Global warming is widely believed to be accelerated by increasing levels of atmospheric CO2. Wood and bio-fuels score very well on the environmental front as they return carbon to the atmosphere that was taken out only a few years before. Coal, gas and oil (fossil fuels) are releasing carbon into the atmosphere that was trapped and stored hundreds of millions of years ago.
Caring for the environment means using our resources with as little waste as possible. Furthermore it means using fuels with low CO2 emissions.
Less use less fuel through better insulation, improved controls and user education.