Uganda Biogas Project

John Njendahayo writes:

AN AMAZINGLY SIMPLE, CHEAP, RELIABLE AND COST EFFECTIVE SOURCE OF ENERGY THAT HAS BEEN KEPT AWAY FROM PEOPLE FOR YEARS!

Biodigester

Did you know that;

One cow can produce enough manure in one day to generate three kilowatt hours of electricity? Read on…..

biodigester-sketch-2

Introduction:

For some years now, I have been looking for ways to sort out my energy problems at the Link  Centre, the Campsite in Kyambura and in my rural village. Electricity bills are high all over Uganda and continue to rise. At the campsite the cost of installing electricity and connecting to the national grid is unaffordable and close to £1000.

Travelling across Uganda has also made me realise how badly human activities are affecting the environment: cutting down trees for fire wood, for burning bricks and for timber. Uganda has changed so much in the last 20 years and unless something is done to avert this, Ugandan is doomed!

A frustrated young man!

Frustration and failure to able to do anything about all the above, prompted me to hunt for alternatives. It is indeed true that necessity is the mother of invention!

History of biogas in Uganda

A story about a former vice president of Uganda who was invited to China in the mid 80s to look at Chinese agricultural systems inspired me even more. The story goes that one day the vice president was invited by the Chinese government.   He was taken to visit different families in different parts of rural China.  There, he found village people using biogas out of Bio digesters feed on cow dung! They were able to use the same gas to power machinery, power lights, for cooking, refrigeration and even in incubators! Much of Uganda was still in the dark by then and one could easily say that still is in the dark. Very few people know about the above technology and no wonder why much of rural Uganda goes pitch black by 7 PM.   Only a few candle lights can be seen here and there!

Upon his amazement, the vice immediately requested the Chinese government to provide him with two experts to accompany him to Uganda. There, they would help teach at least two Ugandans on how the technology worked.   The duo arrived some time in 1985.   Unfortunately the war was raging on at the time and so the two Chinese experts had very little time in Uganda.   While sharing their expertise, the war became even intense and wanted to go back immediately.   However, the vice president became rather angry that the two Ugandans in the hands of the Chinese experts had not yet grasped the workings of biogas.   They had only learned how to dig holes where the bio digesters would be built! Although the rebels were then approaching Kampala (6 miles away from the city centre) the vice president could not allow the Chinese to go back until the two Ugandans knew exactly what to do! The Chinese had no choice then apart from doing exactly what they had to do-teach the two Ugandans all they knew and get out of Uganda as soon as possible.

Well, that was exactly how the very few Ugandans became introduced to biogas technology.   It has now been 26 years since the Chinese arrived in Uganda to introduce the technology but for some bizarre reasons, very few Ugandans use this amazing technology.   Very few people know about it leave alone how it works! What went wrong?   Why has the government kept quite about it?  Is there a hidden agenda or is it purely due to the failure by researchers to disseminate research information to benefit the public?   Or is it just an economic problem?   These questions leave me rather puzzled and angry!

My hard search for solutions led me to one of the surviving experts on biogas technology in Uganda.   He now lectures at Makerere University and we are now good friends and we are sharing a great deal on biogas technology. What hasn’t been achieved in 26 years, I am hoping, can be achieved in less than five years.

biogas-2

From months of research and final guidance from my professor friend, I am proud of knowing how bio digesters work and how they are constructed! The task now is for me to be able to share this information with hundreds of other Ugandan families who stand a chance to benefit from the technology.

In developing countries (Uganda included) – where food is scarce and reliable energy supplies are even scarcer – necessity often becomes the mother of invention. It is possible for farmers to use human urine and excreta – mixed in with banana peels, algae, water hyacinth, cow dung and poultry droppings – as an inexpensive source of biogas.   Together with other partners, I am now determined and hoping to push for the use of this cheap but effective technology as a way of reducing poverty in rural Uganda and within slum areas.   After solving my energy needs at the centre (might be tricky as I have no space left for anything) at the campsite and at the village home, I will turn to family homes, schools and hospitals, sharing all the knowledge gained along the way.

In an effort to stave off the growing threat of deforestation in Uganda, we will work with several partners to build biogas plants.

The Project:

The Biogas project is meant to be an alternative source of energy to replace crude methods like wood cutting which degrade the environment.  If well developed, the country would be relieved of rural energy shortage problems.

The biogas project will target people in communities such as refugee camps, military camps, schools, hospitals and prisons.   Areas that have already been identified to benefit in the pilot project include all cattle keeping zones and other congested human settlements due to the ready supply of the biogas raw material (cow dung etc) already in these areas.

The Vision/Plan:

  • The plan is to see to it that at least one bio digester is constructed in all the sub counties of Uganda and if funds do allow, in all the villages of Uganda.   The plan is also to, at least, train two or more people in these areas.   The trained people would then provide the necessary support, information and advise to whoever wanted to build one at his/her home.
  • To occasionally carry out an Open Day event to provide information to the public about biogas technology and its benefits to the user and the nation.
  • Also to try and partner with other interested parties (other researchers, NGOS and government) to further this research.

Biogas:

This inflammable gas is typically produced by bacteria in an air tight container called a digester.   Biogas made from excreta contains 60 – 90% methane – enough for it to burn without further purification. There are currently three available plant models:  floating, polythene tubular system and Chinese fixed dome – the latter is what we hope to promote for the following reasons:

It keeps the environment free of organic wastes, is convenient, time-saving and reduces smoke-related illnesses often associated with the use of firewood. If the majority of Ugandans adopted biogas, we would preserve our biodiversity.   People should exploit decomposing raw materials, which are free.   Biogas plant maintenance is not regular, constant energy, no load shedding,  local technicians are available, appliances are now locally-made and there is no metering.   Therefore,  no monthly power tariffs.

In Uganda’s Mukono district – where the technology is being used for cooking, lighting pressure lamps and in various engines – the residents are already reaping the benefits:  Many are pulling themselves out of poverty and are using its by-product, a “slurry,” to enrich their soil, contributing to larger crop outputs.

Benefits

By using biogas, many advantages arise.   In Uganda, utilization of biogas would generate enough electricity to meet up to three percent of the country’s electricity expenditure.   In addition, biogas could potentially help reduce global climate change.   Normally, manure that is left to decompose releases two main gases that cause global climate change: nitrous dioxide and methane.   Nitrous dioxide warms the atmosphere 310 times more than carbon dioxide and methane 21 times more than carbon dioxide.   By converting cow manure into methane biogas via anaerobic digestion, the hundreds of cows in Uganda would be able to produce many kilowatt hours of electricity, enough to power hundreds of homes across Uganda.

Amazing facts:

  • One cow can produce enough manure in one day to generate three kilowatt hours of electricity;
  • Only 2.4 kilowatt hours of electricity are needed to power a single one hundred 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 ninety-nine million metric tons or four percent.

The 30 million rural households in China that have biogas digesters enjoy 12 benefits:  saving fossil fuels, saving time collecting firewood,  protecting forests, using crop residues for animal fodder instead of fuel,  saving money, saving cooking time,  improving hygienic conditions, producing high-quality fertilizer,  enabling local mechanization and electricity production, improving the rural standard of living, and reducing air and water pollution.

  • In comparison with other power sources, 5100 Kcal of biogas is equivalent to 3.6 Kg of firewood usage, whereas 5100 Kcal of biogas can replace 1.5 Kg of charcoal consumption.
  • 13kg of dry cow dung consumption is equivalent to 5100 kcal biogas usage per family whereas 1Kcal biogas consumption is equivalent to 1.25 electric power consumption.   Research indicates that in a day, one cow can produce 9-10 Kilograms of cow dung worth 59% of biogas supply for a relatively small family, whereas 8 kg of hen droppings can produce 2.2 volumes of biogas.
  • It was found out that human bi-products are the effective ingredients for biogas production. 0.5 kg of human bi-products produces 68% methane gas content which is used for biogas production.

Biogas Digesters:

biodigester-2

The digester is an airtight pit made of concrete with a pipe connection. The manure is directed to the pit, usually directly from the cattle shed. The pit is then filled with a required quantity of wastewater.   The gas pipe is connected to the kitchen fireplace through control valves.   The combustion of this biogas has very little odour or smoke.   Owing to simplicity in implementation and use of cheap raw materials in villages, it is one of the most environmentally sound energy sources for rural needs.   One type of these systems is the Sintex Digester.   Some designs use vermiculture to further enhance the slurry produced by the biogas plant for use as compost.

Bio digesters can be built in different sizes depending on the energy needs of the family (9+cubic metres) we now have drawn up plans for these and the necessary expertise to build any size of digester!   If one is to use machinery on the system, a 10+ cubic metre bio digester is recommended for construction.

Biogas upgrading

Raw biogas produced from digestion is roughly 60% methane and 29% CO2 with trace elements of H2S, and is not high quality enough if the owner was planning on selling this gas or using it as fuel gas for machinery.   The corrosive nature of H2S alone is enough to destroy the internals of an expensive plant.   The solution is the use of a biogas upgrading or purification process whereby contaminants in the raw biogas stream are absorbed or scrubbed, leaving 98% methane per unit volume of gas.   There are four main methods of biogas upgrading; these include water washing, pressure swing absorption, selexol absorption and chemical treatment.   The most prevalent method is water washing where high pressure gas flows into a column where the carbon dioxide and other trace elements are scrubbed by cascading water running counter-flow to the gas.   This arrangement could deliver 98% methane with manufacturers guaranteeing maximum 2% methane loss in the system.   It takes roughly between 3-6% of the total energy output in gas to run a biogas upgrading system.

We are soon starting to experiment on the upgrading of the produced biogas, compress it into cylinders for sale on the Uganda markets.   If it successfully works,  it would be a breakthrough!  There is also a possibility of constructing much bigger digesters in populated areas and find a way of feeding it and supplying metered biogas.   In return,  families could make a small financial contribution each month.   Looking at the work that has already been done, there are higher chances that this would work.

biogas-3

Only one company is selling biogas appliances in Uganda (gas lamps and stoves) once more people start using the biogas, the demand would be much higher and enough to allow another supply chain to be opened up.   This is an area that could lead to further business developments.

Biogas generators are now available on the market in Rwanda at reasonable prices. Making them available to people in Uganda would open up opportunities for those who want to move a step further with this technology

Cost for building Bio digesters:

Depending on size and location, a typical brick made fixed dome biogas plant can be installed at the yard of a rural household with the investment of between £600-800.   A high quality biogas plant needs minimum maintenance costs and can produce gas for at least 15-20 years without major problems and re-investment.

Follow up:

If anyone would like to know more or feels they would like to be involved and help in achieving our vision then please email us.

njendahayo@yahoo.com

revtimhall@stdavidscollege.co.uk

Clock here for up-to-date information on current projects and working biodigesters in Uganda