Easy to Digest

Energy independence and sustainability are the guiding principles of the EnviroPlus process. Two British Columbia-based innovators are using that credo to introduce a revolutionary and wide-ranging anaerobic digestion process to the fuel ethanol industry.
By Dave Nilles | June 01, 2006
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Five years ago, Richard Marshall and Alexander Kopp set their sights on the fuel ethanol industry. With a grandiose vision and plenty of know-how, they hatched a plan that they then believed—and still believe—could revolutionize even the most basic standards of the ethanol industry.

Flash forward to today. Marshall and Kopp—and their unique anaerobic digestion process—may be on the precipice of opening the door to energy independence even wider. By utilizing and updating proven technology, Marshall and Kopp's EnviroPlus process may allow both new and existing ethanol facilities to become fossil-fuel free and energy independent through the creation of "green" power.

While anaerobic digestion isn't exactly brand new to the industry—Heartland Corn Products in Winthrop, Minn., has used the process in a bio-methanator at its ethanol plant since 2001—it hasn't been applied with the magnitude and promise in which Marshall and Kopp envision. They believe their process can lessen feedstock and energy risks while providing a solution for the distillers grains glut expected to occur when an additional 3 billion gallons per year of ethanol enters the market within the next two years. As Marshall says about the EnviroPlus process, "The only downside is … there is no policy in place making ethanol plants energy independent."

Adjusting to Ethanol
The Canadian federal government's Ethanol Expansion Program can be credited for kick-starting the ethanol industry in that country. Marshall and Kopp also credit the program with opening the door for the EnviroPlus process. The program forged the partnership leading to anaerobic digestion of stillage. Kopp is now president and CEO of British-Columbia-based Econcept Bio-Energy Corp. Marshall is vice president of R&D.

The EnviroPlus process is actually quite simple, but its benefits are numerous. Marshall says an ethanol producer could get up to nine value-added coproducts. The process begins where the whole stillage would normally be discharged into the evaporators. Instead, the stillage is pumped into anaerobic digestion tanks, bypassing the evaporating and drying process that creates distillers grains.

The anaerobic digestion process does not dry the grain slurry, but rather ferments the grain in a series of vessels to generate vast quantities of biogas. This gas consists of approximately 65 percent methane and 35 percent carbon dioxide. There are several options for the gas, both of which provide great paybacks to the ethanol facility.
If an additional gas turbine is installed, the methane can be used to produce "green" power for the ethanol facility to operate. Marshall and Kopp believe the EnviroPlus process provides enough power to completely eliminate the ethanol plant's traditional energy needs. The generation facility will produce up to 66 percent more electricity than the ethanol facility requires, according to Marshall. In addition, the turbine exhaust gases generate all the steam needed for the ethanol facility. "We require no outside energy—no outside gas or steam," Marshall says. "We generate everything internally."

The biogas that is not turned into electricity can be scrubbed to pipeline-spec natural gas, compressed and injected into the existing natural gas distribution grid. The gas sales can then be established on a net metering system through which the distribution lines are used as the storage system. "We realized the generation of power from green sources was a lucrative business," Marshall says.

The anaerobic digestion process is exothermic, so the excess heat could also be utilized in a greenhouse or for general heating purposes.

Small amounts of ammonia are also produced, which could be reused in the ethanol production process. The remaining liquid is filterable into potable water.

Kopp says the remaining solids can be used as an organic dry or liquid fertilizer. Approximately 25 percent of the grain will end up as the fertilizer, which can be customized for varying applications. An idealized vision has a corn farmer hauling a load of grain to a cooperative-owned ethanol plant and leaving with a load of environmentally friendly fertilizer.

Carbon credits can also be claimed with the EnviroPlus system. A 40 MMgy plant can produce 360,000 tons of OC2e-credits, which can be scrubbed and sold into various markets, such as enhanced oil recovery. "If you compare conventional plants with the EnviroPlus model, you more than double your [OC2e-credits] credits," Kopp says.

A Perfect Match for Ethanol
Anaerobic digestion works with many feedstocks, but few are as ready for the process as thin stillage. The first advantage with stillage is the fermentation process conducted prior to its introduction to the anaerobic digestion tanks. This reduces retention time in the digestion tanks and improves the methane gas yield. Essentially, the bacteria have a much easier time breaking down—or digesting—the feedstock. Kopp compares the bacteria used in anaerobic digestion to those inhabiting a cow's stomach.

Typically anaerobic digestion takes place in as long as 20 to 30 days. The EnviroPlus system, which has a series of tanks set up in a continuous batch system, takes as little as 10 days. The consistency of the feedstock plays an important role. The bacteria in the system become more specialized when exposed to the same feedstock day in and day out, therefore becoming more efficient at digesting corn stillage.

The most important aspect is the temperature of the stillage. Anaerobic digesters, particularly the thermophilic design used in EnviroPlus, require a specific temperature range for the bacteria to function properly. To get this temperature in a conventional anaerobic digester, the feedstock must be heated to approximately 130 degrees Fahrenheit, creating significant energy costs. The ethanol whole stillage slurry is over 200 degrees Fahrenheit. Through the use of a heat exchanger, cool water is introduced to lower the stillage temperature for anaerobic digestion. At the same time, the stillage warms the water for use in the ethanol process.

Creating a Showcase
Marshall and Kopp plan on implementing the EnviroPlus system commercially at Okanagan Biofuels in Kelowna, British Columbia. Kopp is president of Okanagan, which consists of an existing 12 MMgy distillery with an 80-car rail siding. They hope to begin construction this fall on the project, which they hope will be a showcase of the EnviroPlus process. "Eighteen months from now, we should be the first energy-independent biofuels facility in the world," Kopp says.

Natural Resources Canada awarded the project funding in 2004. Long Beach, Calif.-based Earth Tech is slated to be the project's EPC contractor.

The project is expected to display the functionality and adaptability of the EnviroPlus process. Marshall says EnviroPlus can be adapted to any existing ethanol facility. Environmental permitting isn't expected to be an issue since there is no wastewater discharge, and no dryer or evaporator emissions.

The system's flexibility may be especially appealing for existing plants. The process allows the plant to bypass the distillers grains handling system. However, at any time, the feedstock can be diverted to or from the anaerobic digestion system, allowing the plant to choose anaerobic digestion or distillers grains, depending on market conditions. Marshall says an expanding facility could add only the anaerobic digestion process instead of additional dryer capacity. "It is modular, so you can build it up a piece at a time," he says.

The system alleviates dryer emissions, allowing ethanol plants to expand without worrying about emissions issues. That may also appeal to ethanol plant opponents since the noise and emissions associated with a dryer system are eliminated.

Building the Future
With all the apparent advantages of anaerobic digestion of stillage, why hasn't it already been introduced to the industry? In fact, there are several reasons. The first, understandably, is cost. Kopp says the anaerobic digestion process could cost as much as 30 percent of the existing ethanol facility. An additional power plant would potentially double that cost, but it could be offset by the new revenue streams.

Changing energy prices also factor into the equation. Five years ago, it wasn't uncommon for the kilowatt price of electricity to be as low 1 cent in the United States. That's about the time Marshall and Kopp first discussed their process with U.S. ethanol producers. In fact, J.R. Simplot already flared biogas from its potato-waste-to-ethanol facility. However, with such low electricity prices, the appeal of adding anaerobic digestion with power generation wasn't necessarily worth the capital costs. With energy costs going nowhere but up, anaerobic digestion of stillage becomes more plausible.

The ability for an ethanol plant to create its own energy—and even excess to sell into the grid—is certainly eye opening. Marshall considers it a paradigm shift. "We are no longer an ethanol plant and no longer an anaerobic digestion plant," Marshall says. "We are a biofuels energy facility."

That distinction may light up the eyes of potential financiers. The potential for long-term power or gas off-take agreements provides the leverage needed to secure financing. "We're using proven technologies here," Marshall says. "It's just the integration and using this particular feedstock that is the big benefit."

Feedstock independence also helps alleviate corn supply issues. "In our process, it doesn't matter if you use potatoes, sugar beets or millet," Kopp says. "It is feedstock independent."

Off-spec grain and other low-quality feedstocks take the pressure off of relying on the commodity markets.

The final tantalizing issue is the net energy aspect. Kopp says the net energy value of ethanol increases significantly with the EnviroPlus process. Combining the decreased energy needs with the sales of green electricity, Kopp says the EnviroPlus model offers a net energy gain of 138 percent, compared to the conventional ethanol process. "With EnviroPlus you become an energy player—not a distillers grains handler," Kopp says. EP

More information about Econcept Bio-Energy Corp., and the EnviroPlus process, can be found at www.econcept.info. More information on Okanagan Biofuels can be found at www.okanaganbiofuels.com.

Dave Nilles is an Ethanol Producer Magazine staff writer. Reach him at dnilles@bbibiofuels.com or (701) 373-0636.