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Biofilter System Lowers Manure Load, Odor by 90%

Odor complaints from neighbors living downwind from hog barns may soon be a thing of the past. Biosor, a biological filtration system perfected in Quebec, Canada and distributed by H2O Innovation, is designed to nearly eliminate odors and liquid effluent from hog barns. The system is particularly well suited for tightly closed confinement barns like those in Canada, the Midwest and Northern Plains.

Odor complaints from neighbors living downwind from hog barns may soon be a thing of the past.

Biosor, a biological filtration system perfected in Quebec, Canada and distributed by H2O Innovation, is designed to nearly eliminate odors and liquid effluent from hog barns. The system is particularly well suited for tightly closed confinement barns like those in Canada, the Midwest and Northern Plains.

Quebec Challenge

Pork production is a hot topic in Quebec, as many farms exceed the new, provincially mandated hog-per-acre ratio.

According to a Quebec government study, many hog farms are producing 120% more manure than they can spread on the land under the new regulations. Therefore, the industry was left with three options: reduce production, ship excess manure to non-surplus regions, or treat the manure to municipal waste standards.

In the early 1990's, the Quebec Center for Industrial Research (CRIQ) launched a $13 million project to develop viable biofiltration systems for heavily charged effluents, such as hog manure. Their target was to remove more than 90% of pollutants and nutrients in order to reduce the amount of manure spread on farmland to a strict minimum. A system had to have very low operation and maintenance costs and still achieve high performance standards for the processing of liquid waste and air vented from barns.

CRIQ came up with the Biosor system, an aerobic, organically-structured biofiltration system (Figure 1).

“I've seen various kinds of biofilters in Holland and England, and this is by far the best air cleanup system I have seen,” says Leonard S. Bull, professor of animal science and associate director of the Animal and Poultry Waste Management Center at North Carolina State University (NCSU).

“For hog facilities, where the odors coming from pit-ventilating systems are really serious problems, it seems to be a very logical application. Air quality is the next focus point that all animal agriculture must address, as highlighted by the new Environmental Protection Agency (EPA) monitoring program,” he states.

NCSU plans to install and test a Biosor system in an existing, full-scale hog operation in North Carolina in the near future (pending funding). By mid-2006, they hope to have a pilot scale operation running. H2O Innovation will be a partner in the project.

How It Works

The biofiltration process is quite simple and requires little attention. Separating the manure, so only the liquid and gaseous effluents pass through the biofilter, is one of the biggest challenges.

“Only the liquid portion of the waste is treated with the biofiltration system,” explains Elise Villeneuve, engineer with H2O Innovation. “The process is aerobic, which means it works with the oxygen in the air.” This organic bed is conducive for the right bacteria to develop. The natural resin in the bed fixes several pollutants and serves as a medium for microorganisms that digest the retained substances and break them down into carbon dioxide (CO2) and water (see Figure 2). “The biofilter uses a fixed-film biological process. Since it combines biological and physical processes, the system can deal with the variable manure loads produced by pigs as they grow. This is very important,” Villeneuve says.

“Normally, when you add a variable into a wastewater load, you need a fulltime operator for the treatment plant. With this biofiltration system, maintenance only takes a few hours every month. You just need to make sure the pump is in good working order and that the distribution system, the lines transporting the liquid manure to the biofilter, are washed out with a power jet. The media will last from five to eight years.”

Installation Issues

The method of separating the manure depends on the type of production, nursery or finishing, and the quantity of manure that needs to be treated. In some cases, separation can be done by decantation in a large tank. Other systems might require mechanical or physical and chemical separation.

In Quebec, several producers have converted existing manure storage tanks into biofilters, observes Bull. New facilities would require some sort of storage system, so those costs could be applied toward the biofilter and solid storage costs.

Bull suggests that walling off a section of an existing lagoon for the biofiltration process would be a relatively inexpensive option. Regardless, some costs will be incurred. But he reminds: “If we are dealing with air quality issues, it may allow you to stay in business.”

“Some Biosor biofilters are used exclusively for treating foul air,” points out Villeneuve. “Exhaust air from the hog barn is run through the filter and removes virtually all odors. In this case, keeping the filter clean and making sure the blower is in good working order is the only maintenance required.”

The peat moss and wood chip media utilized in Biosor, while available in huge quantities in Quebec, are hard to come by in some areas of the Unites States.

“We would need to come up with alternatives so the media wouldn't need to be shipped from Canada,” Bull notes. “Finding other local media that have the same proprietary components would need to be built into the research.”

Prototypes Tested

The first full-scale Biosor system, using a filtering media primarily consisting of peat moss and wood chips, was installed in 1997 in a 150-sow, farrow-to-finish facility in Ile d'Orleans, near Quebec City. The system was designed to treat 3,000 gal. of liquid manure/day and 2,500 cfm of foul air.

Preliminary findings were promising. The polluting load of the manure was reduced by 90% and the biofilters successfully deodorized 95% of the foul air.

Four subsequent hog barns and a dairy unit, outfitted with the system between 1999 and 2000, confirmed the initial findings. Owners of two barns aimed to solve odor problems, while the other three wanted to reduce land applications.

One test facility, a 1,200-sow unit operated by Purporc in St-Valerien in eastern Quebec, used an existing manure storage tank to separate the manure, and three Biosor filtration basins. This 10,000-sq. ft. system can effectively treat 9,000 gal. of liquid manure and up to 13,000 cfm of foul air daily. The effluent is discharged on farmland using an automated sprinkler irrigation system when weather permits.

The total investment was $425,000, with total annualized costs, including the initial investment, amortization, media renewal, maintenance, electricity, insurances and taxes, estimated at $95,000 ($15/1,000 lb. produced).

Jean-Paul Thériault, general manager of the Purdel cooperative, owners of Purporc, says that they are pleased with the results. In an age where barns face stiffer and stiffer opposition from various pressure groups, he says perhaps the most important benefit the Biosor system offers is ensuring their manure management practices are beyond reproach.

“Sure, there's a cost associated with using this technology,” Thériault says, “but we're hoping this will be seen as a value-added feature down the road.”

An installation at the Viaporc Inc.'s Cesy farm required a similar investment. Two Biosor biofilters were installed for their finishing facility of 35,000 piglets and 5,000 full-grown pigs in 2000.

The chemical separation of the manure is slowly being replaced by a more cost-efficient method of using a belt system running underneath the slats to separate solids from the liquid manure.

“We still have problems with ammonia, but we're making headway,” says Cécilien Berthiaume, Viaporc owner. “By 2007, our wastewater treatment should be fully operational, and we should be able to meet our goal to discharge the treated wastewater directly into a nearby stream for less than US$8.70/cubic meter.” (264 gal./cubic meter).

Not only has the system allowed them to increase their production capability from 5,400 piglets in 1999 to 35,000 without having to purchase additional land, they now meet the provinces' new land application norms — plus, they're eligible for Carbon credits under the Kyoto Treaty.

U.S. Pilot Project

Bull is talking with Hog Slat, Inc. to adapt the system to a 1,200-head building. “We're hoping to put one in the ground for around $150,000,” says Bull, assuming half of a lagoon is walled off for the biofilter. “There's a fairly sizeable margin of error with that figure, depending on material costs,” he adds.

Bull figures they could probably handle the lower volume ventilation rate in the winter with curtains down, but managing the higher summer ventilation rates would be more difficult.

“Obviously, you will have the most control in buildings that are entirely ventilated downward through the pits and whose sides do not open. With buildings that have curtain sides, and therefore diffuse ventilation, it will not be possible to capture all of the emissions. If the pits below the slats are ventilated, however, the concentrated odors and ammonia emissions will still be captured,” Bull says.

“There are a lot of things that need to be sorted out,” he continues. “Those are the reasons why the most logical and easiest installation locations in the United States would be in the upper Midwest, where facilities and ventilation systems are very similar to those in Quebec. Such installations could use the excellent scientific data from CRIQ without much, if any, modification. This would allow the process to start while we look at applications to other climatic zones and facility types.”