Title: [GreenYes] GHG and compost worms: Any thoughts, anyone?
This article appeared in the Telegraph (UK)
Wormeries 'may add to greenhouse gases'
By Charles Clover, Environment Editor
Last Updated: 6:01pm BST 06/07/2007
Worms may not be as environmentally friendly as the growing number of
gardeners who use them to help compost their kitchen scraps and grass
clippings believe, say scientists.
In fact, the greenhouse gases emitted by a large commercial worm composting
plant may be comparable to the global warming potential of a landfill site
of the same scale, according to the Open University.
This is because worms used in composting emit nitrous oxide - a greenhouse
gas 296 times more powerful, molecule for molecule, than carbon dioxide.
Landfill sites produce methane which is 23 times more powerful a greenhouse
gas than carbon dioxide.
Jim Frederickson, senior research fellow at the Open University's
technology, said: "We know from research in Germany that a third of the
nitrous oxide emissions coming from the soil are associated with worms.
"What we found from looking at large worm composting systems is that their
emissions could be comparable in global warming potential to the methane
from landfill sites."
The Government has said it wants to increase the amount of waste that is
composted to 40 per cent by 2010 and 45 per cent by 2015 - which is likely
to involve more commercial scale worm composting plants.
Red worms appear naturally in country compost heaps but over the past
or so a thriving trade has grown up in domestic wormeries which enable
people with space as limited as a balcony to compost their kitchen waste.
Domestic wormeries are dustbin-sized boxes formed from several trays, with
names such as Can-O-Worms, into which reared worms are introduced. Some are
even made to look like beehives.
The worms are laid out on lime and vegetable peelings. When they have
digested this material they move to another level in search of more food.
The lower trays of compost can be used and a tap allows the liquid
to be drained off as fertiliser.
The red worms used in composting are extremely efficient at breaking down
decomposing material such as kitchen scraps and other organic material but
they emit nitrous oxide in the process of digestion in the gut.
Mr Frederickson told Materials Recycling Week said: "Everybody loves worms
because they think they can do no harm but they contribute to global
"The amount of worm composting is very, very small and the amount of
landfill is huge. But landfill sites are quite well run these days and
possible to extract about half the gas they generate and use it for
"So the amount of nitrous oxide emitted by large scale worm composting is
something we should be looking at before we go further down that route."
Mr Frederickson said that the research he and his colleagues had done
very large commercial worm composting "beds" which build up large
nitrogen which is then emitted by the worms as gas.
It is unclear whether the same process goes on to the same extent in
domestic worm composting bins, but Mr Frederickson said: "We are clear they
will be producing nitrous oxide but maybe not to the same extent. They may
be more stable.
"Worm composting bins and compost heaps produce really good compost in a
decentralised way with no transport to landfill sites - which is a good
"But we must remember if we are evaluating this method against other
getting rid of wastes, such as landfill and incineration, that worm
composting can also be a source of greenhouse gas emissions."