I had the opportunity to visit one of three biogas sites in London and it was amazing!
They are using food waste (both domestic and commercial) to feed massive anaerobic digesters and create biogas that is turned into electricity for the grid. They take around 35 000 tonnes of food waste per year and produce 31 000 MWH, pretty cool, right?
The site self-sufficient as it uses the energy it produces as well as using rainwater to mix with the food waste for digester.
First the food waste is dumped in the warehouse.
Different types of waste are mixed to get the right proportion of carbs, fats and proteins for the digester.
Then it is fed to the unpacking machine which removes all the plastic or bioplastic packaging.
What is left ideally is mix of plastic that can be later sent to incineration facilities in Europe.
When I asked what happens to biodegradable packaging (like those green food waste bags most of us are using) I was surprised to hear that they are considered to be a contamination. I have heard about it before from plastic recycling facilities, but surely when put in context of food waste they should be in the right place- apparently not. If they haven't biodegraded by the time the food waste have reached the facility they will be separated in the unpacking machine and end up in the "shredded plastic" pile. The packaging pile is sent for incineration that expects mainly plastic material, if there are to many biodegradable material mixed the humidity levels are too high and the whole pile might be rejected and would have to go to landfill.
The unpackaged and mixed food waste is then fed to the small digester container - where the chemical components are tested and have to be approved by site biologist to then be fed to the main digester containers.
The food waste takes around 42 days to compost and release biogas, it is kept around 35C to create the perfect temperature for the anaerobic bacteria.
Once in 3 months or depending on demand the digestate is drained, filtered (to capture microplastics or other particles that haven't decomposed) and sold to farmers as liquid fertiliser.
A big part of the the biogas facilities system is devoted to managing the odour, the anaerobic composting smells very bad and depending on wind can reach far. There are air filtration system that uses wood and type of bacteria that reduces smell as well as fresh air feed to the warehouses every few seconds.
I have to say that the smell wasn't half as bad as I expected, not sure if it is due to the efficient fresh air systems or cold weather (I imagine in hot summer day it might be a different story).
As for the future of the food waste, biogas looks promising, from people working there it seems like the main issue is getting people and companies to actually recycle food waste separately and change the old practices of one bin- one landfill.
I was told a story of couple years ago when company was struggling to feed the digesters and had to look for food waste outside of London! Like London doesn't have plenty of food waste itself!
So, have you got your food waste bin already?
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