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

This article aims to comprehensively review the anaerobic digestion (AD) process utilising the organic fraction of municipal solid waste (OFMSW) substrate. The AD of OFMSW has received considerable attention due to its significant energy and nutrient recovery as well as its greenhouse gas (GHG) mitigation potential. AD is a biological process involving treating and stabilising organic matter in the absence of oxygen accomplished by a consortium of microorganisms and occurs under hydrolysis, acidogenesis, acetogenesis, and methanogenesis phases. The hydrolysis phase is recognised as the primary rate-limiting step. Thus, exploring the ways to speed up the hydrolysis process will maximise biogas production. The key factors affecting the digestion efficiency include feedstock quality, pre-treatment process, design and selection of digestion process and process conditions including pH, temperature, carbon to nitrogen (C: N) ratio, organic loading rate and hydraulic retention time. The review reveals that solid-state anaerobic digestion (SSAD) is best suited for OFMSW due to its high solid concentration (>15%) and better process performance. The continuous digestion with thermophilic temperatures was found to be the best condition for high solid AD process. The plug flow and continuous stir tank reactors were the best performing options to control the biological conditions for the digestate post-treatment. Proper selection of the parameters for the whole process is crucial in ensuring process feasibility and economic sustainability of AD of OFMSW. The study revealed that the AD of OFMSW could play a significant role to mitigate waste and waste-related problems.

A comprehensive review on anaerobic digestion of organic fraction of municipal solid waste

Tourist arrivals, energy consumption and pollutant emissions in a developing economy–implications for sustainable tourism

Waste-to-energy generation technologies and the developing economies: A multi-criteria analysis for sustainability assessment

Prioritizing and overcoming biomass energy barriers: Application of AHP and G-TOPSIS approaches

Anaerobic digestion of biowastes in India: Opportunities, challenges and research needs.

Waste-to-Energy Options in Municipal Solid Waste Management A Guide for Decision Makers in Developing and Emerging Countries

Remote communities in the Nepalese mountains above 2500 m a.s.l. belong to the most precarious in the world. Inhabitants struggle for the minimum in terms of safe drinking water, food and sanitation. Reliable, affordable and clean energy for cooking, room heating and warm water for personal hygiene is often lacking and dependency on firewood very high. The remoteness and unlikeliness of electric grid connection in the coming decades make a diversified energy supply from renewable local resources crucial. Small-scale anaerobic digestion (AD) of organic substrates has been used for long in rural areas of developing countries to produce biogas as energy source and recover residue as organic fertilizer. AD is challenging at high elevations due to year around lower ambient temperatures and lower annual biomass production per area compared to lowlands. Nevertheless, examples of operational household AD exist even above 3000 m a.s.l. in the Andes. Here we compare firewood consumption with biogas potential from organic substrates in a community with 39 households at 3150 m a.s.l. in Jumla District, Nepal. In five households with varying numbers of members and animals kept, mean firewood use and its energy content per capita (cap) and day (d) were 2.1 kg or ca. 25 MJ in spring and 2.3 kg or ca. 28 MJ in winter. Easily available substrates include cow, sheep and horse dung from overnight shelters and human excrements from pit latrines, amounting on average to 1.7 kg wet weight (kgww ) cap−1  d−1 in spring and 2.2 kgww  cap−1  d−1 in winter. Adjusted to normal conditions (Nm3 at 0 °C, 1013.15 hPa), these substrates yielded on average 0.08 Nm3  cap−1  d−1 biogas in spring and 0.12 Nm3  cap−1  d−1 in winter (35–60% methane content) in biochemical methane potential (BMPs) tests at 36 °C. This could provide up to 60% of basic cooking needs on average and up to 75% in a “typical” household in terms of members and animals kept. Of the overall thermal energy needs including also room heating ca. 10–20% could be covered, substituting 0.1–0.4 (mean: 0.2) kg firewood cap−1  d−1 . If only animal dung and human excrements are considered, no competition for resources arises as residues can still be used as organic fertilizer. This study supports the design and introduction of planned pilot digesters integrated into on-going community development including pit latrines for substrate availability, greenhouses as possible way of thermal insulation, and planned pico-hydropower plants to use excess electricity during the night for digester heating.

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Potential of biogas production to reduce firewood consumption in remote high-elevation Himalayan communities in Nepal

Methane potential from municipal biowaste: Insights from six communities in Maharashtra, India.

Remote, high-altitude villages in the Nepalese Himalayas belong to the poorest and most underdeveloped communities in Nepal, with many still years/decades away from access to electricity. It is common that first-time electrification of these villages is through a 15–50 kW micro-hydropower (MHP) system, subsidized by the Nepal government. The majority of the so far installed MHP systems in the region are however within 3–12 months after they have been commissioned either inoperable due to premature equipment breakage, inappropriate operation, and absent maintenance or do not provide the expected power output. No mechanism is put in place to build an operating and maintenance fund, further putting the longevity of the system at risk. The “dreams” of villagers, promised by such development projects, remain unfulfilled and most often shattered. This paper describes a modular pico-hydropower (PHP) system (1–5 kW) being pursued in the village of Moharigaun in the Jumla district of Nepal whose capacity can be expanded as the village’s power demand, population, and ability to operate and maintain the system grow. This modular PHP system provides reliability through redundancy and the elimination of some of the more maintenance-prone components. The turbine water and electricity delivery infrastructure are buried to protect them from the elements and potential mischief. Most importantly, a prepayment system with remote disconnect capability ensures households pay into an operations and maintenance fund. The whole village community is actively involved in each step of the project (planning, implementation stages, and training), so they will develop a strong ownership for their PHP system. Further, local people, chosen by the community, will be trained to properly operate, administer, and maintain the PHP system.

Thomas Gross

Papers

Anaerobic digestion of biowastes in India: Opportunities, challenges and research needs.

Waste-to-Energy Options in Municipal Solid Waste Management A Guide for Decision Makers in Developing and Emerging Countries

Potential of biogas production to reduce firewood consumption in remote high-elevation Himalayan communities in Nepal

Methane potential from municipal biowaste: Insights from six communities in Maharashtra, India.

Modular Pico-hydropower System for Remote Himalayan Villages