Biogas digesters, also known as Biogas Plants or Anaerobic Digestion Plants, are generally thought to be a new technology by those in wealthy countries; nevertheless, they have been widely utilised in developing countries, particularly India and China, for many years when firewood for cooking becomes scarce. Other countries, ranging from Honduran farmers to the tiny South Pacific island nation of Tuvalu, have successfully harnessed the natural gas produced by decaying manure and other organic materials. These Biogas Plants, which use the anaerobic digestion process to produce the fuel gas, also have the potential to produce a high-nutrient slurry fertiliser and improve farm hygiene.
The win-win process goes even further because the digester’s pollution emissions are significantly lower than they would be without it, so they can assist to reduce river and groundwater pollution at the same time. Microbiology is used in a working biogas digester system, as well as the development of renewable energy.
Farm or community/human waste (called slurry) is held in specially constructed containers while being digested using biogas technology. Depending on the reactor design, manure can be handled as a liquid, slurry, or semisolid in biogas plants. Biogas digesters take biodegradable feedstock and turn it into gas and digestate, two important outputs (solid and liquid).
Both are beneficial, and this is undoubtedly one of the primary reasons why more and more farmers around the world are installing biogas digesters.
Biogas plants are typically constructed underground to protect them from temperature fluctuations as well as accidental damage. They not only conduct the necessary tasks to keep the bacteria happy and produce biogas, but they have also developed designs ideal for farms and communities in underdeveloped countries that can be replicated using components that are cheap, easy to get, and simple to assemble.
The typical biogas digester in a developing country is built in a hole dug by a trained labourer with the help of one or more members of the household or community. A typical biogas digester has an 8-m3 volume, while some are larger at 10-15m3, and can supply enough gas for a two-ring stove and a light.
Human and animal waste can both be digested by a biogas digester. We are aware of one Anaerobic Digestion Plant that is based on pig husbandry and is constructed beneath the pigsty. The pigsty is insulated, and the plant generates some heat as well, which helps to keep both the pigs and the biogas digester warm throughout the hard winter months.
A biogas factory is made up of one or more airtight reservoirs into which a suitable feedstock, such as cow dung, human waste, or even slaughterhouse waste, is fed in batches or on a continuous basis. It is blended on a regular basis, and the solid and liquid digestate is eliminated. Methane bubbles to the top and is stored as a large bubble above the liquid in the simplest systems. Methane is stored in separate tanks in more advanced systems, ready to be used when needed.
The rising use of anaerobic digestion in Africa has huge potential for benefit. According to an AGAMA Energy information sheet, there are 400,000 households in South Africa with two or more cows and no electricity that could benefit from biogas digesters. According to an article published in the Rwandan daily The New Times on November 30, 2005, the Institute for Scientific Research and Technology in Kigali wants to install 1,500 biogas digesters in the imidugudu villages by 2009. Following the horrific battles of the mid-1990s, rural Rwandans were transferred to these settlements.
According to the Worldwatch Institute’s Renewables 2005: Global Status Report, around 16 million households worldwide employ small-scale biogas systems.
According to reports, a residential biogas digester unit capable of providing enough energy for an entire family’s cooking needs can be installed in India for between R5 000 and R8 000, or less than $200 USD. Facilities that are best suitable for biogas plants have consistent year-round manure production and collect and feed manure to the digester on a daily basis.
