A form of separating fluids named “perstraction” is getting on the scene with patents and experimental materials making more news and press releases. I suspect it’s a construction using the “per” from permeable and “straction” from extraction.

A definition is forming from real world research, as a separation process where a separation process is used with one side contacting a solvent, the other side’s contacting the desired migrating product. For our purposes, the membrane would have a water and alcohol broth mix on one side hoping to move the alcohol over to the solvent side. That would eliminate the high-energy heat needed to vaporize alcohol out of the broth water.

But one still has to extract the alcohol from the solvent.

The yeasts and bacteria that digest and form alcohols live in broth of water and the prepared biomass feedstock. As they live and grow the microorganisms excrete the desired alcohols. When the alcohol content gets past the organism’s tolerance level it slows growth and eventually kills the microorganism. This part of the cycle is a huge problem, which is solved by running batches and distilling off the alcohols before or just at the concentration when microorganism activity stops.

Perstraction in a developed and refined form would allow continuous production. Then adding biomass and water as alcohol is taken off could be practical. The reduction in fuel use to heat the mash broth and distill the product off would be greatly diminished so making alcohols much more energy competitive and more eco friendly.

The range of perstraction in fuels includes methanol, ethanol and butanol. A Google will turn up research in pharmaceuticals and other fields. Most recently the USDA’s Agricultural Research Service offered a paper about using perstraction in a whey permeate (a kind of milk sugar) process to make butanol. The experiments offer that recovery of the butanol would be more economical than using batch distillation, better membranes need developed while its now known that silicalite membranes developed for pervaporation can be used, and that the process as done in the lab can be adapted in existing solvent ferment systems without significant changes.

This means that perstraction will be something we’re going to need to understand. Biomass and microorganisms at high productivity could displace a huge chunk of fossil oil and gas driving down and moderating prices. As this technology gets better, stabilizes on a few competitive models and integrates into plant engineering plans, biomass to fuels could become much more common than the 10% ethanol in gasoline. Perhaps it will apply in oil extraction from algae someday also.

There is a lot of room for growth in biomass to fuel and perstraction could well be an important part of the system. There is a huge opportunity in the extraction of alcohols from fermentation broths and those that offer the lowest cost to set up and run coupled to microorganisms that eat about anything are the two things to watch as we look at what crop systems will be most effective at gathering the atmosphere’s CO2 for recycling into fuels.


3 Comments so far

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  2. government grants for women on November 8, 2010 8:38 AM

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  3. Rachelle Landau on April 5, 2011 10:09 PM

    This is a topic all-around my heart cheers, where are your contact information though?

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