Faculty Publications
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Item Artificial neural network based modeling to evaluate methane yield from biogas in a laboratory-scale anaerobic bioreactor(Elsevier Ltd, 2016) Nair, V.V.; Dhar, H.; Kumar, S.; Thalla, A.K.; Mukherjee, S.; Wong, J.W.C.The performance of a laboratory-scale anaerobic bioreactor was investigated in the present study to determine methane (CH4) content in biogas yield from digestion of organic fraction of municipal solid waste (OFMSW). OFMSW consists of food waste, vegetable waste and yard trimming. An organic loading between 40 and 120 kg VS/m3 was applied in different runs of the bioreactor. The study was aimed to focus on the effects of various factors, such as pH, moisture content (MC), total volatile solids (TVS), volatile fatty acids (VFAs), and CH4 fraction on biogas production. OFMSW witnessed high CH4 yield as 346.65 L CH4/kg VS added. A target of 60–70% of CH4 fraction in biogas was set as an optimized condition. The experimental results were statistically optimized by application of ANN model using free forward back propagation in MATLAB environment. © 2016 Elsevier LtdItem Life cycle assessment of municipal solid waste management options for India(Elsevier Ltd, 2019) Khandelwal, H.; Thalla, A.K.; Kumar, S.; Kumar, R.Life Cycle Assessment (LCA) tool can be used for environmental assessment of Municipal Solid Waste Management (MSWM) system. The present study aims to evaluate the impact of MSWM system in Nagpur city, India under four different scenarios. i.e., composting combined with landfilling (S1), material recovery facility (MRF) & composting combined with landfilling (S2), MRF & anaerobic digestion (AD) combined with landfilling (S3) and MRF, AD & composting combined with landfilling (S4) using LCA tool. The sensitivity analysis was also performed for evaluating the influence of recycling rate of valuable resources in all the considered scenarios. The scenarios were compared using Gabi 8.5.0.79 model and CML-1A impact characterization method. S2 was found to have the least environmental impacts on global warming, human toxicity, eutrophication, and photochemical ozone creation potential categories. The sensitivity analysis indicated an inversely proportional relation between change in recycling rate and total environmental burdens. © 2019 Elsevier LtdItem Co-digestion of Food Waste and Switchgrass for Biogas Potential: Effects of Process Parameters(Springer editorial@springerplus.com, 2020) Uma, S.; Thalla, A.K.; Devatha, C.P.Abstract: Anaerobic digestion is the technology aimed at organic substrates conversion to biomethane potential. The co-digestibility performance of food waste and switchgrass at different mix ratio and the temperature is evaluated in the present study. To address this performance evaluation, the response of volatile acid groups’ viz. acetic, propionic, butyric and valeric acids, pH related to the biomethane potential. The highest methane yield observed with 1:1 FW: SG is 267 ml/g VSadded at mesophilic and 234 ml/g VSadded at thermophilic condition respectively. Methane yield has a positive response on co-digestion is confirmed by digestion performance index (DPI). Also, process parameters viz acetic and butyric acid concentrations were in the range 15–70% and 18–70% for the loadings at 35 °C and 55 °C respectively. SG showed the highest butyric acid concentration, and in contrast, the utmost acetic acid produced from both FW and SG respectively. Even though at higher acid concentrations, less significant inhibition on biomethane yields is observed during performance evaluation. Result revealed that co-digestion at 1:1 ratio yields the improved performance with FW and SG at mesophilic as well as in thermophilic condition. Food waste is predominant and achieves the second highest methane yield compared to switchgrass in single substrate digestion. This study confirms the presence of slow and fast biodegradable organic matters have an equal contribution to the biomethane yield. Graphical Abstract: [Figure not available: see fulltext.] © 2018, Springer Nature B.V.Item Effects of chemical pretreatments on material solubilization of Areca catechu L. husk: Digestion, biodegradability, and kinetic studies for biogas yield(Academic Press, 2022) Vannarath, A.; Thalla, A.K.This study aimed to understand the pretreatment-aided anaerobic digestion of lignocellulosic residues and to assess the substrate solubilization capacity of pretreatment processes. We evaluated the feasibility of biogas production using chemically pretreated Areca catechu L. (Arecanut husk, AH). AH was pretreated for 24h at two different temperatures—25 °C and 90 °C with four different chemicals viz. H2SO4 (acidic), NaOH (alkaline), H2O2 (oxidative), and ethanol in 1% H2SO4 (organosolv) under each temperature. AH solubilization assessment included analyses of parameters such as volatile solids to total solids (VS:TS) ratio, soluble chemical oxygen demand, total phenolic content, and biomass composition. Alkaline pretreatment of AH at 90 °C resulted in the maximum biogas yield of 683.89mL/gVS, which was 2.3 times more than that obtained using raw AH without pretreatment. Methane content of biogas produced using AH pretreated with 2–10% of NaOH was found to be between 71.53% and 75.06%; methane content of biogas using raw AH was 62.31%. In order to describe the AH degradation patterns, biogas production potential from pretreated AH was evaluated using bacterial kinetic growth models (First-order exponential, logistic, transference, and modified Gompertz models). The modified Gompertz and logistic models (correlation coefficient >0.99) were found to have the best fit of all kinetic models for the cumulative experimental biogas curve. We formulated a multiple linear regression equation depicting the biodegradability index (BI) as a technical tool to determine biomethane production; BI is represented as a function of biomass composition (cellulose, hemicellulose, and lignin), with a high correlation (>0.95). Based on our analyses of AH pretreatment and substrate utilization for biogas production, we propose that the biochemical composition of lignocellulosic residues should be carefully considered to ensure their biodegradability when subjected to anaerobic digestion. © 2022 Elsevier LtdItem Co-digestion of mushroom compost with switchgrass using solid-state anaerobic digester(ICE Publishing, 2023) Nair, R.R.; Thalla, A.K.; Nair, V.V.Spent mushroom compost (SMC) already broken down into smaller particles by fungal action is an ideal material for producing biogas. Two cycles of five solid-state anaerobic digesters (SS-ADs) with different mix-ratio of SMC and switchgrass (SG) were operated at feedstock-to-effluent ratio of 2 at a temperature 35 ± 2°C. The total solids concentration of the digester was kept at 17%. Initial biogas production observed during the start-up of the digester confirmed the presence of readily available extractives for digestion. In the first cycle, the highest methane yield was observed in SMC 0 (0% SMC + 100% SG) of 28.82 l/kg VS/d and the lowest yield was observed in SMC 4 (100% SMC + 0% SG) as 10.32 l/kg VS/d. The substrate containing 100% SG (SMC 0) recorded the highest cumulative biogas yield of 295.43 l/kg VS in 63 days. The digesters with higher SMC fraction showed lower methane production, low pH value and high volatile fatty acids content upon decomposition. The SS-ADs having SMC/SG of 50 : 50 showed more than 2 times methane production in comparison with SS-ADs having SMC as sole substrate. An estimation of volumetric productivity also established a linear relationship with the SMC/SG ratio. © 2023 Emerald Publishing Limited: All rights reserved.