Technologies based upon biogenic storage of carbon, bio-energy or bio-products have been proposed as mitigators of climate change. Life Cycle Assessment may facilitate the quantification of the environmental impacts and potential climate benefits of these technologies and products. However, significant methodological challenges remain. We discuss these in this session.
Key Discussion Points:
- Determining the climate benefits of biogenic storage of carbon
- Optimizing the contribution of biomass in energy systems
- Understanding the LCAs of energy systems in remote areas
- Using LCA to assist research and development of new products
- Challenges of conducting LCA
|10:30||Geoffrey Guest, Ryan Bright, Francesco Cherubini and Anders Strømman
Consistent quantification of climate impacts due to biogenic carbon storage across a range of bio-product systems
SPEAKER: Geoffrey Guest
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 feed-stock 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 feed-stock 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 43 years, a climate change impact of 0.08 kg CO2eq per kg CO2 stored (100 year 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 −0.56 kg CO2eq per kg CO2 stored (100 year 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.
|10:45||Carl Vadenbo, Davide Tonini, Stefanie Hellweg and Thomas F. Astrup
Optimizing the use of biomass in national energy systems under current capacities and future energy scenarios – the case of Denmark
SPEAKER: Carl Vadenbo
ABSTRACT. Many countries worldwide have committed to increase the share of renewable energy in their energy systems. Besides harvesting wind, solar, hydro, and geothermal energy, the use of biomass is frequently put forward as an important component to meet these targets. Determining sustainable strategies for utilizing domestic biomass resources requires a holistic perspective to reflect the consequences of, for example, limited availability of agricultural land and the associated competition with the food/feed sector, which in turn may induce land use changes. To identify the environmentally-optimal use of biomass in the Danish energy system, an optimization model based on linear programming was formulated. Key model constraints comprise meeting the annual energy demand, divided into a set of final demand categories (electricity, centralized/decentralized district heating, individual heating, process heat, and various transport services), under current or foreseen (2030) plant capacities, and with limited availability of biomass and agricultural land. Primary bioenergy conversion options include pretreatment for liquid/solid separation (e.g. for manure), direct combustion, bioethanol biorefineries, anaerobic digestion, gasification, and pyrolysis. Options for subsequent utilization include direct use in combined-heat-and-power units or upgrading to higher-quality energy carriers (e.g. biomethane, biodiesel). Conversion efficiencies and environmental performance were derived from detailed biochemical process models combined with LCA data. With the focus here on minimizing the contribution to global warming potential, the results suggest that the largest untapped potential is found among crop residues, sent to direct combustion or bioethanol biorefineries, and through co-digestion of animal manures. About 30-40% of the total energy demand could be covered by domestically-available biomass and other renewables. When energy crops are considered, willow and Miscanthus are highlighted as the best alternatives under Danish conditions. Enforcing a minimum share of 25% renewables in road transport (e.g. simulating a policy constrain) leads to a shift for several biomass substrates from direct combustion to gasification with the syngas subsequently being upgraded to biofuels. Although the optimization model is currently limited to an annual energy balance, not reflecting temporal variations of demand and supply, the results show that it constitutes a powerful tool to systematically identify the optimal utilization strategies for a wide range of biomass substrates.
|11:00||Allen Brackley, David Nicholls, Maureen Puettmann and Elaine Oneil
Life cycle assessment of wood pellet consumption for residential heating in southeast Alaska
ABSTRACT. This research evaluates several scenarios for southeast Alaska pellet use for residential heating. A life cycle assessment (LCA) was conducted comparing wood pellets imported to southeast Alaska versus being locally produced. This cradle-to-grave LCA compared carbon release differences between imported wood pellets, locally produced pellets, locally produced cordwood, and refined fuel oil. We compared 5 scenarios, including current fuel use (close to 0 percent pellets), as well as 20, 40, and 100 percent wood pellet penetration into the refined fuel oil heating market. Cordwood use for residential heating was assumed to remain constant for all comparisons. Eight communities within southeast Alaska were evaluated, ranging in population from less than 1,000 to more than 30,000. This research found that global warming potential (in terms of CO2 equivalent) was lowered for all substitution scenarios using woody biomass, when compared to the case of 100 percent fuel oil. At 20 percent wood pellet substitution, the scenario of importing pellets from the continental U.S. differed from the scenario of locally produced pellets by only 3 percent (in terms of reduced global warming potential). At the 100 percent substitution level, CO2 emissions were reduced by 74 percent when considering locally produced pellets and 54 percent when considering imported pellets (both versus heating oil). The infrastructure necessary to establish a pellet market in southeast Alaska will likely be the largest hurdle in establishing a viable pellet industry, serving regional markets. Further, lack of wood drying facilities and adverse weather conditions can create unique challenges for southeast Alaska. An estimated 43,492 bone dry tons of biomass are available on Prince of Wales Island in southeast Alaska, close to the amount required under the scenario of 20 percent substitution (estimated to be 44,761 bone dry tons). However resource use is still an outstanding issue in southeast Alaska, and estimating future timber harvest and the availability of material suitable for energy has large uncertainties. The results of this study strongly indicate the environmental advantage of increase use of wood based biofuels in southeast Alaska for residential heating in terms of life cycle CO2 reductions. Environmental benefits can be further enhanced when wood fuel is produced within southeast Alaska markets versus transported from the continental U.S. by water. Although this research focused primarily on carbon impacts, there are several other environmental benefits associated with fuel substitutions, including smog, respiratory effects, and ozone depletion.
|11:15||Terrie Boguski and James McLaren
LCA Camelina Adhesive, an Emerging BioProduct and the Difficulties Associated with Evaluating a Product Yet-to-Be
ABSTRACT. In 2012, a Kansas State University-led research team was awarded $5.08 million to study the oilseed, camelina, with the overall research goal to promote development of camelina as a cost-effective bio-based product feedstock. The research team is building a foundation to help make oilseeds, such as camelina, a better resource for biofuels, chemicals and bioproducts, while also minimizing negative impacts on food crop systems and the environment. To achieve the research goals, Life Cycle Assessment (LCA) is being used to conduct preliminary assessments of three types of adhesives made from defatted camelina meal. Defatted meal is the carbohydrate and protein material after oil is removed from the camelina seed.
The LCA includes research of farming practices, including rotation of camelina with wheat crops instead of leaving fields fallow between wheat crop rotations. The LCA also includes crushing and extracting oil to produce the defatted camelina meal, process design data for commercial-scale manufacturing of camelina adhesives, application of adhesive to plywood and final disposal.
This project highlights the difficulties of using LCA to evaluate a product system not yet developed. Manufacturing data, information about material losses during manufacturing, and product economic profiles do not yet exist. The team has improved upon existing farm machinery and fertilizer data in existing LCA datasets, making these data more representative of actual use in the United States. For the not-yet-in-existence manufacturing facilities, the LCA model is set up to replace research data with actual manufacturing data, whenever such data may exist. To date, we have moved from laboratory, to pilot-scale, to modelled commercial-scale manufacturing data for the adhesive manufacturing. The journey has been interesting and enlightening.