Sorghum Readies to Advance

Drought and the U.S. EPA have given the underdog crop a big boost.
By Susanne Retka Schill | March 29, 2013

Sorghum’s natural mechanisms to resist drought shone through last year in the High Plains, reigniting interest in the well-known crop. The bigger news in sorghum circles, though, is the U.S. EPA’s determination that grain sorghum, in tandem with specified greenhouse gas (GHG) reducing technologies, qualifies as an advanced biofuel, earning the coveted D5 renewable identification number (RIN). 

Western Plains Energy LLC, of Oakley, Kan., is the first ethanol producer poised to capture the D5 RINs for grain sorghum-based ethanol. The company received its letter of determination from the EPA in late December just days before it started up its new $40 million anaerobic digester, fed by manure from nearby feedlots and other biomass. It takes several weeks for the digester to produce enough biogas to switch the boilers over and turn off the natural gas, so the company didn’t expected to register for D5 RINs in March. 

The story behind sorghum’s advanced biofuel pathway reveals much about the ethanol industry’s evolving relationship with the EPA. Sorghum growers were part of the discussions when the renewable fuels standard (RFS) was revised in 2007, explains Tim Lust, CEO of the National Sorghum Producers. In the end, getting the corn and soybean life-cycle analyses and indirect land use change impacts figured out took priority and the EPA published its rule without sorghum. “We’ll handle this in a supplement,” Lust says the EPA told the sorghum producers. “It ended up being a very long process. And, like corn and soybeans, most of our challenges came down to the indirect land use component,” he adds. Sorghum’s carbon footprint on the domestic side was very good, he continues, but, at one point, the international land use change component for sorghum was twice that of corn.  “We were able to work with EPA and with different scientists to work through the process,” Lust says.

EPA published its final determination on a pathway for grain sorghum in December, not long before Western Plains’ separate pathway was approved.  The two-year-plus wait, however, between the EPA publishing its first set of rules for RFS2 in 2010 and completing the sorghum pathway, was not a huge problem for existing producers who were grandfathered in just as corn ethanol producers were. The newly published pathways mean new dry mill facilities fired with natural gas and using grain sorghum will meet the 20 percent GHG reduction threshold to qualify as renewable fuel in the RFS. The real excitement was generated by the ruling that grain sorghum ethanol achieves a 50 percent reduction in GHG emissions to qualify as an advanced biofuel when production facilities use only biogas for process energy, utilize mostly on-site electricity production and dry 100 percent of the distillers grains. 

Western Plains joined other sorghum-ethanol producers and the National Sorghum Producers to get the EPA pathway established. With the knowledge of what would be required by the EPA for the advanced pathway, and with no plans for adding combined heat and power (CHP), Western Plains petitioned for its own pathway in September 2011. 

“We’re virtually totally wet distillers,” explains CEO Steve McNinch, which provides significant energy savings compared to the main pathway. Western Plains also collected data from a pilot-scale digester to use in its petition as construction on the Himark bioGas system proceeded. The data documented the GHG efficiencies gained both from co-location and minimal biogas cleanup involving the removal of just water and hydrogen sulfide. Western Plains uses it essentially raw in specialized burners able to compensate for gas quality and variability. McNinch explains the system eliminates several energy-intensive steps required for biogases, such as landfill gas, that must have gases other than methane removed, meet a Btu content regulation and be compressed for delivery by pipeline.

While providing its own process data, Western Plains didn’t have to start from scratch. In its letter of determination, EPA explained the Western Plains pathway built upon the feedstock modeling that was done as part of the sorghum rule along with the emissions impact modeling used as part of the March 2010 RFS rule. Modifications to the pathway were based on Western Plains’ conversion efficiency as well as mass and energy balances. The plant’s data, supplied with a confidentiality agreement, was used in the EPA’s modeling to determine Western Plains’ GHG impact achieves a 50 percent reduction compared to the baseline gasoline emissions. The EPA letter of determination and supporting comments explains that Western Plain’s better-than-average ethanol yield “results in 1 percent more Btus of fuel produced for the same amount of grain sorghum feedstock,” and goes on to describe the ripple effect in being able to scale back not only the agricultural sector impacts for feedstock production, but direct and indirect emissions. 

With the EPA approval, Western Plains has additional daily reporting requirements to verify compliance as it applies for RINs on its production. The payback for the Kansas producer comes in the added value for D5 RINs. “Last year [the RIN value] was as high as 90 cents a gallon and its low point was 30 cents a gallon,” McNinch says. The payback time for the company’s substantial investment in the anaerobic digester will depend on just where those RINs credits average out. “From pure gas alone, it will be a seven- to eight-year payback,” he adds. 

McNinch says apprehensions about working with the EPA are misguided. “The EPA has been very helpful and a willing partner. They want the industry to be successful,” he says. “Whatever fears [many in the ethanol industry] have of the EPA, I think they can set them aside. If you’re willing to be a partner with them, they’re willing to sit down and discuss what needs to be done. They were very helpful with the process.”

More Candidates

While the Kansas-based ethanol producer is the first, it won’t be the only grain sorghum ethanol producer of advanced biofuels for long.  Like Western Plains, Aemetis Advanced Fuels Keyes Inc. in California’s Central Valley sells only wet distillers grains. Unlike Western Plains, which invested in a digester for renewable power, the Praj-designed plant built in 2008 does have CHP installed. Andy Foster, president and chief operating officer, says the company expects to register for D5 RINs by midyear, initially under the EPA rule for grain sorghum as a petition for a separate pathway is prepared. 

Aemetis did a successful trial run using sorghum this past year and is working to source feedstock both internationally and domestically. The company is negotiating a supply agreement for landfill gas to power the steam turbine that generates electricity and process heat for the 55 MMgy plant. And, it is in discussions with EPA regarding other pathway requirements. 

“It may require some additional engineering studies,” Foster says. “We have CHP and how much electricity that we take off the grid is important in the EPA rule.” In the rule, the amount of electricity purchased from the grid is limited to no more than 0.15 kilowatts of electricity per gallon of ethanol produced. Foster explains that due to the sheer cost of a steam turbine, the plant doesn’t have the built-in redundancy typical for other plant systems. Thus, whenever they do routine maintenance, the plant switches to the grid. 

An engineering study to document the plant’s actual performance is under way, Foster adds. Aemetis’ long-term goal is to use the study to achieve a lower carbon intensity score for the California low carbon fuel standard and a separate pathway with the U.S. EPA. While landfill gas is available, he explains, it is expensive and the company anticipates other efficiencies, once documented, will permit a much lower percentage of biogas usage. Aemetis is considering other technologies further down the road, such as using a biomass boiler.

Pacific Ethanol Inc. also used grain sorghum for the first time in 2012 and is  aiming towards producing advanced biofuels at its 60 MMgy Stockton, Calif., plant, but expects it will take more time than its neighbor in the Central Valley. “There are some hurdles to overcome,” reports Paul Koehler, vice president of corporate development. The company expects to gain yield and energy efficiencies when Edeniq Cellunator technology is brought online midyear, but it will also need to consider CHP and biogas. “There are a number of dairies in the region that would provide manure for biogas,” he says. “And we feed a lot of those cows.”

In the plains, Chris Standlee, executive vice president, reports Abengoa Bioenergy is evaluating the possibility of producing advanced biofuel. Its plants in Colwich, Kan., and Portales, N.M., have long histories of using grain sorghum almost exclusively, he says, and other facilities are being evaluated as well. 

Twelve to 17 U.S. plants routinely use sorghum, says Lust, of the National Sorghum Producers. Of those, Kansas Ethanol LLC, Nesika Energy LLC and Conestoga Energy Partners LLC, which has three plants in Kansas and Texas, are some examples of those seriously considering pursuing the advanced biofuels pathway. “Each plant is going to have to look at the pathway and break the numbers down and see what the value is,” he adds.

Author: Susanne Retka Schill
Contributions Editor, Ethanol Producer Magazine
[email protected]


Sweet Progress 

Mick Henderson has gotten a good look at how sweet sorghum juice might be integrated into the corn ethanol process. Coming in at about 12 percent BRIX (a measure of sugar content), an 80,000-pound truckload displaced about a third of a truckload of corn in the process at Commonwealth Agri-Energy LLC, a 33 MMgy plant in Hopkinsville, Ky. Sweet sorghum sugars are fermentable as is, but with the concern that bacteria or wild yeast may come in with the juice, the plant’s general manager says they added it at the liquefaction phase to sanitize. The juice performed as expected, Henderson adds, with close attention paid to both sugar content and water balance. He’s ready to try more. “I said, ‘Next year, get me 30 truckloads in 30 days or less.’” 

Commonwealth’s partner in the experiment, Delta BioRenewables LLC, of Memphis, Tenn., is aiming to diversify the region’s agriculture base and create new businesses in the mid-South. Creating a new industry is no easy task. Delta BioRenewables is simultaneously working on sweet sorghum variety trials, agronomics and processing technology as well as providing samples to potential end users. The company’s model is to recruit enough farmers to grow between 2,500 and 5,000 acres in proximity to facilities manufacturing renewable fuels, biobased products or specialty foods. The company has potential partners in seven states, says Pete Nelson, director of business development.

As the manager of a farmer-owned cooperative, Henderson says, “I’m not out to displace corn acreage, but we have marginal acres where the sweet sorghum crop might work out well for the farmer.”  He can envision sweet sorghum processing being co-located with the ethanol plant, with sweet sorghum juice providing both sugars and water for the facility. “I’ve only talked 5 MMgy [ethanol from sweet sorghum] for a plant our size,” he says. “That’s like 2,500 acres and that’s a good place to start with the farmers.”

Just how quickly sweet sorghum could take off will depend upon whether it achieves an advanced biofuel designation from the U.S. EPA. The National Sorghum Producers expects to complete the EPA petition by late spring. While it would appear easily analogous to Brazilian sugarcane, an already designated advanced biofuel, sweet sorghum has unique issues. Sugarcane’s rating depends partly upon the burning of the bagasse for power and heat. The target market for sweet sorghum bagasse is feed, which requires documenting its feed value and the displacement of other crops for the lifecycle analysis. Sweet sorghum currently yields about 20 tons per acre on nonirrigated land, Nelson says, and university analyses indicate it should yield about 500 gallons of ethanol per acre. He adds that new varieties in development are boosting yield expectations closer to 30 tons per acre.      

Delta BioRenewables isn’t the only one working on sweet sorghum-to-ethanol. In Florida, Southeast Renewable Fuels LLC is expecting to break ground this spring on a long-planned 20 MMgy plant in Clewiston, Fla. The company had hoped to break ground in 2009 on the first of three plants in the region with a goal of 100 MMgy of capacity.


Mule vs. Quarter Horse

 Sorghum’s performance in high heat and drought has many taking a second look, explains Ismail Dweikat, sorghum geneticist at the University of Nebraska-Lincoln. Sorghum goes into dormancy under severe drought and has several mechanisms to conserve moisture while waiting for rain. It will generate more roots in dry conditions to enhance the plant’s ability to search for water. It has wax on its leaves and stems to reduce moisture loss, as well as narrow leaves and the ability to fold the leaves in on themselves—all strategies to conserve moisture in both heat and drought stress. Sorghum has other positives, including a seed cost at a fraction of corn’s and its low water requirement, a plus in places where water for irrigation is costly or scarce. “If you classified crops like animals, corn would be like a quarter horse that would run and run until it runs out of water, then die,” says Steve McNinch, CEO of Western Plains Energy LLC, which has used grain sorghum for years. “Milo is more like a mule. It will actually sit and wait for moisture. It has to rain for it to finish but it not only likes heat but it needs heat.” 

The Kansas corn crop was devastated by high heat during the critical pollination period last year—temperatures topped 117 degrees Fahrenheit, McNinch says. Heat isn’t an issue for sorghum. “On a really wet year, sorghum isn’t going to yield like corn. But on a normal year or below average year, sorghum is going to perform better than corn.” In Kansas, the starch levels in locally grown corn are not as high as in the heart of the Corn Belt, McNinch explains, and given sorghum’s usual discount to corn, it is a cost-effective feedstock. Sorghum and corn perform the same in the ethanol process, he adds, with the main difference being the addition of a third enzyme, a protease to treat tannins. “We’ve never been able to measure a difference in conversion rate,” he says, adding that there is a slight difference in the protein levels of the resulting distillers grains. The two grains are so similar, in fact, that Western Plains stores them in the same bin.