BioCycle March 2011, Vol. 52, No. 3, p. 74
Reinford Farm in Mifflintown, Pennsylvania receives 60 to 70 tons/week of commercial food waste, which it processes with manure from about 500 cows.
Molly Farrell Tucker
AN anaerobic digester on a 180-acre dairy farm in Mifflintown, Pennsylvania is doing some serious multitasking. It is reducing manure odors, producing electricity, creating cow bedding, drying grain, pasteurizing calf milk and providing additional income for the farm. Construction of the complete mix digester system at Reinford Farm began in August 2007 and it has been operating since February 2008.
Feedstocks for the digester include manure from Reinford Farm’s 470 milking and dry cows and source separated commercial food waste. The digester was sized to process manure from up to 1,000 cows, allowing room for future growth. Because codigestion of manure and food waste was part of the plan when building the digester, it was constructed with a second liner on the bottom to meet permit requirements. “As long as I put the food waste into the digester and stay in compliance with my nutrient management plans with the acreage we have, I’m fine,” says Steve Reinford.
In 2010, the farm began receiving food waste from 40 Walmart and Sam’s Club stores in the region. Walmart associates are trained to separate packaging from the food waste, which consists primarily of nonedible produce and bakery waste, and a small amount of dairy. (Meat waste is managed under separate rendering contracts.) The food waste is stored at the WalMart and Sam’s Club stores in 3- and 4-cubic yard (cy) leak-proof, sealed, locked receptacles specially designed for food waste. Organix Recycling, Inc. collects food waste from each store at least once a week, as far north as Mansfield, Pennsylvania (about 120 miles distance) and as far south as Shrewsbury (about 85 miles).
Organix Recycling delivers the food waste to Reinford Farm in tractor trailers. “We have had very few problems with contaminants such as glass, plastics, etc.,” says Reinford. “The driver rejects contaminated loads at the source, but sometimes we may find a few pieces when the material is delivered to us. It’s removed ahead of our process.” Reinford Farms receives a tip fee for the food waste, and is getting about 60 to 70 tons a week. Reinford estimates that the farm could process double that amount.
Organix Recycling provides food waste hauling services in Illinois, Indiana, Missouri, Arkansas, western Tennessee, western Kentucky, eastern Pennsylvania, northern Louisiana, northern Mississippi and southern Florida. It diverts millions of pounds a month of source separated, preconsumer food waste to permitted recycling outlets, including anaerobic digestion and composting facilities and animal feed manufacturers in 12 states on behalf of Quest Recycling Services, LLC, based in Frisco, Texas. Quest Recycling is the contractor Walmart selected to manage its food waste diversion program nationally.
“Before we started our operation in Pennsylvania, we researched all permitted outlets that could handle food waste, and came across Reinford Farm’s dairy digester on the EPA/AgSTAR web site,” says Andy Taylor, National Accounts Manager for Organix Recycling. “The farm’s owner, Steve Reinford, is a modern visionary and could see the benefits of working with Organix and being flexible on handling the food waste. He installed a receiving area allowing easy access for our machinery to tip our loads daily.”
PREPROCESSING STEPS, DIGESTER OPERATIONS
The food waste is emptied into a holding pit and then loaded into a grinder designed and built by Reinford. “I took a forage chopper and revamped it to suit our needs,” he says. The food waste is ground for 30 to 45 minutes and then added to a concrete influent tank where it is mixed with manure.
The cow manure in the main freestall barn is removed with continuous, automatic alley scrapers; manure in the second freestall barn and dry cow barn is skid-steer scraped. The manure is gravity-fed into the influent tank, where it is mixed with the food waste. The mixed materials, at about 14 percent solids, are gravity-fed through a six-inch pipe into the digester every four hours for 15 minutes. “Everything is automated so we don’t even have to push a button,” says Reinford. “It takes about a half hour every day to process the food waste. Four of our employees know how to deposit the food waste into the digester, so whoever sees that there has been a delivery and can fit it into their schedule, gets the job done.”
The mesophilic digester, designed by RCM International, LLC, operates at a temperature of 100°F. Contents are mixed by three Houle mixers, which help to maintain a high level of bacterial activity. The mixers run twice a day for 15 minutes. The top of the vessel is covered with 60-mil thick black plastic to contain the biogas.
The biogas is piped underground and pretreated with an RCM hydrogen sulfide scrubber before it is sent to a reconditioned, 1,200 rpm Caterpillar G342 engine coupled to a 140 kW single-phase, 250 volt AC, 60 hertz auto flare generator. The biogas produces an average of 140 kWh/hour of electricity.
Reinford Farm has a commercial power purchase agreement with Pennsylvania Power and Light (PPL) Electric Utilities Corporation. All the electricity produced is sold to PPL for approximately 13 cents/kWh. The farm purchases any electricity it uses at a residential rate of approximately 8.9 cents/kWh.
DIGESTED SOLIDS, HEAT RECOVERY
The digested manure is stored in a 20-foot long by 20-foot wide and 12-foot deep pit until it is pumped into a building where a screw press separator with a 5 hp motor separates the solids and liquids. The solids fall directly into a storage bay and are used for bedding. Reinford Farm uses about one-third of the digested solids; the remainder is sold to two farms for bedding. Liquid effluent flows by gravity into a 2.5 million gallon storage pond. It is applied to the farm’s 1,000 acres twice a year by both drag hose and tanker truck.
All waste heat from the gas engine is utilized – from the engine water jackets is to heat water to pasteurize milk for new born calves; from the engine’s radiator to dry grain in a grain bin; and from the engine coolant and exhaust to heat the large Reinford farmhouse, as well as provide radiant heat for the shop floor and hot water in the milking parlor. In fact, notes Reinford, the waste heat has replaced an oil-fired boiler in the milking parlor that used 200 gallons of fuel oil every three weeks. “It’s amazing that we haven’t had a fuel truck here in over two years,” he says. “We still have leftover heat, which we’ve been looking at using to dry manure solids for bedding.” Energy savings to the farm are more than $6,000/year.
The farm also receives approximately $650/month for renewable energy credits through 3Degrees, an environmental commodities sales, trading and advisory firm in California. “That check pays for the groceries,” adds Reinford.
The anaerobic digester system cost a total of $1.1 million. RCM International helped Reinford Farm apply for grants. The farm received an Energy Harvest grant of $285,000 from the Pennsylvania Department of Environmental Protection; a U.S. Department of Agriculture (USDA) grant of $203,600; a USDA Environmental Quality Incentives Program grant of $40,000; a Resource Enhancement and Protection Tax Credit of $90,000, and a $135,000 loan from the Pennsylvania Department of Agriculture’s Machinery and Equipment Loan Fund.
For Organix Recycling, which just started collecting and hauling food waste about a year ago, working with processors like Reinford Farm makes a huge difference in the diversion program’s success. “As food waste collection on such a large scale had never been done before, we came across a few challenges including finding the right receptacles, the right machinery and most of all the right recycling facilities,” says Taylor. “We’ve worked hard to make this service work. We now have the right receptacle and machinery, and because of the support from Steve Reinford and all of our current outlets, we are stepping in the right direction regarding facilities. But more are needed.”
Molly Farrell Tucker is a Contributing Editor to BioCycle.