It isn’t distiller’s fermentation. It isn’t even just a single process. It’s a combined process using both biochemical and thermochemical processes without the complications of using yeast or bacteria to get the sugars converted directly to ethanol. And it isn’t limited to just ethanol as a product output.

Cellulosic Biomass Composition. Click to enlarge.

Cellulosic Biomass Composition. Click to enlarge.

A quick review – cellulosic feedstocks are those parts of the biomass that aren’t sugars – rather its made up of cellulose, hemicellulose, lignin and the minerals which form the plant’s structure. These are very tough materials that make the bulk of the plant matter we call biomass. Of this about two thirds is cellulose and hemicellulose and one-third lignin. Of the total energy stored by the biosphere these components make up the vast majority of the energy available. Getting them converted to something more useful is the goal.

Zeachem Technology Block Diagram. Click to enlarge.

ZeaChem Technology Block Diagram. Click to enlarge.

First the ZeaChem process chemically fractionates the biomass where the sugar stream (both xylose [C5] and glucose [C6]) is sent to fermentation where an acteogenic bacteria process is utilized to ferment the sugars to acetic acid. Unlike alcohol fermentation acetic acid fermentation occurs without CO2 gas going to a waste stream. Traditional yeast fermentation creates one molecule of CO2 for every molecule of ethyl alcohol. So the carbon efficiency of the sugar’s acetic acid fermentation process is nearly 100% vs. <67% for alcohol fermentation. The acetic acid is then converted to the ester ethyl acetate, which can then be reacted with hydrogen to make ethanol or simply sold.

How to get the hydrogen? The lignin residue from the fractionation goes to a gasifier making a hydrogen rich syngas stream. The separated hydrogen is fed to a hydrogenation unit to make ethanol. The syngas fraction is combusted for heat to generate power and make steam for the process.

ZeaChem is explaining that the net effect of combining the two processes is that about 2/3s of the energy in the ethanol comes from the sugar stream and 1/3 comes from the lignin stream in the form of hydrogen. Plus they expect that a ton of fully dried biomass yielding 135 gallons of ethanol would have about enough process energy available from the syngas to make the power and steam needed drive the system.

Where did all that cellulose, hemicelloluse and mineral content go? Much of the carbon organics must be in the syngas and the minerals will come out as ash somewhere. The ZeaChem site isn’t explaining that in any detail. I’ll ask them to comment. But the process offers some substantial advantages.

Ethanol direct from corn at 150 bushels an acre yields about 96 gallons from about 4.2 tons of actual corn kernel biomass. Common cellulosic numbers available offer up to 90 gallons of ethanol per dry ton of biomass where an acre other than corn could be from 4 to as much as 20 tons per acre. ZeaChem’s process kicks the gallons per ton to 135 gallons and may well power itself. A simple doubling of the corn tonnage to 8.4 tons would then yield 756 gallons in competing technologies and ZeaChem yielding 1134 gallons. These are both far beyond anything that corn can produce using current technology.

What stands out, less the explanation of the cellulose and hemicellulose fractions, which may be an oversight, is the efficient use of all the feedstocks’ biomass fractions. If one were to postulate that 200 billion gallons of ethanol annually would substitute out the 150 billion gallons of gasoline currently used, and plants could average say 15 tons of biomass per acre you’d have a 2025 gallons per acre yield or need 988 million acres – about seven times the current corn acreage.

ZeaChem makes a point of clarifying that plants other than corn would be fully functional. A year ago ZeaChem and GreenWood Resources, Inc. signed a non-binding Letter of Intent for the supply of poplar tree (Pacific Albus) feedstocks under a long-term agreement to support the operation of an initial 1.5 million gallon per year ZeaChem cellulosic biorefinery near one of Greenwood’s Pacific Albus tree farms in the Columbia River Basin.

This likely triggered the news yesterday that ZeaChem has raised $34 million in initial Series B financing. The funding round was co-led by venture capital investors Globespan Capital Partners and PrairieGold Venture Partners with follow-on investment by MDV-Mohr Davidow Ventures, Firelake Capital and Valero Energy Corporation, the largest petroleum refiner in the United States. The new funds will be used to build ZeaChem’s first cellulosic biorefinery.

For everyone lusting to destroy corn-based alcohol with the idea that its food vs fuel it might be a happy day.

On the other hand, the most productive land on earth is the U.S. Corn Belt, owned and operated by the nation’s savviest business people. If anyone seriously thinks that those folks will overlook such an opportunity . . .

Maybe one wants to be sure that their next car is a flex fuel vehicle.


2 Comments so far

  1. Contour ABS on August 23, 2010 11:44 AM


  2. Kelly Jolin on March 18, 2011 9:27 PM

    I’m still learning from you, as I’m improving myself. I definitely like reading everything that is posted on your website. Keep the posts coming. I love it.

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