Biogas production from livestock manure

GLOBAL ENERGY demand is growing rapidly and approximately 88% of this demand is met by fossil fuels at present time. At the same time, concentration of greenhouse gases (GHGs) in the atmosphere is rising rapidly, with fossil fuel-derived CO2 emission being the most important contributor. In order to minimize related global warming and climate change impacts, GHG emissions must be reduced to less than half of global emission levels of 1990. Another important global challenge is the security of energy supply because most of the known conventional oil and gas reserves are concentrated in politically unstable regions.

In this context, biogas from kitchen wastes, crop residues, energy crops and animal manure will play a vital role in future. Biogas is a versatile renewable energy source which can be used for replacement of fossil fuels in power and heat production and can also be used as gaseous vehicle fuel. In rural areas of developing countries, various cellulosic biomass (cattle dung, agricultural residues, etc.) are available in plenty which have a great potential to provide the energy demand, especially in domestic sector.

Biogas has been evaluated as one of the most energy-efficient and environmentally beneficial technology for bioenergy production. It can drastically reduce GHG emissions compared to fossil fuels by utilization of locally available resources. Germany has become the largest biogas producing country in the world. By properties, biogas is very similar to natural gas and is composed of Methane (50-75%), Carbon dioxide (25-50%), Nitrogen (0-10%), Hydrogen (0-1%) and Hydrogen Sulphide (0-3%). Biogas is also being used in power generators for electricity production around the world as renewable fuel source.

In addition, biogas could potentially help reduce global climate change. In fact, one cow can produce enough manure in one day to generate 3 KWh of electricity; while only 2.4 KWh of electricity is needed to power a single 100 watt light bulb for one day. Furthermore, by converting cow manure into methane biogas instead of letting it decompose, we would be able to reduce global warming gases by 99 million metric tons or 4%.

Potential of Biogas Production in Pakistan:

Biogas plants are popular in Pakistans neighborhood and even developed countries. The 30 million rural households in China that have biogas digesters, enjoy a lot of benefits i.e. saving fossil fuels, time collecting firewood, money, cooking time, protecting forests, improving hygienic conditions, producing high-quality fertilizer, enabling local mechanization and electricity production and improving the rural standard of living and reducing air and water pollution.

There are almost two million bio-gas plants in India and the facilities have been built even in UK and US through official patronage. Around 89 such plants in the US are consuming 13% or 95000 tons of waste to produce about 2500 MW of electricity that suffices for 2.3 million households. In Nepal, where 80 percent population lives in rural areas with no electricity, an NGO has installed around 210,000 biogas plants to provide biogas for cooking and lighting. In North America, utilization of biogas can generate enough electricity to meet up almost 3% of the continents electricity expenditure.

In Pakistan, biogas produced from small-scale digestion plants is called “Gobar Gas” and it is estimated that such facilities exist in hundreds of thousands in Pakistan, particularly in North Punjab due to the thriving population of livestock. Government of Punjab is also taking initiative to install biogas plants to produce electricity and help people to get rid of load shedding. An average sized animal produces 10-15 KG of dung on daily basis and this dung is either sold at very cheap rates as raw manure or the farmer uses it as manure for his own lands. This dung can easily be used as raw material to produce biogas and thus generate power to run tube wells, electricity and gas for cooking.

There are currently around 74 million large animals in Pakistan. Even if 50 percent of the dung produced by these animals is collected, it can produce around 19 million mᶾ of biogas a day. It will also produce 27 million tons of bio-fertilizer per year which can boost agricultural productivity. As per Pakistan Centre for Renewable Energy Technologies (PCRET) report, a family size biogas plant annually produces energy equivalent to 10056 Kg wood, 22200 Kg animal dung, 1104 litre kerosene oil, 540 kg LPG or 9000 KWh of electricity. In Landhi Cattle Colony Karachi alone, around 0.35 million cattle-heads are kept in a 3 km area which produce thousands of tons of waste but 80-90% of this waste is thrown in the sea.

A Canadian firm Highmark Renewables with the help of KESC, plans to establish worlds biggest biogas plant at the cost of around $70 million that would produce up to 30 MW of power. Any farmer having at least three animals can establish this plant with a one-time investment of Rs 40,000 to 50,000. Gas produced in a small bio-digester which contains about 20 kg of dung would be enough to meet the fuel requirements of a small family. Based on these calculations, a bio-digester for any number of animals can be designed.

Despite huge potential and benefits, biogas technology has not been given due attention in Pakistan. With inflation, energy shortage is aggravating with each passing day, thus, this type of gas can be used both for cooking and power generation and its residue as fertilizer. This will ultimately decrease domestic fuel budget, deforestation and pressure on national power grid. It can also contribute towards sustenance of ecosystem and conservation of biodiversity in the country.

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