Consistent quantification of climate impacts due to biogenic carbon storage across a range of bio-product systems

Abstract

Temporary and permanent carbon storage from biogenic sources is seen as a way to mitigate climate change. The aim of this work is to illustrate the need to harmonize the quantification of such mitigation across all possible storage pools in the bio- and anthroposphere. We investigate nine alternative storage cases and a wide array of bio-resource pools: from annual crops, short rotation woody crops, medium rotation temperate forests, and long rotation boreal forests. For each feedstock type and biogenic carbon storage pool, we quantify the carbon cycle climate impact due to the skewed time distribution between emission and sequestration fluxes in the bio- and anthroposphere. Additional consideration of the climate impact from albedo changes in forests is also illustrated for the boreal forest case. When characterizing climate impact with global warming potentials (GWP), we find a large variance in results which is attributed to different combinations of biomass storage and feedstock systems. The storage of biogenic carbon in any storage pool does not always confer climate benefits: even when biogenic carbon is stored long-term in durable product pools, the climate outcome may still be undesirable when the carbon is sourced from slow-growing biomass feedstock. For example, when biogenic carbon from Norway Spruce from Norway is stored in furniture with a mean life time of 43years, a climate change impact of 0.08kg CO2eq per kg CO2 stored (100year time horizon (TH)) would result. It was also found that when biogenic carbon is stored in a pool with negligible leakage to the atmosphere, the resulting GWP factor is not necessarily −1 CO2eq per kg CO2 stored. As an example, when biogenic CO2 from Norway Spruce biomass is stored in geological reservoirs with no leakage, we estimate a GWP of −0.56kg CO2eq per kg CO2 stored (100year TH) when albedo effects are also included. The large variance in GWPs across the range of resource and carbon storage options considered indicates that more accurate accounting will require case-specific factors derived following the methodological guidelines provided in this and recent manuscripts.