Fuels play a critical role throughout our economy. In 2013, fuels directly supplied about 99% of the energy needed by our national transportation system, 66% of that needed to generate our electricity, 68% of that needed by our industry, and 27% of that needed by our buildings. For the purposes of this Quadrennial Technology Review (QTR), a “fuel” is defined as a carrier of chemical energy that can be released via reaction to produce work, heat, or other energy services. Fuel resources include oil, coal, natural gas, and biomass. The source and mix of fuels used across the sectors of the energy system is changing, particularly the rapid increase in production from unconventional oil and gas resources.
This chapter considers three primary fuel pathways—oil and natural gas, biomass, and hydrogen, their associated technology and industrial ecosystems, and the economic, security, and environmental challenges they face. For each, current technology is reviewed and key RDD&D opportunities are identified that could help resolve their challenges. In the oil and gas sector, the primary Federal role in research is related to prudent development of these resources. Biofuels require RDD&D across the entire value chain, from resources through conversion to a variety of refined products. Hydrogen can be produced via a variety of industrially proven technologies from fossil sources such as natural gas, but further RDD&D is needed to reduce the cost of producing hydrogen from renewable, low-carbon resources. Hydrogen’s other challenges include on-board storage cost, lack of transmission and distribution infrastructure, and fuel cell cost and durability, as well as economic scale-up across the entire value chain. The chapter concludes with a brief survey of additional fuel pathways (coal and biomass to liquids, dimethyl ether, ammonia, etc.), each of which has intrinsic technological merit, but all of which also face challenges.