IEA Bioenergy paper gets to grips with scientific literature on the climate effects of forest bioenergy

The scientific literature contains contrasting findings on the climate effects of forest bioenergy. This is partly due to the wide diversity of bioenergy systems but also due to differences in assessment methods.

In a recently published paper titled “Applying a science- based systems perspective to dispel misconceptions about climate effects of forest bioenergy“, the IEA Bioenergy Technology Collaboration Programme (IEA Bioenergy TCP) examines debated aspects related to climate impacts of forest bioenergy, in applications including heat production, power generation and transport.

IEA生物能源研究TCP是一个全球性的网络and implementation of bioenergy, established under the International Energy Agency’s Implementing Agreement mechanism. The paper, which has been published as an open-access article in the journalGCB Bioenergy, is an output of IEA Bioenergy Task 45 ‘Climate and Sustainability Effects of Bioenergy within the broader Bioeconomy’ with twenty-eight scientists from around the world with expertise in forestry, climate, and energy systems that contributed to this article.

The paper identifies factors that are relevant to understanding the climate effects of forest bioenergy and misconceptions that can lead to conclusions that exaggerate or underestimate the effects. The objective is to reduce confusion arising from the publication of diverging studies on forest bioenergy, to inform policy development, business decisions and the public debate on bioenergy.

Temporal and spatial system boundaries and counterfactual scenario choices influence results

The temporal and spatial system boundary and the reference (known as “counterfactual”) scenarios are key methodology choices that strongly influence the results of studies on the climate effects of forest bioenergy. Focussing on carbon balances of individual forest stands and comparing emissions at the point of combustion neglect system-level interactions that influence the climate effects of forest bioenergy.

A systems approach should be used, that considers the whole life cycle of bioenergy systems, including effects on land carbon balances, production of wood products, and impacts on sectors affected by bioenergy deployment, including transport, building, and energy.

Greenhouse gas (GHG) reporting under the United Nations Framework Convention on Climate Change (UNFCCC) does not assume that bioenergy is carbon neutral, as any carbon stock loss associated with forest harvest is counted as a CO2 emission in the land use, land-use change, and forestry sector (LULUCF).

Proposals to count emissions at the point of combustion could have adverse climate impacts as this creates disincentives to replace fossil fuel, and removes incentives for maintaining forest carbon stocks.

Nevertheless, greater transparency and consistency are needed in GHG reporting and accounting related to bioenergy so that the connections between forest carbon stock change and the use of biomass for energy are not overlooked.

Key conclusions of the paper are:

• The use of sustainable forest biomass for energy (heat, electricity, or transport fuels) can effectively reduce fossil fuel use in the short term and can contribute to phasing out the use of fossil fuels in technologies and infrastructure that rely on carbon-based fuels. Furthermore, when combined with carbon capture and storage (CCS), forest bioenergy can remove CO2 from the atmosphere.
• Effective sustainability governance is required to ensure that forest biomass used for energy makes a positive contribution to mitigating climate change, and to broader environmental and socioeconomic objectives.
• Holistic assessments show that forests managed according to sustainable forest management principles and practices can contribute to climate change mitigation by providing bioenergy and other forest products that replace GHG-intensive materials and fossil fuels, and by storing carbon in the forest and in long-lived forest products.
• Bioenergy systems operate within the biogenic carbon cycle, which implies a fundamentally different influence on atmospheric CO2 concentrations over time compared to burning fossil fuel, which transfers carbon from geological storage and causes a permanent increase in atmospheric CO2.
• To answer the key question ‘what are the climate implications of policies that promote bioenergy?’ assessment should be made at the landscape level, and use a full life cycle approach that includes supply chain emissions, changes in land carbon stocks, and other variables influenced by the policies studied.
• The bioenergy system should be compared with reference scenarios (counterfactuals) that describe the most likely alternative land use(s) and energy sources that would be displaced by the bioenergy system, and the probable alternative fates for the biomass being utilized.