To find out when your food waste is collected, and what you can put in your food waste caddy please visit your district council website:
- Cherwell District Council
- Oxford City Council
- South Oxfordshire District Council
- Vale of White Horse District Council
- West Oxfordshire District Council
Video about food waste
Watch our film to find out how your food waste is recycled'
Read video transcript
Separately collected food waste from the kerbside is brought to an Anaerobic Digestion facility for recycling. The first stop is the weighbridge, where the vehicle full of food waste is weighed so we know how much food is being recycled.
The vehicle then drives into an enclosed reception building where it tips the food into a large bunker. Business waste from supermarkets, restaurants, and even liquid waste from factories, breweries and dairies is mixed with household food waste. It is passed through the mouth of the plant where it is chewed, any contamination removed, and the food waste soup is created, ready for digestion.
Before digestion this needs to be pasteurised, to kill off any bad bacteria. This is like cooking the soup. It is held in giant vats where it is heated to 70oc for one hour. They are heated by using recycled heat from the gas engines. The pasteurised soup is then fed to one of the digestion tanks. There are five tanks on site. Each tank is like a giant stomach, where good bacteria eat the food, converting it into biogas, or methane, and a fertiliser called digestate.
The food waste is pumped through the five tanks, and this takes around 100 days.
Like the bacteria in our stomachs, the good bacteria break down the food waste to extract as much energy as possible. Once all the biogas has been extracted, we are left with a nutritious organic fertiliser.
Because the digesters are like giant stomachs, they have to be tested every day , in our lab, to keep them healthy.
The digesters have to be kept at body temperature, and are heated by using recycled heat from the gas engines.
The biogas is stored in the roofs of the tanks. It is then fed into two large engines which, just like a car converting fuel into energy, converts the biogas into electricity. This is fed into the national grid through transformers on site. The engines produce enough energy to power 4,200 homes.
The nutritious organic fertiliser is a black liquid which is taken from the plant and spread as a valuable fertiliser on local farmland. This helps improves crop yield, and replace artificial fertilisers.
Vehicles bring in approximately 120 tonnes of food waste every day. This means, in addition to powering our homes and helping to grow crops, over 40,000 tonnes of food waste is kept out of landfill.
Your questions answered
Why can I put cooked food waste in my food waste collection but not in my home composter?
The food waste collected by your district council will be taken to one of three composting sites provided by Oxfordshire County Council and our contractor, Severn Trent Green Power Ltd.
These composting sites are highly controlled to stop smells escaping and ensure birds and vermin are not attracted to the facilities. This means that the facilities can compost cooked and uncooked food including meats, oils and fats.
Can I use plastic bags to line my food waste caddy?
If you live in Oxford City, South Oxfordshire, Vale of White Horse and West Oxfordshire you can. If you live in Cherwell, you need to use compostable bags. More information about using liners.
Should I stop home composting?
Making your own compost at home is the most environmentally friendly way of dealing with your vegetable peelings and other uncooked food waste. However, meat and fats and cooked food waste cannot be composted at home. It is likely to create nasty smells and attract vermin.
How is the food waste processed?
Severn Trent Green Power operates three plants within the county, which re-processes food waste into organic fertiliser, which is applied to farmland as a soil improver. Two technologies are used: In-Vessel Composting and Anaerobic Digestion.
In-Vessel Composting (IVC)
Food waste is shredded and treated in large tunnels for three weeks. Air is pumped through the tunnels to speed up the decomposition process. The waste is then transferred to another set of tunnels and the process is repeated to ensure that all waste has fully broken down into compost. This compost is stored in a maturation area, and is then refined on site to sell to the farming industry.
The IVC plant at Ashgrove Farm, Ardley has now been built and is accepting food waste from Oxfordshire.
Anaerobic Digestion (AD)
Food waste is processed in a series of large sealed vats, or 'digestors', where it is heated and stirred for 72 days. This process releases methane and converts the food waste to a valuable fertiliser, which is pasteurised and stored on site for up to six months and then sold to the farming industry.
The methane gas arising from the process is piped to an on-site engine to generate electricity which can be fed into the National Grid. It is expected that the electricity generated from the AD process will be sufficient to power 10 per cent of Oxford's homes.