WINNIPEG – A Vancouver company is using gravity to remove urine from hog manure.
Called Closed Loop Manure Recovery, the system channels manure onto a sloped, perforated conveyor in the barn, where the urine is continuously collected for a nearby liquid processing and purifying plant.
ATD Waste Systems president Victor Van Slyke, who invented the system, says it is the only manure treatment scheme that addresses the segregation issue at the moment when solids and liquids are excreted.
Although all new systems designed to treat hog manure depend on segregating nitrogen-rich liquid from phosphorus-rich solids, other systems separate the two components later, sometimes many days after the manure leaves the barn.
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In his presentation to Manitoba Hog & Poultry Days in December, Van Slyke said the key to solving hog barn odour problems is to halt anaerobic activity right at the source by separating urine from solid manure immediately.
He said this prevents anaerobic activity, eliminating the two typical hog manure problems of odour and lethal hydrogen sulfide.
Anaerobic activity is the organic breakdown that occurs without the presence of oxygen in a slurry lagoon or storage tank. When the lagoon or tank is agitated, the gases that have been produced by anaerobic activity are released to the atmosphere in large quantities.
One of those gases, hydrogen sulfide, is considered by the livestock industry to be the most dangerous of those produced through anaerobic decomposition of manure.
“If you can stop anaerobic activity, you can stop the production of both ammonia and hydrogen sulfide.”
ATD’s system doesn’t use a storage tank or lagoon, which means there is little opportunity for chemical reaction between urine and solid manure and no generation of odour or hydrogen sulfide.
Van Slyke said chemistry is the key.
“Ammonia is caused by enzymes which are produced when bacteria in the feces attacks urea in the urine,” he said.
“Low ammonia levels mean improved health for people and animals. You also get better feed conversion.
“In my system, the feces and urine drop down to a conveyor which only runs once a day, for about five minutes. But the urine is constantly being drained away and removed from the barn. We have only momentary contact between the urine and the feces, so there is almost no anaerobic activity.”
Van Slyke concedes some barn smells will continue because of evaporation from the floor and from the animals themselves. However, he said the levels are far below regulatory requirements.
The liquid passes through a membrane filter and then through an ammonia stripper that uses heat and pH to extract the ammonia and convert it to ammonium sulfate, which is eventually added back to the solid material before drying to enhance the value as fertilizer.
The next step is to bombard the liquid with ultraviolet radiation to kill pathogens and adjust pH with lime and sulfuric acid.
Finally, with all nutrients removed, the cleaned water is piped back to the barns and mixed 50:50 with the fresh water supply.
The chemical reaction in the remaining feces is now fully aerobic because it has free access to oxygen. The method not only prevents the generation of ammonia and hydrogen sulfide but also preserves the urea in the manure, which has value as fertilizer.
The conveyor belt is operated once every 24 hours to deposit the drying solid manure material into a line for the biomass dryer. As it waits, aerobic activity continues.
The dryer uses biomass fuel, typically feces that have already been dried and stacked within the system. Moist air from the dryer is vented through an all-weather biofilter to help mitigate odour concerns.
Before going to the dryer, the solid material is injected with products that have been previously extracted from the liquid, such as the ammonium sulfate, as well as other byproducts from the process such as lime sludge and burner ash.
The dried manure is pressed into pellets that go into bulk storage for sale as commercial fertilizer or for use in fueling the dryer.
“We expect a 10,000 head operation to produce about 2,500 tonnes of pellets every year with an NPK (nitrogen, phosphorus, potassium) of about 10-8-7.
“Sulfur is at four, calcium at four and magnesium at 1.4. That should sell for about $200 per tonne based on equivalent chemical prices. The bulk chemicals which are consumed in the system and which find their way into the pellets are lime and sulfuric acid.”
Van Slyke said the solid pellets are free of weed seeds and pathogens. They meet the U.S. Environmental Protection Agency’s Part 503 Class A requirements for biosolids.
“We have 100 percent capture of the nutrients that were in the manure, and it’s in the form of a salable, dry pellet fertilizer so it’s easy to handle.”
He said nutrients contained in those pellets burned for fuel are always recovered because his system recycles the ash from the dryer into the next batch of pellets.
The company was incorporated in 1993, originally to deal with vegetable waste. However, the needs of the hog industry prompted him to change his focus. The Closed Loop Manure Recovery System was developed in conjunction with the University of British Columbia and Hipp-Anvil Engineering.
Van Slyke attended Manitoba Hog Days because he and his partners are looking for a prairie hog producer who wants the first Closed Loop pilot project on his farm.
“We propose to build a 10,000 head treatment facility at no cost to the operator, but with his promise to buy it at a discount of 33 percent if we pass agreed milestones.”
For more information, contact Van Slyke at 604-736-4474 or visit www.hogmanure.com.
