Biofuel Life-Cycle Analysis

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

A life-cycle assessment (LCA) of corn ethanol was conducted to determine the reduction in the life-cycle greenhouse gas (GHG) emissions of corn ethanol compared to gasoline by integrating biomass fuels in a 190 million liter (50 million gallon) per year dry-grind corn ethanol plant to replace fossil fuels (natural gas and grid electricity). 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 key inventory components of the LCA are corn production, stover production, ethanol production, fertilizer inputs, truck transport, co-product credits, ethanol transport to blending, biomass fuel conversion systems, and combustion of anhydrous ethanol (E100). The life-cycle GHG emission reduction for corn ethanol compared to gasoline (97.7 g CO2e/MJ gasoline) is 42.5% for PH with natural gas, 61.3% for PH with corn stover, 82.2% for CHP with corn stover, 81.6% for IGCC with natural gas, 127.7% for BIGCC with corn stover, and 119.1% 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 of corn ethanol by 31.5% compared to gasoline.

Abstract. 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 t/h (33.4 ton/h) of corn stover at 17% wet basis (w.b.) moisture content was modeled. The torrefaction plant produced 136,078 t/year (150,000 ton/year) of torrefied material (i.e., biocoal) at 1.1% (w.b.) moisture content and 28.1 MW th (96 million Btu/h) 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 from corn stover (including corn stover logistics GHG emissions) is 11.35 g CO 2 e/MJ biocoal dry matter (229.5 kg CO 2 e/t biocoal at 1.1% w.b. moisture content). The excess heat from the torrefaction plant met about 42.8% of the process steam needs (excluding the co-products dryer heat demand) of a 379 million liter per year (100 million gallon per year) natural gas-fueled dry-grind corn ethanol plant, 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 (i.e., 2.5 MW e ) would result in lower GHG emissions for biocoal, corn ethanol, and co-fired electricity than for the case where the torrefaction plant purchased electricity from the grid.

Development and application of an electric vehicles life-cycle energy consumption and greenhouse gas emissions analysis model

The influence of catalysts on biofuel life cycle analysis (LCA)

Land management practices such as cover crop adoption or manure application that can increase soil organic carbon (SOC) may provide a way to counter SOC loss upon removal of stover from corn fields for use as a biofuel feedstock. This report documents the data, methodology, and assumptions behind the incorporation of land management practices into corn-soybean systems that dominate U.S. grain production using varying levels of stover removal in the GREETTM (Greenhouse gases, Regulated Emissions, and Energy use in Transportation) model and its CCLUB (Carbon Calculator for Land Use change from Biofuels production) module. Tillage (i.e., conventional, reduced and no tillage), corn stover removal (i.e., at 0, 30% and 60% removal rate), and organic matter input techniques (i.e., cover crop and manure application) are included in the analysis as major land management practices. Soil carbon changes associated with land management changes were modeled with a surrogate CENTURY model. The resulting SOC changes were incorporated into CCLUB while GREET was expanded to include energy and material consumption associated with cover crop adoption and manure application. Life-cycle greenhouse gas (GHG) emissions of stover ethanol were estimated using a marginal approach (all burdens and benefits assigned to corn stover ethanol) and an energy allocation approach (burdens and benefits divided between grain and stover ethanol). In the latter case, we considered corn grain and corn stover ethanol to be produced at an integrated facility. Life-cycle GHG emissions of corn stover ethanol are dependent upon the analysis approach selected (marginal versus allocation) and the land management techniques applied. The expansion of CCLUB and GREET to accommodate land management techniques can produce a wide range of results because users can select from multiple scenario options such as choosing tillage levels, stover removal rates, and whether crop yields increase annually or remain constant. In a scenario with conventional tillage and a 30% stover removal rate, life-cycle GHG emissions for a combined gallon of corn grain and stover ethanol without cover crop adoption or manure application are 49 g CO2eq MJ-1, in comparison with 91 g CO2eq MJ-1 for petroleum gasoline. Adopting a cover crop or applying manure reduces the former ethanol life-cycle GHG emissions by 8% and 10%, respectively. We considered two different life cycle analysis approaches to develop estimates of life-cycle GHG emissions for corn stover ethanol, marginal analysis and energy allocation. In the same scenario, this fuel has GHG emissions of 12 – 20 g CO2eq MJ-1 (for manure and cover crop application, respectively) and 45 – 48 g CO2eq MJ-1 with the marginal approach and the energy allocation approach, respectively.

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

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

Aluminum production is a major energy consumer and important source of greenhouse gas (GHG) emissions globally. Estimation of the energy consumption and GHG emissions caused by aluminum production in China has attracted widespread attention because China produces more than half of the global aluminum. This paper conducted life cycle (LC) energy consumption and GHG emissions analysis of primary and recycled aluminum in China for the year 2020, considering the provincial differences on both the scale of self-generated electricity consumed in primary aluminum production and the generation source of grid electricity. Potentials for energy saving and GHG emissions reductions were also investigated. The results indicate that there are 157,207 MJ of primary fossil energy (PE) consumption and 15,947 kg CO2-eq of GHG emissions per ton of primary aluminum ingot production in China, with the LC GHG emissions as high as 1.5–3.5 times that of developed economies. The LC PE consumption and GHG emissions of recycled aluminum are very low, only 7.5% and 5.3% that of primary aluminum, respectively. Provincial-level results indicate that the LC PE and GHG emissions intensities of primary aluminum in the main production areas are generally higher while those of recycled aluminum are lower in the main production areas. LC PE consumption and GHG emissions can be significantly reduced by decreasing electricity consumption, self-generated electricity management, low-carbon grid electricity development, and industrial relocation. Based on this study, policy suggestions for China’s aluminum industry are proposed. Recycled aluminum industry development, restriction of self-generated electricity, low-carbon electricity utilization, and industrial relocation should be promoted as they are highly helpful for reducing the LC PE consumption and GHG emissions of the aluminum industry. In addition, it is recommended that the central government considers the differences among provinces when designing and implementing policies.

The pyrolysis of biomass can help produce liquid transportation fuels with properties similar to those of petroleum gasoline and diesel fuel. Argonne National Laboratory conducted a life-cycle (i.e., well-to-wheels [WTW]) analysis of various pyrolysis pathways by expanding and employing the Greenhouse Gases, Regulated Emissions, and Energy Use in Transportation (GREET) model. The WTW energy use and greenhouse gas (GHG) emissions from the pyrolysis pathways were compared with those from the baseline petroleum gasoline and diesel pathways. Various pyrolysis pathway scenarios with a wide variety of possible hydrogen sources, liquid fuel yields, and co-product application and treatment methods were considered. At one extreme, when hydrogen is produced from natural gas and when bio-char is used for process energy needs, the pyrolysis-based liquid fuel yield is high (32% of the dry mass of biomass input). The reductions in WTW fossil energy use and GHG emissions relative to those that occur when baseline petroleum fuels are used, however, is modest, at 50% and 51%, respectively, on a per unit of fuel energy basis. At the other extreme, when hydrogen is produced internally via reforming of pyrolysis oil and when bio-char is sequestered in soil applications, the pyrolysis-based liquid fuel yield is low (15% of the dry mass of biomass input), but the reductions in WTW fossil energy use and GHG emissions are large, at 79% and 96%, respectively, relative to those that occur when baseline petroleum fuels are used. The petroleum energy use in all scenarios was restricted to biomass collection and transportation activities, which resulted in a reduction in WTW petroleum energy use of 92-95% relative to that found when baseline petroleum fuels are used. Internal hydrogen production (i.e., via reforming of pyrolysis oil) significantly reduces fossil fuel use and GHG emissions because the hydrogen from fuel gas or pyrolysis oil (renewable sources) displaces that from fossil fuel natural gas and the amount of fossil natural gas used for hydrogen production is reduced; however, internal hydrogen production also reduces the potential petroleum energy savings (per unit of biomass input basis) because the fuel yield declines dramatically. Typically, a process that has a greater liquid fuel yield results in larger petroleum savings per unit of biomass input but a smaller reduction in life-cycle GHG emissions. Sequestration of the large amount of bio-char co-product (e.g., in soil applications) provides a significant carbon dioxide credit, while electricity generation from bio-char combustion provides a large energy credit. The WTW energy and GHG emissions benefits observed when a pyrolysis oil refinery was integrated with a pyrolysis reactor were small when compared with those that occur when pyrolysis oil is distributed to a distant refinery, since the activities associated with transporting the oil between the pyrolysis reactors and refineries have a smaller energy and emissions footprint than do other activities in the pyrolysis pathway.

Plastic production and consumption contribute to climate change and the depletion of non-renewable fossil resources, necessitating a shift towards a circular economy. This study explored the potential of pyrolysis as a novel approach to managing plastic waste and achieving plastic circularity in the Netherlands. Specifically, we focused on the pyrolysis of DKR-350, a low-quality mixed-plastic sorting residue. Using the life cycle assessment framework, we analysed DKR-350 pyrolysis, based on empirical data from pilot-scale trials, from two perspectives depending on the system’s primary function: waste management or naphtha production. We also considered the impacts of pyrolysis feedstock pre-treatment, including washing. Our findings demonstrated that pyrolysis of DKR-350, with lifecycle greenhouse gas (GHG) emissions of 876 kg CO2 eq. per 1000 kg pyrolysed unwashed DKR-350, can offer significant environmental benefits compared to incineration, resulting in a 28%–31% reduction in lifecycle GHG emissions. Sensitivity analysis showed the potential for achieving a 39%–65% reduction in GHG emissions by 2030, with lifecycle GHG emissions representing a mere 470 kg CO2 eq. per 1000 kg pyrolysed unwashed DKR-350 for the best sensitivity case. Lastly, we analysed the carbon recovery efficiency – a potential circularity indicator based on substance flow – resulting in 38%–55% of recovered carbon in pyrolysis oil, the system’s main product from a lifecycle perspective.

The building sector contributes 12% of the greenhouse gas (GHG) emissions in Canada. Building heating is the main contributor to building-level GHG emissions, primarily due to natural gas combustion. Although carbon-capturing is an emerging technology used to curb the GHG emissions in the fossil fuel-based power generation sector, the possibility of implementing this technology in natural gas building heating systems has not been comprehensively explored. This paper aims to evaluate the life cycle GHG emission reduction potential of integrating carbon capturing systems in residential and commercial building heating systems. The GHG emission reduction potential of commercially available building level carbon-capturing system (which uses Potassium Hydroxide (KOH) to capture CO2 and generate Potassium Carbonate as a by-product) and a carbon-capturing technology used in fossil fuel power generation plants (which uses Mono Ethanol Amine (MEA) based chemical absorption to separate CO2) were compared. Life cycle GHG assessment was conducted using TRACI 2.0 impact assessment method. The percentage reduction of life cycle GHG emissions was lower than the operational GHG emission reduction in MEA based systems due to the embodied emissions associated with the carbon-capturing process life cycle. The KOH-based system also consists of a substantial amount of embodied GHG emissions. However, the life cycle GHG emissions reduction of the KOH-based system was higher than the GHG emissions reduced during the operation when avoided emissions of the by-products were accounted. The findings of this paper will assist building owners, community developers, and policymakers in assessing the feasibility of implementing building-level carbon-capturing in the future.

Globally, bioethanol is the largest volume biofuel used in the transportation sector, with corn-based ethanol production occurring mostly in the US and sugarcane-based ethanol production occurring mostly in Brazil. Advances in technology and the resulting improved productivity in corn and sugarcane farming and ethanol conversion, together with biofuel policies, have contributed to the significant expansion of ethanol production in the past 20 years. These improvements have increased the energy and greenhouse gas (GHG) benefits of using bioethanol as opposed to using petroleum gasoline. This article presents results from our most recently updated simulations of energy use and GHG emissions that result from using bioethanol made from several feedstocks. The results were generated with the GREET (Greenhouse gases, Regulated Emissions, and Energy use in Transportation) model. In particular, based on a consistent and systematic model platform, we estimate life-cycle energy consumption and GHG emissions from using ethanol produced from five feedstocks: corn, sugarcane, corn stover, switchgrass and miscanthus. We quantitatively address the impacts of a few critical factors that affect life-cycle GHG emissions from bioethanol. Even when the highly debated land use change GHG emissions are included, changing from corn to sugarcane and then to cellulosic biomass helps to significantly increase the reductions in energy use and GHG emissions from using bioethanol. Relative to petroleum gasoline, ethanol from corn, sugarcane, corn stover, switchgrass and miscanthus can reduce life-cycle GHG emissions by 19–48%, 40–62%, 90–103%, 77–97% and 101–115%, respectively. Similar trends have been found with regard to fossil energy benefits for the five bioethanol pathways.

Harvesting corn stover for biofuel production may decrease soil organic carbon (SOC) and increase greenhouse gas (GHG) emissions. Adding additional organic matter into soil or reducing tillage intensity, however, could potentially offset this SOC loss. Here, using SOC and life cycle analysis (LCA) models, we evaluated the impacts of land management change (LMC), that is, stover removal, organic matter addition, and tillage on spatially explicit SOC level and biofuels’ overall life cycle GHG emissions in US corn–soybean production systems. Results indicate that under conventional tillage (CT), 30% stover removal (dry weight) may reduce baseline SOC by 0.04 t C ha−1 yr−1 over a 30‐year simulation period. Growing a cover crop during the fallow season or applying manure, on the other hand, could add to SOC and further reduce biofuels’ life cycle GHG emissions. With 30% stover removal in a CT system, cover crop and manure application can increase SOC at the national level by about 0.06 and 0.02 t C ha−1 yr−1, respectively, compared to baseline cases without such measures. With contributions from this SOC increase, the life cycle GHG emissions for stover ethanol are more than 80% lower than those of gasoline, exceeding the US Renewable Fuel Standard mandate of 60% emissions reduction in cellulosic biofuels. Reducing tillage intensity while removing stover could also limit SOC loss or lead to SOC gain, which would lower stover ethanol life cycle GHG emissions to near or under the mandated 60% reduction. Without these organic matter inputs or reduced tillage intensity, however, the emissions will not meet this mandate. More efforts are still required to further identify key practical LMCs, improve SOC modeling, and accounting for LMCs in biofuel LCAs that incorporate stover removal.

Plug-in hybrid electric vehicle (PHEV) technology has the potential to help address economic, environmental, and national security concerns in the United States by reducing operating cost, greenhouse gas (GHG) emissions and petroleum consumption from the transportation sector. However, the net effects of PHEVs depend critically on vehicle design, battery technology, and charging frequency. To examine these implications, we develop an integrated optimization model utilizing vehicle physics simulation, battery degradation data, and U.S. driving data to determine optimal vehicle design and allocation of vehicles to drivers for minimum life cycle cost, GHG emissions, and petroleum consumption. We find that, while PHEVs with large battery capacity minimize petroleum consumption, a mix of PHEVs sized for 25–40 miles of electric travel produces the greatest reduction in lifecycle GHG emissions. At today’s average US energy prices, battery pack cost must fall below $460/kWh (below $300/kWh for a 10% discount rate) for PHEVs to be cost competitive with ordinary hybrid electric vehicles (HEVs). Carbon allowance prices have marginal impact on optimal design or allocation of PHEVs even at $100/tonne. We find that the maximum battery swing should be utilized to achieve minimum life cycle cost, GHGs, and petroleum consumption. Increased swing enables greater all-electric range (AER) to be achieved with smaller battery packs, improving cost competitiveness of PHEVs. Hence, existing policies that subsidize battery cost for PHEVs would likely be better tied to AER, rather than total battery capacity.