Gloucestershire Recycles - October 2020 newsletter

What happens to your food waste?

After leaving your kitchen caddy, food waste embarks on a remarkable transformation process that enables it to generate clean, green and eco-friendly energy for local homes!

Something rather special happens to your food waste once it arrives at our recycling plant just outside Bishops Cleeve near Cheltenham. After leaving your kitchen caddy, it embarks on a remarkable transformation process that enables it to generate clean, green and eco-friendly energy for local homes AND helps farmers grow bigger and healthier crops.

It’s been estimated that just one caddy of food waste generates enough electricity to watch a football match on TV, and for every eight banana peels we recycle enough energy can be produced to boil a kettle, but what happens to transform it into renewable energy once it leaves your home?

The 34,000 tonnes of food waste a year which comes from homes and businesses all over Gloucestershire is the ‘fuel’ for our anaerobic digestion process. Starting at the plant the food waste is separated from any packaging which is recycled where possible.  The food waste then enters a tank and mixed into a pumpable ‘soup’ while a macerator reduces food particles to below 12mm to ensure all particles can be fully heated in the next stage of the process.

This ‘soup’ is then heated to 70°C using the waste heat from the electricity generator, for one hour, to kill all unwanted pathogens.

Following pasteurisation, the food waste is pumped as a liquid into large tanks called digesters which contain cultures of anaerobic bacteria to digest the waste. During this process, the bacteria give off methane which we collect in large bags above the tanks. The methane (or Biogas), is then fed either to a generator to produce electricity which powers the site, or to the Biomethane plant to produce biomethane (similar to natural gas) which is pumped into the local Bishops Cleeve gas main.

The biogas that we produce can be stored on site enabling us to deliver energy when people need it - a huge advantage over other renewable systems that can’t efficiently store power or only produce it when the elements allow.  The remaining digested liquid is then screened and pumped into a storage tank ready to be used as liquid fertiliser which with its high values of nitrogen, phosphate and potassium, provides a very eco-friendly and sustainable resource producing bigger, stronger crops and a better yield per acre for farmers. 

At our Bishops Cleeve plant, we are very proud to have recently injected a record 11 million cubic metres of biomethane gas into the national grid - enough energy to power 10,000 homes for a year!

So next time you squeeze out a teabag or scrape your plates into your food waste caddy, remember you are playing a vital part in shaping Gloucestershire’s sustainable future!