Life Cycle Greenhouse Gas Emissions Research Articles

Office to housing conversion: estimating life cycle environmental and financial performance

Renovating existing building is often touted as having an improved environmental performance as compared to demolition and construction. However, very few studies have quantified the life cycle environmental benefits resulting from such renovations. The aim of this research is to provide a benchmark based on a real and representative case study building to estimate life cycle greenhouse gas emissions and financial costs of redeveloping an office building by considering different scenarios: (1) renovation as an office building; (2) conversion as a residential building; (3) demolition and construction of an office building and (4): demolition and construction of a residential building. Results show that the demolition-construction scenarios are undoubtedly the most environmentally impactful, but the difference between offices and housing is less significant and depends greatly on the assumptions made. On the other hand, from a tax point of view, the demolition-construction scenario is favoured by the real estate industry because it allows for the recovery of VAT in the operation and thus maximizes the value of the real estate asset as well as the financial return. There is also a significant difference between the profitability of a housing and an office project. The latter is favoured by market values. The tendency to favour offices in the European district could be reversed in the current post covid situation and solutions exist to encourage the development of housing projects through office conversion.

Simulation of a rapid compression machine for evaluation of ignition chemistry and soot formation using gasoline/ethanol blends

Due to the projected decline of demand for gasoline in light duty engines and the advent of ethanol as a green fuel, the use of gasoline/ethanol blend fuels in heavy duty applications are being investigated as they are projected to have lower cost and lower lifecycle green house gas (GHG) emissions. In heavy duty engines, the primary mode of combustion is mixing controlled combustion where wide range of mixture conditions (equivalence ratio) exist. Soot emissions of these fuels in richer conditions are not well understood. The goal of this research is to evaluate some commercially available soot modeling codes for the particulate matter emissions from gasoline/ethanol fuel blends, especially at fuel rich conditions. A Rapid Compression Machine (RCM) is modeled in a three-dimensional numerical simulation using CONVERGE computational software using a reduced chemical kinetic mechanism with SAGE chemistry solver and a RANS k-ϵ turbulence model with a sector model including the creviced piston. The creviced piston is used in the experimental setup to reduce boundary layer effects and to maintain a homogeneous core in the reaction cylinder. Computational fluid dynamics simulations are conducted for different gasoline-ethanol fuel blends from E10 (10% ethanol v/v) to E100. The fuel blend is modeled as a surrogate mixture of toluene, iso-octane, n-heptane for gasoline content, and ethanol. The computational results were validated against experimental results using pressure measurements and laser extinction diagnostics. Different soot models are investigated to evaluate their capability of predicting the sooting tendencies of fuel blends, especially in richer conditions experienced during mixing-controlled combustion. The experimental combustion characteristics such as the ignition delay of different blends of fuel are reasonably well predicted. The Particulate Size Mimic (PSM) model accurately predicts the soot generation characteristics of the different fuels, but the Hiroyasu-NSC model falls short in this regard. For accurate prediction of soot with the PSM model, the thermodynamic conditions during combustion must be accurately modeled. While the current computational modeling tools can produce accurate results for the prediction of particulate matter emissions, there is much work to be done in improving our understanding of the underlying fundamental processes.

Calculation of greenhouse gas emissions of urban rail transit systems in China

In China, the total energy consumption and greenhouse gas (GHG) emissions will reach considerable levels based on the current speed of urban rail transit system development. Based on the life-cycle assessment theory, this research constructs an urban rail transit system GHG emission assessment method, calculates emission outputs based on resource inputs from actual investigated data and makes a quantitative analysis of GHG emissions. The results show that in recent years, the GHG emission of urban rail transit construction and operation in China is between 2000 × 104 and 4200 × 104 tonnes of carbon dioxide equivalent (tCO2e) per year. The proportions of the construction and operational phases in this emission are 57 and 43%, respectively. In the construction phase, the GHG emission intensity per unit mileage of shield tunnels and per unit area of stations is about 1.3 × 104 tCO2e/km and 3.71 × 104 tCO2e/ha, respectively. In the operational phase, the GHG emission intensity per unit trip is 0.084 kg carbon dioxide equivalent/passenger-km. The entire life-cycle GHG emission per kilometre of urban rail transit systems is 11.69 × 104 tCO2e (with a service life of 50 years) in China. The construction phase and operation phase generated about 18.73 and 81.27% of this emission, respectively. The preliminary conclusions of this study may help shed light on the emission reduction potential of urban rail transit systems and the emission reduction targets in China.

Mobile Proton-Exchange Membrane Fuel Cell Powered by Diesel Fuel: System Simulation and Life Cycle Analysis

Diesel engine generators used at construction sites generate noise, vibration, and large amounts of pollutant emissions. With the strengthening of emission standards for construction equipment, technologies must be developed to meet new requirements. We proposed and analyzed a mobile proton-exchange membrane fuel cell diesel-powered system to address these issues. The proposed system consisted of an autothermal reformer, a proton-exchange membrane fuel cell, and a balance of plant components. Previous studies on the system have not explored the optimal design and operating condition of the system and have not shown whether the proposed system is superior to the system using the hydrogen-fueled proton-exchange membrane fuel cell system in the life-cycle greenhouse gas emissions point of view. In this study, we clarified system operation characteristics, determined the operational design point, and evaluated system performance and life-cycle greenhouse gas emissions. The system was analyzed by constructing a zero-dimensional simulation model. Several control parameters were varied in parametric studies to determine the operational design point (steam-to-carbon ratio of 2, oxygen-to-carbon ratio of 0.5, fuel utilization factor of 0.85, and heat exchanger effectiveness of 0.85). Considering system performance, the determined design point achieved a 32.3% efficiency. Additionally, we assessed the life-cycle greenhouse gas emissions of the system and compared them with those of an alternative system, which is a hydrogen-fueled proton exchange membrane fuel cell system. It was confirmed that in the United States of America, the proposed system emits 1010.2 g-CO2-eq/kWh of greenhouse gas at a 300 km fuel transportation distance, which is similar to a hydrogen-fueled proton-exchange membrane fuel cell system (1001.1 g-CO2-eq/kWh). The proposed system emits less greenhouse gas emissions than the hydrogen-fueled proton-exchange membrane fuel cell system if the distance from the hydrogen production site to the construction site is more than 318 km. Therefore, for a construction site far from a hydrogen production plant, the proposed diesel-fueled proton-exchange membrane fuel cell system is preferable from both the greenhouse gas emissions and convenience perspectives.

Agent-based model for assessment of multiple circular economy strategies: Quantifying product-service diffusion, circularity, and sustainability

Despite the increasing need for tools to support a circular economy, methods for assessing circularity and environmental consequences in a way that considers dynamic changes in heterogeneous consumer behavior are lacking. Here we propose an agent-based model for assessing seven explicitly-defined product-level circular economy strategies. The model endogenizes bounded rational consumer behavior and interactions related to product acquisition, obsolescence, repair, hibernation, and discharge. Simulation experiments with numerical examples were used to quantify the diffusion of product service systems (e.g., leasing of refurbished products and sharing/rental services), product circularity, and lifecycle greenhouse gas emissions over 30 years. As a result, synergies arising from promotion measures (e.g., pricing, advertisements, and service levels), bottlenecks (e.g., lack of collected products), and rebound effects (e.g., due to new production and transport) were identified. By employing “what-if” analyses, this model provides a means to identify effective interventions in the transition to a net-zero circular economy.

Comparative life cycle greenhouse gas analysis of clean hydrogen pathways: Assessing domestic production and overseas import in South Korea

The development of a Clean Hydrogen Standard based on life-cycle greenhouse gas (GHG) emissions is gaining prominence on the international agenda. Thus, a framework for assessing life-cycle GHG emissions for clean hydrogen pathways is necessary. In this study, the comprehensive datasets and effects of various scenarios encompassing hydrogen production, carriers (liquid hydrogen, ammonia, methylcyclohexane), carbon capture and storage (CCS), target analysis year (2021, 2030) to reflect trends of greening grid electricity and potential import countries on aggregated life-cycle GHG emissions were presented. South Korea was chosen as a case study region, and the low-carbon alternatives were suggested for reducing aggregated emissions to meet the Korean standard (5 kgCO2e/kgH2). First, capturing and storing nearly entire (>90%) CO2 from fossil- and waste-based production pathways is deemed essential. Second, when repurposing the use of hydrogen that was otherwise used internally, applying a penalty for substitution is appropriate, leading to results notably exceeding the standard. Third, for electrolysis-based hydrogen, using renewable or nuclear electricity is essential. Lastly, when hydrogen is imported, in a well-to-point-of-delivery (WtP) perspective, using renewable electricity during hydrogen conversion into a carrier and reusing the produced hydrogen for endothermic reconversion reaction are recommended. By implementing the developed calculation framework to other countries' cases, it was observed that importing hydrogen to regions having scope of WtP or above (e.g., well-to-wheel) might not meet the threshold due to additional emissions from importation processes. Additionally, for hydrogen carriers undergoing the endothermic reconversion, the approach to reduce WtP emissions (reusing produced hydrogen) may conflict with the approach to reduce well-to-gate (WtG) emission (using external fossil-based fuel). The discrepancy highlights the need to set a broader scope of emissions assessment to effectively promote the life-cycle emission reduction efforts of hydrogen importers. This study contributes to the field of clean hydrogen GHG emission assessment, offering a robust database and calculation framework while addressing the effects of greening grid electricity and CCS implementation, proposing low-carbon alternatives and GHG assessment scope to achieve global GHG reduction.

Implications of CO2 Sourcing on the Life-Cycle Greenhouse Gas Emissions and Costs of Algae Biofuels.

Production of algal biomass and its conversion to biofuels are important technological platforms within the larger umbrella of CO2 capture and utilization. This analysis incorporates a life-cycle assessment (LCA) with respect to global warming potential and techno-economic assessment (TEA) of algae biofuels, focusing on the sourcing and delivery of CO2. This analysis evolves past work in this area to include high-purity biogenic CO2, industrial fossil fuel use, fossil power plants, and direct air capture, and uses a Sherwood plot approach to estimate the CO2 capture energy penalty. We also show that allocation or displacement facilitates a more intuitive distinction between biogenic and fossil sources of carbon. Thus, the LCA better reflects the influence of coproduct handling strategies as compared to previous works. The TEA is also strongly influenced by the CO2 concentration in the flue gas. Currently, when CO2 is sourced from large-point sources, the price of biofuels ($4.5-6.5/GGE) may become comparable to fossil diesel. However, as DAC systems become more economical, they may deliver competitive CO2 sources for biofuels in 2050 with a total cost of <$7/GGE. Based on the net emissions and costs, algae biofuels with CO2 sourced from biogenic sources are consistent with a decarbonized economy as of now, with substantial potential for DAC with decreasing costs.

Comparative Evaluation of Total Cost of Ownership of Battery-Electric and Diesel Trucks in India

Whereas battery electric vehicles (BEVs) are on their path to maturity in the light-duty segment, their viability in medium- and heavy-duty applications faces greater skepticism. Furthermore, their higher upfront cost relative to diesel trucks is perceived as even more challenging for less wealthy nations such as India. Here, we undertake a total cost of ownership (TCO) assessment of battery electric trucks (BETs) for four different classes of freight trucks in India using a bottom-up vehicle subsystem level cost estimation. We estimate that, in a scenario in which the incremental upfront cost of BETs relative to a diesel truck is simply the extra cost of the battery pack procured at close to current average international battery pack prices, BETs could have lower TCO, less than 5-year payback, and deliver substantial life cycle cost savings, even without accounting for their environmental benefits. In addition to eliminating tailpipe pollution, they already deliver lower life cycle greenhouse gas emissions based on the current average electricity mix in India. Achieving a scale production that yields lower TCO will, however, require public support over a long maturation phase marked by learning-by-doing externalities and lack of economies of scale when BETs will be costlier. Currently, while there exist multiple types of incentive for light-duty BEVs as well as for cell manufacturing in India, targeted policies for zero emissions trucks are absent; this is a gap that needs to be filled if BETs are to emerge as a serious alternative to diesel trucks in a decade or so.

Waste Activated Sludge-High Rate (WASHR) Treatment Process: A Novel, Economically Viable, and Environmentally Sustainable Method to Co-Treat High-Strength Wastewaters at Municipal Wastewater Treatment Plants.

High-strength wastewaters from a variety of sources, including the food industry, domestic septage, and landfill leachate, are often hauled to municipal wastewater treatment plants (WWTPs) for co-treatment. Due to their high organic loadings, these wastewaters can cause process upsets in both a WWTP's liquid and solids treatment trains and consume organic treatment capacity, leaving less capacity available to service customers in the catchment area. A novel pre-treatment method, the Waste Activated Sludge-High Rate (WASHR) process, is proposed to optimize the co-treatment of high-strength wastewaters. The WASHR process combines the contact stabilization and sequencing batch reactor processes. It utilizes waste activated sludge from a municipal WWTP as its biomass source, allowing for a rapid start-up. Bench-scale treatment trials of winery wastewater confirm the WASHR process can reduce loadings on the downstream WWTP's liquid and solids treatment trains. A case study approach is used to confirm the economic viability and environmental sustainability of the WASHR process compared to direct co-treatment, using life-cycle cost analyses and greenhouse gas emissions estimates.

In-Depth Lifecycle Assessment of Ballasted Railway Track and Slab Track Considering Varying Subsoil Conditions

This study assesses and compares lifecycle (LC) greenhouse gas (GHG) emissions from the two main railway track construction types: ballasted track and slab track. In this study, preexisting soil conditions are considered, as they significantly influence necessary measures during the construction phase for each type. This study is executed for Austrian boundary conditions with speeds up to 250 km/h. The results show that ballasted track is associated with 11–20% lower LC GHG emissions, whereby the variation in relative emission reduction is associated with additional soil reinforcement treatments due to varying preexisting soil conditions. Poor preexisting soil conditions increase LC GHG emissions by 26%, underlying the necessity to integrate this parameter into the lifecycle assessment of railway track. In contrast to the higher service life of slab track construction, this type amounts to higher masses of concrete and demands more extensive measures for soil enhancement due to the higher stiffness of the track panel. Only in tunnel areas does slab track cause lower GHG emissions since soil reinforcements are not necessary due to an existing concrete base layer after tunnel construction. For both construction types, over 80% of the GHG emissions stem from material production. Hence, circular economy as well as innovations within steel and concrete production processes hold significant potential for reducing GHG emissions.

Tradeoffs in life cycle water use and greenhouse gas emissions of hydrogen production pathways

Hydrogen has been promoted as a key component of global decarbonization efforts, with various past studies estimating carbon emissions for several production pathways, but little past work has considered its water resource needs. This life cycle analysis considers hydrogen production on a per-kilogram basis for 11 pathways, fossil and non-fossil. It also includes impacts of treating water to the required quality for hydrogen production. Greenhouse gas emissions results were in a range of −15 to +31 kg CO2e/kg H2 produced. Water consumption varied more widely, from about 7 to 55 kg water/kg H2 for fossil-based pathways and 530 to 3400 kg water/kg H2 for biomass-based pathways. Electrolysis with various renewable electricity scenarios were also modeled. Overall, there are challenging tradeoffs to be navigated to achieve a low carbon and water footprint in hydrogen economy.

Life cycle greenhouse gases emissions from high-speed rail in Spain: The case of the Madrid – Toledo line

The Madrid – Toledo high-speed rail (HSR) line is 74.5 km long, has an average speed of 140 km/h and a maximum speed of 270 km/h. It averages almost 104 million passenger-kilometres travelled and has a utilisation rate (passengers per available seats) of 0.75 as of 2019. This study analyses the life cycle greenhouse gases (GHG) emissions of the Madrid – Toledo HSR line using the life cycle assessment methodology, taking into consideration the stages of construction, maintenance and operation for the infrastructure, as well as the manufacturing, maintenance and operation stages for trains. The most significant stage is infrastructure construction, which accounts for an average 75 % emissions, followed by train operation, with an average 18.2 %.The results highlight several environmental benefits of the deployment of the line, as after 40 years of operation there will be an average 21 % reduction in GHG emissions for passenger mobility between Madrid and Toledo compared to the case where no HSR line was built. Moreover, the line's GHG emissions are offset between 19 and 23 years after starting operation, mainly due to the emissions avoided by passengers switching to a carbon-friendlier mode of transportation in terms of operation, and the adoption of a 100 % renewable energy mix for the operation of trains since 2019.These findings point to opportunities for improving the life cycle GHG emissions of high-speed rail lines, such as increasing the occupancy of trains by applying new pricing policies and investing in intermodal infrastructures to achieve higher modal shift rates, promoting proximity criteria for the supply of raw materials during the infrastructure construction stage and improving the maintenance stage to prolong the lifetime of the infrastructure, thus deferring life cycle emissions for longer.

Improving mechanical and life cycle environmental performances of recycled CFRP automotive component by fibre architecture preservation

Recycled carbon fibre reinforced polymer (rCFRP) is attracting interest for automotive applications but has reduced mechanical properties due to a loss of intact fibre architecture. This study investigates the effects of fibre architecture preservation during recycling of carbon fibres on the mechanical and life cycle environmental performances of rCFRP applied to a vehicle roof panel. Results show that rCFRPs with preserved unidirectional and woven fibre architectures have average flexural properties at least 4 times higher than those of current rCFRP with unpreserved fibre architecture. A hypothetical rCFRP roof panel with preserved plain woven rCF reduces the life cycle greenhouse gas emissions by 11% and 23% compared to the current rCFRP, respectively, when used in gasoline vehicle and battery electric vehicle. This paper demonstrates that the recycling approach with fibre architecture preservation offers great opportunities to improve the mechanical and environmental performances of rCFRP for use in the automotive industry.

Comparing Life-Cycle Emissions of Biofuels for Marine Applications: Hydrothermal Liquefaction of Wet Wastes, Pyrolysis of Wood, Fischer-Tropsch Synthesis of Landfill Gas, and Solvolysis of Wood.

Recent restrictions on marine fuel sulfur content and a heightened regulatory focus on maritime decarbonization are driving the deployment of low-carbon and low-sulfur alternative fuels for maritime transport. In this study, we quantified the life-cycle greenhouse gas and sulfur oxide emissions of several novel marine biofuel candidates and benchmarked the results against the emissions reduction targets set by the International Maritime Organization. A total of 11 biofuel pathways via four conversion processes are considered, including (1) biocrudes derived from hydrothermal liquefaction of wastewater sludge and manure, (2) bio-oils from catalytic fast pyrolysis of woody biomass, (3) diesel via Fischer-Tropsch synthesis of landfill gas, and (4) lignin ethanol oil from reductive catalytic fractionation of poplar. Our analysis reveals that marine biofuels' life-cycle greenhouse gas emissions range from -60 to 56 gCO2e MJ-1, representing a 41-163% reduction compared with conventional low-sulfur fuel oil, thus demonstrating a considerable potential for decarbonizing the maritime sector. Due to the net-negative carbon emissions from their life cycles, all waste-based pathways showed over 100% greenhouse gas reduction potential with respect to low-sulfur fuel oil. However, while most biofuel feedstocks have a naturally occurring low-sulfur content, the waste feedstocks considered here have higher sulfur content, requiring hydrotreating prior to use as a marine fuel. Combining the break-even price estimates from a published techno-economic analysis, which was performed concurrently with this study, the marginal greenhouse gas abatement cost was estimated to range from -$120 to $370 tCO2e-1 across the pathways considered. Lower marginal greenhouse gas abatement costs were associated with waste-based pathways, while higher marginal greenhouse gas abatement costs were associated with the other biomass-based pathways. Except for lignin ethanol oil, all candidates show the potential to be competitive with a carbon credit of $200 tCO2e-1 in 2016 dollars, which is within the range of prices recently received in connection with California's low-carbon fuel standard.

Life-Cycle Greenhouse Gas (GHG) Emissions Calculation for Urban Rail Transit Systems: The Case of Pernambuco Metro

In recent years, the issue of climate change has gained significant attention and become a focal point of discussion in various sectors of civil society. Governments, individuals, and scientists worldwide are increasingly concerned about the observed changes in climate patterns, often attributed to the rising levels of greenhouse gases. In this context, the main objective of this study is to assess the greenhouse gas emissions associated with the railway system in the state of Pernambuco, Brazil, and compare them with other national case studies, aiming to obtain greenhouse gas emission parameters specific to the railway system and propose mitigation models to address this environmental impact in the air. To achieve this goal, a comprehensive life cycle assessment (LCA) methodology was employed to examine the life cycle of the Pernambuco Metro. This involved conducting an inventory of resource inputs and emissions using actual observed data. Additionally, a comparative analysis of greenhouse gas emissions across different urban rail transport systems is presented to provide valuable contextual insights. The study findings reveal that the total greenhouse gas emissions from the Pernambuco rail system amount to 6170.54 t CO2e. Considering a projected total service life of 50 years, the estimated greenhouse gas emissions for the entire life cycle of the system’s operation and maintenance reach 308,550 t CO2e. The interdisciplinary nature of this research highlights the significance of studying the atmospheric effects of the Pernambuco railway system as a crucial parameter for designing strategies and technologies aimed at reducing air pollution within the region. Through quantifying and analyzing the greenhouse gas emissions of the Pernambuco rail system, this study provides valuable insights that contribute to addressing concerns related to climate change and promoting sustainable practices. It underscores the importance of developing effective strategies to mitigate air pollution and facilitates informed decision-making for the future of urban transportation systems.

Linear programming approach to design bio-based plastics strategies for Japan: Integration of material characteristics, product applications, and end of life options

There is a growing interest in bio-based plastics for mitigating climate change; however, it remains unclear as to which products should be produced using bio-based plastics and how such plastics should be disposed of to minimize their environmental impact. To investigate the degree to which bio-based plastics can be applied toward the mitigation of climate change based on material characteristics, product applications, and end of life (EoL) options, we developed a linear-programming-based model to represent a plastic system of nine types of fossil-based plastics and 12 types of bio-based plastics in Japan. We found that introducing bio-based plastics could reduce life cycle greenhouse gas (LCGHG) emissions, provided that an appropriate EoL is coupled. Specifically, the ‘drop-in’ plastics were dominantly selected with feedstock recycling when only material property was constrained, and the LCGHG emissions from the system was −15.5 million t-CO2eq/year.

Technical, economic and environmental analysis of solar thermochemical production of drop-in fuels

This study analyzes the technical performance, costs and life-cycle greenhouse gas (GHG) emissions of the production of various fuels using air-captured water and CO2, and concentrated solar energy as the source of high-temperature process heat. The solar thermochemical fuel production pathway utilizes a ceria-based redox cycle for splitting water and CO2 to syngas – a tailored mixture of H2 and CO – which in turn is further converted to liquid hydrocarbon fuels. The cycle is driven by concentrated solar heat and supplemented by a high-temperature thermal energy storage for round-the-clock continuous operation. The study examines three locations with high direct normal irradiation using a baseline heliostat field reflective area of 1 km2 for the production of six fuels, i.e. jet fuel and diesel via Fischer-Tropsch, methanol, gasoline via methanol, dimethyl ether, and hydrogen. Two scenarios are considered: near-term future by the year 2030 and long-term future beyond 2030.In the near-term future in Sierra Gorda (Chile), the minimum fuel selling price is estimated at around 76 €/GJ (2.5 €/L) for jet fuel and diesel, 65 €/GJ for methanol, gasoline (via methanol) and dimethyl ether (DME), and 42 €/GJ for hydrogen (excluding liquefaction). In the long-term future, with advancements in solar receiver, redox reactor, high-temperature heat recovery and direct air capture technologies, the industrial-scale plant could achieve a solar-to-fuel efficiency up to 13–19 %, depending on the target fuel, resulting in a minimum fuel selling price of 16–38 €/GJ (0.6–1.3 €/L) for jet fuel and diesel, and 14–32 €/GJ for methanol, gasoline, and DME, making these fuels synthesized from sunlight and air cost-competitive vis-à-vis e-fuels. To produce the same fuels in Tabernas (Spain) and Ouarzazate (Morocco) as in Sierra Gorda, the production cost would increase by 22–33 %. Greenhouse gas savings can be over 80 % already in the near-term future.

Life Cycle Greenhouse Gas Emissions of Brazilian Sugar Cane Ethanol Evaluated with the GREET Model Using Data Submitted to RenovaBio.

Brazil is the second-largest ethanol producer in the world, primarily using sugar cane as feedstock. To foster biofuel production, the Brazilian government implemented a national biofuel policy, known as RenovaBio, in which greenhouse gas (GHG) emission reduction credits are provided to biofuel producers based on the carbon intensities (CI) of the fuels they produce. In this study, we configured the GREET model to evaluate life cycle GHG emissions of Brazilian sugar cane ethanol, using data from 67 individual sugar cane mills submitted to RenovaBio in 2019/2020. The average CI per megajoule of sugar cane ethanol produced in Brazil for use in the U.S. was estimated to be 35.2 g of CO2 equivalent, a 62% reduction from U.S. petroleum gasoline blendstock without considering the impacts of land use change. The three major GHG sources were on-field N2O emissions (24.3%), sugar cane farming energy use (24.2%), and sugar cane ethanol transport (19.3%). With the probability density functions for key input parameters derived from individual mill data, we performed stochastic simulations with the GREET model to estimate the variations in sugar cane ethanol CI and confirmed that despite the larger variations in sugar cane ethanol CI, the fuel provided a robust GHG reduction benefit compared to gasoline blendstock.

Recycling of Plastics as a Strategy to Reduce Life Cycle GHG Emission, Microplastics and Resource Depletion

Plastic waste is the most challenging type of waste because its generation rate (consumption rate) is high, and the current recycling rate is low. The increase in the production and disposal of plastics has led to significant environmental problems including greenhouse gas (GHG) emissions, microplastic pollution, and resource depletion. The study aimed at quantifying the potential environmental effects reduction achieved by recycling the most widely consumed polymers. One approach to establishing a circular economy for plastics is recycling. Plastic recycling as a strategy to reduce life cycle GHG emissions, microplastic emissions, and resource depletion was investigated. Life cycle assessment methodology was employed, considering cradle-to-gate as a system boundary. The results showed that recycling can significantly reduce life cycle GHG emissions and resource depletion. Replacing the virgin material with recycled material reduces the emission to −67 MtCO2e. Recycling could have saved 56.8 million microplastic emissions per year. However, mechanical recycling, which is commercialised nowadays, contributed to an increase in microplastics as much as 2.4 × 109 million particles per year. Recycling will also save about 50 million tonnes of resources from depletion worldwide by recycling around 20 Mt plastics. However, microplastic emissions reduction in the present scenario of mechanical recycling is not possible unless other mechanisms to capture the emitted microplastics are introduced or other recycling methods, such as chemical recycling, are employed.

Life cycle greenhouse gas emissions for irrigated corn production in the U.S. great plains

Agricultural management practices improve crop yields to satisfy food demand of the growing population. However, these activities can have negative consequences, including the release of greenhouse gas (GHG) emissions that contribute to global climate change. To mitigate this global environmental problem, the management practices that contribute the most to system GHG emissions should be identified and targeted to mitigate emissions. Accordingly, we estimated the cradle-to-product GHG emissions of irrigated corn production under various farmer-selected scenarios at an experimental testing field in the semi-arid U.S. Great Plains. We applied a carbon footprint approach to quantify life cycle GHG emissions associated with pre-field (e.g., energy production, fertilizer production) and in-field (e.g., groundwater pumping, fertilizer application) activities within fourteen scenarios in the 2020 Oklahoma Testing Ag Performance Solutions (TAPS) sprinkler corn competition. We determined that 63% of the total GHG emission from corn production was associated with in-field activities and that agricultural soil emissions were the overall driving factor. Soil biochemical processes within agricultural soils were expected to contribute an average of 89 ± 18 g CO2-eq kg−1 corn of the total 271 ± 46 g CO2-eq kg−1 corn estimated from these systems. On-site natural gas combustion for agricultural groundwater pumping, pre-field fertilizer production, and pre-field energy production for groundwater pumping were the next most influential parameters on total GHG emissions. Diesel fuel, seed, and herbicide production had insignificant contributions to total GHG emissions from corn production. The model was most sensitive to the modeled GHG emissions from agricultural soil, which had significant uncertainty in the emission factor. Therefore, future efforts should target field measurements to better predict the contribution of direct soil emissions to total GHG emissions, particularly under different managements. In addition, identifying the optimal application rate of irrigation water and fertilizer will help to decrease GHG emissions from groundwater irrigated crops.