Implications of system expansion for the assessment of well-to-wheel CO2 emissions from biomass-based transportation

Abstract

SUMMARYIn this paper we show the effects of expanding the system when evaluating well-to-wheel (WTW) CO 2 emissions for biomass-based transportation, to include the systems surrounding the biomass conversion system. Four different cases are considered: DME via black liquor gasification (BLG), methanol via gasification of solid biomass, lignocellulosic ethanol and electricity from a biomass integrated gasification combined cycle (BIGCC) used in a battery-powered electric vehicle (BPEV). All four cases are considered with as well as without carbon capture and storage (CCS). System expansion is used consistently for all flows. The results are compared with results from a conventional WTW study that only uses system expansion for certain co-product flows.It is shown that when expanding the system, biomass-based transportation does not necessarily contribute to decreased CO 2 emissions and the results from this study in general indicate considerably lower CO 2 mitigation potential than do the results from the conventional study used for comparison. It is shown that of particular importance are assumptions regarding future biomass use, as by expanding the system, future competition for biomass feedstock can be taken into account by assuming an alternative biomass usage. Assumptions regarding other surrounding systems, such as the transportation and the electricity systems are also shown to be of significance.Of the four studied cases without CCS, BIGCC with the electricity used in a BPEV is the only case that consistently shows a potential for CO 2 reduction when alternative use of biomass is considered. Inclusion of CCS is not a guarantee for achieving CO 2 reduction, and in general the system effects are equivalent or larger than the effects of CCS. DME from BLG generally shows the highest CO 2 emission reduction potential for the biofuel cases. However, neither of these options for biomass-based transportation can alone meet the needs of the transport sector. Therefore, a broader palette of solutions, including different production routes, different fuels and possibly also CCS, will be needed.

Systems analysis of integrating biomass gasification with pulp and paper production – Effects on economic performance, CO2 emissions and energy use

“…Harvey [11] and Wetterlund et al [20]. It is assumed that the net ows of energy and material entering or Figure 3: Overview of the studied BIGCC biorenery.…”

“…Similarly, it is assumed that district heating delivered from the gasication plants in the stand-alone cases replaces alternative district heating production and that DME replaces diesel in heavy trucks. The supply of biomass is regarded as limited, thus additional demand for biomass at the biorenery plant site will lead to increased use of fossil fuels elsewhere in the expanded system, as discussed in reference [20]. The marginal CO 2 eects of increased biomass use are taken into account by assuming an alternative biomass usage.…”

“…If the CO 2 emission eect would instead be shown per unit of biomass input, as discussed in eg. [20], the BIGDME cases would for example lose some of their apparent advantage. Those results thus emphasise the importance of considering marginal biomass use eects.…”

Sociotechnical system studies of the reduction of greenhouse gas emissions from energy and transport systems

“…The figures derived from such analyses can be used in subsequent evaluations or as a basis for decision-making. Research has shown that the results of GHG-emission assessments differ, depending on which methods are used and which assumptions about input data are made (e.g., Borrion et al, 2012;Börjesson, 2009;Sjödin and Grönkvist, 2004;Wetterlund et al, 2010). Thus, these results can be difficult to use as they are products of their context.…”

“…Table 3 presents the renewable energy carriers that were selected and their main production pathway and use. Research has shown that the use of biofuels such as those listed in Table 3 could reduce GHG emissions from transport (see for example Difs et al, 2010;Mohseni et al, 2012;Wetterlund et al, 2010). Great potential has also been identified in the amount of renewable energy that could be used in the transport sector.…”