Monday, November 15, 2010

Can Biogas From Cow Dung Save Our Forests?

A healthy dairy Kenyan herd 


Piped biogas by Mwangi Mumero

With the rising fuel costs, farmers in Kenya have come up with ways of generating power locally and cheaply.

Biogas is increasing becoming a viable alternative to many farmers and especially those in high potential Central Highlands where dairying is common.

The blue slow flame coming from an improved cooker may fool an untrained eye. While the conventional gas cookers roar as they churn out the hot flame, this one is slow and methodical.

Yet, this cooker is running on biogas produced within 10 metres from this fabricated kitchen at Ngukura village in Kieni East District, Central Province .

At least 70 farmers in the region, affiliated to Kathuna Dairy Co-operative Society have initiated a biogas production project that has seen them boost their incomes, reduce their energy costs and generally improve their welfare.

“Biogas is cheap to produce, clean to use and has helped my family utilize the waste from our dairy herd. It has also boosted our crop production through the production of manure in form of slurry”, said Paul Mureithi, a farmer at Ngurukani Village , Kabaru location.

On his farm, Mureithi who has two health dairy cows has installed a 20 cubic metre biogas digester at a cost of Ksh 100,000.

Having constructed a zero-grazing unit where his dairy herd is permanently housed, the farmer is able to collect dung and urine used in the biogas production.

The 70 farmers are beneficiaries of a United Nations Development Programme- Global Environmental Facility (UNDP-GEF) support.

At the Mt Kenya region GEF funding is channeled through COMPACT- Community Management for Protected Areas Conservation.

COMPACT is an initiative addressing environmental concerns and community needs around the Mt Kenya Heritage Site.

“Each was farmer was required to raise 50 per cent of the total cost of installing the biogas unit. They must also have at least two dairy cows under a zero-grazing system to boost collection of animal waste”, asserted Simon Wachira, the technical adviser to the Kathuna Biogas Project for Western Mt Kenya .

Of the Ksh 50,000 each farmer has to pay, Ksh 18,800 is in form of labour costs while the Ksh 31,200 goes to the purchase of building materials such as cement, stones and sand.

For the farmers who were unable to raise the required funds, Wananchi Sacco- a local financial organization- provided loans which were to be repaid through the milk proceeds.

The Ksh 50,000 GEF support per farmer was utilized in purchasing the improved stove, internal fittings and for paying the skilled artisans needed in installation process.

“We supervise to ensure that the fitting is done well and the whole unit is functional and readily usable by farmers. We also train farmers on operations and maintenance of the biogas unit once installation is over”, said Wachira, who heads Lorian Institute of Development that is providing the technical advice on the implementation of the project.

During installation, skilled personal constructs the underground digester and connects the gas pipes to the kitchen ready for use. Polyvinyl Chloride pipes (PVC) are used to channel dung from the zero-grazing unit to the underground digester.

Pressure build-up in the digester, as gas is generated is easily monitored by farmers and regulated.

Biogas originates from bacteria in the process of bio-degradation of organic material under anaerobic conditions.

It is a renewable natural gas containing approximately 55-60 per cent methane (CH4), around 40 per cent carbon dioxide and trace amounts of other gases.

Natural gas has 99 per cent methane but it is non-renewable, a key factor for environmentalists who promote the use of biogas in many households to stem the tide of global warming.

The calorific value of biogas is about 6 kWh/, m3 – which corresponds to about half a litre of diesel.

“We can prepare all types of meals with biogas without having to substitute with fuel wood. It is also cleaner – with no smoke- leaving the cooking utensils shiny unlike when fire wood is used, leading to sooty cooking pans”, said Mrs Ruth Mureithi at her home.

Before the biogas project, Mureithi’s household would utilize at least Ksh 4,000 in form of fuel wood purchased from neighbouring farms.

The gas can also be used for lighting and power generation.

But the use of biogas in households has other benefits both to the farmer and the environment.

“It has cut my operational costs drastically as I no longer need to buy diesel to run the chaff cutter needed for chopping Napier grass. The Ksh 3000 needed monthly for diesel and labour are now my savings”, noted Mureithi, whose dairy cows produce at least 40 litres of milk daily. At Ksh 22 per litre, the farmer earns Ksh 800 daily translating to Ksh 24,000 monthly.

According to Wachira, biogas produced by two cows can run a power generator for chaff cutters and also for production of electricity for the households.

He added that the 20 cubic metre biogas digester installed in the 70 homes produces 15-30 kg of gas daily while for many households the monthly consumption is just 15 kg.

“It is possible to commercialize the production and put the gas into canisters for sale although that is not part of the installation project”, he said.

With the excess production of biogas above household needs, prospects of liquefying the gas and selling it in canister may be explored in future. Alternatively, households may connect pipes to their neighbours and sell the gas at mutually agreed terms.

With the biogas installed in many households, the demand for fuel wood had declined

In the past, women had to trek the whole day fetching fuel wood deep inside the forest, exposing themselves to attacks by marauding jumbos and buffalos. The previously wasted time can now be used in productive activities such as farming or domestic chores.

This has also reduced the pressure on fuel wood harvesting from the Mt Kenya forest- that is just 7 kilometres away.

This in turn has reduced the level of forest denudation through illegal fuel wood harvesting, logging and charcoal burning. Soil erosion is also expected to slow down as ground cover increases with reduced cutting of trees.

“Methane is a highly destructive greenhouse gas. Biogas systems utilize the gas in production of energy thereby avoiding its release into the atmosphere and contributing to global warming reduction”, observed Wachira.

Wachira intoned that households utilizing biogas systems should in future be considered for the carbon credits that many tree growers are enjoying in many parts of the world.

During the biogas production process, slurry- well fermented manure- floats out as a by-product.

“This manure provides our farm with all the necessary nutrients when used as fertilizer. Previously, we had to use at least Ksh 12,000 in the purchase of artificial fertilizers which we no longer need. This provides another form of savings on the farm with the installation of the biogas unit”, added Mureithi.

Research conducted in India has shown that fertilizer which comes from a biogas plant contains three times more readily available nitrogen than the best fertilizer made through open air digestion.

For instance, the Indian tests have shown that compost chicken manure will have in it only 1.58-2 per cent nitrogen. Manure digested in a biogas digester will analyse 6 per cent nitrogen.

Another indirect benefit of the biogas units has been improved dairying in terms milk production and quality.

Regular dung collection and cleaning to wash off the urine to the digester results in cleaner livestock herd.

As Mureithi noted, cases of mastitis and other animal ailments that thrive in unhygienic conditions are unheard off in his farm since its inception two years ago.

Human health is also bound to improve with cleaner air –with no smoke – in kitchen where biogas cookers are in use. Cases of respiratory problems such as sneezing and coughing, common in sooty kitchens, are rare.

Meanwhile a National Biogas Promoters conference was recently held in Nairobi and brought together stakeholders in the industry to assist in developing a National Biogas Promotion program. The program aims to install 8,000 units in Kenya within the next 5 years.

A COMPACT site was used for technology selection where fixed dome gas production technologies were compared against the traditional floating dome system. The key consideration included cost effectiveness, durability, gas production capacity and unit size. Units studied ranged from 6- 20 m3. (


  1. Robert MunyorokuDecember 15, 2010

    this is a nobel initiative and i would like to install the same for my parents back in the reserves. how can i get the designs for the project as well as the operation/maintenance procedures? i am from othaya and have a zero-grazing shed already

  2. Congratulations for reducing inhouse gas emissions and replacing petroleum products with biogas. I wish that you may take it a step further:human waste too if combined with animal waste might increase gas production, reduce underground water contamination from pit latrines and once the gas is gone, the slurry too is excellent fertilizer. Am from Nyanza and exploring ways of installing such an integrated system towards the end of this year.Any technical advice?