Manure separation could be key to P accumulation issue

Removing phosphorus-rich solids from nitrogen-rich liquid allows both 
local use and economical transportation to other farms

A unique method of separating nutrients in hog manure, based on European technology, may give livestock producers another way to deal with excess soil phosphorus in southeastern Manitoba’s livestock alley.

The method involves separating out the solids in manure from the liquid, using an automated conveyor belt system. Solids in hog manure are high in phosphorus (P), while the liquid is rich in nitrogen (N). The liquid is injected locally into the soil as nitrogen fertilizer, while the solids are shipped out to phosphorus-deficient areas elsewhere in the province.

The Prairie Agricultural Machinery Institute tested the system last year on a hog and grain farm near St. Malo. The automated system is manufactured by VP Systems, a Dutch-based company. It and similar manure treatment systems are common in Europe, but this is believed to be the first attempt to apply this technology in Canada.

Lauren Wiebe, who owns Topeaka Farms where the system was tested, said it helps him use the nitrogen in hog manure for his crops without having to worry about putting excess phosphorus on the land along with it.

“I had all of this nitrogen sitting in my lagoon but it was too much phosphorus for what I wanted to do,” Wiebe said.

Lauren Wiebe with phosphorus-rich solids separated from hog manure on his farm near St. Malo.

Lauren Wiebe with phosphorus-rich solids separated from hog manure on his farm near St. Malo.
photo: Don Flaten

Some soils in southeastern Manitoba, especially in the hog-intensive municipalities of Hanover and La Broquerie, are starting to experience soil phosphorus overload. Too much phosphorus in the ground can be an environmental issue. Run-off P from saturated soils is linked to algae blooms and degraded water quality in Lake Winnipeg and other water bodies.

The Manitoba Livestock Manure Management Initiative, working with PAMI, is conducting a series of projects to find ways of removing excess phosphorus from the region. The VP manure separation system is the MLMMI’s latest project. Results were released in late December.

Hog manure contains roughly three times as much P as N. When farmers continually apply it as fertilizer, soils get more P than crops can use. This eventually leads to excess P in the soil and increases the risk to water sources.

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The VP separation system enables farmers to use the N in liquid form while making P available as a solid for others, said Harvey Chorney, an agricultural engineer and PAMI’s vice-president of Manitoba operations in Portage la Prairie.

Since the P is in a dry, solid form, it is much lighter, easier and cheaper to transport out of the region, according to Chorney.

“You have to move it. But remember, the mass that you’re moving now is much less than what it would be if you were doing it in a liquid state,” he said.

Wiebe said previously he had to buy N fertilizer separately for his crops, since he couldn’t use hog manure because of excess P. Now he can use his own N-rich liquid and save money while doing it.

“I look at the cost of getting that separated (and) it’s a lot cheaper to separate than it is to buy fertilizer.”

The process starts by agitating hog slurry into a homogenized mixture. The mixture then goes through a flow meter into a flotation tank where a calibrated blend of air and polymer is added. These cause the solid particles to cling together and float to the top of the tank. A belt filter press system separates the liquid from the solids. Rollers on the belt squeeze out as much liquid as possible. The solids go into storage, while the liquids enter an effluent tank and eventually a lagoon.

The solids have an average dry matter content of 6.5 per cent, which enables them to be handled easily as a solid product. The P concentration in the separated solids is more than four times greater than in the original liquid manure. This makes it more economical to transport the dry solids instead of raw manure.

Also, the P concentration in the liquid effluent is 83 per cent lower than in the original manure, reducing the risk of excessive P buildup in the nearby soil.

The downside is the expense. The total capital cost is just under $1.8 million. The operating cost for one year is $571,000 — more than three times as much as for a traditional land application system.

Wiebe said he is able to recapture some costs by selling P solids to other farmers in his area, as well as elsewhere in the Red River Valley. Government subsidies helped pay for the system’s installation.

Don Flaten, a University of Manitoba soil science professor, points out the P concentration in the separated solids is still much lower than in commercial 11-52-0 fertilizer. A canola grower using those solids would still need to supplement with commercial fertilizer to provide the crop with enough P.

But Flaten stressed the agronomic value of separated manure is greater than P alone. Another project sponsored by the MLMMI at the U of M’s Glenlea Research Station is evaluating the overall value of separated solids, using the flotation system at Topeaka Farms as well as a centrifuge system.

Wiebe said hog farmers in southeastern Manitoba must find ways of removing excess phosphorus, especially if the province ever decides to regulate land applications of P. For that reason, there are more considerations than just cost.

“At the end of the day, we’re going to pay the piper,” said Wiebe. “I’d rather pay it sooner than later.”

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