I Never Cease to be Amazed
18 May, 2009 05:34 pm
Don't get me wrong, butanol is a fine fuel, and I have a special fondness for it. I would like to see it work out. But my observation is that people grossly underestimate the difficulty of economically producing butanol from biomass.
Company trying to turn waste into biofuel
Salem businessmen to turn dairy dung into butanol for vehicles
Diesel Brewing would burn dairy waste and turn it into butanol.
Butanol is mainly used as a solvent, but company officials want to use it as a renewable fuel.
If Diesel Brewing succeeds, it likely would be the first company in the world to make butanol with what's called a gasification process, said Andy Aden, a senior research engineer with the biomass center at the National Renewable Energy Lab in Golden, Colo.
Once the process is proved feasible, Raines and his team hope to build commercial-scale plants that use 100 tons of waste per day — and produce a couple million gallons of butanol per year.
Why does this amaze me? Chemical companies like Celanese (my former employer), Dow, BASF, Eastman - oil companies like BP and Shell - and numerous other companies around the world produce butanol. They have big research budgets, and they would love to find an economical direct gasification route to butanol. These companies have looked at probably thousands of catalysts, and people have spent their careers working on this problem. The challenge is that syngas (produced from gasification) doesn't like to form butanol. You can form a little bit directly, but CO (carbon monoxide) likes to do lots of things besides form a C4 alcohol like butanol.
Methanol is not a problem. You can also produce ethanol, which is what Range Fuels is planning on doing (although you almost always have methanol to deal with as well). But the selectivity falls off sharply as you go to higher alcohols. By the time you get to butanol, you are lucky if 5% of the product is butanol. More typical is 1-2%. See this NREL report for more details:
Thermochemical Ethanol via Indirect Gasification and Mixed Alcohol Synthesis of Lignocellulosic Biomass
So why does any of this amaze me? This is all known technology. It has been looked at for 50 years by multiple big companies spending untold millions of dollars. The economics simply don't work, because of the very low yields. But a small company in Oregon still got someone to give them money to work on it:
The only way Diesel Brewing could get its start was through Oregon's business energy tax credit program — one of the most robust in the nation.
The tax credit is worth 50 percent of their $1.4 million in capital costs, Stapleton said.
And then they also suggest that they will be profitable:
Raines doesn't expect to make a profit until the 100-ton-per-day plant is running.
I spent several years working on butanol, and am quite familiar with the chemistry. How butanol is typically made involves a gasification step, but then you react the syngas with propylene and hydrogenate the product. This produces normal and iso-butanol, with very high selectivity and conversion. I believe it is highly unlikely that anyone is going to economically produce butanol by gasification of biomass. The chemistry just doesn't work. Methanol or mixed alcohols? Those economics look better, and might eventually have staying power.
Source: R-Squared Energy Blog