Feature

Biogas project in Malawi leads to other benefits


M.G.G. Chagunda, D.J. Roberts, M.L. Chitawo and V. Kasulo

A small-scale underground biogas plant in Malawi that has recently been established in an effort to mitigate climate change can also improve food security and livelihoods in rural Malawi, if well tapped. Mizeck Chagunda, geneticist and expert in livestock, agriculture and environment, explains.

The importance of dairy farming to Malawi

Smallholder dairy production is an important agricultural activity in Malawi, producing valuable products and providing a regular income for poor households. The country is still deficient in milk, the current processed quantities mainly going to urban and peri-urban consumers. Improving small-scale dairy production would empower small-scale farmers economically through increased sales in rural areas.

Although the capacity of the five major dairy processors is 126,000 litres of milk per day, they currently process only half of that volume. Thus, scaling up the production and quality of milk would directly contribute not only to nutritional and food security, but would significantly contribute to accelerating economic growth in the country, experts believe.

Although smallholder dairying is one of the priority areas for development by the Department of Animal Health and Livestock Development, the contribution potential of dairying to sustainable livelihoods remains untapped. And one of the major challenges facing the rural Malawian dairy household is availability of energy, a problem that biofuels may just have a solution for.

Firewood as an energy source

At present, Malawi's utilisation of energy resources is heavily dominated by firewood. Firewood, which is mainly sourced from indigenous forests, provides 93% of all household energy needs.

Current annual household consumption of firewood and charcoal stand at some 7.5 million tonnes, exceeding sustainable supply by about 3.7 million tonnes. Poverty and population growth in the country place escalating pressures on Malawi's indigenous forests, and are hence destroying the much-needed and fast-depleting carbon sink.

Could biogas be the answer?

In an effort to preserve the carbon sink and switch to a cleaner and more efficient alternative to firewood, a small-scale underground biogas plant has been established by the Test & Training Centre in Renewable Energy Technologies (TCRET) at Mzuzu University, one of the public universities in Malawi. It can be found at Ruguwa Mnhlanga Village, a rural village north east of Mzuzu City in Malawi, and the project is being funded by the British High Commission in Malawi.

By the end of the project in 2011, there will be 12 biogas digesters.

The location of the plant was determined based on the following criteria so as to maximise plant efficiency and impact:

  • Households in the area relied on charcoal and firewood as the only sources of energy for thermal applications;
  • Households in the area were engaged in the charcoal business as a source of income;
  • The manure from the herd of dairy cows could be utilised as feedstock in small-scale biogas digesters.

Capacity and benefits

Each digester uses manure from 4-6 cows and produces between 3m3 of gas/day when working at 70% efficiency. It is estimated that the manure from 6 adult cattle will produce 3m3 of gas per day, enough to operate 3 kitchens for 4 hours daily.

The main objective of the plant was to provide an alternative energy source to carbon, and in this respect it has been successful - already reducing demand for firewood, leading to the preservation of important woodlands and the natural carbon sink. It is envisaged that using biogas from the 12 plants for cooking will save (annually) 444 hectares of natural forests, from which firewood and charcoal are freely collected.

A second major objective was to make a positive impact on the smallholder dairying industry in the area. With this plant, there is potential for better animal health due to reduced time constraints, improved forage production, increased milk production (and thereby increasing income), all leading to improved living standards of the smallholder dairy farmers.

A third key benefit is that the plant uses manure as feedstock which would otherwise anaerobically ferment, causing methane emissions. Together with enteric fermentation this form of methane production comprises about 30%-40% of the total anthropogenic methane emissions, a major reason for global climate change. Thus, the biogas plant can also indirectly contribute to mitigating climate change, a huge advantage over firewood and charcoal fuel.

Other spin-off advantages from this project include:

  • Possibility of bottling extra gas (into compressed cylinders) and selling in nearby towns for provision of additional income to farmers, and reduction in the demand for wood and charcoal in towns;
  • Improvement of milk quality: It is estimated that 17% of milk in Malawi is rejected by the milk purchasers due to unacceptable quality. This may be due to disease, poor hygiene during milking or transportation. However it is important to cool milk to reduce bacterial activity. Milk could be cooled by one, or a combination of, three methods: Either using water, provided it was colder than milk, in a heat exchanger (the water could still be collected and used for other purposes); using damp cloths to cover the milk storage containers (the evaporation of the water would help to cool the milk); using some of the gas produced to power a refrigerator;
  • Production of manure: The digester slurry, which is a by-product of the biogas production process, is known to be a better manure compared to raw manure from cattle. The digester slurry can be used as manure for forage production, thereby improving animal feed.
     

 

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Comments

collen said

10 January 2010
well done for putting this in the magazine..by the way I am at Loughborough University and I should be going back to Malawi this September

REF Editor said

03 September 2009
Thanks for the feedback on our subediting guys! We have tightened up that paragraph with the help of Mizeck. All the best...

Mizeck said

03 September 2009
Thanks Steve for the observation. There indeed must have been a little mix-up in that statement in the final version of the article. Originally the article was very long, I guess in trying to keep up with space some issues were 'lost in translation'. That aside, Kerne's interpretation is right. Rotting manure would freely release methane while the biogas plant captures the methane which is then utilised at a household energy source. Thanks again.

Karne said

03 September 2009
I must admit I agree with Steve's comment but I interpreted that line "A third key benefit is that the plant uses manure as feedstock which would otherwise anaerobically ferment in cattle, causing methane emissions" to refer to the rotting of the manure if it was left on the ground - this would release methane. Instead the methane can be captured. Any thoughts??

Steve said

02 September 2009
The statement "A third key benefit is that the plant uses manure as feedstock which would otherwise anaerobically ferment in cattle, causing methane emissions " is biologically wrong.
In crude terms the use that is made made of cow shit after it leaves the cow has no impact on the effects of that shit inside the cow or the extent that it causes the cow to fart.
Futhermore, the production of methane in the digestive system of the cow occurs in the early stages of digestion of grass in the cows multiple stomachs resulting in methane emissions with the air that the cow breathes out. In other words - Cows burp methane they don't fart it.

My apologies for the simple crude terminology.


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