Energy Efficiency Analysis: Biomass-to-Wheel Efficiency Related with Biofuels Production, Fuel Distribution, and Powertrain Systems

BACKGROUND: Energy efficiency analysis for different biomass-utilization scenarios would help make more informed decisions for developing future biomass-based transportation systems. Diverse biofuels produced from biomass include cellulosic ethanol, butanol, fatty acid ethyl esters, methane, hydrogen, methanol, dimethyether, Fischer-Tropsch diesel, and bioelectricity; the respective powertrain systems include internal combustion engine (ICE) vehicles, hybrid electric vehicles based on gasoline or diesel ICEs, hydrogen fuel cell vehicles, sugar fuel cell vehicles (SFCV), and battery electric vehicles (BEV). METHODOLOGY/PRINCIPAL FINDINGS: We conducted a simple, straightforward, and transparent biomass-to-wheel (BTW) analysis including three separate conversion elements--biomass-to-fuel conversion, fuel transport and distribution, and respective powertrain systems. BTW efficiency is a ratio of the kinetic energy of an automobile's wheels to the chemical energy of delivered biomass just before entering biorefineries. Up to 13 scenarios were analyzed and compared to a base line case--corn ethanol/ICE. This analysis suggests that BEV, whose electricity is generated from stationary fuel cells, and SFCV, based on a hydrogen fuel cell vehicle with an on-board sugar-to-hydrogen bioreformer, would have the highest BTW efficiencies, nearly four times that of ethanol-ICE. SIGNIFICANCE: In the long term, a small fraction of the annual US biomass (e.g., 7.1%, or 700 million tons of biomass) would be sufficient to meet 100% of light-duty passenger vehicle fuel needs (i.e., 150 billion gallons of gasoline/ethanol per year), through up to four-fold enhanced BTW efficiencies by using SFCV or BEV. SFCV would have several advantages over BEV: much higher energy storage densities, faster refilling rates, better safety, and less environmental burdens

Carbon sequestration potential of the South Wales Coalfield

This paper presents a preliminary evaluation of the carbon dioxide (CO2) storage capacity of the unmined coal resources in the South Wales Coalfield, UK. Although a significant amount of the remaining coal may be mineable through traditional techniques, the prospects for opening new mines appear poor. Also, many of the South Wales coal seams are lying unused since they are too deep to be mined economically using conventional methods. There is instead a growing worldwide interest in the potential for releasing the energy value of such coal reserves through alternative technologies – for example through carbon dioxide sequestration with enhanced coal bed methane recovery. In this study, geographical information systems and three-dimensional interpolation are used to obtain the total unmined coal resource below 500 m deep, where the candidate seams for carbon dioxide sequestration are found. The ‘proved’, ‘probable’ and ‘possible’ carbon dioxide storage capacities of the South Wales Coalfield are then obtained using an established methodology. Input parameters are based on statistical distributions, considering a combination of laboratory coal characterisation results and literature review. The results are a proved capacity of 70·1 Mt carbon dioxide, a probable capacity of 104·9 Mt carbon dioxide and a possible capacity of 152·0 Mt carbon dioxide