Carbon balances of bioenergy systems using biomass from forests managed with long rotations: bridging the gap between stand and landscape assessments

Abstract

Studies report different findings concerning the climate benefits of bioenergy, in part due to varying scope and use of different approaches to define spatial and temporal system boundaries. We quantify carbon balances for bioenergy systems that use biomass from forests managed with long rotations, employing different approaches and boundary conditions. Two approaches to represent landscapes and quantify their carbon balances -expanding vs. constant spatial boundaries -are compared. We show that for a conceptual forest landscape, constructed by combining a series of time-shifted forest stands, the two approaches sometimes yield different results. We argue that the approach that uses constant spatial boundaries is preferable because it captures all carbon flows in the landscape throughout the accounting period. The approach that uses expanding system boundaries fails to accurately describe the carbon fluxes in the landscape due to incomplete coverage of carbon flows and influence of the stand-level dynamics, which in turn arise from the way temporal system boundaries are defined on the stand level. Modelling of profit-driven forest management using location-specific forest data shows that the implications for carbon balance of management changes across the landscape (which are partly neglected when expanding system boundaries are used) depend on many factors such as forest structure and forest owners' expectations of market development for bioenergy and other wood products. Assessments should not consider forest-based bioenergy in isolation but should ideally consider all forest products and how forest management planning as a whole is affected by bioenergy incentives -and how this in turn affects carbon balances in forest landscapes and forest product pools. Due to uncertainties, we modelled several alternative scenarios for forest products markets. We recommend that future work consider alternative scenarios for other critical factors, such as policy options and energy technology pathways.

Geospatial supply–demand modeling of biomass residues for co‐firing in European coal power plants

“…See Berndes, Ahlgren, Börjesson, and Cowie (); Cintas et al. (, ) for further reading on this topic.…”

Accounting for effects of carbon flows in LCA of biomass-based products—exploration and evaluation of a selection of existing methods

“…Holtsmark (2012) and Cintas et al (2017)). Similar to the already used GWP characterization factors (IPCC 2013), the GWP bio CF represents the cumulative radiative forcing of a greenhouse gas relative to the forcing of a pulse of CO 2 and thus also is a relative measure of the potential effects of that greenhouse gas on the climate.…”

“…Recently, Cintas et al (2017) demonstrated that the results of assessment at the landscape level depend on how the spatial system boundaries are defined, that is, whether these boundaries are constant or are expanding during an accounting period. Cintas et al (2017) argue that using constant spatial boundaries is preferred because in that case all carbon flows in a landscape are accounted for and thus is a true landscape approach.…”

“…Cintas et al (2017) argue that using constant spatial boundaries is preferred because in that case all carbon flows in a landscape are accounted for and thus is a true landscape approach. This is contrary to Cherubini et al (2013) (see (2) above) who assume that the spatial system boundaries expand during the accounting period (by offsetting the carbon emissions of a newly harvested plot) and thus account for all carbon flows in the landscape only at the end of an accounting period when all stands that comprise the landscape are included in the assessment.…”

Natural climate solutions versus bioenergy: Can carbon benefits of natural succession compete with bioenergy from short rotation coppice?

“…Yet, concerns regarding the net carbon (C) impacts of increased forest harvests are rising. Due to the reduction in forest C stocks associated with increased use of forest biomass relative to a counterfactual scenario with lower harvests, it often takes considerable periods of time until forest bioenergy actually provides net C savings in comparison to fossil‐based reference systems (“fossil fuel parity time,” see Cherubini, Bright, & Strømman, ; Cintas et al, ; Gustavsson, Haus, Ortiz, Sathre, & Truong, , ; Holtsmark, ; Hudiburg, Law, Wirth, & Luyssaert, ; Jonker, Junginger, & Faaij, ; Lamers & Junginger, ; McKechnie, Colombo, Chen, Mabee, & MacLean, ; Sterman, Siegel, & Rooney‐Varga, ; Vanhala, Repo, & Liski, ; Zanchi, Pena, & Bird, , ). Depending on different influencing factors (management practices, tree species, types of fossil fuels being displaced, which parts of trees are used for energy and other uses, etc.…”