I had an early start to get to London for the start of a workshop on AD – anaerobic digestion. It might be a bit weird but it’s a subject I’m rather passionate about. AD is essentially like composting in an enclosed system. It can be used to treat food waste, farm waste, sewage sludge and pretty well anything that’s slushy and compostable.
At the end of the process you get biogas, which can be used to generate electricity, heat boilers or as a vehicle fuel. And the remaining sludge left at the bottom is an excellent fertiliser – replacing energy-intensive agri-chemicals.
In 2006, when I was researching The New Green Consumer Guide, I realised that AD had huge potential but was barely being used. At the end of the year I organised a conference with South Somerset District Council called ‘Biogas – Explosive Potential’//. Amazingly the conference hall was full to bursting as interest in the issue was just getting going.
Back to the London event. Organised by BiogenGreenfinch, who describe themselves as a company pioneering food waste recycling for biofertiliser and renewable energy. The workshop entitled AD in the City – solving the urban food waste challenge was aimed at London councils encouraging them to use AD.
They appeared to be pretty keen on the idea. Ealing Council signed up with BiogenGreenfinch last year, for 5,000 tonnes of food waste but this is a very small proportion of the 2.5 million tonnes apparently produced by Londoners – and that’s only domestic food waste. Two other West London boroughs have just signed up – Richmond and Hounslow – and Hammersmith & Fulham look like they’ll be joining the fray. And following the workshop, other councils are apparently queuing up to have a look at whether it might work for them.
The London Councils are being encouraged by the London Waste and Recycling Board. This body was set last year to boost recycling – and is chaired by the London Mayor – Boris Johnson. They said that food waste in London is contributing about 210,000 tonnes of CO2 to the atmosphere each year.
I don’t think much food was wasted from the lunch served at the end of the workshop. Cooked by Oliver Rowe, who runs a restaurant near Kings Cross called Konstam, it was delicious. The unsual feature of the restaurant is that it sources 85% of its ingredients from within the M25. this means using apple balsamic vinegar, rape seed oil, rosehips, nettles, ground elder and wild garlic. It also means that the menu is very seasonal. We were served the most appetising pork with crunchy crackling and rhubarb sauce, served on a bed of lettuce with roast potatoes.
FOOD WASTE FOR FUEL… A DIFFERENT TAKE
If all possible food, garden and agricultural waste was converted to biomethane by 2020 it could replace half of the gas in the grid. This is just one of the revelations about the potential for anaerobic digestion presented to London Councils recently. BiogenGreenfinch, who are pioneering technology for recycling food waste, hosted a workshop titled ‘AD in the City – Solving the urban food waste challenge‘.
‘AD’ stands for anaerobic digestion. It’s essentially composting in an enclosed system but there are two main reasons why it’s a really brilliant solution for food waste. The first is that the methane released from rotting food no longer goes up to the atmosphere contributing to climate change. It’s siphoned off and used for energy. The second is that the waste left-over at the end of the process can be used for fertilising crops, replacing energy intensive agro-chemicals.
The biogas produced from AD can be put straight into the gas grid to fuel our cooking and heating, although this is something that’s not yet happening – it will do soon. It can also be used to generate electricity, fire boilers and even as a vehicle fuel.
Farm waste such as pig manure and wasted crops can also be put into AD systems – as well as sewage sludge. What’s surprising is that this idea is only just catching on as a mainstream solution. As early as 1895 there was a sewage sludge digestor producing biogas that fueled the gas lamps in Exeter.
The London Waste Recycling Board, set up last year to boost recycling, said that London produced 2.5 million tonnes of food waste and 40% of it still goes to landfill. They are very enthusiastic about the climate change benefits of producing energy from food waste – and are actively promoting and supporting AD in London.
BiogenGreenfinch already take 5,000 tonnees for food waste from Ealing Borough. They’ve just agreed a contract with other West London boroughs, including Richmond and Hounslow. And after their workshop, they say that other London councils are queuing to come and see whether AD might be the right solution for them. Let’s hope they think it is.
