BioCycle October 2006, Vol. 47, No. 10, p. 45
Program initiated in 1990 includes 32 composting operations processing organics from 56 correctional facilities, diverting 14,000 tons of food residuals and waste wood.
James I. Marion
THE NEW York State Department of Correctional Services (NYS DOC) is the third largest state correctional system in the nation with 70 correctional facilities housing approximately 63,000 inmates supervised by 29,000 civilian and security staff. Correctional facilities range from 200 bed minimum security work camps and shock incarceration units to large 1930s era maximum security walled facilities such as Sing Sing and Attica with up to 3,300 inmates. The majority of inmates, 39,000, are housed in medium and minimum security dormitory style units with up to 1,500 beds.
Feeding systems range from traditional mess halls with cafeteria-style service to small group satellite feeding units. Nearly 6,000 inmates are fed three meals daily in their cells, medical units or 23 hour/day isolation cells.
With the passage of the New York State Solid Waste Management Act of 1988, all State divisions were required to initiate solid waste management and recycling policies to be in place by January 1991. The Department of Correctional Services responded by creating the Resource Management Division in 1990 to reduce the waste stream and provide avoided disposal costs to cover the cost of operations. Today the Department maintains recycling programs in all 70 facilities with 12 regional processing centers marketing over 20 recycled commodities in commercial load lots.
Early waste audits revealed the largest fraction of the waste stream by weight was food preparation waste and leftovers. Food waste generated weighed 1800 lbs/cubic yard with an average of 1 lb/day generated per inmate. This number is representative of audits conducted in 16 other states and compares with over 2 lbs/bed in hospitals and up to 3 lbs/bed in nursing homes. It was determined that less than .25 lbs/day was coming from returned serving plates with the balance coming from food prep areas, over-date bakery goods and wet materials such as pasta, rice, coffee grounds and soups.
In 1990, two pilot compost sites were developed to refine collection protocol and compost process control as well as determine economic feasibility for expanded operations. These early sites were open windrows on impervious pads utilizing large wood chips as a bulking agent and carbon source. (BioCycle has documented the history of the New York State Correctional composting program since its beginning; see “Correctional System Wins With Composting and Recycling,” September 1994; “Composting 12,000 Tons of Food Residuals A Year,” May 2000; and “Comparing Composting Technologies At Correctional Facilities,” March 2003.)
Based on results of the pilot sites, and from the perspectives of operational and avoided costs, the program has expanded to 32 compost facilities processing organic waste from 56 correctional facilities. During Fiscal Year 2005-06, approximately 9,000 tons of food residuals and 5,000 tons of waste wood were composted. Using $130/ton as an average waste disposal cost (tipping and hauling fees), the avoided cost is about $2.2 million. This number includes avoided disposal costs for composting of approximately 100 dairy cattle and calf mortalities and abattoir waste from 500 beef animals processed in the Department’s Agri-Business program. It is interesting to note that for the last three years, total tons diverted have decreased slightly to parallel a decrease of nearly 10,000 inmates in the last five years (due mostly to alternative sentencing and overall decreased arrests in the state).
Although a number of composting technologies are in place in the New York system, a set of standard separation, collection and process protocols have become implemented at all composting facilities. Food waste is collected in unlined, covered, plastic barrels (35 gallon) from pre and postconsumer areas of facilities. All paper and plastics are source separated following strictly enforced procedures. Collected food waste barrels are moved daily to compost facilities. At some facilities, they are stored in dedicated coolers for collection three times per week.
Inmates typically are served in Lexan sectioned trays using durable drinking vessels and metal cutlery. Inmates housed in remote areas or segregated cells are served in covered Lexan trays and portion controlled foil sealed polystyrene containers. In emergency situations and facility lock downs, inmates may be fed in their cells in Styrofoam containers with disposable cutlery.
No size reduction or grinding is utilized at any facility. At the windrow composting sites, mixing of food waste with bulking agent is accomplished either by skid steer or front loaders or in scaled agricultural feed mixers. Aerated bay and in-vessel sites all utilize Kuhn Knight reel-type mixers with scales. Bulking agent is exclusively tub ground scrap wood generated at correctional facilities from routine maintenance, pallets, clean construction debris, lawn and tree waste. All grinding and shredding is done by contract with mobile shredder operations due to capital costs, liability and high maintenance costs of grinders. In-vessel systems require double ground mulch material that is either purchased or double ground by contract vendors on-site. (Initial trials with the Wright Environmental Systems’ unit indicated a need for more absorptive surface area for the shorter residence time in the vessels to take up excess moisture and provide smaller airspaces for more uniform forced aeration.) At several sites, lawn and tree trimmings are accepted from local municipalities, as are utility generated chipped material. Starting recipes are generally 2:1 by volume bulking to food. Mixing ratios by weight are used at sites with mechanical mixers.
Composting temperatures are maintained at 55-70°C for approximately 30 days. Daily temperature readings determine turning and aeration activities. Initial moisture content is routinely 60 percent for windrows and 65 to 70 percent for mechanically aerated systems. Experience shows that visible food waste is gone in two to three weeks, with material ready for screening and curing in four to five weeks. Material is removed from active aeration and turning based on return to near-ambient temperature, moisture content and physical appearance.
Routine maturity testing is performed semiannually with complete physical and chemical analysis done only when a significant change in feedstock is experienced. Base recipes and time protocols were developed based on two years of quarterly analysis conducted for each technology.
All compost is screened through three-eighth-inch trommel or orbital screens. Overs are returned to the compost cycle after contaminants are hand removed. Fines are cured with minimal management for at least 90 days, with 120 days being the average.
Mature compost is utilized within the correctional system for landscaping, vocational horticulture programs, community service projects and, in some cases, land applied for turf maintenance or agricultural land amendment. Increasingly, finished compost is bartered to state and local transportation departments and municipalities for in-kind services. Limited bulk sales to private vendors are completed when surpluses develop at selected sites.
A number of considerations factor into site design and composting methodology selection, including available space, need for visual buffers, quantity of food waste generated, leachate treatment options and available labor. These factors are used to determine the level of technology utilized in developing compost facilities. Economic payback analysis also plays a major role in system implementation. Facilities are generally constructed that will provide an avoided disposal cost amortization in less than five years. The exception to this rule is when an in-vessel system is indicated where payback is less than 10 years.
Four levels of technology are employed at correctional sites. At present, there are 17 open windrow, six structure-covered windrow (i.e., in a pole barn with open sides), five aerated bay and four in-vessel systems. An additional three aerated bay facilities are funded or in development. The operating policy calls for implementing the lowest effective technology.
Leachate treatment is accomplished through capture of site runoff in surface drains and underground settling tanks that are pumped for landfill disposal as needed. The liquid fraction of runoff is diverted to stone-filled recharge structures and grass filter strips designed by USDA-NRCS.
Each level of technology offers advantages and challenges:
Open Windrow: A traditional open window system on an impervious pad (usually concrete) is the most economical system to construct and operate. These facilities are capable of handling large quantities of material with great flexibility for active processing, bulk storage and curing. Process control is limited by precipitation, temperature and other environmental influences. Mixing is less precise unless a mechanical mixer is used. Maintaining appropriate moisture has been problematic in some instances. Open windrows are used for very large sites with a variety of feedstocks such as manures, food and mortalities. This method is also used for very small operations, where capital costs for benefit derived are marginal. Leachate collection and treatment must be sized to accommodate rain and snow drainage from pad areas.
Open windrows are used for curing at most sites even with enclosed active composting areas. A 2002 study using prevailing civilian wages and current construction costs indicated open windrows operated with costs in the $6/ton range.
Covered Windrow: Windrow operations covered by pole structures with open or partial sidewalls are used where visual considerations are a factor. The structures also provide increased process control in high precipitation and severe winter sites. Containment of compost materials to the pad area is also improved with partial concrete sidewalls. Large pole structures also can provide protection from the elements for equipment such as mixers and screens. Pole structures are normally 60-feet wide by up to 200-feet long. Operational challenges with a covered windrow system include adequate ventilation for water vapor, building maintenance from equipment damage and interior odor issues. In the New York experience, based on 2002 information, costs per ton of material composted was in the $12 to $15/ton range.
Aerated Bay: Aerated static bay systems offer several process control advantages such as absolute temperature and moisture control with forced aeration. Aerated bay facilities are relatively labor efficient since regular turning of windrows is not required. They also are very space efficient in terms of materials processing. Because of the improved process control, thermophilic stages can be reduced to the minimum time frame. However, aerated bay systems require additional equipment in mixers, scales, screens and aeration fans, and controls with inherent maintenance costs. As with any enclosed composting space, ventilation is critical to the success of the program. Aerated bay systems also lose flexibility in recipes and variation in feedstock, although are not as restrictive as in-vessel systems. It has been our experience that most new composting facilities will use the aerated bay design because of cost efficiency, space, aesthetic parameters and process control. Aerated bay systems are in the $20 to $25/ton range when amortized over 10 years.
In-Vessel: While the most costly on a per ton processed basis, in-vessel composting systems still provide reasonable returns in specific locations. The New York State DOCS operates four Wright Environmental units of 750, 1500, 2000 and 3000 pounds/ day capacity. These units are employed where space is at a premium, such as inside facility security perimeters and adjacent to other inhabited buildings. In-vessel units provide ultimate process control and protection from the elements. Aeration, moisture, mixing and leachate and odor control are integrated in the vessel. With a 20-foot by 60-foot footprint, the 3,000 lb/day unit is very space efficient. Management considerations are increased for in-vessel systems. Integrated computers and electronics require extensive operator training and increased maintenance costs when mechanical failures occur. Enclosed space regulations may make routine maintenance difficult. In-vessel systems are recipe specific and require specialized bulking material with little flexibility in feedstock. With an enclosed tunnel design, adjustments to material in the 14-day cycle are difficult. In-vessel systems have been very successful in the New York State system. Over a 15 year amortization capital and operational costs average $45/ton.
All the composting technologies described above are capable of producing commercially acceptable compost products and significant waste disposal cost avoidance when compared to an average $130/ton hauling and landfill fee structure.
BIOBASED PRODUCT EXPERIENCE
Since 1995, the New York State DOCS has piloted three brands of biobased bags and food serviceware. All of these products were vegetable/starch-based with bag products including a polyethylene matrix. In each case, a number of economic and physical characteristics precluded the Department from regular use of the products. The NYS DOCS’ potential use of disposable/compostable serviceware is limited to emergency and security issue cell-based feeding situations.
The most evident limiting factor in each of the product lines tested was cost per service. The minimum cost was more than double the cost of alternative materials such as foam or paper materials.
In the case of compostable bag products to be used as food waste can liners, no product exhibited abrasion resistance suitable for institutional use. No product tested provided thermal tolerance above 100°F without failure. All but one product tested also lost integrity in the presence of high moisture materials when stored for more than a few minutes.
When introduced in windrow composting, biobased bags disintegrated into large fragments that posed a severe airborne problem across the landscape. When used in mixing equipment, bag sections became entangled in shafts and elevators causing system failures. Nondegraded bag fragments also coated the interior of screening equipment causing poor sizing of material. As with all tested biobased products, the per unit cost of biodegradable waste bags was approximately double that of traditional film bags.
Product testing for biobased serviceware included cups, bowls, plates and cutlery. All products tested were made from vegetable starch compounds. In each case of products submitted for field testing, both physical and economic limitations prohibited inclusion of these products in regular use for correctional facilities.
In all cases, cups, bowls and plates did not sustain physical shape or integrity when exposed to normal serving temperature of foods or liquids. When stored in unventilated areas, ambient heat of summer caused disfiguring and self-adherence. Forks and spoons did not maintain rigidity when introduced to hot liquids and became misshapen when stored in summer temperatures. Utensils used after being stored for over 60 days became brittle and broke into small pieces especially knives.
When biobased cutlery was introduced to the compost process, handle of the utensils showed an uncanny resistance to degradation and after several months became a contaminant of increasing proportions in recovered bulking agent. It was noted that a significant portion of biobased cutlery was still evident in compost after four cycles of active composting. The biobased materials were tested in all four compost systems in use. As with biobased film products, the cost of cutlery was at least double of durable and disposable plastic and metal alternatives.
Although initial experiences with biobased serviceware were unsatisfactory, the NYS DOCS system would continue to field test new products as the utility and environmental advantages of biobased products could fill a need in selected instances.
James Marion is Resource Management Director with the New York State Department of Corrections. This article is based on a paper presented at the Food And Biobased Cafeteriaware Composting For Federal Facilities In Washington, DC Roundtable Discussion held in Beltsville, Maryland, sponsored by the U.S. Department of Agriculture in December 2005.
October 25, 2006 | General
New York State Correctional Composting Update
BioCycle October 2006, Vol. 47, No. 10, p. 45