Life Cycle Greenhouse Gas Emissions Research Articles

Assessing Best Practices in Natural Gas Production and Emerging CO2 Capture Techniques to Minimize the Carbon Footprint of Electricity Generation.

Natural gas (NG) is expected to provide a substantial portion of electricity generation in many jurisdictions for the foreseeable future. Postcombustion carbon capture and storage (CCS) effectively abates direct CO2 emissions; however, indirect NG supply chain emissions in most jurisdictions are incompatible with climate change mitigation goals. This life cycle assessment evaluates specific opportunities to reduce the carbon footprint of combined cycle gas turbine (CCGT) generation with CCS using existing low-emission NG production practices, technologies, and processes combined with emerging CCS techniques to achieve high CO2 capture rates and mitigate startup emissions. We find baseload life cycle greenhouse gas (GHG) emission intensity ranges from 22 to 62 kgCO2e/MWh for 95-98.5% CO2 capture, within the range of published estimates for wind and photovoltaic power and considerably below prior estimates of CCGT with CCS. Low-emission NG production practices reduce other environmental impacts, which are dominated by combustion-related air pollution. We also show how interim solvent storage can effectively mitigate emissions from CCGT start/stop cycles. This work highlights the importance of mitigating both CO2 and methane emissions from NG supply chains and proposes a more nuanced discussion regarding the potential contribution of NG to the future energy supply. A surrogate model is provided to estimate life cycle GHG emissions for CCGT with CCS and user-input parameters.

Estimating the effect of biological nitrification inhibition-enabled sorghum on nitrogen fertilizer consumption, life cycle GHG emissions, farmer's benefit and fertilizer subsidy from Indian sorghum production

Biological nitrification inhibition (BNI) effectively curtails nitrogen (N) loss and enhances N utilization efficiency. BNI is increasingly important as a technology for mitigating greenhouse gas emissions and water pollution in countries with high N fertilizer consumption. This study aimed to evaluate the potential impacts of BNI-enabled sorghum varieties with a 30 % soil nitrification inhibition rate for a major sorghum-growing state (Maharashtra, India). We analysed the farm survey data collected for Rabi sorghum in 2020–2021 (n = 250) and for Kharif sorghum in 2022 (n = 209). Life cycle greenhouse gas (LC-GHG) emissions were estimated using a life cycle assessment with a cradle-to-farm gate perspective. The results showed that adoption of BNI-enabled sorghum reduced N fertilizer application in the Rabi and Kharif seasons by 8.0 % and 7.4 % and area-scaled/yield-scaled LC-GHG emissions by 15.6 % and 11.2 %, respectively, while increasing farmers' benefits slightly. These changes could reduce the government's expenditure on urea fertilizer subsidies by 9.1 %. However, many farmers indicated that they would not change N fertilizer application even if the yield per N fertilizer application increased. Even under these circumstances, area-scaled/yield-scaled LC-GHG emissions will be decreased by 11.3 % and 13.5 % in the Rabi season and 8.1 % and 10.2 % in the Kharif season, respectively. The yield and farmers' benefit will increase by 2.5 % and 4.9 % in the Rabi season and by 2.4 % and 6.5 % in the Kharif season, respectively, but the government's expenditure on fertilizer will not decrease. These results indicate that BNI-enabled sorghum can be introduced into countries where fertilizer use is low. This study shows the potential impacts of BNI-enabled sorghum under two scenarios; N fertilizer consumption is reduced or maintained. Discussions on the N fertilizer consumption under BNI-enabled sorghum are needed to establish a sustainable food system, especially in countries with high N fertilizer consumption.

Curbing household food waste and associated climate change impacts in an ageing society.

We explored the intricate quantitative structure of household food waste and their corresponding life cycle greenhouse gas emissions from raw materials to retail utilizing a combination of household- and food-related economic statistics and life cycle assessment in Japan. Given Japan's status as a nation heavily impacted by an aging population, this study estimates these indicators for the six age brackets of Japanese households, showing that per capita food waste increases as the age of the household head increases (from 16.6 for the 20's and younger group to 46.0 kg/year for 70's and older in 2015) primarily attributed to the propensity of older households purchase of more fruits and vegetables. Further, the largest life cycle greenhouse gases related to food waste was 90.1 kg-CO2eq/year for those in their 60's while the smallest was 39.2 kg-CO2eq/year for 20's and younger. Furthermore, food waste and associated emissions are expected to decline due to future demographic changes imparted by an aging, shrinking population after 2020 until 2040. Specific measures focused on demographic shifts are crucial for Japan and other countries with similar dietary patterns and demographics to achieve related sustainable development goals through suppressing food waste and associated emissions under new dietary regimes.

Environmental life-cycle analysis of hydrogen technology pathways in the United States

Hydrogen is a zero-carbon energy carrier with potential to decarbonize industrial and transportation sectors, but its life-cycle greenhouse gas (GHG) emissions depend on its energy supply chain and carbon management measures (e.g., carbon capture and storage). Global support for clean hydrogen production and use has recently intensified. In the United States, Congress passed several laws that incentivize the production and use of renewable and low-carbon hydrogen, such as the Bipartisan Infrastructure Law (BIL) in 2021 and the Inflation Reduction Act (IRA) in 2022, which provides tax credits of up to $3/kg depending on the carbon intensity of the produced hydrogen. A comprehensive life-cycle accounting of GHG emissions associated with hydrogen production is needed to determine the carbon intensity of hydrogen throughout its value chain. In the United States, Argonne’s R&D GREET® (Greenhouse Gases, Regulated emissions, and Energy use in Technologies) model has been widely used for hydrogen carbon intensity calculations. This paper describes the major hydrogen technology pathways considered in the United States and provides data sources and carbon intensity results for each of the hydrogen production and delivery pathways using consistent system boundaries and most recent technology performance and supply chain data.

Evaluating the levelized costs and life cycle greenhouse gas emissions of electricity generation from rooftop solar photovoltaics: a Swiss case study

Abstract The transition to renewable energy sources is pivotal in addressing global climate change challenges, with rooftop solar photovoltaic (PV) systems playing a crucial role. For informed decision-making in energy policy, it is important to have a comprehensive understanding of both the economic and environmental performance of rooftop solar PV. This study provides a high-resolution analysis of existing rooftop solar PV systems in Switzerland by assessing the robustness of the potential estimation to properly derive the amount of electricity generated by individual systems, and subsequently quantify the levelized cost of electricity and life cycle greenhouse gas (GHG) emissions of electricity generation from PV and compare them with those of grid electricity supplies. Our results indicate substantial geographical variations between potential estimations and real-world installations, with notable underestimations of approximately 1.3 Gigawatt-peak, primarily for systems around 10 kWp in size, mainly due to the quality of input data and conservative estimation. The study finds that in many regions and for most of the installed capacity, electricity generated from rooftop PV systems is more economical than the grid electricity supply, mainly driven by factors including high electricity prices, larger installations and abundant solar irradiance. The GHG emissions assessment further emphasizes the importance of methodological choice, with stark contrasts between electricity certificate-based approaches and others that are based on the consumption mix. This study suggests the need for more accurate geographical potential estimations, enhanced support for small-scale rooftop PV systems, and more incentives to maximize the potential of their roof area for PV deployment. As Switzerland progresses towards its renewable energy goals, our research underscores the importance of informed policymaking based on a retrospective analysis of existing installations, essential for maximizing the potential and benefits of rooftop solar PV systems.

Considering Embodied Greenhouse Emissions of Nuclear and Renewable Power Plants for Electrolytic Hydrogen and Its Use for Synthetic Ammonia, Methanol, Fischer-Tropsch Fuel Production.

Recent concerns surrounding climate change and the contribution of fossil fuels to greenhouse gas (GHG) emissions have sparked interest and advancements in renewable energy sources including wind, solar, and hydroelectricity. These energy sources, often referred to as "clean energy", generate no operational onsite GHG emissions. They also offer the potential for clean hydrogen production through water electrolysis, presenting a viable solution to create an environmentally friendly alternative energy carrier with the potential to decarbonize industrial processes reliant on hydrogen. To conduct a full life cycle analysis, it is crucial to account for the embodied emissions associated with renewable and nuclear power generation plants as they can significantly impact the GHG emissions linked to hydrogen production and its derived products. In this work, we conducted a comprehensive analysis of the embodied emissions associated with solar photovoltaic (PV), wind, hydro, and nuclear electricity. We investigated the implications of including plant-embodied emissions in the overall emission estimates of electrolysis hydrogen production and subsequently on the production of synthetic ammonia, methanol, and Fischer-Tropsch (FT) fuels. Results show that average embodied GHG emissions of solar PV, wind, hydro, and nuclear electricity generation in the United States (U.S.) were estimated to be 37, 9.8, 7.2, and 0.3 g CO2 e/kWh, respectively. Life cycle GHG emissions of electrolytic hydrogen produced from solar PV, wind, and hydroelectricity were estimated as 2.1, 0.6, and 0.4 kg of CO2 e/kg of H2, respectively, in contrast to the zero-emissions often used when the embodied emissions in their construction were excluded. Average life cycle emission estimates (CO2 e/kg) of synthetic ammonia, methanol, and FT-fuel from solar PV electricity are increased by 5.5, 16, and 49 times, respectively, compared to the case when embodied emissions are excluded. This change also depends on the local irradiance for solar power, which can result in a further increase of GHG emissions by 35-41% in areas of low irradiance or reduce GHG emissions by 21-25% in areas with higher irradiance.

Life cycle greenhouse gas emissions assessment: converting an early retirement coal-fired power plant to a biomass power plant

Decommissioning aging coal-fired power plants (CFPPs) represents an effective strategy for reducing greenhouse gas (GHG) emissions, accelerating energy mix diversification, and achieving nationally determined contributions and net-zero emissions targets. However, dismantling the CFPP and building a renewable energy-based power plant with a capacity equal to a dismantled CFPP could burden state finances. Therefore, converting coal to 100% biomass fuel in the aging CFPP is one of the proposals that needs to be studied. This study conducted an environmental assessment concerning the Life Cycle Greenhouse Gas (LC GHG) emissions, encompassing raw material extraction and power plant operation. Five scenarios were analyzed. Two scenarios related to using sawdust and agroforestry residue for biomass fuel in the aging CFPP. The other three scenarios used biomass fuel from Calliandra wood harvested from tropical forests, production forests, and marginal land, which produced GHG emissions from Land Use Change (LUC). This study demonstrates that sawdust and agroforestry residue can reduce global warming impacts compared to coal. The LUC in higher carbon stock land will increase global warming impacts, while the LUC in lower carbon stock land will reduce global warming impacts. A decrease in the aging CFPP efficiency, when coal is converted to 100% biomass, will cause an increase in global warming impacts.

Life cycle greenhouse gas emissions and cost of energy transport from Saudi Arabia with conventional fuels and liquified natural gas

The International Maritime Organization has recently developed several regulations to reduce greenhouse gas (GHG) emissions. To meet these targets, ship builders and operators must either replace or upgrade the existing fleet with new decarbonized vessel technologies and/or switch to alternative fuels. The latter has been of interest, especially using liquified natural gas (LNG), among other alternative fuels, which can have lower emissions than conventional fuels. In Saudi Arabia in 2023, LNG was priced about 10 times lower than in Europe. In this study, Well-to-Wake life cycle GHG emissions and cost are calculated for a SUEZMAX tanker operating with three fuel options: high sulfur fuel oil, very low sulfur fuel oil and LNG. This is done for two different trips, for Saudi Arabia to Japan and Saudi Arabia to the Netherlands. Results show 11% and 12% life cycle GHG emissions reduction with LNG for trips to the Netherlands and Japan, respectively. From a sensitivity analysis of methane slip, LNG cost and anchoring time, the cost of GHG abatement for the LNG vessel varied from 171 United States dollars (USD) to –255 USD, and from 206 USD to –191 USD per ton of GHG, for the trip to the Netherlands and Japan, respectively.

Assessment of life cycle environmental impacts of materials, driving pattern, and climatic conditions on battery electric and hydrogen fuel cell vehicles in a cold region

Battery electric vehicles (BEVs) and hydrogen fuel cell vehicles (HFCVs) can play an important role in addressing climate change by diminishing greenhouse gas (GHG) emissions in the worldwide road transportation sector. There is limited research on the implications of the use of lightweight materials, driving pattern, and climatic impact on the life cycle GHG emissions in a cold region. To address this limitation, we developed a framework to assess eighteen BEV and four HFCV scenarios for a cold region that consider aforementioned parameters through a combination of driving patterns (in rural, city, and highway driving) and climatic conditions (i.e., summer, mild winter, and severe winter) for both conventional and carbon fiber-reinforced plastic (CRFP)-based BEVs. A case study was conducted for Canada, considering its cold regions, using available data for HFCVs. We assessed city driving in summer and highway driving in severe winter conditions for conventional and CFRP-based HFCVs. The results show that the lowest GHG emissions are in cities in summer, with life cycle GHG emissions values of 68.7 g CO2 eq/km for CFRP-based BEVs. The highest life cycle GHG emissions are 364.4 g CO2 eq/km with conventional HFCVs on the highway in severe winter conditions' scenario. The operation phase emerges as the primary contributor to life cycle GHG emissions, closely trailed by the production phase. The analysis shows that the most sensitive parameters for CFRP-based BEVs in the city in summer scenario are vehicle lifetime and for conventional HFCVs in the highway in severe winter scenario, fuel cell efficiency. The analysis also shows the range of life cycle GHG emissions for a cold region, with conventional HFCVs on highways in severe winter conditions exhibiting the highest emissions (331.0 g CO2 eq/km) and CFRP-based HFCVs in the city in summer scenario the lowest (51.0 g CO2 eq/km).

Environmental impacts of biodegradable microplastics

Biodegradable plastics, perceived as ‘environmentally friendly’ materials, may end up in natural environments. This impact is often overlooked in the literature due to a lack of assessment methods. This study develops an integrated life cycle impact assessment methodology to assess the climate-change and aquatic-ecotoxicity impacts of biodegradable microplastics in freshwater ecosystems. Our results reveal that highly biodegradable microplastics have lower aquatic ecotoxicity but higher greenhouse gas (GHG) emissions. The extent of burden shifting depends on microplastic size and density. Plastic biodegradation in natural environments can result in higher GHG emissions than biodegradation in engineered end of life (for example, anaerobic digestion), contributing substantially to the life cycle GHG emissions of biodegradable plastics (excluding the use phase). A sensitivity analysis identified critical biodegradation rates for different plastic sizes that result in maximum GHG emissions. This work advances understanding of the environmental impacts of biodegradable plastics, providing an approach for the assessment and design of future plastics.

Impacts of alternative fuel combustion in cement manufacturing: Life cycle greenhouse gas, biogenic carbon, and criteria air contaminant emissions

Waste products destined for landfills with high calorific value are increasingly being explored for potential use in a variety of industries. One example is the potential use of these wastes in cement kilns to reduce greenhouse gas (GHG) emissions from cement production. This study develops a cradle-to-gate life cycle assessment (LCA) model to estimate the GHG emissions, criteria air contaminants (CAC), and the impact of biogenic carbon accounting methods in biomass-containing alternative fuels (AFs) on life cycle GHG emissions when replacing natural gas with AFs at a cement facility. The proposed AF mixture includes landfill wastes like construction and demolition waste, asphalt shingles, tire fluff, carpet, textiles, and plastics. While many LCAs assume the biogenic fraction's climate impact is carbon-neutral, its actual effects depend on a range of new methods being proposed to account for the climate impacts associated with biogenic carbon. The findings of this study demonstrate a reduction of approximately 7–13% in life cycle GHG emissions. The preliminary estimates suggest that the change to CACs will likely not be materially different from the current use of natural gas. It also emphasizes the importance of accounting for the biogenic fraction in biomass-based AFs, indicating a potential overall reduction of up to 7.2% in life cycle GHG emissions when the biogenic fraction is treated as carbon-neutral. While factoring in the benefits of shorter rotation and longer storage periods results in a 12.7% reduction in life cycle GHG emissions. The LCA model developed in this study holds the potential for broad application among cement facilities that are considering fossil to alternative fuels as part of their GHG emission reduction strategies.

US urban land-use reform: a strategy for energy sufficiency

Policy approaches to the global energy transition often focus on technology-based solutions while ignoring challenges of overall energy demand. A sufficiency-first approach aims to limit superfluous consumption while achieving wellbeing for all. This study focuses on US built environment mechanisms of sufficiency under urban land-use policy. The historical context of US exclusionary and car-oriented planning is reviewed with an order-of-magnitude assessment of the effects on greenhouse gas emissions (GHGE). Using national vehicle-miles traveled (VMT) data derived from mobile device locations (Replica) and validated here with federal data, a hypothetical scenario explores the potential for state urban land-use reforms to enable energy sufficiency. Tenth percentile-VMT (per capita) neighborhoods are defined by state: in 47 states, the typical such neighborhood has less than 33% of its housing units in structures larger than four units. Assuming each state redresses its housing shortage while matching this VMT, 31 Mt CO2e (direct GHGE) and about 38 Mt CO2e (indirect and life-cycle GHGE) would be avoided in 2033. Texas, California, and Florida have the largest absolute emissions reduction opportunity. Urban land-use reforms comprise a logical starting point for a US sufficiency agenda. Key priorities for research, data collection, and technology and policy innovation are proposed. Policy relevance International climate policy is increasingly focused on enabling people to consume less energy: not just technological ‘efficiency’ but ‘sufficiency’ is needed. However, sufficiency has seen little uptake in the US. It may be more relevant to US policymakers if related to the growing momentum for reforming land-use planning and housing policy to address the housing shortage and affordability crisis. This crisis stems in part from the US prevalence of single-family zoning and car-centric planning, rooted in a history of racial segregation; these same laws effectively mandate people to maintain more polluting lifestyles. This study estimates how much climate pollution could be avoided with state-led land-use reform. If states committed to solving the housing shortage while building new housing in neighborhoods where people can drive less, the savings could be comparable with expanding electric vehicle policies. Policymakers and practitioners can enable these reforms while supporting complementary policy goals.

Analysis of emission reduction strategies for the use of alternative fuels and natural carbon sinks in international bulk shipping

This research examines four categories of international bulk carriers and forecasts their ability, from 2025 to 2050, to meet the IMO targets for emission reduction: a 20% reduction by 2030 and a 70% reduction by 2040 compared to 2008 levels, with the ultimate aim of achieving net-zero emissions by 2050, utilizing a life cycle assessment (LCA) methodology. It evaluates various scenarios involving different rates of ship demolition and alternative fuel adoption to achieve these targets. Additionally, it investigates the potential costs associated with carbon credits and natural carbon sinks (such as seagrass) in cases where emissions targets are not met. The findings suggest that, under the baseline scenario and Scenario 1, despite increased usage of alternative fuels and declining emission factors, none of the four ship types meet the IMO targets in terms of life cycle greenhouse gas (GHG) emissions. However, in Scenario 2, where the ship demolition rate steadily increases until the usage of traditional fuel ships reaches zero, and with concurrent reductions in emission factors, emissions decrease substantially and approach the desired targets, though they still fall short. Furthermore, the study analyzes the financial implications of employing carbon credits versus natural carbon sinks to offset emission shortfalls, indicating that Scenario 2 is comparatively less costly. It also demonstrates that leveraging natural carbon sinks is more cost-effective in reducing emission expenses compared to relying solely on carbon credits. Consequently, the research recommends prompt adoption of alternative fuels, acceleration of ship demolition rates, and utilization of natural carbon sinks not only to meet international shipping emission reduction objectives but also to rejuvenate marine ecosystems, thereby fortifying marine environments.

Life cycle GHG emissions and economic viability of two levulinic acid production processes from biomass: A case study of Japan and Canada

We evaluated CO2 equivalent (CO2eq) greenhouse gas (GHG) emissions and minimum selling price of levulinic acid (LA) produced in two biomass-waste-based processes: the AlCl3/choline chloride (ChCl) process, and the formic acid (FA) process, with catalysts recycling. Six scenarios were synthesized to compare the performances of the two processes in Japan and Canada. In the AlCl3/ChCl process, the total GHG emission was 11.35–11.56 kg-CO2eq/kg-LA and those from the energy input to the pretreatment and ChCl production were 5.22 and 3.90 kg-CO2eq/kg-LA, respectively. In the FA process, the total GHG emission was 9.46–9.68 and 22.29–22.51 kg-CO2eq/kg-LA for 60 wt% and 80 wt% FA, respectively. The operational emissions for makeup FA input were 7.65 and 20.80 kg-CO2eq/kg-LA (60 wt% and 80 wt%, respectively), which accounted for more than 80% in all scenarios. The optimization of the product purge volume, FA concentration in the pretreatment, and FA production using biomass and/or renewable energy are critical parameters to reduce overall environmental impacts of the processes. The liquid content of the solid residue (moisture, water soluble organic matters, and catalyst) had insignificant influences on the GHG emission and minimum selling price. In the FA process, combustion of solid residue can compensate the GHG emissions from the reaction and separation units.

Decarbonizing of power plants by ammonia co-firing: design, techno-economic, and life-cycle analyses

ABSTRACT This research investigates the decarbonization of India’s electricity grid using ammonia in power plants. It focuses on ammonia produced in Western Australia and transported to India, co-fired with high rank coal, and compared with power plants utilizing carbon capture and sequestration (CCS). The study assesses the overall costs and the life cycle greenhouse gas (LC GHG) emissions for both new plants and retrofits. For 20% gray, blue, and green ammonia, the levelized cost of electricity is 86, 89, 125 $/MWh, with corresponding LC GHG emissions of 1,234, 1,079, and 1,062 kg CO2e/MWh. Co-firing with green ammonia, though more expensive than blue ammonia, yields lower CO2 emissions. Conversely, reducing the same amount of direct CO2 emission via CCS costs $84/MWh and a LC GHG emission of 1,227 kg CO2e/MWh. While CCS is cheaper, it results in higher LC GHG. There is a trade-off between cost and emissions across the strategies. Under scenarios with low capacity factors or reduced ammonia production costs, coal-ammonia co-firing could become more economical and greener than the CCS. This study provides quantitative insights for policymakers and project developers. However, it is crucial for decision-makers to consider several factors: (1) the potential impact of social resistance to CCS; (2) the time required for large-scale commercialization of CCS technology, which is expected to be significantly longer than the implementation time for a coal-ammonia co-firing decarbonization strategy; (3) the potential of either CCS or ammonia-coal co-firing strategy to enhance India’s electricity mix, thus contributing to energy security.

Life-cycle analysis of hydrogen production from water electrolyzers

The United States' focus on decarbonization has spawned interest among policymakers in deploying water electrolysis technology for clean hydrogen production. However, water electrolyzers also raise concerns regarding their substantial use of carbon-intensive materials. Here, we conduct a comprehensive life-cycle analysis (LCA) of three prominent water electrolyzer technologies to investigate the environmental implications of their manufacturing and life cycles under different energy sources. All electrolyzer technologies employing low-carbon energy (nuclear, solar, or wind) exhibit life-cycle greenhouse gas (GHG) emissions of 0.3–2.4 kg-CO2-eq/kg-H2. This is significantly lower than the corresponding GHG emissions for hydrogen production via both conventional steam methane reforming and alternative autothermal reforming with carbon capture and storage (by > 50%). The well-to-gate GHG emissions of low-carbon electrolyzers (0–0.36 kg-CO2-eq/kg-H2) qualify for Tier I of the production tax credit in the U.S.’ Inflation Reduction Act of 2022, indicating their suitability for producing decarbonized hydrogen under this program.

Carbon savings from sugarcane straw-derived bioenergy: Insights from a life cycle perspective including soil carbon changes

Sugarcane straw removal for bioenergy production will increase substantially in the next years, but this may deplete soil organic carbon (SOC) and exacerbate greenhouse gas (GHG) emissions. These aspects are not consistently approached in bioenergy life cycle assessment (LCA). Using SOC modeling and LCA approach, this study addressed the life cycle GHG balance from sugarcane agroindustry in different scenarios of straw removal, considering the potential SOC changes associated with straw management in sugarcane-cultivated soils in Brazil. Long-term simulations showed SOC losses of up to −0.5 Mg ha−1 yr−1 upon complete straw removal, whereas the moderate removal had little effects on SOC and the maintenance of all straw in the field increased SOC accumulation by up to 0.4 Mg ha−1 yr−1. Our analysis suggests that accounting for SOC changes in LCA calculations could lower the net GHG benefits of straw-derived bioenergy, whose emissions intensity varied according to soil type. Overall, SOC depletion induced by complete straw removal increased the life cycle GHG emissions of straw-derived bioenergy by 26 % (3.9 g CO2eq MJ−1) compared to a scenario without taking SOC changes into account. Straw removal for cellulosic ethanol could be effective for mitigating GHG emissions relative to gasoline, but it was not advantageous for bioelectricity generation depending on the energy sources that are displaced. Therefore, straw-induced change of SOC stocks is a critical factor to model life cycle GHG emissions of straw-derived bioenergy.

Are alpine floatovoltaics the way forward? Life-cycle environmental impacts and energy payback time of the worlds’ first high-altitude floating solar power plant

Floating photovoltaics (FPV) and high-altitude PV installations are increasingly gaining importance in the sustainable energy sector, each technology holding its own potential. A pioneering high-altitude FPV installation in Switzerland represents the first implementation of combining the two technologies. In order to determine the environmental performance of such an installation, the present study examines the life-cycle environmental impact of the world’s first high-altitude FPV system, using Life Cycle Assessment (LCA). Our results record life-cycle greenhouse gas emissions of 94 g of CO2–eq per kWh of electricity produced by the high-altitude FPV system. The non-renewable primary energy demand amounts to 10′810kWh oil-eq/kWp, which equals an energy payback time of 2.8 years. Environmental hotspots in the life cycle of the installation were found to be the production of the PV panels, due to the wafer production, and the mounting system, dominated by the production processes of the aluminium. Comparison to other PV installations identifies the mounting system as the main point of issue in the high-altitude FPV installation, due to a more intensive aluminium use. It was found that the high-altitude FPV installation can generally compete with alternative PV systems in the lowland, with its environmental impacts lying in the range of −45 % and + 15 %, while being largely outperformed by ground-mounted PV installations at high altitude. By implementing measures such as transitioning to renewable energies in the PV panel and mounting system supply chains, as well as reducing aluminium use for the mounting system, FPV systems hold great potential to help meet the increasingly growing demand of renewable energy sources.

Life cycle assessment of a virtual power plant: Evaluating the environmental performance of a system utilising solar photovoltaic generation and batteries

As the world shifts to renewable energy sources to mitigate climate change, virtual power plants (VPPs) have emerged as an innovative solution for integrating distributed renewable generation. This study conducted a comprehensive Life Cycle Assessment (LCA) for a 40 MW VPP in operation in Aotearoa New Zealand, comprising residential solar photovoltaic systems with battery storage. Unlike traditional LCA studies that focus on individual components, this study evaluates the full life cycle impacts of a VPP, offering a holistic view of its environmental implications. Additionally, the study considered electricity fed back to the grid, which avoids grid electricity, or electricity generation from natural gas. The findings reveal an estimated life cycle greenhouse gas (GHG) emissions of 45.3–78.9 gCO2eq/kWh for the VPP, depending on what the surplus electricity replaces. Notably, avoiding natural gas electricity generation by returning surplus electricity to the grid yields a significant credit of −47.3 gCO2eq/kWh. The life cycle GHG emissions of the VPP are highly sensitive to PV generation. If the systems are operated at their maximum potential, the overall emissions reduce by 17.6%. Conversely, when operated at minimum potential, the emissions increase by 23.2%. Additionally, uncertainties in the energy demand to manufacture the battery cells can alter GHG emissions from a 6.7% reduction to a 14.3% increase. This study underscores the complexity of evaluating environmental performances of VPPs and fills a gap in the literature by presenting the potential environmental impacts and benefits of VPPs, shedding light on their role in fostering sustainability with the energy transition.

Energy carrier exports from New Zealand to Japan – A comparative life cycle assessment of hydrogen and ammonia

Hydrogen and ammonia have been promoted as energy carriers for exporting energy from renewables-rich countries. This article presents a life cycle assessment on the export of hydrogen and ammonia from New Zealand to Japan. It encompasses production of hydrogen by electrolysis in New Zealand, conversion to ammonia (where applicable), liquefaction, transport to Japan and combustion in a thermal power station.The life cycle greenhouse gas emissions of energy carriers under present conditions are 0.61 kg CO2eq per kWhe output. This is higher than the carbon intensity of Japan's current electricity generation, so energy carriers provide no climate benefit for electricity generation. The emissions are largely from the supply of electricity for production: for every 1 kWhe output at the power station where the energy carrier is burnt, 5.1 kWhe input is needed for energy carrier production due to energy losses. The findings underscore the importance of decarbonizing the electricity grid in the exporting country if genuine carbon savings are to be realised.