Navneet R. Singh

Sustainable fuel for the transportation sector

A hybrid hydrogen-carbon (H2CAR) process for the production of liquid hydrocarbon fuels is proposed wherein biomass is the carbon source and hydrogen is supplied from carbon-free energy. To implement this concept, a process has been designed to co-feed a biomass gasifier with H2 and CO2 recycled from the H2-CO to liquid conversion reactor. Modeling of this biomass to liquids process has identified several major advantages of the H2CAR process. (i) The land area needed to grow the biomass is <40% of that needed by other routes that solely use biomass to support the entire transportation sector. (ii) Whereas the literature estimates known processes to be able to produce ≈30% of the United States transportation fuel from the annual biomass of 1.366 billion tons, the H2CAR process shows the potential to supply the entire United States transportation sector from that quantity of biomass. (iii) The synthesized liquid provides H2 storage in an open loop system. (iv) Reduction to practice of the H2CAR route has the potential to provide the transportation sector for the foreseeable future, using the existing infrastructure. The rationale of using H2 in the H2CAR process is explained by the significantly higher annualized average solar energy conversion efficiency for hydrogen generation versus that for biomass growth. For coal to liquids, the advantage of H2CAR is that there is no additional CO2 release to the atmosphere due to the replacement of petroleum with coal, thus eliminating the need to sequester CO2.

Estimation of Liquid Fuel Yields from Biomass

We have estimated sun-to-fuel yields for the cases when dedicated fuel crops are grown and harvested to produce liquid fuel. The stand-alone biomass to liquid fuel processes, that use biomass as the main source of energy, are estimated to produce one-and-one-half to three times less sun-to-fuel yield than the augmented processes. In an augmented process, solar energy from a fraction of the available land area is used to produce other forms of energy such as H(2), heat etc., which are then used to increase biomass carbon recovery in the conversion process. However, even at the highest biomass growth rate of 6.25 kg/m(2).y considered in this study, the much improved augmented processes are estimated to have sun-to-fuel yield of about 2%. We also propose a novel stand-alone H(2)Bioil-B process, where a portion of the biomass is gasified to provide H(2) for the fast-hydropyrolysis/hydrodeoxygenation of the remaining biomass. This process is estimated to be able to produce 125-146 ethanol gallon equivalents (ege)/ton of biomass of high energy density oil but needs experimental development. The augmented version of fast-hydropyrolysis/hydrodeoxygenation, where H(2) is generated from a nonbiomass energy source, is estimated to provide liquid fuel yields as high as 215 ege/ton of biomass. These estimated yields provide reasonable targets for the development of efficient biomass conversion processes to provide liquid fuel for a sustainable transport sector.

Solar Energy to Biofuels

In a solar economy, sustainably available biomass holds the potential to be an excellent nonfossil source of high energy density transportation fuel. However, if sustainably available biomass cannot supply the liquid fuel need for the entire transport sector, alternatives must be sought. This article reviews biomass to liquid fuel conversion processes that treat biomass primarily as a carbon source and boost liquid fuel production substantially by using supplementary energy that is recovered from solar energy at much higher efficiencies than the biomass itself. The need to develop technologies for an energy-efficient future sustainable transport sector infrastructure that will use different forms of energy, such as electricity, H(2), and heat, in a synergistic interaction with each other is emphasized. An enabling template for such a future transport infrastructure is presented. An advantage of the use of such a template is that it reduces the land area needed to propel an entire transport sector. Also, some solutions for the transition period that synergistically combine biomass with fossil fuels are briefly discussed.

Synergy in the hybrid thermochemical-biological processes for liquid fuel production

For a successful large scale implementation of biomass-to-liquid fuel for transportation, it is imperative that production of liquid fuel from biomass be maximized. For this purpose, synergistic processes using energy from sustainable carbon-free energy sources are needed. In this paper, we present such novel integrated processes that, when compared to the known conventional conversion methods, have potential to produce nearly three times more liquid fuel from a given quantity of biomass. The new processes treat biomass predominantly as carbon source and rely on the novel integrations to preserve carbon atoms during biomass conversion to liquid fuel. We have named such approach as hybrid hydrogen–carbon (H2CAR) process. Furthermore, we propose a novel synergistic integration between H2CAR and fermentation process where high-level heat from the H2CAR process is used to supply process heat for the fermentation process and CO2 produced during the fermentation is converted to liquid fuel using H2CAR process. This synergy leads to increase in process carbon efficiency (∼100%) and higher energy efficiency (65.7% vs. 57.2%), significantly decreasing land area requirement to produce liquid fuel compared to fermentationbased processes. Such synergistically integrated processes provide attractive opportunities for process design, operation and control.

Energy Systems Analysis for a Renewable Transportation Sector

Abstract 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 fossil-based liquid hydrocarbon fuels. Here, we present a detailed systems analysis of the transportation sector, from which emerges an energy efficient roadmap, based on the use of renewable carbon sources like biomass and atmospheric CO2, solar energy in the form of H2, heat and electricity, in conjunction with novel processes for producing liquid fuels. The proposed roadmap is illustrated using the US transportation sector as a case study.