- Hydrogen gas
- Alcohol fuels
Biomass is often made out of plant matter grown to generate electricity or heat. Biomass can be converted into other types of energy, too, such as methane gas, or fuels used for transportation, such as ethanol or biodiesel fuels.
The downside of using biomass as an energy source is that is creates air pollution, sometimes at higher levels than more traditional fuel sources like coal or natural gas. Air pollution is one of the causes of COPD.