Thoughts on 'hybrid' fuels
Does a coal-based fuel have any place in biorefining? When it’s a hybrid mix with woody biomass, there are several reasons to support such projects. In the coal-rich Appalachians, West Virginia University is working on a coal-biomass feedstock for gasification and reformation into liquid fuel. This is a focal point of a feature article in our upcoming December print issue of Biorefining.
Coal is obviously a domestic product so a coal-biomass feedstock blend for liquid fuel production would certainly improve energy security and independence issues. The fuel, derived from coal and wood, could be 100 percent domestic, as opposed to even existing biofuel blends, say B20 (20 percent biodiesel, 80 percent diesel from crude, the latter likely being imported from abroad). Additionally, there would be some transportation efficiencies and cost savings without having to ship crude oil halfway around the world. Instead we could ship coal via efficient modern locomotives from a coal mine to a local refinery. Local economic development in places like in Appalachia in the east and Wyoming in the west would also benefit.
But with coal being so rich in carbon, there are some environmental concerns. A few years ago I wrote “The Dark Alternative,” a feature article about CTL, coal to liquid fuels. This wasn’t about biomass-coal hybrids, but I learned some interesting things in producing that story. Here is an excerpt:
In well-to-wheel-or in the case of coal mines, mine-to-wheel analyses-CTL diesel fuel ought to be compared with petroleum diesel and higher-alcohol CTLs should be pitted against gasoline rather than grain-based ethanol, considering that petroleum is the target of displacement. "With gasoline, you're pumping it out of the ground, and you're getting like 80 percent of that energy going into your tank," [John] Reardon [with Frontline Bioenergy] says. "With coal, only about 50 percent will be in your tank, the carbon from which ultimately emits net greenhouse gases. The other energy will be in the process or in efficiency losses, things like that. So there's a well-to-wheel efficiency to be considered. I mean, how simple is it? You pump crude out of the ground, distill it and hydrotreat it. That's it."
To be fair, the Sierra Club doesn't support CTL or corn-based ethanol. "Right now, the calculation of the carbon impact on the environment with corn-ethanol is all over the map," Hamilton says [remember this was a few years ago]. However, Reardon says using biomass energy at a conventional corn-to-ethanol plant reduces its fossil-carbon footprint by half. The mine-to-wheel carbon release of CTL fuels-without carbon capture and sequestration-is close to double that of petroleum, Hamilton says. "None of these will require carbon capture without the [regulatory] means though, like supporters claim will happen," he adds. If further refining of C16H34-type molecules to make C2H5OH ethyl alcohols is needed, this could mean even higher amounts of carbon emissions from the plant," he says.
It will be hard for CTL projects to get their permits granted if carbon capture isn’t part of the plan, Henry says. CTL diesel fuel carbon emissions from the process smokestack and vehicle tailpipe are slightly less than those derived from petroleum diesel fuel when effective capture equipment is implemented at the plant. He also says this new generation of coal processors will view carbon dioxide as a revenue stream, and therefore, CTL plants will seek that additional income. "The first fleet of these plants will be built in and around oil fields for enhanced oil recovery (EOR)," Henry says. He cites as an example the Great Plains Synfuels Plant near Beulah, N.D., which gasifies coal into natural gas and fertilizers. Its carbon dioxide is captured and piped north to Canada, where it's sequestered underground for EOR. While carbon dioxide could be a revenue stream, the fact is that only a handful of the more than 100 U.S. grain ethanol plants view it this way. Even if the carbon was secured, there are still questions. "How long does the carbon dioxide stay in the reservoir?" Reardon asks. "Does it come back out or burp it up? Just because it's put down there, that doesn't mean it's down there forever." Does the sequestered carbon dioxide stay down there 50 years, 10 years or two years? According to Henry, the North Dakota plant's sequestered carbon dioxide has been monitored for years, with no evidence of leakage.
A WVU professor looks at it differently though. In Luke Geiver’s December feature article, titled, “Regional Work for Global Change,” he interviews WVU Prof. Singh, who says the U.S. consumes nearly 48 percent crude oil and nearly 28 percent coal to meet its energy needs, and the U.S. is the second largest producer of coal in the world. “Why can’t we substitute coal? If you add 20 to 30 percent biomass, you are tapping into that 28 percent consumption and you will reduce GHGs by the percentage of biomass you put in. It’s just another way to look at things.”
Check out the story, which is being printed next week and will be online soon.