Biomass (plant material) can be a renewable energy source, but importantly, only if the rate of extraction does not exceed the rate of production, as non-renewable biomass usage can easily occur, such as the historical Deforestation during the Roman period and the present Deforestation of the Amazon Rainforest.
Through the process of photosynthesis, plants capture the sun’s energy. When the plants are burnt, they release the sun’s energy they contain. In this way, biomass functions as a sort of natural battery for storing solar energy.
In general there are two main approaches to using plants for energy production: growing plants specifically for energy use (known as first and third-generation biomass), and using the residues (known as second-generation biomass) from plants that are used for other things. See biobased economy. The best approaches vary from region to region according to climate, soils and geography.
The proportion of truly renewable biomass in use is uncertain, as for example peat, one of the largest sources of biomass, is sometimes regarded as a renewable source of energy. However due to peats extraction rate in industrialized countries far exceeding its slow regrowth rate of 1mm per year, and due to it being reported that peat regrowth takes place only in 30-40% of peatlands, There is considerable controversy with this renewable classification. Organizations tasked with assessing climate change mitigation methods differ on the subject, the UNFCCC classify peat as a fossil fuel due to the thousand plus year length of time for peat to re-accumulate after harvesting, another organization affiliated with the United Nations also classified peat as a fossil fuel. However, the Intergovernmental Panel on Climate Change (IPCC) has begun to classify peat as a “slow-renewable” fuel, with this also being the classification used by many in the peat industry.
Further controversy surrounding the classification of all biomass as “renewable” centers around the fact that depending on the plant source, it can take from 2 to 100 years for different sources of plant energy to regrow, such as the difference between fast growing switch grass and slow growing trees, therefore due to the high emission intensity of plant material, researchers have suggested that if the biomass source takes longer than 20 years to regrow, they argue the plant source should not be regarded as renewable from a climate change mitigation standpoint.
As of early 2012, 85 of 107 biomass plants operating in the U.S. had been cited by federal or state regulators for violating clean air or water laws over the past five years. The Energy Information Administration projected that by 2017, biomass is expected to be about twice as expensive as natural gas, slightly more expensive than nuclear power, and much less expensive than solar panels.
