I once read about someone who made a compost bin against one of the house's walls, thereby helping to heat that wall.
I also
think I remember reading about someone using compost to preheat water.
But no links for either
EDIT: I just saw where you are. I guess that you can compost for the whole year round. In many places composting happens only during the warmer months, when heating is not needed.
EDIT#2: The more I look at my city's problems with waste management (i.e. wasting trash, instead of reusing it), the more I'd like to start up a large composting set-up. This would reduce the city's wastestream by 30%-40% and give quite a bit of good soil, plus any extra energy (heat + methane) would make the project more feasible. With the composting happening inside a building, the heat would be able to keep it running year round, with a surplus in the summer.