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A Trip to Waste Tip (Jun08)

Dimmer landfill site near Castle Cary in Somerset is unusual.  It has a rather beautiful wooden eco-building within it’s boundaries, housing the Carymoor Environmental Centre.  School trips for nature talks and wildlife walks are a regular feature – and they do a lot to educate the public on the benefits of recycling.

I took my son Monty to have a look on a Saturday morning, along with a few members of the South Somerset Climate Action.  First stop was garden waste. Large piles of what looks like masticated tree bark at different stages of decomposition.

Send away your lawn cuttings, weeds or dead trees and they’ll be cut into little bits by a large shredder, and allowed to compost over a period of 12 weeks.  The end product is compost sold to the public – and returning to where it came from, gardens.

Food waste on the other hand – the stuff that’s been separated from the main domestic waste – is treated by an in-vessel composter.  The material is sterilised and turned into compost but isn’t given as much time to decompose and is therefore classified as ‘waste’ and given to farmers.

This would seem to be a missed opportunity on two counts. First, because there’s very little difference between it and garden waste compost – so why not treat it the same?   And second because it could be put in an anaerobic digester, where the methane produced from its rotting could be captured and used for energy.

Actually, one of the most striking things about Dimmer – and I presume most other landfill sites nowadays – are the pumps dotted around the obsolete heap.  These apparently collect the methane gas that’s emitted and sends it to a generator that turns it into electricity to be fed directly into the grid.

The pumps only manage to collect about 60% of the methane produced.  You can see some of it bubbling up in puddles on the ground – Monty was particularly interested in that.  Methane escaping is a real problem because it’s a powerful greenhouse gas – about 24 times worse for global warming than carbon dioxide.

That’s why it makes sense to collect any biodegradable or rotting waste and put it in an anaerobic digester – so all the methane can be used for energy.  It’s also why European legislation is trying to reduce or eliminate biodegradable waste from land fill sites.

One thing I did learn though was that composting waste – where it is exposed to air – does not produce methane.  So you’re getting useful stuff to put on the land andavoiding greenhouse gas emissions.

It’s surprising how much there is to learn about what we throw away.  And Carymoor is a good place to start.

Carymoor Environmental Centre – http://www.carymoor.org.uk/

South Somerset Climate Action – http://www.southsomersetclimateaction.org.uk  <Link no longer valid>
Recycle Somerset – http://www.recyclesomerset.info/

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