Jajang Supriatna

Mieke Rochimi Setiawati

Rija Sudirja

Cucu Suherman

Xavier Bonneau

Composting for a More Sustainable Palm Oil Waste Management: A Systematic Literature Review

Palm oil production has increased signifcantly, specifcally in Indonesia and Malaysia. However, this growth has raised environmental concerns due to the high discharge of empty fruit bunches, palm oil mill efuents, and other solid wastes. Terefore, this study aims to examine the treatment of palm oil waste by composting and systematically review insights into its application through a systematic literature review approach. Among the 1155 articles, a total of 135 were selected for a systematic review of palm oil waste management developments and their applications, while 14 were used for determining compost quality according to the criteria and requirements established in the systematic literature review. Moreover, using Egger's test, JAMOVI 1.6.23 software was used to analyze random efects models with 95% confdence intervals and publication bias. Te results showed that palm oil waste was optimally treated by composting, which is considered as a sustainable technology for protecting the environment, human safety, and economic value. Te in-vessel method with a controlled composting chamber is the best system with a minimum time of 14 days. However, it requires tight control and provides a fnal product with a high microbial colony form outdoors and indoors compared to the windrow system. Tis study is useful to see the bias of research results and helps to fnd new studies that need to be developed, especially in this case related to the management of palm oil waste into organic compost fertilizer and its application methods in the feld. It is suggested that applying palm oil waste or compost is mainly performed by mulching. In contrast, new challenges for better processing to produce organic fertilizers and applicable technologies for sustainable waste management are recommended. Te method must be afordable, efcient, and practical, combining compost quality with maximum nutrient recovery.

Introduction

Indonesia and Malaysia represent over 80% of the world's palm oil production [START_REF]Growth in industrial uses of palm oil exceeds food uses. Oil seeds: World markets and trade[END_REF]. Meanwhile, processing one ton of fresh fruit bunches (FFBs) will produce waste in the form of empty fruit bunches (EFBs) up to 0.20-0.23 ton, mesocarp fber 0.12-0.13 ton, palm kernel shell 0.05-0.06 ton, boiler ash 0.005-0.006 ton, and palm oil mill efuent (POME) 0.77-0.84 m 3 [START_REF] Harihastuti | Potensi airlimbah industri kelapa sawit (CPO) sebagai sumber bioenergi terbarukan[END_REF]. Tese amounts of untreated solid wastes potentially cause environmental problems and might reduce the competitiveness and productivity of the palm oil industry in Indonesia [START_REF] Richo | Pengaruh produktivitas lahan dan nilai tambah terhadap daya saing komoditas minyak kelapa sawit Indonesia[END_REF]. When the waste is not sustainably managed, it leads to land, air, and water pollution [START_REF] Park | Te past, present, and future trends of biosorption[END_REF][START_REF] Vijayaraghavan | Bacterial biosorbents and biosorption[END_REF]. For example, EFB takes a long time to degrade, and POME harms the environment by polluting groundwater and reducing soil fertility. However, if treated and managed properly, they could be a valuable resource and value-added product [START_REF] Vakili | A Review on Composting of Palm Biomass[END_REF].

EFB contains several nutrients and organic matter that provide fertility to the soil and can help meet nutritional needs. A research study shows that [START_REF] Baharuddin | Cocomposting of empty fruit bunches and partially treated palm oil[END_REF] the nutritional content of N, P, K, and Mg in EFB with shredded pretreatment were 0.90%, 0.60%, 2.40%, and 0.60%, respectively. Meanwhile, when press-shredded pretreatment was carried out [START_REF] Baharuddin | Cocomposting of empty fruit bunches and partially treated palm oil[END_REF], the nutritional content was 0.80%, 0.08%, 2.01%, and 0.12%, which were generally lower for the potential contents of N, P, K, and Mg. Recycling organic materials such as EFB and factory and mill waste in solid form can reduce the use of chemical fertilizers. Consequently, the application of 40-60 tons of EFB ha -1 year -1 is highly recommended to increase organic matter and fertility in less fertile soils [START_REF] Khatun | Sustainable oil palm industry: the possibilities[END_REF].

As for POME, it also contains relatively high nutrients, especially for K of 4173 ppm and 3193 ppm, which come from POME leachate and post biogas, respectively [START_REF] Baron | Waste Reduction and Nutrient Recovery during the Co-Composting of Empty Fruit Bunches and Palm Oil Mill Efuent[END_REF], with POME pH values of 8 and 7.5, respectively, in contrast to fresh POME with a relatively acidic pH (4.33), with a relatively low K nutrient content of 446 ppm [START_REF] Baharuddin | Efects of Palm Oil Mill Efuent (POME) Anaerobic Sludge from 500 m 3 of Closed Anaerobic Methane Digested Tank on Pressed-Shredded Empty Fruit Bunch (EFB) Composting Process[END_REF]. Composting is a waste management method that can treat solid (EFB) and liquid (POME) waste. For example, composting can convert EFB into valuable products for plant growth [START_REF] Aini | Pengaruh bioaktivator selulolitik untuk mempercepat pengomposan tandan kosong kelapa sawit (elaeis guineensis jacq) infuence of cellulolytic bioactivator to accelerate composting of oil palm empty bunches (elaeis guineensis jacq)[END_REF]. Composting is a complex biological transformation of organic matter carried out under controlled environmental conditions by a succession of microbial communities [START_REF] Soepena | A Control Strategy for Basal Stem Rot (Ganoderma) on Oil Palm[END_REF][START_REF] Schuchardt | Production of Compost from EFB of Palm Oil Mill Solid Wastes[END_REF]. Tere are two processes in composting, namely, aerobic and anaerobic. Composting with an aerobic system is easier to implement, and when applied correctly, it potentially reduces the volume of solid waste. Tis method requires sufcient oxygen supply into the solid waste pile. In contrast, the anaerobic system method tends to be more challenging to implement, but methane production is easier to control and utilize [START_REF] Tchobanoglous | Integrated Solid Waste Management: Engineering Principles and Management Issues[END_REF].

Furthermore, composting is divided into three main stages based on temperature parameters, namely, mesophilic, thermophilic, and ripening [START_REF] Ayed | Microbial C and N dynamics during composting process of urban solid waste[END_REF][START_REF] Hassen | Microbial characterization during composting of municipal solid waste[END_REF]. During the mesophilic phase, temperature and water content increase as a signal of a rise in psychrophilic and mesophilic microorganisms that improve the biodegradation of organic compounds and takes 20 to 30 days with temperatures above 45 °C to reach the maximum peak [START_REF] Ayed | Microbial C and N dynamics during composting process of urban solid waste[END_REF][START_REF] Hassen | Microbial characterization during composting of municipal solid waste[END_REF]. Meanwhile, the thermophilic phase occurs between 30 and 100 days [START_REF] Ayed | Microbial C and N dynamics during composting process of urban solid waste[END_REF][START_REF] Hassen | Microbial characterization during composting of municipal solid waste[END_REF] with an increase in microorganisms and as a sanitation phase in the composting process with a temperature that must be maintained from 55 to 65 °C. Te fnal phase, namely, ripening/stabilization, is the process of decreasing temperature to 30 °C, which occurs after 12 weeks. Tis decrease is caused by the depletion of organic compounds in the compost, thereby making the C/N ratio potentially stable. Te fnal product or compost can be used for agricultural activities.

Data of previous studies assist in determining the best steps in palm oil waste management based on the development of methods, systems, and their application. Tis study aims to analyze developments in the process of palm oil waste management and its application technology in the feld.

Materials and Methods

Data were initially obtained from the journal published globally from 2000 to 2021 and analyzed according to predetermined topics and from collections using integrated sources such as Scopus, Google Scholar, and PubMed. Te keywords used were focused on composting palm oil waste with the queries of composting palm oil, waste treatment, compost empty fruit bunch, waste management, composting process, organic fertilizer, biofertilizer, palm oil mill efuent (POME), solid waste, anaerobic digestion, biodegradation, co-composting, fertilizer application, efuent treatment, and empty fruit bunches (EFB).

We used the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) method to study with a systematic review [START_REF] Page | Te PRISMA 2020 statement: an updated guideline for reporting systematic reviews[END_REF], which is described in Figure 1. Subsequently, relevant abstracts were selected according to the predetermined requirements. We collected 869 articles, with an extensive selection of 135 articles and an intensive selection of 21 articles.

Articles were selected intensively with the following criteria: (i) the article must focus on the topic of compost from waste produced by palm oil, including EFB, POME, and other solid wastes; (ii) the article must contain experiments with a good statistical design and analysis; (iii) the results must contain variables such as composting time, humidity, temperature, pH, C-organic, N-total, C/N ratio, and metal components. Te materials and methods section should be detailed enough that all procedures can be repeated. If several methods are described, it may be divided into heading subsections.

Te article database was analyzed using the statistical software, namely, JAMOVI 1.6.23 [18] because it can use one of the raw data tabulated or the efect-sized value to obtain the standardised mean diference (SMD), heterogeneity, and publication bias information using the Egger test [START_REF] Egger | Bias in meta-analysis detected by a simple, graphical test[END_REF].

Results and Discussion

Defnition of Compost.

Compost is produced from the biological decomposition of fresh organic matter with the assistance of decomposing organisms. Plant or animal waste and microorganism residues in the form of bacteria, fungi, and algae are potential sources of organic matter for the soil because of their essential role in improving the physical, chemical, and biological properties [START_REF] Anwar | Evaluasi Kinerja Komposter Menara Pada Pengomposan Tandan Kosong Kelapa Sawit (TKKS) Menggunakan Pupuk Cair Organik Aktif Dari Limbah Cair Pabrik Kelapa Sawit (LCPKS)[END_REF]. Table 1 presents the various defnitions of composting based on several opinions from books and articles.

Development of Palm Oil Waste Management.

Te traditional method of processing EFB is burning and utilizing the ashes by spreading them in the feld as organic fertilizer. However, due to air pollution caused by the emission of CO Compost defnition Reference Composting is the controlled biological decomposition of organic waste into humus. It is also known as the bioconversion of organic waste substrates into stable end products (compost) [START_REF] Molla | A potential resource for bioconversion of domestic wastewater sludge[END_REF] Composting is a solid phase of aerobic biodegradation through a natural heating process of organic matter under controlled conditions that distinguishes it from ordinary decay [START_REF] Ryckeboer | A survey of bacteria and fungi occurring during composting and self-heating processes[END_REF] Composting is a viable way to convert various organic wastes into products that can be safely used as biofertilizers and soil conditioners [START_REF] Oviasogie | Oil Palm Composted Biomass: A Review of the Preparation, Utilization, Handling and Storage[END_REF] Compost is the fnal product of decomposed organic plant and animal waste [START_REF] Mclaughlin | Te Complete Idiot's Guide to Composting[END_REF] Composting is the biological decomposition of organic matter under aerobic conditions [START_REF] Epstein | Industrial Composting: Environmental Engineering and Facilities Management[END_REF] Composting is the biological decomposition and stabilization of organic substrates when a thermophilic process occurs due to a naturally generated heat to produce a stable fnal product that is free from pathogenic bacteria and can be applied to agricultural land [START_REF] Singh | Assessment of bioavailability and leachability of heavy metals during rotary drum composting of green waste (water hyacinth)[END_REF] Composting is a viable way to convert various organic wastes into products that can be safely used as biofertilizers and soil conditioners [START_REF] Cummings | Te Organic Composting: Techniques for a Healthy[END_REF] Composting is a biological decomposition and stabilization of organic waste that occurs naturally [START_REF] Oppliger | Environmental mycology in public health: fungi and mycotoxins risk assessment and management[END_REF] Composting is the process of breaking down organic matter through the process of decomposition and digestion in an oxygen-rich (aerobic) environment [START_REF] Baird | Composting toilets: a guide to options, design, installation, and use[END_REF] more efcient combustion. Moreover, using EFB for power generation requires costly preprocessing [START_REF] Samiran | Progress in biomass gasifcation techniquewith focus on Malaysian palm biomass for syngas production[END_REF].

A more practical approach is to use EFB for organic mulching in palm oil plantations because of the large quantity produced. Processing one ton of FFB can produce 230-250 kg of EFB, 130-150 kg of fber, and 60-65 kg of shell waste [START_REF] Harihastuti | Potensi airlimbah industri kelapa sawit (CPO) sebagai sumber bioenergi terbarukan[END_REF].

EFB can be composted to reduce volume and facilitate the application in plantations, thereby reducing costs. Te compost can reduce volume in high amounts by up to 85% of the initial value [START_REF] Salètes | Lignocellulose composting: case study on monitoring oil palm residuals[END_REF]. In addition, composted EFB can increase soil C: N ratio and release benefcial micronutrients when applied to plantations as fertilizer [START_REF] Siddiquee | Efective composting of empty fruit bunches using potential trichoderma strains[END_REF]. Composting can be improved with a mixture of liquid waste of palm oil [START_REF] Mohammad | Efective Composting of Oil Palm Industrial Waste by Filamentous Fungi: A Review[END_REF], decanter cake [START_REF] Yahya | Efect of adding palm oil mill decanter cake slurry with regular turning operation on the composting process and quality of compost from oil palm empty fruit bunches[END_REF], and animal manure, including chicken, cow, and goat dung [START_REF] Tambirajah | Microbiological and biochemical changes during the composting of oil palm empty-fruit-bunches. Efect of nitrogen supplementation on the substrate[END_REF]. In general, it is a biological process that takes 2-3 months to complete, and a proper control of microbial activity is necessary to produce highquality compost. Composting is also considered as a sustainable technology because it aims to preserve the environment and provide economic value by reducing chemical fertilizers that can cause land degradation [START_REF] Saputra | Study of Salicylic Acid Concentration in Suppressing the Development of Ganoderma Spp. Causes of Stem Rot Disease in Vitro and its Efect on Oil Palm Seedling Growth[END_REF].

Solid biomass waste generated by the factory contains lignocellulosic components, including large amounts of cellulose, hemicellulose, and lignin [START_REF] Chan | Bio-oil production from oil palm biomass via subcritical and supercritical hydrothermal liquefaction[END_REF]. Various technologies have converted solid waste biomass in palm oil mills into value-added products. Tis waste can be converted into bio-oil and biochar through pyrolysis, which is the thermal decomposition of lignocellulosic biomass, such as palm oil, into gaseous and liquid fuels in the absence of oxygen [START_REF] Onoja | Oil palm (Elaeis guineensis) biomass in Malaysia: the present and future prospects[END_REF]. Tis process usually occurs at a temperature of 400-600 °C, and palm oil biomass pyrolysis products can be condensed into organic liquids such as bio-oil, noncondensable gas including CO, CO 2 , and hydrogen, and CH 4, as well as biochar. Tese products highly depend on the process conditions and the biomass content of cellulose, hemicellulose, and lignin. Generally, there are two types of pyrolysis: fast and slow. According to Kong et al., fast pyrolysis produces bio-oil (70%), biochar (15%), and noncondensable gas (13%). Palm oil mill produces the highest amount of biooil usage among solid biomass waste compared to EFB and PPF (palm pressed fber) due to the signifcantly higher amount of lignin [START_REF] Saputra | Study of Salicylic Acid Concentration in Suppressing the Development of Ganoderma Spp. Causes of Stem Rot Disease in Vitro and its Efect on Oil Palm Seedling Growth[END_REF][START_REF] Onoja | Oil palm (Elaeis guineensis) biomass in Malaysia: the present and future prospects[END_REF]. Meanwhile, the highest amount of biochar can be produced when the biomass is decomposed by slow pyrolysis.

Te palm oil mill waste emits a pungent odor due to the decay of the organic matter, and one of the alternative physical treatments is fotation. It aims to remove/reduce the particles in the waste water by foating the oil or fat, thereby reducing the content in the palm oil mill waste. According to Ref. [START_REF] Maulinda | Pengolahan awal limbah cair pabrik minyak kelapa sawit secara fsika[END_REF], the fotation process of POME is very efective as a physical treatment to reduce fat or oil content, COD (chemical oxygen demand), MLSS (mixed liquor suspended solid), and MLVSS (mixed liquor volatile suspended solid) contained in palm oil mill efuent. It implies that the longer the time of the liquid in the fotation equipment, the higher the reduction [START_REF] Maulinda | Pengolahan awal limbah cair pabrik minyak kelapa sawit secara fsika[END_REF].

Several examples of solid waste biomass, such as EFB, are processed into fbers for making paper. Te paper quality obtained from EFB pulp is comparable to that of kraft hardwood [START_REF] Singh | Using biomass residues from oil palm industry as a raw material for pulp and paper industry: potential benefts and threat to the environment[END_REF], while the bubble slurry produced is suitable for making corrugated paper and cardboard [START_REF] Daud | Oil Palm Fibers as Papermaking Material: Potentials and Challenges[END_REF]. Furthermore, EFB and palm fber are used as fllers to reinforce polymer composites using melt blends and hot-press molding techniques. EFB can also be processed into fber materials and used in the manufacture of fberboard as well as medium-density fber (MDF). Other products are coir and board fber, cement, board, roof tile, and wood paper [START_REF] Prasertsan | Biomass residues from palm oil mills in Tailand: an overview on quantity and potential usage[END_REF]. Recently, the isolation of cellulose nanofbers, as well as microcrystalline and nanocrystalline cellulose from EFB by acid hydrolysis, has also been demonstrated [START_REF] Fahma | Isolation, preparation, and characterization of nanofbers from oil palm empty-fruit-bunch (OPEFB)[END_REF]. Cellulose has various applications in diferent industries, such as food stabilizers, pharmaceuticals, compounds, cosmetics, and as a bio-fller in composites [START_REF] Beroual | Efect of the delignifcation process on the physicochemical properties and thermal stability of microcrystalline cellulose extracted from date palm fronds[END_REF]. Palm fber contains 5% to 6% dry residual oil after CPO extraction, while the remaining oil comprises natural carotenes ranging from 4000-6000 ppm, vitamin E 2400-3500 ppm, sterols 4500-8500 ppm, and coenzyme Q10 1000-1500 ppm [START_REF] Neoh | Utilization of agro-industrial residues from palm oil industry for production of lignocellulolytic enzymes by curvularia clavata[END_REF]. Most of these bioactive compounds reportedly have superior antioxidant and anticancer properties. Hence, they can reduce the risk of heartrelated diseases in humans. Besides, eforts have been made to recover residual oil from palm fber using solvent and supercritical fuid extraction [START_REF] Yuhazri | Solid Fuel from Empty Fruit Bunch Fiber and Waste Papers PART 3: Ash Content from Combustion Test[END_REF]. In Table 2, we can see the development of palm oil waste management summarised by some references.

Composting Process of Palm Oil Waste.

Te composting process can be divided into two stages, namely, active and ripening. During the early stages, mesophilic microbes will immediately utilize oxygen and easily degraded compounds, which are then replaced by the thermophilic. Subsequently, the temperature of the compost heap increases rapidly, followed by a rise in pH until it reaches 60 °C. Te temperature will remain high at 40 °C during the ripening phase [START_REF] Yulianto | Bioadsorption of modifed empty fruit bunch palm oil for reducing its 3-MCPD compounds using response surface methodology[END_REF], while the mesophilic microbes are then replaced by the thermophilic ones active at high temperatures. During the active decomposition of organic matter, the microbes in the compost will decompose the substrate into NH 4 + , CO, steam, and heat through the metabolic system with the assistance of oxygen, and the temperature reduces to the initial value. Te next phase is the compost's ripening, leading to further humic complexes' formation. During the composting process, a decrease in the volume and biomass of the material occurs. Tis reduction can reach 30% to 50% of the initial weight, depending on the moisture content [START_REF] Yulianto | Bioadsorption of modifed empty fruit bunch palm oil for reducing its 3-MCPD compounds using response surface methodology[END_REF].

Microorganisms play an essential role in the composting process because the stability and maturity of compost depend on the microbial activity [START_REF] Hirzel | Compost tea efects on production and extraction of nitrogen in ryegrass cultivated on soil amended with commercial compost[END_REF]. Tey can degrade and change constituents in the substrate, especially local types such as fungi that are useful in converting organic waste into compost [START_REF] Estrella-González | Enzymatic profles associated with the evolution of the lignocellulosic fraction during industrial-scale composting of anthropogenic waste: comparative analysis[END_REF]. Meanwhile, fungi degrade substrates containing lignin into simpler components because they have an efcient extracellular enzyme performance system, including hydrolytic and ligninolytic. Both systems produce cellulase, hemicellulase, and ligninase to degrade polysaccharides, lignin, and an open phenyl ring [START_REF] Gutiérrez | Process integration possibilities for biodiesel production from palm oil using ethanol obtained from lignocellulosic residues of oil palm industry[END_REF]. Several studies also stated that using rich N substances, such as palm 4

Te Scientifc World Journal

Results

Liquid waste Organic liquid fertilizer (fermentation using the EM4 activator)

Decreased COD from 2.362 mg/l to 1.580 mg/l and some of the organic matter was converted into new bacterial cells. Te resulting product contains nutrients similar to organic fertilizers [START_REF] Irvan | Kajian awal pembuatan pupuk cair organik dari efuent pengolahan lanjut limbah cair pabrik kelapa sawit (lcpks) skala pilot[END_REF] EFB Compost Te compost produced had the characteristics of pH 9, moisture content 57.24%, water holding capacity 76%, C/N ratio 12.5%, P 0.58%, and K 0.95% with a composting period of 40 days [START_REF] Trisakti | Efect of turning frequency on composting of empty fruit bunches mixed with activated liquid organic fertilizer[END_REF] EFB Compost (mixture using palm oil mill efuent)

Compost nutrition is similar to other studies. In-vessel systems such as rotating drum composters are the systems with the fastest degradation of EFB -liquid waste of palm oil substrates [START_REF] Zahrim | Production of non shredded empty fruit bunch semi-compost[END_REF] EFB Compost (the addition of mud to the decanter and chicken manure)

Compost produced by standard nutrition [START_REF] Kananam | Biochemical changes during oil palm (Elaeis guineensis) empty fruit bunches composting with decanter sludge and chicken manure[END_REF] EFB Compost (mixture of palm oil mill efuent and earthworm Eisenia fetida) Good compost content on vermicompost is EFB with the addition of liquid waste of palm oil (50% EFB + 50% liquid waste of palm oil) [START_REF] Nahrul Hayawin | Vermicomposting of empty fruit bunch with addition of palm oil mill efuent solid[END_REF] EFB Compost (the addition of palm oil mill efuent anaerobic sludge)

Anaerobic liquid waste of palm oil. Anaerobic accelerates the composting period in 40 days with a C/N ratio of 12.4 [START_REF] Alibolandi | High level expression of human basic fbroblast growth factor in Escherichia coli: evaluating the efect of the GC content and rare codons within the frst 13 codons[END_REF] Bunch fber cell (i) Nucleus plantation fertilizer (mulching) 100% EFB is used for land applications, and 100% fber is used as fuel in the boiler. Refusing and reducing the system can save costs and increase company revenue [START_REF] Daulay | Analisis strategi manajemen pengolahan limbah padat di pabrik pengolahan kelapa sawit PT. Perkebunan nusantara VII unit talo pino kecamatan pring baru kabupaten seluma[END_REF] (ii) Plasma plantation fertilizer (mulching) (iii) Partnership plantation fertilizer (mulching) (iv) Community plantation fertilizer (mulching) (v) Boiler energy (vi) Boiler surplus (vii) Dryer fuel

Liquid waste Land application

Applying the thermophilic system to the anaerobic reactor unit might increase the decomposition of bacteria, thereby making the processing more efcient [START_REF] Rahardjo | Studi banding teknologi pengolahan limbah cair pabrik kelapa sawit[END_REF] Liquid waste Biogas production (pilot-scale closed pond system with semi and continuous feeding) Te liquid waste of palm oil processing was stable at an organic loading rate of 0.9-3.11 kg/m 3 /day with a COD reduction percentage of more than 90% and a maximum biogas production of 2.59 m 3 /day [START_REF] Shintawati | Karakteristik pengolahan limbah cair pabrik minyak kelapa sawit dalam bioreaktor cigar semi kontinu characteristic of palm oil mill waste water treatment using semicontinue anaerobic cigar bioreactor[END_REF] Liquid waste Reduce odor (fotation system) Flotation of palm oil's liquid waste efectively reduces fat/oil content, COD, MLSS, and MLVSS. Te longer the period of residence of the liquid in the fotation, the higher the decrease [START_REF] Maulinda | Pengolahan awal limbah cair pabrik minyak kelapa sawit secara fsika[END_REF] Te Scientifc World Journal oil mill efuent, cow or poultry dung, and rice husks, is one solution to increase the efectiveness of composting with EFB materials [START_REF] Tambirajah | Microbiological and biochemical changes during the composting of oil palm empty-fruit-bunches. Efect of nitrogen supplementation on the substrate[END_REF]. Other factors such as pH, humidity, and residual oil content can afect the natural composting process because they potentially interfere with the growth of fungi that act as composters.

In principle, composting is a method used to reduce the C/N ratio of the organic matter until it is equal to the level of the soil, namely, <20 or a � 10. It is because organic matter has a relatively high C/N ratio ranging from 58 to 60 [60]. It indicates that the higher the ratio, the longer the composting process or organic matter overhaul. Te decomposition process in composting occurs under both aerobic and anaerobic conditions, as demonstrated in equation ( 1) in the following reaction [START_REF] Michel | Summer perspectives[END_REF]:

Organic compound + O 2 aerobic microbes N, P, K ≫ H 2 O + CO 2 + nutrient + humus, (1)

Composting Method Development.

Te appropriate method for a given composting application is determined by a variety of factors, including location, scale of operation, the consequences of occasional odors, access to capital, the nature of the feedstocks, environmental regulations, labor availability, and business objectives. Many composting facilities use simple methods such as passively aerated static piles and turned windrows. Tese methods are popular because they require minimal site modifcation, engineering, and capital investment. Another simple, widely used method with numerous applications is aerated static pile composting (ASP). Some composting operations have implemented advanced technology and automation methods to produce compost faster, save space, provide shelter from the elements, or reduce odors where sensitive neighbors are nearby. Several criteria can be used to label and categorize composting methods, including the mode of aeration (passive vs forced), the level of containment (open, covered, contained, or in-vessel), the degree of agitation (static vs turned), and material movement (batch vs continuous).

Table 3 summarises the comparison between the windrow-based and CECC (control environment composting chamber) systems on composting. In in-vessel anaerobic composting with CECC, EFB waste from palm oil mills will be chopped to the specifed size in precomposting and mixed with liquid waste and ash from combustion. Te resulting biomass mixture is then transferred by the frontend loader to the CECC and stacked into customized piles 2 meters high, 6 meters wide, and 25 meters long along the tunnel. Once flled, the tunnel will be closed and blown through a computer system to ensure the optimal conditions for the composting process according to the specifed batch processing temperature. Te composting process is activated using a specially formulated mixture of microorganisms mixed with a liquid waste of palm oil and sprayed onto the compost pile. Te computer control system will allow the composting to be completed within two weeks with reasonable control of the oxygen level in the biomass as well as the temperature and humidity levels. At high temperatures in the composting process, a certain amount of liquid waste of oil palm is sprayed onto the compost and evaporated to maintain the optimum temperature of a humid level. After two weeks, the compost will be removed from the front-end loader from the vessel and ripened in a pile for further 14 days for preservation and cooling down.

Te efectiveness of the compost in the presence of a high consistency of microbial CFU (colony forming unit) is very benefcial because it allows us to see performance signs on soil conditions, plant health, and increase in yield compared to unfortifed compost produced from windrow composting mechanisms. In an environment that is not controlled by the typical windrow composting process, the composting period varies from 45 to 60 days.

Compost Quality Standard.

Te success of essential compost can be seen in the temperature parameters indicated by the mesophilic (20-40 °C), thermophilic (40-60 °C), and maturity (30-35 °C) phases of compost with an aerobic system [START_REF] Hassen | Microbial characterization during composting of municipal solid waste[END_REF]. Te results of the review showed a change in temperature from the initial phase of about 28 °C to the peak phase of about 60 °C and the maturity phase to 30 °C of soil temperature. Te thermophilic phase will be active at high temperatures to degrade hemicellulose, cellulose, lignocellulose, lignin, and lipids [START_REF] Lim | A potential bioconversion of empty fruit bunches into organic fertilizer using Eudrilus eugeniae[END_REF]. EFB is a high-fber material consisting of 44.2% cellulose, 33.5% hemicellulose, and 20.4% lignin [START_REF] Aziz | Preparation of Cellulose from Oil Palm Empty Fruit Bunches via Ethanol Digestion: Efect of Acid and Alkali Catalysts[END_REF]. Composting is a process of decreasing organic C/N on the substrate. Te high C/N ratio in compost can be caused by high holocellulose, alpha-cellulose, and lignin in organic materials used as raw materials for compost [START_REF] Sakiah | Sifat Biologi Tanah Pada Lahan Aplikasi dan Tanpa Aplikasi Tandan Kosong Kelapa Sawit di Adolina PT[END_REF]. Te C/N ratio is an important factor that can afect the process conditions regarding nutrients in microbes during composting and compost as a fnal product. Te EFB composted with several other waste materials contains relatively high nitrogen and carbon, such as poultry manure, goat manure, cow manure, and palm oil mill efuent [START_REF] Zainudin | Indigenous cellulolytic and hemicellulolytic bacteria enhanced rapid co-composting of lignocellulose oil palm empty fruit bunch with palm oil mill efuent anaerobic sludge[END_REF].

Te data from the review showed that the temperature changes during the composting process are divided into the mesophilic, peak/thermophilic, and cooling/maturation phases. Te mesophilic is the initial phase of composting, and it involves a temperature range of 28 °C. In comparison, the activity of local microorganisms increases in the thermophilic phase at 60 °C, which is the peak phase in the degradation of organic matter. Furthermore, the last phase is the compost maturity of the fnal product, which occurs at the range of 25 °C soil temperature. Another critical factor in determining compost quality is the degree of acidity. Bacteria and fungi in the compost which are benefcial to soil and plants will breed at pH > 5.5. If the soil pH is very low, growth and development will be hampered [START_REF] Rosmalinda | Aplikasi limbah cair pabrik kelapa sawit dalam memperbaiki sifat kimia tanah gambut[END_REF]. Te pH in the composting process will increase from the initial acidic state to alkaline state, but Table 4 showed that the overall pH is in the range of 7.41. Tis value is classifed as neutral pH and complies with the requirements of SNI 19-7030- Te C/N ratio obtained follows the requirements, namely, 23.42. Overall, based on the average from a total of 21 articles, the compost produced from various organic materials as well as the techniques carried out in each study is still under the requirements determined by both SNI and the Regulation of the Minister of Agriculture regarding compost, as presented in Table 4.

A total of 135 articles in the data collection were generated for systematic review. However, after considering the inclusion and exclusion criteria, only 14 were used for the systematic review activities to determine compost quality. Te eight articles contain complete information on the parameters that can be used, including moisture content, pH, C-Organic, and N-total, as well as macro-and microcomponents consisting of phosphorus (P), potassium (K), calcium (Ca), sulfur (S), iron (Fe), magnesium (Mg), zinc (Zn), manganese (Mn), and copper (Cu), as presented in Table 5.

According to the articles reviewed, the composting period ranged from 30 to 150 days. However, using organic materials such as EFB mixed with the liquid waste of palm oil, containing local microorganisms, can help accelerate the decomposition of organic matter, thereby reducing the time. Te period required to reach the maturity phase of the compost takes approximately 60 days, in line with the studies presented in Table 6.

A total of 14 parameters were analyzed, 6 of which had a signifcant result on pH, C-organic, C/N ratio, and elements such as P, K, Fe, Zn, Mn, and Cu. Moreover, some parameters in the heterogeneity test had a value >48%, except K, Ca, S, and Mg.

Te bias in the basic parameters Ca, S, and Mg was caused by excessive intervention in small-sized studies with low methodological quality. Te insignifcant nature of these parameters does not mean that the results were not good. However, it showed that the expected decrease and increase in specifc parameters could provide quality following the requirements and standards set.

Microorganisms need C-organic as a source of energy in the composting process. Hence, the longer the composting time, the lower the C-organic levels. It is because the presence of C carbon is required for microbes to breed [60]. C-organic content based on compost quality standard SNI 19-7030-2004 (Indonesia) ranges from 9.8% to 32%. In addition, microorganisms in the composting process also require a certain amount of N. Te higher the total content, the faster the organic matter will decompose.

Phosphorus and potassium are the main nutritional elements/macronutrients in microbial compost. Based on the literature review, the phosphorus and potassium levels in the compost are 0.99% and 4.14%, respectively. Given that both are macrocomponents, the higher the percentage of P and K, the better the quality of the end product. Besides, nitrogen also infuences phosphorus levels, indicating that the greater the N content, the higher the P due to the multiplication of remodeling microorganisms [START_REF] Hidayati | Lignin isolation from black liquor from oil palm empty fruit bunch using acid[END_REF]. Microorganisms use potassium as a catalyst in the substrate material. Te presence of bacteria and their activities will signifcantly cause an increase in the content [START_REF] Hidayati | Lignin isolation from black liquor from oil palm empty fruit bunch using acid[END_REF]. Phosphorus plays a role in the forming of fowers and fruits. At the same time, potassium helps to develop and strengthen the tissue on the fruit stalk, thereby reducing the tendency to fall.

Calcium is another essential element for growth and makes plants less susceptible to disease and pests. However, pH strongly infuences its availability, implying that soil with low pH tends to have poor phosphorus and calcium contents [START_REF] Rosmalinda | Aplikasi limbah cair pabrik kelapa sawit dalam memperbaiki sifat kimia tanah gambut[END_REF]. Te calcium defcit is linked to a low soil pH, organic matter, and sandy soil texture. Moreover, applying palm oil liquid waste to land can increase the magnesium value [START_REF] Rosmalinda | Aplikasi limbah cair pabrik kelapa sawit dalam memperbaiki sifat kimia tanah gambut[END_REF]. Generally, roots absorb nutrients at a neutral pH quickly because they are readily soluble in water. In acid soils, toxic elements are found due to the increase in the solubility of microelements such as Fe, Mn, Zn, Cu, and Co in large quantities, which are toxic to plants. Soil pH also determines the development and population of soil microbes. Hence, bacteria and fungi benefcial to soil and plants will breed at pH > 5.5, but when the value is low, it leads to reduced growth and hampered development [START_REF] Rosmalinda | Aplikasi limbah cair pabrik kelapa sawit dalam memperbaiki sifat kimia tanah gambut[END_REF].

Mn, Zn, and Cu micronutrients are needed in the plant growth process at moderate amounts, but based on the review results, these microelements are still below the required limits, namely, 115.44 ppm, 443.18 ppm, and 52.50 ppm, respectively. Hence, they were classifed as safe. Cu is an essential nutrient for plant growth needed in low concentrations because excessive amounts cause phytotoxicity. One of the organic materials that can reduce soil phytotoxicity is organic metals' complexity [START_REF] Gupta | Use of biomass-derived biochar in wastewater treatment and power production: a promising solution for a sustainable environment[END_REF].

Due to its high afnity towards organic matter, Cu is not quickly mobilized in the composting process [START_REF] Singh | Assessment of bioavailability and leachability of heavy metals during rotary drum composting of green waste (water hyacinth)[END_REF]. During the composting of solid-liquid waste, the formation of humic substances converts Cu from the humic substances to the organic fraction [START_REF] Yu | Efects of long-term compost and fertilizer application on stability of aggregate-associated organic carbon in an intensively cultivated sandy loam soil[END_REF]. Te cellular fraction decreases with increasing humic content and reducing pH from 7.5 to 6.7 in line with the afnity of Cu for organic matter [START_REF] Kuriyama | Improved Sustainable Fractionation of Palm Oil Using Polyglycerol Fatty Acid Esters[END_REF]. Te amount of adsorbed Cu decreased with an increase in the amount of C-organic dissolved in the substrate because the metal formed a stable complex that tended to remain in the substrate (Singh & Kalamdhad). Zn is also an element that is needed in small amounts, and its mobile fraction increases during the composting process due to the oxidation of organic matter and high oxidation-reduction potential. Te formation of humate potentially converts Zn from the fraction of the humic substance to organic during the composting process [START_REF] Singh | Assessment of bioavailability and leachability of heavy metals during rotary drum composting of green waste (water hyacinth)[END_REF].

Furthermore, Mn is a nutrient needed by plants in small amounts. Te nutrient plays a critical role in synthesizing chlorophyll, a coenzyme, and acts as an activator of several respiratory enzymes in metabolic and photosynthetic reactions. A research study [START_REF] Singh | Assessment of bioavailability and leachability of heavy metals during rotary drum composting of green waste (water hyacinth)[END_REF] reported that the availability of Mn decreased during the composting with animal manure.

Other metal elements such as Ni, Pb, Cd, and Cr in the compost are defcient and not expected to be present. Te indicated heavy metal concentration was below the toxicity level, and Ni was not identifed in the compost. After 40 days, Ni < 20 ppm, and when palm oil liquid waste was added, the concentration of heavy metals decreased in the 8

Te Scientifc World Journal fnal product [START_REF] Baharuddin | Cocomposting of empty fruit bunches and partially treated palm oil[END_REF]. Te slight decrease might be related to the stabilization phase, where the moisture increased in the fnal stage.

Methods of Palm Oil Waste Application.

Several methods are related to applying palm oil waste in the regulations and provisions set by the government in its utilization. Te land application method tends to consider feld-specifc conditions consisting of eight main factors which are as follows: (i) the type and quantity of available waste, (ii) the shape of the ground surface, (iii) the soil type and groundwater depth, (iv) the area and distance from the WWTP (waste water treatment plant), (v) the distance between the area and the water source, (vi) the investment, operational, and showed the best growth and production in mustard plants [START_REF] Salahudin | Microbial fuel cell (Mfc) design for production of electric bio from palm oil industry waste[END_REF] Mulching (soil mixing of growing media) 1:2 (compost: growing media) Te addition of leaves on chili and corn plants with EFB compost was faster than urea and ordinary soil, while the weight of plants with compost was greater than urea and soil [START_REF] Jaya | Optimasi produksi pupuk kompos tandan kosong kelapa sawit (Tkks) dan aplikasinya pada tanaman[END_REF] Mulching in inceptisol soil pH 5.2 3-12 ton/ha Te administration of several doses of EFB compost showed diferent efects on the parameters of plant height, plant fresh weight, and fresh weight of plants ft for consumption. Te application of EFB compost at a dose of 9 tons/ha is the best dose for producing pakcoy plants [START_REF] Dahlan | Aplikasi beberapa dosis tricho-kompos tkks pada tanaman pakcoy (Brassica rapa L.)[END_REF] Mulching (soil mixing growing media) Te Scientifc World Journal

Methods

Dosage

Results

Randomly sampling on peat soil (soil analysis) @700 g mixed with the liquid waste of palm oil Tere was a change in composition for the pH value and mineral content of the peat soil after the application of POME with a pH value of 6. .

[67]

Biopore (palm oil mill efuent from an aerobic pool) 5; 7.5; and 10 liters of liquid waste of palm oil are provided in 1, 2, 3, and 4 biopore/plant holes, respectively Te application of POME dose of 7.5 liters in four biopores/ plant holes increased the number of midribs and leaves, leaf width and length compared to the control and the highest form of other treatments.

[98]

Mulching with the size of 1.2 × 1.4 m with plant spacing 60,70 cm. 100, 200, and 300 ml per plan Mixed crops with palm ash Te interaction of POME and ash signifcantly afected plant height and weight of fruit/plant with the best dose of giving POME 300 ml with a fruit weight of 670 g per plant.

[99]

Mulching plot size 4 × 4 m with a spacing of 20 × 40 cm) 25000, 50000, 75000, 100000, and 150000 L/ha Applying 150000 L ha -1 POME can replace dolomite lime, manure, urea fertilizer, and KCl in improving the chemical properties of ultisol soil for soybean production.

[97]

14

Te Scientifc World Journal

Methods

Dosage

Results

Mulching (three same-age plant blocks) POME and EFB as organic fertilizers Te POME application produced an FFB that was not signifcantly diferent from the EFB application although the production of the EFB block was lower than the POME block.

Te average FFB production in both blocks was already above the potential for moderate-class land production. Te POME application resulted in higher plant height, female fowers, and sex ratio than the EFB application [START_REF] Wiharja | Pengaruh aplikasi limbah cair pabrik kelapa sawit dan tandan kosong kelapa sawit terhadap produksi kelapa sawit[END_REF] Mulching (three blocks with a total of 60 samples)

POME and EFB as organic fertilizers Applying organic fertilizer had the same efect on palm oil plants' production and agronomic character. Palm oil production on land where EFB and POME were applied was still below the production potential according to the intermediate class of land production [START_REF] Setiono | Pengaruh pupuk organik tkks dan lcpks terhadap produksi tanaman kelapa sawit[END_REF] Mulching (three blocks with a total of 60 samples)

POME and EFB as organic fertilizers Each year's growth and productivity of palm oil plantations had not yet reached the production potential in the moderate-class of land suitability. POME and EFB applied the same efect on all agronomic characteristics of palm oil plant growth [START_REF] Hardiansyah | Kajian pengaruh limbah cair pks dan tandan kosong terhadap pertumbuhan dan produktivitas tanaman kelapa sawit (elaeis guineensis jacq.)[END_REF] Mulching Composition of planting media (sand soil, clay soil, and a mixture of both) with the addition of four doses of dry mud (% volume) with 10%, 20%, 30%, and 40% seeds

Tere was no excellent combination between the dosage of POME dry mud and soil type. Applying dry mud POME concentration of 10% was sufcient to produce good growth of palm oil seedlings. Te four doses gave the same efect as NPK fertilizer and urea at a dose of 0.4 g on palm oil growth [START_REF] Solichin | Pengaruh dosis lumpur kering kolam lcpks dan komposisi media tanam terhadap pertumbuhan bibit kelapa sawit di prenursery[END_REF] Te Scientifc World Journal maintenance costs, and (vii) the distance to residential areas. Meanwhile, the most common methods used in palm oil plantations are fat or long beds, furrows, sprinklers, and the tanker system. Te diferences between the methods are presented in Table 7.

Aside from developing composting technology, the following is an application review of composted EFB, POME, and other solid wastes as organic fertilizers for growth and productivity. According to several reviews, mulching is the most commonly used technique (Tables 8910).

Te solid waste application method generally uses a direct mulching system, either conventional or mechanical. Mulching is the practice of applying a layer of material to the soil surface to reduce temperature and increase pH and nutrients to improve plant growth and yield [START_REF] Moradi | Efect of four soil and water conservation practices on soil physical processes in a nonterraced oil palm plantation[END_REF]. Using EFB mulching can efectively enhance soil aggregation and water retention. Furthermore, it facilitates weed control, prevents erosion, and helps maintain soil moisture, specifcally for young palm oil [START_REF] Rahmadi | Pemanfaatan Limbah Padat Tandan Kosong Kelapa Sawit Dan Tanaman Pakis-Pakisan Untuk Produksi Kompos Menggunakan Aktivator Em-4. neliti.com[END_REF]. Mulching can improve soil fertility because it contains the elements needed to improve the quality [START_REF] Daulay | Analisis strategi manajemen pengolahan limbah padat di pabrik pengolahan kelapa sawit PT. Perkebunan nusantara VII unit talo pino kecamatan pring baru kabupaten seluma[END_REF].

Liquid waste (POME) is generally applied directly as mulching in land application systems with various doses either through pond systems or biopori. Tis application can increase soil CEC up to 9.47 cmol•kg -1 [START_REF] Rosmalinda | Aplikasi limbah cair pabrik kelapa sawit dalam memperbaiki sifat kimia tanah gambut[END_REF], improving the chemical properties of ultisol soils [START_REF] Ermadani | Pengaruh aplikasi limbah cair pabrik kelapa sawit terhadap hasil kedelai dan perubahan sifat kimia tanah ultisol efect of palm oil mill ef uent on soybean yield and chemical properties of ultisol[END_REF]. Te summary is presented in Table 9.

Te compost from co-composting EFB and POME is generally used as organic compost with a mulching application method (Table 10). Several research results show that the mulching method still does not provide consistent results on plant productivity.

Conclusions

Optimal palm oil waste management is usually carried out using composting and considered as a sustainable technology because it is aimed at environmental conservation and providing economic value. Te in-vessel method with CECC is the best system with the shortest period of 14 days. However, it requires extra management control and produces a fnal product with a high microorganism value compared to the outdoor and indoor windrow methods. Furthermore, the systematic review results on the compost quality of the 14 measured parameters, namely, humidity, pH, C-organic, N-total, and macro-and micronutrients such as P, K, S, Ca, Mg, Fe, Mn, Cu, Zn, and B which were still following the standards and requirements of compost quality in Indonesia. Te palm oil waste application has advantages and disadvantages. Te advantages include sorting from the top based on the most applied solid and liquid waste method, using a method with the furrow system, long bed, sprinkler, and tanker. Te use of solid waste for direct fertilization (EFB) and compost through a manual or mechanical mulching system is placed on the soil surface between the palms. In another method, EFB is applied after composting through mulching to supply nutrients in stock nutrition for both soil and plants to improve the quality. However, a sustainable practice needs to be studied further for a better consistent result on the yield. Based on the systematic review, we found that there are still research biases and the need for fnding new methods so that the quality of the compost produced from composting EFB and POME or other waste becomes organic fertilizer that can increase soil fertility, nutrient stock, and plant productivity sustainably [START_REF] Abnisa | Characterization of bio-oil and bio-char from pyrolysis of palm oil wastes[END_REF].

Table 3 :

 3 Comparison between windrow-based and CECC environment [62]. bio-organic fertilizer Noncompliance and low-quality compost only Partial compliance, inconsistent quality, and colony form unit Full compliance and high colony form unit calculation Te Scientifc World Journal 2004 and Minister of Agriculture No. 261/KPTS/SR.310/M/ 4/2019 (Indonesian standard).

Table 7 :

 7 Comparison of palm oil efuent methods[START_REF] Novandaharto | Pemanfaatan Limbah Industri Pabrik Minyak Kelapa Sawit Dengan Sistem Aplikasi Pada Lahan Perkebunan Kelapa Sawit[END_REF].Application methodStrengthsWeaknessesFlatbed or long bed system (i) Higher capacity compared to the furrow system (i) Investment and operational costs are more expensive than the furrow system (ii) Suitable use in sloping/relatively fat hilly areas (ii) Can damage palm oil trees if overfeeding is done (iii) Equitable distribution of waste and good soil element storage (iii) Complicates the work of harvesters compared to furrows (iv) Less soil erosion efect (iv) More pungent smell (v) Rarely clogged (vi) Low investment cost compared to sprinklers Furrow system (i) At the same volume, less area is required (i) Afected by soil erosion (ii) Cheaper investment costs compared to sprinklers and long beds (ii) Easy to clog and overfow (iii) Te potential for damaging palm oil trees is more diminutive than long beds (iii) Need control during efuent irrigation (iv) Suitable use in areas with clay or clay soil types (iv) Operating costs are higher than long beds (v) Easier to maintain (vi) Do not complicate harvesters (vii) Increase in yield/ha/year is almost the same as sprinklers and long beds (viii) Relatively less smell than a long bed Sprinkler system (i) Sufciently high waste delivery capacity (i) High investment and operational costs (ii) Can distribute liquid waste over a large area (ii) Need more maintenance (iii) Not afected by the contours of the land (iii) Pipes can be clogged and broken (iv) Not afected by soil erosion (iv) Te sprinkler can get stuck due to blockage Tanker system (i) Cheaper investment and operational costs than other systems (i) Potential for pollution outside the area is relatively high (ii) Can apply liquid waste in areas far from WWTP (ii) Lower efuent application capacity (iii) Infuenced by the condition of road and bridge infrastructure in the application area (iv) Infuenced by the season (v) Afected by the condition of the tractor/tanker (vi) Application of liquid waste at any time can be stopped entirely (vii) Easy to clog and overfow (vii) Need control during waste watering 12 Te Scientifc World Journal

Table 1 :

 1 2, open burning is discouraged and prohibited in countries such as Malaysia and Indonesia. EFB is a lousy fuel because it contains a high moisture content of approximately 60%. Hence, it is usually air-dried to reduce 40% of the content for Defnitions of composting obtained from several references.

	2

Figure 1: Procedure, criteria, inclusion, and exclusion for systematic review studies.

Table 2 :

 2 Development of palm oil waste management.

	Management	(development technology)
	Substrate	(waste type)

Table 5 :

 5 Te analysis results on physicochemical parameters and macro-and micronutrient content of palm oil waste compost.Description: N � number of samples used in the study; k � number of studies used in the analysis; SMD � standardized mean diference is a summary of each study with the efect size; p � p value; I 2 � inconsistency (heterogeneity test); Egger's � publication bias test; ns � not signifcant.

	Parameter	N	k	SMD	p	I 2 (p)	Egger′s (p)
	Physicochemical
	Moisture	75	8	-0.946 [-1.440; -0.452]	<0.001	93.40% (<0.001)	0.039
	pH	95	8	0.968 [0,520; 1.415]	<0.001	48.54% (0.015)	0.001
	C-organic	135	8	0.926 [0.572; 1.280]	<0.001	92.90% (0.003)	0.001
	N-total	135	8	2.19 [1.762; 2.616]	<0.001	93.35% (<0.001)	<0.001
	C/N ratio	120	8	0.407 [0.029; 0.785]	0.035	82.28% (<0.001)	0.001
	Macro-and microcomponents
	P	125	8	0.698 [0.321; 1.076]	<0.001	60.51% (0.118)	<0.001
	K	125	8	0.847 [0.464; 1.230]	<0.001	35.41% (0.242)	<0.001
	Ca	70	8	-57.6 [-67.191; -48.072]	<0.001	0% (0.557)	ns
	Mg	95	8	-0.212 [-0.641; 0.217]	ns	34.46% (0.267)	ns
	S	18	8	-0.33 [-1.34; 0.68]	ns	10.18% (0.355)	0.155
	Fe	24	8	0.99 [-1.32; 3.30]	ns	83.66% (0.033)	0.005
	Zn	18	8	5.64 [2.36; 8.91]	<0,001	52.94% (0.047)	0.013
	Mn	18	8	1.33 [-2.20; 4.85]	ns	88.75% (0.007)	0.008
	Cu	24	8	3.38 [0.64; 6.12]	0.016	76.45% (0.003)	<0.001

Table 4 :

 4 Comparison of review data of compost standards based on the Indonesian standards (SNI 19-7030-2004) and Minister of Agriculture (Regulation No. 261/KPTS/SR.310/M/4/2019).

	Parameter	SNI 19-7030-2004	Permentan no 261/KPTS/SR.310/M/4//2019	Review results
	C-organic (%)	9.80-32	min 15	-
	C/N ratio	10-20	≤25	23.42
	pH	6.80-7.49	4-9	7.41
	Temperature ( °C)	Groundwater temperature	-	Variation (in standard)
	Water content (%)	Max. 50	8-20	-
	Macroelements:			-
	N-total (%)	Min. 0.4	Total � Min. 2	-
	Phosphorus (%)	Min. 0.10		0.99%
	Potassium (%)	Min. 0.20		4.14%
	Heavy metal (ppm):
	As	-	Max. 10	-
	Hg	Max. 0.8	Max. 1	-
	Pb	Max. 150	Max. 50	-
	Cd	Max. 3	Max. 2	-
	Cr	Max. 210	Max. 180	-
	Co	Max. 34	-	-
	Cu	Max. 100	-	52.50 ppm
	Ni	Max. 62	Max. 50	-
	Se	Max. 2	-	-
	Microelements:
	Ca	Max. 25.50%	-	1.29%
	Mg	Max. 0.60%	-	0.7%
	Fe total	Max. 2.00%	Max. 15000 (ppm)	0.78%
	Fe available		Max. 500 (ppm)
	Mn	Max. 0.10%	-	115.44 ppm
	Zn	Max. 500 (ppm)	Max. 5000 (ppm)	442.18 ppm
	Al	Max. 2.20%	-	-

Table 8 :

 8 Review of the development of the EFB compost application.

	Methods

Table 9 :

 9 Review of the development of POME applications.

Table 10 :

 10 Review of the development of soil-mixed waste applications.

Te Scientifc World Journal

Description: n � none (not available): P � phosphorus, K � potassium, S � sulfur, Ca � calcium, Mg � magnesium, and Fe � iron are represented by the unit % (percentage); Mn � manganese, Cu � copper, Zn � zinc, and B � boron are represented by the units ppm or mg/kg.

Acknowledgments

Te authors would like to thank ANJ Research Center Library and Agricultural Science Department, Padjadjaran University, for the facility and technical support during the research work. PT Austindo Nusantara Jaya Tbk, ANJ Research Center, supported this study in collaboration with the Faculty of Agriculture, Padjadjaran University, Indonesia, and Perennial Crops Department, AbSys Research Unit, Centre de Coopération Internationale en Recherche Agronomique pour le Développement, France.

Data Availability

Te experimental data used to support the fndings of this study are available from the corresponding author upon request. Te data are also available at https://fairsharing.org/ users/6709.

Conflicts of Interest

Te authors declare that there are no conficts of interest regarding the publication of this paper.

Authors' Contributions

All the authors contributed to the study's conception and design. J.S. and M.R.S. coordinated the writing process and wrote the general parts of the manuscript (Abstract, Introduction, Materials and Methods, and Conclusion). Supervision, writing-review, and editing were performed by M.R.S. Supervision, literature review, and editing were performed by R.S. and C.H. Literature review and revision were performed by X.B.


Michel Dojat
email: dojat@laforia.ibp.fr

Laurence Brochard

François Lemaire

Alain Harf

Laurent Brochard

A KNOWLEDGE-BASED SYSTEM FOR ASSISTED VENTILATION OF PATIENTS IN INTENSIVE CARE UNITS

Keywords: Assisted ventilation, Knowledge-based system, Medical decision-making, Process control, Real-time, Weaning from mechanical ventilation

A knowledge-based system for assisted ventilation of patients in intensive care units.

INTRODUCTION

In Intensive Care Units (ICUs), the management of a patient receiving respiratory support may be complex, and requires considerable clinical expertise. A common strategy is to place the patient as soon as possible under partial mechanical assistance such as Pressure Support Ventilation (PSV), so that he can gradually participate in the work of breathing. The clinician adjusts the ventilator settings according to the physiological needs of the patient, and adapts the level of assistance so as to maintain the patient in a state of "comfort". The procedure of weaning from the ventilator may be a difficult step for some patients who have been ventilated for long periods, especially those ventilated for acute exacerbation of chronic obstructive lung disease. Before the clinican proceeds to withdraw the ventilator, he should appreciate the patient's capacity to breathe without assistance. Recently, several advances have been made in working out strategies for difficult-to-wean patients [START_REF] Brochard | Improved efficacy of spontaneous breathing with inspiratory pressure support[END_REF][START_REF] Brochard | Inspiratory pressure support prevents diaphragmatic fatigue during weaning from mechanical ventilation[END_REF][START_REF] Macintyre | Respiratory function during pressure support ventilation[END_REF]. At best, these strategies need a constant monitoring of the ventilated patient, in order to adjust the ventilator settings to the evolution of the patient's respiratory status. For this reason, they may be hard to use in clinical practice. The object of this study was to build a computer-controlled system to implement such a strategy.

Because most of the control of mechanical assistance and of weaning decisions is based on objective data, the clinician's reasoning is essentially data driven. Thus, a rule-based approach is a priori well adapted to the representation of the expert knowledge.

In the field of mechanical ventilation, many systems using Artificial Intelligence techniques have been proposed such as VM [START_REF] Fagan | Representing time dependant relations in a medical setting[END_REF], VQ-ATTENDING [START_REF] Miller | Goal directed critiquing by computer: ventilator management[END_REF],

ESTER [START_REF] Hernandez-Sande C | ESTER: an expert system for management of respiratory weaning therapy[END_REF], KUSIVAR [START_REF] Rudowski R | A knowledge-based support system for mechanical ventilation of the lungs. The KUSIVAR concept and prototype[END_REF] and COMPASS [START_REF] Sittig | A computerized patient advice system to direct ventilatory care[END_REF]. Each system has its own characteristics.

For example, KUSIVAR and VM manage different ventilatory modes, COMPASS is designed for patients with severe respiratory failure (Acute Respiratory Distress Syndrome), and ESTER needs the participation of the clinical staff to feed the system with physiological indices. These systems supply advice to the clinician but do not act directly on the ventilator to adjust its settings ; this is because of the complexity of the problems they are trying to solve, and the extreme diversity of the patients they ventilate. GANESH, the system described in this paper, deals with a limited problem and has two main features: i) it is designed to work for a specific period of mechanical ventilatory support, while the patient is recovering a spontaneous breathing activity, at a time when a strategy is required to wean the patient from the ventilator, and ii) only one mode of assisted ventilation is controlled by the system: Pressure Support Ventilation (PSV).

With these specifications in mind, we constructed GANESH, which is a closed-loop system. GANESH acquires and processes a set of data, appreciates the current respiratory status and its evolution, establishes a diagnosis of respiratory status severity, determines the action to be taken, and implements it by acting directly on the ventilator. In addition, as a part of its diagnostic capacity, it indicates when the patient can be weaned from the ventilator.

In this paper, we describe the prototype of GANESH, and report the clinical tests performed on 19 patients. These tests were designed to evaluate the ability of our system to adapt the respiratory assistance to the patient's needs, in order to facilitate weaning by gradually lowering the level of assistance.

MATERIALS AND METHODS

Description of the expert system GANESH

Architecture

We used three fundamental parameters to assess the patient's respiratory status: respiratory rate (RR), tidal volume (Vt), and end-tidal partial pressure of carbon dioxide (PetCO 2 ).

As shown in Figure 1, the system uses conventional serial communication protocols (RS 232) to acquire patient's data from the ventilator (RR, Vt) and from a gas analyzer (PetCO 2) . These parameters are acquired and averaged at a sampling frequency of 0.1 Hz over periods of 2 to 10 minutes.

During Pressure Support Ventilation (PSV), i.e. the mode of assisted ventilation chosen, a preset level of pressure is delivered as a plateau during each spontaneous inspiration. For a high level of pressure, the work of breathing performed by the patient is minimal, and the respiratory muscles are hardly loaded. By contrast, when the level of pressure is low, most of the work of breathing is performed by the patient. When insufficient pressure is delivered to the patient, respiratory discomfort occurs and a pattern of rapid shallow breathing is observed.

During PSV, the patient controls his own respiratory rate, inspiratory time and tidal volume. A positive correlation between tidal volume and the level of pressure support, and an inverse correlation between the respiratory rate and the level of pressure support have been observed [START_REF] Brochard | Improved efficacy of spontaneous breathing with inspiratory pressure support[END_REF][START_REF] Brochard | Inspiratory pressure support prevents diaphragmatic fatigue during weaning from mechanical ventilation[END_REF]. The principle of the system described here is to adapt the pressure support level so that the respiratory rate of the patient is maintained within a range of 12 to 28 breaths per minute, the tidal volume is above the minimum threshold and PetC0 2 below the maximum threshold. Lastly, the system tries automatically to reduce the pressure support level, to facilitate gradual weaning from the ventilator.

From the level of pressure support which the patient needs to remain in the zone of comfort described above, GANESH evaluates the degree of abnormality of the respiratory system. When a low level of assistance is sufficient to maintain the breathing pattern in the zone of comfort (9 cmH 2 0 for a tracheally intubated patient), the possibility of permanent weaning from the ventilator is envisaged [START_REF] Brochard | Inspiratory pressure support compensates for the additional work of breathing caused by the endotracheal tube[END_REF]. When this level of assistance is maintained for a specified period of time, the patient is diagnosed by the system as fit to be weaned.

After each data acquisition, the control-loop real-time system consults the knowledge base, establishes a diagnosis and acts on the ventilator. It works without any intervention from the clinical staff except at the initialization of the system. A cycle can be stopped by specific action of the physician on the keyboard. For each expertise, a simple report is displayed on the computer screen, printed and saved.

The report includes the ventilatory status of the patient, the actions performed, and the ventilator settings used.

We devised a way in which the system was able to run on a microcomputer placed at the of the patient's bedside. The prototype was connected via two serial ports to a Veolar ventilator (Hamilton, Bonaduz AG, Switzerland) especially adapted for this purpose by the manufacturer. A gas analyser (5200 Ohmeda, Maurepas, France) was connected to another serial port. The application was written in C language. An inference engine (written in C) order 0 + (GSI, Paris, France) was used.

The knowledge base contained 142 rules.

In this system all ventilator alarms remain available throughout the period of automatic control. If no information is sent by the computer to the ventilator for a period of one minute, the ventilator automatically switches to the set-up imposed by the settings placed on its front panel.

Knowledge representation -Knowledge organization

The reasoning implemented in our system is based on the expertise in the

-Temporal aspects

The temporal dimension has been developed in this system, and three aspects are represented:

-evolution of the patient's respiratory status: the history of respiratory status is assessed by a symbolic entity which summarizes three previous consultations. Therefore, decisions are influenced both by the present status and by the patient's evolution.

reference to specific periods: several local clocks store the duration of specific periods (such as periods of stable respiratory status). The patient's current status is analyzed with reference to these periods.

-asynchronous events: when an alarm occurs on the ventilator (patient's disconnection, or apnea), a special reasoning is processed : acquisition is stopped to avoid accumulating invalid data during disconnection. In case of apnea, the pressure support level can be either decreased in case of hyperventilation or switched to controlled mechanical ventilation in case of hypoventilation.

-Interface

The user interface is designed to be concise and free of information overload.

The implementation and professional use of decision support systems in the medical field is surprisingly slow and some of the reasons may be found in the lack of attention given to the designing of the user interface [START_REF] Zimolong B | On the limits of expert systems and engineering models in process control[END_REF]. In different windows, we summarize the patient's parameters, ventilator settings, tolerance of parameters variations, the GANESH consultation report, and alarms [Figure 3].

-Protocol and patients

After approval by the Ethical Committee of our University, we performed a preliminary study of 19 patients, to verify that the system was able to keep the patients comfortable and reduce the assistance adequately during recovery. More precisely, the study was designed to explore two objectives: 1) whether the system was able to keep the patient's breathing pattern inside the predetermined zone of comfort and 2) whether a gradual decrease in ventilatory support would be observed in patients considered as good candidates for weaning.

Patients were selected for the study when the physicians in charge had decided to start trying to wean them from the ventilator because of sufficient improvement in their respiratory status. All patients were tracheally intubated, to allow mechanical ventilation. None of them was still experiencing difficult oxygenation that could be considered to impede weaning or necessitate high levels of FiO 2 (≥ 0.5). When the study began, the patients had been ventilated for several days in the PSV mode of assisted ventilation, and hemodynamic stability over the previous 24 hours was required. The system did not involve additional work for the clinical staff and did not interfere with the usual management of the patients: for instance they had endotracheal suctioning as often as required during the study.

Patients were divided in two groups, according to the values of their preweaning indices. Positive criteria for these indices were the following: oxygen saturation of the arterial blood (SaO 2 ) > 90% with an inspired oxygen fraction of 0.4 or less, negative maximal inspiratory force greater than 25 cmH 2 0, respiratory rate below 35 breaths per minute after one minute of disconnection from the ventilator, and vital capacity greater than 10 ml/kg. When at least three of these criteria were met patients were considered as good candidates for weaning: 10 patients fulfilled this condition (group 1). The second group (group 2) was made up of patients who failed to meet the preweaning criteria (n = 9). Table 1 gives the characteristics of the patient population. The two groups of patients were comparable for age, Simplified

Acute Physiology Score (SAPS) [START_REF] Gall | A simplified acute physiological score for ICU patients[END_REF] and weight.

At the beginning of the study, the system provided all the patients with 15 cmH 2 0 of pressure support. The system was then left in complete control of ventilation for a period that varied from 8 to 24 hours. The duration of this period was determined, either by the decisions of the system (proposition to withdraw mechanical ventilation or proposition to switch to controlled mechanical ventilation)

or by the therapeutical constraints affecting each individual patient. To consider the patient in a zone of "respiratory comfort" the following three conditions had to be satisfied: respiratory rate between 12 and 28 breaths/min, tidal volume above 250 ml for patients weighting less than 55 kg, and above 300 ml for those weighting more than 55 kg, and PetCO 2 below 55 mmHg (or below 65 mmHg for patients with chronic obstructive lung disease). In the zone of respiratory comfort, GANESH maintained or tried to lower the assistance level. At the end of the period of ventilation with GANESH, the final diagnosis made by the system was noted with regard to the possibility of withdrawing mechanical ventilation .

RESULTS

As expected, the average duration of ventilation with GANESH was longer for group 2 patients, who were not considered weanable, than for group 1 patients who fulfilled the preweaning criteria (Table 2). The mechanical assistance provided by the system was adequate since it kept the patients in the zone of respiratory comfort most of the time (95% of the total ventilation period for group 1 patients and 72% for group 2 patients). The average values for the three physiological parameters RR, Vt and PetCO 2 were similar for the two groups, inside and outside the zone of respiratory comfort (Table 3). At the end of the period of assisted ventilation with the system, all the patients in group 1 were stated to be weanable by GANESH: accordingly, they were withdrawn from the ventilator and the weaning was considered successful, since they were able to breathe alone without any sign of respiratory discomfort. For group 2 patients, however, mechanical assistance was continued, as advised by GANESH.

DISCUSSION

The system described in this study was designed to optimize the monitoring and the weaning procedure for mechanically ventilated patients.

-Medical aspects

Our aim with this system was to validate a type of reasoning linked to Pressure Support Ventilation (PSV) in order i) to ventilate patients according to their physiological needs and ii) to withdraw mechanical assistance progressively, with the final objective of weaning the patient from the ventilator altogether. This constitutes an approach to the automatization of the weaning procedure.

During weaning from mechanical ventilation, the respiratory muscles of the patients, who are often weakened by denutrition, sepsis, disuse atrophy or electrolyte disorders, have to bear high workloads, due to lung infection, high airway resistance and the presence of the endotracheal tube and ventilator circuit. Therefore, in most instances, failure of weaning from mechanical ventilation does not result from impaired gas exchange and hypoxemia, but from the inability of the respiratory muscles to cope with the imposed workload [START_REF] Tobin Mj | The pattern of breathing during successful and unsuccessful trials of weaning from mechanical ventilation[END_REF]. This generally leads to the fast shallow breathing which precedes hypercapnia, respiratory acidosis and respiratory arrest. That is why modes of ventilation designed to support respiratory muscle work have been developed and used as means of gradually separating the patient from the ventilator [1, 2, 3]. The system described here adjusts the level of pressure support by assessing its effects on the breathing pattern of the patient. In the PSV mode, the patient triggers the assistance by his inspiratory effort and switch it off on expiration. Several recent studies [START_REF] Brochard | Improved efficacy of spontaneous breathing with inspiratory pressure support[END_REF][START_REF] Brochard | Inspiratory pressure support prevents diaphragmatic fatigue during weaning from mechanical ventilation[END_REF][START_REF] Macintyre | Respiratory function during pressure support ventilation[END_REF] have shown the advantages of this mode especially in reducing the subject's respiratory work while allowing satisfactory gas exchange. It seems an increasingly promising mode of ventilation, as it provides the respiratory muscles with physiological assistance. Brochard et al [START_REF] Brochard | Improved efficacy of spontaneous breathing with inspiratory pressure support[END_REF][START_REF] Brochard | Inspiratory pressure support compensates for the additional work of breathing caused by the endotracheal tube[END_REF] have shown the advantage of this mode for weaning the patient compared to conventional methods.

PSV is not a volume-controlled mode. Thus, any alteration in respiratory mechanics alters the volume delivered at inspiration. This is why it may be necessary to change the level of PSV frequently. The problem for the clinician is to evaluate the patient's needs correcty, with the relevant indices. As indicated in a previous study [START_REF] Tobin Mj | The pattern of breathing during successful and unsuccessful trials of weaning from mechanical ventilation[END_REF], the respiratory rate is in many circumstances a precise reflection of how well the respiratory muscles are adapted to the imposed workload. When the muscles deal with an excessive load, tachypnea rapidly ensues. In our study, respiratory rate was the parameter most often used to change the pressure support level. Our results also show that Vt was a good index for assessing the adaquacy of assistance, but that PetCO 2 , as used in the present study, was not very useful in this respect. After comparable durations of ventilation for the two groups (10 hours and 14 hours for groups 1 and 2 respectively), the level of assistance provided by the system in order to maintain physiological parameters in an acceptable range was 10 cmH 2 0 higher for group 2 (non weanable patients) than for group 1. Like other authors [START_REF] Tobin Mj | The pattern of breathing during successful and unsuccessful trials of weaning from mechanical ventilation[END_REF][START_REF]Is weaning an art or a science ?[END_REF], we postulated that the use of simple non-invasive indices to characterize the patient's respiratory status is pertinent to the management of the weaning process. The present clinical results support this approach.

Clearly, our study shows that rational checking of the level of assistance and the breathing pattern allows computer control of mechanical assistance and enables a decision to be proposed about weaning.

-Clinical decision support system

Several modalities of servo-controlled PSV have been proposed, such as those of Hamilton and Taema with Veolar and Cesar ventilators respectively [START_REF] Boyer | Aide inspiratoire avec asservissement du niveau de pression : volume ventilé versus fréquence ventilatoire[END_REF], both of them based on conventional algorithms. Basically, these modalities monitor a physiological parameter like tidal volume or spontaneous frequency and use it as a variable for the servo-control of PSV. The adjustment of PSV maintains either minute volume or spontaneous frequency at a specific target level fixed by the clinician.

Different negative aspects of these modes of control have been reported [START_REF] Boyer | Aide inspiratoire avec asservissement du niveau de pression : volume ventilé versus fréquence ventilatoire[END_REF].

Moreover, the algorithms on which they are based, do not reflect the attitude of the physician who is trying to maintain the patient in a overall respiratory comfort in relation to a set of parameters and to their evolution. By using a rule-based approach,

we were able to model the clinician's expertise and adapt the decision to different clinical situations. The rule-based formalism is efficient for the expertise considered because the modelized knowledge consists of specific rules applied to explicit entities in the relevant domain. The structure of the knowledge base in blocks, which represent several clusters of knowledge [START_REF] Gomez F | Knowledge organisation and distribution for medical diagnosis[END_REF], facilites the modelization of the control of the reasoning (the firing of rules) and preserves the steps in this reasoning. Specific rules (metarules) activate the blocks, depending on the context.

The usual problem of the response time of a such rule-based system in real time applications is not crucial in the present application. The ventilation is essentially a low frequency phenomenon (< 0.02 Hz) and the actions in alarm cases (apnea or disconnection) were performed in less than 2 second, with a 286 processor at 12 MHz. The patients were never in critical regions (low Vt, bradypnea, tachypnea) for longer than the time required to identify a situation as such (period of data acquisition of 2 or 5 min). In ICU, the quantity of data available on any one patient is enormous. It is important to determine what data is pertinent and how often is necessary to sample and store it. We chose to use three relevant physiological indices, collect them every 10 seconds and store them every 2, 5, or 10 minutes. The clinical results justify our choice.

In our study, the system managed the ventilation of 19 patients correctly, and diagnosed their ability to be weaned. Although, this approach will have to be validated for a larger sample of patients, including more with prolonged difficulties of separation from the ventilator, these preliminary results indicate that the decisons taken by the system seem reliable.

Information technology must be used to improve the quality of medical care.

In our opinion, systems capable of monitoring physiological data in real time and applying therapeutical actions in a well-known environment, would prove very helpful to physicians. Clearly, the necessary formalization of the expertise for its implementation on a computer implies the rationalization of clinical methods, and may allow future standardization. It has been demonstrated that medical decision making by physicians can be improved by incorporating certain formal decision-aids into clinical routine [START_REF] Ohmann | Methods, statistical performance and clinical benefit of decision support systems[END_REF].

Future developments will require enlargement of the knowledge base to include other physiological parameters than those currently used, in order to estimate more precisely the respiratory comfort of the patient, and to assess his physiological needs with a view to optimizing the mechanical assistance. On the basis of the working prototype described here, we are exploring a general architecture for knowledge-based systems which would support different clinical procedures in anesthesia and intensive care.

FIGUREs

Figure 1:

Information exchange in the GANESH system.

The communications with the ventilator and gas analyser use the RS 232 protocol.

GANESH is implemented on a PC computer. This diagram shows the different situations in which the ventilator settings can be modified. At the initialization, the values entered by the clinician are used by the system to fix safety limits. When respiratory status is "good", i.e., the patient is in the zone of respiratory comfort (see definition in the legend to Patients #1, #5 and #7 were always in the zone of respiratory comfort. In group 1, the longest time spent outside comfortable limits was seen in patient #8 (17% of the total time of the study, but most of it was spent in the intermediate zone).

The mean periods spent in bradypnea, tachypnea or low Vt represent 1% of the total duration of the ventilation. The mean period spent outside the respiratory comfort limits constituted 28% of the total duration of ventilation (18% in the intermediate zone).

  management of weaning acquired by the clinical staff of the medical ICU of the Henri Mondor Hospital, and on published data concerning PSV[START_REF] Brochard | Improved efficacy of spontaneous breathing with inspiratory pressure support[END_REF][START_REF] Brochard | Inspiratory pressure support prevents diaphragmatic fatigue during weaning from mechanical ventilation[END_REF][START_REF] Macintyre | Respiratory function during pressure support ventilation[END_REF]. We represented the expertise with production rules in zero order logic. The complete organization of the reasoning is shown in Figure2. We divided the knowledge base into several blocks encoding different types of knowledge representative of different cognitive steps. Details concerning these blocks are given below, together with some typical examples. The first block infers information from the data provided by the clinician about the patient, including anthropometric data, presence of chronic lung disease, and mode of assistance. This information is representative of Static Knowledge. Example: rule 3: IF the patient is tracheostomized THEN pressure support before weaning can be envisaged = 5 cmH 2 0 The second block assesses the severity of the ventilatory dysfunction from the level of pressure support needed by the patient, and determines the duration of the observation period before pressure support can be decrease. Example: rule 2: IF pressure support ≥ 15 AND pressure support < 20 cmH 2 0 THEN the period of observation = 240 min The third block assesses the respiratory status of the patient and compares it to the predetermined range of comfort. It therefore evaluates the quality of the ventilation. Example: rule 3: IF Vt < minimum Volume OR PetCO 2 > 55 mmHg THEN ventilation = "insufficient" The fourth block appreciates evolution of the respiratory status with time. Example: rule 4: IF ventilation =("tachypnea" OR "insufficient") AND the previous ventilatory checkUp = "normal" THEN stability = "bad" The fifth block defines, in relation to the previous modules, the action to be performed on the ventilator settings and the time that must elapse before a new expertise is launched (during this period, fresh data are acquired) . Example: rule 5: IF stability = "bad" THEN pressure support = previous pressure support + 4 cmH 2 0 AND new expertise = 5 minThe sixth block concerns the last step of the weaning procedure: when only a low level of assistance is needed, the respiratory status of the patient is observed for a predetermined period of time, to appreciate his ability to be weaned from the ventilator. If the patient tolerates this low level of pressure support throughout the observation period, the system will indicate that he can be weaned from the ventilator. Example: rule 6: IF the stability period < observation period before weaning THEN weaning = "in observation" AND stability period = previous stability period + duration of the expertise AND new expertise = 2 min All blocks except the first encode dynamic knowledge which is updated after each data acquisition. A specific block of rules deals with the alarms of the ventilator (apnea, disconnection, or hypoventilation). Example: rule 7: IF ventilation = "hypoventilation" THEN raises Alarm 4 AND switch to Mechanical Ventilation

2 peepFigure 2 :

 22 Figure 2:

Figure 4 :

 4 Figure 4:

Figure 5 :

 5 Figure 5:

Table 2

 2

	) assistance is

Table 3 :

 3 Respiratory values for weanable patients (group 1) and non-weanable patients (group 2) during the ventilation periods spent inside and outside the zone of respiratory comfort.This table shows the mean values of respiratory rate (RR) and tidal volume (Vt) while the patients were inside and outside of the zone of respiratory comfort (see definition in legend to table 2). Patients 1, 5 and 7 were in the zone of comfort throughout the study (see table2). For patients 9, 12, 13 no PetCO 2 data were available.

	Patient #		RR	RR	Vt	Vt	PetCO2
			inside the zone	outside the	inside the	outside the	inside the zone
				zone	zone	zone
			of comfort	of comfort	of comfort	of comfort	of comfort
			(breaths/min)	(breaths/min)	(ml)	(ml)	(mmHg)
		1	21	-	615	-	30
		2	20	29	407	383	31
		3	23	34	425	393	28
		4	25	28	359	344	36
		5	18	-	558	"	33
	GROUP 1	6	23	29	658	669	29
		7	19	-	617	-	33
		8	21	27	527	512	27
		9	23	29	444	376	-
		10	19	18	410	397	34
	Mean (± SD)		21 ± 2	28 ± 5	502 ± 106	439 ± 114	31 ± 3
		11	20	34	636	541	31
		12	16	30	850	540	-
		13	23	27	640	550	-
		14	16	21	617	520	52
	GROUP2	15	24	33	478	425	29
		16	21	29	380	333	34
		17	23	29	550	462	24
		18	19	28	557	455	26
		19	20	28	304	265	39
	Mean (± SD)		20 ± 3	29 ± 4	557 ± 160	455 ± 100	34 ± 10

Acknowledgments

The authors wish to thank Dr. Josef Brünner from the Hamilton Company for his assistance in helping to implement the communication between the computer and the ventilator, and for his useful comments, and Martine Laforest and Dominique Touchard for their active participation in the clinical evaluation of our prototype.

This study was supported by a grant from la Délégation à la Recherche Clinique de l'Assistance Publique -Hôpitaux de Paris.

Differents units summarize the main information. Top left: patient's current data and the number of data acquisitions performed (data processing). Top right: the ventilator settings. The bottom left unit indicates the patient's status and the action performed. In the clinical case represented, the patient was disconnected from the ventilator for suctioning, and after reconnection, the system did not modify the level of pressure support. A new data acquisition was then performed for 2 minutes (new expertise in 2 min). The alarm unit indicates the important alarms occurring during data acquisition (here, reconnection of the patient after 3 minutes of disconnection).

The bottom right unit represents the physiological thresholds used to measure minimum tidal volume (Vt), maximum PCO 2 (Pco2), maximun respiratory rate (RR),