August 18, 2005 | General


BioCycle August 2005, Vol. 46, No. 8, p. 36
By combining upfront separation for recyclables with intensive composting of MSW and biosolids, Florida’s Sumter County and FORCE teach much about solid waste management.
Miriam Zimms

SINCE its launch in 2000, the Florida Organics Recycling Center for Excellence (FORCE) has become a formidable tool for organics outreach in the state – relating research and practices that directly impact Florida’s organics industry. Its Technical Advisory Group (TAG) brings in state businesses and diverse experts in biosolids, citrus, forestry, golf, horticulture, poultry and sod along with organics generators and processors. The Scientific Advisory Committee (SAC) members bring backgrounds in heavy metals, bioavailability, potential organic contaminants, microbial flora and the composting process itself. The group was assembled to establish parameters for the major issues and concerns with compost production and use – and to serve as consultants in specific areas.
Physically headquartered in Lake Panasoffkee at the Sumter County Solid Waste, Recycling and Composting Facility – one of the first in the nation to combine up-front recovery of recyclables with composting MSW and biosolids – keeps FORCE in the forefront of integrated, innovative solid waste management. A major component of the FORCE effort is made possible with the Sumter Facility’s 40-acre R&D farm.
Brought online last year for specific FORCE related activities is the in-vessel digester tube where various compost blends are formulated and tested. Complicated permitting requirements for the digester were successfully navigated, and careful attention to remaining strictly within regulatory guidelines has been challenging. The FORCE digester equipment has been operating without any significant extended downtime to date. In combination with SAC Protocol and the state’s Department of Environmental Protection (DEP) compost permit requirements, approximately 33 compost composite studies or tests will be performed for each of the 13 feedstock additive projects approved by DEP.
Manufactured and installed by A-C Equipment Services of Milwaukee, Wisconsin, and operated by Sumter County, the FORCE digester is used primarily for the purpose of running R&D feedstock additive projects while the Sumter County Solid Waste and Recycling facility goes through a retrofit. This digester is approximately 185 feet long and 14 feet in diameter. Digesters accelerate the conversion of organic wastes into compost. They work as an enclosed, rotary vessel that serves as a biomechanical preprocessing device to jump-start the natural decomposition process as air and moisture are added in the digester. The drive system continuously rotates the digester so that materials inside the unit are aerated and break down into smaller pieces. The digester is built on a slope to assist in movement of materials down the vessel.
The solid waste and recycling facility retrofit will include a MRF renovation and expansion and waste transfer area to account for the huge growth of the County’s population and increased waste generation. According to a recently released Census Bureau report, Sumter County ranked as the eighth fastest growing county in the nation. Overall, Florida gained more homes than any other state. According to the Bureau of Economic and Business Research at the University of Florida, the State’s population increased by more than 1.5 million people since 2000. Sumter County currently has ample “green pastures” for new home construction and retail stores.
The County facility has the capacity to produce compost utilizing this digester under its current permit conditions of a total 121 tons/day (69 tons of MSW, 34.5 tons of biosolids and 17.5 tons of fresh compost) with a three-day digester retention time. The compost from the tube then spends an additional 21 days in windrows on a finishing pad. The facility produces a Florida DEP classified Type A compost. The County will be seeking a compost permit change with the DEP to a two-day retention time in the digester tube.
Biosolids for the compost recipe are received monthly primarily from the city of Wildwood, and a small amount from the city of Bushnell, both located in Sumter County. The county’s new compost permit issued in 2004 limited the types of biosolids to be received by the facility to Class A, AA or B domestic wastewater residuals. A compost permit change will be sought to reverse this special condition.
Biosolids are delivered to a holding bay where they are dumped on a concrete pad and contained within concrete bumpers. Odor is currently mitigated in this area as well as on the MSW tipping floor. In addition, air that is released out of the infeed end of the digester is treated with an air scrubber to remove any volatile organics and particulates that may be present in the air. A biofilter, a combination of gravel, finished compost and wood chps, serves as an additional air filtration and odor control device for the exhausted air.
Additional studies include research on the in-vessel digester in the area of feedstock testing, procurement and compost product testing, including, but not limited to some of the following for 13 feedstock additive research projects: chicken and cow manures, chicken mortalities, bacterial additives, citrus sludge, MSW and biosolids.
Compost produced in 2004 went to a variety of university and other utilization projects. These incuded the local Master Gardener program, Boys and Girls Club, the Universities of Florida and Central Florida and private sector end users.
The county facility is designed to handle incoming MSW through a conveyor to a totally enclosed materials recovery area, where sorters pull out corrugated cardboard, newspaper, bottles, cans and plastics. Materials pass through a two-inch disk screen; unders from that screen go into the windrows and overs are transferred and disposed. About 20 percent of what goes through the sorting line is recovered for recycling.
Organic material remaining on the line is conveyed to the digester. Additional screening occurs after discharge from the digester. The material is composted in windrows for 21 days. Moisture and temperature are monitored and proper adjustments are made with a turning machine, or by adding water if needed. After the 21 days, material is screened again using a three-eighth inch screen. Residuals are either diposed or put back into the digester, depending on the composition.
After testing to determine the type of compost produced, material is moved to an outdoor storage pad and can then be marketed. The purpose of the facility is to produce a Type A compost with unlimited application. In total, about 65 percent of incoming MSW is estimated to be recovered via composting and recycling.
Research and Demonstration projects have been a major priority for FORCE since its founding. The following are examples of what has been accomplished:
Erosion & sediment control using organics – Working with the Organics Committee of Recycle Florida Today, FORCE completed a resource guide to promote beneficial utilization of processed organic residuals throughout Florida. The compilation included studies and articles that detailed applications for erosion and sediment control.
Comprehensive training, education and marketing of compost – This training outreach by Drs. Monica Ozores-Hampton and Nancy Roe involved the University of Florida/Institute for Food & Agricultural Services. Dodging the onslaught of hurricanes, a series of training workshops was held around the state that awarded continuing education units for citrus, vegetable, turf and ornamental growers as well as government staff. Presentations and tours covered topics such as compost biology, technologies, operational aspects to improve safety, quality and testing, regulations and varied uses. Approximately 300 private and public organics feedstock generators, processors users and regulators attended the events.
Compost value for forest crops – Directed by the University of Florida’s Don Rockwood, a multiple-year study using Sumter County MSW compost is underway to determine tree responses and define economic benefits. More than 1,500 eucalyptus species were planted in the 40-acre demonstration farm. In another study, the goals were to evaluate opportunities for growing cyprus and cottonwood with and without compost in the vegetable-producing sand lands of southwestern Florida. A third forestry study used county compost at the Withlacoochee State Forest Project. Drought effects – coupled with excessive flooding conditions during the hurricanes – were factors. Comparative analyses will be done on tree growth planted at affected and nonaffected sites. Preliminary findings showed: Cottonwood performs better with compost than fertilizer over first year growth; Cypress performs better with compost than fertilizer; and Eucalyptus Amplifolia performs better with fertilizer than compost over its first year growth.
Intensive production system for turfgrass utilizing compost instead of ground cover – Project goal at Todd Farms in Webster is to develop a viable cropping system for small-scale turf grass production that will conserve both water and land using Sumter County MSW compost over ground cover. Over 500 cubic yards of compost were used during this R&D project. A fertilizer and irrigation program was developed and monitored as well as a growth monitoring visual inspection process. Soil and tissue samples were performed to develop and modify the fertilizer program. During the pilot, the turf was monitored for weeds, pests and disease.
The FORCE project team spearheaded by Sumter County staff is hopeful that a Year 6 extension for the project will be granted. If approved by the state, additional R&D feedstock additive testing projects will occur in the in-vessel digester; staff will continue to seek strong university research partners; the website will continue to be expanded with more organics outreach and educational information; educational organics workshops and demonstration events will be explored; and partnerships in other funding agencies beyond solid waste will continue to be solicited to continue FORCE funding beyond Year 6. Most importantly, FORCE staff will seek to have the Center become legislatively created to maintain a long-term, organics-focused and funded center for Florida in an effort to centralize organics environmental testing, research and demonstration, education and outreach through one organization – FORCE.
Miriam Zimms is with Kessler Consulting, Inc. based in Tampa, Florida. She serves as the technical consultant for the project and can be reached at or 813-971-8333. The FORCE website can be visited at

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