Though operating expenses for the biogas plant are considerable, the combination of electricity savings, power production and carbon credits makes it profitable, Horrevorts says.
Horrevorts, who is a biological researcher rather than a professional farmer, says that with financial incentives through electricity subsidies, it could become standard practice for ordinary farmers. About 50 commercial biogas plants operate on farms in the Netherlands, and the practice is spreading across industrial livestock farms around the world.
"I think in the future every pig farm will have a biogas plant," he says.
But at euro1 million ($1.3 million) for a big plant like Sterksel's, it's a rich man's answer to climate change.
About 70 percent of the world's agriculture is on small land holdings in the developing world, which complicates climate politics, says Antonio Hill of the nonprofit group Oxfam International.
"It sounds like a big pot," Hill said, but dealing with farming is tougher than with industries. "You're talking about tens of thousands of sources of industrial emissions in rich countries. That's a lot more manageable than hundreds of millions of agricultural operations."
Measuring and verifying carbon reductions from soil conservation, grassland management and livestock is complicated, and those reductions may not be permanent. Trees planted to soak up carbon from the air, for example, can always be cut down and burned.
In the past year, much effort has gone into quantifying emissions from deforestation in the tropics and ways to compensate countries like Brazil or Indonesia for protecting their rainforests. But no comparable effort has gone into accounting for the vast farming sector.
Another obstacle to an agreement in the U.N. talks is the suspicion that rich countries will meet a large part of their emissions reductions by buying credits on the international carbon market rather than constraining their own industries. In other words, they would buy credits from farmers to reduce their carbon footprint, in the same way the offset company bought credits from the Sterksel pig farm.
"If the idea is that rich countries will do most of their reductions through offsets, a lot of developing countries have a big problem with that," says Hill, speaking from his home base in Bolivia.
Hill says he expected nothing more in the Copenhagen agreement than "place holders," or general statements that can be filled in later with details. But Smith, the scientist from Aberdeen who co-wrote the agriculture section in the 2007 report by the U.N's Intergovernmental Panel on Climate Change, says including agriculture in the Copenhagen agreement would provide a source of capital from rich countries to poor ones.
"It would be a desperate shame if it were blocked for political reasons," he says.