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Posts tagged “syngas fermentation”

By Robert Rapier on Oct 16, 2014 with 28 responses

LanzaTech’s Vulnerability

It’s been years since I looked at this article I wrote on LanzaTech in 2007, but today I was made aware that it’s been linked to from an article in Biofuels Digest: Junk or treasure? Looking at carbon monoxide and LanzaTech. LanzaTech CEO Jennifer Holmgren had some comments referencing my previous article that are worth addressing. So let me summarize.

LanzaTech proposes to take waste carbon monoxide from sources like steel manufacturers and ferment that to produce ethanol. Holmgren says that the bacterium they use for their fermentation, Clostridium autoethanogenum, is highly ethanol tolerant. The scientific literature mentions tolerance in the 2% to 4% range, and says that the ethanol production rate slows down beyond 4%. I did see one patent application where they mentioned ethanol via this process in the 5.5% to 6% range.

To my knowledge LanzaTech hasn’t publicly stated the ethanol concentrations they achieve, and this prevents really rigorous calculations. Holmgren states that we needn’t make assumptions since “distillation energy requirements are textbook calculations and easy to calculate.” This only true if we know the ethanol concentration in the solution being distilled. As Holmgren’s own link showed in her response, it takes nearly twice as much steam to distill a 5% ethanol solution as it does a 10% ethanol solution. But without knowing for sure what their ethanol concentration is, we can’t know the energy requirement. So, I gave an example in my previous article to illustrate my point, which is this. CONTINUE»