New government research adds to biomass emissions controversy
- 13 Mar 2013, 12:50
- Mat Hope
Credit: Drax Group
Government research examining emissions from biomass
power generation seems unlikely to settle arguments over how
polluting it is. But as campaigners and industry continue to argue
about whether biomass could cut greenhouse gas emissions, the
government has ambitious plans to increase the amount in the UK's
Biomass - carbon neutral power?
Plants, trees and crops can all be burned to generate
electricity. One advantage of such 'biomass power' is that the
greenhouse gases emissions from burning plants get reabsorbed as
more plants grow. In theory, this means biomass power could be
effectively carbon neutral - as this video from Drax power station,
which is in the process of switching from coal to burn mostly
This should make biomass an attractive option for the
government, as it aims to reduce UK greenhouse gas emissions 80 per
cent by 2050. The government has outlined proposals to get up to
11 per cent of the UK's total primary
energy demand from biomass by 2020, and last week passed
an amendment adding new subsidies for
biomass generation, if it can emit
60 per cent less than fossil
Calculating biomass emissions
That's all fine in theory, but projecting actual
biomass emissions is quite complicated, and very dependent on
assumptions about what is going to be burned and where it comes
For example, one of the main sources of biomass is
wood. Trees take a long time to grow, which can produce a
significant time lag between emissions being released and being
absorbed. This has to be factored into calculations about emission
reductions. Or, if wood is burned that otherwise would have been
used for building, it could also result in extra emissions.
This is why the Department of Energy and Climate
Change (DECC) has developed a
calculator, which considers twelve
different scenarios for producing and burning biomass and works out
the associated emissions. But startlingly, the preliminary results
suggest biomass generation actually produces more emissions than
burning coal in five out of the twelve scenarios.
This issue hasn't come out of nowhere, as calculating
biomass emissions has previously proved controversial.
Environmental NGOs released a report last year
claiming biomass can be
"dirtier than coal", largely based on a
paper by Princeton academic Timothy
Searchinger. It argues that DECC's bioenergy strategy doesn't
adequately account emissions from biomass, meaning the government
is "significantly overestimating the climate benefits of generating
electricity from wood".
Searchinger actually calculates that over a 20 year
time period, the emissions from power generation using wood are 80
per cent higher than from coal - meaning biomass is obviously far
from being a carbon neutral power source.
But the analysis is based on using whole trees as
biomass. This prompted a firm response from the Forestry
Biomass Energy Centre, which says
Searchinger's paper "bases its main contention on the (rejected)
worst case scenario, and the "Dirtier than Coal" report appears to
base its fundamental arguments on this misleading and uninformed
Trade body the Renewable Energy Association (REA),
which represents the biomass lobby, says Searchinger's paper
overlooks the fact that selling whole trees as biomass "would not be
financially viable" for landowners. By-products from forestry such
as sawdust, bark and thinnings - known as residues - are more
likely to be used, as they can't be used for anything else. The
market should largely take care of excluding the types of materials
Searchinger envisages being used for fuels, REA argues.
The new calculator captures this disagreement. It
suggests that burning biomass from residues produces less emissions
than burning coal or gas, while burning whole trees produces far
higher emissions than burning fossil fuels.
But if the government was hoping to bring some
harmony to the debate, it seems to have failed. Friends of the
Earth says the calculator provides further evidence that burning
biomass can be dirtier than coal, and that it
"changes everything" when it comes to
thinking about the future of biomass in the UK's energy mix. It
argues the calculator should be used to exclude high polluting
forms of biomass from renewable energy subsidies.
But the Renewable Energy Association's Back
Biomass campaign says the calculator is still in the
development phase and it expects "fundamental revisions" before the
final version is released. A spokesperson tells us:
"Far from 'changing everything',
Friends of the Earth is once again using data that doesn't reflect
the real world of biomass supply chains and forestry governed by
strict Sustainability Criteria."
So the argument looks set to rumble on until it is
clear how the final version of the calculator and the scenarios it
envisages fit into the government's bioenergy strategy. That
probably won't be any time soon.
If the government can guarantee residues will be used
- not whole trees - then biomass generation will presumably help it
achieve climate goals. But the research does highlight that
sometimes calculating emissions can be much more complicated than
it first seems.