By Hilary Griffiths
A group of 12 of us were lucky enough to be able to visit Agrivert AD (anaerobic digestion) facility in Longcross, Chertsey on August 18th.
At the facility, food waste from our household bins is turned into fertiliser and a biogas, which produces electricity.
The visit was organised for us by Sarah Mabey of Woking Borough Council (WBC) at the request of Woking Green Drinks and LA21.
Why recycle food waste?
Agrivert is a private company that WBC and many other food waste collectors use to dispose, in an environmentally friendly way, of food waste that would otherwise go to landfill, every day.
It is a win for economic reasons, too, as it is considerably cheaper to recycle our food waste in this way than to leave it in the black bins and send it off to landfill, where it releases methane, which is 23 times worse as a greenhouse gas than carbon dioxide!
What happens to the food waste?
Vehicles arriving at the site tip the food waste into a recessed bunker. The waste is then macerated, and all packaging removed. Liquid waste is added, creating a liquid food ‘soup’, which then passes into the huge digesting tanks (the “stomachs” of the plant) where natural enzymes break down the food over a period of about 90 days as it passes from the first tank to the fifth, pasteurising the soup along the way.
Biogas is drawn off continually, (CH4 mainly with some CO2) and finally a rich digestate remains, used as nutrient-rich fertiliser on 2500 acres of farmland nearby.
The biogas then passes into the final stage where it is burnt to produce energy to turn turbines to produce electricity, which is sold straight into the National Grid.
The plant was only built in 2014 and uses safe, modern technology to keep efficiency high.
Using your food waste bin
Food waste is collected once a week. You should have a small silver ‘caddy’ bin, designed to be kept indoors and either your own larger green collection bin, or a shared food waste bin for a block of flats.
Previously, only compostable bin liners or newspaper could be used in these bins. Recently, WBC has announced a change, which means that households can now use plastic bags (including carrier bags, or bags food has come in, such as bread or salad). The bags are removed at the Agrivert facility.
You can find out more about this change on the WBC website, along with details of what can and can’t be put in the food waste bins.
Thank you to Agrivert for allowing us to visit and providing us with an excellent guide!
Please pass this on to any non-food waste recyclers to encourage even more usage of the Woking food waste recycling scheme, saving council tax and smelly bins!!