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 language | English |
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Pages (from-to) | 171-182 |
Journal | Global Change Biology: Bioenergy |
Volume | 8 |
Issue number | 1 |
DOIs | |
Publication status | Published - 2016 |
MoE publication type | A1 Journal article-refereed |
Keywords
- biomass emission factor
- carbon debt
- forest harvest residues
- dynamics
- steady-state
- carbon neutrality
- landscape level
- baseline
- system boundaries
- timing of emissions