Biogas plants are growing in popularity throughout rural areas for their use as a free source of renewable energy. Not only does this system provide energy, it also recycles waste, improves public hygiene and controls pollution. The biogas produced by this product can be used instead of gasoline and other fuels to generate electricity.
Biogas is an odorless, colorless gas commonly referred to as sewer gas. It is primarily made of methane, and 1,000 cubic feet of biogas can produce the same energy as 600 cubic feet of natural gas or 5.2 gallons of gasoline. A family of four may use 150 cubic feet of gas daily to power the appliances and lighting in their home.
Biogas plants feature a digester (fermentation tank) and a container that holds gas. There are also containers that hold the feed slurry and sludge. Brick, cement, concrete and steel are used to build the digester reactors. In some cases, digester bags are used because they are more economical than concrete and steel digesters. This bag measures 0.55 mm thick and is produced in the United States.
How it Works
The digester, shaped like a cube or a cylinder, has an inlet for slurry to enter it. The gas holder is made from steel and floats in the digester. Its placement cuts off air to the digester, and the gas tank absorbs the emitted gas, sending it out of the plant through a pipe. Overflow from the digester is fed to the sludge receptacle.
There are a number of raw materials which can be used to create biogas. Many of these products can be found around the home or farm. Waste from livestock, such as cows and poultry, can be used. Paper waste, food waste, aquatic weeds, seaweed and residue from hay, straw and corn can also be utilized. These materials should be stored in a closed space for 10 days to initiate anaerobic bacteria.
Without the proper nutrients, microbiological activity will not reach optimum potential and useful gas may not be produced. Carbon and nitrogen are the primary nutrients that need to be present to produce useful biogas. Sources of these nutrients include sewage and animal waste. Materials such as grass and corn stubble are extremely low in nitrogen and will not produce useful gas by themselves.
Based in Ponte Vedra, Fla., Carly Reynolds has been an article and Web content writer since 2006. Reynolds holds a Bachelor of Arts in English from Florida State University.