A new technology integrates cattle and an ethanol plant into a so-called closed loop system that also produces energy required for the thermal needs of the plant and fertilizer for crop production.
The technology is on display on a farm adjacent to the University of Nebraska research farm, in Mead, Neb. According to Patrick Tracy of Prime BioSolutions in Mead, the company that has patented the technology, the cores of the facility are a 30,000-head cattle operation and a 25-million-gallon ethanol plant.
Tracy told attendees of the National Alliance of Independent Crop Consultants in Seattle, Wash., that the facility captures about 12,000 pounds of actual nitrogen per day, enough to treat about 10,000 acres based on 1.2 pounds per acre needed per bushel of corn. It also produces about 12,000 pounds of phosphorus and 9,800 pounds of potassium per day.
The technology is known as an integrated closed loop facility. “We integrate a conventional dry mill ethanol plant with no dryers or evaporators. We use all the wet feed on site for an adjacent cattle facility. We have no drying costs, no transportation costs, and it greatly improves the efficiency of ethanol production.”
The feedlot on the operation had previously been in operation since 1970, according to Tracy. “It's all proven technology. The cattle are in 2,000-foot long barns all on slatted floors. The roof is open to the south, so the cattle are always eating in the sunlight. We found that to be one of the tricks of feeding cattle on slatted floors. The cattle like to be outside, so you have to design a facility that makes them think they're outside.”
The facility brings in corn — mostly from surrounding farms — and grinds it to remove the starch. All the feed then goes back to the cattle. “That's one point that often gets missed about the growth of corn being used in ethanol,” Tracy said. “A third of the corn comes back to us as feed. In that third volume of corn are 100 percent of the nutrients that were in the corn when we started. So all we're taking out is the starch. So you really haven't lost any feed value.”
The rest of the cattle feed ration is 5 percent silage and minerals and 62 percent steam-rolled corn.
Thin stillage (a by-product left when wet distillers grains are removed) and manure captured from the cattle are pumped to anaerobic digesters in 4 million gallon tanks, which makes gas to power boilers in the ethanol plant.
“We have a retention time of 21 days to convert the product to gas. The gas is then captured in a dome and pumped over to the ethanol plant to run the boilers. We create all the gas that we need to run the boilers.”
Overflow is sent to the effluent tank, which is a holding facility for the solids removal building. “We have a series of belt presses, clarifiers and filters to capture all the phosphate in a solids component. We can take that back to the land or sell it for use in the landscape business, wherever it's most profitable.
“We also treat the stream with lime, and send the liquid stream over to the stripper to strip off the nitrogen and turn it into an aquas ammonia for commercial grade fertilizer, which can be sold commercially, or we can send it back to the land to grow more corn. In the future, there is the potential for sending these products back to land in cellulosic production.”
Most of the water used is recycled, too, according to Tracy. Some goes back to the cattle, contained in wet feed. The water that is left after nutrients are stripped off is sent via underground pipelines to center pivot irrigation systems for area farmers. There are small amounts of P and N left in the stream.
The facility produces about 45,000 tons of wet distillers grains, which is 30 percent of the total ration for the facility, based on 26,000 head of cattle on feed at any one given time.
“There have been studies indicating we can go to 40 percent very easily,” Tracy said. “We designed this facility to be material balanced based on what we knew in the industry at the time. We started the facility in 2002. Now we could take the same facility with a 30,000-head feedlot and go to a 40-million to 50-million gallon ethanol plant. Our energy efficiency has gotten a lot better and we can increase wet feed volume to the cattle.”
Tracy said the ethanol produced is a low carbon fuel. “When you look at energy conversion, a standard ethanol plant is about 2 to 1 (For every two British thermal units out, one goes in). Conversion of crude oil to gasoline is only .08 to 1. So even the worst ethanol plant is twice as good as gasoline.
“Because we're making all our own energy, we have a 5 to 1 ratio, which is about what cellulosic ethanol is going to be. Low carbon fuels are the fuel of the future. Not only do we want to produce renewable fuels, but we want it in a system that creates low carbon fuel.”
Tracy cited a study by the University of Nebraska which showed that a closed loop system has an 80 percent higher energy coefficient than gasoline production. “Standard ethanol is 13 percent better, dry mill ethanol is 40 percent better, any plant not drying its product is 70 percent. So this is the best low carbon fuel on the market today.”
One of the biggest challenges for constructing the facility was getting through a morass of government regulations, Tracy said. “They classified our anaerobic digester as an industrial waste water treatment facility. We permitted this facility as though we were a standard factory with a waste-water stream and we had to meet all that criteria, which was challenging.”
The plant operates 24 hours a day, seven days a week and consumes 9.8 million bushels of corn. About 40 employees are required to run the operation.