Two news items have appeared on the general subject of coke and coal with respect to biomass and fuels. Both are worth a look.
The first one comes from the Air Force, which has for some time been investigating Coal-to-Liquids as a source of alternative fuels at scale — and lately has looked at a hybrid of coal, biomass and carbon capture. The Connecticut Center for Advanced Technology has authored a report, here.
In the second, the National Science Foundation has issued a 3-year, $330 grant to investigate zeolite catalysts in their interactions with biomass.
Let’s take that second one first.
Santa’s deliveries on the coke front
Bottom line, zeolite is a vital material for catalytic strategies for converting biomass to liquid fuels. Why zeolite? They feature uniform arrays of tiny, molecule-sized pores with the right size and shape to convert the hydrocarbon molecules that make up petroleum into high-octane gasoline. Something that UMass-Amherst researcher Scott Auerbach terms “shape-selective catalysis.”
It’s the same reason that zeolite-inspired synthetic catalysts has been king at petroleum refineries since the 1970s. These shape-selectors cut the long-chain hydrocarbons in crude oil down to the shorter chain-lengths of gasoline.
Zeolite catalysts have been used in biomass. A problem seen for a long time in petroleum, and even more acutely in biomass, is coke formation. Side reactions in refining “can deactivate zeolite catalysts by clogging their microscopic pores, like enveloping a sponge in plastic wrap, shutting down the refining process,” the UMass-Amherst research team observes.
And we’ve seen high catalyst death rate plaguing projects like KiOR. Anellotech is using them as well — based on technology originally developed at UMass-Amherst, not coincidentally. More on advances in catalyst reactivity and selectivity, BTW, right here.
“We could turn off the chemical pathways that lead to coke if we knew what they are, but we don’t,” says Auerbach. “If we can discover how the undesirable coke molecules are formed, we can imagine ways to block them.”
The process is complex, so they’re starting with the end product — the known coke molecules that are forming — and working backwards. Auerbach plans to apply computational chemistry, using computers to reveal the microscopic structures and motions of molecules, to understand how carbohydrates react in zeolite pores. “Computational chemistry provides the most powerful microscope known to humanity, revealing the atomic dance of making fuels,” he says.
PNNL and Utrecht University are also working on a project to understand chemical transformations occurring within zeolites. More on that here.
Over to Santa’s deliveries on the coal front
So, now, onto that other news item, based on the Air Force’s work on coal-to-liquids.
Why coal and biomass? CCAT opines:
“Coal is mined in more than 50 countries with the U.S. controlling the largest coal reserves in the world. Technologies for converting coal into liquids are mature today, as evidenced in South Africa where coal has been used to make liquid fuels for the last 60 years. The use of domestic feedstocks, such as coal and biomass, offers a degree of energy security and can decrease U.S. dependency on petroleum imports.”
OK, so here are the challenges. Carbon capture is expensive, biomass and coal mixes are well established for power generation through combustion, but this is F-T conversion — much more sensitive. Plus, F-T generally works economically only on massive scale — not always well aligned with the small-scales that work for biomass.
The good news. If you can get coal and biomass into a somewhat homogenous feedstock state, F-T is a proven technology, and the military certainly needs the fuel.
It’s been a detailed and worth effort.
As CCAT reports:
“The Project Team executed gasification testing and analyses of 150 coal-biomass feedstock tests. Testing was performed with partners and facilities at Energy and Environmental Research Center (EERC), U.S. Department of Energy National Carbon Capture Center (NCCC), Westinghouse Plasma Corporation, ThermoChem Recovery International, Inc., and Emery Energy Company. Analyses for technical feasibility and commercial viability were performed by the Project Team and subject matter experts.”
The good news on emissions? Life cycle analysis results indicate that all cases satisfy Section 526 when up to 90 percent of CO2 emissions are captured and stored.
Scale of plant.
Using test data, the Project Team and NETL performed Life Cycle Analyses (LCA) and techno-economic modeling for a commercial-scale, 50,000 barrel-per-day CBTL plant to address Section 526 CO2 emission requirements and commercial viability. This scale CBTL plant will satisfy the stated alternative jet fuel needs of the USAF for non-contingency operations.
30% biomass – 38-62% below the baseline
10% biomass – 13-33% below the baseline
0% biomass – 2-18% below the baseline
Using the techno-economic model for a 50,000 barrels-per-day CBTL plant with an entrained flow gasifier or transport gasifier showed average required selling price (RSP) of jet fuel (on a crude oil equivalent basis) ranged from approximately $134 to $170 per barrel. That translates into $3.19 – $4.05 per gallon.
The Bottom Line
The economics are off, but not wildly so. There was a time a few years back when this was right on the viability bubble when Brent crude was priced at $135. That was then, this is now. We suspect that carbon capture and use is the answer — as opposed to carbon capture and storage.
One helper? As CCAT observed in its write-up, “Alternative financing, based on a government DOE loan guarantee scenario (40 percent equity, 4.56 percent interest) rather than private financing (50 percent equity, 8.00 percent interest), can result in approximately a 23 percent per barrel reduction in the required selling price.” So, think in the $2.45-$3.11 per gallon range, in that scenario — overall, that’s promising.
The project team notes the need for “mproved gasification efficiency for utilizing mixed coal-biomass feedstocks, including novel gasifier designs, and increased efficiency for preparing domestic feedstock mixtures (drying, torrefying, grinding).” In other words, we’re quite a ways away from a reference design for scale.
The biggest problem we see, and it’s essentially fatal at this stage, is the scale. 50,000 barrels per day is relatively fanciful for acquiring biomass. At 70 gallons per ton of biomass, that’s 11 million tons of biomass. A radius of 100 miles would have to be utilized even for a 30% biomass mix, and you’d need something close to 200 two-ton trucks per hour hauling in biomass.
Consequently, that 1,000-3,000 ton per day plant is going to be critical in this effort, we suspect. Small-scale FT — calling Velocys, anyone?