Coal and Biomass to Liquid Fuels

James R. Katzer

Abstract Demand for liquid transportation fuels has been increasing by over 2%/year over the last two decades and is accelerating in the emerging economies which are moving to automobile ownership. Almost all liquid transportation fuels are derived from petroleum, which at the same time is coming under increasing demand pressure and price instability. A high degree of dependence on petroleum brings concerns about diversity and security as well as issues of decreasing CO2 emissions associated with the transportation sector. This chapter examines the potential to use coal and biomass to replace petroleum-derived liquid fuels and thereby to address the concerns that are associated with near total dependence on petroleum-based liquid transportation fuels. The evaluation centers on the U.S. but is easily expandable to other developed countries and the developing world.

3.1 Introduction

Global transportation depends on liquid fuels, and these are almost entirely derived from crude oil. For a number of countries, including the U.S., China, India, and Europe, there is rising concern over access to sufficient crude supply, over energy and national security, over the cost of that supply, and over diversity of the energy sources for liquid transportation fuels. In addition, there is growing concern over reducing CO2 emissions from transportation. The transportation sector contributes one third of the U.S. Greenhouse Gas (GHG) emissions, and it is likely that the transportation sector will have to do its share in reducing GHG emissions in the

The findings included in this chapter do not necessarily reflect the view or policies of the Environmental Protection Agency. Mention of trade names or commercial products does not constitute Agency endorsement or recommendation for use.

Chemical and Biological Engineering, Iowa State University, Ames, IA 50011, USA e-mail: [email protected]

F.T. Princiotta (ed.), Global Climate Change - The Technology Challenge, Advances in Global Change Research 38, DOI 10.1007/978-90-481-3153-2_3, © Springer Science+Business Media B.V. 2011

future. The conversion of coal to liquid fuels requires large energy inputs which in turn result in additional production of CO2. Therefore, coal to liquids (CTL) without aggressively applying carbon capture and sequestration (CCS) would have a negative impact on the greenhouse gas emissions balance. However, CTL offers the opportunity to reduce petroleum imports and to diversify the sources of our transportation fuel supply. As the price of petroleum and natural gas increase relative to that of coal, there will be increasing interest in the commercial potential of synthetic liquids produced from coal and also from biomass.

In 1979, the United States, anticipating increases in the price of oil to $100 per barrel, embarked on a major synthetic fuels program intended to produce up to two million barrels of oil equivalent per day of natural gas from coal and of synthetic liquids from shale and coal. A quasi-independent government corporation, "The Synthetic Fuels Corporation" (SFC), was formed for this purpose. The SFC undertook to finance approximately six synfuels projects using a combination of indirect incentives. When the price of oil fell to about $20 per barrel in the early 1980s, the need for and particularly the economics of a government-supported synfuels program disappeared; and the SFC was terminated in 1985. The SFC experience suggests the dangers of building a program around a single issue or assumption such as the future world oil price or to base it on a single goal. Today, concerns about greenhouse gas emissions, and energy security, and diversity of supply have been added to the issue of crude oil price.

This chapter focuses primarily on the thermochemical conversion of coal and/or biomass to liquid fuels. Figure 3.1 illustrates the routes for coal conversion to liquid transportation fuels. If biomass is substituted for coal, the top and bottom routes in Fig. 3.1 still apply. For biomass, liquid fuels can be produced using biochemical conversions, such as the conversion of cellulose to ethanol. This chapter addresses the biochemical routes in less detail. The conversion of coal to liquid transportation fuels will most likely involve one of two main "routes". The "indirect route" involves breaking down the coal to form low molecular weight gases which can then be catalytically converted to synthesize liquid fuels. The other is the so-called "direct route" which converts the coal to liquid products without going through low molecular weight gases as a primary intermediate. The "indirect route" gasifies the coal as the first step. This chapter evaluates the cost and performance of technologies for the production of 50,000 bpd of Fischer-Tropsch based diesel and gasoline, and 50,000 bpd of gasoline from coal produced via methanol synthesis followed by the conversion of the methanol to gasoline (MTG). The conversion of biomass to liquid fuels, and combined biomass and coal conversion to liquid transport fuels in smaller-scale plants, limited by biomass availability, is also evaluated. All of these conversions are based on gasification, and the technology cost and performance evaluations use the same cost and operational bases and assumptions used in Chap. 2 on power generation. Thus, the technology background developed for use of coal and biomass in power generation will not be repeated here. Similarly, the issues associated with CCS are the same as those associated with power generation and will not be discussed in this chapter. Because the estimates in this chapter use the same consistent cost basis, comparisons should be quite accurate.

Fig. 3.1 Schematic for conversion of coal to liquid fuels by direct liquefaction (center) and by indirect liquefaction routes (top and bottom)

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