yes, they can. The Green Microgym in Portland, Oregon, which opened in August, is the first in the US to convert the efforts of gym bunnies into electricity. Its three specially adapted bikes and the four-person "Team Dynamo", which combines cycles with hand cranks, can generate up to 1000 watts. What's more, you can emulate them in your own home by investing in a Pedal-A-Watt. When hooked up to a normal bicycle on a stand, this device allows a cyclist to generate up to 200 watts of electricity. That's enough to power a large TV while you go. Or you can store the energy you produce in a battery and use it later. An hour's worth of cycling could power a low-energy light bulb for 8 hours. (New Scientist

This idea can be extended so that those people who contribute nothing to society can now do their bit to make this a green and pleasant land. Prisoners live in a hotel with full board for free, the unemployed do nothing and get paid for it. They can now spend their time generating electricity equivalent to their drain on society. If they do not attend such social programmes they would be required to stop breathing for the equivalent length of time needed to equate to the energy they could have produced. Their carbon footprint would thereby be minimal.