Erry Ika Rhofita

Ridwan Rachmat

Michel Meyer

Ludovic Montastruc

Mapping analysis of biomass residue valorization as the future green energy generation in Indonesia

Keywords: Biomass energy potential, agricultural residue, forest residue, timber processing residue

Biomass residue is one of the focus areas for green energy in Indonesia, elaborated in Government Regulation no 79 the year 2014 on national energy development. The assessment of residual resources is an important way to show the availability distribution to realize the target of biofuel is more than 5% of the energy supply in 2025. Thus, this paper will present a method to assess the energy production from biomass residue as a primary consideration in its development. Statistical data and field observations have been used to estimate the total availability of residue. Furthermore, to calculate the energy potential of biomass residue, the minimum and maximum value parameters, such as residue to product ratio, moisture content, and heating value, were obtained from works of literature. The power potential was also analyzed through three scenarios of the conversion factor efficiency, i.e., low, medium, and high, to provide comprehensive results.

The proposed methods allow the annual Indonesian biomass residue production from agriculture and forest residue to be nearly 155,271 and 2,554 tonnes, respectively. It can be generated an energy potential around 1261 PJ, covering 22.12% of national energy consumption. Given the high potential for sustainability in biomass residue supply and utilization, strategic factor in the areas of the government regulation and policy, greenhouse gasses emission, land-use change, and conversion technology were identified to support residue valorization in the context of planning, organizing and operating. The challenges and barriers that can be minimized by integrated collaboration and synergy among policymakers, entrepreneurs,

Introduction

Fossil fuel has a vital role in human-kind activities, which influence growth, development, and progress in all nations' economic, social and security sectors. Annually, the significant global energy demand continues to happen, fossil fuel consumption has increased by more than 50%, and it is expected to rise by another 18% over the next two decades (Yıldız, 2018).

It can be potentially catastrophic in political, socio-economic, and environmental ramifications due to the overuse and depletion of energy reserve [START_REF] Oyedepo | Energy and sustainable development in Nigeria: the way forward[END_REF]. However, since implementing sustainable development goals, biomass energy sources are one of the solutions to reduce the problems. For example, natural gas can be partially substituted by biogas produced from food waste as the most voluminous solid waste via anaerobic fermentation [START_REF] Maroušek | Advances in nutrient management make it possible to accelerate biogas production and thus improve the economy of food waste processing[END_REF]. The charred bio-waste as a solid fuel can replace coal to support long-term energy supply by considering the economic and ecological aspects [START_REF] Mardoyan | Analysis of Czech Subsidies for Solid Biofuels[END_REF]. In the sustainability concept, waste cooking oil or vegetable oil can be processed as biodiesel to substitute diesel oil in specific applications (i.e. public transport and hybrid or marine propulsion) [START_REF] Maroušek | Advances in nutrient management make it possible to accelerate biogas production and thus improve the economy of food waste processing[END_REF]. Similarly, forest residue, such as palm oil fronds and leaves and rubber-wood sawdust, can replace 5% to 10% of gasoline applications in the transportation sector through bioethanol conversion [START_REF] Hossain | Bioethanol production from forest residues and life cycle cost analysis of bioethanol-gasoline blend on transportation sector[END_REF].

On the other hand, immediate application of biomass as clean energy due to the increase in crude oil price has forced the upgrading of biofuel production capacity [START_REF] Oláh | The Role Of Biofuels In Food Commodity Prices Volatility And Land Use[END_REF], which can be immense potential he environmental issues (e.g., land-use competition, landuse change, deforestation, and water supply pressure). Moreover, the land availability to cultivate the bioenergy crop has been slight. As a result, to minimize these problems, marginal and degraded land optimization is one of the sustainability solution to reduce the conflict between food, industry, and fuel production according to the community background [START_REF] Edrisi | Exploring marginal and degraded lands for biomass and bioenergy production: An Indian scenario[END_REF]. Therefore, these problems can also be solved by using biomass residues as a sustainable raw material for bioenergy.

Biomass residue utilisation has an enormous potential; several parameters must be considered, such as conversion processes and biomass characteristics based on the geographical, economic and social factors [START_REF] Wang | Temporal-spatial variation analysis of agricultural biomass and its policy implication as an alternative energy in northeastern China[END_REF]. In geographic view, climate and spatial model affect biomass's availability and distribution [START_REF] Chinnici | Analysis of biomass availability for energy use in Sicily[END_REF].

Consequently, the impact of different geographic areas will determine the biomass residue properties, such as residue-to-product ratio, moisture content, and heating value. However, in the long term, biomass application can be a part of the solution to environmental problems.

Several researchers have described the advantages of residue utilization in reducing greenhouse gas emissions (GHG). In Alberta, Canada, the utilization of agriculture and forest residue for energy production could be predicted to reduce 11-15% of GHG emissions by substituting 14-17% of total energy demand in 2030 (Weldemichael and Assefa, 2016). In Uttar Pradesh, India, biomass can reduce more than 50% to 80% of GHG emissions compared to fossil fuels (coal and natural gas) as a power source (Hiloidhari et al., 2019). If China can replace around 27% of fossil fuels with bioenergy, it will reduce GHG emissions by 49% by 2050 [START_REF] Kang | Bioenergy in China: Evaluation of domestic biomass resources and the associated greenhouse gas mitigation potentials[END_REF].

Indonesia is an agrarian country whose land covers nearly 200 million ha, approximately 48.96% of forest area and 31.77% of agriculture area in 2018 (Fig 1). Almost all of the forest land is used for dryland forest (74.57 million ha), while agriculture land is cultivated for rice and cereals (7.88 million ha) ("Statistics Indonesia," 2020). Given the fact that there is vast biomass potential as a sustainable energy feedstock, there is an abundant residue that can be converted to heat and electrical energy forms. However, most of the residue was burned in the field area, and a small amount was utilized as feed, burned as fuel for cooking in households and small industries, as fertilizer, or left on the farm for soil conservation.

Farmers' most well-known method of lowering costs and time is open burning in the field area, but the activity harms the health of nearby communities, soil structure, biodiversity, and air pollution. There is no comprehensive data on the quantity and distribution of Indonesian biomass residue on a local, regional, and national scale, nor any record of the total used and disposed of at the final landfill. However, when the phenomena are associated with the national energy planning goals according to Presidential Regulation No. 22 The years 2017 which explains that in 2025 and 2050, biomass could generate electricity at about 5.5 GW and 26 GW, respectively, the opportunity for biomass residue valorization is highly open for commercial purposes in all regions. Thus, the assessment of biomass residue as a basis to implement these programs considers the model of sustainable development. To evaluate the sustainability of biomass residue resources, the global scale, scope, and boundary must be determined as a basic calculation. Furthermore, the biomass potential types (e.g., theoretical, technical, economic, and implementation potential) as an important parameter in deciding the assessment approach using one of the following approaches: resource-focused, demand-driven, or integrated approaches [START_REF] Batidzirai | Harmonising bioenergy resource potentials-Methodological lessons from review of state of the art bioenergy potential assessments[END_REF]. Many researchers have analyzed the residual resources for bioenergy production in some regions with various approaches and methods. In this article, the complete literature review of the methodology of biomass residue assessment is presented in the Supplementary Document.

The study aims to assess Indonesia's sustainable biomass residue potential for bioenergy purposes. The spesifics objectives have been set to archieve the overal goals: to identify and calculate the total residue and energy production in national scale by using the statistical and government report; to estimate the power energy generation, the energy efficiency scenarios have been used according to the literature review, and to support the biomass energy development as a national energy substitution, and the strategic factor will decribes to determine the future perspective of residue utilization.

The results will provide comprehensive information on biomass residue potential across Indonesia. Favorable results could be helpful to increase awarness and promoting of residue utilization as sustainable energy sources in the future. Producing green energy from agriculture and forest residue could positive impact to the community and environment, such as streghten the energy security, improve the social-economic, reduce environmental problems, and decreasing dependent to fossil fuel. Page 5 of 35

The strategic factor for biomass residue development in Indonesia

The current debate about the future of bioenergy is focused on how to best generate green energy by utilizing biomass residue based on technological advancement, environmental benefits, and socioeconomic potential. It should consider the embeddedness of the last issue in a macro system in which the influence factors of biomass residue utilization interact and can hardly be separated. In this section, the supporting view points of biomass residue utilization will be explained in detail, i.e., government regulation and policy, greenhouse gas emissions, land-use change, and technology development.

Government regulation and policy

The sustainability of Indonesia's energy supply is a significant challenge due to the gradually increases demand annually. In 2020, the total primary energy supply, i.e., coal, oil, natural gas, biomass and other renewable energy, reached 3388.83 PJ, 2891.96 PJ, 1536.46 PJ, 326.48 PJ and186.17 PJ, respectively. Whereas the total consumption is nearly 5497 PJ, composed of 43% of transportation, 34% of the industry, 16% of households, 5% of commercial, and 2% others. To mitigate these problems, the fossil fuel reserve continually depletion and global commitment to reduce greenhouse gas emissions improve Indonesian government is committed to enhancing national energy security, one of which is through biomass energy production. It has been proven by the policies and regulations that are related to biomass development (See Supplementary Materials).

Traditional biomass utilization is associated with side effects on the environment, such as indoor air pollution and deforestation. The replacement of modern biomass energy combined with more efficient technology conversion needs the guarantee of quality. It is clear that Indonesia has a huge potential for competitiveness to improve its biomass energy output. This should be supported by the standardization of biomass products like in developed countries.

For example, the European Union has guidance of EN 14961-2 to guarantee the quality of wood pellets sold in the market [START_REF] Duca | Wood pellet quality with respect to EN 14961-2 standard and certifications[END_REF]. The South Korean government stated that the biomass pellets produced and exported must have comparable properties to the Wood Pellet Quality Standard from the Korea Forest Research Institute [START_REF] Oh | Fuel Properties of Woody Pellets in Domestic Markets of Korea[END_REF].

While France does not have official wood pellet standards, it has established quality control (ITBE) based on the combustion installation type, such as stove, boiler, and incinerator [START_REF] Garcia-Maraver | A review of European standards for pellet quality[END_REF]. Denmark, the Netherlands, and the United Kingdom require a supplement to the biomass power plant's periodic report on the land sustainability assessment result and air pollution produced by its operation [START_REF] Thrän | The dynamics of the global wood pellet markets and trade -key regions, developments and impact factors: The rise of the global wood pellet market, the intensification of trade and future challenges scrutinized in detail[END_REF]. To realize the national green bioenergy goals, the Indonesian government's participation is important through issuing the rules and guidance on the criteria and requirements for biomass process and output that reflect environmental sustainability and market trust.

The government programs that have been launched to support biomass energy development according to the Indonesian President Regulation No. 72 the year 2017 on national energy plans are: 1) guarantee the biomass supply and feedstock; 2) improve the quantity and quality of biomass potential survey; 3) construct the biomass power plant to equalize access to electricity; 4) promote non-edible food as bienergy sources; and 5) research and development of biomass technology. Currently, the big challenge is the low price of coal, but the Indonesian government has issued a regulation on the coal price. In November 2019, the Minister of Energy and Mineral Resources' decision No 224K/30/MEM/2019 explained that the estimated fee of coal per ton was approximately USD 66.27. While in December 2018, the cost per ton of coal was more expensive 40% that is accordance with the Minister of Energy and Mineral Resources' decision No 2025K/30/MEM/2018. The coal operational fee per kWh of electricity generated was set at 0.05 US dollars. It contrasted condition with the micro-hydro and geothermal value of of 0.06 US dollars and 0.08 US dollars, respectively. It means that the assumption is that conventional power plants the economic operating costs.

Traditional biomass utilization is associated with side effects on the environment, such as indoor air pollution and deforestation. The replacement of modern biomass energy combined with more efficient technology conversion needs the guarantee of quality. It is clear that Indonesia has a huge potential for competitiveness to improve its biomass energy output. This should be supported by the standardization of biomass products like in developed countries.

For example, the European Union has guidance of EN 14961-2 to guarantee the quality of wood pellets sold in the market [START_REF] Duca | Wood pellet quality with respect to EN 14961-2 standard and certifications[END_REF]. The South Korean government stated that the biomass pellets produced and exported must have comparable properties as the Wood Pellet Quality Standard from the Korea Forest Research Institute [START_REF] Oh | Fuel Properties of Woody Pellets in Domestic Markets of Korea[END_REF]. While France does not have official wood pellet standards; it has established quality control (ITBE) based on the combustion installation type, such as stove, boiler, and incinerator [START_REF] Garcia-Maraver | A review of European standards for pellet quality[END_REF]. Denmark, the Netherlands, and the United Kingdom require a supplement to the biomass power plant's periodic report on the land sustainability assessment result and air pollution produced by its operation [START_REF] Thrän | The dynamics of the global wood pellet markets and trade -key regions, developments and impact factors: The rise of the global wood pellet market, the intensification of trade and future challenges scrutinized in detail[END_REF]. To realize the national green bioenergy goals, the Indonesian government's participation is important through issuing the rules and guidance on the criteria and requirements for biomass process and output that reflect environmental sustainability and market trust.

Greenhouse gasses emissions

Greenhouse gas emissions are a continuing contentious issue in any energy sector, except biomass energy. Biomass energy can have positive value in reducing GHGs, particularly when applied in sustainable production and management contexts. For example, when biomass is applied efficiently to generate electricity and heat by modern conversion technology, but the traditional application in households has a role in creating indoor air pollution when the utilization does not observe environmental criteria. It should be noted that biomass application is related to technology conversion, therefore it needs a detailed environmental assessment through Life Cycle Assessment (LCA) to discover the precise percentage contribution to GHG's.

When the biomass residue is not utilized optimally and the amount is abundant, this is the major contributor to GHGs in post-harvest activity. Most farmers in developing countries prefer burning the biomass residue in the field compared to managing it as a bioenergy source. Overall, they have the perception that open burning can minimize the cost and time of management for the next planting. In fact, this activity can damage the soil structure due to diminished soil nutrients and be a reason for erosion in the long term (Chen et al., 2017). In Indonesia, during the dry season from August to September, the open burning of rice residue almost happened in a part of Java Island (i.e., East Java, Central Java, and West Java provinces) and South Sumatera province as a leading agricultural areas (Permadi and Kim Oanh, 2013).

In 2015, it could be estimated that the production of GHGs emmissions reached 20,874.55 Gg per year CO2; 3,088.27 Gg per year CO, 164.63 Gg per year CH4, 53.22 Gg/year NOx, 34.33 Gg per year SO2 and 51.33 Gg per year OC, respectively (Andini et al., 2018). To mitigate these phenomena, the rising public awareness is needed through the education and training about GHG's impact on environment and more important how to increase the benefits of biomass residue as a sustainable energy source by taking note of the material and technological purposes. It is supported by the government role to promote the biomass energy on transportation and industrial sector, to reduce roughly 5% of CO2 emissions annually

Land-use change

In recent years, the land-use change was a fundamental problem in globalization and industrialization. It has an impact on the gradual decrease in agriculture area and deforestation. In the bioenergy scenario context, reducing GHG emissions also provokes land use competition in the long term. Therefore, crop residue utilization as bioenergy could be a simple solution to synergi between food and energy security [START_REF] Lambin | Global land use change, economic globalization, and the looming land scarcity[END_REF].

In recent years, land-use change has been a fundamental problem in globalization and industrialization. It has an impact on the gradual decrease in deforestation and agricultural areas. In the bioenergy scenario context, reducing GHG emissions also provokes land use competition in the long term. Therefore, crop residue utilization as bioenergy could be a simple solution to synergi between food and energy security [START_REF] Lambin | Global land use change, economic globalization, and the looming land scarcity[END_REF].

To support these solutions, since the last decade, the degraded land restoration program has promoted the production of bioenergy from non-edible oils, such as nyamplung (Calophyllum inophyllum L.) and Jatropha curcas. It was proven that nearly 50% of degraded land is a significant decrease of about 14.01 million ha in 2018 compared to 2011 (Statistik Indonesia). In general, the critical land use integration for green energy production has several benefits for the environment, i.e., it minimizes the impact of unlimited carbon storage, prevents soil erossion, and maintains biodiversity [START_REF] Blanco-Canqui | Growing Dedicated Energy Crops on Marginal Lands and Ecosystem Services[END_REF]. Moreover, it has created new job prospects in rural areas to improve the socio-economic situation of the community [START_REF] Dauber | Bioenergy from "surplus" land: environmental and socio-economic implications[END_REF].

Since a decade ago, the degraded land restoration program has promoted the production of bioenergy from non-edible plants, such as nyamplung (Calophyllum inophyllum L.) and Jatropha curcas. It was proven that nearly 50% of degraded land is a significant decrease of about 14.01 million ha in 2018 compared to 2011 (Statistics Indonesia, 2022). In general, The integration of critical land use as bioenergy has several benefits for the environment, i.e., it minimizes the impact of unlimited carbon storage, prevents soil erosion, and maintains biodiversity [START_REF] Blanco-Canqui | Growing Dedicated Energy Crops on Marginal Lands and Ecosystem Services[END_REF]. Moreover, it has created new job prospects in rural areas to improve the socio-economic situation of the community [START_REF] Dauber | Bioenergy from "surplus" land: environmental and socio-economic implications[END_REF].

Few models were developed to review the effect of land-use change on biofuel production; for instance, the GHG emissions can determine land-use change decisions during the biomass energy production by Calculating Uncertainty in Biomass Emissions (CUBE) model [START_REF] Curtright | Scenario uncertainties in estimating direct land-use change emissions in biomass-to-energy life cycle assessment[END_REF]. A separate method was used to assess the land-use change by mitigating impacts on perennial plants due to mapping and quantifying the degree of accumulated soil organic carbon losses by wind and water erosion, nitrogen emissions to water, and recurring floods [START_REF] Englund | Beneficial land use change: Strategic expansion of new biomass plantations can reduce environmental impacts from EU agriculture[END_REF]. The economic model is also applied to explain the correlation between land-use change, the economy, and biomass production for electricity [START_REF] Fargione | The Ecological Impact of Biofuels[END_REF]. The existence and application of bioenergy policies determine the demand proportion of land utilization in agricultural and marginal lands (Warner et al., 2013). The important point to note, however, is how the sustainable program minimizes land-use change while supporting the community's social-economic well-being.

The sufficient energy village (Desa Mandiri Energi) is one of the implementations to manifest minimalizing land-use change. The first key is to strengthen collaboration among farmers, government, industry, and academics by increasing farmer awareness and participation in crop residue utilization, facilitating infrastructure provision and market share through cooperation and institutional development, and sharing information through education and training to improve sustainable cultivation programs.To optimize these, government regulations and policies have been issued to protect land-use change, which impacts environmental issues and biomass energy supply (see Suplementary Document).

Biomass technology conversion

Agricultural and forest residues have a huge potential as bioenergy, which can be transformed into solid fuel (i.e., pellets and briquettes), liquid fuel (i.e., biodiesel and bioethanol), and gas in the form of syngas. The biomass conversion technology is a major factor in generating the quantity and quality, but it should be noted that crop type, cost of handling, and emission level were also factors. For example, secondary industrial waste has a high moisture content and is not suitable for being converted by thermochemical, but it is suitable for being converted via biochemical. The utilization of each conversion method has some benefits, which follow the purpose of the biofuel produced. There are three main processes for transforming biomass into bioenergy that are thermochemical, biochemical, and physical. The representation of biomass residue development in Indonesia can be described in Fig. 2.

Fig. 2. Indonesian biomass residue processes

The thermochemical conversion uses high heat energy to resolve the bond of the organic matter through devolatilised, depolymerise, and oxidised activities into biochar (solid), synthesis gas and bio-oil (liquid) [START_REF] Lee | Waste to bioenergy: a review on the recent conversion technologies[END_REF]. This process involves direct combustion, pyrolysis, gasification, torrefaction, carbonisation and thermal liquefaction [START_REF] Dayton | Biomass Conversion[END_REF]. More over, It has high efficiency and quicker reaction time than biochemical activity, but it depends on the operational temperature and environmental conditions [START_REF] Adams | Biomass Conversion Technologies[END_REF]. Contrary to thermo-chemical process, the biochemical process needs biological activators such as enzymes, bacteria, yeast and biocatalyst, for degrading the biomass structure in conversion processes. There are two methods to transforming i.e., fermentation to produce bioethanol and anaerobic disgestion to generate biogas [START_REF] Dayton | Biomass Conversion[END_REF].

Lastly, the physical process uses mechanical force to convert biomass to solid fuel through the densification process or bio-oil via extraction. The physical process uses mechanical force to convert biomass into solid fuel through densification and extraction. Moreover, the physical process is a pre-treatment to make material handling easier.

In Indonesia, the most widely applied biomass conversion technologies on small scales are direct combustion, carbonizing, and biogas. In the case of electricity production, the thermo-chemical conversion via the gasification process has operated in recent years as a power plant. At the end of 2018, the palm oil residue was utilized as a raw material at biomass power plant in Siantan, Kalimantan, generating annual electrical production roughly 0.27 PJ.

In the third quarter of 2019, the bamboo residue could generate 5.1 TJ per year in Siberut Island. However, the biomass transformation will continue to be refined to achieve the national plan of biomass energy, which is to reach 5.5 GW in 2025 and 26 GW in 2026.

Materials and methods

The estimation of Indonesian biomass residue potential energy considers the amount of energy available from each residue resource. Firstly, calculate the total residue during the temporal cycle in all regions, which depends on crop properties and energy content. Furthermore, a scenario is adopted to define the detailed range of energy that predicts the electrical energy potential.

Study Ares

Indonesia is located between 6° northern latitude and 11° southern latitude and 95° -141° east meridians, part of the Southeast Asia region, cover 1,904,569 km 2 . As shown in Fig. 1, agriculture and forest covered nearly 61 and 94 million hectares, respectively. In the agriculture sector, the main commodities are rice, corn and cassava in the food crop and and palm oil in the plantation crop. In 2019, food crops production slightly decreased by 7.76% in rice, while corn and cassava gradually increased by 3.91% and 1.51%, respectively. Those quantities were recorded approximately 54,60 million tonnes of rice, 29.90 million tonnes of corn and 16.52 million tonnes of cassava. Moreover, Indonesia is the largest producer of palm oil, accounting for nearly 43% of the world's palm oil production (Widiyanto et al., 2019). In the forest sectror, total log production roughly increased 4.36% in 2019, reaching 57.93 million m 3 . At the same time, the processed timber production, such as chips and particles, plywood, swan timber, veneer, and fibreboard are around 29.73 million m 3 , 3.99 million m 3 , 2.59 million m 3 , 2.10 million m 3 and 0.5 million m 3 , respectively (Subdirektorat Statistik Kehutanan, 2020).

In the energy view 2019, Indonesia's primary energy supply consisted of 35% oil, 37.3% coal, 18.5% natural gas, 2.5% hydropower, 1.7% geothermal and 3% biofuel (MEMR, 2019). In the last decade, primary energy demand has increased by 3% per year, while energy consumption rose from 0.017 TJ per capita in 2016 to 0.021 TJ per capita in 2019 [START_REF] Bp | BP Statistical Review of World Energy[END_REF].

Indonesia also has a huge potential for renewable energy sources, (e.g. solar, wind, hydro, biomass, ocean and geothermal), has an estimated value of approximatelly 1.59 PJ [START_REF] Memr | Outlook Energi Indonesia 2019[END_REF]. It has great potential to develop green energy programs to reduce GHG emissions.

Data sources and collection

This investigation focused on agriculture and forests residue that is are subject to possible exploitation as an energy source. Several agriculture products, such as food crops (i.e. rice, maise, cassava, groundnut, and soybeans) and plantation crops (i.e. sugarcane, coconut, palm oil, coffee, and cocoa) are principally commodities in all the Indonesian areas throughout year.

The availability of forest products derived from the harvesting of natural forests (i.e. Acacia sp., Eucalyptus sp, Tectona grandis LF, Meliaceae, and Albizzia falcataria), industrial forest plantations (i.e. Shorea spp, Mixed forest, Intsia bijuga and Dipterocarpus borneensis), and wood processing mill residues considered from technical, ecological, and sustainability aspects due to the limitation of forest production.

To achieve the research goal, the annual crop production and cover harvested area have been drawn from statistical data collected over ten years by the Indonesia Central Bureau of Statistics (BPS). Specifically, the annual report and strategic documents from the Agriculture Ministry (i.e., the Outlook Food Crop Report and the Outlook Plantation Crop Report started in 2010 to 2020) to discover the geographic location of the products. The major information on wood and timbre processing yield and distribution was obtained from the Forest Production Statistics Report started in 2010 to 2020 by the Environmental and Forestry.

In this study, the physical properties of biomass residue, such as moisture content (M), residue-to-product ratio (RPR), and lower heating value (LHV) of dry matter, were obtained from numerous studies in the last 20 years to maintain data accuracy and validity (See Appendix A and B).

The availability factor (A) used the literature review as a basis study to estimate the amount of residue for bioenergy purposes. A random sampling of the residues was performed by interviewing 100 stakeholders (i.e., farmers, agriculture and wood suppliers, agricultural extension, researchers in agriculture and forestry agencies, and academics) to recognize the biomass residue availability in post-harvest. The sampling locations are in several provinces on Java Island, such as East Java, Central Java, and West Java for the agriculture sector. And in Kalimantan island, i.e., East Kalimantan, Central Kalimantan, and East Kalimantan for forestry products. The main reasons for selecting these are the high biomass residue potential due to above-average production and harvested area. To validate these data, the minimum and maximum value are applied to calculate the numerical data of biomass residue properties by a mathematical model (See Appendix).

Key parameter to assessment biomass residue

The energy potential of agriculture and forest residue is estimated in this section.

Theoretical potential quantity of biomass residue

The Residue-to-Product Ratio (RPR) related to total residue was generated from a tonne of harvested dry crop production. For example, the RPR of rice straw is 1.75, which means that a tonne of total rice production on a dry basis could generate 1.75 tonnes of rice straw according to the physical characteristics, cultivation method, and crop variety. RPR value as the basis to estimate the Theoretical Biomass Residue Potential (TBR) quantity. To calculate the TBR of agricultural residue, Eq. ( 1) is used, [START_REF] Di Fraia | Energy potential of residual biomass from agro-industry in a Mediterranean region of southern Italy (Campania)[END_REF].

(1)

Where HA(i) is the annual harvested area of crop in hectare per year, P(i) is the annual productivity of crop in tonne per hectare per year, RPR(i) is the residue to product ratio, and MC(i) is moisture content of crop residue in percentage term.

The theoretical quantity of forest biomass residue depends on the density of wood density and the recoverability factor related to the generated timber residue. The wood's density was obtained from the open-access database of tree density on the website http://db.worldagroforestry.org. In contrast, the density of timber processing was obtained from the Ministry of Environmental and Forestry data and field observation, which is similar to determining the availability factors (see Section 3.2). To calculate the TBR of forest residue can be expressed in Eq. ( 2), [START_REF] Di Fraia | Energy potential of residual biomass from agro-industry in a Mediterranean region of southern Italy (Campania)[END_REF].

(2)

Where AP(i) is the annual production of wood product in ton per year, ( ) is the density of wood in kg m -3 and R(i) is the recoverability factor of timber. In this study, logging and wood processing residue recoverability factors were 0.25 and 0.42, respectively (Mboumboue and Njomo, 2018a). In Indonesia, the residual factors reach 30.5% and 16.4% of natural and industrial forests in Kalimantan, Papua, and Sumatra. Those indicate that every 1m 3 of log produced 0.351 m 3 and 0.153 m 3 residues from natural woods and industrial forest and timber manufacture (i.e. plywood, sawdust wood and veneer) reach 0.6 m 3 [START_REF] Simangunsong | Potential forest biomass resource as feedstock for bioenergy and its economic value in Indonesia[END_REF].

Availability Potential of Biomass Residue

The Availability Biomass Potential (ABP) is calculated from the total residue production for bioenergy purposes after deducting for other purposes (e.g. animal feed, fertilizer, etc).

More competitive uses of biomass residue mean less availability of biomass. The availability value of each crop in each area dramatically varries according to the harvesting methods and equipment. For example, when rice harvesting, the height of the cutting and threshing process influences residue production. The straw and husk that are generated using manual techniques and have an uncertain quantity compared to the agricultural machinery. The availability factor is a basics for evaluating the availability of biomass residue, as given in Eq.

3, [START_REF] Avcıoğlu | Assessment of the energy potential of agricultural biomass residues in Turkey[END_REF].

(3)

(3)

Where A(i) is the availability factor of biomass residue as a percentage.

Energy potential of biomass residue

The Energy Potential of Biomass (EPB) could be estimated by biomass's lower heating value (LHV) on a dry basis, as presented in Eq. 4, [START_REF] Avcıoğlu | Assessment of the energy potential of agricultural biomass residues in Turkey[END_REF].

(4)

Power potential of biomass residue

Biomass residue can be converted to reen energy by precise technology selection. The efficiency of energy process production depends on crop residue (moisture content) and its route. There are two types of biomass energy conversion, i.e. thermochemical conversion and bio-conversion, which have certain moisture content requirement. The thermochemical conversion is more suitable to generate and store heat, mechanical power, and electricity ompared to bio-conversion [START_REF] Singh | Energy potential through agricultural biomass using geographical information system-A case study of Punjab[END_REF]. For any types of biomass residue, the thermochemical process efficiency ranged from 20 to 40% [START_REF] Singh | Overview of electric power potential of surplus agricultural biomass from economic, social, environmental and technical perspective-A case study of Punjab[END_REF]. The amount of power potential biomass (PPB) as presented in Eq. 5, [START_REF] Román-Figueroa | Bioenergy potential from crop residue biomass in Araucania Region of Chile[END_REF].

(5)

Where, is an efficiency conversion factor, in this study, the efficiency factors use three levels, i.e. low, medium and high efficiency were 20, 30, and 40%, respectively. OH(i) is the time operation of technology conversion in an hour, in this case, 8000 hours per year.

Results and discussions

The theoretical availability, energy potential and power potential Indonesian biomass residue potential from agriculture and forest sectors were estimated by Eq. ( 1) -( 5), based on Tables 1 and2.

Agriculture residue energy and power potential

In recent decades, the annual average agriculture production has reached 136.22 million tonnes, with the top ten commodities recorded. The analysis by Eq. ( 1) -( 3) shows that rice, corn and palm oil ranked in the first three places of agriculture product, with 75.97; 54.98 and 15.24 million tonne of dry biomass residue, respectively. Rice straw and husk, and maize cob and stalk as food crops have great opportunities to be converted into bio-energy through densification processes due to their their being found in most areas in Indonesia regions.

Otherwise, palm oil as a plantation crop is only cultivated in a part of Sumatra, Borneo, Celebes and Papua island. However, palm oil residue (i.e. empty fruit brunch, shell and fibre)

has been utilized as a raw material in biodiesel production due to the Indonesian government's mandate to mix 20% biodiesel (B20) starting in 2018. The result of this study estimated the energy potential of agricultural residue at more than 300 PJ.

Fig. 3 present the total availability residue production and energy potential for (a) food and (b) plantation crop during 2011 -2020. Rice straw and husk have half the total residue of food crops and can generate over 50% of their energy potential. While palm oil is a plantation crop produce 82% of residue, it can generate nearly 60% of its energy potential. It has to be underlined that the biomass characteristics were taken into the maximum and minimum limitation values. Furthermore, several properties, such as productivity and RPR have an essential role in determining the amount of residue, but the moisture content on a dry basis is the final factor to show the total residue production. Finally, the LHV is the main factor to calculate the energy potential of residue. The analysis results reflect that rice, corn and palm oil can be promote as food and energy security for future investment. In addition, the cultivation geography, such as location altitude, weather, soil quality and water resources has influence on the physical properties of the crop. The harvesting methods and agricultural machinery also have a relationship with the residue yield. For example, in rice harvesting, the utilization of a rice harvesting machine will produce a homogenouz size of straw compared to the manual method of using a sickle. When the crops produce the highest amount of residue, it could be considered to plan and create the supply chain for biomass valorization.

The main supports for launching sustainable bioenergy generation are stakeholder awareness, policy and regulation, and infrastructure. The agriculture residue as power generation were analyzed by three scenarios of efficiency conversion factor and time operation of 8000 hours per years (Fig. 4). When Eq. ( 5) has applicated to calculate the agriculture residue and efficiency factors 20, 30, and 40% would generate around 7623.29, 11435.13, and 14389.22 MW of power potential, respectively. Straw, stalk, and husk generate the most power in all scenarios when compared to other residues.

When the efficiency factor is at its minimum value (20%), the power potential of straw, stalk and husk residue reachs 3429.11, 1981.59 and 833.75 MW, respectively. The gradual increase in conversion factor will significantly increase power generation. Hence, the efficiency factor is the most crucial point. In deciding the power plant design and technology with biomass raw materials.

Forest residue energy and power potential

Nearly, 50% of the covered land area in Indonesia is forest, which means the total forest production around 40 million tonnes in 2020 (Statistics Indonesia, 2021). It has a great opportunity to create a sustainable bioenergy program from the primary residue in harvesting and extraction of logging activities, and timber manufacturing residue as secondary residue sources. From 2011-2019, the forest residue generated over 7.5 million tonnes of logging residue and 0.8 million tonnes of timber processing. Those can generate an energy potential of about 59 PJ and 5 PJ logging activities and wood processing. These results have a similar estimation value for the annual forest residue from prior research around 7.3 million tonnes, can produce 48 PJ of energy [START_REF] Dani | Challenges and Policy for Biomass Energy In Indonesia[END_REF]. In the recent decades, the forest residue production has reached 3.7 million tonnes, equivalent to 15.64 PJ [START_REF] Prastowo | Biomass Resource in Indonesia : Indonesia s Solid Biomass Energy Potential, in: Our Last Resource Defining Sustainable Policies and Management of Indonesia s Biomass Utilization[END_REF].

Fig. 5 illustrates the relationship between the quantity of forest residue and its energy potential in each group. In the industrial forest production sector, the total residue production of Acacia sp. reached 5.5 million tonnes. It almost generated 100% of its energy potential, equivalent to over 3400 MW per year. Whereas in the natural forest production sector, Shorea spp ranked first place with with the residue production of nearly 0.7 million tonnes, equivalent to producing 3.28 PJ of energy. In general, the quantity of wood residue is influenced by the physical properties of wood (e.g., density and moisture content and logging methods (e.g., woodcutting technique, wood fall direction and handling management). But, the environmental conditions, such as soil type, rainfall, temperature, and wind velocity, also play a significant factor in determining the quality and quantity of timber. For example, Acacia sp. is one of wood varieties that can vegetate in the infertile soil area and spread all over Indonesia due to its high environmental tolerance characteristics. The bulk of acacia (89.3%) is superior compared to eucalyptus (82.1%). The Acacia plantion generated a higher biomass density and more potential as a bioenergy source because it can be applied in various technology conversions.

Generally, timber processing residue, such as solid and sawdust, is utilized as traditional energy for cooking and heating in the households and small industries. In Indonesia, over 60% of wood processing residue is produced from chip and particle manufacturing and can generate around 0.889 PJ of energy potential, equvalent to 30 MW of power energy. Economic growth will affect the graduak increase of the wood processing residue production, for example in the fourth triwulan of 2020, chip and particle production increased 20% more than in the first triwulan, reaching 3.44 million tonnes. In the future, it is predicted that production capacity will gradually rise by approximately 10% to 30% due to management improvements to guarantee sustainability through policy, regulation, and infrastructure support.

Distribution of energy potential biomass residue

The GIS analysis is utilized to construct a geographical distribution of energy potential in each Island of Indonesia; it aims is to evaluate the feasibility of collecting and distributing the biomass residue. To construct a geographical distribution of energy potential, the zonal functional method is used by accumulating the total energy potential of agricultural and forest energy potential on each major Indonesian island with their respective attributes to map the data spatially. At the same time, the image classification of energy potential using maximum likelihood is classified into five classes (i.e., very high, above average, average, below average, and very low). The precise method for constructing a geographical distribution is shown in Appendix D.

Figs. 7 and 8 present the geographic distribution of energy potential from agricultural and forest residue. These finding describe that, Java Island has very high energy potential for its food crops and sugarcane as a plantation crop, compared to other islands. Java island is only dominated by food crops, while plantation crops are widely cultivated outside Java island.

Contrastingly, Sumatra Island has a very high energy potential for four plantation crops, except sugarcane. The most significant plantation crop production is palm oil, and the cultivation area of palm oil in Indonesia is nearly 15 million ha. Sumatera's largest cultivation area is approximately 8 million ha and generates 22.46 PJ of energy potential. While Borneo island cultivates palm oil in one-fourth of its region, it has an average energy potential of about 11.65 PJ. Overall, palm oil is only cultivated in Sumatra, Borneo, and Papua Islands, but it is not cultivated on Java Island because the environmental capacity and water resources does not allow for its cultivation activities. Given forest residue production on Java Island, grandis L.F., Meliaceae, Albizzia falcataria, Intisia bijuga, and other varieties. While, on Sumatera Island, five different types (i.e., Acacia sp., Eucalyptus sp., Shorea spp, mixed forest, and Dipterocarpus borneensis) have a very-high category of energy production. For example, Acacia sp. can produce 14.12 million tonnes of residue per year, generating nearly 32.42 PJ. There could be a huge opportunity to develop the biomass power plant due to the feedstock availability and the fact that the supplies are spread across Sumatera Island.

Fig. 9 shows that the largest production of timber manufacturing residue on Sumatera island, which is produced by chip and particles, reached 10.64 million tonnes of residue and will generate 0.13 PJ of energy. The other major timber processing products on Java Island are sawn timber, plywood, and veneer, due to the most advanced wood processing industries and the availability of facilities. In the future, it will need to improve other locations that have great productivity from biomass by enhancing the quality of their supporting infrastructure and technology to guarantee a sustainable supply chain and achieve the goals of green energy production. The utilization of food crops as energy sources has been abandoned since the last decade, similar to the traditional approach of burning the crop residue in post-harvest.

Currently, the sustainable approach being applied refers to the Sustainable Development Goal (SDG) of utilizing biomass residue as an environmentally friendly raw material. The findings of this study reveal that Indonesia has a huge potential to use agricultural and forest residue to generate electricity. This study identified that the rice residue, such as straw and husk, produces a large volume every year throughout the year, and its availability and spatial distribution are even in all regions. The government's support has issued a national energy plan that presents some points for the application of biomass energy, i.e., 1) switching 10% of the capacity of coal power plants to biomass power plants in 2025; 2) guaranteeing the availability of Crude Palm Oil (CPO) as a national biofuel; 3) promoting non-edible crops as biomass energy; 4) increasing the quality and quantity of biomass potential surveys; 5) improving the quality of institutional production and distribution of biomass energy; 6) increasing the funding of research and development; 7) setting the price standard of biomass energy; and 8) industrialization of biomass energy. This paper also elaborates on the global approach to converting the biomass residue into a biorefinery, which incorporates the concept of sustainable use of bio-based carbon. To establish the concept, the practical implications require appreciation from stakeholders throughout the value chain, from residue management, production, and market share. In this case, the main stakeholder is the farmer, who has a vital role in guaranteeing the sustainability of the raw material, while the government provides the facilities supporting it, such as policy and regulation, infrastructure, an integrated cooperation concept, and market share.

From a social-economic perspective, biomass residue as a lignocellulosic resource must be promoted by simultaneous valorization as a new paradigm in rural areas. The farmers who produce the sustainable raw materials need some education and training to change their mindset and awareness to manage the biomass residue through the collection, storing, and distributing processes before energy production in the biorefrinery. In Indonesia, reorganizing the institutional framework of the village cooperative and optimizing the farmers' group role is a basic option to be done. The technology edorsment is an easier way to generate the biofuel. One of them is the densification process to convert biomass residue to pellets or briquettes, which is suitable for application in rural areas as an electricity source to implement the "Desa Mandiri Energi" program. On a small scale, pellets can be used for residential purposes, such as fuel for pellet stoves and electricity for pellet boilers, while in the industrial sector, pellets are a fuel for heat, steam, and power generation. For example, the utilization pellet from agricultural waste can be applied in the sugarcane industry as boiler heating and electricity. In general, pellets have advantages compared to unprocessed biomass or residue, i.e., 1) high energy content, 2) high density, 3) reduced operational cost for handling, transport, and storing, and 4) simple technology production, which requires minimum maintenance (Tumuluru, 2011). To realize its purpose on a commercial scale, strengthening the residue supply chain and infrastructure, such as warehouses, harvesting machinery, pellet machine production, and transportation networking, is needed. Moreover, manufacturing pellets in large quantities requires a substantial capital cost to set up the machinery and technology. For instance, the total total investment cost to produce 6 tons per hour of pellet is nearly 2.2 million US dollars (S. [START_REF] Mani | Economics of producing fuel pellets from biomass[END_REF]. But the application of mobile pellet can be a simple solution in rural areas due to the fact that it can reduce feedstock and drying costs by removing the need to harvest expensive feedstocks in an area when cheap feedstocks are plentiful in another area [START_REF] Jacobson | A Cost Analysis of Mobile and Stationary Pellet Mills for Mitigating Wildfire Costs[END_REF]. To produce a tonne of wood pellet, 1.6 tonnes of Accacia sp. residue (trunck and branch) is needed as a raw material [START_REF] Saosee | Life Cycle Assessment of Wood Pellet Production in Thailand[END_REF], and the LHV of Accacia sp. pellet is 18.63 MJ/kg [START_REF] Duong | Emission characteristics from the combustion of Acacia Mangium in the automatic feeding pellet stove[END_REF].

According to the findings of this study, the annual production of Accacia sp. residue reached annually. Although it may be challenging to realize in the short term, it is vital to assess the potential of biomass residue as bioenergy. In more detail, the monitoring and evaluation to recognize the sustainable energy from the guarantee of supply of raw materials, design of technology and supporting facilities, such as distribution and storage facility, policy and regulation and financing facility are a few points to realize the sustainable development of the state. The information created from this study is expected to help determine the energy potential of biomass residue in other sectors, for example, agro-industry, animal husbandry, aquatic sectors, and municipal solid waste, and will also contribute to the proper strategic planning of valorization technology and model to maximize the recovery of their residual materials. Thus, several issues can be further developed to optimize the Indonesian biomass residue, viz. 1) analyzing the properties of residue due to its strong impact on the sustainability of supply chain management, 2) environmental analysis of the biomass residue potential in all activities of collection, storage, transportation, and energy conversion, 3) technical and economic analysis of technology conversion and power plant from the engineering point of view, 4) social analysis of the biomass utilization development impact for the empowerment framework. [START_REF] Singh | Energy potential through agricultural biomass using geographical information system-A case study of Punjab[END_REF] b [START_REF] Iye | Assessment of the availability of agricultural residues on a zonal basis for medium-to large-scale bioenergy production in Nigeria[END_REF] c [START_REF] Okello | Bioenergy potential of agricultural and forest residues in Uganda[END_REF] d [START_REF] Hiloidhari | Bioenergy potential from crop residue biomass in India[END_REF] e [START_REF] Chen | Renewable energy from agro-residues in China: Solid biofuels and biomass briquetting technology[END_REF] f (Avcıoğlu et al.,

Fig. 1 .

 1 Fig. 1. Indonesian spatial data of the land use in 2018

Fig. 3 .Fig. 4 .

 34 Fig. 3. Residue production availability and energy potential of agricultural sectors in Indonesia, where (a) food crop and (b) plantation crop

Fig. 6

 6 Fig. 6 is the Sankey diagram of the power potential of forest residue, which illustrates that over 90% of power is generated by Accacia sp. compared to other products. The development potential of its varieties is supported by the fast harvesting cycle of around 5 or 6 years. It needs the stakeholders' awareness and support to guarantee the availability of feedstock for bioenergy purposes.

Fig. 5 .Fig. 6 .

 56 Fig. 5. Residue production availability and energy potential of forest sectors in Indonesia, where (a) industrial forest production, (b) natural forest production, and (c) timber processing

Fig. 7 .Fig. 8 .Fig. 9 .

 789 Fig. 7. Geographical distribution of energy potential from agriculture residue in Indonesia, where (a) food crop and (b) plantation crop distribution

Energy transformation analysis Indonesian energy supply Sustainable development goals as

  3,48 million tonnes, pellets were produced at a rate of 2,17 million tonnes per year, and an energy potential of approximately 64.8 PJ, equivalent to 449.9 MW of electricity power potential, was generated. While annual rice straw pellet production has a potential energy potential of 552.31 PJ, which is equivalent to 5753,24 MW of electrical power. It is assumed that the densification rice straw pellet method requires no additional water to produce 88.1% of yield and the LHV is 10.1 MJ/kg(Ishii and Furuichi, 2014). Considering the potential of agricultural and forest residue, the energy conversion facilities' development is necessary to increase the efficiency of production of the residue pellets by observing the analysis of social, economic, and environmental factors.In correlation to environmental issues, the Indonesian commitment to reduce GHG emissions by 26% in 2020 and 29% in 2030 amounts to approximately 314 million tonnes of CO2, which means the energy sector has been able to reduce nearly 64.4 million tonnes of CO2 in 2020[START_REF] Dirjen | Laporan Kinerja Dirjen Energi Baru Terbarukan dan Konversi Energi[END_REF]. While its value is far from the target in 2030, as the results of the scenarios prepared to achieve the goals, i.e., 1) optimalization of renewable energy application straw and husk from the agriculture sector and logging residue from Acacia sp. crops, considering they have been cultivated in all Indonesia locations. Java Island is the most productive to produce the main agriculture plant except palm oil, while Sumatra island is a more excellent producer of a few wood varieties such as Acacia sp., Eucalyptus, and mixed forest types. However, the unproductive area can be used support the raw material supply to guarantee sustainable bioenergy production.

	Energy security	Food security
	Indonesian biomass analysis
	Policy and regulation The annual energy potential from agriculture, forest, and timber processing residues Crop cultivation Cultivated area Land-use Biomass properties
	generated can reach 2822.29, 98.34, and 18.58 MW of fluidised bed combustion and generating
	turbine (C/GT) technology and 4181.17, 145.69, and 27.50 MW of combined cycle of gas and
	Biomass residue energy analysis
	steam (C/GC) technology, respectively. Those could cover around 28% and 39% of the
	Biomass residue estimation Indonesian electrical supply in 2019 (about 10565.92 GW). When it was applied to replace coal Biomass residue energy potential Biomass residue power potential
	in power plants with biomass residue, the current consumption could save more than 38%
	of 10.1 million tonnes of CO2; 2) energy efficiency of 16.7 million tonnes of CO2; 3) low-carbon Electricity demand Power plant capacity
	fuel transition of 9.56 million tonnes of CO2; and 4) post-mining reclamation of 0.38 million
	tonnes of CO2 . In the case of biomass energy acceleration, the two methods to contribute to
	environmental sustainability are: 1) optimalization of degraded lands to produce energy crops
	from non-edible plants; and 2) optimalization of integration residue to produce bioenergy. At present, a great hope is pinned on the synergy of food and energy security being grown jointly Fossil fuel (coal, oil, and natural gas) Biomass energy
	to realize environmental sustainability. The general concept of future perspective is illustrated
	10.
	Greenhouse gasses emissions
	Fig. 10. Future prespective of biomass residue in Indonesia
	6. Conclusions
	The proposed method simply assessing the biomass potential of the agriculture and forest
	sectors. According to Indonesia's geography, it has abundant diversity and is also supported
	by climate and environmental conditions. It has affected biomass residue production, as a

large quantity is created. The study estimated that agriculture and forest residue production is approximately 155.27 and 7.85 million tonnes of dry mass per year, respectively. The analysis shows that the highest share of energy potential is generated from rice residues such

estimation from crop residues and livestock manures. Biomass and Bioenergy 144, 105914. https://doi.org/10.1016/j.biombioe.2020.105914 Warner, E., Inman, D., Kunstman, B., Bush, B., Vimmerstedt, L., Peterson, S., Macknick, J., Zhang, Y., 2013. Modeling biofuel expansion effects on land use change dynamics. Environ. Res. Lett. 8, 015003. https://doi.org/10.1088/1748-9326/8/1/015003 Widiyanto, R.P.K., Kariyasa, K., Susanti, A.A., Akbar, 2019. Outloook Kelapa Sawit, Buku Outlook Seri Komoditas Perkebunan. Pusat Data dan Sistem Informasi Pertanian Sekretariat Jenderal, Kementerian Pertanian, Jakarta. Yıldız, İ., 2018. 1.12 Fossil Fuels, in: Comprehensive Energy Systems. Elsevier, pp. 521-567. https://doi.org/10.1016/B978-0-12-809597-3.00111-5

Availability

Factor (%) ** Availability Factor (%) **

Appendix

The resources of Indonesian biomass residue can be grouped into five, i.e., forest residue, agriculture residue, animal residue, aquatic residue, and urban waste. In this study, two groups of biomass residue will be thoroughly analyzed, i.e., forest and agriculture residue.