Back to the future: dynamic full carbon accounting applied to prospective bioenergy scenarios

Abstract

Ongoing debates focus on the role of forest-sourced bioenergy within climate mitigation efforts, due to the long rotation lengths of forest biomass. Valuing sequestration is debated due to its reversibility; however, dynamic modelling of biogenic carbon (Cbio) flows captures both negative and positive emissions. The objective of this work is to respond to the key issue of timing sequestration associated with two opposed modelling choices (historic vs. future) in the context of dynamic LCA.Methods. The model outputs of a partial-equilibrium model are used to inform prospective evaluations of the use of forest wood residues in response to an energy transition policy. Dynamic forest carbon modelling represents the carbon cycle between the atmosphere and technosphere: Cbio fixation and release through combustion and/or decay. Time-dependent characterisation is used to assess the time-sensitive climate change effects. The two Cbio sequestration perspectives for bioenergy (biomass use) and reference (no use) scenarios are contrasted to assess i) their temporal profiles, ii) their climatic consequences concerning C-complete (fossil + biogenic C) vs Cneutral (fossil C) approaches, and iii) the implications of comparing the two approaches with dynamic LCA.Results and discussion. Full lifetime carbon accounting confirms that Cbio entering the bioenergy system equals the Cbio leaving it in a net balance, but not within annual balances, which alter the atmospheric greenhouse gas composition. The impacts of the historic approach differed considerably from those of the future. Moreover, the methane proportions. The chicken-egg dilemma arises in attributional LCA: as the forcing depends on the timing of the Cbio sequestration and its allocation to a harvest activity. A decision tree supported by case study applications provides general rules for selecting the adequate time-related modelling approach based the criteria of provision of wood and regrowth from managed and unmanaged forests, determined by the origin of biotic resources and related spheres. Conclusions.Excluding dynamic Cbio introduces under-(future) or over-(historic) estimation of the results, misleading mitigation results. Further research is needed to close the gap between forest stand and landscape level, addressing issues beyond the chicken-egg dilemma, and developing complete dynamic LCA studies.

Life cycle assessment of carbon dioxide removal technologies: a critical review

“…In addition, CO 2 storage in forests can be reversible, since its permanency depends on many factors and potential disturbances such as wildfires, water scarcity, storms, flooding and pests infestation. 40,[44][45][46][47][48] Further, direct and indirect land use change (i.e. LUC and iLUC) can also greatly influence the GHG emission balance (please refer to Section 1.2 in the ESI, † for more explanation).…”

Bioenergy carbon emissions footprint considering the biogenic carbon and secondary effects

“…Levasseur et al 23 assessed the CF of a wooden chair with a different end of life scenarios by dynamic LCA. Albers et al 24 applied dynamic LCA in carbon accounting of bioenergy and concluded the potential misleading mitigation decision by excluding dynamic biogenic carbon. The advantages and limitations of these two approaches (GWP bio , Dynamic LCA) have been critically discussed by Breton et al, 10 specifically for buildings.…”

No simple menu for sustainable food production and consumption

“…The importance of using dynamic LCA in GHG accounting was also studied by Albers et al (2019) who looked at dynamic full carbon accounting for evaluating prospective bioenergy scenarios. GHG reduction options often focus on the use of biogenic carbon sources for energy to displace fossil-based carbon dioxide emissions.…”

“…Also, the effect of modeling the biomass growth (forest) before harvest or after harvest is different. So Albers et al (2019) studied the difference in results of modeling choices (before harvest/historic vs. after harvest/future) on the carbon sequestration in forestry for bioenergy vis-à-vis the greenhouse gas balance using a dynamic LCA approach. A partial equilibrium model was used combining prospective energy system analysis with biogenic carbon modeling to assess the time-sensitive climate consequences of an energy policy scenario with fossil and biogenic carbon accounting.…”