Bioenergy is generally considered to be carbon-neutral. It can be used as replacement for fossil fuels and, therefore, as a way of mitigating climate change. The idea of bioenergy being carbon-neutral is based on the assumption that the carbon dioxide released by the combustion of biomass is bound again into the growing biomass. Based on the regeneration rate of biomass, this may well be the case. However, based on this fact alone, we cannot draw conclusions whether bioenergy is an efficient measure for climate change mitigation or nor.
Often conflicting quantification results of the climate effects of bioenergy make decision-making difficult and cause financial risks. At VTT and the Finnish Environment Institute (SYKE), we have been involved in international cooperation to study how the quantification practices could be made consistent. Our study, to be published in the Renewable & Sustainable Energy Reviews journal, clarifies what bioenergy production should be compared with when quantifying climate effects and what kind of conclusions can be drawn from the carbon balances defined in various ways.
The EU is currently considering how to involve the land use sector in the post-2020 climate commitments and what kind of sustainability criteria to apply to bioenergy. These decisions may also affect each other. The same issues also arise in connection with the Paris Agreement on Climate Change.
Those bioenergy sources that can most efficiently respond to the mitigation targets for climate change will also be the most competitive ones. Therefore, it is important to identify the climate effects of bioenergy. The same also applies to the other products of the bioeconomy.
Inconsistencies lead to conflicting results and interpretations
When quantifying the climate effects of bioenergy, the particularly important question to ask is how the production of bioenergy is supposed to affect land use and, consequently, the development of carbon stocks.
In the quantifications of climate effects of bioenergy, some very conflicting results and interpretations have been produced, when different reference systems of land use have been used or the reference land use has been excluded in the first place. In addition, the starting points for the various analysis and their impact on the results are not always explained clearly enough. This makes it difficult to draw any consistent conclusions from the results.
To be able to quantify the real capacity of bioenergy to mitigate climate change, we must compare the production of bioenergy to a situation in which it is not produced. In such a case, the challenge lies not only in defining the form of alternative energy, but also in defining the reference system for biomass and the land area needed for producing it.
Systematic selection of the reference system for land use
In reality, the biomass and the land area needed for producing bioenergy always has some alternative fate. We call this alternative fate the “reference system”, meaning the situation which remains unrealised if the decision is made to use the land and biomass resources for bioenergy production. For land use, the reference system can be, for example, the use of the land area for production of different biomaterials, food or feed, construction, or provision of other ecosystem services.
For the purpose of systematic quantification of the climate effects of bioenergy, the reference system for the biomass or the land area needed for producing bioenergy can be selected in such a manner that it describes the most likely alternative use of the resource. The challenge is that, for objectivity’s sake, it may be necessary to draw up several scenarios on which alternative use of the resource would be the most likely. In addition, in such a case, it would also be necessary to define the indirect impacts that are caused when the service displaced, such as food, is produced elsewhere. The quantification may become very complicated and its results are very susceptible to any socio-economic assumptions made.
The indirect impacts related to land use have often been ignored in the quantifications of the climate effects of bioenergy. This means that the most likely alternative use of resources has been ignored. In such a case, the consistent assumption would be that, in the reference system, the biomass or the land area needed for producing bioenergy would not be used for any purpose. Therefore, depending on the research question and the time span suited for examining it, the land area would be either in its natural state or gradually returning towards it. Describing such a reference system entails scientific uncertainty, but no socio-economic uncertainty.
The key conclusion of our study is that the reference system must be selected in accordance with the research question. The selection of the reference system defines what kind of conclusions can be drawn from the analysis. Therefore, the reference system selected and its impact on the results must be clearly explained.
The study is part of the work of the International Energy Agency’s IEA Bioenergy Task 38 investigating the climate effects of bioenergy. The work performed by Finnish research scientists was funded by the Academy of Finland, the Sustainable Bioenergy Solutions for Tomorrow (BEST) research programme, and the Maj and Tor Nessling Foundation.
Koponen, K., Soimakallio, S., Kline, K., Cowie, A., Brandão, M. 2017. Quantifying the climate effects of bioenergy – Choice of reference system. Renewable & Sustainable Energy Reviews (in press). http://authors.elsevier.com/sd/article/S1364032117309759