Reduction In Life Cycle Greenhouse Gas Emissions Research Articles

Global warming intensity of biofuel derived from switchgrass grown on marginal land in Michigan

AbstractEnergy crops for biofuel production, especially switchgrass (Panicum virgatum), are of interest from a climate change perspective. Here, we use outputs from a crop growth model and life cycle assessment (LCA) to examine the global warming intensity (GWI; g CO2 MJ−1) and greenhouse gas (GHG) mitigation potential (Mg CO2 year−1) of biofuel systems based on a spatially explicit analysis of switchgrass grown on marginal land (abandoned former cropland) in Michigan, USA. We find that marginal lands in Michigan can annually produce over 0.57 hm3 of liquid biofuel derived from nitrogen‐fertilized switchgrass, mitigating 1.2–1.5 Tg of CO2 year−1. About 96% of these biofuels can meet the Renewable Fuel Standard (60% reduction in lifecycle GHG emissions compared with conventional gasoline; GWI ≤37.2 g CO2 MJ−1). Furthermore, 73%–75% of these biofuels are carbon‐negative (GWI less than zero) due to enhanced soil organic carbon (SOC) sequestration. However, simulations indicate that SOC levels would fail to increase and even decrease on the 11% of lands where SOC stocks >>200 Mg C ha−1, leading to carbon intensities greater than gasoline. Results highlight the strong climate mitigation potential of switchgrass grown on marginal lands as well as the needs to avoid carbon rich soils such as histosols and wetlands and to ensure that productivity will be sufficient to provide net mitigation.

The value of low- and negative-carbon fuels in the transition to net-zero emission economies: Lifecycle greenhouse gas emissions and cost assessments across multiple fuel types

In recent macro-energy systems modeling studies of net-zero emissions pathways for the United States and elsewhere, fuels made via gasification of sustainably produced biomass coupled with carbon capture and storage (CCS) play critical roles in achieving economy-wide net-zero greenhouse gas emissions because they provide carbon-negative energy carriers. In this study, we develop lifecycle greenhouse gas (GHG) emissions and cost assessments to provide insights into the environmental and economic cost and value of hydrogen (H2), synthetic natural gas (SNG), and Fischer-Tropsch liquid (FTL) fuels made from 1) biomass, coupled with CCS, 2) natural gas, with CCS, and 3) renewably-generated electricity. We find that H2 production pathways are less costly to decarbonize than FTL and SNG pathways that use the same input feedstock and also provide the largest reductions in lifecycle GHG emissions per unit of delivered fuel. Sensitivity analyses on the levelized costs of carbon mitigation (LCCM) indicate that capital costs and capacity factors are influential for most of the pathways. Costs for processes that use natural gas as feedstock are more sensitive to changes in input feedstock intensity than other processes. Finally, we find that fuel production pathways starting from biomass and including CCS have the highest carbon mitigation potentials among all feedstock pathways. They also have the lowest production costs beyond certain threshold carbon emission price levels. Our findings help explain the critical role that biomass-based hydrogen production with CCS plays in macro-energy system models of the U.S. transition to net-zero emissions.

An ex ante life cycle assessment of wheat with high biological nitrification inhibition capacity.

It is essential to increase food production to meet the projected population increase while reducing environmental loads. Biological nitrification inhibition (BNI)-enabled wheat genetic stocks are under development through chromosome engineering by transferring chromosomal regions carrying the BNI trait from a wild relative (Leymus racemosus (Lam.) Tzvelev) into elite wheat varieties; field evaluation of these newly developed BNI-wheat varieties has started. Ten years from now, BNI-enabled elite wheat varieties are expected to be deployed in wheat production systems. This study aims to evaluate the impacts of introducing these novel genetic solutions on life cycle greenhouse gas (LC-GHG) emissions, nitrogen (N) fertilizer application rates and N-use efficiency (NUE). Scenarios were developed based on evidence of nitrification inhibition and nitrous oxide (N2O) emission reduction by BNI crops and by synthetic nitrification inhibitors (SNIs), as both BNI-wheat and SNIs slow the nitrification process. Scenarios including BNI-wheat will inhibit nitrification by 30% by 2030 and 40% by 2050. It was assumed that N fertilizer application rates can potentially be reduced, as N losses through N2O emissions, leaching and runoff are expected to be lower. The results show that the impacts from BNI-wheat with 40% nitrification inhibition by 2050 are assessed to be positive: a 15.0% reduction in N fertilization, a 15.9% reduction in LC-GHG emissions, and a 16.7% improvement in NUE at the farm level. An increase in ammonia volatilization had little influence on the reduction in LC-GHG emissions. The GHG emissions associated with N fertilizer production and soil N2O emissions can be reduced between 7.3 and 9.5% across the wheat-harvested area worldwide by BNI-wheat with 30% and 40% nitrification inhibition, respectively. However, the present study recommends further technological developments (e.g. further developments in BNI-wheat and the development of more powerful SNIs) to reduce environmental impacts while improving wheat production to meet the increasing worldwide demand.

A Local Ecosystem Assessment of the Potential for Net Negative Heavy-Duty Truck Greenhouse Gas Emissions through Biomethane Upcycling

Decarbonising heavy-duty trucks is challenging due to high journey power and energy requirements. With a growing fleet of commercial vehicles in the UK, biomethane can provide significant reductions in greenhouse gas (GHG) emissions compared to fossil diesel. Methane is a potent GHG with a global warming potential (GWP) of 23–36, therefore reducing levels in the atmosphere can have a significant impact on climate change. There are a range of anthropogenic sources of methane that could be collected and processed to provide sustainable energy (upcycled), e.g., agricultural waste and the waste water system. This paper explores the impact of using upcycled methane in transport in South East England, evaluating local sources of anthropogenic methane and the environmental and economic impact of its use for a heavy-duty truck compared to fossil and battery electric alternatives. Analysis concludes that the use of upcycled methane in transport can provide significant reductions in lifecycle GHG emissions compared to diesel, fossil natural gas or battery electric trucks, and give net negative GHG emissions where avoided environmental methane emissions are considered. Furthermore, upcycling solutions can offer a lower cost route to GHG reduction compared to electrification.

Life cycle performance of Cross Laminated Timber mid-rise residential buildings in Australia

Engineering wood products have significant potential as a sustainable alternative for concrete and steel in construction. Cross Laminated Timber (CLT) can add value to conventional timber products due to its high strength-to-weight ratio, simple installation, aesthetic features and environmental benefits. Recent changes in the national construction code permit structural timber buildings with a height of up to 25m, which demonstrates the strong commitment of the construction industry to adopt more sustainable practices. This paper aims to compare life cycle greenhouse gas emissions (LCGHGE) and life cycle cost (LCC) of CLT and reinforced concrete (RC) in identical midrise residential buildings in three most populated cities in Australia. It has shown that the CLT building has 30 % less LCGHGE compared with the RC building over a life span of 50 years in Melbourne, and 34% and 29% reduction in LCGHCE in Sydney and Brisbane, respectively. The results from LCC analysis showed that CLT building is 1.3% lower than conventional RC in Melbourne, and 0.9% lower in Sydney and Brisbane. The initial and end of life phases reflected reductions in LCGHGE and LCC for the CLT building whilst the operation phase incurred higher values. The extended service life of buildings has a major impact on the operational phase while changes in the discount rate have strong effects on the lifecycle operational and maintenance costs. Overall the CLT building outperformed the RC building in terms of LCGHGE and LCC across three cities. However, further savings in the operational phase with energy efficient methodologies and reuse or recycling of timber products at the end of life of the building can reinforce CLT as a sustainable alternative to RC construction.

Technoeconomic and life-cycle analysis of single-step catalytic conversion of wet ethanol into fungible fuel blendstocks

Technoeconomic and life-cycle analyses are presented for catalytic conversion of ethanol to fungible hydrocarbon fuel blendstocks, informed by advances in catalyst and process development. Whereas prior work toward this end focused on 3-step processes featuring dehydration, oligomerization, and hydrogenation, the consolidated alcohol dehydration and oligomerization (CADO) approach described here results in 1-step conversion of wet ethanol vapor (40 wt% in water) to hydrocarbons and water over a metal-modified zeolite catalyst. A development project increased liquid hydrocarbon yields from 36% of theoretical to >80%, reduced catalyst cost by an order of magnitude, scaled up the process by 300-fold, and reduced projected costs of ethanol conversion 12-fold. Current CADO products conform most closely to gasoline blendstocks, but can be blended with jet fuel at low levels today, and could potentially be blended at higher levels in the future. Operating plus annualized capital costs for conversion of wet ethanol to fungible blendstocks are estimated at $2.00/GJ for CADO today and $1.44/GJ in the future, similar to the unit energy cost of producing anhydrous ethanol from wet ethanol ($1.46/GJ). Including the cost of ethanol from either corn or future cellulosic biomass but not production incentives, projected minimum selling prices for fungible blendstocks produced via CADO are competitive with conventional jet fuel when oil is $100 per barrel but not at $60 per barrel. However, with existing production incentives, the projected minimum blendstock selling price is competitive with oil at $60 per barrel. Life-cycle greenhouse gas emission reductions for CADO-derived hydrocarbon blendstocks closely follow those for the ethanol feedstock.

Life cycle greenhouse gas emissions of hydrogen fuel production from chlor-alkali processes in the United States

By-product hydrogen from chlor-alkali processes can help meet the increasing demand for hydrogen fuel in early fuel cell electric vehicle markets (e.g., California) in the U.S. Hydrogen produced from chlor-alkali plants is typically combusted for process heat on site, vented to the atmosphere (i.e., wasted), or sold to the external merchant hydrogen market. Whether it is combusted, vented, or sold as a commodity, relevant information is lacking as to the life-cycle environmental benefits or trade-offs of using by-product hydrogen from chlor-alkali plants. A life-cycle analysis framework was employed to evaluate well-to-gate greenhouse gas (GHG) emissions associated with by-product hydrogen from chlor-alkali processes in comparison with hydrogen from the conventional centralized natural gas steam methane reforming (central SMR) pathway. U.S.-specific, plant-by-plant, and up-to-date chlor-alkali production characteristics were incorporated into the analysis. In addition to the venting and combustion scenarios, to deal with the multi-functionality of the chlor-alkali processes that simultaneously produce chlorine, sodium hydroxide, and hydrogen, two different co-product allocation strategies were adopted—mass allocation and market value allocation. It was estimated that by-product hydrogen production from chlor-alkali processes creates 1.3–9.8 kg CO2e/kg H2 of life-cycle GHG emissions on average, which is 20–90% less than the conventional central SMR pathway. The results vary with co-product treatment scenarios, regional electric grid characteristics, on-site power generation, product prices, and hydrogen yield. Despite the variations in the results, it was concluded that the life-cycle GHG emission reduction benefits of using by-product hydrogen from chlor-alkali processes are robust. With a diverse set of scenario analyses, the study developed a comprehensive and detailed life-cycle GHG emissions inventory of the chlor-alkali by-product hydrogen pathway and quantified sensitivity indices in the context of different assumptions and input parameter values.

Towards an Integrated Approach for Evaluating both the Life Cycle Environmental and Financial Performance of a Building: A Review

A building is responsible for the emission of a significant amount of greenhouse gas (GHG) emissions over the various stages of its life cycle. Industry and government have been primarily focused on assessing and implementing mitigation measures related to the operational GHG emissions of buildings, leaving the emissions related to other life cycle stages, such as raw material extraction and maintenance, largely ignored. However, the uptake of assessments, such as life cycle assessment (LCA), and mitigation measures that consider buildings’ emissions from a life cycle perspective has been slow due to various barriers. One such barrier that has not been as widely documented yet is the uncertainty towards the financial cost of life cycle GHG emission reduction. There has been an increase in studies that have included both the environmental and financial assessment of a building or building systems over its expected lifetime. These studies often use the economic methodology called life cycle costing (LCC), that complements the life cycle approach of LCA, to help quantify the financial impact of a project. However most of these studies either base their results on exemplary low energy buildings, not traditional buildings that dominate the built fabric. In addition there is a trend to primarily focus on residential buildings, leaving other building typologies neglected. Other aspects to notice from these studies include the fact that most present findings of the life cycle energy impact, not life cycle GHG impact. There is also a need to use more comprehensive life cycle inventory data, such as hybrid, not just process data, to provide more comprehensive results. And lastly, most studies consider at new buildings, not refurbished or existing buildings. LCA and LCC support each other from a life cycle perspective however there is still a need to further develop an approach to concurrently balance both economic and environmental performance to create a more sustainable built environment.

Life Cycle Assessment of Biofuels from Algae Hydrothermal Liquefaction: The Upstream and Downstream Factors Affecting Regulatory Compliance

Life-cycle greenhouse gas (LC-GHG) emissions are a principal metric used by the U.S. Environmental Protection Agency to determine whether a biofuel qualifies under the U.S. EPA’s Renewable Fuel Standard (RFS2). This paper identifies important factors in the quantification of LC-GHG of algae-derived diesel, jet fuel, and gasoline, using hydrothermal liquefaction (HTL) as a case study for algal biofuels. The results indicate that, under certain conditions, algae biofuels produced using HTL offer an over 50% reduction in LC-GHG emissions compared to their petroleum counterparts and would thus qualify as advanced biofuel and biomass-based biodiesel under RSF2. However, the results are sensitive to several upstream and downstream factors, specifically the CO2 supply chains used in feedstock production and the fuels that are produced using these algal feedstocks, respectively. Upstream processes for the production of algae include supplying gas or liquid phase CO2 to maintain culture viability, which is unlike ...

Consideration of black carbon and primary organic carbon emissions in life-cycle analysis of Greenhouse gas emissions of vehicle systems and fuels.

The climate impact assessment of vehicle/fuel systems may be incomplete without considering short-lived climate forcers of black carbon (BC) and primary organic carbon (POC). We quantified life-cycle BC and POC emissions of a large variety of vehicle/fuel systems with an expanded Greenhouse gases, Regulated Emissions, and Energy use in Transportation model developed at Argonne National Laboratory. Life-cycle BC and POC emissions have small impacts on life-cycle greenhouse gas (GHG) emissions of gasoline, diesel, and other fuel vehicles, but would add 34, 16, and 16 g CO2 equivalent (CO2e)/mile, or 125, 56, and 56 g CO2e/mile with the 100 or 20 year Global Warming Potentials of BC and POC emissions, respectively, for vehicles fueled with corn stover-, willow tree-, and Brazilian sugarcane-derived ethanol, mostly due to BC- and POC-intensive biomass-fired boilers in cellulosic and sugarcane ethanol plants for steam and electricity production, biomass open burning in sugarcane fields, and diesel-powered agricultural equipment for biomass feedstock production/harvest. As a result, life-cycle GHG emission reduction potentials of these ethanol types, though still significant, are reduced from those without considering BC and POC emissions. These findings, together with a newly expanded GREET version, help quantify the previously unknown impacts of BC and POC emissions on life-cycle GHG emissions of U.S. vehicle/fuel systems.

Environmental and economic assessment of producing hydroprocessed jet and diesel fuel from waste oils and tallow

Animal fats and waste oils are potential feedstocks for producing hydroprocessed esters and fatty acids (HEFA) jet and diesel fuels. This paper calculates the lifecycle greenhouse gas (GHG) emissions and production costs associated with HEFA jet and diesel fuels from tallow, and from yellow grease (YG) derived from used cooking oil. For YG, total CO2 equivalent (CO2 eq.) GHG emissions of jet and diesel were found to range between 16.8–21.4 g MJ−1 and 12.2–16.9 g MJ−1 respectively. This corresponds to lifecycle GHG emission reductions of 76–81% and 81–86% respectively, compared to their conventional counterparts. Two different system boundaries were considered for tallow-derived HEFA fuels. In System 1 (S1), tallow was treated as a by-product of the rendering industry, and emissions from rendering and fuel production were included. In System 2 (S2), tallow was considered as a by-product of the meat production industry, and in addition to the S1 emissions, cattle husbandry and slaughtering were also included. The lifecycle emissions (CO2 eq.) from HEFA jet fuel for S1 and S2 were estimated to be 25.7–37.5 g MJ−1 and 67.1–83.9 g MJ−1 respectively. HEFA diesel lifecycle emissions were found to be 21.3–33.3 g MJ−1 for S1 and 63.4–80.5 g MJ−1 for S2. Production costs for these fuels were calculated using a discounted cash flow rate of return model. The minimum selling price was estimated to be 880 $ m−3–1060 $ m−3 for YG-derived HEFA, and 1050–1250 $ m−3 for tallow-derived HEFA fuels.

Life cycle assessment of a corn stover torrefaction plant integrated with a corn ethanol plant and a coal fired power plant

A life cycle assessment (LCA) study was conducted to understand and assess potential greenhouse gas (GHG) emissions reduction benefits of a biomass torrefaction business integrated with other industrial businesses for the use of the excess heat from the torrefaction off-gas volatiles and biocoal. A torrefaction plant processing 30.3 Mg h−1 of corn stover at 17% wet basis (w.b.) moisture content was modeled. The torrefaction plant produced 136,078 Mg y−1 of biocoal at 1.1% w.b. moisture content and 28.1 MW of excess heat energy in the torrefaction off-gas volatiles. At the torrefaction plant gate, the life-cycle GHG emission for the production of biocoal (including corn stover logistics emissions) is 11.35 g MJ−1 carbon dioxide equivalent (dry basis) (i.e., 229.5 kg Mg−1 carbon dioxide equivalent of biocoal at 1.1% w.b. moisture content). The excess heat from the torrefaction plant met 42.8% of the process steam needs of a U.S. Midwest dry-grind corn ethanol plant producing 0.38 hm3 y−1 of denatured ethanol, which results in about 40% reduction in life-cycle GHG emissions for corn ethanol compared to gasoline. Co-firing 10%, 20%, and 30% (energy basis) of biocoal at a coal-fired power plant reduced the life-cycle GHG emissions of electricity generated by 8.5%, 17.0%, and 25.6%, respectively, compared to 100% coal-fired electricity. A sensitivity analysis showed that adding a combined heat and power (CHP) system at the torrefaction plant to meet 100% electricity demand of the torrefaction plant (2.5 MW) could further reduce the GHG emissions for biocoal, corn ethanol, and co-fired electricity.

Life cycle and cost assessment of mineral carbonation for carbon capture and storage in European power generation

Large-scale greenhouse gas (GHG) emission reductions are crucial for achieving the European goals for climate change mitigation. A frequently discussed option is carbon capture and storage (CCS), where CO2 emissions from point sources are captured and stored in geologic structures. However, concerns about risks of leakages of CO2 from geological storage have been raised. These risks could be avoided with ex situ mineral carbonation, where the captured CO2 is stored in an inert and stable solid form after reacting with calcium and magnesium silicates. For a comprehensive assessment of the environmental and economic performance of this CO2 storage option in fossil-fueled power generation chains, life cycle assessment (LCA) and levelized cost of electricity (LCoE) calculations are performed. The implementation of CCS using mineral carbonation leads to life cycle GHG emission reductions of 15–64% and LCoE increases of 90–370% on a per kWhel basis compared to a reference power plant without CCS. The life cycle GHG emission reduction achievable with mineral sequestration is less substantial than with geological storage of CO2 due to significant energy and chemical additives requirements. Accordingly, LCA results for other environmental indicators are worse than those of the reference plant without CCS and the geological CO2 storage option.

Life cycle assessment of carbon capture and storage in power generation and industry in Europe

To prevent serious negative effects of climate change, greenhouse gas (GHG) emission reductions are required on global level and at large scale. One option is Carbon Capture and Storage (CCS) which aims to capture carbon dioxide (CO2) emissions from power generation and industry and store it permanently in geologic structures. For a comprehensive comparative assessment of the environmental performance of CCS technologies life cycle assessment (LCA) is required. This study provides a systematic comparison of LCA-based environmental performances of fossil and wood power plants as well as cement production in Europe for 2025 and 2050 with and without CCS. The implementation of CCS leads to life cycle GHG emission reductions of 68–92% for fossil power generation and 39–78% for cement production whilst to negative ones for wood power generation. There are trade-offs with respect to environmental and human health impacts due to direct (e.g. air emissions) and indirect (e.g. coal mining) impacts of the increase in fuel use and additional processes and materials necessary for CCS. Cement plants are suitable point sources for the implementation of CCS. Here the energy supply for the CO2 capture and compression is decisive for the environmental impacts, what indicates benefits of system integration.

Reducing life cycle greenhouse gas emissions of corn ethanol by integrating biomass to produce heat and power at ethanol plants

Abstract A life-cycle assessment (LCA) of corn ethanol was conducted to determine the reduction in the life-cycle greenhouse gas (GHG) emissions for corn ethanol compared to gasoline by integrating biomass fuels to replace fossil fuels (natural gas and grid electricity) in a U.S. Midwest dry-grind corn ethanol plant producing 0.19 hm3 y−1 of denatured ethanol. The biomass fuels studied are corn stover and ethanol co-products [dried distillers grains with solubles (DDGS), and syrup (solubles portion of DDGS)]. The biomass conversion technologies/systems considered are process heat (PH) only systems, combined heat and power (CHP) systems, and biomass integrated gasification combined cycle (BIGCC) systems. The life-cycle GHG emission reduction for corn ethanol compared to gasoline is 38.9% for PH with natural gas, 57.7% for PH with corn stover, 79.1% for CHP with corn stover, 78.2% for IGCC with natural gas, 119.0% for BIGCC with corn stover, and 111.4% for BIGCC with syrup and stover. These GHG emission estimates do not include indirect land use change effects. GHG emission reductions for CHP, IGCC, and BIGCC include power sent to the grid which replaces electricity from coal. BIGCC results in greater reductions in GHG emissions than IGCC with natural gas because biomass is substituted for fossil fuels. In addition, underground sequestration of CO2 gas from the ethanol plant’s fermentation tank could further reduce the life-cycle GHG emission for corn ethanol by 32% compared to gasoline.