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Life Cycle Assessment: Principles, Practice and Prospects
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carbon assessment – that conducting carbon-only assessment involves the risk that technolo-
gies with other significant environmental impacts may be chosen.
10.3.3 Policy implications
Clearly, there is an extensive range of assumptions, uncertainties and situations in which
biomass may be used for apparent carbon benefits. Many technologies and practices are
untried, economically marginal or submarginal, or not being adopted optimally for carbon
savings due to perverse incentives in the market. Given this situation, the current growth of
interest and commencement of carbon trading schemes and various support mechanisms is
appropriate in general terms. However, new policies and mechanisms must be carefully devel-
oped and based on ‘complete’ LCA-based information, taking into account all direct and
indirect emissions and impacts, otherwise new perverse incentives may be created.
For example, a proposal for a biomass energy project was designed to generate electricity,
displacing emissions from a coal-fired plant, and to use the sawdust and offcuts from a sawmill
as feedstock (A. Cowie, pers. comm., 27 November 2007). The sawmill residues were being
used as feedstock at a particleboard plant and, as part of the project, they were to be diverted to
the biomass energy project. As a result, the particleboard manufacturer was required to use
freshly harvested low-grade timber as feedstock, with particular implications for the particle-
board plant. Because the green feedstock has a high moisture content and will need to be dried
before use in particleboard manufacture, the dryer energy (usually supplied as natural gas)
must be accounted for in a full LCA.
Calculations (Cowie and Gardner 2007) indicate that the increase in emissions from parti-
cleboard manufacture, due to the higher fossil fuel requirements to harvest, transport, chip
and dry the green biomass, can amount to nearly 20% of the emissions displaced by the
biomass energy project. The net emissions reduction would be 18% greater if the freshly har-
vested timber was used by the biomass energy project and the dry sawmill residues continued
to be used for particleboard. This result is specific to the particular project in question. It is
affected particularly by the fossil fuel displaced, the efficiency of the biomass energy project
compared with the displaced coal-fired electricity plant, the moisture content of the sawmill
residues, and the efficiency of the dryer in the particleboard plant. Whether the newly har-
vested timber is used for biomass energy or for particleboard, the carbon stock in the forest
will be reduced, causing an additional indirect impact that further diminishes the net green-
house benefit of the biomass energy project.
This example illustrates that indirect consequences can reduce the net greenhouse gas
mitigation benefits of a biomass energy project. Such ‘leakage’ must be taken into considera-
tion in devising incentives for renewable energy projects and in determining the credit earned
by such projects.
In summary, there are various assumptions to be made in calculating the net savings in
emissions associated with the substitution of fossil fuels by biomass. Each assumption, however,
can greatly vary the overall ‘saving’ achieved. As an example, while ignoring the credit due to
the avoided use of fossil fuel, one study into emission factors for electricity generation from
burning wood produced a range from –1.9 kilograms of carbon dioxide per kilowatt hour (kg
CO /kWh) to 6.8 kg CO /kWh (Reijnders and Huijbregts 2003). While the range of values was
2 2
primarily a result of different assumptions about the extent of carbon sequestration, this nev-
ertheless shows the potential magnitude of uncertainty associated with the calculation of
emissions for substitution. Even when reporting for compliance with international standards,
uncertainties remain in particular cases of carbon offset and biomass energy technology
projects. Although these uncertainties do not overall constitute a case for pausing in the rapid
adoption of such technologies and supporting policies, regulations and support mechanisms

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