Biogas

Biogas is derived from the anaerobic(in the absence of oxygen) fermentation of biomass and solid wastes, which are combusted to produce heat and electrical power, it mainly contains carbon dioxide and methane. Landfill gases and gases from sewage and animal waste facilities are included in this category.

i) It produces more energy with less emissions of carbon dioxide than coal.

ii) It can be used to produce cheaper electricity therefore reducing costs spent on energy.

iii) It can easily be produced from paper production, sugar production, animal waste.

iv) It has the potential to reduce energy use and decrease emissions in a very inexpensive manner.

v) Biogas systems will contribute immensely to rural development by turning people away from the traditional means of cooking and lighting by providing them with more efficient energy sources.

vi) The organic materials needed for producing biogas in an anaerobic digester are readily available in developing countries. i.e. cattle and other farm animals.

vii) The dried manure left after the gas is generated is richer than ordinary manure and makes a fantastic organic fertilizer.



Digester Systems

Digester systems have the added benefit of producing a high nutrient fertilizer and encouraging better sanitation on farms. They can reduce bacteria in manure by more than 99 percent, virtually eliminating a major source of water pollution. Separation of the solids during the digester process removes about 25 percent of the nutrients from manure.

The waste (called slurry) is stored in specially constructed containers while being digested. There are a number of technologies used to accomplish this:

A) Batch type digesters treat a large amount of material at once. They are used for large scale applications.

B) Continuous flow units add and remove waste material on a daily or regular basis. They are best suited for small-scale domestic applications.

Alternative energy in Kenya

Biogas technology was introduced in Kenya in the mid 1950s by white settler farmers. By 1958, a private company Tunnel Technology limited was constructing processing plants in different parts of the country. The company had installed about 150 units by the early 1980s. It is most commonly used for cooking and lighting.

The technology is a cost-effective investment if plants are properly constructed, effectively operated and well maintained. Only an estimated 25 % of the installed plants in Kenya are operational, giving the technology a negative image. With the rising cost of services such as electricity and cooking gas, biogas is beginning to look like a prospective alternative for creating energy. It has also led to a reduction of cutting down trees and has spared many people the burden of gathering firewood every now and then in rural areas in Kenya.

In Kenya, biogas is produced mainly on individual homesteads in rural areas. The production process is simple and straightforward as long as the feed material is in easily digestible small particle size with organic content. In most cases, feed material is almost entirely cow dung with limited quantities of grass that always end up getting mixed in with the dung. Biodegradability is the key factor in its production. Some organic wastes that are found in paper, grass and stalks are difficult to digest. Such materials need special treatment to reduce particle size and also degrade the complex compounds to simpler more easily digestible molecules.

Major constraints to biogas technology dissemination include:

• High initial investment costs compounded with lacking credit schemes.

• Negative image caused by the previously failed plants.

• Limited private sector involvement.

• Biogas generation is not as easy as the simplicity of its equipment might suggest. The temperature and chemical sensitivity of the methanogenetic bacteria require careful management. Digesters must be fed daily with material of the proper liquidity, pH and carbon/nitrogen ratio. A change in feedstock or some other biological shock may halt gas production for weeks.

To increase viability the following avenues must be explored:

1. Resources should be directed to promoting the technology in high potential areas.

2. Private sector involvement in promotion and dissemination is necessary for successful adoption of the technology.

3. There is need to counter the already negative image of the technology that exists by promoting proven designs and providing post installation support.

4. Cheaper low costs designs need to be developed to lower the cost entry barrier.

5. Access to credit for end-users and small enterprises promoting biogas.

6. Promoting entities should develop sufficient capacity to advice potential users on available options.

The United Nations Framework Convention on Climate Change has set up a Clean Development Fund, and the World Bank has put together a Carbon Finance Unit to allow rich countries, which are pumping more carbon into the atmosphere than is allowed under the Kyoto Protocol, to buy emissions that poor countries prevent through conserving forests or promoting renewable energy. This is a major advantage for countries that decide to adopt biogas as an alternative energy source because their governments get paid for reducing output of greenhouse gases and also for conserving the environment from degradation.

It would make much better sense for rich countries to cash in on these same benefits themselves rather than paying cash to poor countries not to burn firewood. Furthermore, they also have greater capacity for research and development to optimize the production and use of alternative sources of energy.