January 25, 2011 | General

From Dining Hall To Farm Power

BioCycle January 2011, Vol. 52, No. 1, p. 23
Somat Company, Elizabethtown College and Brubaker Farms team up to turn plate scrapings into energy, bedding material and fertilizer.
Dan Sullivan

KNOW thy neighbor. That could easily be the mantra of a partnership launched in fall of 2009 that includes Somat Company of Lancaster, Pennsylvania, nearby Elizabethtown College and Brubaker Farms.
For more than 50 years, Somat has been in the business of developing technologies that mainly help institutional clients reduce food-service labor hours and waste transport costs via use of the company’s patented shredders, dehydrators and pulping systems. Now that many of these clients are developing sustainability initiatives, Somat has turned the R & D spotlight on helping them achieve their goals.
“Our clients include hospitals, nursing homes – anybody who serves 500 meals-plus at a seating,” Somat Service Manager Tom Dalkiewics explains. The company prides itself on coming up with tailored solutions to individual customer’s needs. So when Elizabethtown College wanted to add food waste recycling to its portfolio of other sustainability initiatives, Somat was there to accommodate. From the college’s main Marketplace Dining Facility, closing the loop is readily apparent in many forms. A revolving carousel delivers students’ trays to the kitchen, where staff scrapes the food waste into a grinder – basically an industrial-sized garbage disposal – helped along by a recirculating river of water.
The pulped food waste slurry from approximately 2,400 meals served daily travels through 2-inch copper piping to an extractor, where it is screened out to 80 percent solids. These are placed into 32-gallon toters for a twice-weekly haul to Brubaker Farms in nearby Mount Joy, where they are added to the farm’s anaerobic digester. The recirculating grey water from the pulping process at the school cafeteria is changed with fresh water daily at an appointed shutdown time and gets pumped to an outside holding tank where it is mixed with the fats, oils and grease (FOG) also generated by the cafeteria. That mixture is pumped twice weekly through a 1 1/2-inch pipe (insulated and encased in a 6-inch pipe) into a mobile 1,200-gallon tank mounted to the front cargo area of a box truck, leaving room for the six to eight toters – weighing about 200 pounds each – of separated solids. From kitchen to truck and with the help of booster pumps, the food waste travels through more than 400 feet of piping.
Water recirculation is unique to Somat’s technology, says Dalkiewicz. “Elizabethtown’s recycled water is thick in order to limit the amount of trips to the farm – they try to keep it at about 5 percent solids so they don’t clog the pipes.” But the acidity of the concentrated food waste was damaging the grinder’s internal cast-iron parts, he says. “The parts were getting eaten away by the pH level, and so we switched to all stainless steel.” Somat’s pulper installation at Elizabethtown College is the first in the country where none of the outputs end up in the landfill – or the wastewater treatment plant. “I think it’s really a nice way to run everything full circle,” Dalkiewicz says. “Nothing is wasted, and everything gets completely used.”
Not only does Brubaker Farms receive a twice-weekly turbo charge for its digester, it also collects tipping fees that add up to about $400 a month. “From our standpoint, the tipping fee is considerably less than to take it to the landfill,” says Joe Metro, Elizabethtown College Director of Facilities Management and Construction. “Basically, I’ve cut my hauling costs in half. From our perspective, it’s a money saver.” Adds college Directore of Dining Services Eric Turzai: “When we have the compactor emptied, it costs about $1,000 to $1,200 each time – which was every two weeks without the pulper. Now it is the same cost, but only once every 4 weeks.” And the college is also realizing savings on its water bill by recycling 4,400 gallons a week of the water used in the pulping process.
The school belongs to a consortium of colleges working on sustainability initiatives, explains Turzai, and first got the idea for recycling food waste from Dickinson College in nearby Carlisle, Pennsylvania. Dickinson has a student farm that not only provides fresh vegetables to the dining hall and greater campus community but also produces compost from cafeteria food residuals (see “Recycling Food Waste: 101,” December 2010). “They planted the seed for us,” he says, adding that Elizabethtown College has its own modest half—acre farm on the 202-acre residential campus serving 1,900 students.

Brubaker Farms’ RCM International complete mix anaerobic digester – partially funded through a USDA Rural Development Grant and a Pennsylvania Energy Harvest Grant – has been operational since December 2007. Methane is chilled and filtered to reduce moisture before powering a Martin Machinery engineered 210 kW Guascor engine to generate around 200 kW/hour of electricity. The farm uses about 15 kW/hour for the digester project, with the surplus sold to PPL Corporation. The Brubakers buy back power from PPL to run the farm and for the past three years have been paying slightly less than they sell it for, but that arrangement is changing. The retail price paid by PPL used to include distribution and transmission costs, Brubaker explains, but the scenario moving forward won’t include these, thereby reducing the cost per kilowatt paid to the Brubakers by several cents. “I’m contemplating changing the way our electricity is marketed and utilized,” says third-generation farmer Mike Brubaker, who runs the farm with his brother Tony and father Luke.
“When we built the digester, it cost in the neighborhood of $40,000 to $50,000 to install extra lines, safeguards and controls, get our inspections and work with the utility to get hooked up and tied to the grid,” says Mike Brubaker. “It went pretty well for us. Because I had some good advice from some other farms that had done biogas projects ahead of us, they let me know what to look out for. We had good people on my team from the get go, and we worked together with the utility to help us recognize any potential speed bumps before we hit them.” In addition to energy production, other benefits of the anaerobic digester include nutrient management (nitrogen and phosphorous), odor control (odors are reduced by about 90 percent) and a surplus production of bedding material.
About 725 of 800 total milking cows along with 500 heifers of varying ages supply the digester with approximately 22,000 gallons of manure daily. The manure gets delivered to a 25,000-gallon reception pit and then into the digester four times daily via a Vaughn chopper pump. “Of that portion going in, it is testing usually at around 7-percent solids,” says Brubaker. A twin 25,000-gallon reception pit holds food waste from Elizabethtown College as well as what Brubaker refers to as “spot loads” of rejected milk from other area dairies and food processing waste from local manufacturers including candy rinse water and chocolate. “The food waste gets added to the manure right before the Vaughn unit pumps it into the digester,” he explains. “It’s added incrementally. We typically do not have the reception tanks full – we’re feeding into them and out of them all the time – but it adds a buffer. If something breaks down, we have capacity to back up a bit. And if we get a bunch of food waste all at one time, it allows us to take in several truckloads.”
Adjacent to the genset building, the digested solids exit a screw press separator via an overhead conveyor belt forming neat and fluffy rows onto a porous tipping floor. “The screw press screens out the liquid and takes about 4 percent of the solids out,” Brubaker explains. “The liquid portion is used to fertilize cropland. The solids are used for parlor bedding – 50 percent we use, and 50 percent is sold to other dairies. We’ve found this product actually increases milk quality.” Since switching to digested solids, the producing cows’ somatic cell counts are typically in the range of 120,000 to 160,000, Brubaker says, good enough that the cows’ milk commands a premium. Previously, the cows were bedded down on sawdust at a cost to the farm of $1,000 a load. Besides milk and some poultry, the 1,500-acre farm produces corn, alfalfa, soybeans, rye, wheat and grass hay, all mostly for feed.
“We’re only three years into it, and at this point we’re looking at a five-year payback – assuming we don’t have unexpected equipment issues,” he notes. The genset burns through about 880 gallons (around $8,000 worth) of oil a year and the Brubakers would like to find a way to utilize the waste oil generated rather than just give it away. The waste heat, however, is utilized to its fullest capacity. “Waste heat from the engine keeps the digester warm.” Warm air also is run through the floor to dry the solids after they come out of the screw press. The excess heat is also used to pasteurize waste milk to feed to the calves and heat the milking parlor as well as another outbuilding. “We’ve got good gas production and solids and have had good people to work with,” says Brubaker. “It’s been pretty smooth sailing up to this point.”

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