Woody plants can be turned into low-carbon fuel
While alive, trees and shrubs remove carbon dioxide from the atmosphere and store it. If they are burned as fuel, they release CO2 back into the air, but the net impact on atmospheric levels is essentially zero since their carbon is simply being returned to the atmophere. (Harvesting and processing woody fuel, or biomass, takes some energy and if fossil fuels are used for this, there will be some some net CO2 emissions.) The National Renewable Energy Laboratory gives more information on the topic.
Woody biomass can be used for energy in a great number of ways. It can be burned to provide heat (for example, in a fireplace or an industrial furnace) or to create steam for generating electricity.[[Ifie, Tony. “Biomass Initiative.” (PDF) Washington State Department of Natural Resources, July 20, 2009.]] It can also be made into a combustible gas that can be burned more-or-less the way natural gas is burned, for example, to make electricity in a gas turbine.[[Larson, E. D., and R. H. Williams. 2001. “A review of biomass integrated-gasifier/gas turbined combined cycle technology and its application in sugarcane industries, with an analysis for Cuba.” (PDF) Energy for Sustainable Development V(1): 54-76.]] This latter technology (gasification) isn’t routinely used on a commercial scale yet, but demonstration plants exist in Denmark, Austria, Germany and elsewhere. And finally, biomass can be converted into a number of liquid transportation fuels, including ethanol, synthetic gasoline or synthetic diesel.[[National Academy of Science, National Academy of Engineering, and National Research Council. Liquid Transportation Fuels from Coal and Biomass: Technological Status, Costs, and Envirornmental Impacts. (Abstract) The National Academies Press..]] [[Larson, Eric. “Biofuel production technologies: status, prospects and implications for trade and development New York,” (PDF) 2008.]]