A 2,500-sow corporation in west central Minnesota has spent more than $200,000 on environmental controls. So the last thing general manager Jeff Vosika expected was a call from the Minnesota Pollution Control Agency (MPCA) reporting an odor complaint.

Vosika met with MPCA officials and learned an odor complaint on a nursery-finishing site triggered a hydrogen sulfide test. Unofficial test results showed the farm bordered on violating the state's hydrogen sulfide emission levels.

Vosika, who works for Churchill Co-op, Hector, MN, and the MPCA officials together worked out a plan to lower the hydrogen sulfide emissions.

Executing the plans, Vosika reports hydrogen sulfide emissions dropped to safer levels at the production site.

Vosika and Churchill Co-op's experience in Minnesota represents a new trend in the state and possibly country. A rule about hydrogen sulfide emissions drives the push to control odors from livestock. The state has a hydrogen sulfide emission standard of 30 ppb (parts per billion).

Complaint-Driven Tests People can call MPCA and file a complaint about a farm's odor. The regulatory agency must respond. They send out an employee to screen the site for potential hydrogen sulfide problems. A Jerome meter is used to test for hydrogen sulfide only. Readings from the meter are not official and are only used by MPCA to screen possible trouble.

If readings are near or above 30 ppb at the property line, the farm is notified. At this point, MPCA and the farmer work out a plan to lower the gas levels without taking the complaint further.

The success rate for this process is very high. Jim Sullivan with MPCA reports the agency has checked on 360 odor complaints in 11/2 years. Virtually all odor complaints with high hydrogen sulfide readings have been resolved.

In the case of Churchill Co-op, the offending site already had a polypropylene cover on the lagoon. However, the cover was not working correctly and bubbled. Voiska, acting on the advice of MPCA, added straw around the edge of the lagoon cover. This lowered the gas levels to legal limits.

On sites in violation, MPCA places a continuous hydrogen sulfide monitor. The monitor, measuring gases 24 hours/day, will produce an official hydrogen sulfide reading. Violations of the hydrogen sulfide rule can only be charged with measurements taken by this type of monitor. The agency uses three monitors in the program.

"This is a new program," Sullivan says. "Hydrogen sulfide is the way Minnesota addresses the odor issue. While hydrogen sulfide is a component of odor, it doesn't correlate very well. You can have odor and not hydrogen sulfide."

If a farm has an odor complaint but tests low for hydrogen sulfide, the MPCA does not need to get involved.

Many of the state's hog farms already are working to keep potential hydrogen sulfide problems and odor low. Churchill Co-op, for example, had invested $85,000 for the lagoon cover. Therefore, they wanted to make it work. The additional straw did just that.

Churchill Co-op has other production sites, including a 1,200-sow facility with a two-stage lagoon. On this facility, they've incorporated a different odor-control system involving a two-step biological process. It uses low-level aeration in lagoons to keep solids in suspension.

This site was tested and reported a low level of hydrogen sulfide. Vosika says this is their second year using this system and it does the job.

Some 2.5 million gal. of manure from the lagoons is injected into cropland for Churchill Co-op. A commercial applicator with a drag-line hose system does the job.

Finding What Works Minnesota's program of testing for hydrogen sulfide has created a need to find quick ways to reduce odors and emissions.

Officials at the University of Minnesota and other commercial companies have come up with several they recommend to producers.

Here is a brief description of some of the newer methods being used to cut emissions from manure storage:

Biofilter - The university has experimented with biofilters for removing gases from hog buildings. This method has proven to be a low-cost option for holding down odors and hydrogen sulfide gases from buildings with deep pits. Cost runs 50-80 cents/finishing pig.

In a biofilter, air from a building is exhausted by a ventilating fan into a biofilter plenum. The plenum distributes the air across a biofilter media, which is usually shredded wood and compost. A supporting screen holds the media above the plenum.

The air goes through the biofilter media before entering the atmosphere. As the air passes through the media, it is filtered of gases, contaminants and odors. The media bed must be changed every three years. The bed also must be kept moist in the summer, which Nicolai accomplished by hooking up a lawn sprinkler and running it one hour every evening.

This biofiltration process is widely used in areas like septic fields to treat odors. Microorganisms in the media oxidize the gases and vapors, making them less odorous.

Nicolai says the initial cost of biofilter for a 750-sow, farrow-wean facility was $9,225. Additional electrical cost is about $400/year.

A disadvantage of the system is weed and rodent control on the bed. A design procedure for the biofilter is available on the university's website for the Department of Biosystems and Agricultural Engineering: www.bae.umn.edu

BioSun - Churchill Co-op uses a two-step biological process that targets hydrogen sulfide in manure. The patent-pending process also lowers other manure odors and gases. Unofficial hydrogen sulfide tests showed the unit in compliance with the state's hydrogen sulfide levels.

BioSun is a commercial system that uses a biological process to enhance the digestion of solid waste and organic matter. Diffusers, powered with small compressors, then keep the solids in the lagoon in suspension. The diffusers also provide oxygen for the digestion process.

The diffusers use only 0.6 kilowatts/hour at a monthly cost of $30. According to BioSun's Greg Patterson, a 1- to 2-acre lagoon will require 6-8 diffusers. Cost of the system is 40-50 cents/hog marketed.

Patterson has conducted wet chemistry tests on the Churchill Co-op lagoons as well as the Jerome meter. Jerome meter readings around the lagoon in September found hydrogen sulfide levels at 7 ppb, well below the 30 ppb state standard.

Vosika says the cost to maintain the system is $5,000-7,000/year. Lagoon effluent is used to recharge pits in the sow unit. He adds that the air seems fresher now in the unit.

Floating Clay Balls - University researchers have tested a floating cover of small, clay balls. The balls are similar to leca or macrolite balls used in Europe. The balls float and promote a natural crust. The layer of balls should be 6-8 in. thick. Cost for the product is $2-5/sq. ft.

Nicolai says the layer of clay balls should last several years. Pumping from the storage unit should be done with care, however.

Geotextile Mat - Dick Nicolai, an agricultural engineer from the University of Minnesota, reports a geotextile mat can work to hold gas emissions from manure storage units.

The geotextile mat is a thick material used in construction under roadbeds. It floats on top of the manure storage unit with 4 in. of straw blown on top. Nicolai says it is a dry material and rain goes through it.

The mat lasts longer than a thick layer of straw, which deteriorates after a couple of months. "The geotextile and other inorganic material may offer a longer-term solution," Nicolai says.

He estimates the cost of the geotextile mat at 20-25 cents/sq. ft., including installation and straw.

Land Application - Producers who want to apply their manure to cropland should inject the manure into the soil to keep odors low, according to Nicolai. This technique may not be new, but it dramatically lowers odors during land application.

Manure Additives - The university has tested a number of manure additives, including those added to the manure or fed to the hogs.

"Additives work good in reducing solids, but are poor to fair for odor reduction," Nicolai reports. Costs run from $0.50-1.00/pig.

Straw Cover - Straw is being used to hold down odors from many manure storage units in the Midwest. Large straw bales are chopped and blown onto the manure.

Nicolai estimates the cost of these covers at 10-15 cents/sq. ft. A straw cover lasts about three months and and serves as a good, short-term solution.

Jerry Shurson, swine nutritionist at the University of Minnesota, is investigating how to reduce hydrogen sulfide emissions by manipulating pig diets.

"Our studies have shown by carefully selecting low sulfur feed ingredients and using them to formulate nutritionally adequate, low sulfur starter diets, total sulfur and sulfate excretion can be reduced by approximately 30% without compromising energy and nitrogen digestibility or pig performance," Shurson explains. "Furthermore, our studies show reduction in total sulfur consumption and excretion may lead to a reduction in hydrogen sulfide gas and odor, but appears not to affect ammonia levels in nursery facilities."

Meeting Sulfur Requirements Sulfur is an essential element for the pig. The pig's sulfur requirement is met by providing adequate levels of the sulfur-containing amino acids methionine, cystine and cysteine, and the water soluble vitamins biotin and thiamin.

Organic forms of sulfur are readily absorbed relative to all sulfur compounds. Absorption of inorganic sulfate from the gastrointestinal tract is inefficient, Shurson explains. Unabsorbed sulfur is likely reduced in the lower gastrointestinal tract and excreted as sulfate, researchers speculate. Inorganic sulfur is excreted via feces and urine.

Proteins are present in every cell of the body, explains Shurson. Sulfur-containing amino acids are components of almost all proteins, which means sulfur is widely distributed throughout the body and is found in every cell.

Because the bulk of body sulfur is present in amino acids, it is not surprising that urinary sulfur excretion tends to parallel urinary nitrogen excretion. High protein diets are associated with large amounts of urinary sulfur and nitrogen.

Shurson says it appears most of the production of hydrogen sulfide and other volatile sulfur-containing gases occurs as a result of microbial fermentation during manure storage.

Sulfur is found in a variety of chemical forms and changes forms depending on chemical conditions in manure storage systems.

Shurson concludes that sulfate levels in drinking water and feed appear to be significant contributors to hydrogen sulfide levels on commercial hog farms. However, he says other poorly identified factors are also involved in hydrogen sulfide levels. Sulfates excreted in urine and feces are easily converted to hydrogen sulfide under anaerobic microbial fermentation processes in the manure storage structure.

Shurson says preliminary data suggests if high sulfate drinking water and high dietary levels of sulfur are found in on-farm production conditions, hydrogen sulfide levels may be increased on some farms compared to farms with low sulfur feed and water.

Analyzing Ingredients Having an accurate analysis of the sulfur levels of swine feed ingredients can make a difference when attempting to reduce manure sulfur levels.

Shurson says sulfur content of common swine feed ingredients ranges from 0.02% in dried bakery product to 1.59% in low lactose dried whey, according to National Research Council (NRC) figures from 1998. The Minnesota researchers chose to analyze the total sulfur content for all ingredients used in complex starter diets. The results were compared to values published by NRC.

Shurson reports the values he and his colleagues analyzed were very similar to NRC values except for a much lower sulfur value for spray dried whey (edible grade) and a somewhat higher value for spray dried blood meal.

Nutrient Levels Vary "The discrepancy for dried whey is likely due to potential differences in nutrient levels of various sources and grades, coupled with natural analytical variability," Shurson says. "The discrepancy for spray dried blood meal is likely due to variability in product quality among sources."

NRC does not list sulfur values for spray dried porcine plasma, for many grades and sources of fish meal, tricalcium phosphate, DL methionine, or copper sulfate. Therefore, the researchers calculated sulfur values based either on sulfur amino acid content listed on ingredient specification sheets for spray dried porcine plasma; or, in the case of the fish meal source used and the tricalcium phosphate source, the values were taken directly from product specification sheets. "These results suggest NRC sulfur values are accurate and can be used for most commonly used ingredients in starter diets," Shurson explains. However, he suggests spray dried plasma, spray dried blood meal, fish meal, and spray dried whey should be analyzed to establish reliable sulfur content values if producers are selecting ingredient sources to minimize sulfur content of starter diets.