KEY POINTS:
Microbes discovered in the depths of a French lake may hold the key to dealing with the problem of belching cattle and sheep, source of a third of New Zealand's greenhouse gas emissions.
Dr Gerard Fonty, of Blaise Pascal University in Clermont-Ferrand in central France, discovered the methane-consuming micro-organisms in a nearby volcanic crater lake.
The 6000-year-old Lake Pavin is unusual in that its waters are in layers that do not mix, resulting in an anaerobic or oxygen-free zone in the bottom third of its 92m depth. Geochemists studying the lake noted that its deepest zone contained methane, but none reached the surface.
Fonty, whose field is the microbial ecology of lakes and other freshwater ecosystems, established that this was the result of a previously unknown microbe which had evolved to live on the methane produced in the sediment at the lake bottom.
Methane-consuming micro-organisms have been found before, but only in salty marine environments. These are the first from a freshwater source.
And while their natural habitat is cold, about 4C, Fonty and his team have succeeded in growing them in a laboratory at room temperature.
Fonty was able to recognise their potential significant because in the past his field of research was the microbiology of the rumen.
He is an old friend and colleague of Dr Keith Joblin, a senior scientist with AgResearch in Palmerston North and principal investigator for the pastoral Greenhouse Gas Consortium, the body funded by farmers and taxpayers which is looking for ways to suppress emissions of enteric methane.
Collaboration with Fonty and his colleagues is an important new avenue of that research, which had been confined to trying to block the methane from being produced in the first place.
But Joblin stresses that it is still in its early, fundamental phase.
"Everyone would love to do the quick and dirty experiment of introducing them to the rumen, but there is a lot we need to know first."
They are typical anaerobic organisms in that they grow and multiply relatively slowly and are fastidious, needing exactly the right environment.
"And they probably work together with other organisms," Joblin said
If introduced as immigrants, so to speak, to the teeming, complex microbial population of the rumen, would they survive and thrive?
Or might they prove antisocial? The biosecurity issues are serious. But so is climate change and methane is a potent greenhouse gas.
New Zealand's cattle and sheep produce the equivalent of about 24 million tonnes of carbon dioxide a year, about a third of national emissions of greenhouse gases - a much higher proportion than in other countries with Kyoto Protocol obligations.
"It's our problem and we can't expect other people to solve it for us," Joblin said.
The methane belched also represents a waste of feed of anything from 3.5 to 7.5 per cent.
Scientists have been looking to see if methane production can be reduced by altering the pasture, or by developing vaccines that stimulate antibodies which restrict the activity of methane-producing organisms in the rumen.
Research is also going on into why one cow produces more or less methane than the cow next to it.
So far no "silver bullet" has emerged.
"It may be that we need a number of bullets, saving 10 per cent here, 10 per cent there," Joblin said.
But at least the humble creatures from the bottom of Lake Pavin provide a new direction from which to attack the problem.
The problem
* Methane from the digestive systems of cattle and sheep is one of the main sources in NZ of the greenhouse gases blamed for global warming.
* At current carbon prices and exchange rates, it will represent a cost to the taxpayer of about $200 million by 2012. That will increase if emission reduction targets become more ambitious and carbon prices rise.
* It is not just our problem. Globally, farming of ruminants accounts for about a quarter of man's emissions of methane, a very potent greenhouse gas.
* Because it is more of a problem here than in other Kyoto countries, New Zealand is leading research in the field.
* But it is looking for international collaborators in the research effort and has found a promising ally in France.
