23 February 2017 - Duncan Brack
Although most renewable energy policy frameworks treat biomass as carbon-neutral at the point of combustion, biomass emits more carbon per unit of energy than most fossil fuels.

Summary
The use of wood for electricity generation and heat in modern (non-traditional) technologies has grown rapidly in recent years, and has the potential to continue to do so.
The EU has been, and remains, the main global source of demand, as a result of its targets for renewable energy. This demand is largely met by its own forest resources and supplemented by imports from the US, Canada and Russia.
Countries outside the EU, including the US, China, Japan and South Korea, have the potential to increase the use of biomass (including agricultural residues as well as wood), but so far this has not taken place at scale, partly because of the falling costs of competing renewables such as solar PV and wind. However, the role of biomass as a system balancer, and its supposed ability, in combination with carbon capture and storage technology, to generate negative emissions, seem likely to keep it in contention in the future.
Although most renewable energy policy frameworks treat biomass as though it is carbon-neutral at the point of combustion, in reality this cannot be assumed, as biomass emits more carbon per unit of energy than most fossil fuels. Only residues that would otherwise have been burnt as waste or would have been left in the forest and decayed rapidly can be considered to be carbon-neutral over the short to medium term.
One reason for the perception of biomass as carbon-neutral is the fact that, under IPCC greenhouse gas accounting rules, its associated emissions are recorded in the land use rather than the energy sector. However, the different ways in which land use emissions are accounted for means that a proportion of the emissions from biomass may never be accounted for.
In principle, sustainability criteria can ensure that only biomass with the lowest impact on the climate are used; the current criteria in use in some EU member states and under development in the EU, however, do not achieve this as they do not account for changes in forest carbon stock.
Also see Woody Biomass for Power and Heat: Impacts on the Global Climate, which assesses the impact of the use of biomass for energy on greenhouse gas emissions, how these are accounted for under international climate accounting rules, and analyses the sustainability criteria currently in use and under development to minimise negative impacts.