This, however, does not take into account the entire life cycle of the product.

As interest in the use of coal to produce diesel waxed in the early 21st century, the EPA models showed that FT diesel, on its face, produced carbon dioxide at rates a little higher than petro-diesel.  However, the EPA cautioned, more study is needed to look at the entire life cycle of FT diesel, because the process to generate it was known to be a high-carbon emission process.  It asked the Department of Energy to review the process and generate a report about the energy alternatives available.

The DOE did this, and produced a report called Life Cycle Energy and Greenhouse Gas Results of Fischer-Tropsch Diesel Produced From Natural Gas, Coal, and Biomass.  It came out in May of this year.

Coal is a carbon-intensive substance.  It is the most carbon intensive of all the fossil fuels, and the carbon molecules are released eventually somehow.  Burning coal produces far more CO2 than burning natural gas, gasoline, or even oil.  The precursor to FT diesel, also called syngas, can be produced from a variety of feedstocks, including natural gas, coal gasification, biomass gasification, and heavy refinery products such as pet coke through gasification.

The carbon in each of these feedstocks does not go away during the process of making the syngas.  And since carbon sequestration does not yet exist in anything but experimental form, carbon dioxide from each process is released to the atmosphere.  Carbon dioxide is, of course, a greenhouse gas linked to global warming.

In early 2007, the studies, which had been conducted by Argonne National Laboratory in Illinois, were complete.  The results were released at a meeting of the Society of American Engineers, many of whom were active in coal gasification technology, on May 7.

The life cycle analysis took into account the recovery of the coal, including all the machinery needed to mine it and transport it to the location where it would be processed; the cleaning and processing of the coal; coal gasification and syngas synthesis; and the transportation of the resulting FT diesel fuel to the refueling stations, such as gas stations across the world.

Two scenarios were considered.  One was a relatively low-efficiency plant (47.4%); the other was a high-efficiency plant (52%).  The proposed gasification plant in Wiscasset falls somewhere between the two.  These were compared to gas to liquid (natural gas burned in automobiles) and biomass to liquid (a gasification technique involving non-fossil fuels, such as trees, and a second process involving used cooking oils). When accounting for the whole life cycle of the product, both the low-efficiency and high efficiency coal to liquid (CTL) diesel products used more energy to produce than either gasoline, diesel, or natural gas.  This was true whether carbon was eventually captured and sequestered or not.

The product used slightly less energy than the biomass gasification diesel product, but nearly all of its energy needs were met by fossil fuels - coal, natural gas, or oil - unlike the biomass product which used next to no fossil fuels.

When looking at the output in terms of CO2, and other greenhouse gases, the difference was even more pronounced.  Gasoline puts out 100,000 grams of greenhouse gas emissions per million units of energy (BTU), as does petro-diesel.  Natural gas puts out slightly more than that.  But whether the gasification plant was low or high efficiency, output for a non-capturing and sequestering coal gasification plant FT diesel product, over the course of its lifetime, was between two and three times (200,000 - 250,000 grams) the emissions from gasoline or diesel. 
Even if the plant does capture and sequester its carbon ... and sequestration technology does not currently exist except experimentally ... the greenhouse gas emissions are still higher than gasoline and petro-diesel.

According to the EPA in their white paper, Greenhouse Gas Impacts of Expanded Renewable and Alternative Fuels Use, published in April of this year, FT diesel without carbon capture and sequestration would produce 118.5% more greenhouse gas emissions (GHG) than gasoline or diesel.  Even with capture and sequestration, the figure is still higher than petro-diesel - 3.7% more greenhouse gas in the atmosphere.  Other alternatives - compressed natural gas, biodiesel, ethanol, to name a few - produce far less than gasoline or diesel.

According to Scott Houldin of the Twin River Energy Center and Point East, “it is very important to note that TRE Center is a co-production facility generating electricity and producing clean diesel fuel simultaneously,” he said in his commentary in the Wiscasset Newspaper, dated August 23.  He further stated that the plant would utilize “both coal and wood biomass feedstocks” to generate both electricity and produce syngas, which would be processed into FT diesel.  However, most of the feedstock would be coal, not biomass. 

The plant’s diesel output is not expected to be high - perhaps 9,000 barrels per day.  Steve Hinchman of the Conservation Law Foundation refers to the small amount of co-produced FT diesel as ‘window dressing’.  “Of all alternative transportation fuels,” he said, “FT diesel is by far the dirtiest (in terms of climate impacts) of all fuels currently being evaluated worldwide.  This is without carbon sequestration, which is not currently possible and will likely never be possible in Maine due to our geology. Nonetheless, even with sequestration, the EPA concludes that FT diesel is still almost 4% worse than petro-diesel. In other words, no matter how you look at it, FT diesel is a major step backwards.”

Geology that would be favorable to carbon sequestration would include regions with salt mines, which provide a non-permeable “roof” underground.  Maine’s geology is primarily fractured bedrock, through which carbon could easily escape into the atmosphere.  The closest location for carbon sequestration would be the Sable Island oil fields in Canada, which would require transportation by tanker or pipeline, if Canada were willing to accept the carbon produced by Maine.