December 5, 2006

Sugar Fermentation's Achilles Heel - Water

From the "Land of 10,000 Lakes" comes a cautionary report that points to an issue that will impact the explosive growth of ethanol production in the Midwest and other parts of the country. While most observers worry about soil depletion, the food vs. energy dilemma, and energy return on investment, relatively little concern has been given to the demand for water required by sugar fermentation and enzymatic hydrolysis processes in the production of ethanol. By comparison, thermal conversion processes consume very little water because they use heat to break down the molecular bonds of the feedstock.

For states like California, water could be a deal-breaker for many proposed sites unless they could mitigate their use of water.

The Institute for Minnesota-based Agriculture and Trade Policy issued a report this October that spotlights the national lack of consideration of water usage by regulatory agencies. Below are some excerpts:

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Water Use by Ethanol Plants

There are no publicly available records on water use by ethanol plants for the U.S. In a review of ethanol states, only the Minnesota Department of Natural Resources apparently has records on water use by specific plants in reference to the amount of ethanol produced. Minnesota ethanol plants report a wide range of water use, with most plants in a range from 3.5 to 6.0 gallons of water consumed per gallon of ethanol produced. Average water use has declined from 5.8:1 in 1998 to 4.2:1 in 2005, indicating that the plants are achieving greater efficiency over time.

The state of Iowa prepared a water plan in 1996. The total water use for industrial purposes was estimated to be about 108 billion gallons per year (bgy), and the report projected water use by 2015 of 120 bgy. Currently Iowa has 2,094 million gallons per year of ethanol capacity (in operation and under construction). Using the multiplier of 4 gallons water/gallon of ethanol gives 8,376 million gallons per year, or about 7 percent of the projected water use. There is the likelihood of a doubling of Iowa’s ethanol capacity by 2012, thus the potential industrial use could be up to 14 percent of the projected use. This does not necessarily indicate that state-wide water available for ethanol is in short supply, but it does show that ethanol plants will add significantly to Iowa’s industrial water use.

Midwest agriculture is built on the region’s incredible soil and water resources. Economic development is only sustainable if it strengthens, rather than depletes, these resources. Options for reducing ethanol’s water consumption include the following:
• Maintain and strengthen regulatory oversight by state and local government on the siting of ethanol plants, with special emphasis on the water supply and availability.
• Where feasible, site plants adjacent to municipal wastewater facilities.
• Look for water recycling opportunities with livestock facilities.
• Place a greater economic value on water.
• Maintain publicly available records on ethanol’s water consumption.


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6 comments:

Ubi Nemo said...

Something to keep in mind is that the Great Lakes are an NON renewable resource similar to oil in the ground. Once it's used up it's gone.

Any option that doesn't eliminate the need for water consumption in the conversion process is a non-starter.

C. Scott Miller, EDP said...

Inasmuch as biomass are carbohydrates that contain carbon, hydrogen, and oxygen, you should know that syngas fermentation can produce water as a byproduct. In essence, there is a net increase in water from drying and converting waste biostock into biofuels.

So if your sole focus of interest is preserving water, you should not object to gasification and syngas fermentation.

Ubi Nemo said...

70% of water loss is due to evaporation due to irrigation. Are you suggesting that water is a net gain including the water it takes to grow the biomass?

My readings suggest that as much as 10 gallons of water are lost for every gallon of Ethanol produced. Some use different calculations to bring the rate down to 4:1 or even 3:1, but still a net loss for water.

Seems like converting biomass may supply some small percentage of energy needs but it's not likely to grow large. I don't object to gasification, just the notion that current energy consumption can be preserved simply by substituting biomass for oil.

C. Scott Miller, EDP said...

If the biostock used for conversion does not require cultivation, then evaporation due to irrigation is not a factor. This would include ag, forestry, and urban waste.

I am all for conservation - there is more than enough waste to reduce, reuse, and recycle without negatively impacting lifestyle. But I think what we do here will be meaningless unless it is part of a global implementation of bioconversion technology.

California's recycling efforts is diverted 50% of waste from landfills. Unfortunately, waste to be diverted has grown proportionately so the tonnage being landfilled is the same.

Anonymous said...

Being a Minnesotan, I quickly noticed an error in your article. Where you claim Minnesota to be the "Land of 1,000 Lakes," we are actually known as the "Land of 10,000 Lakes." I will give you the benefit of the doubt and say you just forgot a zero since you claim to be an experienced blogger, writer, and consultant. On the other hand, wouldn't an experienced writer make sure the catch phrases he used are correct before he published an article. Thank you for the like to the original article, it was very helpful for my research.

C. Scott Miller said...

Most bloggers write articles on the fly, sacrificing quality for speed. Some are experienced writers but that isn't a prerequisite. Some use blogging programs that have spell checkers - mine doesn't.

My apologies to the great state of Minnesota (I have moved the errant decimal). I will gladly edit any story that my readers find a typo in but I can't edit comments... like the mis-keying of the word "link" as "like" in your comment.

I'm glad you sought out the original article - that makes my day!