Manure Manager

Features Applications Swine
Turning brown into Green

April 24, 2008  by Ray Ford

Construction is well underway on a new $9.5 million facility for Premium Standard Farms that will turn hog manure into an odorless organic fertilizer that’s perfect for the putting green.
Construction is well underway on a
new $9.5 million facility for Premium Standard Farms that will turn hog
manure into an odorless organic fertilizer that’s perfect for the
putting green.

    As a hefty dose of nutrients in an easy-to-deliver slurry, pig manure has a lot to recommend it. But with an aroma likely to put a duffer off his swing, it’s never really found its place as the fertilizer of choice on American golf courses.

    Now a US company is bridging the gap between finishing barn and fairway, thanks to a process that takes hog manure and turns it into a dry, odorless organic fertilizer that’s perfect for the putting green.

    “We have the philosophy of trying to make something valuable out of the manure,” says Dave Townsend, vice-president for environmental affairs at Premium Standard Farms. “We want to offset the cost of the technology required to process the manure, but we also want to do something beneficial with it, rather than just treating it as waste we’ve got to do something with.”

    The result is a process, now under construction, that is both complex in design and elegantly simple in operation. Based at Premium Standard’s Valley View Farm near Green City, Missouri, the system uses an approach developed by Crystal Peak Farms to combine anaerobic digesters, a centrifuge dewatering system, an ingenious freeze-thaw system to capture nutrients from the effluent, and the dryer-fertilizer facility.

brown1The digesters at Premium Standard’s Valley View farm will replace a lot of lagoon capacity. The farm used to have fourteen 20-million gallon lagoons, which will be replaced by five million gallons in digester capacity, representing a huge reduction in volume.

    The end result is a granulated product that “doesn’t have dust and doesn’t have odor. It’s in nice, solid black granules. It handles like a traditional fertilizer and has zero odor,” says Townsend.

    In Valley View’s case, litigation is the mother of invention. Premium Standard is a large, vertically integrated company that controls its own genetics, formulates its own feed, raises hogs in Texas, North Carolina, and Missouri, and processes them at two company-owned packing plants. For most of its history, the company used conventional manure handling techniques, housing pigs on concrete slatted floors, collecting the slurry in lagoons and land-applying the manure.

    Problems with land application—and resulting legal disputes—drove Premium Standard to seek a better way. “Land application is a challenge, and pumping effluent through the distribution network creates risks,” Townsend says. As a result, “there had been a lot of litigation and challenges.”

    Turning the manure into commercial fertilizer allows Valley View to avoid land application problems, meet environmental commitments with the State of Missouri and the US Environmental Protection Agency, and generate a value-added product. “When we looked at the options, this one had great potential,” Townsend says.

    “The cost of this project is $9.5 million. It’s a tremendous amount of capital to spend on a hog farm, even one this size. But it should operate at a break-even level, and down the road it has the upside potential to generate profit.”

    The system is also guaranteed to raise eyebrows. What other manure treatment approach creates miniature glaciers on giant plastic-covered “ice fields”?

    “People always look at me kind of strange about the ice field,” Townsend admits.
    Whether it uses an ice field, settling basin, or an anaerobic digester, the Valley View process separates the manure into component parts to retain nutrients and ease handling. In the final step, it recombines those parts at a fertilizer plant slated to produce more than 8,000 tons of fertilizer and provide 11 jobs.

    “If you look at the manure, basically what you have is gas, water, and fertilizer. It’s readily available as these three components,” Larry Sower, founder of Crystal Peak Farms and the designer of the approach, said in an interview before his death late last year.

    Sower’s technique uses the gas produced from the manure to heat and process the fertilizer, and diverts the water to irrigate nearby fields. The result is “a zero-discharge facility that deals with all the major problems” stemming from manure, and an on-farm fertilizer plant producing a 12-8-8 mix that’s ideal for turf.

    Valley View is home to about 107,000 hogs housed in barns with concrete slatted floors connected to a conventional lagoon system. Each barn houses 1,000 hogs. Individual sites feature eight barns and a lagoon. The entire Valley View operation includes 14 of these sites, each featuring eight barns and a lagoon, scattered over several thousand acres.

    Rather than flushing manure from the grower-finisher barns into lagoons, the Valley View approach substitutes an internal recirculation process (IRP) that flushes the barns and runs the slurry through a pump station equipped with a chopper, grinder, and slurry pump. The flush water is drained into concrete pits, where the slurry settles and the thickest goo collects on the bottom. Meanwhile, the watery liquid at the top is pumped out to flush the barns.

    Because the liquid used for the flushing is still fairly fresh, and hasn’t developed a heavy load of odor-producing anaerobic bacteria, “the environment inside the barn is still fine,” Townsend adds. “The employees said they felt there was less odor than with the conventional system.”

    The farm’s five anaerobic digesters are the first step in breaking the waste into its constituents. The heavy slurry from the bottom of the pits is pumped as far as two miles (3.2 kilometres) to the digesters, which act as a 24-hour diner for the kind of microbes that thrive in a low-oxygen environment. The bacteria chew up the solids in the manure,
belching out a “biogas” that’s 65 percent methane.

    By ensuring the thorough digestion of cellulose and larger solids in the manure, the microbes help the system produce evenly sized, firm fertilizer pellets at the other end of the process. The biogas, in turn, is collected, processed to make it burn more cleanly, and piped to the fertilizer plant where it supplies the energy to dry and char the pellets.

    Sizeable though the digester system is, the digesters are a lot smaller than the lagoons they’re replacing. “The farm used to use fourteen 20-million-(US) gallon lagoons,” Townsend says. “Those will be replaced by five million gallons in digester capacity, so that’s a huge reduction in volume.”

    Once the digesters have drawn off the biogas, the next step is to separate the manure into its solid and liquid portions.  
    The first move is to pump most of the digested slurry out of the digester (about 30 percent remains behind to jump-start the next batch) into a 145,500-gallon settling basin. The basin is a simple gravity system where the solids sink to the bottom, and the more watery portion stays
at the top.

    As the slurry settles, the liquid at the top is pumped out, treated with sulphuric acid, and stored in a pond. The acid drops the effluent’s pH to about six, keeping the nitrogen bound up in the liquid rather than allowing it to escape as ammonia.

    The thicker portion at the bottom of the basin is pumped to one of two Bird centrifuges—large cylinders that wring the water from the solids. “The manure comes out of the centrifuge at 25-30 percent solid, but now it’s in a form called ‘cake’, where it will pile up and stack,” Townsend says.

    Perhaps the most remarkable wintertime sight at Valley View is the ice fields in operation. The fields occupy two levelled-off areas, one 10 acres and another three acres, each studded with irrigation nozzles, bermed on four sides to prevent run-off, lined with plastic and draining to a catch basin in one corner.

    During freezing weather the nozzles spray effluent from the storage pond into the cells in a bid to separate the liquid’s salts and soluble nutrients from its water. The process is familiar to anyone who’s ever accidentally frozen a bottle of beer. As the brew chills, the water turns to a slushy ice while the alcohol remains in its liquid form. A similar process takes place on the ice fields. As the mercury falls, “you start building an ice pile around these spray nozzles,” Townsend says. Another portion—containing the nutrients and salts—has a much lower freezing point. It flows off the ice and into the sump in the corner of the cell.

    The brine, in turn, is pumped off into a storage pond, where it will be held until it’s mixed with the manure “cake” to produce fertilizer. Dividing the liquid into brine and water “is the most important part of this process, because nearly two-thirds of the nutrient value is in the liquid,” Townsend says. “By capturing those nutrients in the liquid and blending them with the solids we’re able to achieve 12-8-8 fertilizer, because we’re extracting all the nutrients from both the solids and liquid.”

    Since what freezes will also thaw, the system must keep the water separate from the brine after the ice begins to melt. To tell water from brine, the system uses sensors that measure the conductivity of the fluid in the catch basins. Because of its salt content the brine is highly conductive, and the sensors tell the pumps to send that portion to the brine pond. The purer water portion has much less salt, and therefore is less conductive.

    As the ice piles melt on mild winter afternoons, the sensor detects the fall in conductivity and diverts the water to a storage pond, where it is held for irrigation. “Our philosophy is to produce a treated liquid with much less nitrogen, so we don’t need as many acres to apply it on.”

    The Valley View area has about three months of freeze-thaw weather. Aside from cold snaps, the typical pattern is chilly, below-freezing nights followed by milder days. “In the winter we store up enough brine to run the plant for a year,” Townsend says, adding the system “reduces the amount of water we need to evaporate in the dryer, limits energy costs, and captures nutrients.” About 70 percent of the effluent ends up in the irrigation pond, while the remainder is stored in a brine pond.

    After all the effort to divide the manure into components, it’s finally reconstituted in a new form during the fertilizer manufacturing process. In the first stage, a paddle mixer kneads the cake and the concentrated liquid together before sending the mix into the granulation/drying system. As the manure mix is fed into the spinning, 42-foot dryer, it rolls and forms into granules. The granules are cooked over a biogas flame in a chamber reaching temperatures as high as 1,200 degrees F. A second, smaller combustion chamber is used to char the granules, burning off the compounds that cause odors and making a firm, stable pellet. After cooling and screening, the granules are stored for marketing by the J R Simplot Co.

    The fertilizer plant “is very small compared to a commercial-scale plant, but it still needs a lot of equipment,” Townsend says. “One-third of the investment is tied up in the fertilizer plant.”

    With an investment of that size, Premium Standard wanted to ensure the system would work well before it broke ground at Valley View last July. Although the approach hasn’t been tested in a complete pilot plant, components were field-tested at different Premium Standard operations. Anaerobic digesters were built from 15,000-US gallon steel tanks. The freeze-thaw system was tested on a half-acre plot. “We shipped dewatered manure all the way to Wisconsin” for a processor to produce fertilizer that could be shown to potential buyers.

brown2Construction is already well underway on the new system at Valley View Farm. The fertilizer operation is scheduled for start-up in March, with fertilizer being commercially available this summer.

    The second concern was to maintain simple, low-cost components. “Even though this thing looks really complicated and it’s got lots of parts and components, it has been designed to be as farm-friendly as possible,” Townsend says.

    “Our goal was to keep the technology involved as simple as possible,” adds project manager Ray Gibson, who is overseeing Valley View’s construction for the Utah-based engineering firm Roberts and Schaefer Co. “Where we could, we tried to keep costs low and use common, simple components.”

    Digesters, ponds and pits are made of earth and lined with high density polyethylene. Used centrifuges were bought, one locally, and another from KonicaMinolta in New York State. The system is linked together by about 40,000 feet of pipe (HDPE underground, because it flexes rather than bursts, and PVC aboveground).

    Most of the technology in the system can be bought off the shelf from existing suppliers. The granulation equipment came from FEECO International Inc of Green Bay, Wisconsin. The HDPE liner came from Environmental Fabrics Inc. Pumps, nozzles, and pipes came from established suppliers including Flygt, Gould and Gorman-Rupp. Given the run of up to two miles from barn to digester, designers opted for the pushing power of the Vogelsang positive displacement pump to drive the effluent (at roughly six to 10 percent solids) to its destination.

    While attention has focused on getting the system built and operating, a key part of the strategy involves marketing the fertilizer, and promoting the technology that produces it. “Technical success doesn’t necessarily guarantee marketing success,” adds Keith McGinnis, general manager of Crystal Peak Environmental. Crystal Peak Environmental is a joint venture of Premium Standard Farms, Crystal Peak Farms, and Roberts & Schaefer, formed to market the Valley View technology.

    To ensure market acceptance, “we test-marketed the product on golf courses in Hawaii, and I think it’s going to be very well received,” McGinnis says. To bolster the appeal of the fertilizer, McGinnis is also seeking organic certification for the product, and working closely with distributor J R Simplot Co.

    Back at Valley View, Townsend says full operation is slated for start-up in March. Fertilizer from the plant should be hitting the fairways as early as this summer, as Valley View tees off in its effort to link pork production and putting greens.


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