealing with LCA and simulation of biorefinery processes.

 1

	Environmental LCA	Gate-to-gate	GWP or a single metric, the total	eco-indictor 99				Cradle-to-gate	GWP, ADP, AP, EP, FAETP, HTP,	MAETP, ODP, POCP, TETP, Land use	Cradle-to-gate	Greenhouse gases emissions	Cradle-to-gate	Human health, ecosystem quality, cli-	mate change, resources depletion	Cradle-to-gate	Ecoscarcity06, Ecoindicator99, GWP	Gate-to-gate	Cradle-to-gate	ADP, AP, EP, GWP, ODP, HTP, POCP
	Simulation	Equations repre-	senting each unit	operation				Aspen Plus®			Aspen Plus® and	Aspen HYSYS®	Aspen HYSYS®	Ariane®		-		PROII®	-
	Assessed processes	Drying of the cellulosic biomass feedstocks, air sepa-	ration unit, gasifi cation,	syngas conditioning, Fischer-Tropsch synthesis,	hydroprocessing, power generation, and the diesel	and	gasoline production	Feedstock cultivation, handling and drying, gasifi ca-	tion, syngas cleanup and conditioning, synthesis,	alcool separation	Ethanol-route process and syngas-route process		Acid-catalyzed process			Thermochemical production		Heterogeneous catalysis, enzymes, homogeneous	catalysts, fermentations, purifi cation steps	Cleaning, extraction, concentration, fermentation,	distillation, dehydration
	Application fi eld	Hydrocarbon biorefi nery via	gasifi cation pathway					Thermo-chemical biorefi nery	for bioethanol production		Biomass-derived resins (poly-	ethylene and polypropylene)	Biodiesel Production from	waste vegetable oils		Synthetic natural gas (SNG)	production process	from woody biomass	Bioethanol production	Butanol production in sugar-	cane biorefi neries
	Source	Wang et al. 83						Jeswani et al. 55			Mayumi et al. 84		Morales Mendoza et al. 85			Gerber et al. 86-90		Alvarado-Morales et al. 91	Pereira et al. 92

GWP, global warming potential; ADP, abiotic depletion potential of elements and fossil fuels; AP, acidifi cation potential; EP, eutrophication potential; FAETP, freshwater aquatic ecotoxicity potential; HTP, human toxicity potential; MAETP, marine aquatic ecotoxicity potential; ODP, ozone depletion potential; POCP, photochemical ozone creation potential;

Table 2 . Multi-objective optimizations considering sustainability criteria.

 2

	Indicators		GWP, ADP, ODP, HTP, EP, AP, POCP, operating costs		Eco-indicator 99 unique score, total annualized cost		GWP, ADP, AP, EP, FAETP, HTP, MAETP, ODP, POCP, TETP, capital	costs, total annualized costs, levelised costs, security and diversity of	supply, public acceptability, health and safety, intergenerational issues	GWP, ODP, POCP, AP, EP, HTP, AETP, TETP, cumulative cash fl ow,	purchase cost, utility cost	Annual earnings, break even, profi t opportunity	Capital costs, operating costs, biomass costs	Energy effi ciency, exergy effi ciency, operating costs, total production	costs	GWP, POCP, Ecotoxicity, AP, ODP, Human health non-cancer, EP,	Human health cancer, Human health	Particles, Profi tability, Investment, Energy economics, Supply chain	profi t	GWP, net present value		Total annualized cost, greenhouse gas emissions, number of accrued	local jobs
	Methodologies		LCA, economic analysis		LCA, economic analysis		LCA, LCC, social LCA			LCA, economic analysis		Economic analysis	Economic analysis	-		LCA, economic analysis				LCA, economic analysis		LCA, economic analysis, social	input-output anaysis	Market analysis, techno-eco-	nomic study, LCA, supply chain	analysis
	Application fi eld Sustainability	considerations	Vinyl chloride plant Environment,	economy	Absorption cooling Environment,	systems economy	Energy systems Environment, econ-	omy, social		β-galactosidase Environment,	production economy	Biorefi nery Economy	Biorefi nery Economy	Biorefi nery Thermo-economic		Biorefi nery Environment,	economy			Biorefi nery Environment,	economy	Cellulosic Environment, econ-	Biofuel omy, social	Biorefi nery Environment,	economy
	Source		Khan et al. 98		Gebreslassie et al. 99		Santoyo-Castelazo and	Azapagic 100		Carvalho et al. 101		Lundberg 102	Wright and Brown 103	Gassner and Maréchal 105		Janssen et al. 106				Gebreslassie et al. 107		You et al. 108	Mansoornejad et al. 109

-GWP, global warming potential; ADP, abiotic depletion potential of elements and fossil fuels; AP, acidifi cation potential; EP, eutrophication potential; FAETP, freshwater aquatic ecotoxicity potential; HTP, human toxicity potential; MAETP, marine aquatic ecotoxicity potential; ODP, ozone depletion potential; POCP, photochemical ozone creation potential; TETP, terrestrial ecotoxicity potential; AETP, aquatic ecotoxicity potential

Acknowledgments

Th e fi nancial support allocated to this project by the French Ministry of Higher Education and Research (MESR) is gratefully acknowledged.

Rémi Julio

Rémi Julio: Chemical Engineer, PhD student in Chemistry of Agroresources and Life Cycle Assessement, in the Laboratory of Agro-Industrial Chemistry. Researches in combining LCA and Chemical Engineering for the ecodesign of agro-industry processes.

Caroline Sablayrolles