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Manure Conveyance System Nips Odor, Ammonia

Unique belt waste removal system cuts odor, ammonia and building costs in Dutch hog operation. Sometimes the best solutions to production challenges come from outside an industry. In pork production, manure handling and odor control serve as ongoing and major challenges. Martien van Kempen turned to chicken industry technology to solve his hog waste handling challenge. He adapted a belt waste removal

Unique belt waste removal system cuts odor, ammonia and building costs in Dutch hog operation.

Sometimes the best solutions to production challenges come from outside an industry.

In pork production, manure handling and odor control serve as ongoing and major challenges.

Martien van Kempen turned to chicken industry technology to solve his hog waste handling challenge. He adapted a belt waste removal system and double-deck hog housing to control odor and gaseous emissions, and dramatically change the nature of the waste product.

The Dutch producer grows 5,000 hogs and 70,000 laying hens near the small town of Venray, in the Netherlands. Unlike in the United States, Dutch farms are relatively small and privately owned, and their buildings are uniquely designed. At about 74 acres, van Kempen's farm is about average in size.

Because the farms are small and the environmental regulations reasonably stiff, manure and waste must be trucked significant distances from the farm; van Kempen once shipped waste up to 250 miles — some into neighboring Germany. The trucking cost was about $25/ton (U.S. dollars). He now ships some of the waste up to 100 miles at a cost of about $13/ton, but he now ships much less volume per animal.

Despite the differences between Dutch and American pork production, farmers in the Netherlands struggle to overcome the same odor and air quality problems.

This difficulty, along with van Kempen's experience with poultry, and his brother Theo's research at North Carolina State University (NCSU), led him to adopt a belt waste system for a new building constructed two years ago. The new building increased his capacity by 4,000 head.

Tackling Odor

One of the greatest advantages of the belt system is that it makes such dramatic strides toward controlling odor and gaseous emissions, Martien van Kempen says.

The polyethylene belt is forced into a slight “V” shape, forming a gutter that allows the urine to run off and be removed from the barn immediately. The feces collect on the belt, partially dry and are conveyed out of the barn every 12 hours.

The belt system fundamentally changes the nature of the waste as it leaves the building, providing very effective solids separation — a goal that is largely unachievable with waste streams from conventionally managed hog buildings.

The solid-liquid separation is extremely important, because when urine is kept from standing in solution with the feces, it prevents much of the odor. Separation also preserves much of the nitrogen in the urine.

If urine and feces are allowed to mix, much of the urea in the urine breaks down to form ammonia. Then it volatilizes, explains Theo van Kempen, Martien's brother and former associate professor at NCSU, and current director of swine research and development for a premix company in Belgium.

Urine from the van Kempen barn is removed quickly, treated with an acidic preservative and held in a sealed container. Later, it is mixed with poultry waste and sold to local mushroom farmers.

Quick removal and storage of urine is an imperative step to prevent ammonia release and odor in the barn, Theo van Kempen explains. If the urine goes into a sealed container within 12 hours, 95% of the urea can be kept from volatilizing. If a preservative such as benzoic acid or adipic acid is added, it converts the NH3 to NH4+, preserving even greater amounts of nitrogen.

Further, U.S. research showed separating the urine reduces ammonia in the building by 65 to 80%, depending on the extent of pen fouling. Actual ammonia concentrations measured in a U.S. facility with a ventilation rate of approximately 65 cubic yards/hour/pig space were only 2-3 ppm.

Research on methane emissions in the U.S. trials of the belt system showed it eliminated the stored-waste methane emissions and left only the methane that came directly from the hogs via flatulence and possibly respiration.

Like most farmers, van Kempen has no way to actually measure odor or gaseous emission, but he has noted a significant difference in air quality and pig performance.

Research in the United States shows a 5 to 10% improvement in gain-to-feed for pigs in a belt-waste facility, vs. the performance of pigs in standard commercial buildings.

“In the old facility, you smell manure and ammonia,” Martien van Kempen says. “In the new facility, you smell pigs — the animals themselves. You smell a little odor, but not much.”

Costs and Returns

With an estimated price tag of $7-8/pig space to retrofit a belt waste system in the United States, it appears to be a reasonable solution to odor and air quality issues when measured against the $3-4 cost/pig for lagoons, annually.

Theo van Kempen and fellow NCSU researchers developed these estimates for single-site farms with four, 1,200-head barns. The estimate includes the cost of urine processing with equipment called a sequential batch reactor, plus solid manure storage. This is more complex and expensive equipment than Martien van Kempen uses in his operation.

Martien van Kempen says the belt system compensates for seemingly high per-pig construction costs by improving animal performance, decreasing manure handling and shipping costs, and, potentially, by decreasing building construction costs because it allows hogs to be stacked.

Pigs could be stacked higher than the two layers, he says. “Theoretically, you could go much higher, and that would reduce the cost per pig space even more.” This ability to go higher instead of wider and longer offered significant savings, Martien van Kempen says.

Construction costs for buildings are fairly high in the Netherlands, typically running 350-400 Euros ($420-480)/pig space. The double-deck construction, made possible by the belt system, held van Kempen's cost to 250 Euros ($300)/pig space, a cost savings of roughly 40%.

It was less costly to increase the building height by 6 or 8 ft. than it was to go down with sealed concrete manure holding pits, which is the standard technology in the Netherlands, he adds.

The high nitrogen content in the pig urine boosts the nutrient value of poultry waste when mixed, making it an ideal fertilizer for nearby mushroom farmers. The solid portion must still be hauled every three or four weeks however, but the volume is lower, the nutrient quality is arguably higher, and there is less odor.

Van Kempen's farm produces about 10,500 cubic yards of poultry and hog waste each year. He can only apply roughly 85 lb./acre/year of phosphorus to his own land. That amounts to about 785 cubic yards — so he must export about 92% of his animal waste to other locations.

Since no one in the United States has adopted such a commercial system, it seems difficult to make Martien van Kempen's figures apply here. Nonetheless, his experience with the belt waste system shows some of the strong advantages and the potential options for a radically different waste management system in modern hog production.

Adapting the Belt Waste Removal System for Hogs

Belts have been used successfully for waste removal in the laying hen industry for about 30 years. They require little maintenance, typically last eight to 10 years, and allow the poultry manure to be collected in a dry form with minimal ammonia and odor emissions.

When Martien van Kempen designed his new hog house with a belt waste removal system, he looked at the experimental designs from North Carolina State University (NCSU). Some drained into gutters; others used the belt as a gutter, either on one side or in the middle.

“We literally built seven versions of the belt system until we got it right,” says Theo, Martien's brother, who was involved in the U.S. research.

“During this research, Martien and I had many exchanges about how to continue with the belt system, and this is how his system got started,” Theo says.

Theo adds that belt manure systems exist under hogs in Korea, the Netherlands and Germany, but to his knowledge, few, if any, of these systems segregate the urine from the manure.

Theo noted some of the clogging problems the researchers reported with a separate gutter system. So he decided to use the belt framing to create a more dependable gutter for urine removal by forcing the belt into a “V” shape, and leaving about 16 in. of the pen flooring solid over that section of belt. The urine drains constantly from the middle of the belt into a closed collection system.

Slotted flooring over the rest of the belt, a width of about 6.6 ft., allows urine and feces to drop through onto the belt for removal.

Because of his experience with poultry belt systems, Martien van Kempen realized the need for maintenance and repair, and he left an access space between the pens at about every 10 ft.

He runs the belt at 6 a.m. and 6 p.m. daily, twice as often as NCSU ran their belt. Higher frequency means less weight and less wear on the belt, and reduces the puddling of urine in standing fecal material. However, emptying the belt more often also means less drying time and potentially wetter dry matter.

This is not a problem, however, says van Kempen. He uses a fan separator to bring the fecal material down from about 50% dry matter to 75% dry matter before hauling it.

His conveyer framing for the belt provides about 4 in. of fall in about 195 ft. This does not drain the urine as quickly or as well as it would with a greater degree of incline, but the more frequent emptying of feces from the belt overcomes that issue, too, Martien says.