February 21, 2007 | General

Agricultural Residuals Drive Producer-Owned Energy

BioCycle February 2007, Vol. 48, No. 2, p. 45
Farmer-owned renewable energy enterprises are increasing rapidly – with alternative fuels such as biodiesel, ethanol and distiller’s grains becoming mainstream.
Dan Lemke

MINNESOTA is home to 16 ethanol plants generating approximately 550 million gallons per year. Most of these new facilities are producer-owned. Many others are under construction or are in the planning process.
In 2005, Minnesota farmers jumped into the biodiesel market by opening three refineries that produce more than 60 million gallons annually. Minnesota also became the first state to require that 2 percent biodiesel be added to every gallon of diesel sold in the state, creating an instant market for 16-18 million gallons of biodiesel.
But producer-owned energy isn’t limited to transportation fuels like ethanol or biodiesel. A multitude of opportunities for producing electricity and heat also exist.
The Agricultural Utilization Research Institute (AURI) is a Minnesota-based nonprofit corporation that works to help develop new uses for agricultural products grown in the state. AURI also operates the Center for Producer-Owned Energy which helps in the development of farmer-driven enterprises. Not surprisingly, renewable energy development presents some of the most intriguing value-added opportunities for agriculture.
As traditional fuel prices climb, interest in renewable sources has grown as well, in large part because of economics. Agricultural products and renewable resources are beginning to compete favorably with traditional sources when it comes to cost.
The use of crop residues, ag processing coproducts and other low value feedstocks for energy is creating opportunity for farmers to increase revenue possibilities and reduce the use of petroleum-based fuels. A number of Minnesota enterprises are taking advantage of biomass sources to generate power.
Central Minnesota Ethanol Cooperative (CMEC) is a 20-million-gallon per year producer-owned ethanol plant located near Little Falls. The plant has installed a multimillion dollar gasification system to produce synthetic gas from wood waste to cut the use of natural gas. The gasifier converts about 280 tons/day of sawdust into synthesis gas, which fuels the cooperative’s ethanol production and distiller’s grain-drying facility. This gasification system allowed CMEC to cut emissions and meet air standards for less money than a natural gas system, has stabilized the plant’s energy costs and even powers a turbine that generates one-third of the plant’s electricity. In the future, the plant’s own coproducts could be used to power the plant.
Grass seed growers in northwestern Minnesota have also tested and are considering a gasification system to make use of seed screenings. Northern Excellence Growers is a group of producers in extreme northern Minnesota that raises grass seed. Each year, the growers pay to dispose of tons of chaff and screenings generated when the grass seed is cleaned. The chaff was tested in a gasifier and was shown to produce excellent syngas. Installing a gasifier would not only save the company about $40,000 in energy costs per year, it could also produce power for a nearby small town.
Perhaps the hottest topic as it relates to biomass energy is the potential for converting cellulosic materials into ethanol. While several different processes exist and are being demonstrated on a pilot scale, nothing exists on a commercial scale. Several groups, including a farmer-directed venture in southwestern Minnesota, is pushing to develop a corn stover-based ethanol plant.
Poultry litter will be the primary fuel source for a 50 megawatt plant soon to open in west central Minnesota. The Fibrominn plant is scheduled to begin operating in early 2007 providing power by burning the litter. Several plants utilizing this technology are in operation in the United Kingdom, but this marks the first plant of its kind in the United States.
Minnesota’s ethanol and biodiesel industries consume large volumes of raw commodities. They also produce large amounts of coproducts. For the ethanol industry, dried distiller’s grains are the solid remnants of the distilling process and solubles or syrup is the liquid portion. Both have energy potential value as stand-alone products.
Dried distiller’s grains contain about 8,200 Btu per pound-due mainly to its concentration of oil. The distiller’s grains are an ingredient in several pellet fuels, have been tested as a combustion fuel by industry and are being used as a biomass source for gasification. Ethanol plants with gasification systems have the potential to utilize their own coproducts to produce energy, which reduces or eliminates the need for natural gas and creates a coproducts reuse opportunity.
One Minnesota ethanol plant, Corn Plus in Winnebago, utilizes a fluidized bed furnace to use the liquid syrup as a fuel. Instead of spraying the syrup back onto the distiller’s grains and drying it, the solubles are burned in this unique furnace. Utilizing this technology has allowed the Corn Plus plant to cut their natural gas consumption by over half.
The main coproduct from biodiesel refining is glycerin. While purified forms of glycerin can be found in hundreds of products from shampoo and toothpaste to cake mixes, crude glycerin has fewer uses and will likely be flooding the market as biodiesel production ramps up around the nation. AURI will be testing crude glycerin as a potential boiler fuel. Containing nearly 7,000 Btu per pound in its crude form, glycerin may be another coproduct that finds its way into the energy supply.
In Minnesota, both on-farm and industrial digesters are in operation. Those located on farms are primarily dairy-based. The resulting methane is either burned for heat, used to produce steam to power generators that provide electricity, or captured and stored. The manure solids can then be land applied.
Several Minnesota food processing plants also utilize this technology to produce energy from feedstocks like vegetable processing waste. In most cases, these lower-value by-products would either be land applied or used as livestock feed. Methane digesters give them added value.
Among the fastest growing areas of renewable energy production in Minnesota is wind power. Hundreds of turbines dot the landscape of western and southern Minnesota where the wind profile is most positive for energy development. However, wind turbines aren’t producing energy at peak levels all the time.
AURI is working on several cogeneration projects utilizing biodiesel-powered backup generators. The generators help to produce electricity when the wind isn’t blowing as well as during peak power usage times. These projects are in the research stage, but could provide a way to maximize wind energy while providing another opportunity for biodiesel consumption.
Dan Lemke is Communications Director with the Agricultural Utilization Research Institute based in Waseca, Minnesota. His e-mail is

Sign up