Prospects for Biofuels: A Review

Author(s):  
Matthew A. Oehlschlaeger ◽  
Haowei Wang ◽  
Mitra N. Sexton

Biofuels have the potential to be sustainable, secure, low carbon footprint transportation fuels. Primarily due to government mandates, biofuels have become increasingly adopted as transportation fuels over the last decade and are projected to steadily increase in production. Here the prospects of biofuels are summarized in terms of several important performance measures, including: lifecycle greenhouse gas (GHG) emissions, energy return on investment (EROI), land and water requirements, and tailpipe emissions. A review of the literature leads to the conclusion that most first-generation biofuels, including corn ethanol and soybean biodiesel produced in the United States, reduce tailpipe pollutant emissions and GHG emissions—provided their feedstocks do not replace large quantities of fixed carbon. However, their production is perhaps unsustainable due to low EROI and significant land-use and water requirements. Second-generation biofuels; for example ethanol produced from lignocellulosic biomass, have the potential for larger reductions in GHG emissions and can provide sustainable EROI with reasonable land area usage; however, they require water inputs several orders-of-magnitude greater than required by petroleum fuels. Advanced biofuels from algal oils and synthetic biological processes are further from commercial reality and require more assessment but potentially offer better performance due to their orders-of-magnitude greater yields per land area and lower water requirements; at present, the energy costs of such biofuels are uncertain.

2018 ◽  
Vol 18 (7) ◽  
pp. 4817-4830 ◽  
Author(s):  
Christina B. Zapata ◽  
Chris Yang ◽  
Sonia Yeh ◽  
Joan Ogden ◽  
Michael J. Kleeman

Abstract. California's goal to reduce greenhouse gas (GHG) emissions to a level that is 80 % below 1990 levels by the year 2050 will require adoption of low-carbon energy sources across all economic sectors. In addition to reducing GHG emissions, shifting to fuels with lower carbon intensity will change concentrations of short-lived conventional air pollutants, including airborne particles with a diameter of less than 2.5 µm (PM2.5) and ozone (O3). Here we evaluate how business-as-usual (BAU) air pollution and public health in California will be transformed in the year 2050 through the adoption of low-carbon technologies, expanded electrification, and modified activity patterns within a low-carbon energy scenario (GHG-Step). Both the BAU and GHG-Step statewide emission scenarios were constructed using the energy–economic optimization model, CA-TIMES, that calculates the multi-sector energy portfolio that meets projected energy supply and demand at the lowest cost, while also satisfying scenario-specific GHG emissions constraints. Corresponding criteria pollutant emissions for each scenario were then spatially allocated at 4 km resolution to support air quality analysis in different regions of the state. Meteorological inputs for the year 2054 were generated under a Representative Concentration Pathway (RCP) 8.5 future climate. Annual-average PM2.5 and O3 concentrations were predicted using the modified emissions and meteorology inputs with a regional chemical transport model. In the final phase of the analysis, mortality (total deaths) and mortality rate (deaths per 100 000) were calculated using established exposure-response relationships from air pollution epidemiology combined with simulated annual-average PM2.5 and O3 exposure. Net emissions reductions across all sectors are −36 % for PM0.1 mass, −3.6 % for PM2.5 mass, −10.6 % for PM2.5 elemental carbon, −13.3 % for PM2.5 organic carbon, −13.7 % for NOx, and −27.5 % for NH3. Predicted deaths associated with air pollution in 2050 dropped by 24–26 % in California (1537–2758 avoided deaths yr−1) in the climate-friendly 2050 GHG-Step scenario, which is equivalent to a 54–56 % reduction in the air pollution mortality rate (deaths per 100 000) relative to 2010 levels. These avoided deaths have an estimated value of USD 11.4–20.4 billion yr−1 based on the present-day value of a statistical life (VSL) equal to USD 7.6 million. The costs for reducing California GHG emissions 80 % below 1990 levels by the year 2050 depend strongly on numerous external factors such as the global price of oil. Best estimates suggest that meeting an intermediate target (40 % reduction in GHG emissions by the year 2030) using a non-optimized scenario would reduce personal income by USD 4.95 billion yr−1 (−0.15 %) and lower overall state gross domestic product by USD 16.1 billion yr−1 (−0.45 %). The public health benefits described here are comparable to these cost estimates, making a compelling argument for the adoption of low-carbon energy in California, with implications for other regions in the United States and across the world.


2017 ◽  
Author(s):  
Christina B. Zapata ◽  
Chris Yang ◽  
Sonia Yeh ◽  
Joan Ogden ◽  
Michael J. Kleeman

Abstract. California's goal to reduce greenhouse gas (GHG) emissions 80 % below 1990 levels by the year 2050 will require adoption of low carbon energy sources across all economic sectors. In addition to reducing GHG emissions, shifting to fuels with lower carbon intensity will change concentrations of short-lived conventional air pollutants, including airborne particles with diameter less than 2.5 µm (PM2.5) and ozone (O3). Here we evaluate how business-as-usual (BAU) air pollution and public health in California will be transformed in the year 2050 through the adoption of low-carbon technologies, expanded electrification, and modified activity patterns within a low carbon energy scenario (GHG-Step). Both the BAU and GHG-Step state-wide emission scenarios were constructed using the energy-economic optimization model, CA-TIMES, that calculates the multi-sector energy portfolio that meets projected energy supply and demand at the lowest cost, while also satisfying scenario-specific GHG emissions constraints. Corresponding criteria pollutant emissions for each scenario were then spatially allocated at 4 km resolution to support air quality analysis in different regions of the state. Meteorological inputs for the year 2054 were generated under a Representative Concentration Pathway (RCP) 8.5 future climate. Annual-average PM2.5 and O3 concentrations were predicted using the modified emissions and meteorology inputs with a regional chemical transport model. In the final phase of the analysis, mortality (total deaths) and mortality rate (deaths per 100 000) were calculated using established exposure-response relationships from air pollution epidemiology combined with simulated annual-average PM2.5 and O3 exposure. Predicted deaths associated with air pollution in 2050 dropped by 24 %–26 % in California (1537–2758 avoided deaths yr−1) in the climate-friendly 2050 GHG-Step scenario, which is equivalent to a 54 %–56 % reduction in the air pollution mortality rate (deaths per 100 000) relative to 2010 levels. These avoided deaths have an estimated value of $ 11.4 B–$ 20.4 B USD per yr−1 based on the present-day Value of a Statistical Life (VSL) equal to $ 7.6 M. The costs for reducing California GHG emissions 80 % below 1990 levels by the year 2050 depend strongly on numerous external factors such as the global price of oil. Best estimates suggest that meeting an intermediate target (40 % reduction in GHG emissions by the year 2030) using a non-optimized scenario would reduce personal income by $ 4.95 B yr−1 (−0.15 %) and lower overall state GDP by $ 16.1 B yr−1 (−0.45 %). The public health benefits described here are comparable to these cost estimates, making a compelling argument for the adoption of low carbon energy in California, with implications for other regions in the United States and across the world.


2021 ◽  
Author(s):  
Deepthi Swamy ◽  
Apurba Mitra ◽  
Varun Agarwal ◽  
Megan Mahajan ◽  
Robbie Orvis

India is currently the world’s third-largest emitter of greenhouse gases (GHGs) after China and the United States and is set to experience continued growth in its population, economy, and energy consumption. Exploring low-carbon development pathways for India is therefore crucial for achieving the goal of global decarbonization. India has pledged to reduce the emission intensity of its gross domestic product (GDP) by 33–35 per cent relative to 2005 levels by 2030 through its Nationally Determined Contribution (NDC), among other related targets for the renewable energy and forestry sectors. Further, countries, including India, are expected to respond to the invitation of the Conference of the Parties (COP) to the Paris Agreement to communicate new or updated NDCs with enhanced ambition and long-term low-GHG development strategies for 2050. To design effective policy packages to support the planning and achievement of such climate targets, policymakers need to identify policies that can reduce GHG emissions in a timely and cost-effective manner, while meeting development-related and other national objectives. The India Energy Policy Simulator (India EPS), an open-source, system dynamics model, can enable an integrated quantitative assessment of different cross-sectoral climate policy packages for India through 2050 and their implications for key variables of interest such as emissions, GDP, and jobs. The tool was developed by Energy Innovation LLC and adapted for India in partnership with World Resources Institute. It is available for open access through a Web interface as well as a downloadable application. This technical note describes the structure, input data sources, assumptions, and limitations of the India EPS, as well as the setup and key results of its reference scenario, referred to as the business-as-usual (BAU) scenario in the model. It is intended as an update to the first technical note on the India EPS (Mangan et al. 2019) and accounts for the changes incorporated into the model since the first version.


Energies ◽  
2020 ◽  
Vol 13 (16) ◽  
pp. 4251
Author(s):  
Sheng Yang ◽  
Timothy Volk ◽  
Marie-Odile Fortier

Few life cycle assessments (LCAs) on willow biomass production have investigated the effects of key geographically specific parameters. This study uses a spatial LCA model for willow biomass production to determine spatially explicit greenhouse gas (GHG) emissions and energy return on investment (EROI), including land use conversion from pasture and cropland or grassland. There were negative GHG emissions on 92% of the land identified as suitable for willow biomass production, indicating this system’s potential for climate change mitigation. For willow planted on cropland or pasture, life cycle GHG emissions ranged from −53.2 to −176.9 kg CO2eq Mg-1. When willow was grown on grassland the projected decrease in soil organic carbon resulted in a slightly positive GHG balance. Changes in soil organic carbon (SOC) associated with land use change, transportation distance, and willow yield had the greatest impacts on GHG emissions. Results from the uncertainty analysis exhibited large variations in GHG emissions between counties arising from differences in these parameters. The average EROI across the entire region was 19.2. Willow biomass can be a carbon negative or low-carbon energy source with a high EROI in regions with similar infrastructure, transportation distances, and growing conditions such as soil characteristics, land cover types, and climate.


2021 ◽  
Author(s):  
Devashree Saha ◽  
Greg Carlock ◽  
Rajat Shrestha ◽  
John Feldmann ◽  
Haley Leslie-Bole

This working paper identifies key climate policies and investments and estimates their emissions-reduction potential and associated costs, which can enable the United States to reduce economy-wide greenhouse gas (GHG) emissions by 50–52% compared to 2005 levels by 2030 and reach net-zero GHG emissions by midcentury, the goals set by the Biden administration.


Author(s):  
Michael Somers ◽  
Liaw Batan ◽  
Baha Al-Alawi ◽  
Thomas H. Bradley

Abstract The transportation sector accounts for over 20 percent of greenhouse gas (GHG) emissions in Colorado which without intervention will grow to over 30 million metric tons (MMT) of GHG emissions per year. This study seeks to develop a specific characterization of the Colorado fuel and transportation system using a customized life cycle assessment (LCA) model. The model (CO-GT) was developed as an analytical tool to define Colorado’s 2020 baseline life cycle GHG emissions for the transportation sector, and to examine Colorado-specific pathways for GHG reductions through fuel types and volumes changes that might be associated with a state clean fuel standard (CFS). By developing a life cycle assessment of transportation fuels that is specific to the state of Colorado’s geography, fleet makeup, policies, energy sector and more, these tools can evaluate various proposals for the transition towards a more sustainable state transportation system. The results of this study include a quantification of the Colorado-specific roles of clean fuels, electricity, extant policies, and fleet transition in projections of the state’s 2030 transportation sector GHG emissions. Relative to a 2020 baseline, electrification of the vehicle fleet is found to reduce state-wide lifecycle GHG emissions by 7.7 MMT CO2e by 2030, and a model CFS policy able to achieve similar reductions in the carbon intensity of clean fuels as was achieved by California in the first 10 years of its CFS policies is found to only reduce state-wide lifecycle GHG emissions by 0.2 MMT CO2e by 2030. These results illustrate the insensitivity of Colorado’s transportation fleet GHG emissions reductions to the presence of CFS policies, as proposed to date.


1995 ◽  
Vol 117 (4) ◽  
pp. 297-306 ◽  
Author(s):  
S. R. Bell ◽  
M. Gupta ◽  
L. A. Greening

Utilization of alternative fuels in the transportation sector has been identified as a potential method for mitigation of petroleum-based energy dependence and pollutant emissions from mobile sources. Traditionally, vehicle tailpipe emissions have served as sole data when evaluating environmental impact. However, considerable differences in extraction and processing requirements for alternative fuels makes evident the need to consider the complete fuel production and use cycle for each fuel scenario. The work presented here provides a case study applied to the southeastern region of the United States for conventional gasoline, reformulated gasoline, natural gas, and methanol vehicle fueling. Results of the study demonstrate the significance of the nonvehicle processes, such as fuel refining, in terms of energy expenditure and emissions production. Unique to this work is the application of the MOBILE5 mobile emissions model in the full-fuel-cycle analysis. Estimates of direct and indirect green-house gas production are also presented and discussed using the full-cycle-analysis method.


2021 ◽  
Vol 13 (18) ◽  
pp. 10371
Author(s):  
Nariê Rinke Dias de Souza ◽  
Bruno Colling Klein ◽  
Mateus Ferreira Chagas ◽  
Otavio Cavalett ◽  
Antonio Bonomi

Decarbonization programs are being proposed worldwide to reduce greenhouse gas (GHG) emissions from transportation fuels, using Life Cycle Assessment (LCA) models or tools. Although such models are broadly accepted, varying results are often observed. This study describes similarities and differences of key decarbonization programs and their GHG calculators and compares established LCA models for assessing 2G ethanol from lignocellulosic feedstock. The selected LCA models were GHGenius, GREET, JRC’s model, and VSB, which originated calculators for British Columbia’s Low Carbon Fuel Standard, California’s Low Carbon Fuel Standard, Renewable Energy Directive, and RenovaBio, respectively. We performed a harmonization of the selected models by inserting data of one model into other ones to illustrate the possibility of obtaining similar results after a few harmonization steps and to determine which parameters have higher contribution to closing the gap between default results. Differences among 2G ethanol from wheat straw were limited to 0.1 gCO2eq. MJ−1, and discrepancies in emissions decreased by 95% and 78% for corn stover and forest residues, respectively. Better understanding of structure, calculation procedures, parameters, and methodological assumptions among the LCA models is a first step towards an improved harmonization that will allow a globally accepted and exchangeable carbon credit system to be created.


2014 ◽  
pp. 70-91 ◽  
Author(s):  
I. Bashmakov ◽  
A. Myshak

This paper investigates costs and benefits associated with low-carbon economic development pathways realization to the mid XXI century. 30 scenarios covering practically all “visions of the future” were developed by several research groups based on scenario assumptions agreed upon in advance. It is shown that with a very high probability Russian energy-related GHG emissions will reach the peak before 2050, which will be at least 11% below the 1990 emission level. The height of the peak depends on portfolio of GHG emissions mitigation measures. Efforts to keep 2050 GHG emissions 25-30% below the 1990 level bring no GDP losses. GDP impact of deep GHG emission reduction - by 50% of the 1990 level - varies from plus 4% to minus 9%. Finally, very deep GHG emission reduction - by 80% - may bring GDP losses of over 10%.


2021 ◽  
Vol 13 (4) ◽  
pp. 2418
Author(s):  
Ana María Arbeláez Vélez ◽  
Andrius Plepys

Shared mobility options, such as car sharing, are often claimed to be more sustainable, although evidence at an individual or city level may contradict these claims. This study aims to improve understanding of the effects of car sharing on transport-related emissions at an individual and city level. This is done by quantifying the greenhouse gas (GHG) emissions of the travel habits of individuals before and after engaging with car sharing. The analysis uses a well-to-wheel (WTW) approach, including both business-to-consumer (B2C) and peer-to-peer (P2P) car-sharing fleets. Changes in GHG emissions after engaging in car sharing vary among individuals. Transport-related GHG emissions caused by car-free individuals tend to increase after they engage in car sharing, while emissions caused by previous car owners tend to fall. At the city level, GHG emissions savings can be achieved by using more efficient cars in sharing systems and by implementing greener mobility policies. Changes in travel habits might help to reduce GHG emissions, providing individuals migrate to low-carbon transport modes. The findings can be used to support the development and implementation of transport policies that deter car ownership and support shared mobility solutions that are integrated in city transport systems.


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