Increasing energy demands in urban and rural households in Uganda have escalated challenges related to land degradation, indoor air quality, and rural economic development. When thinking about renewable energy it is common to think of wind power and solar. However, there is massive potential in our country for the utilisation of renewable gas for power generation.
Some naturally occurring microbes are able to break down organic material in the absence of oxygen to produce different types of biologically-created gas – ‘biogas’ that consists primarily of methane and carbondioxide.
Renewable energy from biogas has the added benefit of being able to produce a consistent source of power, ‘base-load’, rather than just when the sun shines or wind blows. It can also be utilised for high efficiency combined heat and power generation – giving a useful source of renewable heating or cooling.
In order to understand biogas better, one needs to know that it can be produced from raw materials such as agricultural waste, manure, municipal waste, plant material, sewage, green waste or food waste.
Apart from cooking, biogas can also be used in a gas engine to convert the energy in the gas into electricity and heat.
Biogas plants are basically two types i.e. mainly the digester or pit for fermentation and a floating drum for the collection of gas.
Biogas is becoming increasingly more popular as a form of energy to power rural communities in Africa, who live far away from the electricity grid. As a low-cost integrated system providing alternative energy, as well as organic manure, it also provides an answer to reducing gas emissions and improving soil fertility.
More than 70 per cent of the population in Africa relies on fuel-wood energy sources, whereby 90 per cent of the resource is extracted from natural forests. Excessive energy consumption derived from forest resources disrupts carbon sinks, which compounds the adverse effects of climatic change such as recurring droughts, flooding, land degradation, and loss of soil nutrients, which directly affect livestock and crop yield.
Consequently, energy sources in Africa that are perceived as environmental friendly have received growing attention, especially when these sources also have the potential to alleviate energy poverty, which is generally defined as limited or lack of access to modern energy infrastructure.
One sustainable energy alternative that has potential to provide low-cost energy without the need to harvest wood is a biogas digester. Capturing biogas during waste decomposition and using it for energy) can reduce the use of fuel-wood energy, and hence lessens the degradation of local forests. This commensurately reduces the greenhouse gas emissions into the air and improves carbon sequestration potential.
Biogas digesters can also improve rural livelihoods through energy cost savings and reduced labour to harvest wood and by providing organic fertilisers that can enrich soil fertility.
Biogas burns very cleanly, and produces fewer pollutants during cooking than any other fuel except electricity. Biogas provides instant heat upon ignition, no pre-heating or waiting time is required. Biogas can be used for lighting as well. The by-product (slurry) from the digester can be used as fertiliser.
The Ugandan government can start a project for sensitising and introducing of bio-digesters across rural villages with the hope that introducing bio-digesters to rural households would address all of these issues.
Once the use of biogas is enhanced then we shall finally realise a reduction in the cutting and burning of wood, still prevalent in rural areas, as well as help rehabilitate degraded land.
Mr Frank K. Kweronda is a Civil Engineer Africa.