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Cleaning the Plate: Preliminary results look promising for a 15-month pilot project to compost food waste generated by the commercial and institutional sectors. by Monica Duebbert, Richard Flammer and David J Williams A state-funded food waste composting pilot project is showing communities that source separation and outdoor. open-windrow technology can be used effectively to handle and process Illinois’ commercial and institutional food organics waste stream with a minimal amount of problems. The 15-month project, which began in February 1994, is the first in Illinois to address the viability of an integrated approach

applying source separation, open-windrow cornposting and highquality finished compost production methods to commercial and institutional food waste. Approximately 10 tons of food preparation waste, including meat, from 13 sources are collected each week and delivered to a 1½-acre all-weather composting pad made from crushed recycled concrete and brick located at the University of Illinois.

Monica Duebbcrt is program and communications coordinator for the Office of Recycling and Waste Reduction at the Illinois Department of Energy and Natural Resources. Richard Flammer is senior project manager for Organic Recycling, a minority-owned business located in Joliet. Illinois. David J. Williams is professor of horticulture. College of Architecture at the University of Illinois at Champaign/Urbana.

Follow the money The project is a cooperative effort between the Illinois Department of Energy and Natural Resources, University of Illinois at Champaign/Urbana, Community Recycling Center in Champaign, and Organic Recycling Inc. of Illinois. Grants were provided to project participants from ENR’s Office of Recycling and Waste Reduction to cover a portion of their project costs. “Food waste is a category of the solid waste stream with tremendous recycling potential,” states ENR director John S. Moore. “Approximately 8 percent of the solid waste stream currently entering Illinois landfills is composed of food wastes. This project is focused on developing technical and economic data associated with collecting and composting organic food waste that can be applied to encourage a reduction in the amount of such waste deposited in Illinois landfills.” An earlier ENR-funded study conducted by the Community Recycling Center in Champaign, Illinois found food waste composed 30 to 50 percent of the waste streams from grocery stores and restaurants in the Champaign/Urbana area (see “Commercial food waste from restaurants and grocery stores” in the February 1993 issue). In general, food waste generated by grocery stores tends to be cleaner than that from restaurants, and food from grocery stores is often sur-

a

Food waste can be composted with less technology and reduce cost in outdoor open-windows.

a Layering wood chips in the compost pile controls odors and deters birds and rodents.

a Contamination, at less than 10 percent of delivered food waste, is managed by manual removal and screening.

a

Finished compost is suitable for soil amendment or mulch.

prisingly homogeneous, as if all the past-date cabbages or all the apples were set out for collection on the same day. ENR provided $218,505 in state funding for the project. The U of I College of Agriculture, Department of Horticulture received a $55,000 grant for site construction and dayto-day operation expenses, and additional funding was provided by the U.S. Army Construction Engineering Research Laboratory in Champaign and the Institute of Environ-

mental Studies at the University of Illinois. CRC was awarded $66,800 for collection and outreach programs. Organic Recycling Inc., received $96,705 for providing technical assistance and overall project management. Data acquired from this project will help ENR, communities and food waste generators gauge the feasibility of larger scale food organics projects and will serve as a mode] for promoting and funding future openwindrow food waste composting efforts. Midpoint project data are already being used by the Illinois Compost Quality Standards Technical Advisory Committee and the Illinois Environmental Protection Agency in developing state regulations on composting the organic (other than yard waste) portion of the waste stream. Collection and outreach At present, 13 waste generators are participating in the study, including four grocery stores, four restaurants, two schools, a nursing home, a food bank and a U of I residence hall cafeteria. Each generator is given a collection container ranging from 90 gallons to four cubic yards. The container size is determined by collection frequency and the space available for collection, though most sites use either a 90-gallon or a two-cubic-yard container. All containers are tipped into a 17-cubic-yard packer truck. The collection frequency for each generator varies from two to six times a week, depending on the volume produced and the preference of the generator. To maintain convenience for the generator and to keep collection costs at the same rate, collection frequency is the same as garbage. Initial outreach efforts by CRC yielded positive results from the majority of the waste generators. Levels for inorganic contaminants (such as plastic wrappings and tin cans) were typically low in the start-up and firstquarter phase of each participant’s waste generation, but grew in the later stages, perhaps because of personnel changes at generators or the absence of ongoing education efforts. Also, in summer months, some generators had problems with maggots and flies in the food waste and solved them by using plastic bags to collect food waste materials, which aggravated the contamination problems. Instruction on preparing materials was catered to the structure and needs of individual participants. Although some businesses requested CRC to conduct a training session for all of its staff, others felt management personnel could adequately transfer information to their employees. Both education methods showed varying degrees of effectiveness. Follow-up instructional meetings were necessary when management or staff turned over and when organic contamination levels visibly increased.

Businesses that responded enthusiastically and showed interest in environmental issues when they were first contacted to participate increased the volume of diverted food organics over time. Businesses whose interest was focused more on the financial rewards of food organics diversion recovered amounts below what could be expected from their stream. Processing methodology Food waste is tipped directly into a 12” to 15” thick pad of leaves and, after accessible contaminants are manually removed, it is covered with wood chips. In spite of the fact that food organics are delivered frequently and in low volumes, the stipulated recipe (one part leaves, three to three-and-a-half parts wood chips and one part food scraps) and the dimensions of the windrow are followed; chips are applied in thin, successive layers of four to six inches, the minimum necessary to biofilldors and discourage vectors. The food waste composting pilot project got off to a rough start. The composting site was originally scheduled to begin operations in the autumn months, but permitting problems delayed its opening until February, when leaves and wood chips, used as part of the composting “recipe,” were frozen. Because temperatures were well below freezing during the first segment of the project, the first batch of layered food waste and ng agent was allowed to heat up without mixing or aeration. Once the material retained a temperature range suitable for miial activity, it was aerated. Subsequent res were mixed and aerated on a 28-day cycle using a windrow turner. Most plastic bags were coincidentally reed by the operation of the windrow turner. Manual decontamination, i.e., hand picking is carried out after each turning, with the bulk of items removed consisting of plastic bottles, cans and glass. After three months of composting, the material is left to cure for one month and is then set aside for screening.

logical oxygen demand levels. Water samples were collected upstream and downstream of the pad and tested for metals, salmonella and fecal coliform. Because vectors, odor release and migration are primary concerns when composting food organics in the outdoor, open-windrow method, extensive monitoring procedures were established for gauging these two parameters. Checkpoints at measured, incremental distances are used to record the migration potential of odors. Nocturnal visits to the composting site and wildlife counts are carried out to determine if the feedstock was attracting rodents or vectors of any kind.

Conclusions At the halfway mark of this study, primary data and initial observations by the participating investigators indicates a strong potential for the outdoor, open-windrow method to be a viable system for composting the commercial and institutional food organics that are present in the Illinois waste stream. When the site operator was asked to identify the most critical processing difference between yard debris and food waste composting, he unhesitatingly stated that compost site operators must begin to process food scraps immediately, or the site will begin to experience odor and vector problems.

Onsite monitoring, sampling and testing The active windrows are monitored daily for temperature, odor, vectors and physical characteristics. Using measuring devices called thermocouples, temperatures are recorded at depths of 15,46 and 91 centimeters, with 12 readings taken at each depth for each windrow. After three months, temperature monitoring is reduced to once a week. Each week, oxygen and moisture level readings and sample collections for aciditysalinity (pH), electrical conductivity, organic carbon, nitrogen and carbon-tonitrogen ratios are taken. Random core samples are also collected for periodic monitoring of heavy metals, fecal coliform and bioResource Recycling January 1995 47

In general, odors have been managed by using partially composted wood chip biofilters and applying the same rules of thumb as for yard waste composting, such as balancing the carbon-to-nitrogen ratio, porosity and windrow size. With the exception of a few industrious crows, the facility attracted no wildlife. The crows left when all undecomposed food scraps were completely covered by wood chips. Physical contamination of the material with plastic bags, cans, bottles and other noncompostables is an ongoing problem, apparently directly correlated to shift changes and turnover in the management and staff of waste generators. The contamination level of the feedstock is estimated at less than 10 percent of the delivered food waste; manual removal and screening have proven to effectively eliminate contaminants. Because of the higher rates of contamination later in the project, the site operator recommends that on-site litter be collected at least once a month and that a snow fence be erected to stop plastic bags from being blown off-site. Water samples showed metals (nickel, cadmium, iron, lead, chromium, arsenic and selenium) that did not exceed background levels in the soil, and salmonella and fecal col-

48 Resource Recycling January 1995

Waste generation

for grocery stores and restaurants The earlier ENR-funded collection study conducted by CRC showed that weights for grocery store food waste and garbage could be calculated based on store floor area. Old corrugated containers, food and garbage ranged from 52 to 62 pounds per day per 1,000 square feet of floor space. Similar estimates for restaurants were not as easily made, because generation did not correlate well to seating capacity or to number of employees; these parameters did, however, provide a basis for estimating potential ranges for waste volumes. The ranges found in the study were 0.9 to 4.8 pounds of waste per customer seat per day and 4.6 to 7.8 pounds per employee per day.

iform were not detected. Soluble salts levels and the pH in the finished compost, at approximately 1.050 parts per million and 7.0, respectively. appear favorable for the end product to be suitable for horticultural uses

such as a soil amendment or mulch. Specific economic data are not yet available, but in comparing iJated costs associated with the outdoor, open-windrow method with in-vessel or hybrid systems, the numbers favor the low technology approach. And in terms of compost quality, after 90 days, the product was fairly mature and easily passed through a 1/2-inch screen, though the site operator believes that the food waste composting process could have been accelerated by turning the materials earlier and more frequently. Because this pilot project processes only small volumes of food waste, however, an accelerated schedule was not considered to be economically feasible. “Food waste cornposting could be an important part of Illinois communities’ efforts to reduce the amount of waste they dispose of,” believes Pat Bumpus, manager of the ENR Office of Recycling and Waste Reduction Resource Recovery Section. “Results from this pilot project will be useful in Illinois’ community solid waste planning activities.” Overall, mid-point results of this pilot project show positive signs of the viability of the diversion, collection and application of the outdoor, open-windrow cornposting technology to the estimated 1.1 million tons of food waste discarded in Illinois annually. RR