Analyzed Impact Categories Research Articles

Comparative life cycle assessment of microalgae cultivation for non-energy purposes using different carbon dioxide sources

The ability of microalgae to sequester carbon and at the same time synthesise valuable compounds with potential applications in nutraceutical, pharmaceutical and cosmetic industries makes them attractive for commercial deployment, especially in view of a blue bioeconomy. Among microalgae, the diatom Phaeodactylum tricornutum is considered as an important potential source of omega-3 polyunsaturated fatty acids, such as eicosapentanoic acid, an essential polyunsaturated fatty acid with anti-inflammatory and antimicrobial properties. The aim of this study was to perform the Life Cycle Assessment of the cultivation of P. tricornutum - at semi-industrial scale in photobioreactor - for the production of high-quality bioactive compounds comparing synthetic carbon dioxide supply to a supply with waste carbon dioxide from a biogas upgrading process hypothesizing industrial symbiosis network. The effect of renewable energy use instead of the European electricity mix was also examined. Primary data on the production process, including the stages of cleaning and sterilisation, cultivation, harvesting and freeze-drying, were used. The midpoint impact categories recommended in the ILCD Handbook were used for performing the impact assessment. A sensitivity analysis was also performed on algal productivity, culture medium recirculation factor and amount of solvents per cleaning cycle. Firstly, results indicate in general cultivation and freeze-drying as the most contributing stages to the impacts. Secondly, they demonstrate in the comparative assessment that the use of carbon dioxide from the biogas upgrading is a feasible and attractive alternative to the synthetic one, as it allows for the improvement of the environmental performance of the production process in all the analysed impact categories. Finally, sensitivity analysis suggests that the environmental performance could be further improved by acting on other key factors, such as electricity source, nutrients culture medium and cleaning solutions.

Environmental impacts of CO2-based chemical production: A systematic literature review and meta-analysis

Carbon capture and utilization (CCU) is perceived as a technology to mitigate climate change and conserve non-renewable resources, especially in the chemical industry. Numerous life cycle assessments (LCA) of individual CCU systems have been carried out. The goal of this review is to understand the environmental effects of CO2-based chemical production comprehensively. In order to achieve this goal, a systematic literature review and a meta-analysis were conducted. 52 peer-reviewed articles were found that deal with LCA and CO2-based chemical production. Amongst the case studies found, the methodological choices and technological parameters differ. The meta-analysis reveals that there is no CO2-based chemical production technology that performs better in all analyzed impact categories (IC) compared to conventional production. Nevertheless, looking at the results from the meta-analysis, it has been found that the CO2-based production of formic acid (FA) via H2 is a promising CCU pathway. FA produced via hydrogenation performs better in 11 out of 15 ICs using the German grid mix as the electricity supplier and better in 14 out of 15 ICs using wind power as the electricity supplier compared to the conventional production. The global warming impact of FA production can be reduced by 95.01% when produced via CO2 hydrogenation. The meta-analysis also unveils CCU technologies that are not favorable from an environmental perspective because CO2-based kerosene and dimethyl carbonate (DMC) production lead to higher impacts in all ICs compared to conventional production. This study can inform decision-makers about the differences in published LCA studies on CCU and the harmonized environmental impacts of CO2based chemical production.

Environmental assessment of CO2 mineralisation for sustainable construction materials

Mineral carbonation is a carbon utilisation technology in which an alkaline material reacts with carbon dioxide forming stable carbonates that can have different further uses, for instance as construction material. The alkaline material can be a residue from industrial activities (e.g. metallurgic slags) while CO2 can be recovered from industrial flue gasses. Mineral carbonation presents several potential environmental advantages: (i) industrial residues valorisation, (ii) CO2 sequestration and (iii) substitution of conventional concrete based on Portland cement (PC).However, both the carbonation and the CO2 recovery processes require energy. To understand the trade-off between the environmental benefits and drawbacks of CO2 recovery and mineral carbonation, this study presents a life cycle assessment (LCA) of carbonated construction blocks from mineral carbonation of stainless steel slags. The carbonated blocks are compared to traditional PC-based concrete blocks with similar properties.The results of the LCA analysis show that the carbonated blocks present lower environmental impacts in most of the analysed impact categories. The key finding is that the carbonated blocks present a negative carbon footprint. Nonetheless, the energy required represents the main environmental hotspot. An increase in the energy efficiency of the mineral carbonation process and a CO2 valorisation network are among the suggestions to further lower the environmental impacts of carbonated blocks production.Finally, the LCA results can promote the development of policy recommendations to support the implementation of mineral carbonation technology. Further research should enable the use of mineral carbonation on a broader range and large volume of alkaline residues.

From Laboratory to Industrial Scale: A Prospective LCA for Electrochemical Reduction of CO2 to Formic Acid.

CO2-based production technologies unveil the possibility of sustainable production in the chemical industry. However, so-called carbon capture and utilization (CCU) options do not inevitably lead to improved environmental performance, which is especially uncertain for emerging technologies compared to present production practices. Thus, far, emerging CCU technologies have been environmentally assessed with conventional life cycle assessment (LCA). Therefore, this study aims to develop a methodology for applying prospective LCA to emerging production technologies from the laboratory to industrial scale. The developed four-step approach for implementing prospective LCA is applied to the case of electrochemical formic acid (FA) production via supercritical CO2 (scCO2) under consideration of different reactor designs to guide process engineers from an environmental standpoint. While using prospective LCA, the underlying modeling approach relies on consequential LCA (cLCA). Fourteen out of the 15 analyzed impact categories (IC) reveal lower environmental impacts for the scale-ups, which are based on the best-case assumptions and on a flow-through regime compared to the conventional FA production. Nevertheless, the impacts of the scale-ups that are based on a batch reactor (BR) and a three compartment cell (TCC) are higher than for the best case and the flow-through reactor scale-up.

Life cycle assessment of liquid inverted sugar and high-fructose corn syrup

The aim of this study is to compare the environmental impact of liquid inverted sugar (77°Bx) produced with enzymatic hydrolysis of beet sugar and HFCS (75% DM) produced from corn in a wet milling process. Given the different sweetness equivalents of liquid inverted sugar (77°Bx) and HFCS (75% DM), the reference flows were defined as 900 kg of liquid inverted sugar or 1000 kg HFCS. The analysis was performed with the life cycle assessment (LCA) method focusing on the cradle-to-gate stage. The inventory data of liquid inverted sugar processing were supplied by a producer while the LCA of HFCS relies on secondary data (literature) which describes the material and energy flows associated with glucose production. Life cycle inventory of relevant inputs and outputs were available from the Ecoinvent 3.4 database. Environmental impacts were calculated with the ReCiPe 2016 (H) life cycle impact assessment (LCIA) method. LCA results have revealed that inverted liquid sugar has a lower impact in 14 out of the 18 analysed impact categories. Consumption of inverted liquid sugar (>77°Bx) instead of HFCS (75% DM) could lead to significant reduction in GHG emissions (by 38%), fossil energy (by 31%) and water (by 95%) consumption, and reduces the required land area by 67%.

Reusing exterior wall framing systems: A cradle-to-cradle comparative life cycle assessment

The construction industry consumes 40% of the global materials and produces one of the largest waste streams in the planet. In a circular economy, the reuse of building components in multiple life cycles aims at increasing resource efficiency and eliminating waste. But can reuse offset the environmental impacts of materials with high embodied energy (e.g. steel)? If so, in what conditions? In the study presented in this paper, the authors used two different life cycle assessment (LCA) methods to compare a single-use wood-framed wall against a reusable steel-framed wall in a tiny house in the U.S. The analyzed impact categories were global warming potential, embodied energy, and water use. One of the main goals of this study was to understand the benefits of reusing a material with high embodied energy when compared to a single-use alternative. Another equally important objective was to understand how different LCA methods can influence the results in a cradle-to-cradle (C2C) LCA. As results, reuse benefits depended on aggressive reuse rates (>70%) and multiple reuses of steel were needed to offset the embodied environmental impacts during steel production. Also, the analyses showed that process-based LCA and hybrid LCA can generate conflicting results in a C2C LCA.

Life cycle assessment and costing of wastewater treatment systems coupled to constructed wetlands

This study evaluates the environmental and economic performance (ecoefficiency) of two decentralized, small-scale, wastewater treatment systems coupled to constructed wetlands. System One comprises a vertical and a horizontal flow wetland. System Two comprises a vertical subsurface flow wetland with artificial aeration. A life cycle assessment based on data from two actual pilot structures was carried out. The functional unit was 1 m3 of treated water over a 20-year long lifetime. The systems were modeled in open LCA software, with the aid of Ecoinvent 3.3 data, and the impact assessment was based on the ReCIPe method. Results have demonstrated that foreground emissions such as direct greenhouse gas released from the septic tank and nutrients released in the effluent have driven potential impacts related to Climate Change, Photochemical Oxidants, and Freshwater Eutrophication. Artificial aeration reduces the area required for the installation of the system and electricity consumption was responsible for only 7% of total Climate Change related potential impact. Technologies that reduce direct (foreground) liquid and airborne emissions will improve the environmental performance of the systems. The analysis of the aerated wetland has shown that the operation stage had the greatest environmental impact potential for all analyzed impact categories, with results varying between 64% for Human Toxicity and 100% for Freshwater Eutrophication. The life cycle cost per cubic meter of treated sewage for the aerated system was 1.8 times smaller than that of the system without aeration. Thus, aeration is cost-effective for small-scale wastewater treatment systems coupled to constructed wetlands.

Evaluation of potential environmental impacts related to two organic waste treatment options in Italy

This paper aims at evaluating the environmental impact of two types of organic fraction of municipal solid waste treatment techniques – composting and anaerobic digestion with post-composting – by using the life cycle assessment (LCA) methodology. The analysis concerns a facility of municipal solid waste selection and composting, which is located in Italy and where currently there is only a composting line. Two LCA implementations will be presented -- one on the current status and one on the future option – where, according to the plant expansion plan, an anaerobic digestion line is expected to be introduced. This line will allow obtaining electricity and heat as a result of a cogeneration process fuelled by the produced biogas. Following the characterisation results, currently the compost production phase assumes the highest values in 9 out of 18 analysed impact categories, while the landfill phase prevails in the remaining 9. As far as the option to be implemented in the future is concerned, the stage that affects the most (for 8 categories) is sewage treatment, followed by landfill (6 of them) and finally by the compost production (for the remaining 4). The parallel analysis of the two organic waste treatment methods showed that the best one is the anaerobic/composting digestion solution, obtaining lower scores with respect to the sole composting option (apart from the photochemical formation of oxidants impact category).

Environmental life cycle assessment of electric vehicles in Poland and the Czech Republic

Electric vehicles (EVs) are the future of road transport in both Poland and the Czech Republic and offer significant potential for reducing air pollution and increasing life comfort, especially in crowded city centers. This paper presents a comparative life cycle assessment (LCA) of EVs in Poland and the Czech Republic, considering the life cycle from cradle to grave, with a special focus on the production of the electricity required to charge EV batteries. The analyses included the current and future energy systems (from 2015 to 2050) used to charge EV batteries in the both countries. A comparative analysis of EVs and passenger vehicles with internal combustion engines (ICEVs) was carried out. In addition, the analyses considered scenarios of smart grids from which the energy for the charging of EV batteries could be supplied exclusively from renewable sources. The results showed that the environmental burden of current and future EVs is higher in Poland than in the Czech Republic for all analyzed impact categories and that this result is primarily related to the type of electricity used to charge EV batteries. The comparative analysis of EVs and ICEVs showed that greenhouse gas (GHG) emissions and fossil fuel depletion in Poland and the Czech Republic, both at present and in the future, will be lower in the case of EVs than in the case of ICEVs. However, the acidification, eutrophication, human toxicity, and particulate matter formation caused by EVs are higher than those caused by ICEVs. The results showed that EVs coupled with renewable electricity sources offer the potential to reduce the negative impacts on the environment. It was concluded that the main determinant of the environmental impact of EVs is the type of electricity used to charge EV batteries. This is the first attempt at a comparative LCA of EVs in Poland and the Czech Republic. It is also the first approach that includes analyses of the LCA for both the present and future electricity production systems used for charging EV batteries.

Life cycle assessment of municipal solid waste management scenarios on the small island of Mauritius.

The aim of this study was to use the life cycle assessment tool to assess, from an environmental point of view, the different possible municipal solid waste (MSW) management scenarios for the island of Mauritius. The scenarios include landfilling with energy recovery (S1), incineration with energy recovery (S2), composting, incineration and landfilling (S3) and finally composting, recycling, incineration and landfilling (S4). The MSW generated in 2010 was selected as the functional unit. Foreground data were collected through surveys and literature. Background data were obtained from ecoinvent data in SimaPro 8 libraries. The scenarios were compared both through the CML-IA baseline-midpoint method and the ReCiPe end-point method. From the midpoint method, the results obtained indicates that landfilling (S1) has the greatest impact in all the analyzed impact categories except ozone layer depletion and human toxicity, while incineration (S2) has the least impact on almost all the analyzed damage categories except in global warming potential and human toxicity. The collection and transportation of waste has a significant impact on the environment. From the end-point method, S4 reduces the damage impact categories on Human Health, Ecosystems and Resources due to the recycling process. S3 is not favorable due to the impact caused by the composting process. However, it is also very important to emphasize that for incineration, the best available technology with energy recovery shall be considered. It is recommended that S2 and S4 are considered for strategic planning.

Allocation strategies in comparative life cycle assessment for recycling: Considerations from case studies

The objective of this research is to verify whether an end-of-life allocation strategy can affect the choice between two products or two processes. This study evaluates whether a comparison between two products/processes that is obtained by applying the cut-off (CO) approach and substitution method (Sub) can cause a sign reversal for products/processes with different recyclability features. The main intent is to provide a clear picture for Life Cycle Assessment practitioners, who analyze recycling systems and would benefit by knowing whether an end-of-life allocation strategy can affect the preference ranking between products or processes. Two comparative case studies were developed using primary data. The case studies were very different because they referred to different sectors. In the first case study, the analyzed subjects were two plastic products; in the second case study, the analyzed subjects were an incineration line under design and an incineration line under operative conditions. For the first case study, the allocation strategies were implemented in the modeling of the burdens of input waste and end-of-life disposal. For the second case study, the allocation strategies were implemented in the modeling of input waste; in the burdens of end-of-life disposal of slag, ashes and dust; in the recovery of construction materials; and in energy recovery. To confirm the main findings of the first and second cases, an additional case was simulated by combining the first and second cases. The results obtained in the two case studies and in the combined case indicate that comparisons between the analyzed products/processes are only marginally affected by the applied end-of-life allocation strategies and are consistent with both the allocation strategies for almost all of the analyzed impact categories.

Life cycle assessment of stormwater management in the context of climate change adaptation

Expected increases in pluvial flooding, due to climatic changes, require large investments in the retrofitting of cities to keep damage at an acceptable level. Many cities have investigated the possibility of implementing stormwater management (SWM) systems which are multi-functional and consist of different elements interacting to achieve desired safety levels. Typically, an economic assessment is carried out in the planning phase, while environmental sustainability is given little or no attention. In this paper, life cycle assessment is used to quantify environmental impacts of climate change adaptation strategies. The approach is tested using a climate change adaptation strategy for a catchment in Copenhagen, Denmark. A stormwater management system, using green infrastructure and local retention measures in combination with planned routing of stormwater on the surfaces to manage runoff, is compared to a traditional, sub-surface approach. Flood safety levels based on the Three Points Approach are defined as the functional unit to ensure comparability between systems. The adaptation plan has significantly lower impacts (3–18 person equivalents/year) than the traditional alternative (14–103 person equivalents/year) in all analysed impact categories. The main impacts are caused by managing rain events with return periods between 0.2 and 10 years. The impacts of handling smaller events with a return period of up to 0.2 years and extreme events with a return period of up to 100 years are lower in both alternatives. The uncertainty analysis shows the advantages of conducting an environmental assessment in the early stages of the planning process, when the design can still be optimised, but it also highlights the importance of detailed and site-specific data.

The relevance of site-specific data in Life Cycle Assessment (LCA). The case of the municipal solid waste management in the metropolitan city of Naples (Italy)

Municipal Solid Waste (MSW) is an unavoidable by-product of modern societies production and consumption patterns. Envisaging waste management strategies is a complex and challenging task, influenced by technical site-specific aspects. To achieve more informed decisions, technical experts should avoid streamlined and generalized analyses, while at the same time policy-makers should increasingly rely on LCA and other biophysical assessment approaches, which can help them identifying context-specific waste hierarchies and priorities. This paper uses site-specific data in comparing different waste management routes for the Metropolitan City of Naples. The waste management of the Metropolitan City of Naples (3 million people, Campania Region, Southern Italy) in the year 2012 is investigated as a case-study, after having faced a severe waste production and disposal crisis, that has not been totally resolved yet. An extensive collection of primary data is carried out to describe the main input/output flows associated with the treatment and recovery of each single waste fraction (Mixed Municipal Solid Waste – MMSW, Organic Fraction Municipal Solid Waste – OFMSW, Recyclable Fraction Municipal Solid Waste – RFMSW). LCA results reveal that the main burdens are caused by the treatment of MMSW (i.e. mechanical biological treatment, landfill, waste-to-energy) and by the export/transport of the OFMSW outside the region (due to the lack of local treatment plants), almost in all analyzed impact categories. The identification of the weak points along the waste management chain allows a sensitivity analysis to test the influence of potential improvements by means of a scenario analysis. Six strategies, substantially differing in terms of percentage of separate collection, transportation routes and options for the disposal of residual waste, are designed and analyzed. The achieved results point out that it is possible to improve the environmental efficiency of the waste management chain locally, in so strengthening the entire waste management process. This study confirms that LCA, if carefully conducted, allows the identification of criticalities and improvement potential towards new management strategies. The use of site-specific data of full-scale waste treatment facilities and the definition of alternative waste management hierarchies may help decision-making by local public administrators and stakeholders, providing a transparent picture and deep understanding of costs and benefits for waste management at local scale.

Sustainable urban electricity supply chain – Indicators of material recovery and energy savings from crystalline silicon photovoltaic panels end-of-life

Solar photovoltaic (PV) electricity has the potential to be a major energy solution, sustainably suitable for urban areas of the future. However, although PV technology has been projected as one of the most promising candidates to replace conventional fossil based power plants, the potential disadvantages of the PV panels end-of-life (EoL) have not been thoroughly evaluated. The current challenge concerning PV technology resides in making it more efficient and competitive in comparison with traditional fossil powered plants, without neglecting the appraisal of EoL impacts. Indeed, considering the fast growth of the photovoltaic market, started 30 years ago, the amount of PV waste to be handled and disposed of is expected to grow drastically. Therefore, there is a real need to develop effective and sustainable processes to address the needed recycle of the growing number of decommissioned PV panels. Many laboratory-scale or pilot industrial processes have been developed globally during the years by private companies and public research institutes to demonstrate the real potential offered by the recycling of PV panels. One of the tested up lab-scale recycling processes – for the crystalline silicon technology – is the thermal treatment, aiming at separating PV cells from the glass, through the removal of the EVA (Ethylene Vinyl Acetate) layer. Of course, this treatment may entail that some hazardous components, such as Cd, Pb, and Cr, are released to the environment, therefore calling for very accurate handling. To this aim, the sustainability of a recovery process for EoL crystalline silicon PV panels was investigated by means of Life Cycle Assessment (LCA) indicators. The overall goal of this paper was to compare two different EoL scenarios, by evaluating the environmental advantages of replacing virgin materials with recovered materials with a special focus on the steps and/or components that can be further improved.The results demonstrate that the recovery process has a positive effect in all the analyzed impact categories, in particular in freshwater eutrophication, human toxicity, terrestrial acidification and fossil depletion indicators. The main environmental benefits arise from the recovery of aluminum and silicon. In particular, the recovered silicon from PV waste panels would decrease the need for raw silicon extraction and refining in so lowering the manufacturing costs, and end-of-life management of PV panels. Moreover, the amount of the recovered materials (silicon, aluminum and copper, among others) suggests a potential benefit also under an economic point of view, based on present market prices.

Life Cycle Assessment of Mixed Municipal Solid Waste: Multi-input versus multi-output perspective

This paper analyses four strategies for managing the Mixed Municipal Solid Waste (MMSW) in terms of their environmental impacts and potential advantages by means of Life Cycle Assessment (LCA) methodology. To this aim, both a multi-input and a multi-output approach are applied to evaluate the effect of these perspectives on selected impact categories. The analyzed management options include direct landfilling with energy recovery (S-1), Mechanical-Biological Treatment (MBT) followed by Waste-to-Energy (WtE) conversion (S-2), a combination of an innovative MBT/MARSS (Material Advanced Recovery Sustainable Systems) process and landfill disposal (S-3), and finally a combination of the MBT/MARSS process with WtE conversion (S-4). The MARSS technology, developed within an European LIFE PLUS framework and currently implemented at pilot plant scale, is an innovative MBT plant having the main goal to yield a Renewable Refined Biomass Fuel (RRBF) to be used for combined heat and power production (CHP) under the regulations enforced for biomass-based plants instead of Waste-to-Energy systems, for increased environmental performance. The four scenarios are characterized by different resource investment for plant and infrastructure construction and different quantities of matter, heat and electricity recovery and recycling. Results, calculated per unit mass of waste treated and per unit exergy delivered, under both multi-input and multi-output LCA perspectives, point out improved performance for scenarios characterized by increased matter and energy recovery. Although none of the investigated scenarios is capable to provide the best performance in all the analyzed impact categories, the scenario S-4 shows the best LCA results in the human toxicity and freshwater eutrophication categories, i.e. the ones with highest impacts in all waste management processes.

Life Cycle Assessment of organic waste management strategies: an Italian case study

Abstract The aim of the paper was to evaluate the environmental burden of the organic waste management systems implemented in Umbria region in Italy, in order to provide useful information for taking strategic decisions aimed at the improvement and optimization. The two most widespread scenarios were analyzed: source-segregated collection followed by organic fertilizer production and not-differentiated collection followed by mechanical and biological treatment and disposal in landfill of the biostabilized material. The environmental performance was assessed through Life Cycle Assessment methodology, assuming one ton of organic waste as functional unit. Most of data for life cycle inventory were provided by actual facilities while background data were obtained from EcoInvent database. The alternative scenarios were compared through the IMPACT 2002+ method and the assessment was carried out on both midpoint and endpoint levels. Results showed that the landfilling of the undifferentiated organic waste has the least impact on the analyzed impact categories, except on the Global Warming, mostly due to the uncollected methane released by the landfill. As regards the aerobic composting of the source-segregated organic fraction, the efforts to reduce the impact should be mainly focused on the reduction of the air emissions (hydrogen sulfide, particulate, ammonia and NMVOC) from the biostabilization process. Furthermore the sensitivity analysis indicated that the increase of the biogas collection efficiency could significantly improve the performance of the not-differentiated collection scenario.

Análisis de ciclo de vida de una nueva solución arquitectónica que mejora el rendimiento térmico de la envolvente del edificio: Fachada Natural Aljibe

The objective of this work, that improves the enclosure’s thermal performance of the building, is to divulge the environmental impacts tied to a new solution of vegetated facade by means of the Life Cycle Assessment methodology with a cradle to grave system boundary. The analysis aims also at generating relevant information of the life cycle as base material for drafting a future Environmental Product Declaration. The facade’s component manufacture stage is the one presenting the highest contribution for all the analysed impact categories, with the vegetated layer being the one with the greatest impact. Conversely, the transport stage is the one presenting the least contribution, and can be considered negligible for all the analysed impact categories. Following the analysis of the results, we have obtained useful information about the most problematic aspects and components in the assessed facade’s performance, thus paving the way towards possible actions of impact reduction by the manufacturer.

Consequential LCA of two alternative systems for biodiesel consumption in Spain, considering uncertainty

Abstract This study assesses possible biodiesel pathways for the Spanish transport sector, representing the current situation. Life Cycle Assessment was carried out for two scenarios: Scenario 1, where 1 MJ of soybean biodiesel was imported from Argentina, and Scenario 2, where 1 MJ of biodiesel from used cooking oil (UCO) was manufactured in Spain. System expansion was performed to include the marginal products involved and additional functions were considered under a consequential approach. Scenario 1 included the production of palm oil in Malaysia (+25.27 g), as the marginal supplier in the global market. This also implied a decrease in the production of soybean meal in Brazil (−3.44 g). In Scenario 2, interactions in the global oil market led to changes in the opposite direction: the production of palm oil decreases in Malaysia (−26.31 g), whereas the production of soybean meal increases in Brazil (+3.58 g). Without considering emissions from Land Use Change (LUC), UCO biodiesel produced in Spain performed better than imported biodiesel from Argentina in all the analyzed impact categories but Global Warming (GW), which was 138.9% lower in Scenario 1, mainly due to the carbon uptake by soybeans in Argentina and palm trees in Malaysia. Since these results could be misleading, GHG emissions from LUC in each country were included. Indirect functions of the expanded systems appeared to have a great contribution in the overall GW impact, especially in Scenario 2. Results show that there are clear environmental benefits arising from the use of UCO biodiesel in Spain to meet the European targets, as compared to the use of imported soybean biodiesel from Argentina. The Monte Carlo simulation for both scenarios also reinforces confidence in the comparative assessment.

Weighting of environmental trade-offs in CCS—an LCA case study of electricity from a fossil gas power plant with post-combustion CO2 capture, transport and storage

Carbon capture and storage (CCS) is increasingly acknowledged as a potent global warming abatement option. It is demonstrated that whilst the global warming potential (GWP) decreases, the other environmental impact category potentials often increase in a life cycle perspective. Despite this, only a few studies clearly address this trade-off or use weighting to compare the positive and negative effects of CCS. The present life cycle assessment (LCA) study focuses, therefore, on presenting several environmental indicators and on weighting the inventory results in order to ascertain which of the analysed systems is to be preferred. The case studied is a projected gas power plant at Tjeldbergodden (Norway), where it is proposed to include post-combustion CCS. Four main scenarios have been analysed, one without and three with CCS. The principal variation between the CCS scenarios is that the steam required for amine regeneration is produced in three different ways: in a separate gas fuelled steam boiler; in a separate biomass fuelled steam boiler; and delivered from the low-pressure steam turbine in the power plant. Design information and technical specifications have been available. The study has used LCA methodology based on the ISO standard 14044, SimaPro 7.3.2.4 software and the Ecoinvent 2.0 database. The functional unit is 1 TWh electricity delivered to the grid. The following environmental impact categories have been included: GWP, acidification potential, eutrophication potential, photochemical ozone creation potential (POCP) and cumulative energy demand (CED). Three weighting methods have been used to ascertain the robustness of the weighting results: ReCiPe, EPS 2000 and IMPACT 2002+. The characterisation results show that the CCS scenarios have reduced impacts only in the case of GWP. The weighting demonstrates that in the ReCiPe model, climate change is strongly in focus, whilst in EPS 2000, human health and depletion of reserves are dominant. Climate change is also an important factor in IMPACT 2002+, together with effects on human health (respiratory inorganics). The process integration scenario has, however, the best result for all three weighting models. This contrasts with the results from the impact analysis where four of the five analysed impact categories rated the CCS-3 scenario as worse than the reference scenario. One possible option for improving the biofuel boiler scenario is to capture the CO2 from the combustion of biomass in the external steam boiler. This would not, in all probability, affect the acidification, eutrophication, POCP and CED to any significant degree, but the GWP, and hence the ReCiPe and the IMPACT 2002+, weighting results could be expected to improve. The weighting exercise has identified toxicity as a concern with regard to the biofuel boiler scenarios (CCS-2) and human health issues as having importance for the CCS-3 scenario. It would seem that process integration is a better CCS option than that of CCS providing steam from a separate steam boiler (without CCS), even where this boiler is biomass-fuelled. Any future analysis should focus both on the process integration scenario and the biofuel boiler scenario with CCS of biological CO2.