Transportation Fuel Solutions using Renewable Energy

Rakesh Agrawal

Summary

In a fossil-fuel deprived world, it is likely that all the basic human needs will be met by renewable sources like solar energy. Among the needs, transportation offers the greatest challenges, owing to its high energy-density fuel requirements, which have traditionally been met by liquid hydrocarbon fuels derived from fossil resources. Here, we present a detailed process systems analysis, from which emerges an energy efficient roadmap, based on the use of renewable carbon sources like biomass, solar energy in the form of H2, heat and electricity, in conjunction with novel processes for producing liquid fuels. In addition, some specific transition solutions are also discussed.
The use of biomass as a carbon source for liquid fuel production is appealing, since it has the potential to offset CO2 emissions while utilizing the existing fuel infrastructure. However, generally the available biomass is limited, therefore, it is important to maximize the liquid fuel production from a given quantity of biomass. For thermochemical processes based on fast-hydropyrolysis and gasification, we present augmented processes using supplementary solar H2 and heat, capable of producing two to three times the liquid fuel yield of the conventional standalone processes.
In the transition period, when use of solar H2 would still not be cost-effective, the envisioned augmented biomass-to-liquid fuel processes can be integrated with a natural gas (NG) reformer and coal gasifier. For one configuration presented, involving a NG reformer, an estimated 45% more liquid fuel can be produced, clearly showing the synergistic benefit of the process integration.
Thus, a systematic roadmap outlining the options to supply the liquid fuel for a renewable transportation sector will be discussed.