Coal and Biomass Availability

A number of countries that typically have limited petroleum reserves have abundant coal reserves. The U.S. has abundant coal reserves. Recently EIA estimated proven U.S. coal reserves to be approximately 270 billion to 275 billion tonnes [43].

A recent NRC study estimates recoverable coal reserves at 227 billion tonnes [44]. These reserve numbers would suggest a 200-year supply of coal at current consumption rates. However, to meet increased demand will require increased mining and opening new mines, and there are environmental impacts associated with these actions. These will have to be dealt with adequately.

Biomass is a scarce resource and also a dispersed resource which raises issues of where and how it can be used best. It is "scarce" in the sense that if the most optimistic estimates of annual biomass availability (to one billion dry tonnes/year) are used to produce transportation fuel, the amount of fuel would be less than 5 million barrels/day, compared to the 12 million barrels/day of transportation fuels that the U. S. consumes [17]. Estimates of the quantity of biomass available on a sustainable basis vary considerably. Walsh et al. [45] estimated total biomass currently available in the U.S. at 460 million tonnes per year at $55/dry tonne in 1995 $ (~$75/dry tonne in 2007 $). Milbrandt [46] estimated the amount of biomass currently technically available (not considering cost) annually in the U.S. at 423 million dry tonnes per year. Perlack et al. [47] estimated over a billion dry tonnes per year of biomass technically available in 35-40 years with technology improvements. The amount of biomass that is sustainably available at an acceptable price is likely to be less then these technically feasible estimates. Estimates of the amount of biomass sustainable globally show that that biomass cannot replace a large fraction of fuel or power used on a global basis.

Furthermore, biomass will be used in a number of applications where it makes economic sense or where it satisfies policy mandates. The major options are power generation and liquid transportation fuels production both of which could be very large; but it will probably also be used in the chemicals and "petrochemicals" areas. Use of biomass in power will be driven by minimum renewables mandates for power generation and generating-unit specific mandates that a given percentage of biomass be fed along with coal. These latter mandates may be a condition imposed when the unit is permitted. For transportation fuels, minimum renewables mandates will continue to drive biomass into fuels applications. Economics should drive the route (process technologies) utilized to get it there, rather than choosing winners. There obviously are other considerations, but energy consumption is so large that economics count.

First, the limited options that exist for liquid transportation fuels production from sources other than petroleum mean that biomass-based fuels will have to be a significant component in transportation. Coal with CCS can provide liquid transportation fuels and diversity the U.S. away from petroleum, but it does not reduce GHG emissions in transportation. However, it also need not increase it; at best, it is neutral. Coal with CCS in power generation reduces GHG emissions associated with power generation. In addition, power generation has a number of options other than biomass to meet CO2 reduction mandates. More importantly, CBTL-OT has the potential to produce both carbon-free fuels and decarbonized electricity. This suggests that the use of biomass for liquid transportation fuels is an essential and probably preferred component in managing GHG emissions from the transportation sector.

If we use biomass as a component in a CO2 management strategy, it should be used where it provides the lowest cost per tonne of CO2 avoided. As shown above, the cost per tonne CO2 avoided is much lower for liquid transportation fuels production than for power generation. In addition, if we look at the demand side of transportation (vehicle options), the most cost effective option is the hybrid-electric vehicle (HEV) [48]. The HEV is about 20% less costly on an annualized basis vs. a plug-in hybrid electric vehicle (PHEV) and about 20% less costly than a 2030 normally aspirated spark-ignition vehicle [48]. If we now look at the supply-side options, the cost per tonne of CO2 is lowest for the use of liquid fuel from biomass in an HEV compared to PHEVs or BEVs using electricity from biomass with CCS.

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