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13 November 2014

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You are in: Shropshire > Nature > Environment > Ludlow's green monster

Ludlow's biodigester

Ludlow's biodigester

Ludlow's green monster

There's a monster in Ludlow and it needs to be fed. Or, the alternative way of starting this feature - What happens to the stuff that goes into green wheelie-bins from all over South Shropshire?

It's big, it's very big, and the whole of South Shropshire is feeding it.

This isn't a scenario from a 1950's B-movie. It isn't science-fiction. It's the Ludlow biodigester.

We're all being persuaded to try to save the planet and there are so many ways of doing it. Recycling is everywhere but different local authorities have different ways of approaching the subject.

Most of us have easy opportunities to recycle newspapers and glass bottles, but what to do with kitchen and garden waste?

Food for the digester

Food for the digester

South Shropshire's approach to domestic waste is to offer all the residents a box for newspapers bottles and cans, a black wheelie bin for stuff that can't be recycled and a green wheelie bin.

The green bin is the interesting one - that's the place to put green waste - sounds obvious, but it raises two immediate questions: what is green waste and what happens to it when the bin's emptied?

Green waste can be stuff from the kitchen - food scraps, including meat, vegetable peelings, cardboard packaging - but definitely not plastic.

From the garden lawn clippings, weeds, the bits you don't know what to do with when you've pruned the roses - but definitely not soil.

The reason for all these likes and dislikes leads on to the second question - what happens to all this stuff?

When the wheelie bin is emptied into the back of the truck, it makes its way to Coder Road in Ludlow where it's fed to the biodigester.

The truck dumps it onto a concrete floor, it's dropped into the biggest, toughest garden shredder you've ever seen and a conveyor belt takes it to a huge drum where it's made into a soup to feed the monster at the heart of the digester - bacteria.

That's the key to the process - a thriving colony of bacteria that break the waste down. So instead of your waste going into a landfill where it just takes up space for a few thousand years and giving off methane, it gets transformed into a useful compost, a liquid fertiliser that can be used in the farmer's field... and methane.

But unlike in a landfill where the methane just pollutes the atmosphere, the methane from the digester is captured to form a useful product. It can be burned and used to heat water and power radiators. It could even be used to generate electricity or power vehicles.

The bacteria, like any other living thing, needs a balanced diet, so the best thing is a good mix - grass clippings are great, but if that's all there is there will be a huge case of indigestion. Cardboard is welcome, but not in industrial quantities, otherwise the digester would choke.

Russell Mulliner - the human face of the digester

Russell Mulliner - the human face of the digester.

The people running the digester are intensely proud of it and look after it like a baby, so they are justifiably upset if people send it junk food. You may be tempted to put your potato peelings in a supermarket carrier bag - don't - not even if you think the bag is biodegradable. Bags made of corn-starch are available and can be used - or you can wrap food waste in a couple of sheets of newspaper.

Most people try to do it right, but Russell Mulliner of Greenfinch, the company that runs the digester says that some have eccentric views as to what constitutes garden waste... hedge clippings good - broken garden forks bad. And kitchen waste... a stale loaf good - an old toaster bad.

But surely the biodigester would smell terrible? Well, no. Six weeks after it began to operate, people from a neighbouring unit went round to ask when it was due to start - they hadn't noticed.

So with the biodigester, we seem to be in a win-win situation. You get rid of your rubbish and in return we get useful products. But this is one monster we need to look after so it can look after us.

last updated: 28/08/2008 at 11:05
created: 19/05/2006

You are in: Shropshire > Nature > Environment > Ludlow's green monster

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