Life Cycle Greenhouse Gas Analysis Research Articles

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.

The Ethanol–Ethyl Acetate System as a Biogenic Hydrogen Carrier

Liquid organic hydrogen carriers will likely be a key element of a future hydrogen economy by enabling the storage and transport of large quantities of hydrogen. Ethanol is a liquid organic hydrogen carrier that is readily available from biological resources, which undergoes a reversible reaction to yield hydrogen and ethyl acetate. The objective of the present study is to obtain a better understanding of the thermodynamic and environmental suitability of the ethanol–ethyl acetate cycle for hydrogen storage applications. The analysis covers three aspects: thermodynamics of the chemical reaction, energy balance of the process, and a first‐order assessment of greenhouse gas emissions. Thermodynamics of the reaction are characterized by a standard Gibbs energy of reaction close to zero which allows the reaction to be shifted between hydrogenation and dehydrogenation within a moderate window of temperature and pressure conditions. The energy demand for dehydrogenation is comparatively small, resulting in an overall system efficiency of 88%. A life cycle greenhouse gas analysis over a 20‐year storage system lifetime gives a carbon intensity of 7.0 kg‐CO2eq/kg‐H2 delivered. These results indicate that the ethanol–ethyl acetate system has considerable promise as a hydrogen carrier and should be the subject of further research.

Incremental approach for the life-cycle greenhouse gas analysis of carbon capture and utilization

Electro-fuels (e-fuels) are examples of carbon capture and utilization (CCU) hydrocarbon products that are derived from captured carbon dioxide (CO2), while using renewable electricity as the energy feedstock. The environmental impacts of CCU products (e.g., e-fuel) are systematically quantified through life-cycle analysis (LCA). Previous studies evaluating LCA of e-fuels proposed frameworks with an expanded system boundary approach that included the entire supply chain of the production process generating the CO2 for CCU, in addition to the supply chain of the CCU product. This expanded system boundary approach evaluates two system boundaries, and uses deduction methods to calculate the carbon intensity (CI) of the CCU product (e-fuel). This paper proposes a simpler system boundary using an incremental approach that can calculate identical CI of the CCU product (e-fuel), while avoiding the extensive calculations in the expanded system boundary framework. The proposed incremental approach allocates the burdens of the CO2 capturing process to the CO2 feedstock supplying the CCU production process (e.g., e-fuel production). The CI of the captured CO2 supplied to CCU process is determined by the energy and material requirements for the CO2 capturing process and transportation to the CCU plant. Thus, the CI of CO2 supplied to CCU process can be directly linked to the CI of e-fuel without the need to conduct LCA of the preceding process that generates the CO2 for CCU.

A screening-level life cycle greenhouse gas analysis of CO2 enhanced oil recovery with CO2 sourced from the Shute Creek natural gas-processing facility

This life cycle analysis (LCA) evaluates life cycle greenhouse gas (GHG) emissions associated with a system that produces both natural gas and crude oil. Two systems are defined: System 1, which independently produces natural gas and oil, and System 2, which captures carbon dioxide (CO2) from the natural gas-processing plant and utilizes this captured CO2 for enhanced oil recovery (EOR). The LCA uses customized spreadsheet models with emission factors from peer-reviewed literature and publications of the National Energy Technology Laboratory of the U.S. Department of Energy. The modeling results show that the CO2 EOR scenario using captured CO2 produces both natural gas and oil with lower life cycle GHG emissions than alternative systems producing natural gas and oil independently. Sensitivity analyses show that the model results are most sensitive to the fraction of CO2 captured (or equivalently, the fraction of CO2 vented) at the natural gas-processing facility and the incremental oil recovery factor and net CO2 utilization factor of the EOR operations. The input variable driving the relative difference in life cycle GHG emissions between these two systems is the fraction of CO2 captured at the natural gas-processing facility (i.e., the capture rate). The results of this study highlight the necessity of linking processes in the life cycle modeling, as a change to one process can affect other processes within the coupled energy system comprised of natural gas and oil. In addition, this analysis shows, as prior work has also suggested, that CO2 EOR using captured anthropogenic CO2 provides a viable means for offsetting carbon emissions from oil production and combustion via the associated storage of CO2 that occurs incidentally during this tertiary method of oil recovery.

Life Cycle Greenhouse Gas Analysis of Multiple Vehicle Fuel Pathways in China

The Tsinghua University Life Cycle Analysis Model (TLCAM) is applied to calculate the life cycle fossil energy consumption and greenhouse gas (GHG) emissions for more than 20 vehicle fuel pathways in China. In addition to conventional gasoline and diesel, these include coal- and gas-based vehicle fuels, and electric vehicle (EV) pathways. The results indicate the following. (1) China’s current dependence on coal and relative low-efficiency processes limits the potential for most alternative fuel pathways to decrease energy consumption and emissions; (2) Future low-carbon electricity pathways offer more obvious advantages, with coal-based pathways needing to adopt carbon dioxide capture and storage technology to compete; (3) A well-to-wheels analysis of the fossil energy consumption of vehicles fueled by compressed natural gas and liquefied natural gas (LNG) showed that they are comparable to conventional gasoline vehicles. However, importing rather than domestically producing LNG for vehicle use can decrease domestic GHG emissions by 35% and 31% compared with those of conventional gasoline and diesel vehicles, respectively; (4) The manufacturing and recovery of battery and vehicle in the EV analysis has significant impact on the overall ability of EVs to decrease fossil energy consumption and GHG emissions from ICEVs.

Updating the U.S. Life Cycle GHG Petroleum Baseline to 2014 with Projections to 2040 Using Open-Source Engineering-Based Models.

The National Energy Technology Laboratory produced a well-to-wheels (WTW) life cycle greenhouse gas analysis of petroleum-based fuels consumed in the U.S. in 2005, known as the NETL 2005 Petroleum Baseline. This study uses a set of engineering-based, open-source models combined with publicly available data to calculate baseline results for 2014. An increase between the 2005 baseline and the 2014 results presented here (e.g., 92.4 vs 96.2 g CO2e/MJ gasoline, + 4.1%) are due to changes both in modeling platform and in the U.S. petroleum sector. An updated result for 2005 was calculated to minimize the effect of the change in modeling platform, and emissions for gasoline in 2014 were about 2% lower than in 2005 (98.1 vs 96.2 g CO2e/MJ gasoline). The same methods were utilized to forecast emissions from fuels out to 2040, indicating maximum changes from the 2014 gasoline result between +2.1% and -1.4%. The changing baseline values lead to potential compliance challenges with frameworks such as the Energy Independence and Security Act (EISA) Section 526, which states that Federal agencies should not purchase alternative fuels unless their life cycle GHG emissions are less than those of conventionally produced, petroleum-derived fuels.

Field-to-Fuel Performance Testing of Lignocellulosic Feedstocks for Fast Pyrolysis and Upgrading: Techno-economic Analysis and Greenhouse Gas Life Cycle Analysis

This work shows preliminary results from techno-economic analysis and life cycle greenhouse gas analysis of the conversion of seven (7) biomass feedstocks to produce liquid transportation fuels via fast pyrolysis and upgrading via hydrodeoxygenation. The biomass consists of five (5) pure feeds (pine, tulip poplar, hybrid poplar, switchgrass, corn stover) and two blends. Blend 1 consists of equal weights of pine, tulip poplar, and switchgrass, and blend 2 is 67% pine and 33% hybrid poplar. Upgraded oil product yield is one of the most significant parameters affecting the process economics, and is a function of both fast pyrolysis oil yield and hydrotreating oil yield. Pure pine produced the highest overall yield, while switchgrass produced the lowest. Interestingly, herbaceous materials blended with woody biomass performed nearly as well as pure woody feedstock, suggesting a nontrivial relationship between feedstock attributes and production yield. Production costs are also highly dependent upon hydrotreat...

Life cycle greenhouse gas analysis of bioenergy generation alternatives using forest and wood residues in remote locations: A case study in British Columbia, Canada

Utilization of forest and wood residues as bioenergy feedstock in some remote communities could reduce environmental burdens and increase development opportunities. In a thorough bioenergy project planning, in addition to the economic performance, the potential greenhouse gas (GHG) emissions from investment alternatives should be considered. We present an economic assessment and a life cycle analysis of GHG emissions of alternative bioenergy systems, which include four combustion and gasification technologies with different capacities (0.5MW, 2MW and 5MW), in two remote communities in British Columbia, Canada. In the analysis, all stages from harvesting to energy production are included, and the GHG emissions of the baseline system in each community (the current situation with all the products and services it provides) are used as the reference for comparison. Results of this study show that for small scale alternatives (0.5MW and 2MW), cogenerating plants using boiler/steam turbines generate the cheapest electricity, while for larger scale alternatives (5MW), the most economical plant alternative is a gasification cogeneration system. In the community where all energy needs are currently satisfied using fossil fuels, and all biomass residues (forest and sawmill residues) are currently disposed by burning, net reductions of up to 40,909t of CO2 equivalent GHG emissions could be achieved with the installation of a 5MW boiler/steam turbine cogenerating heat and electricity. In the community where the current energy mix is mostly supplied from other renewable sources (i.e. hydro), and where forest residues are disposed by burning and sawmill residues are landfilled, the net GHG emission reductions that can be achieved with a bioenergy system are considerably lower (2535t of CO2 equivalent emissions with a 5MW cogenerating gasification system) or null, since the carbon capture of current biomass disposal in landfill outweighs the carbon emission reduction of most bioenergy alternatives.

Lifecycle Greenhouse Gas Analysis of an Anaerobic Codigestion Facility Processing Dairy Manure and Industrial Food Waste.

Anaerobic codigestion (AcoD) can address food waste disposal and manure management issues while delivering clean, renewable energy. Quantifying greenhouse gas (GHG) emissions due to implementation of AcoD is important to achieve this goal. A lifecycle analysis was performed on the basis of data from an on-farm AcoD in New York, resulting in a 71% reduction in GHG, or net reduction of 37.5 kg CO2e/t influent relative to conventional treatment of manure and food waste. Displacement of grid electricity provided the largest reduction, followed by avoidance of alternative food waste disposal options and reduced impacts associated with storage of digestate vs undigested manure. These reductions offset digester emissions and the net increase in emissions associated with land application in the AcoD case relative to the reference case. Sensitivity analysis showed that using feedstock diverted from high impact disposal pathways, control of digester emissions, and managing digestate storage emissions were opportunities to improve the AcoD GHG benefits. Regional and parametrized emissions factors for the storage emissions and land application phases would reduce uncertainty.

Life cycle greenhouse gas analysis of biojet fuels with a technical investigation into their impact on jet engine performance

Biojet fuels have been claimed to be one of the most promising and strategic solutions to mitigate aviation emissions. This study examines the environmental competence of Bio-Synthetic Paraffinic Kerosene (Bio-SPKs) against conventional Jet-A, through development of a life cycle GHG model (ALCEmB – Assessment of Life Cycle Emissions of Biofuels) from “cradle-grave” perspective. This model precisely calculates the life cycle emissions of the advanced biofuels through a multi-disciplinary study entailing hydrocarbon chemistry, thermodynamic behaviour and fuel combustion from engine/aircraft performance, into the life cycle studies, unlike earlier studies. The aim of this study is predict the “cradle-grave” carbon intensity of Camelina SPK, Microalgae SPK and Jatropha SPK through careful estimation and inclusion of combustion based emissions, which contribute ≈70% of overall life cycle emissions (LCE). Numerical modelling and non-linear/dynamic simulation of a twin-shaft turbofan, with an appropriate airframe, was conducted to analyse the impact of alternative fuels on engine/aircraft performance. ALCEmB revealed that Camelina SPK, Microalgae SPK and Jatropha SPK delivered 70%, 58% and 64% LCE savings relative to the reference fuel, Jet-A1. The net energy ratio analysis indicates that current technology for the biofuel processing is energy efficient and technically feasible. An elaborate gas property analysis infers that the Bio-SPKs exhibit improved thermodynamic behaviour in an operational gas turbine engine. This thermodynamic effect has a positive impact on aircraft-level fuel consumption and emissions characteristics demonstrating fuel savings in the range of 3–3.8% and emission savings of 5.8–6.3% (CO2) and 7.1–8.3% (LTO NOx), relative to that of Jet-A.

Life cycle greenhouse gas analysis for automotive applications – ALife cycle greenhouse gas analysis for automotive applications – A case study for taxis in Singapore case study for taxis in Singapore

Life cycle greenhouse gas analysis for automotive applications – ALife cycle greenhouse gas analysis for automotive applications – A case study for taxis in Singapore case study for taxis in Singapore

Effects of Ethanol on Vehicle Energy Efficiency and Implications on Ethanol Life-Cycle Greenhouse Gas Analysis

Bioethanol is the world's largest-produced alternative to petroleum-derived transportation fuels due to its compatibility within existing spark-ignition engines and its relatively mature production technology. Despite its success, questions remain over the greenhouse gas (GHG) implications of fuel ethanol use with many studies showing significant impacts of differences in land use, feedstock, and refinery operation. While most efforts to quantify life-cycle GHG impacts have focused on the production stage, a few recent studies have acknowledged the effect of ethanol on engine performance and incorporated these effects into the fuel life cycle. These studies have broadly asserted that vehicle efficiency increases with ethanol use to justify reducing the GHG impact of ethanol. These results seem to conflict with the general notion that ethanol decreases the fuel efficiency (or increases the fuel consumption) of vehicles due to the lower volumetric energy content of ethanol when compared to gasoline. Here we argue that due to the increased emphasis on alternative fuels with drastically differing energy densities, vehicle efficiency should be evaluated based on energy rather than volume. When done so, we show that efficiency of existing vehicles can be affected by ethanol content, but these impacts can serve to have both positive and negative effects and are highly uncertain (ranging from -15% to +24%). As a result, uncertainties in the net GHG effect of ethanol, particularly when used in a low-level blend with gasoline, are considerably larger than previously estimated (standard deviations increase by >10% and >200% when used in high and low blends, respectively). Technical options exist to improve vehicle efficiency through smarter use of ethanol though changes to the vehicle fleets and fuel infrastructure would be required. Future biofuel policies should promote synergies between the vehicle and fuel industries in order to maximize the society-wise benefits or minimize the risks of adverse impacts of ethanol.

Comments of Colin R. Hagan Submitted to the U.S. Senate Committee on Energy and Natural Resources in Response to the ‘White Paper on a Clean Energy Standard’

These comments respond specifically to a question raised in the U.S. Senate Committee on Energy and Natural Resources’ “White Paper on a Clean Energy Standard.” These comments argue that the Committee should consider lifecycle greenhouse gas analysis as one factor in determining whether an energy resource, or a specific project, is a “clean energy” resource for the purposes of a clean energy standard. Lifecycle analysis is increasingly recognized as a necessary assessment for understanding the full greenhouse gas consequences of generating electricity, or producing transportation fuels, with a particular resource. Applying a lifecycle analysis in a clean energy standard will help ensure that a clean energy mandate maximizes greenhouse gas reductions. In addition, a lifecycle analysis can help identify cost-effective opportunities for reducing emissions from new energy projects. These comments do not provide a full assessment or recommendation for how to incorporate lifecycle analysis into a clean energy standard. Nor do these comments recommend the inclusion or exclusion of any resources in a clean energy standard. Rather, these comments merely highlight the importance of including a lifecycle assessment of greenhouse gases in determining whether a resource qualifies as a “clean energy” resource.

Closing the Gap: Using the Clean Air Act to Control Lifecycle Greenhouse Gas Emissions from Energy Facilities

As the United States moves forward with regulations and policies to control greenhouse gas emissions from energy facilities, regulators and policymakers should require proposed energy facilities to undergo a lifecycle greenhouse gas analysis. Scientific research demonstrates that a significant portion of the total emissions from a particular facility occur upstream or throughout the lifecycle of the resource production process. A lifecycle greenhouse gas analysis, therefore, will ensure that the total consequences of a particular facility or energy resource will be taken into account. In addition, such an analysis would help identify cost-effective opportunities to reduce emissions. The U.S. Environmental Protection Agency (EPA) has an opportunity to require lifecycle analysis for energy facilities as it crafts new Clean Air Act regulations to control greenhouse gas emissions. Congress has recognized the value of lifecycle analysis in the Renewable Fuels Standard, which now affirmatively requires EPA to conduct lifecycle analysis for certain biofuels. This Note considers whether EPA also has the authority to require proposed energy facilities subject to Clean Air Act's pre-construction review to undergo a similar analysis. Reviewing the provisions of the Clean Air Act that govern emissions from energy facilities, this Note concludes that EPA does have the authority to require lifecycle greenhouse gas analysis for proposed energy facilities.

Life-cycle greenhouse gas analysis of LNG as a heavy vehicle fuel in Europe

The aim of the present study was to compare the life cycle, in terms of greenhouse gas (GHG) emissions, of diesel and liquefied natural gas (LNG) used as fuels for heavy-duty vehicles in the European market (EU-15). A literature review revealed that the numerous studies conducted have reported different results when the authors departed from different baseline assumptions and reference scenarios. For our study, we concentrated on the European scenario and on heavy-duty road transport vehicles, given their important incidence on the global emissions of GHG. Two possible LNG procurement strategies were considered i.e. purchasing it directly from the regasification terminal (LNG-TER) or producing LNG locally (at the service station) with small-scale plants (LNG-SSL). We ascertained that the use of LNG-TER enables a 10% reduction in GHG emissions by comparison with diesel, while the emissions resulting from the LNG-SSL solution are comparable with those of diesel.