02 November 2008

AD Plants Produce Lovely, Rich Organic Matter - Daily Telegraph

Biogas converters - making fuel and fertiliser from biodegradable waste
By Julia Hailes

Good composting doesn't just mean throwing your food waste into a composting bin and forgetting about it, which is pretty well what I do.

It's actually quite important to get a reasonable mix of wet and dry material and even to turn it over on occasions.

Getting it right, not only means that it will produce lovely, rich organic matter to put on your garden but will also reduce your carbon footprint.

It's not just the CO2 being released into the atmosphere but methane too - which is about 24 times worse in terms of its global warming impact.

Most of the food we throw away in this country ends up in landfill sites, where methane emissions are a real problem.

Not so long ago all these gases were allowed to waft up into the atmosphere or were simply burnt off with flares to stop explosions.

Nowadays, most dumps will be scattered with gas collectors that siphon off some of the methane and use it to make electricity.

But this isn't a very efficient process, which is why there's strict European legislation aimed at reducing the amount of biodegradable waste going to landfill - and hence the amount of gas from rotting waste that adds to the blanket of greenhouse gases warming our planet.

A couple of weeks ago I went to visit one of the few emerging biogas plants in the country.

At Biogen (www.biogen.co.uk), near Bedford, they take in 30,000 tonnes of food waste and put it in large anaerobic digestors (ADs). Actually, they have to remove the packaging first, but the principle is pretty simple.

The digestors are really silos designed to speed up the rotting process and collect the methane that's released. The brilliant thing about it is that all the gas can than be used for electricity generation - or even for vehicle fuel.

And what's left behind is a great fertiliser - so almost nothing is actually wasted.

AThe following additional related UK Daily Telepgraph articles are available:

- Recycling in action at Somerset landfill site
- California converting cow dung into biogas
- Recycling dreamland in Dagenham.

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