Type: Master Composter
Name: UNC Charlotte
Address: 9201 University City Blvd
City: Charlotte, NC
Launch: June, July and August of 2000.
Location: UNC Charlotte, Cafeteria Activities Building, Room 113, 9201 University City Boulevard
Project: Food Waste Composting
Funding: North Carolina Department of Environment and Natural Resources Division of Pollution Prevention and Environmental Assistance.
Helpers: Facilities Management

 

TWO EARTH TUBS WITH A BIOFILTER IN BETWEEN. FANS ARE IN THE TWO WHITE BOXES; AUGERS ARE WIRED OVERHEAD.

 

Overview: Food Waste Composting The Waste Reduction and Recycling program includes a food-waste composting project. This pilot project is funded through a grant awarded by the North Carolina Department of Environment and Natural Resources Division of Pollution Prevention and Environmental Assistance.

 

The grant was awarded in December 1999. Site preparation took place in June, July and August of 2000. The electrical breaker box was installed, two level concrete pads were prepared for the two Earth Tubs, the sanitary sewer drain was established, a connection to the city water system was installed, and the ramp at the cafeteria loading dock was built to enable transference of the food waste.

 

In July, a Solid Waste Pilot Composting Permit from the NCDENR Division of Waste Management, Solid Waste Section was acquired. The pilot permit is valid through July 15, 2002. In late July 2000, the Earth Tubs were delivered from Green Mountain Technologies. The Facilities Management staff began work on all the appropriate electrical and plumbing connections to the tubs.

 

The Recycling staff provided training and educational materials to the Sodexho-Marriott cafeteria staff regarding separation and storing of food waste. The Recycling Office provided the buckets and the cart for the waste storage and transportation.

 

The Recycling Office obtained a wood-mulch bulking agent from Blythe Equipment Company through a contact at Mecklenburg Compost Central. We loaded the wood mulch into Earth Tub #1 on August 21, 2000. The Cross Road's Café began serving meals on August 22. The Recycling Office began composting the food waste that day.

 

As of the end of the last fiscal year (June 30, 2002), 61,360 pounds of food waste and 5368 pounds of sawdust have been composted since the project began.

 

For more detailed information on our composting program, please contact Lee Arnold at flarnold@email.uncc.edu

 

Description: Food Waste Composting Final Report

 

2000 Organic Wastes Recycling Grant Report University of North Carolina at Charlotte Grant sponsored by North Carolina Department of Environment and Natural Resources Division of Pollution Prevention and Environmental Assistance

 

December 20, 2000

 

Description of Project Accomplishments:

 

The site was prepared and the Earth Tubs were up and running on the first day of the fall semester, August 22, 2000. This was our goal start date; therefore, we met our initial goal. To date we have diverted over 14,948 pounds of food waste. It has only been four months since the food waste diversion pilot project began; therefore there is no final product (compost) at the time of this report.

 

 

 

Implementation: Adherence to Scope of work:

 

After a lengthy design phase in Facilities Management, site preparation took place in June, July and August of 2000. The electrical breaker box was installed. Two level concrete pads were prepared for the two Earth Tubs. The sanitary sewer drain was established. A connection to city water system was installed at the site. The ramp at the cafeteria loading dock was built to enable transference of the food waste.

 

In July, a Solid Waste Pilot Composting Permit from the NCDENR Division of Waste Management, Solid Waste Section was acquired. The pilot permit is valid through July 15, 2001.

 

In late July, the Earth Tubs were delivered. Facilities Management staff began work on all the appropriate electrical and plumbing connections to the tubs.

 

The Recycling staff provided training and educational materials to the Sodexho-Marriott cafeteria staff regarding separation and storing of food waste. The Recycling Office provided the buckets and the cart for the waste storage and transportation.

 

The Recycling Office obtained a wood-mulch bulking agent from Blythe Equipment Company through a contact at Mecklenburg Compost Central. We loaded the wood mulch into Earth Tub #1 on August 21, 2000. The Cross Road's Café began serving meals on August 22. The Recycling Office began composting the food waste that day.

 

The first batch did not turn out so well. It was very wet and although it dis not go completely anaerobic, it did come close. The temperature attainment was not as high as we had hoped and we were unable to attain 130° for three consecutive days. We added urea in an attempt to bring the temperature up; we attained several days in the 120° range. the difficulties we had with this batch may be attributed to five main factors:

 

 

 

The bulking agent we used had soil and 'fines' mixed in with it, thereby depriving the batch of air space.

 

The food waste had a great deal of grease and oil in it contributing further to the density of the batch.

 

Too much food waste was added to the mix before adding more carbon.

 

When we emptied the Earth Tub, we discovered the floor had warped allowing small particles to go under the screen protecting the reservoirs in the bottom of the tub. This prevented leachate from draining appropriately from the tub and restricting airflow.

 

The tub was slightly lower than the bio-filter; therefore leachate stayed in the pipes leading to the filter and had more difficulty draining.

 

To remedy these difficulties:

 

We re-trained the cafeteria staff and restricted the input of oils to the mixture.

 

We began sifting the bulking agent.

 

When the tub was emptied, we jacked it up on bricks to make it higher than the bio-filter.

 

We attached metal plates to the floor grating of Earth Tub #1 to minimize contamination of the reservoirs.

 

We placed the contents of Batch #1 in the fenced in area of the Facilities Management compound and covered it with soil. The temperature of this pile shot up to 120 - 129° and stayed there for several days. It became obvious that the mixture had lacked oxygen. We are still monitoring this pile. It will take a long time to cure as it was in pre-compost state when removed from the tub.

 

While Batch #1 in Tub #1 was aging we started Batch #2 in Earth Tub #2 on September 14,2000. Since we had started this batch before emptying Tub #1, we were not yet aware of the warping issue. We did sift the bulking agent before adding food waste to avoid the fines .Our experience with Batch #2 was similar to Batch #1. After two batches we discovered that the tubs were filling much quicker than had been calculated. The two main reasons for this are; the unanticipated 35% increase in the number of meals served at the Crossroad s Café and the subsequent increase of bulking agents and carbon feedstock required to balance the increase in food scraps. After aging the tub as long as possible we emptied it and discovered the floor in Tub #2 warped and the bottom of the batch did go anaerobic. This caused us to get many complaints about odor. Batch #2 was taken to the compound, covered with soil and mulch. Temperatures went up on this pile as soon as it was exposed to oxygen.

 

Batch #3 in Tub #1 was started on October 5. By this time, we had restricted grease and oil, we had a new bulking agent that did not have 'fines', we had corrected the warped bottom, we had elevated Tub #1 to be above the bio-filter and we became much better at keeping the nitrogen to carbon ratios balanced at 30:1. This tub was a success. It attained a temperature of 130 or above and held it for three consecutive days. We actually had to add water during the aging process. When we emptied this tub, we had a material that could easily become cured compost. We placed this batch at the compound and covered it with mulch only. A soil cover was not required to keep the flies off the batch.

 

Batch #4 in Tub #2 was started on October 18, 2000. We were as careful with Batch 4 as we were with Batch #3, yet we have not attained the 130° temperatures we had in Batch #3. The metal plate that we had placed in Tub #2 has come loose and may be the cause of our current difficulty. We also had tried some crushed leaves as a carbon source and they did not break up very well. We removed part of Batch #4 in order to give Batch #5 a few more days to cure, hoping to get to the Thanksgiving break without empting Batch #5 or the remaining Batch #4.

 

The portion removed from Batch #4 looked good and was mostly decomposed materials and leaves; our bulking agent had decomposed quite a bit. The #4 partial pile is at the compound aging. We continued to fill Tub #2 with food waste and bulking agent creating Batch 4.5. Temperatures went up slightly and held through the Thanksgiving break. Then they dropped drastically. We continued adding food waste, bulking agents and carbon feedstocks. The temperature remained low. On December 18, 2000 we added urea and this batch will age in tub until after the winter break.

 

Batch #5 in Tub #1 was started on November 7, 2000. The metal plates on the floor continued to stay in place. We followed our prescribed formula for food wastes, carbon feedstock and bulking agents. The batch seemed to be coming along fine, however the temperatures were not as high as they should have been. It was at this time we tried a new thermometer. The old thermometer was 15° to 20° cooler than the new thermometer. We verified the readings of the new thermometer to a third thermometer and found the new one was correct. We do not know when the first thermometer became inaccurate. We suspect that it had been somewhat inaccurate since Batch #4. It had apparently had a brief encounter with the auger during that batch. The tub was well drained and aerated. We actually added water to this batch. This batch maintained temperatures over 130° for several days. This tub was emptied on December 4, 2000. Batch #5 was a good quality batch and is currently curing at the compound. The output weights of the successful batches indicate a 50% reduction in weight of the composted food waste. The majority of the weight reduction is attributed to moister loss. In the less successful batches the output weights were very close to the input weights. They were extremely moist and compacted. The successful batches had an earthy odor. The less successful batches had a stagnant odor.

 

Batch #6 in Tub #2 was started on December 4, 2000. The metal plates were replaced on Tub #2 while it was empty. The same formula is being used on this batch. After a slow start, the tub held high temperatures. Water was added to Batch #6. The cafeteria discontinued serving food for the semester on December 13, 2000 and will reopen next semester. The contents of this tub will age during the winter break.

 

Recommendations: Evaluation of success of project

 

The project is just underway. The pilot permit is valid through July 15, 2001. Therefore, we plan to continue the project through that date before determining the success of the project. We believe it has been successful in several ways: having the project on campus has given many people a new insight into waste in general. During our four months of operation, we have had an opportunity to work on the other component of the grant - education. During the Annual National Recycling Congress, held in Charlotte we hosted a tour of the campus composting efforts for one hundred and forty-four participants. The tour participants were very interested in the Earth Tubs and we have had several subsequent conversations and have sent information out to several people. Staff from the North Carolina Division of Prisons Albermarle Correctional Institution visited our campus to look at our composting operation. We provided them with information on the Earth Tubs and NCDENR/DPPEA information. At the October Meeting of the NCDENR Environmental Educators we invited members to visit our operation.

 

Description of unanticipated events in conducting the project:

 

To summarize, we have had several start-up problems. Keeping a good carbon to nitrogen ratio in a continuous feed system is a challenge. Since, we are not sure, at what rate (or volume) our nitrogen is dissipating we are not quite sure of our ratio from day to day. We keep very accurate records of what we are feeding the tubs and hope to repeat our successes. Without the ability to chip our own wood waste, we have spent a lot of time locating and hauling carbon sources. We purchased a four-inch chipper on December 19, 2000 with our remaining matching funds. The chipper will help to provide carbon and bulking agent.

 

The Earth Tubs we received had some problems. The cleavis pins holding the auger in place broke on a regular basis. We have replaced twelve pins so far. The wheels on the lid jumped off the track because there were no washers attached to the U-bolt mechanism. All the bolts holding the push-handles in place loosened and four of the handles came off. The most significant issue has been the warped floor of the tubs; once we had 3,000 lbs. of food and bulking agent in the tub there was nothing we could do until it was time to empty the tubs. These issues took a lot of time to resolve and interfered with the decomposition rate when airflow and drainage were restricted. The difficulty of not maintaining high temperatures in some of the batches causes us more concern about pathogens than we had hoped to have this point. None of the batches have attained a cured compost level; therefore, we have not begun the finished-compost testing phase of the pilot. The second drawback of not having a high rate of thermophilic bacterial activity is that the food waste has not been decomposing at the rate we had anticipated. Therefore, we are emptying the tubs before we had scheduled just to keep up with the daily food waste. When our tubs are hot, the food simply disappears and when they are not, it becomes problematic.

 

One way to increase temperature in the Earth Tub is to turn off the fan. When we do this it cuts down on the oxygen flow and odor control. We operate the tubs with the fans on and the valve almost closed most of the time. We open the valves fully once a day to allow the leachate to fully drain. The other thing we could do is to load it up with urea. We have been reluctant to do this, however we have added five to eight pounds to two of our batches and forty pounds to Batch 4.5. When the highest temperatures were achieved it was without the use of urea, therefore we continue to replicate those factors. We may resort to using lots of hen the highest temperatures were achieved it was without the use of urea, therefore we continue to replicate those factors. We may resort to using lots of urea as other sites have done. If we were to limit the food waste to 150 pounds a day we believe we could make the tubs last long enough to get a good aging in the tubs before removal to the curing site.

 

The number of hours it takes to find carbon sources, repair the Earth Tubs, unload the Earth Tubs and clean out the tubs for repairs has been much greater than expected. We assume some of this can be attributed to 'start-up' problems and hope that in the next several months we will improve our processes. By the end of our pilot year we will be able to make an accurate evaluation of the daily resources required for operating the Earth Tubs at this site.

 

Additional: Description of what we would do differently:

 

We would do more upfront networking with Earth Tub operators at sites with similar food waste volume, in order to obtain a more realistic view of the food waste processing cycle of the tubs. This would help us in determining the volume that could be processed daily at our site. We have learned a great deal about bulking agents and usable carbons, based on that knowledge we know the capacity of the Earth Tubs and realize that two tubs are not adequate for our pilot facility. The tubs require large volumes of bulking agent to maintain porosity in the mixture and so much carbon in to maintain our carbon to nitrogen ratio that the weight of the contents exceeded the tub capacity within ten days of use. In figuring capacity, we did not count on so much weight for bulking agent and daily carbon feedstock. The large quantities of bulking agent and feedstock required by the process need to be obtained more from on-campus sources than outside sources. Our chipper will go into operation in January 2001 and we will be able to use campus wood waste for some of our bulking agent. It would have been much better to obtain the chipper earlier in the process. We were unable to calculate the remaining available matching funds until all Facilities Management design work and estimates for our site and roof was completed.

 

What we would not do differently:

 

The project would not have been possible without the support of UNC Charlotte s administration. Cooperation and support from Sodexho-Marriott Dining Services could not have been better. Cooperation from the Facilities Management operations shops has been excellent. The Recycling Labor Crew Leader and the Recycling Office s student workers have been fantastic. They keep the operation going every day: rain, sleet or snow.

 

Description of Waste reduction impact of the grant:

 

Waste Diversion
August 22 to December 19, 2000
Four months of operation
Annual Projection for 10 months
Operations of Cross Road s Café

 

14,948 pounds of food waste
780 pounds of food waste (sawdust)
948 pounds of paper waste
16,676 Total
37,370 pounds of food waste
5,400** (sawdust and garden debris)
2,370 pounds of paper waste
45,140 Total

 

8.338 tons at $38 per ton = $316.84
2.5 tons at $38 per ton =$855.00

 

**The chipper obtained is capable of processing wood up to four-inches in diameter, therefore the amount of wood waste mentioned in the grant application will not be diverted. The eight-inch chipper requested was understandably not funded through the NCDENR/DPPEA 2000 Organic Wastes Recycling Grant.

 

Materials developed as a result of the project:

 

The University Times, student newspaper, did an article on the Earth Tubs that had a positive impact. We received recognition as being an innovative and research minded organization, putting Waste Reduction and Recycling in a positive light on campus and in the community. We were asked to contribute an article about our program to the Blue & Green Currents, an environmental publication for the greater Charlotte region. As a result of our experience with food waste composting, we were asked to teach a portion of the 'Compost Facility Operator Training Program Short Course'. The two-day course was sponsored by South Carolina Department of Health and Environmental Control and took place at Winthrop University, Rock Hill, SC.