Climate Change Effects of Biomass and Bioenergy Systems

Copenhagen Statement

“Forests, bioenergy and climate change mitigation”

 This statement is an outcome of the workshop on “Forests, bioenergy and climate change mitigation”, held May 19-20, 2014 in Copenhagen[1] , which had the following objectives:

  • to facilitate dialogue between scientists on the topic of climate effects of forest -based bioenergy,  in order to advance scientific understanding of the topic and to clarify divergent views on the role of forest-based bioenergy in climate change mitigation, and
  • to identify knowledge gaps and priorities for future research and data collection, in order to improve scientific understanding and support policy development for forest-based bioenergy.

1    Framing the Issue

Concerns regarding global climate change led to the adoption of the long-term target to limit global warming to 2°C. Current scientific understanding indicates that peak warming is insensitive to CO2 emission trajectories [3] ; that is, timing of emissions is not critical in relation to the 2°C target. On the other hand, policymakers may judge that additional climate targets are needed to facilitate climate change mitigation, such as short-term national emission reduction targets. Such targets constrain the possible emission trajectory profile and shift focus toward gases with shorter atmospheric lifetimes; thus timing of GHG emissions is relevant for such policy targets.

As noted in the IPCC AR5 report “..scenarios reaching atmospheric concentration levels of about 450 ppm CO2eq by 2100 (consistent with a likely chance to keep temperature change below 2 °C relative to pre-industrial levels) include substantial cuts in anthropogenic GHG emissions by mid-century through large-scale changes in energy systems … [and that] bioenergy can play a critical role for mitigation, but there are issues to consider, such as the sustainability of practices and the efficiency of bioenergy systems”. It is further noted that: “the scientific debate about the overall climate impact related to land-use competition effects of specific bioenergy pathways remains unresolved[4] .  Fossil fuel use transfers carbon from the slow domain of the carbon cycle, where turnover times exceed 10,000 years, to the fast domain (the atmosphere, ocean, vegetation and soil); bioenergy systems operate within the fast domain, where vegetation and soil carbon have turnover times of 1-100 and 10-500 years, respectively [5] . A reduction of deforestation and more efficient use of forest biomass for wood-based products and energy, maximising GHG mitigation per unit biomass, are needed in parallel.

Policies frame markets for bioenergy and the broader bioeconomy, and forest management will react to that, as well as forest product markets. Forest management often has a long-term focus, which presents a challenge for development of policies intending to support near-term climate targets.

Forest management influences the dynamics of forest carbon stocks. In many countries, forest carbon stocks have increased over recent decades, but deforestation has reduced carbon stocks in other regions (sub-Saharan Africa, Latin America, South-East Asia). Currently, the vast majority of forest managers receive no revenue from maintaining or increasing forest C stocks.Forest governance differs between countries and regions, which is relevant when considering the implications of the increasing trade in bioenergy.


2    Modelling: scope, data and limitations

2.1    Treatment Of Bioenergy Under The UNFCCC And In Life Cycle Assessment (LCA)

The estimation of carbon fluxes from forest bioenergy in national inventories under the United Nations Framework Convention on Climate Change (UNFCCC) follows IPCC guidelines for national GHG reporting. This means that annual forest carbon releases or sinks are allocated to the land use, land use change and forestry (LULUCF) sector, and CO2 emissions from biomass use are excluded [6] in the energy sector to avoid double counting. This is different from GHG accounting in life cycle assessment (LCA), which has a cross-sectoral and cross-border view and sums GHG emissions over the life cycle of a specific product or service to which the impact of those emissions is attributed.

Both approaches ask different questions, and different actors apply them with different scopes. When IPCC “tier 1” data [7] are used in LCA studies  to obtain estimates of biomass and soil carbon fluxes, caution and transparency are needed as these data were intended for national level reporting and may not be appropriate at finer scales.

Various metrics have been proposed for quantifying climate change effects. Depending on the purpose of the assessment, different metrics may be preferred. Global Warming Potential (GWP) [8] is the most commonly used metric but, the Global Temperature Change Potential (GTP) may be a more appropriate metric in some circumstances.  Application of more than one metric is informative for policy development.

2.2   Modelling And LCA Approaches For Assessing Forest Bioenergy

Information and knowledge from many scientific disciplines, applying a range of different methodologies, are needed to guide development of policy for forest bioenergy. For policy assessment, a landscape [9] perspective, rather than the forest stand level, would in general be the appropriate scope. In any case, the geographical scale, and time scale, should reflect the aim of the assessment or the scope of the (policy) instrument to be evaluated.

The workshop participants agreed that a combination of biophysical, climate and socio-economic models is required to understand the climate effects of bioenergy, including effects on parallel industries (wood products, agriculture and energy), and to inform policy development. The earth climate system is altered not only by CO2, but also by changes in the atmospheric concentration of other gases and aerosols (directly emitted or precursors), in solar radiation and in land surface albedo. Therefore, the effects of all climate forcers influenced by forest cover and forest management should ideally be included. In addition, impacts on biodiversity and ecosystem services need to be considered in policy development.

While attributional LCA (ALCA) may be applicable for some purposes (such as identifying hotspots in the supply chain or implementing a policy decision, as it reflects those aspects under control of the project manager or economic operator), it is not appropriate for evaluating the consequences of the introduction of a new policy, because it does not consider effects on other sectors of the economy. Therefore, consequential approaches, such as consequential LCA (CLCA) are required in developing policy, to conduct due diligence of new policy alternatives. One significant drawback of CLCA is the inevitable uncertainty associated with modelling complex systems, so analysts, stakeholders and policy makers need to exercise appropriate caution and be transparent about the uncertainty associated with CLCA estimates, and pragmatic in choosing among policy alternatives that have high degrees of uncertainty.

Consequential comparative assessments addressing forest bioenergy policies need to compare the biomass and soil carbon pools, product pools, etc. in the bioenergy policy scenarios with counterfactual scenarios. Because the future is uncertain, for both the reference “business as usual” (BAU) situation and the “with bioenergy” case, it is preferable to model several scenarios to inform policy-making. BAU scenarios should reflect commonly accepted practice in forest management and land use, anticipated trends in both, and include different developments in forest product markets (sawnwood and pulpwood markets, new biobased materials) and also energy markets.


3    Policy Guidance

Decisions by government and the private sector should be informed by scientific understanding of climate change impacts of forest bioenergy. Such input should be based on comprehensive analysis of complex systems in the context of alternative policy options and energy technology pathways.

Decision-makers are looking for near-term policy solutions while more sound scientific assessments are being developed.  Given the complex nature of the issue, some have questioned whether decision makers should use categories of bioenergy feedstock production systems based on simplified system descriptions (e.g. sustainable forest management plus maintaining forest carbon stock) to identify acceptable bioenergy systems to support and implement.

Such approaches (including “go/no-go” lists) must be seen as very crude first-order estimates and are subject to significant uncertainty, and so caution should be used if such proxies are applied. It was agreed that risk-based approaches are preferable. For example:

  • Multidimensional risk matrices covering spatial aspects, forest management, forest product types, downstream/upstream markets effects and energy substitution could be used to assess specific cases.
  • Consequential modelling approaches should be applied for policy development, and large-scale projects as part of due diligence. Such planning processes require transparency, including stakeholder involvement.
  • Methodological frameworks (guidance and rules) for risk-based approaches should be developed.


4    Research Needs

The scientific base to inform decision-makers should be expanded beyond LCA, considering the role of integrated models, global monitoring systems and publicly available databases.

The following specific research needs were identified:

  • studies clarifying how the energy sector, forest industry and forest management planning respond to changing forest product markets, including bioenergy markets;
  • good empirical data on forest product supply and demand and land use, at scales of resolution that enable comprehensive analyses of alternative scenarios;
  • development of stronger links between the forest/bioenergy systems modelling and the earth systems/ climate science/ integrated assessment modelling efforts;
  • multi-disciplinary research into the interpretation and translation of insights from scenario modelling into policy guidance for management of land use and energy systems.

As bioenergy policy is currently being developed, for example in Belgium, Denmark, the Netherlands, the UK and the USA at national and state levels, the international community (including scientists and policy-makers from government and industry) should prioritise allocation of resources to conduct the necessary research and risk-analyses that would lead to deployment of sustainable bioenergy systems.

Developed by the workshop participants
Copenhagen, May 20, 2014
Edited for clarity by the Organizing Committee, August 2014

Copenhagen workshop report