By Dr Moses Amweelo
Biogas has been used for over 3000 years as an effective fuel for cooking and lighting. It makes a meaningful contribution to the energy supply and it saves fossil energy, such as coal, oil and gas. It also makes a significant ecological contribution to heat and electricity production.
It is an environmentally-friendly source of energy because it produces electricity and heat but still keeps carbon dioxide emissions neutral.
As fossil-based fuels become scarcer and more expensive and carbon dioxide emission levels become of greater concern, the benefits and potential of biogas as a source of energy supply are being increasingly recognised.
Biogas is a mixture of methane and carbon dioxide. It is produced by the action of bacteria on vegetable/organic material in airless conditions which is why the process is also known as “anaerobic digestion”.
The bacteria slowly digest the material (usually animal dung, human wastes and crop residues) and produce a gas which is roughly 60% methane and 40% carbon dioxide. One of the main attractions of biogas technology is its ability to generate biogas out of organic wastes that are abundant and freely available.
The potential gas production from some animal dung is highlighted by the fact that the manure from one dairy cow can produce 9kg of LPG equivalent (a small gas cylinder) in 20 days.
APLICATIONS FOR BIOGAS
Biogas technology can be implemented as a decentralized sanitation solution which provides energy security and nutrient-rich pathogen-free waste water which can be used for food production. Biogas systems can be scaled from small family-sized to large 100,000 or more person systems. Biogas digestion is a renewable energy technology that ensures a distributed energy production where the energy is produced at the point of consumption or demand. There are over 30 million operational biogas digesters in the world as at 2007. China alone has over 25 million residential biogas systems installed – with over a million now being installed each year – as well as over 100,000 sewage treatment plants capturing biogas for conversion to useful energy.
In North America, utilization of biogas would generate enough electricity to meet up to three percent of the continent’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.
Most households in the SADC region obtain their energy for cooking and heating from biomass. Potential biomass energy supplies include municipal solid waste, industrial residues and energy plantations. Through the Programme for Biomass Energy Conservation, SADC, in partnership with German Technical Cooperation, are promoting efficient energy-saving wood stoves in the region. This programme promotes a switch to renewable energy sources through the introduction of biogas, solar cookers, and fuels can include crop residues.
ADVANTAGES OF BIOGAS TECHNOLOGY
• Biogas can make an important contribution to the protection and improvement of natural resources and environment.
• Slurry, a residue from the process, is a high-grade fertilizer that can replace expensive mineral fertilizers, in particular nitrogen.
• The technology is ideal for effective and productive management of livestock wastes.
• The technology provides an efficient wet sanitary system - that enhances effective waste product disposal.
• It provides an integrated system for waste treatment, energy and fertiliser production.
• The use of biogas enables rural women to save time for productive agriculture, leisure and family care and welfare.
• Use of biogas technology improves the standard of living and can directly contribute to economic and social development of a country.
• A biogas digester can be locally produced or built, and locally operated. The cost of the technology is therefore largely independent of exchange rate fluctuations.
• It is a low maintenance sanitation system which generates resources which requires no electrical and synthetic chemical inputs.
• The technology has the potential to permanently employ many thousands of people should its potential be reached in the country.
Domestic biogas plants convert livestock manure and night soil into biogas and slurry, the fermented manure. This technology is feasible for small holders with livestock producing 50 kg manure per day, an equivalent of about 6 pigs or 3 cows.
This manure has to be collectable to mix it with water and feed it into the plant. Toilets can be connected. Another precondition is the temperature that affects the fermentation process. With an optimum at 36 C° the technology especially applies for those living in a (sub) tropical climate. This makes the technology for small holders in developing countries often suitable.
Recently, our visit to Nepal included an initial set of briefings with parliamentarians and government and NGO staff, followed by five days of site visitations to various field activities. The delegation was exposed to a range of new ideas and concepts. Some that appear suitable for introduction into Namibia’s 71 communal conservancies include:
• Household Biogas Plants – Nepal has pioneered an innovative approach of generating biogas that can be used for cooking in individual households, while at the same time, improving household hygiene and reducing deforestation.
A high quality biogas plant needs minimum maintenance costs and can produce gas for at least 15–20 years without major problems and re-investments. For the user, biogas provides clean cooking energy, reduces indoor air pollution, and reduces the time needed for traditional biomass collection, especially for women and children. The slurry is a clean organic fertilizer that potentially increases agricultural productivity.
Domestic biogas technology is a proven and established technology in many parts of the world, especially Asia. Therefore, I advocate that the usage of domestic biogas could be the best solution in Namibia, especially in our rural areas.