Total Life Cycle Greenhouse Gas Research Articles

Assessing the effectiveness of building retrofits in reducing GHG emissions: A Canadian school case study

This paper investigates the impact of energy retrofits on life cycle greenhouse gas (GHG) emissions across different electricity grid profiles in Montreal, Ottawa, and Halifax, using an existing school building as a case study. Using DesignBuilder for energy simulations and OneClick LCA for GHG emissions estimation, this study evaluates whether the reduction in the operational emission achieved by energy savings from retrofits can outweigh the increased embodied emissions from new envelope materials and equipment. In Montreal and Ottawa, where electricity is mainly generated from renewables and non-fossil fuels, retrofits involving electric heating and envelope improvements could decrease life cycle GHG emissions by up to 75 %. However, if the building initially used electric heating, the retrofits led to an increase in life cycle carbon emissions by 170 % in Montreal and 56 % in Ottawa, respectively, due to the embodied emissions of retrofit materials and equipment. In Halifax, where the electricity grid relies heavily on fossil fuels, all retrofit scenarios showed a positive impact on GHG reductions. Enhancing the building envelope and transitioning from natural gas to electric heating slightly reduced total emissions by 4 %, but retaining natural gas heating decreased the total life cycle GHG emissions by 27 %. This study emphasizes the importance of a comprehensive life cycle assessment in developing policies for achieving carbon neutrality. It demonstrates that the effectiveness of retrofits in reducing GHG emissions significantly depends on the local energy grid, suggesting tailored approaches based on regional energy profiles to optimize emission reductions and energy efficiency.

ICT sector electricity consumption and greenhouse gas emissions – 2020 outcome

The Information and Communication Technology (ICT) sector has gained much attention in the discussions on climate change, as it could impact global emissions both positively and negatively. The objective of the present study is to provide estimates for the 2020 use stage electricity consumption and ICT sector's total lifecycle greenhouse gas (GHG) emissions divided in three main parts: user devices including internet-of-things, networks and data centers. The study builds on a high number of data sources including measured and reported data from 150 companies that is estimated to cover about 80% of network subscriptions, about 55% of data center electricity, and about 35% of upstream GHG emissions. To understand the development, the results are put into the perspective of earlier studies. In conclusion, the ICT sector used about 4% of the global electricity in the use stage and represented about 1.4% of the global GHG emissions in 2020. The use stage electricity consumption and the total GHG emissions have increased since 2015, but the impact per subscription has decreased. The user devices accounted for over half of all GHG emissions, with equal parts relating to use stage and other lifecycle stages. For networks and data centers, the use stage GHG emissions are dominating. The electricity consumption and GHG emissions are also estimated for the closely related areas Entertainment and Media (including e.g., TVs), paper media, and cryptocurrencies.

Life cycle greenhouse gas emissions from five contrasting rice production systems in the tropics

Carbon Footprints (CFs) quantification of major rice production systems (RPSs) is a prerequisite for chalking out strategies for climate change mitigation in agriculture. Total life cycle greenhouse gas emissions (LC-GHGs) from production to consumption could provide precise CFs for RPSs. Therefore, to address this issue, we assessed all the three segments of LC-GHGs for five major contrasting RPSs in India, such as, aerobic rice (AR), shallow lowland rice (SLR), system of rice intensification (SRI), deep water rice (DWR), and zero-tilled direct-seeded rice (ZTR)) to determine the CFs. The CF was found to be lowest in ZTR but the LC-GHGs were found to be lowest in case of AR, which recorded higher CF than that of ZTR. So, for short-term reduction of greenhouse gas (GHG) emission, aerobic rice (AR) is a good option. However, ZTR with lowest CF among all, could be prompted with incentives for long-term strategy. Among the segmental LC-GHGs, the ‘on-farm’ emission contributed less compared to the other two segments. The post-harvest to consumption segment contributed the maximum (54%–69%) of total LC-GHGs, followed by ‘cradle-to-farm’ (21%–27%), and on-farm operations (11%–23%). These findings suggest that post-harvest components that contribute maximum GHG emissions must be tackled scientifically with proactive policy initiatives. However, the data on this segment is limited and scattered. Therefore, real-time assessment of GHG emissions during post-harvest activities and transportation of inputs from cradle to farm require more precise quantification. Although the CF in SRI was found to be more, yet this system has the potential to fetch higher yields and better soil carbon storage. So, SRI could be encouraged for food security and long-term sustainability perspectives by reducing greenhouse gas emissions by 3-to-4 times.

Total CO2-equivalent life-cycle emissions from commercially available passenger cars

The international passenger car market is undergoing a transition from vehicles with internal combustion engines to hybrid and fully electrified vehicles to reduce the climate impact of the transportation sector. To emphasize the importance of this needed change, this paper provides holistic comparisons of the total life-cycle greenhouse gas (GHG) emissions produced by a wide selection of commercially available passenger cars with different powertrains and energy sources. Simple analytical models are used to quantify the total life-cycle GHG emissions in terms of CO2-equivalent values relative to the vehicle curb weight and the peak motor power. The production, utilization and recycling emissions are separately quantified based on the latest reviewed emission coefficient values. In total 790 different vehicle variants are considered. The results show that Battery Electric Vehicles have the highest production emissions. For example, the additional production emissions of a Tesla Model 3 Standard Plus approximately correspond to the driving emissions of a Volkwagen Passat 2.0 TSI after 18 000km. Nonetheless, it is shown that conventional gasoline and diesel vehicles emit the highest amount of total life-cycle GHGs in comparison to vehicles powered by other available energy resources. When using green electricity, plug-in hybrid electric and fully electric vehicles can reduce the total life-cycle emission in comparison to combustion engine vehicles by 73% and 89%, respectively. A similar emission reduction is achieved by biogas powered vehicles (81%). Fuel cell vehicles approximately reduce the GHG emission to a similar extent as electric vehicles (charged with conventional electricity) when using commercially available gray hydrogen (60%).

Life Cycle GHG Emissions of Residential Buildings in Humid Subtropical and Tropical Climates: Systematic Review and Analysis

Improving the environmental life cycle performance of buildings by focusing on the reduction of greenhouse gas (GHG) emissions along the building life cycle is considered a crucial step in achieving global climate targets. This paper provides a systematic review and analysis of 75 residential case studies in humid subtropical and tropical climates. The study investigates GHG emissions across the building life cycle, i.e., it analyses both embodied and operational GHG emissions. Furthermore, the influence of various parameters, such as building location, typology, construction materials and energy performance, as well as methodological aspects are investigated. Through comparative analysis, the study identifies promising design strategies for reducing life cycle-related GHG emissions of buildings operating in subtropical and tropical climate zones. The results show that life cycle GHG emissions in the analysed studies are mostly dominated by operational emissions and are the highest for energy-intensive multi-family buildings. Buildings following low or net-zero energy performance targets show potential reductions of 50–80% for total life cycle GHG emissions, compared to buildings with conventional energy performance. Implementation of on-site photovoltaic (PV) systems provides the highest reduction potential for both operational and total life cycle GHG emissions, with potential reductions of 92% to 100% and 48% to 66%, respectively. Strategies related to increased use of timber and other bio-based materials present the highest potential for reduction of embodied GHG emissions, with reductions of 9% to 73%.

Multi-objective optimisation of a seasonal solar thermal energy storage system for space heating in cold climate

Seasonal solar thermal energy storage (SSTES) system is a promising technology to minimise greenhouse gas emissions (GHGE) by harnessing solar energy for space heating applications. The SSTES system in this study includes double U-tube borehole heat exchanger, ground-coupled heat pump and evacuated tube solar collectors. The aim of this investigation is to optimise the design variables of a SSTES system for space heating in cold climate locations. Six cold climate locations were studied namely: Lukla (Nepal), Dras (India), Sivas (Turkey), Harbin (China), Ulaanbaatar (Mongolia), and Verkhoyansk (Russia). The optimisation variables considered are the total solar collector area and total borehole length. There are three separate optimisation investigations: two single-objective and one multi-objective for the SSTES system. The first investigation is to minimise total life cycle greenhouse gas emissions and the second investigation is to minimise total life cycle cost included cost of GHGE. The third investigation is to minimise both life cycle cost of SSTES system and cost of GHGE (multi objectives). The simulation model was developed using TRNSYS 17 and the Multi-Objective Building Optimisation (MOBO) tool was applied for optimisations. The optimal set of design variables and the corresponding value of the objective function were determined for each single-objective optimisation investigation. Pareto front for each location was also identified for the multi-objective optimisation investigation. The technical and financial performance were also analysed and presented.

Life cycle greenhouse gas emissions of multi-pathways natural gas vehicles in china considering methane leakage

Natural gas has been promoted rapidly recent years to substitute traditional vehicle fuels. However, methane leakages in the natural gas supply chains make it difficult to ascertain whether it can reduce greenhouse gas emissions when used as a transport fuel. This paper characterizes the natural gas supply chains and their segments involved, estimates the venting and fugitive leakages from natural gas supply chains, decides the distribution among segments and further integrates it with life cycle analysis on natural gas fueled vehicles. Domestic natural gas supply chain turns out to be the dominant methane emitter, accounting for 67% of total methane leakages from natural gas supply chains. Transportation segments contribute 42–86% of the total methane leakages in each supply chain, which is the greatest contribution among all the segments. Life cycle analysis on private passenger vehicles, transit buses and heavy-duty trucks show that compressed natural gas and liquefied natural gas bring approximately 11–17% and 9–15% greenhouse gas emission reduction compared to traditional fossil fuels, even considering methane leaks in the natural gas supply chains. Methane leakages from natural gas supply chains account for approximately 2% of the total life cycle greenhouse gas emissions of natural gas vehicles. The results ascertain the low-carbon attribute of natural gas, and greater efforts should be exerted to promote natural gas vehicles to help reduce greenhouse gas emissions from on-road transportation.

Statistical life cycle assessment of residential buildings in a temperate climate of northern part of Europe

Nowadays, with the new technology, the explosion of new products and the implementation of the new construction rules, it is important to evaluate the effect of the strong human pressure on nature. Thus, the analysis of the life cycle of a product (i.e., building) makes it possible to evaluate its main environmental impacts (energy demand, greenhouse gas emissions, product waste, water consumption, etc.) from raw materials manufacturing to its end of life (demolition). The purpose of this research is to carryout a meticulous statistical analysis aimed to better understand and to discern better the impact of sustainable buildings and old buildings on the environment. In addition, this research identifies the main elements that affect the environment during the construction, operation, renovation, and demolition of buildings.59 residences were analyzed (29 durable residences and 30 old residences), distributed in two districts of the Liege city. Several software tools were used (IBM SPSS statistical, ALCYONE, COMFIE-PLEIADES, and nova-EQUER) to statistically evaluate the 12 environmental impacts considered in this study. The results showed that the impacts of sustainable buildings and old buildings on the environment are very significant. Despite that, it is difficult to identify a clear difference between the environmentalimpact from old and sustainable buildings. The total lifecycle greenhouse gas (LCGHG) and energy of the whole the residential buildings represents 17.225 ktCO2-e and 362.8 TJ, respectively, over 100 years. The building operation phase (or use phase) consume significant amount of life cycle energy (from 81.0 to 94.3%), but also, the largest contribution to the life cycle greenhouse gas (between 75.6% and 91.3%).

Environmental and Economic Optimization of Algal Biofuel Supply Chain with Multiple Technological Pathways

This article optimizes the design and configuration of algal biofuel supply chain networks (SCN) under economic and environmental objectives. Minimization of the total supply chain cost and the total life cycle greenhouse gas emission are the economic and environmental objectives, respectively. The SCN has been modeled by a multiobjective mixed integer linear programming approach which incorporates multiple production pathways and time periods, seasonality factors, water evaporation, recycling opportunities, and other major traits of the algal biofuel SCN. The model determines the optimal strategic and tactical level decisions of all SCN echelons. A fuzzy solution-based e-constraint method has been utilized to obtain Pareto-optimal solutions that illustrate the trade-off between economic and environmental objectives. The performance of the model has been assessed in a case study carried out in seven states of the U.S which intends to develop the algal biofuel SCN from the year 2018 to the year 2024. Essen...

Life cycle greenhouse gas emission reduction potential of battery electric vehicle

Abstract Purpose This study uses the life cycle assessment (LCA) method to calculate and compare the life cycle greenhouse gas (GHG) emissions from battery electric vehicles (BEVs) and conventional gasoline internal combustion engine vehicles (ICEVs) in 2010, 2014 and 2020 under different scenarios, including different electricity mixes, electricity generation technologies and combined heat and power (CHP) scales, as well as discusses the GHG emission reduction potential of BEVs throughout their life cycle. Methods The LCA system boundaries, including the vehicle cycle and the fuel cycle, are examined in accordance with the ISO 14040/14044 standards. The China Automotive Life Cycle Database (CALCD), which is the first and primary life cycle database of the China automotive industry, was used. The compositional data for the vehicle components and the battery material were obtained from the GREET2 2017 model. Results and discussion As the electricity mix is optimized, the electricity generation technology is advanced, and the CHP scale is increased from 2010 to 2020, the total life cycle GHG reduction potential of BEVs will gradually improve, reaching 13.4% in 2020, relative to ICEVs. Conclusions The sensitivity analysis shows that the GHG emissions from electricity, the percentage of fossil fuel in the electricity mix and the electricity consumption of the BEV during use are important parameters influencing the GHG emission reduction potential of BEVs. By adjusting the electricity mix, advancing electricity generation technologies and increasing the CHP scale, the GHG emission reduction potential of BEVs can be improved.

A life cycle assessment of oxymethylene ether synthesis from biomass-derived syngas as a diesel additive

The life cycle energy consumption and greenhouse gas (GHG) emission performances of forest biomass-derived oxymethylene ether (OME) synthesis used as a diesel additive are analyzed in this study. OME, a new alternative liquid fuel, has great miscibility with conventional fuels like diesel. OME can reduce combustion emissions significantly when used as a diesel additive without any modification to the engine. A data-intensive spreadsheet-based life cycle assessment (LCA) model was developed for OME synthesis from woodchips derived from two different kinds of forest biomass, whole tree and forest residue. Woodchip harvesting, chip transportation, chemical synthesis of OME from biomass-derived syngas, OME transportation to blending, and vehicle combustion of this transportation fuel were considered in the system boundary. The results show that the whole tree pathway produces 27 g CO2eq/MJ of OME, whereas the forest residue pathway produces 18 g CO2eq/MJ of OME over 20 years of plant life. The difference is mainly due to some emissions-intensive operations involved in biomass harvesting and biomass transportation such as skidding, road construction, etc., in the whole tree pathway. Also, vehicle combustion was found to be the most GHG-intensive unit for both pathways. OME combustion in a vehicle accounts for about 77% and 83% of the total life cycle GHG emissions for the whole tree and forest residue pathways, respectively. This study also compares the diesel life cycle emission numbers with the life cycle emissions of OME derived from forest biomass, and it was observed that GHG emissions can be reduced by 20–21% and soot (black carbon) emissions can be reduced by 30% using a 10% OME blended diesel as a transportation fuel compared with conventional diesel.

Life-cycle greenhouse gas emission and energy use of bioethanol produced from corn stover in China: Current perspectives and future prospectives

In this study, a life cycle analysis (LCA) of bioethanol production from corn stover is carried out under Chinese context. Three scenarios were developed and assessed based on current and future technology levels of the ethanol conversion process. Well-to-pump (WTP) and well-to-wheels (WTW) results are presented in this paper via functional units of 1 MJ of ethanol produced, 1 MJ of E100 produced and used, and 1 km of distance driven by a light-duty vehicle on E10 fuel, respectively. It was calculated that for 1 MJ of E100, the WTW Greenhouse gas (GHG) emission reduction relative to gasoline reaches 52%–55%, and the savings of fossil fuel and petroleum fuel reach 72%–76% and 74%–85%, respectively. For 1 MJ of ethanol produced, GHG emissions occurred in ethanol conversion process account for 51%–55%, and the contribution of chemical inputs reaches 36%–37% of the total life cycle GHG emissions. Furthermore, the life cycle results were found to be highly sensitive to allocation methods.

Life Cycle Greenhouse Gas Emissions from Uranium Mining and Milling in Canada.

Life cycle greenhouse gas (GHG) emissions from the production of nuclear power (in g CO2e/kWh) are uncertain due partly to a paucity of data on emissions from individual phases of the nuclear fuel cycle. Here, we present the first comprehensive life cycle assessment of GHG emissions produced from the mining and milling of uranium in Canada. The study includes data from 2006-2013 for two uranium mine-mill operations in northern Saskatchewan (SK) and data from 1995-2010 for a third SK mine-mill operation. The mine-mill operations were determined to have GHG emissions intensities of 81, 64, and 34 kg CO2e/kg U3O8 at average ore grades of 0.74%, 1.54%, and 4.53% U3O8, respectively. The production-weighted average GHG emission intensity is 42 kg CO2e/kg U3O8 at an average ore grade of 3.81% U3O8. The production-weighted average GHG emission intensity drops to 24 kg CO2e/kg U3O8 when the local hydroelectric GHG emission factor (7.2 g CO2e/kWh) is substituted for the SK grid-average electricity GHG emission factor (768 g CO2e/kWh). This results in Canadian uranium mining-milling contributing only 1.1 g CO2e/kWh to total life cycle GHG emissions from the nuclear fuel cycle (0.7 g CO2e/kWh using the local hydroelectric emission factor).

A mathematical model formulation for the design of an integrated biodiesel-petroleum diesel blends system

This paper addresses the strategic planning of an IBSC (integrated biofuel supply chain) using total annualized cost and total life cycle GHG (green house gas) emissions as economic and environmental criteria respectively. The IBSC for an extended planning horizon H (e.g. 10 years) is considered and horizon H is further subdivided into a set of discrete time intervals. For each of these subintervals the diesel and the biodiesel fuel consumption can be varied according to a predetermined value. A mixed-integer linear programming model of biodiesel production that takes into account infrastructure compatibility, demand distribution, size and location of biorefineries using the available biomass and carbon tax data is proposed. An important aspect of the proposed model is the inclusion of crop rotation conditions to assure the supply of biological feedstock. The price of biodiesel and any byproducts produced are included in the model. Inputs to the model are the quantity of biological feedstock, the cost of biomass transportation, as well as inventory and processing costs. The proposed model is illustrated in Part 2 of this work with an example of Bulgarian economy for planning period 2010 to 2020 when the objectives of the Renewable Energy Directive 28/2009/EC will be achieved.

Impacts of Vehicle Weight Reduction via Material Substitution on Life-Cycle Greenhouse Gas Emissions.

This study examines the vehicle-cycle and vehicle total life-cycle impacts of substituting lightweight materials into vehicles. We determine part-based greenhouse gas (GHG) emission ratios by collecting material substitution data and evaluating that alongside known mass-based GHG ratios (using and updating Argonne National Laboratory's GREET model) associated with material pair substitutions. Several vehicle parts are lightweighted via material substitution, using substitution ratios from a U.S. Department of Energy report, to determine GHG emissions. We then examine fuel-cycle GHG reductions from lightweighting. The fuel reduction value methodology is applied using FRV estimates of 0.15-0.25, and 0.25-0.5 L/(100km·100 kg), with and without powertrain adjustments, respectively. GHG breakeven values are derived for both driving distance and material substitution ratio. While material substitution can reduce vehicle weight, it often increases vehicle-cycle GHGs. It is likely that replacing steel (the dominant vehicle material) with wrought aluminum, carbon fiber reinforced plastic (CRFP), or magnesium will increase vehicle-cycle GHGs. However, lifetime fuel economy benefits often outweigh the vehicle-cycle, resulting in a net total life-cycle GHG benefit. This is the case for steel replaced by wrought aluminum in all assumed cases, and for CFRP and magnesium except for high substitution ratio and low FRV.

Life-cycle greenhouse gas emissions associated with a highway reconstruction: a New Jersey case study

A comprehensive greenhouse gas (GHG) life-cycle assessment was conducted for a large highway reconstruction project in New Jersey. The GASCAP model was used to determine the total life-cycle GHG emissions associated with the materials used, construction equipment, mobilization of resources for the project, traffic disruption during construction, and materials used for life-cycle maintenance. The focus of the case study was to determine the relative share of these various components, as well as the importance of accounting for non-CO2 GHG emissions. Results suggest that non-CO2 emissions are substantial enough that they should be included and that various smaller material components, not just those associated with materials in the pavement should also be included. For this specific case-study, traffic disruption was a minor component of total emissions, though this result will differ depending on project and road network details. GHG emissions associated with this reconstruction project account for about 20% of the total emissions expected to be generated from traffic using the highway over a 50 year lifetime.

Forest carbon accounting methods and the consequences of forest bioenergy for national greenhouse gas emissions inventories

While bioenergy plays a key role in strategies for increasing renewable energy deployment, studies assessing greenhouse gas (GHG) emissions from forest bioenergy systems have identified a potential trade-off of the system with forest carbon stocks. Of particular importance to national GHG inventories is how trade-offs between forest carbon stocks and bioenergy production are accounted for within the Agriculture, Forestry and Other Land Use (AFOLU) sector under current and future international climate change mitigation agreements. Through a case study of electricity produced using wood pellets from harvested forest stands in Ontario, Canada, this study assesses the implications of forest carbon accounting approaches on net emissions attributable to pellets produced for domestic use or export. Particular emphasis is placed on the Forest Management Reference Level (FMRL) method, as it will be employed by most Annex I nations in the next Kyoto Protocol Commitment Period. While bioenergy production is found to reduce forest carbon sequestration, under the FMRL approach this trade-off may not be accounted for and thus not incur an accountable AFOLU-related emission, provided that total forest harvest remains at or below that defined under the FMRL baseline. In contrast, accounting for forest carbon trade-offs associated with harvest for bioenergy results in an increase in net GHG emissions (AFOLU and life cycle emissions) lasting 37 or 90 years (if displacing coal or natural gas combined cycle generation, respectively). AFOLU emissions calculated using the Gross-Net approach are dominated by legacy effects of past management and natural disturbance, indicating near-term net forest carbon increase but longer-term reduction in forest carbon stocks. Export of wood pellets to EU markets does not greatly affect the total life cycle GHG emissions of wood pellets. However, pellet exporting countries risk creating a considerable GHG emissions burden, as they are responsible for AFOLU and bioenergy production emissions but do not receive credit for pellets displacing fossil fuel-related GHG emissions. Countries producing bioenergy from forest biomass, whether for domestic use or for export, should carefully consider potential implications of alternate forest carbon accounting methods to ensure that potential bioenergy pathways can contribute to GHG emissions reduction targets.

Environmental sustainability of urban road transport: an integrated analysis for life cycle emission impact

Despite of significant contributions of urban road transport to global economy and society, it is one of the largest sources of local and global emission impact. In order to address the environmental concerns of urban road transport it is imperative to achieve a holistic understanding of contributory factors causing emissions, which requires a complete look onto its whole life cycle. Previous studies were mainly based on segmental views, which mostly studied environmental impacts of individual transport modes and very few considered impacts other than operational phase. This study develops an integrated life cycle inventory model for urban road transport emissions from a holistic modal perspective. The Singapore case was used to demonstrate the model. Results show that total life cycle greenhouse gas emission from Singapore’s road transport sector is 7.8 million tons per year. The total amount of criteria air pollutants are also estimated in this study.

FutureSteelVehicle: leading edge innovation for steel body structures

WorldAutoSteel launched phase 2 of its FutureSteelVehicle programme with the aim to show automakers how latest and future steel grades and technologies can provide light body structures for electrified vehicles. The objective was to develop detailed design concepts and fully optimise a radically different steel body structure for a compact battery electric vehicle in production in the 2015–2020 timeframe. This article discloses the final outcomes of the phase 2 development, detailing steel body structure concepts for the aforementioned vehicles that achieved the aggressive mass target of 190 kg, while meeting 2015–2020 crash performance objectives as well as total life cycle greenhouse gas emissions targets, noise, vibration and harshness, and stiffness. This is achieved using advanced and ultra high strength steels, engineering design optimisation and advanced steel technologies.

Emissions Savings in the Corn‐Ethanol Life Cycle from Feeding Coproducts to Livestock

Environmental regulations on greenhouse gas (GHG) emissions from corn (Zea mays L.)-ethanol production require accurate assessment methods to determine emissions savings from coproducts that are fed to livestock. We investigated current use of coproducts in livestock diets and estimated the magnitude and variability in the GHG emissions credit for coproducts in the corn-ethanol life cycle. The coproduct GHG emissions credit varied by more than twofold, from 11.5 to 28.3 g CO(2)e per MJ of ethanol produced, depending on the fraction of coproducts used without drying, the proportion of coproduct used to feed beef cattle (Bos taurus) vs. dairy or swine (Sus scrofa), and the location of corn production. Regional variability in the GHG intensity of crop production and future livestock feeding trends will determine the magnitude of the coproduct GHG offset against GHG emissions elsewhere in the corn-ethanol life cycle. Expansion of annual U.S. corn-ethanol production to 57 billion liters by 2015, as mandated in current federal law, will require feeding of coproduct at inclusion levels near the biological limit to the entire U.S. feedlot cattle, dairy, and swine herds. Under this future scenario, the coproduct GHG offset will decrease by 8% from current levels due to expanded use by dairy and swine, which are less efficient in use of coproduct than beef feedlot cattle. Because the coproduct GHG credit represents 19 to 38% of total life cycle GHG emissions, accurate estimation of the coproduct credit is important for determining the net impact of corn-ethanol production on atmospheric warming and whether corn-ethanol producers meet state- and national-level GHG emissions regulations.