August 18, 2005 | General


BioCycle August 2005, Vol. 46, No. 8, p. 47
Anaerobic systems on Illinois dairy farm supplies renewable electricity, crop nutrients and bedding replacement that improves milk quality.
Melissa Dvorak

AT HUNTER HAVEN FARMS in Pearl City, Illinois, an engine fired on May 23, 2005 from an anaerobic digester where biogas powered a generator to create renewable electricity. Also captured and used were a liquid fertilizer with little odor and a solid used as a bedding replacement or as a quality fertilizer for nurseries. Dairy farm owners Doug and Tom Block have been following the progress of digesters for eight years, settling on a GHD unit because it was not “management intensive and liked the comfort that the bedding provided for the cows.”
A major benefit of the system is that the bedding leads to improved herd health. An important metric to a dairy farmer is something called “somatic cell count”, a measure of the amount of bacteria in the milk. The lower the number, the greater the premium the farmer receives for his milk. So far this summer, even when the temperature was 90 degrees and above, Hunter Haven’s somatic cell count was less than 150,000. “When we were on sawdust, our somatic count was 200,000-300,000, with counts over 300,000 at various times during summer. We’ve seen the lowest somatic counts of any summer.” In addition, they have had no instances of Klebsiella Mastitis, a serious form of mastitis often resulting in death to the animal. When using sawdust for bedding, the farm would average two to three cases of Klebsiella a month. Reducing the cases of Klebsiella has led to savings in vet bills, as well as saving the significant cost of purchasing a new cow.
Prior to the digester, Hunter Haven was using sawdust on top of its cow mattresses, spending roughly $100 per year per cow for the sawdust. Now that the farm is using the digested solids for bedding, Block commented that “the cows are now laying down more, are more comfortable than they were on sawdust.” Currently they are bedding with the biosolids daily to build depth in the stalls. The farm plans to switch to deep bedding as the mattresses wear out, rather than replace them. In addition to increased cow comfort, Block also has seen a rise in his milk production of four to five pounds, which he attributes to a combination of the biosolids bedding and new feed.
In the months that the digester has been operating, there has been a decrease in odor from the lagoon, and it keeps improving. After the second crop of alfalfa, Hunter Haven spread 6,000 gallons/acre of digested manure from the lagoon on an alfalfa field eliminating the need to purchase potash to fertilize the alfalfa. “It seems to be greening nicely so far,” says Block.
Another benefit of the digester was efficient electrical production. “GHD produced more electricity per cow than other systems.” Currently the waste from 550 cows is flowing to his digester, with the system consistently producing 97-99 kW per hour. In addition, waste heat from the engine produces a surplus of hot water that will be utilized by the dairy for hot water in their milking parlor. The digester and engine were intentionally oversized, since the Blocks intend to expand their dairy and herd in the future.
According to Block, the most difficult aspect of the project was dealing with the utility. “We had a significant delay getting hooked up with the power company, which added 10 percent to the project. The six month delay meant I was paying interest on loans without receiving any benefits of the system,” says Block.

Sign up