Page 162 - Biofuels for a More Sustainable Future

148 Biofuels for a More Sustainable Future

Given the fact that a large fraction of the environmental and human
health impacts of biomass are traceable to the direct emissions during oper-
ation, it is useful to explore the effects of differing pollution control measures
via sensitivity analyses. Fig. 5.9 shows how the key affected indicators
respond to
– The absence of flue gas desulphurization (FGD).
– The addition of selective catalytic reduction (SCR), reducing NOx emis-
sions by 85%.
– An improvement in overall plant efficiency from 35% to 40%.
The figure shows all impacts relative to the base case (FGD, ESP, low-NOx
burners, and an efficiency of 35%). As shown in the figure, when FGD is not
implemented, the overall life cycle acidification and photochemical smog
impacts of biomass power increase by 12%–134%. This difference is partic-
ularly notable in the case of miscanthus due to its potentially higher sulfur
content per unit energy content. As already observed from Fig. 5.7, biomass
already performs quite poorly for these impact categories, therefore this sug-
gests that legislation should be enacted to ensure FGD is fitted.
The use of SCR reduces the impacts shown in Fig. 5.9 by an average of
6% with the most dramatic effect seen in the eutrophication potential of
wood-fired power plants (a reduction of 18% over the life cycle).
Thus it could be concluded that the most important considerations are
the use of FGD and the overall efficiency of the plant. However, since the
best case only reduces impacts by an average of 18%, the rest of the life cycle
requires attention for biomass to convincingly compete against wind or
nuclear power. Eutrophication and ozone layer depletion, for instance,
are mostly attributable to the importation of pellets by sea, therefore the
transport stage is the key area for improvement.
These insights, based on life cycle thinking, can help to scrutinize policy.
For instance, the Industrial Emissions Directive includes NO x emission
limits of 200mg/m 3 which necessitates selective catalytic reduction
(SCR) (Directive 2010/75/EU, 2012). However, while the earlier analysis
shows that SCR is beneficial, it suggests that policy effort might best be
deployed elsewhere.

3.2 Future electricity scenarios for the United Kingdom
As demonstrated before, LCSA can provide useful insights for present-day or
near-term decision-making in the energy arena. However, energy strategy
often requires longer term thinking. Future scenario analysis is a useful tool