Dropping Water Use
The results of a Google search of the words ethanol and water use are varied and interesting. Some of the information is up-to-date and lays out the industry’s dramatic reduction in water use in the past 10 years, to an industry average of less than 3 gallons of water per gallon of ethanol produced. Other articles contained dated and downright sensationalized information, pigeonholing the ethanol industry as a water guzzler.
That’s simply not the case, says Nandakishore Rajagopalan, associate director for applied research at the Illinois Sustainable Technology Center. While a few groups have either looked into building or have built an ethanol plant in a poorly chosen site where water is in short supply, the majority are located in places where there is enough water to go around. Just one negative story can paint the whole industry in a bad light, however, and that’s often what sticks in people’s minds. “They are worried that an ethanol plant will suck out all the water and leave them high and dry,” he says, adding that the truth is there are other industries that use much more water than the ethanol industry.
How much water the industry uses depends on whether the source is looking at water consumption or total water footprint, which examines the full life cycle, starting with the water (including rainfall) required to grow the crop. According to Water Footprint Network, from which the U.S. Geological Survey takes some of its water use statistics, the global average water footprint of corn is 1,222 liters of water per kilogram of corn. On the ethanol side, it estimates a global water footprint for corn ethanol at 2,854 liters of water per liter of ethanol produced—a number that is vastly larger than the water consumption figure cited by the ethanol industry. To keep that in perspective, however, the global average water footprint of beef is 15,400 liters per kilogram and the global average water footprint of chocolate is about 17,000 liters per kilogram.
Ethanol’s opponents have really blown the industry’s water use out of proportion, says Rick Schwarck, chairmen, president and CEO of Absolute Energy LLC, a 115 MMgy ethanol plant in St. Ansgar, Iowa. The water use of ethanol plants operating in northeast Iowa and southeast Minnesota is what he calls a “flea on the back of an elephant.” Absolute Energy is located in Mitchell County, which has had 13 floods and not one drought in the past 10 years. “Worrying about ethanol water usage here is like someone in Phoenix, Ariz., worrying about not getting enough sunshine in July for a good tan,” he says.
Schwarck points to information from the National Weather Service, USGS and Colorado State University to back up his data. For one thing, water consumed by crops such as corn doesn’t just disappear into thin air. It becomes part of the water cycle, which USGS refers to as evapotranspiration. This is basically the combination of water evaporation and transpiration from plant leaves. About 10 percent of the moisture in the atmosphere comes from transpiration with nearly 90 percent provided by bodies of water on the earth, the USGS says on its website.
Water Conservation Winners
It’s one thing to point out that the ethanol industry is not, in fact, the water guzzler that some have portrayed it, but that doesn’t mean the industry isn’t actively working to conserve water either. Like many other ethanol production facilities, Absolute Energy has taken steps to reduce the amount of water used in its ethanol production process. The company has employed advanced water recycling technologies, including a proprietary technology in the company’s CO2 scrubber and others, Schwarck says.
According to a 2010 report completed by Steffen Mueller of the University of Illinois at Chicago, on average, a dry mill corn-ethanol plant used 2.72 gallons of water to produce one gallon of ethanol in 2008. It also revealed that ethanol production facilities discharged an average of 0.46 gallons of water. “Our survey showed that ethanol plants have been very successful in reducing their water consumption,” he says. “The survey also indicated that many plants had plans to reduce their consumption even further.” Those are the most recent figures available and there are no specific plans to update them at this time. Currently under consideration, though, is a best-practices book to showcase all the energy and water efficiency measures ethanol plants have put into place since 2008, Mueller says.
Industry giant Poet LLC has made significant strides in achieving a 22 percent reduction in water use—or a total of 1 billion gallons—at all its facilities by 2014. The company, which operates 27 ethanol plants in seven states, announced the Ingreenuity initiative in March 2010, which is aiming for an average of 2.33 gallons of water per gallon of ethanol produced. Poet is saving water at its plants primarily by installing its proprietary Total Water Recovery process, which recycles cooling water rather than discharging it. “We believe that water is a precious natural resource and we are committed to using as little of it as possible in our ethanol production process,” says Nathan Schock, director of public affairs and corporate social responsibility at Poet.
As of May, 18 Poet ethanol plants were operating with Total Water Recovery and installation was under way at a 19th plant. “Poet plants have cut their cumulative water rate by about 770 million gallons per year, which is ahead of the pace necessary to achieve our goal,” he tells EPM. The company is closing in on its goal to install the system at all its ethanol plants, with two possible exceptions. The Poet Research Center located in Scotland, S.D., may not have the water recovery system installed because of its smaller size of 11 MMgy, Schock says. The other one is the 73 MMgy plant in Corning, S.D., which reclaims water from a wastewater treatment plant that won’t work in Poet’s water recovery process.
In addition to reducing water use at its ethanol production facilities, Poet is working to survey corn producers that deliver corn to its plants to see how much of that corn is irrigated. “Our initial findings suggest that all of the plants are located in areas with little or no irrigation and that only a small percentage of the corn that we grind comes from irrigated acres,” Schock says.
In Illinois, Rajagopalan conducted a water conservation study at Illinois River Energy LLC, a 110 MMgy plant in Rochelle. It concluded that, using easily implemented methods, the ethanol plant studied could reduce its water use by 6.5 percent to 12 percent. A more dramatic total water-use savings of 25 percent could be achieved with more innovative methods and, in some cases, regulatory changes would be required, Rajagopalan says.
The study identified opportunities to increase water-utilization efficiencies, including minimizing cooling tower waste to potentially reduce water use by up to 11 MMgy water and increasing reverse osmosis (RO) efficiency for an estimated 5 to 17.5 MMgy in water savings. Finally, it was found that there was another 4 MMgy in potential water savings if the ethanol plant reused its filter backwash water. Rajagopalan found that although current practices were to dump all backwash water into the sewer system, some of that water was clean enough to reuse within the plant. “If you actually look at the water quality at different time points, you would find, maybe the first few minutes, the water quality is really bad but after that it does look pretty good,” he says. “You are just wasting water at that point.”
Illinois River Energy has implemented several of Rajagopalan’s report recommendations and is considering others. “One of the ones we implemented right from the beginning was looking at our cooling towers and trying to optimize the cost on those,” says David Files, process engineer. By increasing the amount of RO-treated water vented to the cooling tower, the company was able to save money on chemical use, such as bleach and sulfuric acid. “We’re aiming for a good mixture of RO water and city water,” Files says. “We use about 50/50.”
Using too much city water in the cooling tower means increased ions and minerals, which cause fouled pipes and plating on heat exchanger plates, meaning lost efficiency, says Neal Jakel, general manager of the ethanol plant. The goal is maximizing the amount of times water can cycle though the cooling tower loop. Increasing the amount of RO water used to 50 percent has reduced the amount of blowdown, or water discharged from the cooling tower.
That change was “low hanging fruit,” Files says, easy to implement immediately with a quick payback in savings of both water and chemical costs. And, there are other ethanol plants out there that could easily do this. In order to evaluate it, plants just need to do a cost-benefit analysis to discover what point gives the best return on investment.
Illinois River Energy is also working on optimizing heat reclamation. Although the project has taken more time to implement, it has had a very good cost return, Files says. By expanding the use of heat exchangers, the company has been able to recover and reuse heat while also reducing the use of cooling towers, which ultimately saves both chemicals and water. “It’s kind of a cascading cycle,” he says.
Gray Water to the Rescue
One of the more difficult to implement recommendations from Rajagopalan’s report was using wastewater from nearby municipalities that would typically get discharged. The idea is not new. Tharaldson Ethanol LLC, a 153 MMgy ethanol plant in Casselton, N.D., has been using treated wastewater pumped in from Fargo, N.D., since the plant was built. The $15.3 million project included building a wastewater treatment plant and installing 26 miles of underground pipelines. About 15 percent of the water used at the ethanol plant is piped back to Fargo as gray water, where it is retreated to drinking water standards.
The former Levelland Hockley County Ethanol LLC ethanol plant, renamed Diamond Ethanol LLC after being purchased at auction by Palmer Energy in mid-May, began utilizing city wastewater for its water needs when the 40 MMgy plant began operations four years ago, Rick Osburn, city manager, tells EPM. The company went bankrupt and put the Levelland, Texas, plant in cold idle in December 2010 but is expected to be restarted by its new owners, a company formed by Conestoga Energy Partners LLC. Although the city has an adequate supply of water, it wasn’t “comfortable” selling the ethanol plant city drinking water, considering the plant would need up to 10 MMgy of water monthly at full capacity, Osburn says. Instead, about $70,000 in grant money was used to build a 3-mile pipeline so the ethanol plant could utilize city wastewater. The ethanol plant paid for the needed water filtration system, plus it purchases a small amount of city water for things like drinking and eye wash stations on a separate meter and water system, he says.
Using city gray water is a good way to conserve water, Jakel says, adding that it’s something the Illinois River Energy is currently investigating. There are two major roadblocks, however. The first is that the majority of ethanol plants are located in rural areas with their own on-site wells. Not many ethanol plants “have the luxury” of being co-located next to a city that could supply them with both freshwater and gray water. “It’s probably only a handful, probably only less than 20 or 25 max,” he says.
Cost is also a big factor. Unlike the plants in North Dakota and Texas, both located in areas where getting access to water would have been challenging or impossible, Illinois River Energy has access to plenty of low-cost water. A gray water project would require an additional treatment facility and a 3- or 4-mile pipeline to be built under a major highway, a river and railroad tracks. Such a multimillion dollar project is hard to justify when the $40,000 currently paid monthly for water is considered. “We need to have a driver here,” he says, “like some sort of tax incentive or grant to help augment the investment.”
On the plus side, the treated water could be used for both fermentation and cooling towers. That would add up to a significant amount of well water displacement, considering that nearly 65 percent of the plant’s water use is for cooling tower water. There are some additional boxes to check, including looking at the possible impact to the plant’s permit for the vapors released from the cooling tower, as well as coming up with a cost estimate. “By the end of this year we hope to have a final decision,” Jakel says, adding that the company is hoping for public/private cooperation to make the project happen.
Corn-ethanol plants aren’t the only ones that could use treated effluent water to reduce the amount of water consumed. Currently, Rajagopalan and other researchers are working on a study that shows it is feasible to reduce the water consumption of cellulosic ethanol production with the use of treated effluent water and other water-saving methods. Cellulosic ethanol production is expected to use 6 to 10 gallons of water per gallon of ethanol produced. “There is even more interest in seeing if we can conserve water in those operations,” Rajagopalan says.
Author: Holly Jessen
Associate Editor, Ethanol Producer Magazine