For the past couple of years Heart of BS13, based at Hartcliffe City Farm, have been tackling Bristol’s food waste issues and using that waste to make amazing nourishing compost for their flower farm.
Why is it so important to keep food waste out of the general waste?
The most recent statistics from Bristol Waste have shown that food waste makes up a third of our total general waste which lines up with most of the rest of the UK. Bristol is known for being a Green City especially after it received the green capital award in 2015. However, food waste still remains a major contributor to landfill and greenhouse gases.
It is easy to miss the importance of keeping food waste out of the general waste bin. However, it is actually THE WORST material we can put into landfill as it decomposes so quickly and is one of the biggest sources of methane to our atmosphere. Although methane’s lifetime in the atmosphere is much shorter, methane is 28 times more damaging then carbon, making it a major short-term contributor to climate change.
In Bristol we have an incinerator for our general waste which only 2/3rds of our waste fits into, so if we stop putting food waste in there we would stop needing to send our general waste to Europe for landfill! On top of that, it takes a huge amount of energy for the incinerator to burn wet food waste.
Bristol has municipal food waste collections and this gets processed in a giant anaerobic digestor. The digester collects all the methane produced by the food and sells it back to the grid and it is enough to power 9,000 homes each year in Bristol, or, the whole of Avonmouth, including all the recycling plants!
What is left after they have spun the water off is a kind of compost called ‘cake’. We also call what’s left from sewage works ‘cake’. These are both examples of large-scale closed loop systems, however they are far from completely closed as there is still a lot of carbon produced from the whole huge operation which includes the transporting and processing this waste as well as the left over cake. So, in an ideal world, we would do this on a much smaller, local scale, composting as much organic matter as we can in our own gardens or in a local community compost scheme, preventing all of that carbon production. Which is what we have been trialling here at Heart of BS13!
What we have been doing to change habits
So far I have been working with over 60 households throughout BS13 to support them to change habits and learn the value of local composting and separating food waste form the general waste. Targeting households without a current food waste bin, I’ve been using our E-cargo Trike to collect food waste from these households and composting it on the flower farm with a Ridan food waste composter. I send text reminders and knock on doors if they have forgotten to put the waste out, to support them to build new habits.
The composting process is aerobic and harnesses the power of natural decomposing methods, supporting it with insulation and cogs to make it easy to mix the food waste into woodchip, speeding up the first part of the process and effectively sterilising it from dangerous pathogens like salmonella and listeria which thrive in cooler anaerobic conditions. The woodchip we use for it is another waste product material which we have delivered from local tree surgeons and gardeners. All participants are invited to a compost tour to see how the magic happens!
We have also worked with four schools so far in BS13, each time getting a group of kids to take responsibility for composting their school’s food waste and we show them how to do it at the farm. Kids absolutely love this magical scientific process, which brings them hope for improving the local wildlife, direct responsibility of dealing with their own waste materials as well as tackling climate anxiety. Climate anxiety is something that really needs to be addressed especially in our young people, they need to have hope for the future and composting is a fantastic, practical and magical way of doing this. Not only does composting save masses of carbon from going into the atmosphere but using the finished product ‘heals our soil’, which means it puts life into the soil and enables plants to store carbon in the soil. Plants do this by reacting with sunlight and carbon dioxide in the air to produce carbon, which it uses as building blocks for growth, and oxygen, a waste product, which it releases back into the air. It also stores carbon in parts of itself like carrots and root vegetables, which are just stored energy for the plant and they actually trade carbon with surrounding organisms in the soil, like bugs and bacteria and mycelium, for other essential nutrients which they can’t produce themselves. The process of carbon being taken from the air and stored in the earth is also known as ‘carbon sequestering’ in the scientific world and so is actually a minus-carbon process. The top 6 inches of soil is the second biggest store of carbon on the planet after the ocean, yet a third of our soil around the world is depleted due to the stripping and removing of organic matter, leaving the soils degraded and lifeless. In fact, there are studies that suggest that if we all look after our soils right now, we could get back to pre-industrial levels of carbon in the atmosphere in only 6 years!
So, in an ideal world, schools learn to compost their food waste on site or nearby, and use the compost to grow more food. By doing this they would also be feeding the bottom of the food chain, so all surrounding wildlife would be able to feed off the healthy soil. This should become an integral part of their curriculum and teaches them responsibility and care for nature and the earth!
We also have some local businesses within a 3 mile radius saving their food waste for us and paying us to collect and compost it for them, the most environmentally-friendly waste collection service possible! By saving 3.5 tons of food waste with us over a year, they save 5 tons of carbon from going into the atmosphere, and that doesn’t even take into account the carbon sequestering! We are looking currently for more businesses to join us on this mission!
Written by Jenny Liggitt – Closed Loop Compost Coordinator