Anaerobic Digestion Of Kitchen Waste Research Articles

Effects of upward flow rate and modified biochar location on the performance and microecology of an anaerobic reactor treating kitchen waste.

Increasing the value of food waste through anaerobic digestion is an attractive strategy. Meanwhile, the anaerobic digestion of kitchen waste also faces some technical challenges. In this study, four EGSB reactors were equipped with Fe-Mg-chitosan bagasse biochar at different locations, and the reflux pump flow rate was increased to change the upward flow rate of the reactor. The effects of adding modified biochar at different locations under different upward flow rate on the efficacy and microecology of anaerobic reactors treating kitchen waste were investigated. Results showed that Chloroflexi was the dominant microorganism when the modified biochar was added to the lower, middle, and upper parts of the reactor and mixed in the reactor, accounting for 54%, 56%, 58%, and 47%, respectively, on day 45. With the increased upward flow rate, the abundance of Bacteroidetes and Chloroflexi increased, while Proteobacteria and Firmicutes decreased. It was worth noting that the best COD removal effect was achieved when the anaerobic reactor upward flow rate was v2 = 0.6m/h and the modified biochar was added in the upper part of the reactor, during which the average COD removal rate reached 96%. In addition, mixing modified biochar throughout the reactor while increasing the upward flow rate provided the greatest stimulus for the secretion of tryptophan and aromatic proteins in the sludge extracellular polymeric substances. The results provided a certain technical reference for improving the efficiency of anaerobic digestion of kitchen waste and scientific support for the application of modified biochar to the anaerobic digestion process.

Microbial response behavior to powdered activated carbon in high-solids anaerobic digestion of kitchen waste: Metabolism and functional prediction analysis

Anaerobic digestion (AD) can not only treat organic waste, but also recycle energy. However, high-solids AD of kitchen waste usually failed due to excessive acidification. In this study, the effect of activated carbon (AC) on kitchen waste AD performance was investigated under high-solids conditions (total solids contents = 15%). The results showed that efficiencies of acidogenesis and methanogenesis were promoted in presence of moderate concentration (50 g/L > AC >5 g/L), but high concentration (AC >70 g/L) weakened AD performance. Moreover, AC addition enhanced the methane production rate from 66.0 mL/g VS to 231.50 mL/g VS, i.e., up to 250.7%. High-throughput sequencing results demonstrated that the abundance of electroactive DMER64 increased from less than 1%–29.7% (20 g/L AC). As AC gradually increased，aceticlastic methanogenesis changed to hydrogenotrophic pathway. Predicted functional analysis indicated that AC can enhance abundances of energy and inorganic ion metabolism, resulting in high methane production.

Experimental Study On Production of Biogas from Kitchen Waste

In our institute we have four hostels and all having their own individual mess, where daily a large amount of kitchen waste is obtained which can be utilized for better purposes. Biogas production requires Anaerobic digestion. Project was to Create an Organic Processing Facility to create biogas which will be more cost effective, eco-friendly, cut down on land fill waste, generate a high-quality renewable fuel, and reduce carbon dioxide & methane emissions. Overall, by creating a biogas reactor on campus in the backyard of our hostels will be beneficial. Kitchen (food waste) was collected from different hostels of PACE IT & S Mess as feed stock for our reactor which works as an aerobic digester system to produce biogas energy. The anaerobic digestion of kitchen waste produces biogas, a valuable energy resource Anaerobic digestion is a microbial process for production of biogas, which consist of Primarily methane (CH4) & carbon dioxide (CO2). Biogas can be used as energy source and also for numerous purposes. But any possible applications require knowledge & information about the composition and quantity of constituents in the biogas produced. The continuously-fed digester requires addition of sodium hydroxide (NaOH) to maintain the alkalinity and pH to 7. For this reactor we have prepared our Inoculum than we installed batch reactors, to which inoculum of previous cow dung slurry along with the kitchen waste was added to develop our own Inoculum. A combination of these mixed inoculum was used for biogas production at 37°C in laboratory (small scale) reactor (20L capacity) In our study, the production of biogas and methane is done from the starch-rich and sugary material and is determined at laboratory scale using the simple digesters.

Thermophilic anaerobic digestion of kitchen waste driven by microbial electrolysis cell (MEC): Digestion performances, anodic microorganisms’ distribution and current utilization efficiency

The aims of present study were to investigate the performances of kitchen waste thermophilic anaerobic digestion driven by microbial electrolysis cell (MEC), and to clarify the methanogenic metabolism pathways on the electrodes (especially on the anodic biofilm). The results showed that both 0.6 V and 1.0 V voltages supplementation could enhance methane yields and production rates, while efficient methanogenesis failed to be sustained after power outages under high organic loading rate (OLR, 4.22 gVS/L/day) condition. Voltages supplementation could also enhance VS removal efficiencies from 83.24–83.35% to 87.01–87.46%, and strengthened the hydrolysis and acidogenesis of dissolved organic matters (DOMs) on the outer layer of anodic biofilm. Voltages supplementation accelerated the β-oxidation of volatile organic acids (VFAs) on the inner layer of anodic biofilm and facilitated acetoclastic methanogenesis on the outer layer of anodic biofilm. The generated electrons on the anode were transferred to the cathode for producing hydrogen as a substrate of hydrogenotrophic methanogenesis, rather than directly generating methane by reducing carbon dioxide through direct interspecies electron transfer (DIET) pathway. On the anodic biofilm, the syntrophic relationship between Syntrophomonas and Methanosarcina was confirmed as the main contributor of methanogenesis. Analysis of current utilization efficiency proved that a little amount of energy input could lead several folds of current utilization efficiencies in return, especially under high OLRs condition, which was anticipated to be applied into practical engineering of kitchen waste thermophilic digestion for higher economic benefits.

Metabolic effects of Fe0 on simultaneously eliminating excessive acidification and upgrading biogas in mesophilic or thermophilic anaerobic reactor

Excessive acidification and low methane (CH4) percentage are technical challenges restricting anaerobic digestion (AD) of kitchen waste, especially under high organic loading rate (OLR) conditions. Although the contribution of Fe0 powder to excessive acidification elimination and CH4 yield improvement in mesophilic AD (MAD) has been extensively reported, its impact on the thermophilic AD (TAD) process with more frequent excessive acidification problem is rarely studied. Moreover, the difference in microbial interactions and metabolic pathways between MAD and TAD reactors under Fe0 regulation was still unclear. In this study, we compared the performance of Fe0 dosing on excessive acidification elimination and biogas upgrading quality in both MAD and TAD reactors at different OLRs. The results showed that compared with excessive acidification or low CH4 percentage (less than 70%) in control reactors without Fe0 addition, the CH4 yield of MAD and TAD reactors with addition of Fe0 at OLR of 35 gVS/L were 470.88 mLCH4/gVS and 270.40 mLCH4/gVS, with higher CH4 composition of 81.32%–82.23% and 83.68%–88.48% respectively. Microbial diversity analysis showed a sharp distinction between MAD and TAD reactors with addition of Fe0. Analyses of co-occurrence networks and metabolic pathway presented hydrogenotrophic methanogenic pathway, in addition to acetoclastic methanogenesis, was dominant in MAD reactors as results of enhanced interspecies hydrogen transfer between Methanoculleus and some hydrogen producers, especially under high OLR condition. In contrast, syntrophilic acetate oxidization - hydrogenotrophic methanogenesis, which dominated by Methanothermobacter and Alkaliphilus or Pelotomaculum, was the sole methanogenic pathway in TAD reactors. The results will shed lights on the regulation mechanisms of Fe0 in AD of kitchen waste under mesophilic and thermophilic conditions, offering new insight into development of more efficient waste to energy conversion technologies.

Effect of Saline Sludge on Anaerobic Digestion of Kitchen Waste for Methane Generation: Modeling and Fertilizer Recovery

AbstractA comparative study of methane recovery by co‐digesting kitchen waste and saline sewage sludge is performed to evaluate its feasibility for waste minimization. The experiment is performed at 37 °C having a mixing speed of 100 rpm and pH of 6.49–7.5 in anaerobic mixed batch reactors. The higher salinity level of the saline sewage sludge reduces the degradation rate of kitchen waste causing an enhancement in soluble chemical oxygen demand by 133% compared with 280% when co‐digesting with the non‐saline sample. The inhibitory behavior is in line with the low volatile solid elimination efficiency of 31% of saline against 55% of non‐saline sludge. The Gompertz modeling, based on the outcomes, fits the cumulative methane generation trends quite well, with a strong correlation coefficient (>0.994). Besides, use of the non‐saline sludge results in three times more methane production than the saline sample digestion. Sludge recovery is 0.07 m3 sludge m−3 wastewater, and water recovery is 0.84 m3 m−3 wastewater. The liquid produced from the fermentation of the slurry can be used for irrigation as well as fertilization. Kitchen waste co‐digestion with both sludge samples has been proven to be a practical method for exploiting the extra digestion capacity of wastewater treatment plants currently in operation, but it is more practical for non‐saline sludge.

Enhanced anaerobic digestion of kitchen waste at different solids content by alkali pretreatment and bentonite addition: Methane production enhancement and microbial mechanism

High solid anaerobic digestion (AD) has been considered as a promising and sustainable technology for treating kitchen waste. To enhance AD of kitchen waste, alkali pretreatment and bentonite addition treatment (AP/Be) was performed on kitchen waste, and microbial community was investigated at different total solids (TS) content (10%, 13%, 19%, 22% and 25%). The results indicated that after AP/Be treatment, methane yield was as high as 198 mL CH4/g volatile solid (VS), which increased by 236% as the control. Moreover, microbial community analysis revealed that AP/Be treatment enriched bacterial microbial diversity. At TS of 10%, AP/Be treatment enhanced the hydrogenotrophic methanogens (Methanobacterium) significantly. In addition, the dominant methanogenic pathways changed at different TS content. These results demonstrated AP/Be treatment had a positive effect on methanogenesis during kitchen waste anaerobic digestion process. This study threw new insights towards enhancing kitchen waste anaerobic digestion, as well as the microbial mechanism.

Anaerobic co-digestion of kitchen waste with hyperthermophilically pretreated grass for biohydrogen and biomethane production

Anaerobic digestion of kitchen waste with grass after hyperthermophilic pretreatment was performed in semi-continuously operated reactors. The greatest methane yield of 293 NmlCH4/gVS (volatile solids) was reported for the mixture of both substrates at 55 °C with a solids retention time of 30 d and the corresponding organic lading rate of 1.72 kgVS/m3/d. In contrast, pretreated grass subjected to thermophilic digestion produced only 131 NmlCH4/gVS. However, when mesophilic conditions were applied, the digestion process turned into dark fermentation, especially visible for the mixture. Metagenomic analysis revealed the dominance Ruminococcaceae, Atopobiaceae and Lactobacillaceae at a family level in mesophilic processes, whereas Petrotogaceae, Synergistaceae, Hungateiclostridiaceae, Planococcaceae and two methanogens Methanosarcinaceae and Methanothermobacteriaceae were the most frequent microbes of thermophilic digestion. Kitchen waste can successfully be co-digested with hyperthermophilically pretreated grass at high loading rates, however the digesters must be operated at thermophilic temperatures.

Regulating effects of Fe/C materials on thermophilic anaerobic digestion of kitchen waste: Digestive performances and methanogenic metabolism pathways

This study aimed to evaluate the effects of typical exogenous materials (Fe and C) addition on the performances of kitchen waste thermophilic (55 °C) anaerobic digestion in semi-continuous system. The expression of key enzymes in methanogenesis were demonstrated by microbiological approach, and the regulating effectsf Fe and C addition on methanogenic metabolism pathway were specially explored. Four anaerobic digestion systems (TAD, TAD + Fe, TAD + C and TAD + Fe + C) were carried out, and the running period lasted for 120 days, which was divided into four stages according to organic loading rates (OLRs) from 1.05 to 4.22 gVS/L/day. From this study, C addition improved soluble polysaccharide (sPolysaccharide), soluble protein (sProtein), soluble total organic carbon (sTOC) concentrations and hydrolase (amylase, protease and lipase) activities, while Fe addition facilitated the subsequent degradation of volatile fatty acids (VFAs). As a result, the average methane yields were promoted from 478.0 (TAD) to 487 (TAD + Fe), 597 (TAD + C) and 647.3 mL/gVS/day (TAD + Fe + C), respectively. For microbial communities, C addition promoted the relative abundances of hydrolytic bacteria (Defluviitoga), while Fe addition realized the directional enrichment of Methanothermobacter, and improved hydrogenotrophic methanogenesis ratios from 30.81 % (TAD) to 52.27 % (TAD + Fe) and 64.40 % (TAD + Fe + C). According to the expression of key enzymes in methanogenic metabolism pathways, Fe addition enhanced the syntrophic acetic acid oxidation and hydrogenotrophic methanogenesis pathway, realizing the conversion of dominated methanogenic metabolism pathway from aceticlastic methanogenesis to hydrogenotrophic methanogenesis. This study is of great significance to exposit the behaviors of conductive materials during thermophilic digestion of kitchen waste.

Pyrolysis characteristics of anaerobic digestate from kitchen waste and availability of Phosphorus in pyrochar

Pyrolysis of digestate from anaerobic digestion of kitchen waste yielded combustible gas and liquid with biochar as solid product. In this study, the pyrolysis characterization of the digestate and the P availability of the obtained pyrochar were discussed. Thermogravimetry (TG) analysis showed that 15.56 % of the weight loss occurred from 600 °C to 750 °C due to CaCO3 decomposition. When the final temperature increased from 500 °C to 700 °C, the HHV of pyrogas was slightly affected elevated from 17.20 MJ/Nm3 to 18.12 MJ/Nm3, while the relative content of polycyclic aromatic hydrocarbons (PAHs) in the liquid raised from 1.36 % to 6.28 %. SMT analysis showed that phosphorus in the pyrochar was fully converted to apatite phosphorus (AP) due to an excessive Ca content. Neutral ammonia citrate (NAC) extraction indicated that the availability of P in pyrochar was significantly decreased from 7.97 mg/g at 500 °C to 2.29 mg/g at 700 °C. Overall, the results showed that pyrolysis at 500 °C was suitable to obtain high-quality fuel and pyrochar with high P availability.

Influence of the classification of municipal solid wastes on the reduction of greenhouse gas emissions: A case study of Qingdao City, China

Municipal solid waste (MSW) is an important source of greenhouse gas (GHG) emissions. Reduction of GHG emissions and resource recovery from MSW disposal units is vital for China's dual carbon strategy. Carbon emissions during the treatment of MSW from Qingdao City under different disposal modes including the classification of MSW were investigated using the life-cycle assessment (LCA) methodology and life-cycle inventory (LCI) with material flows. It was found that the carbon emissions during MSW disposal depended on the disposal modes. The traditional mode of mixed domestic waste collection + landfill had the largest carbon emission (568.98 kgCO2-eq/t MSW), while the mode of mixed domestic waste collection + incineration served as a carbon sink with a net carbon emission of −28.56 kgCO2-eq/t MSW. The carbon emissions of classification of MSW + anaerobic digestion of kitchen waste + incineration of other wastes and ideal classification of MSW modes (classification of MSW, anaerobic digestion of food wastes, resource utilization of recyclable wastes, and incineration of dry wastes.) were 4.27 and −269.34 kgCO2−eq/t MSW, respectively. Further, it was determined that improving the classification efficiency of food waste had no significant impact on carbon emissions and the reduction of carbon emission increased linearly with the improvement of waste recycling efficiency. When the recovery efficiency reaches 5%, the MSW disposal sector can be expected to achieve near carbon neutralization. This study show that appropriately separating food waste, improving the recycling efficiency of recyclable waste, and reducing the leakage rate of biogas from anaerobic digestion are three feasible strategies to reduce carbon emission from MSW disposal units through the classification of MSW.

Towards engineering application: Integrating current strategies of promoting direct interspecies electron transfer to enhance anaerobic digestion

The study present here was to integrate the current engineering strategies of promoting direct interspecies electron transfer (DIET), ethanol-type fermentation pretreatment, and conductive materials (zero-valent iron [ZVI] and graphite) supplemented, to strengthen the anaerobic digestion of kitchen wastes. Experimental results imply that after ethanol-type fermentation pretreatment, ZVI and graphite supplemented could significantly improve the methane production, transformation efficiency of organic matter, as well as impact resistance ability of systems during anaerobic digestion of kitchen wastes with a gradual increase of organic loading rate. The sludge with ZVI and graphite addition had a relatively higher capacitance and lower resistance than that without ZVI and graphite. With the concentration ratio of ZVI and graphite increasing, the evidently increased abundance of electrotrophic methanogens, Methanosarcina acetivorans, and Methanospirillum hungatei suggested that ZVI stimulated the growth of electrotrophic methanogens. Together with the enrichment of exoelectrogens capable of extracellular electron transfer (e.g., Streptococcus, Petrimonas, and Syntrophomonas species) in the presence of ZVI and graphite, the DIET between these exoelectrogens and electrotrophic methanogens might be responsible for the improved performances and stability.

Biogas as a Source of Energy and its Production from Kitchen Waste

This research was conducted to determine the efficiency of biogas generation from kitchen garbage and to present the various biogas production processes. The anaerobic digestion of kitchen waste produces a valuable energy resource, and the activity-based laboratory approach was applied for this purpose. The anaerobic breakdown is a microbiological process that produces biogas, mainly composed of methane and carbon dioxide. Biogas can be utilized as a source of energy and for a variety of other purposes. On the other hand, any potential applications require knowledge and information on the composition and quantity of components in the biogas produced. Sodium hydroxide must be added to maintain alkalinity and pH in the digester. The cow dung slurry, as well as kitchen garbage, were added to this reactor. This mixed Inoculum was combined to produce biogas in a small-scale activity. The production of biogas and methane from starch-rich and sugary material is determined on a small scale using simple digesters.

Investigating the role of different materials supplementation in anaerobic digestion of kitchen waste: Performance and microbial community dynamics

Anaerobic digestion (AD) is a promising strategy to achieve both carbon emission reduction and sustainable development. In this work, the performance and microbial community dynamics were investigated in an anaerobic digestion system using four different type of materials. The results obtained indicated that, in the presence of bentonite with the properties of high grease adsorption and alkaline, the improved performances involved in biogas production rate (996.0 mL/g-VSFW) and organic removal efficiencies (84.38%) were higher than that in the presence of biochar. However, activated carbon and zero-valent iron inhibited kitchen waste AD’s biogas production rate. Microbial community analysis revealed that the hydrogenotrophic mathanogenesis significantly increased when the additive was fed with kitchen waste digester. Bentonite increased the composition and diversity of archaea and bacteria and enriched Methanolinea and Bathyarchaeia which in turn improved AD performance. Biochar enriched Lentimicrobium capable of electron transfer to conductive material. Together with the increased abundance of Methanobacterium that could proceed direct interspecies electron transfer (DIET), AD was likely improved due to the processing of DIET with adding biochar. In this way, this study was expected to obtain a research basis for evaluating the influence of exogenous additives on kitchen waste AD.

Fate of polylactic acid microplastics during anaerobic digestion of kitchen waste: Insights on property changes, released dissolved organic matters, and biofilm formation

Polylactic acid (PLA), an alternative to petroleum-based plastics, has been widely used in food packaging and disposable tableware for biodegradable properties. As a result, PLA fragments were often mixed with kitchen waste (KW) and disposed of together. This study aimed to assess the fate of polylactic acid microplastics (PMP) when co-digested with KW. The spiked PMP did not increase the methane yield of KW but had deformation and fragmentation at mesophilic and thermophilic conditions, respectively. Identification of physicochemical properties and leachates showed that the anaerobic digestion of the KW process caused the aging and fragmentation of PMP, including the generation of irregular cracking and tiny daughter particles, the increase of oxygen-containing functional groups, and the releasing of dissolved organic matters (DOM). The thermophilic anaerobic digestion with KW enhanced the aging and fragmentation of PMP to the highest degree, which was attributed to the high temperature and enriched microorganisms (Peptococcaceae, Tepidimicrobium, and Clostridium_sensu_stricto_7) in the biofilm. Clostridium_sensu_stricto_7 was only found in the anaerobic digestion with KW, which meant the KW anaerobic digestion could contribute to the enrichment of microorganisms that promoted the PMP degradation.

Anaerobic digestion and recycling of kitchen waste: a review

About 1.6 billion tons of food are wasted worldwide annually, calling for advanced methods to recycle food waste into energy and materials. Anaerobic digestion of kitchen waste allows the efficient recovery of energy, and induces low-carbon emissions. Nonetheless, digestion stability and biogas production are variables, due to dietary habits and seasonal diet variations that modify the components of kitchen waste. Another challenge is the recycling of the digestate, which could be partly solved by more efficient reactors of anaerobic digestion. Here, we review the bottlenecks of anaerobic digestion treatment of kitchen waste, with focus on components inhibition, and energy recovery from biogas slurry and residue. We provide rules for the optimal treatment of the organic fraction of kitchen waste, and guidelines to upgrade the anaerobic digestion processes. We propose a strategy using an anaerobic dynamic membrane bioreactor to improve anaerobic digestion of kitchen waste, and a model for the complete transformation and recycling of kitchen waste, based on component properties.

Additional electric field alleviates acidity suppression in anaerobic digestion of kitchen wastes via enriching electro-active methanogens in cathodic biofilms

The aim of this study was to investigate the feasibility that the suppression of acidity in anaerobic digestion of kitchen wastes could be alleviated with additional electric field. The results showed that, the accumulation of acidity seriously suppressed methanogenesis, and no methane was detected in the electrode-supplemented digester without applied voltage. In contrast, with applied voltages of 0.6–1.2 V, the suppression of acidity was alleviated, and methane production rates reached 558–669 L/kg-volatile suspended solid that were higher than that previously reported with carbon-based conductive materials, such as granular active carbon and biochar. Although the reduced peak with a potential ranging from -0.3 V to -0.2 V close to the reduced potential of CO2/CH4 detected via cyclic voltammetry, the maximum methane yield derived from cathodic reduction of CO2 only accounted for 0.13–0.33% of total methane yield with applied voltages. Microbial community analysis showed that, Methanosarcina species were specially enriched with applied voltages, accounting for ca. 40–70% of the communities. Together with the increase in the relative abundance of Syntrophomonas species, Methanosarcina species directly accepting electrons from Syntrophomonas species via DIET might be the primary reason for alleviating the suppression of acidity. Further investigations via three-dimensional excitation emission matrix and in-situ electrochemical Fourier transform infrared spectroscopy found that additional electric field stimulated the secretion of EPS primarily comprised of protein-like substance, which might mediate the EET between Syntrophomonas and Methanosarcina species.

Dynamic Soft Sensor for Anaerobic Digestion of Kitchen Waste Based on SGSTGAT

Anaerobic digestion technology is an effective way to solve the problem of urban kitchen waste. Volatile fatty acid (VFA) is an essential intermediate product in the anaerobic digestion process. Real-time monitoring of the concentration of VFA cannot only directly reflect the anaerobic digestion process and improve resource conversion efficiency but also effectively avoid the reactor operation failure caused by acidification. Traditional soft sensors of VFA cannot adapt to the dynamic characteristics of industrial process. In this paper, a dynamic soft sensor based on spatiotemporal graph convolution network is developed. The spatial and temporal information of the anaerobic digestion process is extracted through graph convolutional network (GCN) and gated recurrent unit (GRU) respectively. With the purpose of further improving the prediction accuracy and generalization ability of the model, the adaptive adjacency matrix and graph attention mechanism are introduced into the model to solve the over-smoothing problem of GCN, and the semi-supervised learning mechanism based on manifold regularization is introduced to fully mine data information of unlabeled samples. Then, the gated unit is used to realize the information fusion of different dimensional features and the selection of model depth. At last, a dynamic soft sensor based on the semi-supervised gated spatiotemporal graph attention network is established to estimate the concentration of VFA in real time. Compared with baseline models such as GCN and GRU, the root mean square error of this model is reduced by 17.34% and 15.54%, respectively.

Kinetic study and optimization of total solids for anaerobic digestion of kitchen waste: Bangladesh perspective.

Kitchen waste from hotels and homes is one of the major problems for urban and rural environment and could be one of the best sources of renewable energy by producing biogas through anaerobic digestion. A research work was undertaken to assess the methane potential of kitchen waste at different total solids (TS) content. Kitchen wastes such as spoiled rice, brinjal, potato, papaya, tomato, fish and poultry parts etc., which are easily decomposed, were selected for this study. Batch experiments were set up under ambient temperature. Kitchen waste was added to the batch digester at different TS content (5, 7, 10, 12 and 15%) and sealed for 146 days until the gas production stopped. Substrate characteristics were analyzed before and after the anaerobic digestion. The highest methane yield was 78.12 L/kg VS at 15% TS content followed by 12, 10, 7 and 5%. Different kinetic parameters were determined using a logistic model and the model showed a good fit with the experimental results. After modelling using Minitab®, the optimum TS content for kitchen waste was found to be 14.90%.

Stabilization of anaerobic digestion of kitchen wastes using protein-rich additives: Study of process performance, kinetic modelling and energy balance

Anaerobic digestion (AD) of acidic kitchen waste (KW) streams is found to be unstable and leads to poor overall efficiency. This study assessed the effect of pongamia de-oiled cake addition on KW-AD. High acidic KW (pH: 2.00–5.00), medium acidic KW (pH: 5.00–7.00) and low alkaline KW (pH: 7.00–8.00) fed into digesters I, II and III at 10% total solids (TS) achieved biogas yields of 177.82 ± 19.30, 216.57 ± 7.42 and 280.45 ± 2.55 L/kg VS. d, respectively. Maximum synergistic effect of pongamia de-oiled cake was observed in digester I with increased methane production of 46.04% and volatile solids reduction of 11.18%. The principal component analysis and kinetic evaluation revealed that pongamia de-oiled cake addition had a positive effect on the AD parameters in all digesters. With energy efficiencies exceeded 96% in all the digesters, the study proposes the addition of protein-rich additives for KW-AD stabilization.