Agricultural waste from the dairy farm such as cattle slurry and manure is a vital ingredient for the health of the digestion process. A constant stream of new Methanogenic bacteria from the cattle manure helps to keep the bacteria populations in good condition.
The food processing industry generates large volumes of waste material, such as peelings and cuttings from vegetables, which can be added to the digestion process. By sending waste to the digester instead of to landfill, food processors can reduce their impact on the environment and reduce the cost of waste disposal.
The anaerobic digester consists of two large circular covered tanks that are filled to 800mm from the roof with the agricultural and food waste. The waste is heated to around 40°C to enable the bacteria to breed and the system is fed with fresh material 24 hours per day to give the bacteria a constant supply of fresh food. Methanogenic bacteria in the system produce methane gas which is collected in a large dome above the digester.
The gas produced by the bacteria is then used to fuel two generators which produce electrical and heat energy for use on the adjacent dairy farm. Power to Grid Any excess electrical energy produced by the generators is exported onto the national grid for consumption by local homes and businesses.
After the bacteria have digested all the available energy from the blend of waste you are left with an energy rich liquid known as digestate that can be spread on the farm land.
The nutrients and minerals contained in the digestate provide a valuable source of fertiliser for growing crops to feed the dairy herd.