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V-Shaped Scraper Helps Deter Ammonia, Phosphorus Concerns

New scraper design studied at Michigan State University (MSU) is part of a cooperative study with two groups in Quebec, Canada.

As nutrient management becomes an ever-increasing concern, pork producers must look at new ways of handling manure.

The V-shaped manure scraper studied at MSU effectively keeps solids and liquids separate, which in turn lowers manure transportation costs, helps isolate phosphorus concentrations and lowers gas emissions.

The system, known as the “liquid/solid isolation system,” has been part of a collaborative study between researchers at Michigan State, the Institute of Agroenvironmental Re-search and Development, Inc., Quebec, Canada and Quebec Pork Development Center.

The researchers are especially interested in the system because farmers across North America are facing tough environmental regulations based on phosphorus content in soil and manure. Researchers in Quebec are particularly interested in the technology because farmers there must balance phosphorus levels by 2010 or reduce the number of pigs raised.

“We have to balance phosphorus levels,” says Francis Pouliot, an engineer with the Quebec Pork Development Center. “We have no choice.”

The Quebec government is serious about the environment; so serious, in fact, it placed a moratorium on all new hog buildings in Quebec in 2003.

Separation Helps Control Phosphorus

Keeping the solid and liquid portions of the manure separate allows more of the phosphorus to be controlled, explains MSU researcher Robert von Bernuth. Michigan State studies found that 90% of the phosphorus remained in the feces using the scraper system, and overall, they could account for 96% of the phosphorus.

Paying attention to phosphorus is important because the nutrient tends to build up in the soil. This occurs in part because the phosphorus-to-nitrogen ratio required for plant uptake is out of balance in most manure.

For example, if the nitrogen requirements of the plant are met by the amount of manure applied, the amount of phosphorus will be twice what the plant needs. Phosphorus is not released in the air, so excesses stay attached to soil particles until they are washed away. Consequently, phosphorus levels in the soil just keep building up.

If the solid and liquid portions mix, not only are transportation costs significantly higher, it is much more difficult to remove the phosphorus. However, over the years, attempts to remove liquid from solid in manure have had limited success.

Removing liquid is not necessary if the two are never allowed to mix, explains von Bernuth. When urine and feces mix, a chemical reaction occurs, releasing ammonia and taking nitrogen out of the manure mixture. Preventing this not only reduces the amount of ammonia released into the atmosphere, it also keeps the level of nitrogen in the manure as high as possible, which improves the nitrogen-to-phosphorus ratio.

V-Shaped Manure Scraper Studied

The scraper being studied at MSU differs from traditional under-slat systems. The floor of the pit is V-shaped with an opening at the bottom of the “V” where water and urine collect and drain to the pit. The feces collects on the pit floor and is scraped into a separate holding area where a dairy barn manure scraper (barn cleaner) removes the solid manure from the facility and deposits it onto a covered, concrete pad. The manure is then taken to a composting facility.

Following a 15-week study, MSU researchers concluded that the system was effective in several different areas:

  • It achieved the desired goal of isolating solids from liquids, and the phosphorus was largely contained in the solid portion of the manure. The moisture content of the solid manure was about 66%.

  • Less gas was also released from the manure, which may have contributed to the excellent performance achieved by the pigs. Ammonia concentrations in the facility were less than 5 parts per million (ppm) for most of the study and never exceeded 7.5 ppm.

  • Hydrogen sulfide never reached a detectable level.

The combination of top pig performance, air quality and solid-liquid manure separation have generated so much excitement in Quebec that five commercial barns have been constructed using the scraper design. In operation since September, researchers are anxious to get a good handle on the costs associated with the V-shaped scrapers.

Cost Tradeoffs

Based on the MSU project, Pouliot says the V-shaped scrapers will cost approximately $31/pig space more than the cost associated with a conventional scraper system. Costs for renovating an existing barn to accommodate the V-shaped scraper would be about $41/pig space higher than for a conventional system.

The extra costs of the V-shaped scraper system come primarily from the platform needed to store the solid manure and the barn cleaner used to take the solids out of the barn, says Pouliot.

But, there are some savings associated with the V-shaped scraper system, too. Because a smaller manure tank is required, about $9.00/pig space is saved. As contractors become more familiar with constructing the system, costs may come down further, he adds.

In Quebec, where manure cannot be spread on fields with a high phosphorus content, savings in transporting the manure to more distant fields with lower phosphorus levels can be significant. Costs associated with manure disposal are high, especially in areas that have traditionally had high concentrations of pig manure applied.

Worldwide Interest

The V-shaped scraper system is generating interest around the world. Originally developed in Japan, people in Europe are now looking at the system because of the work done by von Bernuth, Jeff Hill and Erin Anderson at MSU, explains Pouliot.

“This is a worldwide problem. People don't want more pigs,” says Pouliot. A system that reduces odor as well as environmental problems, such as excess phosphorus, may help keep the land healthy while allowing people to enjoy their ham and bacon, he adds.