Life Cycle Assessment of Future Biorefinery Systems: Quantifying Sustainability in a Changing World

The European Union (EU) has established clear targets to develop the European bioeconomy, granting significant support for projects which focus on research and innovation in bio-based products and technologies. One technological concept within the bioeconomy is the biorefinery, which uses a cascading approach to produce multiple products from one or more biomass feedstocks. As the aim is for biorefineries to be more sustainable than their fossil-based counterparts, it is essential that the impacts of bio- based systems are considered. Life cycle assessment (LCA) is a methodology for quantifying the impacts of a product, process or system over its life cycle, and is ideally suited to determine the impacts of bio-based systems. While the method has been standardized, there is still a wide range of methodological choices which can be made by an LCA practitioner. This thesis aims to demonstrate how employing diverse LCA methodologies and integrating them with other systems’ modelling approaches can capture less-often explored complexities within the context of European biorefinery systems. The topic is first explored through the literature review conducted for this thesis, which identifies several open issues with regards to commonly used LCA methodologies and highlights several promising methodological approaches to address some of the expressed challenges. Through the research chapters of this thesis, these approaches are demonstrated by using three case studies relevant to the European biorefinery context. In the first study, the environmental, economic, and social impacts of upscaling seaweed production in Ireland are investigated. The study investigates six seaweed production pathways using a life cycle sustainability assessment (LCSA) applying conventional LCA for quantifying climate change impact, exergetic LCA for quantifying the impacts of resource use, conventional life cycle costing (LCC) for quantifying economic impact, and a novel simplified social LCA (sLCA) for quantifying social impacts via subjective wellbeing. The sustainability assessment is then merged with a prospective model determining the feasibility and impacts of reaching future production targets by estimating the ecological and spatial limitations of upscaling. The findings of the first study demonstrate the complexities of conflicting sustainability criteria and upscaling on biorefinery feedstock production. Manual wild harvesting is more environmentally and economically sustainable than cultivation pathways and more environmentally, economically, and socially sustainable than mechanical wild harvesting. However, due to a limited natural seaweed stock, wild harvesting and especially cultivation will be needed to reach future European seaweed production targets. It is therefore important that steps be taken to optimize factors influencing cultivation methods such as farm location, configuration, and size. The addendum investigates the environmental impacts of Irish seaweed transport and preservation using data collected from real industrial partners. The results show that real-world transport distances and preservation methods can have significant impact the environmental sustainability of seaweed production systems and should be optimized in future studies. In the second study, the sustainability impacts of utilizing seagrass wrack for bioenergy and fertilizer production through anaerobic digestion (AD) are investigated. This study uses LCA and LCC to quantify the sustainability of the valorisation system, but also utilizes system dynamics (SD) modelling to understand how changes to ecosystem health can impact such systems. The study integrates the results of the SD, LCA and LCC models into an extended LCC to demonstrate the true cost of ecosystem degradation and restoration on communities and on industries aiming to valorise biowaste streams within a circular economy. Specifically, the findings confirm the complexities of stakeholder perspective in waste valorisation, ecosystem dynamics, and developing sustainable biorefinery systems. From an environmental perspective, the AD of seagrass wrack performs well compared to the current waste management practice (transport to Slovenia for landfilling). However, economic viability for the AD operator can only be achieved if a sufficient gate fee is provided by the municipality. Furthermore, impact of ecosystem degradation is dependent on the perspective of the stakeholder; for the municipality, seagrass meadow degradation is preferrable due to the high cost of seagrass collection and disposal. For the AD operator, meadow degradation is not preferrable as it would decrease the potential profits from wrack valorisation. Finally, for the community and environment, meadow restoration is essential, due to the ecosystem services provided by the meadow. In the final study, the environmental and economic impacts of bio-based lactic acid production are investigated. The case study assesses the feasibility of producing high purity lactic acid from industrial wastewater and liquid digestate in Denmark, integrating process modelling and simulation with prospective LCA and techno-economic assessment to identify optimal process improvements, scales, energy sources, and market conditions. The results of the third study show that the optimal process depends on what is prioritized. All process improvements reduce global warming potential (GWP) but only some measures improve the economic impact (measured through unit production cost) at pilot scale due to the high cost of additional capital equipment. Scaling up from pilot to commercial scale significantly improves the economic impact through reduction in capital costs and labour and improvements in energy efficiency of electrical equipment, but further upscaling leads to higher economic and environmental costs due to increasing feedstock transport distances. Switching steam and electricity production from fossil to bio-based energy can significantly decrease GWP, but such technologies are currently dependent on subsidies to achieve any decrease in economic costs. Nonetheless, the findings confirm that by optimizing unit processes, scale, energy sources and market conditions, the lactic acid unit production cost and GWP can be lowered substantially compared to the base case, respectively. However, even best-case unit production cost is found to be higher than global market price, demonstrating the challenges of establishing economically viable biorefineries in Europe. The results of the case studies bring a deeper understanding to the intricacies of developing sustainable biorefinery systems; the connectioThe European Union (EU) has established clear targets to develop the European bioeconomy, granting significant support for projects which focus on research and innovation in bio-based products and technologies. One technological concept within the bioeconomy is the biorefinery, which uses a cascading approach to produce multiple products from one or more biomass feedstocks. As the aim is for biorefineries to be more sustainable than their fossil-based counterparts, it is essential that the impacts of bio- based systems are considered. Life cycle assessment (LCA) is a methodology for quantifying the impacts of a product, process or system over its life cycle, and is ideally suited to determine the impacts of bio-based systems. While the method has been standardized, there is still a wide range of methodological choices which can be made by an LCA practitioner. This thesis aims to demonstrate how employing diverse LCA methodologies and integrating them with other systems’ modelling approaches can capture less-often explored complexities within the context of European biorefinery systems. The topic is first explored through the literature review conducted for this thesis, which identifies several open issues with regards to commonly used LCA methodologies and highlights several promising methodological approaches to address some of the expressed challenges. Through the research chapters of this thesis, these approaches are demonstrated by using three case studies relevant to the European biorefinery context. In the first study, the environmental, economic, and social impacts of upscaling seaweed production in Ireland are investigated. The study investigates six seaweed production pathways using a life cycle sustainability assessment (LCSA) applying conventional LCA for quantifying climate change impact, exergetic LCA for quantifying the impacts of resource use, conventional life cycle costing (LCC) for quantifying economic impact, and a novel simplified social LCA (sLCA) for quantifying social impacts via subjective wellbeing. The sustainability assessment is then merged with a prospective model determining the feasibility and impacts of reaching future production targets by estimating the ecological and spatial limitations of upscaling. The findings of the first study demonstrate the complexities of conflicting sustainability criteria and upscaling on biorefinery feedstock production. Manual wild harvesting is more environmentally and economically sustainable than cultivation pathways and more environmentally, economically, and socially sustainable than mechanical wild harvesting. However, due to a limited natural seaweed stock, wild harvesting and especially cultivation will be needed to reach future European seaweed production targets. It is therefore important that steps be taken to optimize factors influencing cultivation methods such as farm location, configuration, and size. The addendum investigates the environmental impacts of Irish seaweed transport and preservation using data collected from real industrial partners. The results show that real-world transport distances and preservation methods can have significant impact the environmental sustainability of seaweed production systems and should be optimized in future studies. In the second study, the sustainability impacts of utilizing seagrass wrack for bioenergy and fertilizer production through anaerobic digestion (AD) are investigated. This study uses LCA and LCC to quantify the sustainability of the valorisation system, but also utilizes system dynamics (SD) modelling to understand how changes to ecosystem health can impact such systems. The study integrates the results of the SD, LCA and LCC models into an extended LCC to demonstrate the true cost of ecosystem degradation and restoration on communities and on industries aiming to valorise biowaste streams within a circular economy. Specifically, the findings confirm the complexities of stakeholder perspective in waste valorisation, ecosystem dynamics, and developing sustainable biorefinery systems. From an environmental perspective, the AD of seagrass wrack performs well compared to the current waste management practice (transport to Slovenia for landfilling). However, economic viability for the AD operator can only be achieved if a sufficient gate fee is provided by the municipality. Furthermore, impact of ecosystem degradation is dependent on the perspective of the stakeholder; for the municipality, seagrass meadow degradation is preferrable due to the high cost of seagrass collection and disposal. For the AD operator, meadow degradation is not preferrable as it would decrease the potential profits from wrack valorisation. Finally, for the community and environment, meadow restoration is essential, due to the ecosystem services provided by the meadow. In the final study, the environmental and economic impacts of bio-based lactic acid production are investigated. The case study assesses the feasibility of producing high purity lactic acid from industrial wastewater and liquid digestate in Denmark, integrating process modelling and simulation with prospective LCA and techno-economic assessment to identify optimal process improvements, scales, energy sources, and market conditions. The results of the third study show that the optimal process depends on what is prioritized. All process improvements reduce global warming potential (GWP) but only some measures improve the economic impact (measured through unit production cost) at pilot scale due to the high cost of additional capital equipment. Scaling up from pilot to commercial scale significantly improves the economic impact through reduction in capital costs and labour and improvements in energy efficiency of electrical equipment, but further upscaling leads to higher economic and environmental costs due to increasing feedstock transport distances. Switching steam and electricity production from fossil to bio-based energy can significantly decrease GWP, but such technologies are currently dependent on subsidies to achieve any decrease in economic costs. Nonetheless, the findings confirm that by optimizing unit processes, scale, energy sources and market conditions, the lactic acid unit production cost and GWP can be lowered substantially compared to the base case, respectively. However, even best-case unit production cost is found to be higher than global market price, demonstrating the challenges of establishing economically viable biorefineries in Europe. The results of the case studies bring a deeper understanding to the intricacies of developing sustainable biorefinery systems; the connections between them are explored in the case study analysis and general discussion. Due to the high economic and environmental cost of production and preservation it is recommended that cultivated seaweed only be used for high value products such as health food and bioextractives, whereas wild harvested seaweed as well as spoiled seaweed and beach wracks can be used for low value products such as energy and biochemicals. Specifically, the suggestion is to use biomass residues or wastes (e.g. spoiled seaweed, seagrass wrack, manure, food waste) as a feedstock for AD, producing bio-based electricity, heat and fertiliser. The digestate can then be combined with additional industrial, municipal or agricultural wastes (e.g. candy factory waste) to produce biofuels and biochemicals (e.g. lactic acid). The electricity produced from AD can be used to lower the environmental impact of biomass production (e.g. seaweed drying) or to the lower the impact of biorefinery processing (e.g. fermenter heating and cooling). For establishing European biorefineries, specific attention should be paid to ensuring sustainable biomass supply by understanding ecosystem dynamics, ensuring economic and environmental viability by optimising biorefinery locations, technologies, and processes, and ensuring social benefits by valuing local production and sustainable consumption. Ultimately, this research demonstrates the great potential for integrating LCA methodologies with other systems modelling approaches, for exploring the sustainability of biorefinery systems and for exploring pathways towards a sustainable future.