Carbon balance indicator for forest bioenergy scenarios

Kim Pingoud, Tommi Ekholm, Sampo Soimakallio, Tuomas Helin

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19 Citations (Scopus)

Abstract

A carbon (C) balance indicator is presented for the evaluation of forest bioenergy scenarios as a means to reduce greenhouse gas (GHG) emissions. A bioenergy-intensive scenario with a greater harvest is compared to a baseline scenario. The relative carbon indicator (RC) is defined as the ratio between the difference in terrestrial C stocks - i.e. the C debt - and the difference in cumulative bioenergy harvest between the scenarios, over a selected timeframe T. A value of zero indicates no C debt from additional biomass harvests, while a value of one indicates a C debt equal to the amount of additionally harvested biomass C. Multiplying the RC indicator by the smokestack emission factor of biomass (approximately 110 t CO2/TJ) provides the net cumulative CO2 emission factor of the biomass combustion as a function of T, allowing a direct comparison with the emission factors of comparable fossil fuels. Using the data of Asikainen et al. (2012), Sievänen et al. (2014) and Repo et al. (2012), the indicator is applied to bioenergy cases in Finland, where typically the rotation length of managed forests is long and the decay rate of harvest residues is slow. The country-level examples illustrate that although Finnish forests remain as a C sink in each of the scenarios considered, the efforts of increasing forest bioenergy may still increase the atmospheric CO2 concentrations in comparison with the baseline scenario and use of fossil fuels. The results also show that the net emission factor depends - besides on forest-growth or residue-decay dynamics - on the timing and evolution of harvests as well. Unlike for the constant fossil C emission factor, the temporal profile of bioenergy use is of great importance for the net emission factor of biomass.
Original languageEnglish
Pages (from-to)171-182
JournalGlobal Change Biology: Bioenergy
Volume8
Issue number1
DOIs
Publication statusPublished - 2016
MoE publication typeA1 Journal article-refereed

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Keywords

  • biomass emission factor
  • carbon debt
  • forest harvest residues
  • dynamics
  • steady-state
  • carbon neutrality
  • landscape level
  • baseline
  • system boundaries
  • timing of emissions

Cite this

Pingoud, K., Ekholm, T., Soimakallio, S., & Helin, T. (2016). Carbon balance indicator for forest bioenergy scenarios. Global Change Biology: Bioenergy, 8(1), 171-182. https://doi.org/10.1111/gcbb.12253