Biomass energy is the use of biomass as an energy source. With biomass energy, biomass is burned or converted to make heat, electricity, or liquid fuel. Biogas is a renewable energy; it is created as a direct result of transforming food waste to energy and is an environmentally friendly way of doing it.
Biomass produces energy from the burning of plant and animal matter to create energy. Biogas uses the same fuel – plant and animal matter (and in some cases human waste too), usually considered as waste – to create gas which can be used for cooking, heating and even refrigeration, and the resulting left over liquid slurry and digestate is a nutient rich organic fertiliser ideal for growing food crops. It’s a perfect and sustainable circular system for producing energy at a very low cost and without the need for complex equipment.
Basically a biogas plant consists of a sealed tank – the digester- which is filled with the organic matter and waste water, sometimes referred to as grey water. Grey water can come from water used for bathing, washing or from the toilet. It’s important that the tank or digester is sealed as the breakdown of the organic matter must take place in an anaerobic or oxygen free environment. A fermentation process takes place in the digester producing mostly methane as well as hydrogen and carbon monoxide. The gas is usually compressed, much like naturally occuring gas, and used for a number of different applications including heating, cooling, cooking and even for generating electricity or for use in internal combustion engines like motorised vehicles. For example, in Sweden, hundreds of cars and buses run on refined biogas. The biogas in Sweden is produced primarily from sewage treatment plants and landfills.
The production of biogas is a naturally occuring phenomonen which occurs in the ocean, in wetlands, swamps, rice paddies, landfill sites and even in compost heaps – anywhere were the decomposition takes place in the absence of oxygen.
The production and use of biogas is particularly predominant in China and India and increasingly in the US where it’s used to cope with animal waste from large scale farms.
Anecdotal evidence traces the first uses of biogas to the Assyrians and the Persians in the 10th and 16th centuries.
Landfill sites produce biogas which can be harnessed for energy production. Coping with the organic waste produced in industrialised countries is becoming increasingly urgent and demanding,thus the production of biogas can help solve the problem. It has increasingly gained popularity in Africa where it is alternatively used in place of firewood for cooking and heating.
Zimbabwe’s Environment Management Agency (EMA) says that 50 million trees are disappearing from forests in the country every year and biogas can therefore help to curb this ongoing dilemma.
Biogas projects can be built on a huge industrial scale or on a much smaller scale for rural communities and even for individual households with the use of a drum. In the UK, for example, it is estimated to have the potential to replace around 17% of vehicle fuel. By converting cow manure into methane biogas via anaerobic digestion, the millions of cattle in the United States would be able to produce 100 billion kilowatt hours of electricity, enough to power millions of homes across the United States. In fact, by converting cattle manure into methane biogas instead of letting it decompose, global warming gases could be reduced by 99 million metric tons.
Recent projects in Zimbabwe to establish biogas production include the creation of biogas digestors for projects in Domboshawa, as well as Insiza, Chegutu, Goromonzi and Mvuma. Projects are funded by NGOs including HIVOS, SNV and Ministry of Energy and Power Development, Ministry of Agriculture, Mechanisation and Irrigation Development and the Renewable Energy Fund.