Rehema’s tips on how biogas works

On March 29th, Rehama was privileged to join a team of researchers and environmentalists who visited Tiribogo village in Muduuma Sub country, Mpigi district. This was part of a field survey about the status of biogas digesters.  The research team came from the University of Aberdeen in partnership with Makerere University,  James Hutton Institute (JHI), Scottish Agricultural College (SAC), Phytobiotechnology Research Foundation (PRF), Centre for Research in Energy and Energy Conservation (CREEC), Green Heat Uganda (GHU) and Orskov Foundation. The project entitled “The Potential of Small-Scale Biogas Digesters to Improve Livelihoods and Long Term Sustainability of Ecosystem Services in Sub-Saharan Africa” was funded by DFID.

Good reception about biogas

All the nine users of the flexible balloon digesters appreciate the technology because of various advantages it has over using firewood. However, more efforts need to be geared at educating and sensitizing the masses about biogas technology and how to adapt to maintenance demands. Kaloli Kimuli, a resident of Tiribogo village and a lead user of the flexible balloon digester believes that much as they are benefiting from the systems now, they have faced a lot of challenges because they didn’t know how the system works.Through all the testimonies I listened to, I summarised just five basic facts people didn’t know about biogas.

What is biogas digester? Biogas is gas created from organic matter such as animal manure, dead crops or food and human waste under anaerobic conditions. Let me explain the meaning of a biogas digester using an example of the human stomach. When you eat food, it goes to the stomach, where digestion takes place. Energy is created and waste is released in form of faeces and gas. The same theory applies to a biogas digester. A digester is a closed up structure where organic waste is put and later turns into gas under no oxygen supply. The digester is fed with animal manure, human waste or dead plants. With no supply of oxygen, this waste will decompose and a gas will be produced from the process and the remains will form fertilizer flows out of the system. Gas is formed and trapped through a tube and later piped to the chicken for cooking or tapped and turned into lighting energy. To read more about how biogas works and some of the types of biogas digesters,

Women and children spend over 4 hours each collecting firewood
Women and children spend over 4 hours each collecting firewood
20 kg of firewood used per day
20 kg of firewood used per day
Over 80 percent of household in Sub Sahara Africa use this type of "stove" to prepare meals.
Over 80 percent of household in Sub Sahara Africa use this type of “stove” to prepare meals.

NOTE: Just like how the human stomach is fed daily to support the functioning of the body system, the digester has to be fed with waste on a regular basis to generate gas or else, the gas will get used up. You cannot survive without eating regularly. Can you?

Organic waste like manure, food leftovers, poop are good for biogas production
Organic waste like manure, food leftovers, poop are good for biogas production
Floating drum digester used to produce biogas
Floating drum digester used to produce biogas

What are some of the factors to consider before investing in biogas technology for home or institutional use? Just like any other energy generating technologies, one needs to have some requirements in place before installing a biogas system. Here are the important requirements one needs;

Constant waste material supply: This can be human waste, animal waste (cows and pigs have the biggest amounts of waste and most recommendable. However, if you have goats, sheep and any other animals that you can constantly access, it is okay to use it). This waste has to be readily available. I mean, it will be easier for someone to adopt easily to feeding a digester if the waste doesn’t require them incurring transport.

Water: This is used to mix this waste material before its fed to the digester. In order for complete decomposition to take place, there has to be water.So, water is required to mix the waste material.

Interest and commitment to the digester or “the stomach”: This comes so easily if one has the interest in the technology and how it works. Doesn’t that gas smell because it’s former out of rotting waste material? No, biogas doesn’t not smell at all. It burns cleanly.

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