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Waste No waste: High Time to Embrace Biogas

Besides being a good source of bioenergy, biogas technology is also an excellent source of organic fertilizer. A 2018 biogas user survey confirmed that 95% of users also noticed an increase in productivity on farmland due to the use of bio-slurry as fertilizer. In light of this, the question still remains as to why people are still not fully on board with adopting bioenergy generation?

The recent Intergovernmental Panel on Climate Change (IPPC) report 2021 has a serious warning to all the policymakers of the world and announced humanity is at stake as climate change is at its peak and is already approaching irreversibility for centuries to come. The UN Secretary General wrote about the deafening risk alarms as greenhouse gas emissions are evidently choking the whole world, putting all the people in a perilous state.

Efforts must be centered on cutting methane emission to dampen temperature rises and reach net zero emission well before 2050.

Signs of climate change have been indisputable in Nepal. During the last week of March 2021, Nepal witnessed awful air quality as smoke and haze took over the country. The reason – scant rainfall during the three winter months led to wildfires throughout the country. Furthermore, the country has frequently started experiencing extreme hydrometereological events, resulting in floods, landslides, and debris flow.

Therefore, in the context of changing climate, sole dependency on energy from hydropower or imported fossil fuels poses social, environmental, and economic threats for Nepal.

Nepal has more than half-a-century experience with biogas technology.

With more than 431,000 domestic biogas plants installed, the contribution of biogas energy for cooking should be around 8 per cent, although data from the Central Bureau of Statistics shows biogas contributes only 2.4 per cent.

This huge differences on the installed and functional biogas plants suggests a need of thorough study.

Statistical information published by the Ministry of Agriculture and Livestock Development in 2019/20 reports that there are more than 103 million livestock and poultry in Nepal, from which the estimated manure generation is nearly 188,000 tons per day. This, according to the theoretical estimation made by the Renewable and Sustainable Energy Laboratory (RSEL), Kathmandu University, could produce biogas equivalent to about 3,165 million m3 per year, or about 110 million LPG cylinders (1 cylinder =14.2kg LPG).

Currently LPG consumption in Nepal is about 30 million cylinders. This provides undeniable evidence of greater possibility for a circular economy as well as resource recovery with biogas technology. Not limiting to energy generation, biogas energy in Nepal, if it were to replace LPG, would prevent 4.4 megatons of CO2eq emissions per year, contributing hugely to net zero emission in the years to come. Feeding biodigesters with optimized ratio of multiple feed stocks help stabilize the anaerobic digestion process and increases biogas yield by 50- 100 per cent. However, this is scarcely practiced in household biodigesters here. Although a few largescale commercial biodigesters seem to be using multiple substrates, such as poultry waste, press mud and cow manure, these digesters are not introducing abundantly available wastes such as agricultural residue and organic faction of solid wastes.

Nearly 1.7 million tons of organic wastes are recovered per year from municipal solid waste generated in Nepal, which has a potential to produce 68.7 million m3 of biogas per year.

Additionally, nearly 6.2 million tons of crop residues are produced in Nepal with a biogas potential of about 2,116 million m3 per year. If these wastes are incorporated in the biogas generation cycle, the total biogas production potential would be nearly 200 million LPG cylinders equivalent.

Biogas technology is not only restricted to bioenergy generation but is also a good source of organic fertilizer. The biogas user survey 2018 revealed that nearly 95 per cent users observed increased productivity on the farmland due to the use of bio-slurry as fertilizer. But the question remains: why is the nation still not fostering bioenergy generation to its potential? Almost all household biodigesters installed in Nepal are of GGC (Gobar Gas Company) 2047 concrete model, mostly of 4-10 m3 plant sizes. Some minor improvements have been made to the GGC 2047 design, however, a significant reduction (50-80%) of biogas yield during the winter due to low ambient temperature remains a problem.

Biogas leakage in GGC 2047 plants is also a problem.

Absence of adequate scientific study on the technical performance of the biodigesters and credible users' feedback are limiting technological development of household biogas plants in Nepal.

Household biogas installation in Nepal is mainly subsidy driven. The installation trend increases only through initiatives taken by different programs and has yet to take the shape of a market-driven approach.

Under Schedule 8 of the Nepali Constitution, local level authorities have been given jurisdiction over Alternative Energy and Environmental Protection. The adoption of bio-gas technology is, therefore, within their dominion of authority.

Furthermore, Solid Waste Management Act 2068 has clearly transferred power to the local bodies for waste management: from waste collection to recovery.

Local governments should realize this on-hand opportunity and utilize it for energy generation.

Towards technical improvisation, the local governments and provinces should also consider working with universities and research institutes towards design improvement, adaptation, and development of new biogas digesters.

Research, development and technological dissemination and support from the central, provincial, and local government are a must to strengthen the bioenergy sector in the country.

Furthermore, improvement of the operational temperature of a digester by incorporating indigenous temperature enhancement approaches, such as insulation and greenhouse could improve biodigester performance in hilly and mountainous region.

Lohani is professor at KU; Dhungana is a research scholar at RSEL

A version of this article appears in the print on September 9 2021, of The Himalayan Times.

Article cited from: https://tinyurl.com/2jmb5a6d