Sustainable utilization of biomass resources for decentralized energy generation and climate change mitigation: A regional case study in India.

Clean energy transition via utilizing biomass resources has been projected as an important climate change mitigation strategy. A vital characteristic of biomass is its localized nature; therefore, bioenergy utilization should follow decentralized planning. Agrarian countries like India can take benefit of its large agricultural biomass waste pool to produce clean renewable energy. However, prior knowledge of spatio-temporal distribution, competing uses, and biomass characteristics are necessary for successful bioenergy planning. This paper assesses biomass resource and its power generation potential at different agro-climatic zone levels in the state of Rajasthan, India considering crop residue biomass (25 different crop residues from 14 crops) and livestock manure (from cattle, buffalo, and poultry). Uncertainties associated with the availability of biomass and the power generation potential are assessed for each agro-climatic zone under different scenarios. Greenhouse gases (GHGs) emissions from biomass-based power generations are also estimated and compared with biomass-equivalent coal power plants. It is observed that the annual biomass power potential of Rajasthan is 3056 MW (2496 MW from crop residues and 560 MW from livestock manure). Scenario analysis suggests that the potential varies from 2445 to 6045 MW under different biomass availability and power plant operating conditions. Annual GHGs emissions due to biomass power generation is 5053 kt CO2eq. Replacing coal-based power with biomass power would result in annual GHGs savings of 11412 kt CO2eq. The paper also discusses various carriers and barriers viz. logistics, institutional, financial and technical in setting up decentralized bioenergy plants. Outcomes of the present study are expected to assist renewable energy planners in India.

Valorization of agricultural waste for biogas based circular economy in India: A research outlook.

Environmental deterioration and the need for energy security are intrinsic problems linked with the linear economy based on fossil fuels. Recently, a transformation to a sustainable circular bio-economy is being experienced where biomass waste is being valorized for energy production as well as minimization of waste and greenhouse gas emissions. The agricultural waste, generated in vast quantities in India is a prospective feedstock for biogas production. Agri-waste to biogas based circular economy requires an integration of agri-waste management, biogas production and utilization and policy support. This paper comprehensively discusses the potential of biogas production from agricultural waste, its upgradation and utilization along with the government initiatives, policy regulations. In addition, barriers that impede the development of an efficient agri-waste to biogas based circular economy, and the future research opportunities to meet the growing needs for agri-waste management, energy production and climate change mitigation are discussed.

Identification of potential waste seeds of wildly growing tree species for the production of biogas.

In this experimental study, seeds of wild tree species namely Acacia nilotica, Prosopis juliflora, Albizia lebbeck, and Leucaena leucocephala were explored as potential feedstocks for anaerobic digestion and compared with cattle manure which is a commonly used feedstock. These seeds occur abundantly as waste biomass in tropical and subtropical parts of Asia, Africa, and the USA. An experimental investigation was carried out in large 300-L anaerobic digesters under semi-continuous feed mode for 90 days. The average specific methane production yield observed was 0.208 Nm3/kg volatile solids (VS) for A. nilotica, 0.227 Nm3/kg VS for P. juliflora, 0.219 Nm3/kg VS for A. lebbeck and 0.210 Nm3/kg VS for L. leucocephala which was found to be higher than cattle manure's yield of 0.146 Nm3/kg VS. Experimental analysis revealed an average methane content of more than 52% for all the seeds and a total volatile solid mass removal efficiency of 41.60% for A. nilotica, 44.19% for P. juliflora, 43.76% for A. lebbeck, and 41.41% for L. leucocephala which was higher than 29.7% for cattle manure. The experimental investigations showed that they have a higher biogas production potential than cattle manure indicating their huge scope and suitability as alternative feedstocks, and their use can also mitigate the ecological risk seeds pose by growing into invasive trees.

Enhanced biogas production from municipal solid waste via co-digestion with sewage sludge and metabolic pathway analysis.

The present study intends to evaluate the potential of co-digestion for utilizing Organic fraction of Municipal Solid Waste (OFMSW) and sewage sludge (SS) for enhanced biogas production. Metagenomic analysis was performed to identify the dominant bacteria, archaea and fungi, changes in their communities with time and their functional roles during the course of anaerobic digestion (AD). The cumulative biogas yield of 586.2 mL biogas/gVS with the highest methane concentration of 69.5% was observed under an optimum ratio of OFMSW:SS (40:60 w/w). Bacteria and fungi were found to be majorly involved in hydrolysis and initial stages of AD. Probably, the most common archaea Methanosarsina sp. primarily followed the acetoclastic pathway. The hydrogenotrophic pathway was less followed as indicated by the reduction in abundance of syntrophic acetate oxidizers. An adequate understanding of microbial communities is important to manipulate and inoculate the specific microbial consortia to maximize CH4 production through AD.

Characterization of leaf waste based biochar for cost effective hydrogen sulphide removal from biogas.

Installation of decentralized units for biogas production along with indigenous upgradation systems can be an effective approach to meet growing energy demands of the rural population. Therefore, readily available leaf waste was used to prepare biochar at different temperatures and employed for H2S removal from biogas produced via anaerobic digestion plant. It is found that biochar prepared via carbonization of leaf waste at 400 °C effectively removes 84.2% H2S (from 1254 ppm to 201 ppm) from raw biogas for 25 min in a continuous adsorption tower. Subsequently, leaf waste biochar compositional, textural and morphological properties before and after H2S adsorption have been analyzed using proximate analysis, CHNS, BET surface area, FTIR, XRD, and SEM-EDX. It is found that BET surface area, pore size, and textural properties of leaf waste biochar plays a crucial role in H2S removal from the biogas.