Vreba-Hoff: Making compost from manure

Written by David Green.

By DAVID GREEN

The owners of two large dairy farms are attempting to put an end to manure discharges into drains and streams through the use of a million dollar partial treatment system.

Guests from as far away as Dayton toured the Vreba-Hoff I farm on Dillon Highway July 26 when the manure management system was unveiled to the public.

vreba-george Farm co-owner Stephen VanderHoff welcomed the new approach to manure handling in January 2005 after an agreement was reached with the Michigan Department of Environmental Quality (DEQ). He knew the system would pay for itself within a few years and would place the Vreba-Hoff farms on the leading edge of farm technology.

Skip Pruss, deputy director of the DEQ, spoke about the project at the open house, noting that relations between farm owners and the environmental agency have been rocky at times. Despite that, he said, communication with VanderHoff has always been good.

“There’s always been a willingness to listen and to learn,” Pruss said. “We have a lot to learn, too.”

When the system is fully operational, manure from about 6,000 cows housed at two Vreba-Hoff dairies will be processed through the equipment. The system at Vreba-Hoff I is the fourth agricultural installation for Press Technology of Springfield, Ohio, but this stands as the company’s largest endeavor.

The company’s Agri-Clean system is designed to address three concerns: limiting phosphorus in soil, controlling odors associated with manure storage, and handling the volume of manure stored on farms.

Making compost

Manure is removed from barns and mixed with water for storage in lagoons. In the treatment process, the slurry passes through a thickener to increase the amount of solids and then through a press to create a substance that is 35 to 45 percent dry matter, with all the “free water” removed. A chemical additive is used to separate out additional solids from the liquid discharge, and those are run back through the thickener and press. This process also binds phosphates with the solid mass.

The fluffy material coming out of the press is transported by conveyor where stacks are formed. This is later removed to pads outside where the material heats as it decomposes and naturally destroys pathogens. The piles are turned for complete composting and the finished product is ready for use as fertilizer on fields or for bedding in the barns.

At the open house, Dan Busscher of Vreba-Hoff explained that so far only one barn at the Dillon Road farm is using compost for bedding.

“We’re just getting started,” he said.

The other barns are all using sand, and that’s caused some problems because sand does not decompose.

VanderHoff hopes to have all barns converted to compost bedding by the end of the year, as fine-tuning of the system continues.

“Compost, if done right, is really good for the soil,” said Rachel Matthews, a DEQ compliance officer who oversees the treatment system for the environmental agency.

Scott Miller, now based in the DEQ’s Kalamazoo office, worked with VanderHoff on the project until Matthews took over in the spring.

Miller said compost making is based on a strict protocol involving temperature, moisture and the ratio of carbon and nitrogen.

“It has to be monitored closely to do it right,” he said.

Finished compost must be stored on a pad to catch any runoff and the storage area must be large enough for the quantities produced. The two dairies’ 6,000 cows produce enough manure to create six semitrailer loads of solid matter every day, although about a third of that volume is lost during the composting process as it dries, VanderHoff said.

Storage capability will also have to take into account compost produced in the winter because the two farms are under an order that prohibits the application of nutrients from December through February.

“I was impressed,” Miller said about the new press system. “There’s lots of similar equipment manufactured for other purposes, but this one is designed for dairy use. The system will give them a much better tool than what they’ve had.”

With phosphorus bound up in the soil, Matthews said, it should break down more slowly when plants can use it. She sees this as a much better approach than liquid manure application where soluble phosphorus is added at rates higher than the soil can handle.

“This is why a Comprehensive Nutrient Management Plan (CNMP) is important,” she said, “and why all farms should be applying nutrients to the fields at appropriate rates, times, using best practices, setbacks, etc.”

Liquids

The waste water collected from the press is sent to an aeration pond where an aerobic process reduces remaining pathogens. A separate storage pond holds silage leachate that VanderHoff says is somewhat diluted by other water collected. Both liquids are applied to fields through a pivot irrigation system—minus the strong odor of liquefied manure.

A low-rate irrigation system is the best method for dispersing the liquids, Matthews said, and by irrigating on growing plants, the nutrients from the silage leachate will be put to best use. If anything, she said, the irrigation process will still leave crops short of required nitrogen.

The low-rate nozzles will avoid pooling in fields, VanderHoff said.

Soil tests are required every three years as specified in the farm’s general permit, but farm owners must keep tabs on the composition of the liquids and solids in order to write an accurate CNMP.

“The liquid is not ‘clean’ from aeration,” Miller added. “It’s something they’ll have to watch.”

Adequate lagoon storage space will be necessary for winter months.

Is it working?

Although Stephen VanderHoff had been investigating alternate manure handling systems, the new technology was driven by an order from the DEQ due to discharges of manure and silage leachate in the past. Followup studies are planned.

“We will be monitoring Vreba-Hoff’s performance to determine if his waste management practices are affecting water quality,” said DEQ Jackson district water bureau supervisor Jon Russell.

Matthews will keep a close eye on the entire system, he said, including checking tile lines during irrigation periods.

Not everyone is satisfied with the DEQ’s approach. Members of the Environmentally Concerned Citizens of South Central Michigan in January began testing the dissolved oxygen level in six drains flowing from Vreba-Hoff farms. Their aim was to collect some baseline data before the new system went into use. Data collected in July suggests that a problem still exists.

Dissolved oxygen (DO) is essential for the support of aquatic life and gives an indication of water quality.

“At two sites, DO levels were the lowest they have ever been in all the years of our sampling,” said Janet Kauffman in a press release.

DO levels far below state water quality standards were detected even in flowing streams, she said. By comparison, samples taken from two locations with no large farms upstream showed healthy DO levels.

Kauffman suspects the liquids used in irrigation could be further degrading water quality and she’s requesting that the DEQ test the system’s waste water for pathogens and nutrients.

Russell agrees that testing is in order and data has been requested from Vreba-Hoff, he said.

Matthews doesn’t expect the new system to be perfect, but she thinks it will improve through VanderHoff’s continuing management efforts.

VanderHoff said last year that he hopes other farm owners follow suit and install treatment systems. The owner of one smaller CAFO said at the open house he doesn’t see it as practical for his size of operation.

The press requires 24-hour attention, he said, and by Press Technology’s estimates, the average, annual operational cost for a 6,000-head farm would run about $200,000.

“I think you’ll see more in stages rather than the entire system,” VanderHoff said.

A smaller operation might install an aeration system one year and a press or thickener another.

The DEQ’s Skip Pruss can be counted among those who want to see more manure treatment systems put in place.

At the open house, Pruss stated his belief that the trend toward large dairies is irreversible. Economy of scale will win out, but the environment must be protected.

   - Aug. 16, 2006
Photo caption: TRANSFORMATION—George Berner of Press Technology shows a handful of what was once liquefied manure. Berner designed the press that separates manure into a liquid and this fluffy solid that will later be composted.
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