Fact
There are 9 AD plants in the UK today licensed to take food waste including animal by products.
Three of these belong to BiogenGreenfinch.
Anaerobic Digestion in more detail
Our process is a unique application of an established technology. It uses anaerobic digestion (AD) to recycle food waste and other organic materials.
It generates renewable energy and returns a valuable biofertiliser to the land.
Our British technology can deal with food waste in almost any form:
- Solid, liquid, sludge.
- Packaged or unpackaged.
- Out-of-date and damaged foods from retailers and supermarkets.
- Food waste from restaurants, pubs and hotels, offices, hospitals and schools.
- Domestic kitchen food waste.
- Food processing waste.
- Animal by-products.
How it works
Anaerobic digestion is a complex biological process – our plants use the mesophilic process at temperatures of 35 to 40°C (the alternative thermophilic process requires much higher temperatures.) AD takes place in the absence of air in a large, sealed and insulated vessel with controlled heating and mixing.
Food waste enters a sealed building where it is processed into a porridge, and then pumped into temperature controlled sealed vessels known as digesters. It is here that bacteria feed on the food waste and produce biogas. Biogas is typically made up of 60% methane and 40% carbon dioxide and is captured and used as a fuel in a CHP (combined heat and power) unit.
Anaerobic digestion is a series of bacterial processes that can be broadly categorised into 4 distinct stages:
- Hydrolysis: Large molecules of carbohydrates, fats and protein are broken down to their small water-soluble subunits. These are simple sugars, lipids and amino acids, and are now in the correct form to be available to the bacteria.
- Acidogenesis: The products of hydrolysis are converted into Volatile Fatty Acids by bacteria. VFA’s are short chained organic acid molecules, the most important of which is Acetic Acid.
- Acetogenesis: The Volatile Fatty Acids are converted to Acetic acid by bacteria.
- Methanogenesis: This is where the methane is made. Acetic acid is used by methane forming bacteria. The majority of the methane in biogas is made in this manner.
During the process no methane is released into the atmosphere.
The digestate or biofertiliser produced undergoes pasteurisation to ensure that any pathogens are killed and is stored in large covered tanks ready to be applied twice a year on farmland. The use of this high nutrient biofertiliser replaces the use of fossil fuel derived fertiliser and ensures nothing is wasted.
Each tonne of food waste recycled by anaerobic digestion as an alternative to landfill prevents between 0.5 and 1.0 tonne of CO2 entering the atmosphere.
