High-solids Anaerobic Digestion Process Research Articles

Enhancing the efficiency of high solid anaerobic digestion of empty fruit bunches under thermophilic conditions by particle size reduction and co-digestion with palm oil mill effluent

This study investigates the impact of thermophilic high solid anaerobic digestion (HS-AD) on biogas production from empty fruit bunches (EFB), focusing on the effects of total solids (TS) loading (5–40 %), particle size reduction (0.5, 3.25, and 6 cm), and co-digestion with palm oil mill effluent (POME) (10–30 % VS basis). The HS-AD at a 15–20 % TS loading has a methane yield of 103.4–105.3 mL CH4/g-VS with 24.6–25.1 % biodegradability. Particle size reduction to 0.5 cm enhanced methane yield by 54–61 % and improved hydrolysis rates by 45 % compared to the untreated EFB (6 cm) at a 15–20 % TS loading. Co-digestion of EFB with POME at a ratio of 31:1 based on VS basis led to a synergistic effect of 17.77 mL CH4/g-VS, increasing methane yield by 24–46.5 % and improving process stability, as evidenced by a 22.8–38.1 % reduction in volatile fatty acids (VFAs) accumulation. Microbial community analysis showed a 2-fold increase in the relative abundance of hydrogenotrophic methanogens (Methanothermobacter sp. and Methanoculleus sp.) during co-digestion, while the abundance of key cellulolytic bacteria (Clostridium sp. and Fibrobacter sp.) increased by 1.5-fold. The optimized HS-AD process achieved a maximum methane yield of 287.77 mL CH4/g-VS and a biodegradability of 61.2 % under thermophilic conditions, with a 20 % POME co-digestion addition (31:1 VS ratio) and 0.5 cm particle size. These findings demonstrate the potential of thermophilic HS-AD for the sustainable management of EFB and highlight the importance of process optimization and co-digestion strategies for enhanced biogas production from EFB.

Hygienic assessment of digestate from a high solids anaerobic co-digestion of sewage sludge with biowaste by testing Salmonella Typhimurium, Escherichia coli and SARS-CoV-2

Anaerobic digestion is a consolidated technology to convert sewage sludge and other organic wastes into biogas and a nutrient-rich fertilizer (i.e. digestate). The origin of sewage sludge does not exclude the potential presence of pathogens (e.g. Salmonella spp. and SARS-CoV-2) in mature digestate that hence could represent a source of sanitary concerns when it is spread on soil for agriculture purpose. Therefore, an experimental study aimed at proving the sanitizing effect of a full scale thermophilic high solids anaerobic digestion process was conducted by monitoring the hygienic characteristics of mature digestate. Although Salmonella spp. was detected in the sewage sludge fed to the full scale plant, the anaerobic digestion treatment demonstrated sanitization capacity since the monitored pathogens were never found in the mature digestate over the entire duration of the monitoring survey. Furthermore, tests on the regrowth of Salmonella Typhimurium and Escherichia coli, artificially inoculated on mature digestate, were also conducted under both anaerobic and aerobic conditions with the aim to assess the effectiveness of mature digestate as microbial growth medium. Concentrations of Salmonella Typhimurium and Escherichia coli were drastically reduced after a short time of incubation under anaerobic process and the two microorganisms already resulted undetectable after 24–48 h, whereas, under aerobic conditions, two microorganisms’ concentrations were stably high for longer than 10 days. The combination of no free oxygen, high temperature, anaerobic metabolites (e.g. total ammonium nitrogen, and volatile fatty acids) production, bacteria competition and lack of nutritional elements in mature digestate considerably reduced in 24–48 h the sanitary risks associated to accidently contaminated digestate. Furthermore, a SARS-CoV-2 monitoring survey on mature digestate during 13 months, resulted in the absence of the virus RNA in the analyzed digestate.

Evaluation of Ca(OH)2 disintegration on high-solid sludge floc structures and subsequent anaerobic digestion

Lime pretreatment was tested at different doses on high-solid sludge. Subsequently, the effects of this pretreatment were investigated in terms of the damage of extracellular polymeric substance and cell structures and the subsequent high-solid anaerobic digestion (HSAD). Moreover, the relationship between them was discussed. Results showed that higher lime dose was favorable to COD solubilization, wherein more proteins were released than carbohydrates under the same lime dose. When lime dose was below 0.04 g/g-TS, the COD solubilization was mainly caused by the disintegration of EPS, and when the lime dose was higher than 0.06 g/g-TS, the damages of cell walls and membranes were observed and led to the further COD solubilization. The HSAD process was accelerated by 7–16 days after lime pretreatment, and the biogas production increased by 22.9%–34.8% when lime dose was higher than 0.04 g/g-TS. Thermogravimetric analysis results suggested that Ca2+ could be removed from the liquid phase by precipitating with the CO2 produced during the HSAD process, thereby increasing the methane content.

High-Solids Anaerobic Digestion Followed by Ultrasonication of Digestate and Wet-Type Anaerobic Digestion for Enhancing Methane Yield from OFMSW

High-solids anaerobic digestion of organic fraction of municipal solid waste often shows inefficient biomethane recovery due to mass transfer limitations. Consequently, this study presents a two-stage anaerobic digestion process combining high-solids anaerobic digestion followed by ultrasonication of digestate and wet-type anaerobic digestion for effective biomethane recovery from the organic fraction of municipal solid waste. The high-solids anaerobic digestion yielded methane production of 210 L CH4/kg volatile solids (VS). The digestate from the high-solids anaerobic digestion process was ultrasonicated at three different specific energy inputs (1000, 2500, and 5000 kJ/kg total solids (TS)). The increases in the soluble chemical oxygen demand (SCOD) concentrations (8%–32%) and volatile solids (VS) removal efficiencies (3.5%–10%) at different specific energy inputs were linearly correlated (R2 = 0.9356). Thus, ultrasonication led to the solubilization of particulate organics and released soluble organic matters. All ultrasonicated digestate samples showed significantly higher biomethane yields than that observed for the untreated digestate samples. The highest methane yield of 132 L CH4/kg VS was observed for a specific energy input of 5000 kJ/kg TS, which was 1.94 times higher than the control (68 L CH4/kg VS). Although specific energy inputs of 1000 kJ/kg TS and 2500 kJ/kg TS showed comparable methane yields (113–114 L CH4/kg VS), they were ~1.67 times higher than the control. Overall, our results suggest that an integrated system of high-solids and wet-type anaerobic digestion with pre-ultrasonication of digestate has the potential to provide a technically viable solution to enhance biomethane recovery from the organic fraction of municipal solid waste.

Humification in extracellular polymeric substances (EPS) dominates methane release and EPS reconstruction during the sludge stabilization of high-solid anaerobic digestion

High-solid anaerobic digestion (HAD) can directly treat dewatered sewage sludge (total solid content ≥15%) with superior volume efficiency. Sludge stabilization during HAD is expected to achieve by throughout organic degradation and conversion towards methane-rich biogas release and humic formation. Sewage sludge is the combination of microbial zoogleas and theirs adsorption of organic and inorganic matter, in which the extracellular polymeric substances (EPS) account 60-80% of total sludge organic matter, inevitably participating most extracellular metabolic pathways. The interactions between EPS transformation and genetically annotated metabolic pathways were found in this research. In brief, noticing the highly cross-linked structures in EPS with major active components of humic substances (HS) and protein (PN), as PN hydrolysis and decomposition in EPS were enhanced in the high-solid anaerobic condition, the exposure of aromatic groups and sites in HS were considerable. HS release was the main factor shifting the electron exchange capacity and activity, which aided in energy metabolism of sludge microorganisms involved in redox reactions, especially the methanogenesis, thus in turn facilitating the PN degradation; Then, the screened humic groups and active protein derives might act as the beneficial precursors to regenerate neo-humic structures, whose significant bridging effect and signal role on stimulating amino acid biosynthesis, member transport and metallic complexation could further contribute to proteolytic condensation and EPS reconstruction. Hence, the in-depth sludge stabilization mechanism during HAD process was established for developing enlightening strategies.

Impact of Leachate in the Soil Vellalore, Coimbatore

As a consequence of increasing urbanisation and industrialization two major effects have occurred. They are resource exploitation and waste generation. In this view, the present work has been undertaken to study problems of open dumping of MSW at Vellalore disposal site of Coimbatore city. The objectives of the present study are monitor and assess the problems of principle solid waste on land and to investigate the feasibility of energy recover from MSW. Physical and chemical characterization of MSW collected from the disposal site showed that the solid waste has 68.95% of biodegradable fraction with relatively higher percentage of moisture content and 72% of volatile solids contents. Hence, methanation process of MSW can be carried out to recover energy. Leachate characterisation study concludes the that the concentration of Total Organic Carbon, Ammonia nitrogen, volatile solids, pH , electrical conductivity were high in fresh leachate and decreased due to the decomposition of MSW. Soil quality study of Vellalore site showed that the soil texture and colour has been altered to a depth of 60cm.To manage the solid waste problem, high solids anaerobic digestion process was carried out in the laboratory in a batch reactor, which showed that the factor pH was found to be significant in the production of biogas. The concentration of volatile solids, Total carbon, Total nitrogen, due to the decomposition of the reactor contents, which has utilized in the production of gas. During the experimental study a cumulative volume of 3.2 litres of gas was obtained in a period of 120 days from 8 litres volume of the initially loaded MSW.

Impacts of ferric chloride, ferrous chloride and solid retention time on the methane-producing and physicochemical characterization in high-solids sludge anaerobic digestion

This study used a batch experiment and a long-term experiment to investigate the effects of FeCl3 and FeCl2 on the high-solids anaerobic digestion (HSAD) of sludge for improving the methane productions. The results of batch experiment with an organic loading rate of 6.93 gVS/L suggested that the cumulative methane productions were enhanced by 28.9% and 6.4% with 200 mg/L FeCl3 and 250 mg/L FeCl2 in HSAD system, respectively. The higher methane productions were also obtained by 200 mg/L FeCl3 and 250 mg/L FeCl2 in the long-term experiment for 114d. An excessive FeCl3 could inhibit the HSAD process, which would be gradually recovered by the ammonia and the microbes acclimated to this environment. The organics degradation results indicated that the addition of 200 mg/L FeCl3 or 250 mg/L FeCl2 could show a positive effect on the substrate environment of a stable total volatile fatty acids (TVFA) concentration and pH, and promote the protease and dehydrogenase activities in HSAD system. In addition, the SRT played a significant role in the HSAD process by balancing hydrolysis-acidification and methanogenesis. An appropriate dosage of FeCl3 and FeCl2 improved the methane productions, and blocked the accumulation of TVFA caused by shortening SRT.

Effect of aromatic repolymerization of humic acid-like fraction on digestate phytotoxicity reduction during high-solid anaerobic digestion for stabilization treatment of sewage sludge

Humification plays an important role in the sewage sludge stabilization treatment and probably influences the end-product ecotoxicity, which are not fully understood for high-solid anaerobic digestion (AD) process. This study monitored the aromaticity degree of humic acid-like fraction (HA) and detected digestate phytotoxicity during a 48-d high-solid AD. Significant repolymerization of aromatic structures in HA. Electrical conductivity (EC) of digestate changed negatively with the aromaticity degree in HA, and the digestate with high EC had low seed germination index (SGI). A positive correlation between SGI and the aromaticity degree of HA was found. Aromatic repolymerization of HA supplies more aromatic electron-rich sites to form neo-humic polymers and to determine the distribution of organic and/or inorganic phytotoxic compounds; thus, aromatic repolymerization of HA may control the digestate phytotoxicity by reducing excessive salinity. The results showed the effect of HA repolymerization on digestate stabilization and phytotoxicity reduction during the high-solid AD process. The inadequate phytotoxicity reduction efficiency (SGI ≤ 17%) may be ascribed to unaccomplished HA repolymerization, creating a demand for humification intensification studies.

HIGH-SOLID ANAEROBIC CO-DIGESTION OF FOOD WASTE AND DAIRY MANURE: A PILOT SCALE STUDY AT LOW-TO-MODERATE TEMPERATURE CONDITIONS

Treating organic solid wastes economically is a challenge, predominantly in cold and high-altitude regions. Objective of this research was to determine the operating strategies to reduce the start-up phase of high-solid anaerobic digestion (HSAD) process and to improve the digestion of food waste (mainly fruits and vegetable wastes [FVW]) with or without animal manure in a low-cost AD system at 20-25°C. In addition, this study aimed to obtain the basic design criteria for starting up of scaled-up HSAD system using adapted liquid inoculum. Inoculum to feedstock ratio was varied from 6:1 to 3:1. The organic loading rate (OLR) expressed as volatile solids (VS) and operational cycle length was varied from 0.44 -2.1 KgVS Kginoculum-1 d-1 and 33 -14d, respectively. Obtained results show that methane (CH4) production from FVW was feasible at low-to-moderate temperature and specific methane yield of 0.4-0.6 L gVS-1 was observed even at high OLR. CH4 conversion rates and its quality were not affected, while maintaining the operational stability (e.g. no acidification or VFA accumulations). CH4 content reached over 60Ϻnd remained almost steady. Results also suggest that HSAD process at 25°C is comparatively efficient in saving heat energy and at the same time obtains the CH4 values close to mesophilic conditions. This means that the smaller size digester (in the case of HSAD) is preferred as there is no waste dilution involved and also suitable for cold countries. Using this concept, livestock producers can play a role in reducing GHG emissions while also earning C-offset credits.

Microbial Insight into a Pilot-Scale Enhanced Two-Stage High-Solid Anaerobic Digestion System Treating Waste Activated Sludge.

High solid anaerobic digestion (HSAD) is a rapidly developed anaerobic digestion technique for treating municipal sludge, and has been widely used in Europe and Asia. Recently, the enhanced HSAD process with thermal treatment showed its advantages in both methane production and VS reduction. However, the understanding of the microbial community is still poor. This study investigated microbial communities in a pilot enhanced two-stage HSAD system that degraded waste activated sludge at 9% solid content. The system employed process “thermal pre-treatment (TPT) at 70 °C, thermophilic anaerobic digestion (TAD), and mesophilic anaerobic digestion (MAD)”. Hydrogenotrophic methanogens Methanothermobacter spp. dominated the system with relative abundance up to about 100% in both TAD and MAD. Syntrophic acetate oxidation (SAO) bacteria were discovered in TAD, and they converted acetate into H2 and CO2 to support hydrogenotrophic methanogenesis. The microbial composition and conversion route of this system are derived from the high solid content and protein content in raw sludge, as well as the operational conditions. This study could facilitate the understanding of the enhanced HSAD process, and is of academic and industrial importance.

Integration of high-solid digestion and gasification to dispose horticultural waste and chicken manure

Abstract To realize full energy recovery from grass and chicken manure (CM), the integration of high-solid anaerobic digestion (HSAD) and gasification was investigated experimentally. The anaerobic biodegradability of grass can be enhanced through codigestion with CM. When the volatile solids (VS) ratio of CM to grass was 20:80, C/N ratio calculated to be 21.70, the cumulative biogas yield was the highest, 237 ml·g − 1 VS. The enhancement of biogas production was attributed to the buffering effects of ammonia and rich trace elements in CM. In semi-continuous systems, when the organic loading rate was 4.0 g VS·L − 1 ·d − 1 , the HSAD process was stable, with the average biogas yield 168 ml·g − 1 VS. More than 80% fractions of the digestates were volatile matters, which meant that the digestates can be used as feedstock for gasification to produce syngas. The VS ratio of grass to CM had significant overall energy generation through HSAD and gasification. Compared with gasification of digestate, cogasification with woodchips increased syngas yield and low heat value (LHV). Increasing of mass ratio of digestates to woodchips led to the decrease of LHV.

Akron, Ohio – a high solids anaerobic digestion process replaces a successful In-Vessel composting operation

For 26 years, the City of Akron had been managing their wastewater solids using the in-vessel Paygro Composting process. While the operations of the facility and the marketing of the finished compost was successful, the concern by the public over the odor generation, the steadily increasing operational costs and the need for a large capital investment to continue composting, as a result of the facility showing its years of wear from the operations, was the reason for the City to move forward with building a new 13,607 dry t (15,000 dry ton) anaerobic digestion (AD) plant. The new 13,607 dry t (15,000 dry ton) AD plant modeled the 4535 dry t (5000 dry ton) Schmack BioGas AG AD plant built in 2007, which was used to validate the operational process and understand the biogas generation prior to going full scale. With the success of the 4535 dry t (5000 dry ton) AD plant, the City in 2011 entered into a long term contract with KB BioEnergy (formerly KB Compost) to build and operate the new 13,607 dry t (15,000 dry ton) (AD) plant on the same grounds that the composting facility existed now known as the Akron Renewable Energy Facility. The $32M plant would use the BIOFerm Energy Systems/Schmack BioGas AD technology. Three 600 kW MWM all-in-one packages from 2-G Cenergy were purchased to convert the biogas to electricity. In addition, an indirect paddle dryer by Komline Sanderson was installed to further process the solids coming out of the AD plant to produce material suitable for market. Construction of the facility began in September of 2011 with the plant being operational by the end of 2013. To process the solids anaerobically, two 1000 cubic meter Eucos (horizontal plug flow tanks) and two 3000 cubic meter Coccus' (complete mix tanks) were constructed. One Euco and one Coccus act as a train capable of processing 6803 dry t (7500 dry tons) of solids. The feedstock consists of a liquid stream entering the Euco tanks at 5% solids and the solids stream where the dewatered sludge enters at 28–30% solids. Maintaining a temperature between 35°C and 37.8°C (95°F and 100°F) in the tanks, the material is slowly moved thru the Euco over the next 8 days where 50% of the biogas production occurs. The digested solids are then transferred to the Coccus where the retention time is approximately 20 days prior to being discharged to holding tanks. Material entering the holding tanks is between 9 and 11% solids. The digestate is then dewatered using centrifuges. This dewatered digestate cake is then the feedstock for the dryer where the solids enter at approximately 30% and leave at ≥92% solids. The biogas production from the process is approximately 11.3 m³/min (400 cfms). This biogas can be used to fuel the three 600 kW MWM engines or the thermal boilers used with the dryer or a combination of both depending on the need. With some of the biogas used in the thermal boilers, a biogas conditioning skid by Unison Solutions was installed that removes hydrogen sulfide, siloxanes if present and moisture. Normal operations result in the biogas being consumed by the engines with a power production of 1.2MW of electric capacity and 1.3MW of thermal capacity. An enclosed flare was installed to manage up to 17.0 m³/min (600 cfms) of biogas. After one year of operations, the 13,607 dry t (15,000 dry ton) AD plant has been able to process all the sludge generated by the Akron Water Reclamation Facility successfully. On average 12.0 m³/min (425 cfms) of biogas have been produced resulting in 1048 kWh generated or 87% design capacity. This paper will take a closer look at the operational numbers as well as the challenges that occurred along the way of commissioning the facility.

High Solids Anaerobic Digestion Process to Treat High Strength Municipal and Industrial Organic Waste

High Solids Anaerobic Digestion Process to Treat High Strength Municipal and Industrial Organic Waste

Thermophilic anaerobic digestion of sewage sludge with high solids content.

The treatment performance of thermophilic anaerobic digestion (AD) of sewage sludge with high solids content was investigated with two laboratory-scale thermophilic anaerobic reactors (R1 and R2) with a feeding of pre-centrifuged sewage sludge. Reactor R1 was fed with sludge of 3.7% total solids (TS). The volatile solids (VS) removal ratio and methane yield in the stable state were 54.9% and 0.29 NL CH(4)/g VS(added), respectively. For reactor R2, when the TS content of fed sludge was 7.4%, the VS removal ratio and methane yield in the stable state were 73.2% and 0.38 NL CH(4)/g VS(added), respectively. When the TS content was increased to 9.5%, the VS removal ratio and methane yield slightly decreased to 69.3% and 0.32 NL CH(4)/g VS(added), respectively, but the reactor was stably operated. An increase of ammonia concentration was observed, but it was in the safe range without severe inhibition on the methane production. The result indicated that thermophilic AD could support sewage sludge with high TS content (9.5%) without abrupt deterioration of the treatment performance. The high-solids AD process is an economical method for centralized sewage sludge treatment with lower transport cost.

Microbial Community Dynamics in Batch High-Solid Anaerobic Digestion of Food Waste Under Mesophilic Conditions

Microbial community shifts, associated with performance data, were investigated in an anaerobic batch digester treating high-solid food waste under mesophilic conditions using, a combination of molecular techniques and chemical analysis methods. The batch process was successfully operated with an organic removal efficiency of 44.5% associated with a biogas yield of 0.82 L/g VSremoval. Microbial community structures were examined by denaturing gel gradient electrophoresis. Clostridium and Symbiobacterium organisms were suggested to be mainly responsible for the organic matter catabolism in hydrolysis and acidogenesis reactions. The dynamics of archaeal and methanogenic populations were monitored using real-time PCR targeting 16S rRNA genes. Methanosarcina was the predominant methanogen, suggesting that the methanogenesis took place mainly via an aceticlastic pathway. Hydrogenotrophic methanogens were also supported in high-solid anaerobic digestion of food waste through syntrophism with syntrophic bacterium. Microbial community shifts showed good agreement with the performance parameters in anaerobic digestion, implying the possibility of diagnosing a high-solid anaerobic digestion process by monitoring microbial community shifts. On the other hand, the batch results could be relevant to the start-up period of a continuous system and could also provide useful information to set up a continuous operation.

Evaluating inhibition conditions in high-solids anaerobic digestion of organic fraction of municipal solid waste

High-solids anaerobic digestion (HSAD) processes, when applied to different types of organic fractions of municipal solid waste (OFMSW), may easily be subjected to inhibition due to organic overloading. In this study, a new approach for predicting these phenomena was proposed based on the estimation of the putrescibility (oxygen consumption in 20 h biodegradation, OD 20) of the organic mixtures undergoing the HSAD process. Different wastes exhibiting different putrescibility were subjected to lab-scale batch-HSAD. Measuring the organic loading (OL) as volatile solids (VS) was found unsuitable for predicting overload inhibition, because similar VS contents corresponded to both inhibited and successful trials. Instead, the OL calculated as OD 20 was a very good indicator of the inhibiting conditions (inhibition started for OD 20 > 17–18 g O 2 kg −1). This new method of predicting inhibition in the HSAD process of diverse OFMSW may be useful for developing a correct approach to the technology in very different contexts.

Demonstration-scale evaluation of a novel high-solids anaerobic digestion process for converting organic wastes to fuel gas and compost

Early evaluations of the bioconversion potential for combined wastes such as tuna sludge and sorted municipal solid waste (MSW) were conducted at laboratory scale and compared conventional low-solids, stirred-tank anaerobic systems with the novel, high-solids anaerobic digester (HSAD) design. Enhanced feedstock conversion rates and yields were determined for the HSAD system. In addition, the HSAD system demonstrated superior resiliency to process failure. Utilizing relatively dry feedstocks, the HSAD system is approximately one-tenth the size of conventional low-solids systems. In addition, the HSAD system is capable of organic loading rates (OLRs) on the order of 20-25 g volatile solids per liter digester volume per d (gVS/L/d), roughly 4-5 times those of conventional systems. Current efforts involve developing a demonstration-scale (pilot-scale) HSAD system. A two-ton/d plant has been constructed in Stanton, CA and is currently in the commissioning/startup phase. The purposes of the project are to verify laboratory- and intermediate-scale process performance; test the performance of large-scale prototype mechanical systems; demonstrate the long-term reliability of the process; and generate the process and economic data required for the design, financing, and construction of full-scale commercial systems. This study presents conformational fermentation data obtained at intermediate-scale and a snapshot of the pilot-scale project.

Development of a Mathematical Model for the Simulation of the Biodegradation of Organic Substrates in a High-Solids Anaerobic Digestion Process

A kinetic model is developed to simulate the biodegradation of the organic fraction of municipal solid waste in a high-solids complete-mix continuous-flow anaerobic digestion process. A mass balance correction factor (f) is used to account for (i) the water that is incorporated into the production of biogas, and (ii) the water vapor present in the biogas. With the inclusion of the factor f, expressions are developed to determine the substrate removal efficiency based on first-order and Monod kinetic models. Simulations using first-order and Monod kinetic models are carried out to illustrate the importance of the f factor on the substrate mass removal and microorganism concentration in the high-solids anaerobic digestion process. The effect of the value of f on kinetic constants, and the error involved in considering the high-solids process as a low-solids process are discussed. Finally, experimental results from a pilot-scale high-solids complete-mix batch-fed anaerobic digestion process are used to estimate the first-order rate constant for the biodegradable fraction of municipal solid waste.

Pilot-scale high solids thermophilic anaerobic digestion of municipal solid waste with an emphasis on nutrient requirements

A pilot study was conducted to assess the biodegradable organic fraction of municipal solid waste (BOF/MSW) as a substrate in a high-solids anaerobic digestion process. Results obtained indicate that a typical BOF/MSW in the United States is deficient in most macro and micro-nutrients required for robust and stable digestion. The BOF/MSW was supplemented with nutrient-rich organic wastes such as wastewater treatment plant sludges, dairy manure, and synthetic chemical solutions to correct nutritional deficiencies. The combined addition of wastewater treatment plant sludge and dairy manure to a typical BOF/MSW significantly elevated the gas production rate and enhanced the process stability. Microbial nutrient requirements are identified and nutrient concentrations for stable operation are quantified.