Biogas helps prevent deforestation

The rural population in Pakistan primarily uses firewood and cow dung cakes as sources of energy for cooking and heating as they are easily available and also economically viable.

The increase in population has exacerbated the pressure on forests, resulting in rapid deforestation and loss of soil fertility.

Alternative sources of domestic energy like kerosene oil, liquefied petroleum gas (LPG) and coal are not only costly but are also not readily available in rural areas. However, biogas energy from animal dung has proved to be a viable source of decentralised energy that offers a cost-effective solution to the rural communities.

Pakistan, despite its enormous potential, is an energy-deficient country. Its total primary energy consumption is estimated at around 62 million tons of oil equivalent (MTOE).

Of this, 85% is met from non-commercial energy resources like biomass, firewood, charcoal and cow dung while only 14% is acquired from commercial energy resources. Consumption of non-commercial energy is mostly concentrated in the household sector, particularly in rural areas.

However, the reliance on traditional non-commercial energy sources creates certain problems with regard to sustainability, mainly in terms of social and environmental concerns.

In rural areas, most of the energy expenditure is on arranging fuel for cooking as around 45% of their energy expenditure goes to solid biomass fuels such as firewood, agricultural residues and cow dung cakes.

An additional 12% goes to LPG, kerosene, natural gas and candles used for cooking and lighting. Cow dung cakes constitute 5.5% of the energy requirement in rural Pakistan.

Over 80% of the rural population is using firewood collected from nearby forests and farmland as a source of domestic energy. Annual firewood consumption is 0.52 m³/ capita in the study area.

Assuming the volume of an average size tree is 1.0 m³, two individuals would consume one standing tree in a year. Therefore, a rural household with an average household (HH) size of eight family members will consume four trees in a year.

This is a major cause of deforestation, which is increasing air pollution and greenhouse gas (GHG) emissions into the atmosphere.

Biogas energy thus emerges as a viable replacement of firewood in rural communities. Crucially, biogas is a clean and environment-friendly source of energy that communities prefer for its social acceptability and economic viability.

Biogas is produced as a result of decomposition of organic matter and is a mixture of various gases including methane (50-75%), carbon dioxide (25-50%), nitrogen (2-8%), water vapours, trace levels of hydrogen sulphide, ammonia and hydrogen.

Methane is inflammable and serves as a source of energy mostly used in the domestic sector in raw form. Biogas produced in a digester is collected in a gas holder at the top of digester body.

Organic materials needed for producing biogas include animal dung, biomass like agricultural waste and municipal waste.

Biogas production in an anaerobic digester using animal dung is an environment-friendly source of energy production as it is carbon neutral compared to the burning of firewood.

Being a decentralised source of energy, it is very easy to develop a biogas plant somewhere close to raw material.

Biogas technology also produces a large quantity of decomposed organic manure, which is the by-product of the anaerobic digestion of animal dung. This is a rich and cheap source of soil fertility that can replace the costly and hazardous chemical fertilisers.

Controlling the GHG emissions into the atmosphere helps Pakistan to enforce the provisions of the United Nations Framework Convention on Climate Change and the Paris Agreement that Pakistan has already ratified.

In addition, the replacement of chemical fertilisers with the decomposed organic manure would help the country meet its obligations under the Persistent Organic Pollutants Convention that it has ratified.

Biogas technology being anaerobic is eligible for earning carbon credits under the Clean Development Mechanism (CDM). Therefore, biogas energy technology is highly sustainable as it offers three major benefits.

These are biogas as a source of energy, as a provider of decomposed organic manure and as a source of earning carbon credits under CDM.

In addition, installation of biogas digesters helps in the better management and disposal of animal waste.

From an ecological perspective, biogas systems have helped reduce the pressure on forests, which in turn has important implications for sustainable forest management.

The use of bio-slurry has reduced the depletion of soil nutrients by providing organically rich nutrients, resulting in increased crop yield.

Biogas technology is successfully used all over the world. China has over 5 million anaerobic domestic biogas digesters and India has also installed over 2.5 million digesters for domestic use. The technology is spreading rapidly in other countries across the globe and millions of domestic biogas plants are in the pipeline.

The writer is a PhD in Natural Resources Management and has served at provincial, federal and international organisations as an environmental consultant

Published in The Express Tribune, September 19^th, 2022.

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