Anders Hammer Strømman

Life cycle assessment of bioenergy systems: State of the art and future challenges

The use of different input data, functional units, allocation methods, reference systems and other assumptions complicates comparisons of LCA bioenergy studies. In addition, uncertainties and use of specific local factors for indirect effects (like land-use change and N-based soil emissions) may give rise to wide ranges of final results. In order to investigate how these key issues have been addressed so far, this work performs a review of the recent bioenergy LCA literature. The abundance of studies dealing with the different biomass resources, conversion technologies, products and environmental impact categories is summarized and discussed. Afterwards, a qualitative interpretation of the LCA results is depicted, focusing on energy balance, GHG balance and other impact categories. With the exception of a few studies, most LCAs found a significant net reduction in GHG emissions and fossil energy consumption when bioenergy replaces fossil energy.

CO2 emissions from biomass combustion for bioenergy: atmospheric decay and contribution to global warming.

Carbon dioxide (CO2) emissions from biomass combustion are traditionally assumed climate neutral if the bioenergy system is carbon (C) flux neutral, i.e. the CO2 released from biofuel combustion approximately equals the amount of CO2 sequestered in biomass. This convention, widely adopted in life cycle assessment (LCA) studies of bioenergy systems, underestimates the climate impact of bioenergy. Besides CO2 emissions from permanent C losses, CO2 emissions from C flux neutral systems (that is from temporary C losses) also contribute to climate change: before being captured by biomass regrowth, CO2 molecules spend time in the atmosphere and contribute to global warming. In this paper, a method to estimate the climate impact of CO2 emissions from biomass combustion is proposed. Our method uses CO2 impulse response functions (IRF) from C cycle models in the elaboration of atmospheric decay functions for biomass‐derived CO2 emissions. Their contributions to global warming are then quantified with a unit‐based index, the GWPbio. Since this index is expressed as a function of the rotation period of the biomass, our results can be applied to CO2 emissions from combustion of all the different biomass species, from annual row crops to slower growing boreal forest.

Life Cycle Environmental Assessment of Lithium-Ion and Nickel Metal Hydride Batteries for Plug-In Hybrid and Battery Electric Vehicles

This study presents the life cycle assessment (LCA) of three batteries for plug-in hybrid and full performance battery electric vehicles. A transparent life cycle inventory (LCI) was compiled in a component-wise manner for nickel metal hydride (NiMH), nickel cobalt manganese lithium-ion (NCM), and iron phosphate lithium-ion (LFP) batteries. The battery systems were investigated with a functional unit based on energy storage, and environmental impacts were analyzed using midpoint indicators. On a per-storage basis, the NiMH technology was found to have the highest environmental impact, followed by NCM and then LFP, for all categories considered except ozone depletion potential. We found higher life cycle global warming emissions than have been previously reported. Detailed contribution and structural path analyses allowed for the identification of the different processes and value-chains most directly responsible for these emissions. This article contributes a public and detailed inventory, which can be easily be adapted to any powertrain, along with readily usable environmental performance assessments.

Bioenergy and climate change mitigation: an assessment

Bioenergy deployment offers significant potential for climate change mitigation, but also carries considerable risks. In this review, we bring together perspectives of various communities involved in the research and regulation of bioenergy deployment in the context of climate change mitigation: Land‐use and energy experts, land‐use and integrated assessment modelers, human geographers, ecosystem researchers, climate scientists and two different strands of life‐cycle assessment experts. We summarize technological options, outline the state‐of‐the‐art knowledge on various climate effects, provide an update on estimates of technical resource potential and comprehensively identify sustainability effects. Cellulosic feedstocks, increased end‐use efficiency, improved land carbon‐stock management and residue use, and, when fully developed, BECCS appear as the most promising options, depending on development costs, implementation, learning, and risk management. Combined heat and power, efficient biomass cookstoves and small‐scale power generation for rural areas can help to promote energy access and sustainable development, along with reduced emissions. We estimate the sustainable technical potential as up to 100 EJ: high agreement; 100–300 EJ: medium agreement; above 300 EJ: low agreement. Stabilization scenarios indicate that bioenergy may supply from 10 to 245 EJ yr−1 to global primary energy supply by 2050. Models indicate that, if technological and governance preconditions are met, large‐scale deployment (>200 EJ), together with BECCS, could help to keep global warming below 2° degrees of preindustrial levels; but such high deployment of land‐intensive bioenergy feedstocks could also lead to detrimental climate effects, negatively impact ecosystems, biodiversity and livelihoods. The integration of bioenergy systems into agriculture and forest landscapes can improve land and water use efficiency and help address concerns about environmental impacts. We conclude that the high variability in pathways, uncertainties in technological development and ambiguity in political decision render forecasts on deployment levels and climate effects very difficult. However, uncertainty about projections should not preclude pursuing beneficial bioenergy options.

Evaluation of process- and input-output-based life cycle inventory data with regard to truncation and aggregation issues.

Life cycle assessments (LCA) and environmentally extended input-output (EEIO) analyses both strive to account for direct and indirect environmental impacts of goods and services. Different methods have been developed to hybridize these two techniques and minimize the impact of their respective shortcomings on final assessments. These weaknesses, however, have not been extensively studied in a quantitative manner, especially not for complete LCA and EEIO databases. To this end, we jointly analyzed process-based and input-output-based data sets. We first evaluated their complementarity. Though the LCA data was more detailed overall, some sectors of the economy were more precisely represented in the EEIO database. We then contrasted the representation of the different economic sectors in the LCA database with the economic, environmental, and structural importance of these sectors. The weakness of the correlation results led us to conclude that process-inventory efforts have not been systematically directed at the most important sectors of the economy. The LCA data was also used to evaluate the sensitivity of EEIO data to aggregation uncertainty. This sensitivity proved highly inhomogeneous. We conclude the presence of important research inefficiencies stemming from the lack of hybrid perspective in the compilation of LCA and EEIO data.

Site-specific global warming potentials of biogenic CO2 for bioenergy: contributions from carbon fluxes and albedo dynamics

Production of biomass for bioenergy can alter biogeochemical and biogeophysical mechanisms, thus affecting local and global climate. Recent scientific developments have mainly embraced impacts from land use changes resulting from area-expanded biomass production, with several extensive insights available. Comparably less attention, however, has been given to the assessment of direct land surface‐atmosphere climate impacts of bioenergy systems under rotation such as in plantations and forested ecosystems, whereby land use disturbances are only temporary. Here, following IPCC climate metrics, we assess bioenergy systems in light of two important dynamic land use climate factors, namely, the perturbation in atmospheric carbon dioxide.CO2/ concentration caused by the timing of biogenic CO2 fluxes, and temporary perturbations to surface reflectivity (albedo). Existing radiative forcing-based metrics can be adapted to include such dynamic mechanisms, but high spatial and temporal modeling resolution is required. Results show the importance of specifically addressing the climate forcings from biogenic CO2 fluxes and changes in albedo, especially when biomass is sourced from forested areas affected by seasonal snow cover. The climate performance of bioenergy systems is highly dependent on biomass species, local climate variables, time horizons, and the climate metric considered. Bioenergy climate impact studies and accounting mechanisms should rapidly adapt to cover both biogeochemical and biogeophysical impacts, so that policy makers can rely on scientifically robust analyses and promote the most effective global climate mitigation options.

Life Cycle Assessment of a Lithium‐Ion Battery Vehicle Pack

Electric vehicles (EVs) have no tailpipe emissions, but the production of their batteries leads to environmental burdens. In order to avoid problem shifting, a life cycle perspective should be applied in the environmental assessment of traction batteries. The aim of this study was to provide a transparent inventory for a lithium‐ion nickel‐cobalt‐manganese traction battery based on primary data and to report its cradle‐to‐gate impacts. The study was carried out as a process‐based attributional life cycle assessment. The environmental impacts were analyzed using midpoint indicators. The global warming potential of the 26.6 kilowatt‐hour (kWh), 253‐kilogram battery pack was found to be 4.6 tonnes of carbon dioxide equivalents. Regardless of impact category, the production impacts of the battery were caused mainly by the production chains of battery cell manufacture, positive electrode paste, and negative current collector. The robustness of the study was tested through sensitivity analysis, and results were compared with preceding studies. Sensitivity analysis indicated that the most effective approach to reducing climate change emissions would be to produce the battery cells with electricity from a cleaner energy mix. On a per‐kWh basis, cradle‐to‐gate greenhouse gas emissions of the battery were within the range of those reported in preceding studies. Contribution and structural path analysis allowed for identification of the most impact‐intensive processes and value chains. This article provides an inventory based mainly on primary data, which can easily be adapted to subsequent EV studies, and offers an improved understanding of environmental burdens pertaining to lithium‐ion traction batteries.

Environmental Impact and Added Value in Forestry Operations in Norway

The forestry sector is experiencing an increasing demand for documentation about its environmental performance. Previous studies have revealed large differences in environmental impact caused by forestry operations, mainly due to differences in location and forestry practice. Reliable information on environmental performance for forestry operations in different regions is thus important. This article presents a case study of forestry operations in Norway. Environmental impact and value added of selected operations were assessed. This was done with a hybrid life cycle assessment (LCA) approach. Main results, including a sensitivity analysis, are presented for a set of four impact categories. The production chain assessed included all processes from seedling production to the delivery of logs to a downstream user. The environmental impact was mainly caused by logging, transport by forwarders, and transport by truck. These three operations were responsible for approximately 85% of the total environmental impact. The contribution to value added and total costs were more evenly distributed among the processes in the value chain. The sensitivity analysis revealed that the difference in environmental impact between the worst case scenario and the best case scenario was more than a factor of 4. The single most important process was the transport distance from the timber pile in the forest to the downstream user. The results show that the environmental impact from forestry operations in boreal forests was probably underreported in earlier studies.

Life Cycle Assessment of Second Generation Bioethanols Produced From Scandinavian Boreal Forest Resources A Regional Analysis for Middle Norway

The boreal forests of Scandinavia offer a considerable resource base, and use of the resource for the production of less carbon-intensive alternative transport fuel is one strategy being considered in Norway. Here, we quantify the resource potential and investigate the environmental implications of wood-based transportation relative to a fossil reference system for a specific region in Norway. We apply a well-to-wheel life cycle assessment to evaluate four E85 production system designs based on two distinct wood-to-ethanol conversion technologies. We form best and worst case scenarios to assess the sensitivity of impact results through the adjustment of key parameters, such as biomass-to-ethanol conversion efficiency and upstream biomass transport distance. Depending on the system design, global warming emission reductions of 46% to 68% per-MJ-gasoline avoided can be realized in the region, along with reductions in most of the other environmental impact categories considered. We find that the regions surplus forest-bioenergy resources are vast; use for the production of bioethanol today would have resulted in the displacement of 55% to 68% of the regions gasoline-based global warming emissionor 6% to 8% of Norways total global warming emissions associated with road transportation.

Life-cycle Assessment of Carbon Dioxide Capture for Enhanced Oil Recovery

Abstract The development and deployment of Carbon dioxide Capture and Storage (CCS) technology is a cornerstone of the Norwegian governments climate strategy. A number of projects are currently evaluated/planned along the Norwegian West Coast, one at Tjeldbergodden. CO 2 from this project will be utilized in part for enhanced oil recovery in the Halten oil field, in the Norwegian Sea. We study a potential design of such a system. A combined cycle power plant with a gross power output of 832 MW is combined with CO 2 capture plant based on a post-combustion capture using amines as a solvent. The captured CO 2 is used for enhanced oil recovery (EOR). We employ a hybrid life-cycle assessment (LCA) method to assess the environmental impacts of the system. The study focuses on the modifications and operations of the platform during EOR. We allocate the impacts connected to the capture of CO 2 to electricity production, and the impacts connected to the transport and storage of CO 2 to the oil produced. Our study shows a substantial reduction of the greenhouse gas emissions from power production by 80% to 75 g·(kW·h) −1 . It also indicates a reduction of the emissions associated with oil production per unit oil produced, mostly due to the increased oil production. Reductions are especially significant if the additional power demand due to EOR leads to power supply from the land.