Numerous LCA tools have been used to evaluate the GHG emissions associated with various vehicle-fuel technologies, including fossil fuels, biofuels, hydrogen fuel cell electric vehicles (FCEVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVS), and battery electric vehicles (BEVs). … None of the aforementioned studies conducted a comprehensive cradle-to-grave LCA (including both fuel cycle and vehicle cycle) of the U.S. light-duty vehicles (LDVs) to calculate the GHG emissions and costs of a wide range of vehicle-fuel technologies—highlighting the need for a comprehensive LCA and economic assessment focused on the U.S. transportation sector.

To address this research gap, we conducted an independent, comprehensive, cradle-to-grave (C2G) (vehicle and fuel cycle) LCA of energy consumption, GHG emissions, vehicle and fuel costs, carbon abatement costs, and technological readiness for current and future LDV/fuel technology pathways; the data and assumptions in our study were vetted by experts from the U.S. automotive and energy industries.

—Elgowainy et al.

The team used bottom-up vehicle simulation models, LCA models, and techno-economic discounted cash flow models for the C2G analysis. The analysis addressed every aspect of the vehicle and fuel life cycles, including manufacturing, end-of-life disposal (recycling and scrappage), and vehicle operation, as well as fuel feedstock production and transportation, fuel production, and fuel distribution.

GHG emissions and energy use were calculated using Argonne’s GREET model; vehicle fuel economies and manufacturing costs were estimated using Argonne’s Autonomie model by sizing components of the different vehicle architectures to deliver comparable operational performance (e.g., time to accelerate from 0–60 mph, maximum speed), thus eliminating important confounding factors.

The costs to consumers for established fuels were based on the US Energy Information Administration’s (EIA’s) 2015 Annual Energy Outlook, while techno-economic analysis models with consistent economic assumptions were used to estimate the costs for hydrogen and advanced bio-derived fuels.

Fuels or energy carriers in the study included gasoline, ethanol, diesel, CNG, LPG, hydrogen, and electricity. For each of these, the team examined the GHG emissions and costs for a current technology case and possible future technology production pathways.

Calculated life-cycle GHG emissions from current vehicle-fuel technology pathways and from those deemed scalable in the 2025–2030 timeframe (following an assessment of technological readiness). Credit: ACS, Elgowainy et al. Click to enlarge.

Broadly, the team found that gasoline ICEVs using current technology have C2G emissions of ∼450 gCO₂e/mi (grams of carbon dioxide equivalents per mile), while C2G emissions from HEVs, PHEVs, H2 FCEVs, and BEVs range from 300–350 gCO₂e/mi.

The team expects future vehicle efficiency gains to reduce emissions to ∼350 g_CO2e/mi for ICEVs and ∼250 gCO₂e/mi for HEVs, PHEVs, FCEVs, and BEVs. Utilizing low-carbon fuel pathways yields GHG reductions more than double those achieved by vehicle efficiency gains alone.

However, the researchers noted, although the findings show that advanced vehicle and fuel technologies could lead to deep reductions in GHG emissions compared with a conventional gasoline ICEV, impacts on the upfront vehicle purchase price and the levelized cost of driving (LCD) are decisive factors in the actual adoption of these advanced vehicles by consumers.

For 2025–2030, ICEVs using conventional gasoline appear to be the least expensive vehicle-fuel systems for the end user on a per-mile basis. LCDs ranged from 26¢ per mile for conventional gasoline ICEVs to 38¢ per mile for long-range BEVs using electricity derived from solar energy. The costs of other pathways include 31¢ per mile for corn-stover ethanol ICEVs, 28¢–30¢ per mile for PHEVs and H2 FCEVs, and 34¢–38¢ per mile for BEVs. The central estimate of the future technology conventional ICEV is $2,110 more than the central estimate of the current technology version, due to advances in engine and materials technologies.

Levelized cost of driving for current (2015, dark bars) and future (2025–2030, light bars) technology pathways. Low-volume production is represented by black diamonds. CNG and LPG vehicles are evaluated only for the current technology case. Credit: ACS, Elgowainy et al. Click to enlarge.

Cost of avoided GHGs for current (2015, dark bars) and future (2025–2030, light bars) technology pathways compared with a conventional gasoline ICEV (baseline). Lifetime costs for carbon mitigation using current technologies range from $170 to $2,700 per tonne. The lowest-cost future pathways are shown for each vehicle type, and range from $90 to $410 per tonne. Credit: ACS, Elgowainy et al. Click to enlarge.

The costs estimated for avoiding GHG emissions from LDVs … are higher than the externalities estimated for the social cost of CO₂. Furthermore, while these alternative vehicle-fuel systems provide large GHG emissions reductions, they require further research and development to compete against the conventional systems available in the market today.

This contextualization highlights the utility of the cost of avoided emissions as a metric for comparing different technologies. However, using the cost-of-avoided-emissions metric has limitations; the technologies considered in the analysis differ not only in terms of their lifetime GHG emissions but also in other important attributes, such as local air-quality-related emissions, reliance on different energy sources and fuels (e.g., petroleum, natural gas, ethanol, hydrogen, electricity), and functionality (e.g., more limited range and longer refueling times for BEVs).

… To achieve large-scale GHG emissions reductions in the United States, emissions reductions will be required in all sectors: electric power generation, residential, commercial, industrial, and transportation. The findings presented here highlight the challenges in achieving large GHG emissions reductions from LDVs and can help policymakers develop a more informed approach to addressing GHG emissions reductions.

—Elgowainy et al.

Resources

• Amgad Elgowainy, Jeongwoo Han, Jacob Ward, Fred Joseck, David Gohlke, Alicia Lindauer, Todd Ramsden, Mary Biddy, Mark Alexander, Steven Barnhart, Ian Sutherland, Laura Verduzco and Timothy J. Wallington (2018) “Current and Future United States Light-Duty Vehicle Pathways: Cradle-to-Grave Lifecycle Greenhouse Gas Emissions and Economic Assessment” Environ. Sci. Technol. doi: 10.1021/acs.est.7b06006