Integrated biorefinery to produce biofuels and dairy products

Process integration can considerably strengthen the energy balance of biofuels (earlier post). By using by-products and residues from the production process in a 'cascading' way so they become inputs for new products or energy is a concept that will drive the design of integrated biorefineries.

Arizona-based XL Dairy Group, Inc. is building such a self-contained biorefinery designed to produce a range of products: high-grade ethanol, biodiesel, milk and dairy products, and animal feed - while all the energy used to power the refinery is derived from residues (glycerol, manure, corn bran, thin silage). The diagram (click to enlarge) offers an overview of this integration.

The US$260 million biorefinery, to be based in Vicksburg, will use proprietary technology to generate ethanol with an energy efficiency ratio of 10:1. The ratio means that for every unit of fossil fuel energy needed to produce ethanol and biodiesel, XL Dairy Group will produce 10 units

It is important to stress that this is the 'internal' energy balance of the system, which does not take into account the energy needed to grow the main input, corn, nor the feed for the cows that deliver manure from which biogas will be obtained. To compare the final energy balance of the biofuels with the energy balance of, for example sugar cane ethanol (which is between 8 to 1 and 10 to 1), one must factor in the energy inputs needed to plant, fertilise and harvest the corn as well as for the animal feed. We estimate that the final energy balance of fuels derived from the concept will then be around 3 to 1. This is twice the efficiency of a traditional dry-grind ethanol plant.

To achieve that efficiency, and generate cost savings of $0.30 to $0.35 per gallon in ethanol production and $0.50 cents per hundred weight of milk, the company will convert waste streams from the 7,500 dairy cows as well as from the fractionation, biodiesel and ethanol processes into energy to power the entire project with recycled, renewable energy.

Fractionation separates corn, the primary element in producing ethanol and biodiesel fuels, into three parts: germ, corn starch and corn bran.

"Environmentally, the project has significant advantages because of low emission of greenhouse gases through the conversion of waste streams to energy and a high energy efficiency ratio. Simply put: as the only biodiesel refinery in the nation with this level of energy efficiency, we will not be energy dependent on fossil fuels and volatile energy markets." - XL Dairy Group Chairman and CEO Dennis Corderman.

According to Corderman, the output from the integrated operation will consist of the following products:

• 54 million gallons of ethanol per year
• 5 million gallons of biodiesel per year
• 11 MW of power and 155,000 pounds of steam per hour
• 525,000 pounds of milk per day
• 110,000 tons of animal feeds per year

Located 100 miles west of Phoenix in La Paz County, construction on the first phase of the Vicksburg BioRefinery dairy farm is complete:
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The Phase II Dairy will be constructed during 2007, and final engineering is now underway on the biofuels facility which includes the fractionation mill. The project, said Corderman, will process over 576,000 tons of corn into 54 million gallons of ethanol, five million gallons of biodiesel and 110,000 tons of animal feeds annually.

Carbon dioxide produced during the process will be captured and stored on site for sale in various applications including beverage carbonation, cooling and the production of dry ice. Carbon dioxide, one of the major contributors to greenhouse gases and global warming, also can be "scrubbed" on site and converted into oxygen to be released into the atmosphere.

XL Dairy Group also is waiting for patent approval on a proprietary, low-cost algae production system, which will then be incorporated into the XL BioRefinery to lower operating costs and expand the production of motor fuels and animal feeds. "Because algae has a higher oil content than corn, and needs much less acreage to produce much higher volumes, which we will do at the site, we expect to expand to 100 million gallons of ethanol and 25-30 million gallons of biodiesel over the next five years," added Corderman.