In-Vessel Food Residuals Composting for Brown Creek Correctional Institute, Polkton, NC

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Kristina Garrett
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1 i Final Report 1999 Organic Waste Recycling Grant In-Vessel Food Residuals Composting for Brown Creek Correctional Institute, Polkton, NC Company: RKB Enterprises, Inc., Norfolk, VA Bob Broom (757) Trial Dates: March 1, February 29, Description of project accomplishments. The GREENDRUM in-vessel system performed better than previous food waste trials predicted. During this trial, all food waste was composted, an average of 1615 lb. per day. The GREENDRUM system's price is less than $50,000 including delivery, and set-up. When waste disposal cost savings and the local bulk sale of compost are considered, the cpmbined annual cost savings for Brown Creek are approximately $30,000. The GREENDRUM in-vessel composting process ensures that the health and environmental requirements set forth by the NC Solid Waste Composting Rules are satisfied. The system proved simple to operate -- a reliable technology that could easily be transferred to other institutions in NC where similar cost savings are possible. Quality compost is available for use on Brown Creek's grounds and vegetable gardens. Surplus compost is available for other North Carolina State agencies or bulk sales. Accomplishments For the last 3 months of the trial, working at full capacity, all food waste generated at Brown Creek was composted with the average intake 1,615 lbs. each day. 12 lbs. of paper towels on average composted daily All requirements listed in the NC Solid Waste Composting Rules were met or exceeded. It is projected that composting food waste, using the GREENDRUM system, will save Brown Creek $10,395 annually in tipping fees as 297 tons of waste are diverted, while campactor haulage fees are reduced by $5, annually, based on current charges of $ per haul. A reduction in the frequency of waste compactor hauls to the landfill. The compactor was emptied 68 times a year before composting. This was reduced to 12 hauls last year; the key is eliminating food waste and the associated potential health, odor, and vector problems that dictate the compactor must be emptied at least weekly. During the trial, July 99 - Jan 00, solid waste disposal costs of $3,248 were avoided, 92.8 tons of waste were diverted. The GREENDRUM system is simple to operate and reliable; the technology could easily be transferred to other institutions in NC where similar cost savings are possible. Quality compost is available for use by Brown Creek on grounds and vegetable gardens, or for sale to local vendors. Approximately 3 cubic yards of compost, worth I

2 9 9 k about $48 is produced daily. Annual bulk sales could amount to $16,000, based on $16 per cu yd. Surplus compost is available for use by other state agencies. Great potential for good public relations for NC Department of Corrections and the State of North Carolina - environmentally responsible disposal through the use of a natural composting system with a reduction in costs. The accumulative effect of food waste composting including reduced frequency of compactor pickup, tipping fees that are avoided, and bulk sales of compost amount to $33,110. General Project Description The GREENDRUM in-vessel composter, supplied by RKB Enterprises, Inc. of Norfolk, VA, was selected to conduct a pilot composting project at Brown Creek Correctional Institute in Polkton, NC. Funding was provided, in part, through a grant from the North Carolina Division of Pollution Prevention and Environmental Assistance, Department of Environmental and Natural Resources. The GREENDRUM in-vessel process ensures that the health and environmental requirements set forth by the NC Solid Waste Composting Rules are more easily satisfied. This long-term trial of food residuals composting studied the GREENDRUM in-vessel process by rigidly applying those rules to see if the GREENDRUM performed to those standards. Potential problems with site location are solved through system design. All waste is isolated from the environment until after the time and temperature requirements to further reduce pathogens (Rule 1406 para. 12C) is accomplished. That rule requires, temperatures in the compost piles shall be maintained at a minimal temperature of 13 1 deg. F for at least 3 days. Analysis confirmed pathogen requirements were attained. After removal from the drum, compost is stacked for curing. The objective was to compost a waste stream made up entirely of food waste. This is a more complex process than adding food waste as a minor part of an existing yard waste, leaf, or other similar waste stream. The critical mix characteristics to achieve required thermophilic temperatures are all interrelated. These are ph, moisture content, porosity, and oxygen. C:N ratio is irrelevant to the process when the primary waste is institutional food waste because nitrogen is readily available and immediately released in food waste, while the carbon in wood chips and bark amendment takes longer to breakdown. Therefore the C:N ratio in a drum filled with food waste and a carbon amendment will always be effectively lower than lab analysis indicates. C:N ratio will, of course, affect the nutrient value of the end result -- compost. Locally available barkhawdust from sawmill, and poultry litter cake was added to reduce moisture and improve porosity. Hydrated lime was added to control ph. Required Capacity Brown Creek Correctional Institute houses on average 852 inmates, and employs 362 people. According to existing survey figures from the EPA document, Waste Assessment Reference Manual, Section 4, Conversion Charts and Figures, cafeteriastyle dining results in each meal producing one (1) pound of waste per person per meal. 2

3 I As Brown Creek food preparation operation is conscientious to minimize food waste, we anticipated receiving between 1,000 to 3,000 lbs. of food waste residuals daily. The prison also bags 12 lbs. of paper towels daily. Selection of GREENDRUM Type 6 16 The GREENDRUM in-vessel composter is a continuous feed system using an insulated drum. The drum is mounted on an all-steel frame and rests on all-steel rotor casters. It rotates every 20 minutes using a chain-drive unit powered by an electric motor. A type 5 12 GREENDRUM was initially selected in order to keep within the funding limitations of the grant. If the type 5 12 had been used, the maximum daily intake of food residuals would have been limited to 500 lbs. per day, plus amendment. This figure is based on trials conducted by Texas A&M University. Therefore, in order to run a pilot program with an operating capacity closer to the maximum needed at Brown Creek, the contract was amended to allow FKB Enterprises to provide a 6 16 GREENDRUM. The type 616, at nearly double the operating capacity, is rated by Texas A&M to handle 900 lbs. of food residuals daily, plus amendment.?he Daily Process The availability of labor at Brown Creek allowed Warden Rick Jackson to choose a manual mixing process over purchasing additional mixing equipment. Initially, a PATZ chopper was installed to chop the food prior to mixing. Use of the chopper was discontinued as it did not improve the consistency of the mix or improve the process. The PATZ chopper is designed as a hay bale chopper, not a food-waste chopper. It also proved to be noisy and allowed food to drop through the grid. However, a low cost mixer would be a timesaving addition to the system if a suitable unit at a reasonable price can be located. The Brown Creek staff devised a more effective method of mixing. A discarded 600-gallon cylindrical drum was recycled into a manual mixer. The staff cut it longitudinally in half and welded wheels at the corners making it an efficient mobile mixing chamber. Food waste is trucked about % mile from the prison kitchens to the site in 35-gallon plastic bins. Additional 35-gallon bins are used to measure the amendment to achieve an accurate mix by volume. Two inmates mix the amendments and food manually with pitchforks. The mixing chamber is then wheeled next to the input screw conveyor, and the mix is transferred to the screw-conveyor hopper feeding into the drum. At the other end of the drum, three sliding-door exit ports unload pre-cured compost, which completes the continuous process. Residence time is 4 to 5 days. The volume of material removed is equivalent to approximately 75% of the daily intake. Allowing for volume reduction during the process, this keeps the same mass of material in the drum. Compost drops onto a belt conveyor and then into a dump truck. Curing is accomplished static piles. 3

4 Daily Operation The original plan was to rotate the drum continuously. In doing so, however, we were not able to achieve the required temperature. As a result, an intermittent rotation routine was adopted; the drum was turned only during loading and unloading for about three hours each morning and for one hour every six hours on a timer. This frequency of turning incorporates sufficient oxygen into the mix to achieve accelerated composting while preventing the mix from dropping in temperature. Temperature averaged 140F. In prison kitchens less food is discarded for aesthetic reasons. This, along with full portion distribution of all meals, contributes to a high percentage of cooked material wasted -- much higher than other types of institutional food waste. Cooked food waste fermentation begins immediately when it is placed in a garbage bin. A dramatic drop in ph results, often causing ph readings of less than 3. Fermentation microbes eliminate aerobic microbes in these highly acidic conditions. The addition of hydrated lime during mixing with the amendment, prior to loading in the drum, limited the drop in ph to about 5.5, as would normally be expected during the initial stages of aerobic decomposition. It -is also possible that fermentation microbes, which are mostly single cell organisms, survive more easily than the more complex aerobic microbes and fungi, in a continuously rotating drum. This contributed to our decision to run the drum intermittently. Initially the weight of food waste composted was limited to 900 lbs. per day plus amendment, the maximum daily loading rate recommended by Texas A&M University. As problems resulting from low drum temperatures were resolved, the daily loading rate was increased to include all of the food waste from the kitchens, plus paper towels. The full amount of waste averaged lbs. of food and 12 lbs. of towels, which were mixed with amendment and loaded each day. Laboratory analysis by Prism Laboratories, Inc. showed no evidence of pathogens. A series of analysis conducted by NCDA Agronomic Division and A&L Laboratories, Inc. of Richmond, VA quantified the characteristics of the waste, amendment, and compost. 2. Assessment of adherence to contract Scope of Work A SW Composting permit for a pilot program was issued to Rick Jackson, warden of Brown Creek Correctional Institute, prior to the commencement of the trials. At all times this project has followed the guidelines set forth in the North Carolina Solid Waste Composting Rules while, at the same time, safely tested the GREENDRUM system in order to compile useful data as required by the scope of work. 3. Evaluation of success of the project Waste Diversion The project was a total success and exceeded expectations by almost doubling the predictions for daily diversion rates for the 616 GREENDRUM. The GREENDRUM invessel system will save Brown Creek $10,395 in tipping fees, as 297 tons of food residuals and other organic waste are diverted annually; and, $5, annually in reduced compactor haulage charges, based on current charges of $ per haul. 4

5 I Potential for Similar Projects Six versions of the GREENDRUM are in production, giving this composting unit a capacity range capable of handling a variety of daily food residuals and other organic waste, including biosolids, from any size institution. The project has demonstrated an economic, simple, efficient technology capable of use by similar institutions and other organic waste streams even in an urban environment. The unit reliably and quickly transforms organic waste into a useful soil amendment for use on the prison grounds. If labor is not as available at other institutions as Brown Creek, which has the advantage of using labor from a low security prison in the same location, a mixer will reduce manual labor needed to load the system each day. Model of GREENDRUM related to inmate population Based on 852 inmates producing on average 1615 lb. per day of food waste, the daily quantity per inmate is 1.9 lb. To apply this information, assume: > the availability of amendment at a reasonable moisture content > a mix ratio of 3 : 1, amendment to food P a 55% average moisture content of the mix The following table will help indicate the model GREENDRUM an institution will need, based on the number of inmates. I Maximum No. of Inmates I Weight of Food Waste 1 GREENDRUM model Expected - lb. per day 403 suitable for the waste Type Type Type Type Type ,920 Type 1050 Nutrient Value of the Compost When approved for use, Warden Rick Jackson, plans to test the compost by top dressing grass and using in the vegetable gardens and flower beds as a mulcwsoi1 amendment. He intends to further increase cost savings by substituting the use of this inhouse compost for the chemical -fertilizers that is currently purchased. Excess compost will also be offered to other state agencies and can be sold in bulk to local vendors. The latest waste analysis report from NCDA Agronomic Division is as follows: Nitrogen is high in relation to carbon, the C:N ratio was It is recommend the compost be blended with a high carbon source to achieve a C:N ratio of for ideal composting conditions. Soluble salt levels were high. Again, blending is recommended. 5

6 Compost ph is below ideal, Blending with high ph materials or agricultural lime is recommended. Additional analysis is planned to confirm the consistency of this analysis. 4. Description of unanticipated events in conducting the project A design change intended to reduce the time spent loading the drum by fitting a U- trough screw conveyor compounded difficulties in producing the ideal mix. A new U- trough conveyor allowed for a reduction in the size of the access port, increasing the usable capacity of the system. This helped achieve two objectives; faster loading and greater capacity. Excellent! However, the new U-trough conveyor caused a reduction in air entering the drum, which was a more significant factor than anticipated. This caused an oxygen deficiency inside the drum, which, in effect, caused the microbes to be smothered. In hindsight this should have been detected sooner. When a smaller Type 408 manually loaded GREENDRUM was used to test the mix, the extent of the oxygen deficiency became clear. The simple solution took months of trials to uncover because there were multiple solution options. Initially, the basics of composting were addressed: a. Moisture content b. C:Nratio Note: 1. Reasonable values of these two characteristics were quickly established. Since the desired temperatures were not achieved immediately, time was lost attempting to produce higher temperatures by varying the moisture content 2. The analyzed C:N ratio for the mix, at approx. 35: 1, was reasonable but not likely to promote a highly active composting process. We believe our effective C:N ratio was lower as the nitrogen in the food waste was much more available than the carbon in our amendment. Having exhausted combinations of the above, we concentrated on the following: c. ph d. ammonia e. oxygen Daily variations in food waste complicated the problem. The key to solving the mix equation at Brown Creek was use of the portable 408 GREENDRUM. Unworkable mixes were quickly eliminated as small batches were used to refine the mix for maximum composting efficiency. The portable unit allows each site s waste to be tested quickly, with the available amendment, to ensure that a full-scale system will operate efficiently. Fifteen pounds of hydrated lime was added for each cubic yard of mix to raise the low ph caused by fermentation. Although visually the litter had the properties of a perfect amendment, excessive amounts of ammonia stifled the process. Therefore, a blend of litter and wood bark was used as the amendment, which provided the fastest increase in temperature. To improve air supply to the drum, a small blower was used temporarily. The permanent remedy replaced this; a ventilation port was added at the unloading end, which caused air to be drawn through the drum by the chimney effect. 6

7 I The final mix was adjusted to the following: By Volume: 1 part food waste 1.5 parts poultry litter (used to reduce the moisture content) 1.5 parts (green) wood bark (for porosity) 5. Description of what would be done differently if the project could be done over again The 616 GREENDRUM design changed between the proposal and the beginning of the trial to include a heavy-duty frame mount. The unit is now considered too heavy to be supported on a trailer. Site preparation is now easier when the weight is distributed through the frame over the length of the drum. The absence of the trailer also allows the drum to be lower on the pad, thus making it easier to load. Future GREENDRUM installations of type 6 16 or larger should be ordered without the trailer. Productivity, working conditions, and the efficiency of the laborhystem combination were examined. For each site, actual situations should be observed. For example, when the time to mix a batch is measured, the circumstances and the labor resources should be taken into consideration. The Brown Creek project was planned as a morning activity allowing adequate time to complete each mix in 30 minutes. Several things here could alter productivity. These include a covered, paved working area and paid non-inmate labor. Notwithstanding their circumstances, the inmate workers had an excellent attitude, were interested and took some pride in this project. The PATZ chopper added time to the process without providing tangible improvement in efficiency. The consistency of food waste delivered to the site meant it was not necessary to employ a chopper to prepare prison food waste for composting; an aesthetically pleasing product is produced without the use of a chopper. A smaller inexpensive mixer would be beneficial, as it would likely reduce total handling time by half. BW Organics has designed a choppedmixer that, if proven reliable in tests, will be sold in the $6,000 - $7,000 range. No such unit is currently available on the market. 6. Description of waste reduction impact of the grant. Include an exact projection of how many tons of permanent annual diversion of material from disposal will result from the grant project. The following table shows the actual daily loading rates and the total tons of food waste diverted. During the first four months, the daily the loading rate was limited to the expected maximum daily capacity of the GREENDRUM 616. The drum was not loaded on a regular routine as various trials were conducted. During the second half of the trial, all available food waste was loaded: 7

8 Month Daily Loading Rate, lb./day July 896 August 955 September 954 October 973 November 1633 December 1727 January (thru 24") 1486 TOTAL Monthly Total, Tons Using figures for the months when the GREENDRUM was working at full capacity, the average daily loading rate was lb., giving a projected annual diversion of 295 tons of food waste, plus 2 tons of paper napkins for a total of 297 tons annually. Also, food waste composting reduced the frequency of waste compactor hauls to the landfill. The compactor was emptied 68 annually before composting and was reduced to 12 hauls last year; the key is eliminating food waste and the associated potential health, odor, and vector problems that dictate the compactor must be emptied at least weekly. It is projected that composting food waste, using the GREENDRUM system, will save Brown Creek $10,395 each year in tipping fees, and $5, annually in reduced compactor haulage charges, based on current charges of $ per haul. Brown Creek will produce approximately 1,000 cubic yards of compost annually. In Charlotte, 50 miles to the west, this has a bulk market value of $17.75 to $23 per yd. Brown Creek's annual bulk sales could amount to $16,000, based on $16 per cu yd. Considering tipping fees, haulage charges, and compost sales, annual positive revenues are $32,110. Not including amortization of the capital cost, operating costs projected over one year including lime, labor, electrical power, and amendment are $2, The positive balance is $29,435 Incentive - Better Prison Recycling Programs will Reduce State Waste Costs Revenues from the sale of recycled and composted wastes currently go to the state. This eliminates any local benefit fiom funds generated by these programs. If, instead, prisons had the motivation of generating funds from these sales for their local budget, the efficiency of recycling and composting programs would improve. Although the state would not directly receive funds fiom sales, the waste disposal cost savings from additional prisons running efficient recycling and composting programs would more than compensate. Currently, there is a Governor's directive but no incentive to achieve it. 8

9 7. Description of any material developed as a result of the project. Food Preparation The quantity of food wasted each day prompted Warden Rick Jackson and the Food Service Department to conduct an investigation. Two primary factors were uncovered. On fairly frequent occasions, more food is prepared than required. No procedure is in place to feed this excess food to inmates. If not composted, the waste food becomes a disposal cost. Also, because of security concerns, there is no method for inmates to communicate with the servers, who fill the food trays in the kitchen. Therefore, each tray is filled with an entire meal and then slid under the hatch. Brown Creek Enterprise Division is building a security screen through which the inmates will be able to request items be omitted from their tray, thus reducing wastage. Rick Jackson expects that individual portion-control will reduce waste and will allow staff to further review the quantity of food prepared for meals. Composting Process The capacity and composting efficiency of the GREENDRUM, as originally designed and manufactured by BW Organics of Sulphur Springs, TX, was improved by making modifications and improvements before delivery and during the project. A simple, but effective, mixing chamber was developed from waste materials. 9

10 ,'- Final fiscal report Cost of items purchased for or during the trial: Hand Tools: $ Hydrated Lime: $ per month, total for the trial $ Agricultural Lime: $23.33 Poultry Litter (amendment): No charge. 20 mile round trip approx. 1.5 hours Bark Mulch (amendment): $37.07 per month, total for the trial $ Electrical Power: $20.47 average cost per month. Total for the trial $ Inmate: Correctional Officer: $1.40 per day $.70 per day) Periodic supervision during 5 hours of work Hauled 14 loads of poultry 1.5 hrs per trip State funds: Lease of type 6 16 GREENDRUM Local cash match: Purchase of Patz 9427 Local in-kind match: Delivery & Equipment set-up REVENUES: $2 1,381.OO $ 3, $ 1, EXPENDITURES : $21, $ 3, $ 1, Initial Training $ Quarterly inspections $ 2, Sub Total: $28, $ $ 2, $28, Funds from other sources: Amendment and Misc. Items $ Inmate Labor $ Sub Total: $ 1, Total project revenue: $29, $ $ $ 1, Total Project Costs $29,

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