November 15, 2010 | General

Source Separation Mandate Drives Food Waste Composting

BioCycle November 2010, Vol. 51, No. 11, p. 34
Western Lakes Superior Sanitation District in Minnesota used an ordinance – combined with intensive training and education – to keep food waste out of the landfill.
Dan Emerson

AS THE provider of wastewater and solid waste services for a 530-square mile area in northeastern Minnesota, Duluth-based Western Lake Superior Sanitary District (WLSSD) is a special purpose subdivision of the state of Minnesota with the power to create ordinances. Under this authority, the WLSSD Board of Directors instituted a new regulation in 2007 mandating large-scale commercial businesses and institutions to separate organic materials from the trash for beneficial reuse. “Their program has been very successful, and a model for the nation,” says Ginny Black, organics recycling specialist with the Minnesota Pollution Control Agency (MPCA).
WLSSD has had a long-standing commitment to reducing the amount of solid waste going into landfills. In 2001, it opened a source separated organics (SSO) composting facility in Duluth adjacent to its yard trimmings collection site and wastewater treatment plant. The site is permitted for 7,900 tons/year of material – about half yard trimmings and half SSO from commercial and institutional generators and residents. At that time, WLSSD hired a part-time organics acquisition contractor and established a voluntary organics recovery program to provide feedstock for the composting facility. Only one hauler in the WLSSD region was providing collection services for participating businesses.

With capacity to compost more SSO, WLSSD evaluated options to increase diversion of those materials from its waste stream. One option considered was an ordinance, and in 2004, the District hosted a series of stakeholder meetings with organic waste generators and private garbage haulers to evaluate that option and establish a framework. Participants aired concerns and identified issues they believed hindered organics recycling in their operations. “Our intent was to recover more food waste by identifying and removing those barriers – both real and perceived,” explains Susan Darley-Hill, WLSSD’s Environmental Program Coordinator. “We targeted the large volume generators, while acknowledging that, collectively, residential food waste was also significant.” To service smaller generators and residents, the District also decided to establish several drop off sites for food scraps, including meat and dairy products.
A grant from MPCA enabled WLSSD to host the stakeholder meetings, carry out a 4-month pilot project to address issues specific to grocery stores and concurrently set up the first two locations for residential and small business food waste drop sites. Working from stakeholder and pilot study findings, WLSSD conducted several site visits and interviewed restaurant and institutional staff to distinguish real challenges from those that were often cited but not necessarily based in fact. For example, frequent employee turnover and presumed need for repeated and extensive training were raised frequently – a barrier that was unfounded in nearly every case. Employee buy-in was found to be the most critical to success.
During the stakeholder meetings, some participants indicated that they would not voluntarily participate in organics recycling for a variety of reasons. Some garbage haulers stated that an ordinance requiring source separation would be the only way to ensure sufficient customer density needed to make running additional routes feasible for them.
The WLSSD board concluded anordinance would be the most effective way to improve organics recovery within the district and reduce the amount of organic waste trucked to area landfills. Central to the mandate was its graduated rollout schedule and staff-heavy education program designed to specifically address stakeholders’ bona fide concerns.
“In addition to news coverage, we were also presented with an opportunity to let folks know the ordinance would be coming when we participated in a series of municipal workshops on fats, oils and grease in the community,” Darley-Hill says. “All those affected knew, more than a year in advance, that source separation was going to become mandatory for the larger generators. We offered incentives for early adopters – bins, compostable bags and as much staff training as was needed.”

The ordinance became effective in November 2007, under a rolling implementation schedule that now encompasses 150 businesses and organizations within the WLSSD service area. About 60 local businesses and institutions were already participating voluntarily at that time. The ordinance covers hospitals and other care facilities licensed for more than 100 beds, grocery stores larger than 7,500 square feet, food manufacturers and processors of more than 5,000 square feet in size, and secondary or postsecondary educational institutions with more than 1,000 students.
To determine those size points, WLSSD used, as a baseline, information from research conducted by Metro’s Solid Waste and Recycling Department in Portland, Oregon that included estimates of the quantity of food residuals generated by sector. It also used categories already established by public licensing agencies, focusing on businesses and institutions that were the largest generators of preconsumer organics in the district’s waste stream. WLSSD set guidelines – such as square footage for grocery stores and number of beds for hospitals – intended to capture that material.
“We established these limits using the North American Industry Classification System (NAICS) and local counties’ Department of Health licensing databases,” says Darley-Hill. “Using these tools, we discovered natural break points which helped define limits that were less arbitrary and better indicators of residual volume. For example, small grocery stores primarily stock prepackaged food, have a very limited produce section, and usually no deli or bakery – typical sources of the large volume residuals targeted for diversion. Similarly, the larger nursing care and hospital facilities generate far more residuals than small assisted care establishments housing 12 residents. This was borne out when we added this last sector in 2010 (assisted living) under an ordinance modification and then ended up granting exemptions to nearly all that were in that specific category.”
An important consideration while determining the size sectors was the opportunity for the generator to realize economic benefits. “The larger entities were more likely to realize benefits by separating and diverting the residuals that otherwise would be subject to a tipping fee, 17 percent state tax, and the District’s solid waste management fee,” adds Darley-Hill. “Food-centered businesses would be able to recoup the cost of an additional organics pick up by cutting back on the frequency of regular trash pick ups due to decreased volume and reduced odor-causing material. They would be more likely to reap the benefits if both pre and postconsumer food residuals were removed.”
Implementation started with grocery stores, followed by large restaurants, colleges and hospitals, and finally medium-sized restaurants. This allowed adequate time for WLSSD to develop and deliver educational materials, signage and training specific to those entities, “using a bullet to hit the target rather than scattershot,” Darley-Hill notes. “We’ve put a lot of staff time into workshops, working one-on-one with restaurants and conducting training. We estimate about four hours of time for each of the entities that generate food waste.”
The undertaking has “been pretty intense, but that is what has made it successful,” she adds. Waste generators have proven “more receptive to face-to-face visits, rather than a mandate from on high with no one person they can talk to or complain to. That’s been a real keystone.”
Along with the targeted waste generators, a number of churches and special events are participating. “The convention center here is very much on board with the program and incorporates food waste recycling into all they do, from weddings to national conferences,” says Darley-Hill. “This is quite a feat from a venue that serves more than one million guests each year.” Promoting “waste-free” events has been a two-fold marketing tool for WLSSD: reducing waste and promoting its composting program. One example is the annual Empty Bowl fundraiser for the Second Harvest food shelf, which serves 2,000 people in a 6-hour time frame. All the food waste is composted.

WLSSD provides six residential/small business food waste drop-off sites at local businesses, its recycling facility, and its SSO composting facility. The yard trimmings composting site accepts grass clippings, leaves, brush, holiday trees and small quantities of sod and dirt. The drop-off sites service the greater Duluth area, which includes the city of Duluth, plus five rural townships and two suburbs – a total of 43,895 households. Residents in the neighboring city of Superior, Wisconsin also use the drop-off sites, adding another 11,515 households. WLSSD purchases compostable bags and provides them free to drop site users. Doing so helps reduce compost contamination and also keeps drop-off bins at host sites cleaner. WLSSD accepts only compostable, BPI-certified bags.
Drop site use for food waste has grown steadily since 2004. The dropoff sites receive an average of about 45 tons/week of food waste and 30 tons/month of yard trimmings. “This can fluctuate a bit with seasonal variations in tourism and produce, but we have also seen an increase with additional organic residuals coming from outside the district,” says Darley-Hill. Overall, the District receives about 5,000 tons/year of wood, brush, and leaves.

There is no tipping fee for clean, separated organics delivered directly to the composting site. The public yard trimmings site next to the composting facility has free drop off for leaves and grass and an $8/cubic yard charge for brush. The tipping fee for solid waste at the transfer station is $45/ton with an added 17 percent state tax and a solid waste management fee based on volume. The quantity of food waste has increased significantly this year, since the ordinance was fully implemented. The goal is 75 tons/week of throughput.
Tim Lundell, a senior solid waste operator, helps oversee WLSSD’s composting operation. Rear-loading and large roll-off garbage trucks unload food waste on a 50-ft by 50-ft concrete mixing pad surrounded by a push wall. A retention pond collects any runoff liquid from the delivery pad and composting site. The feedstock is fed into a Schuler mixer in 10,000 pound batches and mixed for about 15 minutes “until we get a homogenous mixture,” says Lundell.
Yard trimmings and discarded grain from local shipyard grain silos are added to absorb moisture and add bulk to the mixture. After mixing, the mixer’s conveyor belt empties the material onto a bed of wood grindings, screening overs, and leaves about 10 to 12 inches deep, “just enough to contain the mixture.” A front-end loader blends the material further by rolling it back and forth. “We’re shooting for 45 to 55 percent moisture,” explains Lundell. “If the material is too dry, we add fish manure from a local fish hatchery.” Fish waste also is accepted a the facility.
The mixed material is laid out in aerated static windrows around 150-ft long, 7-ft tall, and 12-ft wide at the base. A blanket of leaves is added at the end of each work day to serve as a biofilter and discourage gulls and other birds from feeding on the piles.
Windrows are typically constructed in about one week’s time but that is contingent on how much SSO is delivered. Once complete, the windrow sits undisturbed, for 8 to 12 weeks, and then is put through a McCloskey trommel with a 3-inch screen and placed into intermediate curing piles for another 8 to 12 weeks. It is then screened to a half-inch and the product is cured, tested under STA (Seal of Testing Assurance) specifications, and sold as Garden Green® compost. Finished compost is sold in bulk and as a bagged product.

WLSSD produces an average of 2,500 to 4,000 cy/year of finished compost. Compost is sold directly to the public in either 40-lb bags at $4.50/ bag, or in bulk at ($22/yard self-loaded, or $27/yard loaded). Bagging is done manually from mid-March to mid-April by a contractor using WLSSD’s bag-sealing equipment. “Bagging is very labor-intensive,” says Lundell. “We don’t have an automatic bagger, just bagging funnels, so it requires one person shoveling and one holding the bag.”
The 40-lb. bags are placed on pallets and shrink-wrapped, for pick up by local retailers. About a dozen garden-center retailers in the Duluth-Superior metro area sell the product seasonally. “We usually sell everything we bag during the year,” Darley-Hill explains. “If we need more compost, we can always bag more. We do put a high priority on making the material available to our residential customers, so we monitor our sales to large-scale users carefully to ensure a continuous supply is available for residents.”
Sales have grown steadily, from 4,242 bags in 2005, to 8,443 bags in 2008 and 11,112 bags in 2009. Hiring a firm to design “an attractive bag that looks good next to the other, commercial brands has made quite a difference in sales,” she adds. WLSSD staff do direct marketing at local special events, gardening workshops and community festivals. Mass marketing is accomplished through newspaper advertising and articles in the district’s newsletter. “All of this is done in conjunction with our public education to promote waste reduction, recycling, and higher-use objectives,” Darley-Hill says. The marketing also emphasizes the fact that Garden Green “goes back out to the people who are sending us material, whether it’s yard waste or food waste,” she says.
WLSSD’s emphasis on serving the local region has been important to the program’s success. “The facility is properly sized to meet community needs,” she concludes. “Operations and sales are local, minimizing energy expended in transporting incoming feedstock and finished compost product to point of sale. Close involvement with our stakeholders promotes good quality control. Although the ordinance is fully implemented, our compliance checks and troubleshooting are ongoing. This keeps us connected and prevents problems from getting too big to handle.”

Dan Emerson is a free-lance writer based in Minnesota.

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