The Institute for European Environmental Policy (IEEP) has reviewed current thinking about the life cycle analysis conventions for bioenergy (and woody biomass in particular) and found that the routinely used metrics are “increasingly recognised as flawed”. “This applies particularly to commonly used approaches to life cycle analysis that presume carbon neutrality of the bioenergy feedstock,” the Institute says.
Without a better system for evaluating the greenhouse gas impacts of our policies, they conclude, we cannot know if (or when) our bioenergy use might actually cut greenhouse gas emissions.
The review, The GHG Emissions Intensity of Bioenergy (56pp pdf) was published in October 2012.
The authors reviewed a wide range of recent papers on the subject of the greenhouse gas balance of biomass burning, and found that far from being generally accepted that bioenergy is ‘carbon neutral’ there was now “a general appreciation that increasing the intensity of forestry management and increasing biomass extraction rates over time will lead to a carbon deficit.”
“This then needs to be ‘repaid’ before the exploitation of bioenergy from such resources can deliver emission savings compared to burning fossil fuels,” they say. For example, a paper published in 2011 by McKechnie and colleagues calculated that even over 100 years, and even eschewing whole trees and only burning residues, biomass energy only delivered 73 per cent of the savings anticipated in conventional assumptions (as used by the EU and UK government).
According to this and many other analyses, if whole trees are burned, if a different (lower carbon) energy source is displaced, or if the focus is on a shorter timescale, these presumed savings are eroded still further, and may indeed be eliminated, IEEP warn. (The McKechnie paper was cited by the UK Committee on Climate Change in its 2011 Bioenergy Review.)
IEEP warn that to begin with, when biomass is burned “there is an excess of GHG emissions from the burning of a source of bioenergy over that from the fossil fuel reference energy source.” They also point out that the eventual savings are usually predicated on the source of the biomass being left to return to its pre-harvest state, whereas “in reality, successive episodes of bioenery exploitation may well occur, and keep creating a GHG emission debt.” In other words, we’re not talking about a discrete bioenergy harvesting event, but a new mode of intensified extraction, to feed a new industry.
The report also echoes the concern highlighted in the report for DECC by Forest Research and North Energy Associates (Carbon impacts of using bioenergy in energy and other sectors: forests) that burning biomass might not be the best way to use it to reduce carbon emissions, if that same biomass is being diverted from manufacturing, which then turns to higher-carbon substitutes such as steel, concrete or plastic.
IEEP conclude that we urgently need new ways to evaluate the best way to use land and biomass products to reduce carbon emissions – that have a stonger basis in the evidence. “Utilisation for energy represents only one potential use of diverse biomass materials within society … in a variety of situations other uses will be prefereable purely in terms of climate impact … irrespective of other considerations.”
“Policies based on misleading LCAs need to be revisited and revised as appropriate,” and “the evidence base for making informed decisions about bioenergy in relation to climate change needs to be strengthened considerably as a matter of urgency.”
They end: “It is not currently possible to define the emissions profile and savings associated with Europe’s expanding use of biomass for energy, nor is there any policy process currently in place to secure this. As a consequence, at present there is only the certainty of commitment to bioenergy use up to 2020, but no associated guarantee of emission reduction.”