Benefits of Biogas
Like many subtropical regions, Sub-Saharan Africa depends primarily on wood for energy. Rural households cook their meals on firewood, charcoal, or agricultural biomass. Urban dwellers predominantly utilize charcoal for cooking, yet kerosene and LPG are also common. Due to inefficient use of wood fuels and increasing population levels, endemic reliance on energy from biomass is resulting in deforestation and desertification throughout Sub-Saharan Africa. Moreover, the burning of wood fuel contributes to greenhouse gas emissions and indoor air pollution. Health risks associated with indoor air pollution have been cited as one of the ten major threats to health (globally) and an acute danger to women and girls. Domestic health risks are compounded by a lack of access to adequate sanitation.
Biogas is particularly well suited to meet household energy needs in Sub-Saharan Africa, while simultaneously improving both soil conditions and household sanitation. With a biogas system, smallholder farms are able to use manure from their livestock to generate energy and organic fertiliser. A biogas system may also be fitted with a pit latrine for sanitation. Urban biogas users can dispose of organic household waste and improve sanitation while reducing energy expenses.
How does biogas work?
Biogas systems make use of a relatively simple, well-known, and mature technology. A biogas system comprises a large tank, or digester. Inside this tank, bacteria work symbiotically to convert organic waste into methane gas through the process of anaerobic digestion. Each day, the operator of a biogas system nourishes the bacteria inside the digester with household by-products such as market waste, kitchen waste, and manure from livestock. The methane gas produced by the bacteria inside biogas system may be used for cooking, lighting, and other energy needs. Waste that has been fully digested exits the biogas system in the form of organic fertiliser.
Biogas has several external benefits: biogas replaces the unsustainable use of biomass, slows deforestation and reduces greenhouse gas emissions; emissions of methane (a strong greenhouse gas) associated with the decomposition of livestock manure are mitigated; the import of both kerosene and foodstuffs are reduced, thereby improving the trade balance; and healthcare costs are decreased through improved indoor air conditions and better environmental sanitation.
A family that operates a six cubic meter biogas system can meet their daily cooking needs, burn a gas-lamp at night, and save money or time (3+ hours a day!) otherwise spent on purchasing or collecting wood fuel. They will also increase agricultural productivity, and improve household sanitation conditions.
Cooking
Cooking on biogas is easy and efficient. A biogas stove is analogous to the gas stoves found in many western homes. Biogas stoves are safe for indoor use and a switch to biogas will eliminate the dangers of indoor air pollution – a threat to the lives and livelihoods of women and children in many (sub)tropical regions. The alleviation of health risks associated with indoor air pollution may directly result in a reduction in healthcare costs and as well as an increase in productive days. Moreover, cooking on biogas is fast. Biogas eliminates the process of preheating, which is a necessary step when cooking on biomass.
Lighting
Biogas may be used for lighting. Biogas lamps allow households that are off of the energy grid to light their homes after dark, enabling children to study and family members to engage in new forms of business, such as craft-making. Biogas lamps are brighter than their kerosene counterparts and safer for domestic use. Unlike a kerosene lamp, a biogas lamp cannot be knocked over, thereby mitigating fire danger in the home.
Fertiliser
Biogas-slurry is a safe, organic, and nutrient-rich liquid fertiliser, which can be applied directly to crops to increase agricultural productivity. The use of biogas-slurry not only saves money otherwise spent on chemical fertilisers, but reduces the negative effects of such fertilisers on the environment. It is estimated that the application of biogas-slurry may increase productivity as much as 25% when compared to applying manure directly to fields.