November 18, 2011 | General

Increasing Capacity To Compost Food Waste


San Diego Pilot Compost CollectionBioCycle November 2011, Vol. 52, No. 11, p. 18
A change in its permit has enabled the City to expand its food waste recycling program, which includes a commercial collection route for small to medium-size generators.
Ana Lúcia de Carvalho

THE City of San Diego (City) operates the Miramar Greenery composting facility on land leased from the U.S. Department of Defense. The 74-acre facility is centrally located in the city and is inside the borders of the City’s Miramar Landfill. The Miramar Greenery composts residential and commercial yard trimmings and commercial food waste, as well as grinds clean wood, such as tree stumps and construction lumber.
The City has been composting food scraps since the mid 1990s. It started with a pilot program with grocery stores and discards from the central produce markets and then became a permanent program with the advent of military participation. The Navy began bringing sterilized food waste from ships returning to port and then added the Marine Corps Recruit Depot (MCRD) to the program. At that time, due to the Greenery’s permit specification, food waste had to be considered a pilot feedstock and the quantities it could receive were limited. Still, the program slowly expanded to include seven large single generators: MCRD, Point Loma Nazarene University, San Diego State University, Sea World San Diego, San Diego Convention Center, PETCO Baseball Park, and the San Diego International Airport. This controlled growth allowed the Greenery’s operations staff and recycling specialists to learn and adapt to processing this new feedstock.
Miramar Greenery food waste compost windrow
The composting facility is located less than one-quarter mile from a military airport runway, therefore bird control is a top priority at the Miramar Greenery. Because one grinder is used to process the bulk of the commercial and residential yard trimmings received, it was determined that food scraps would not be ground with yard trimmings to avoid the potential of having unprocessed food waste sitting on the tipping area waiting to be ground. Instead, food waste is received and immediately mixed with ground green waste and placed in a horse-shoe shaped windrow with a volume of up to 30 yards of food waste to 70 yards of ground yard trimmings. The mixed material is then moved and used to build straight windrows. Yard trimmings windrows are kept separate from food waste windrows during composting, and only mixed during final product screening.
Staff was determined to minimize contamination to no more than one percent. An approval system was put in place, where the recycling specialists visit potential participants’ sites, approve the logistics and train their staff. The first three loads from each new participant on the program are inspected upon arrival at the Greenery by a recycling specialist, along with representatives from the participant and the hauler. This “pilot” period allows for identifying any problems and areas where more training would be needed. Once participants have gone through the pilot, they are on a “permanent probation.” If loads received are contaminated, Greenery staff informs a recycling specialist who will work with generators to solve the problem. To date, no participant has needed to be eliminated from the program. This success is attributed to the upfront training and the clear communication on the low tolerance for contamination.
ROLLING OUT A COLLECTION ROUTE
In 2009, the Greenery expanded from 29 to 74 acres, and changed its permit, eliminating restrictions on the amount of food waste it could process. Both pre and postconsumer food waste are accepted. Since then, the program added a few other large single generators, such as the University of California San Diego, Science Applications International Corporation (SAIC), the Hilton San Diego Bayfront Hotel, Feeding America San Diego, and the Sheraton San Diego Hotel and Marina.
Although there are still large generators that don’t participate in this voluntary program, there was a significant demand from mid and small size generators for a system where they could also participate. The City reached out to haulers to establish a pilot commercial food waste composting collection route. In August 2011, the City started accepting food waste loads from the route, which includes seven of the 13 Albertsons grocery stores within the City’s limits (see accompanying article). One of the City’s franchise haulers, Waste Management, was the first to offer a food waste route in San Diego.
In the City’s nonexclusive franchise system, haulers charge customers for service, and pricing is negotiated directly with customers. The City does not set rates, and pricing is driven by the competitive market. The City offers an economic incentive by charging a significantly lower tipping fee for food waste to be composted at the Greenery as opposed to it being disposed as trash in the landfill. However, the $30/ton reduction in fees is more significant to single generators, as costs for route participants also include several collection containers, more time on each site to collect the load and a longer distance to travel in order to complete the route and take the load to the Greenery. Table 1 outlines distinctions between the single generator and route collection systems.
The route is serviced by a front-loader that can serve 32- and 65- gallon toters and up to 3 cubic yard (cy) dumpsters. The requirements are very similar to the single generator system, including the mandatory approval of logistics and staff training by a City recycling specialist. The only difference is the duration and accountability of the route loads’ pilot program. The pilot phase for the route will include three weeks of load inspections by a recycling specialist and a representative of the hauler for route loads.
With this successful experience, the franchised haulers, and other mid-to-small generators are lining up to expand the collection program to include hotels, restaurants, soup kitchens and corporations. The addition of the route and the inclusion of mid and small size generators has expanded the opportunity for businesses and institutions to participate in the City’s food waste composting program. Over the last six months, the Greenery has received approximately 180 tons of additional food scraps to be composted, with expectations to triple its total food scraps intake in 2012.

Ana Lúcia de Carvalho is an Environmental Specialist with the City of San Diego (California) Environmental Services Department.

Sidebar p. 20
Food Waste Collection Vehicles
A1 Organics, based in Eaton, Colorado, has been composting a range of organic waste streams at various sites in Colorado for many years. When the company expanded into composting commercial and institutional organics a few years ago, it decided to do its own collection. A1 started out with modified rear-loading trash trucks in Colorado, but as the routes and collection process grew, it transitioned into custom-built trucks provided by Martel Welding & Sons, Inc. in Tewksbury, Massachusetts. “One of the big challenges with the rear and front-loading trucks we were using was the tonnage we could handle without having to offload due to leaks, etc.,” says Kent Pendley, A1 Organics’ Chief Operating Officer. “The design we ended up with allows for quicker pickup of multiple totes, cleaning the totes versus exchanging them out with clean ones, and route capacity.”
Martel’s food waste collection trucks are designed for use with tote collection, explains Rick Martel. “The trucks can service totes ranging from 32- to 96-gallons. We can also customize the trucks to service 1 and 2-cubic yard (cy) boxes.” Truck bodies can be manufactured in lengths from 15- to 24-feet, with capacity ranging from 17 cy up to 32 cy. They have a sealed tailgate and are watertight. “We were the first ones to build this type of truck body 48 years ago,” adds Martel, “primarily for rendering collection. Essentially, we took that design and modified it for food waste collection.”
The back bucket on the truck is used to unload the totes. The open-top trucks are covered with a sliding canvas or roll-up top. Martel Welding can add a pressure washer so totes can be cleaned on-route, with wash water emptied into the truck. A scale system is available. A1 Organics purchased the 32-cy capacity truck bodies, but notes Pendley, “we typically call them full around 26 cy to ensure no road spillage during transport since they are open-top with tarps.” A1 has three trucks in total — two to service collection routes in Colorado, and the third for use in its Las Vegas program.
A1 Organics back bucket truck empties totes
“Each truck is equipped with a self-contained ‘Hotsy’ and washer storage system to allow us to provide the service that no one else in our market is doing,” he adds. “The ‘Hotsy’ system provides a high pressure wash with heated water. We add a sanitizer to the water storage system to mix with the water being used. The totes are cleaned after tipping and returned for use in the kitchen and/or collection areas.” A1 did not opt to install scales on its trucks.
A1 Organics’ facility in Keenseberg, Colorado has a Class 1 Permit to receive and compost food waste among other feedstocks processed there. “Our Stapleton facility in Denver is a transfer station which logistically allows us to receive, batch and ship collected food waste efficiently prior to sending to Keenseberg for processing,” says Pendley. “We are in the regulatory process of converting our headquarters operation in Eaton from a Class 3 Permit to a Class 1 Permit so we can more efficiently service the North Front Range area of Colorado. In Nevada, we operate a facility similar to the process utilized in Denver at our Stapleton facility. It serves as a transfer station that allows us to efficiently service Las Vegas proper and then we batch and transport the material to the Moapa Paiute Indian Reservation 20 miles out of town to our composting facility we operate on reservation grounds. Both in Colorado and Nevada, this transfer process allows us to move batched/preprocessed food waste to the composting facilities and to back haul completed, finished compost back to the transfer sites for sale and distribution.”
For food waste collection at casinos in Las Vegas, A1 utilizes a pumping program. “Casinos use the totes within the kitchen and collection operations and tip them as they are filled into a larger collection vessel on their docks,” explains Pendley. “We service those vessels daily, which includes a rinse down and clean out. The truck’s high-speed vacuum pressure further breaks down the solids to almost a slurry-type material. Eight-inch ‘vac lines’ are used in this process to enable complete removal of bones, turkey carcasses, etc. in the cleaning of the vessel.”


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