Evahating compost qalityby George E. Johnsonand Steven L. Crawford1 nitial results of a compost quality study point to thebenefits of source separation.Minnesota leads the nation in solid wastecomposting, with over one-third of the oper-ating systems in the U.S. The operating his-tories and experience gained at these facili-ties are a valuable source of information forcommunities considering composting theirwastes. Minnesota’ composting facilities repre- ssent a variety of capacities,technologies,feed-stocks and political infrastructures. All eightMinnesota operations have some leve1 ofhousehold separation of recyclables and haz-ardous materials.Composting facilities in MinnesotaMinnesota’ solid waste composting systems scover a broad spectrum of technology andscale (see Table 1). The largest operation inthe state is the East Central facility in Mora,Minnesota. The facility serves fke COUntieSand processes 250 tons per day (TPD) ofmunicipal solid waste (MSW) using the shifts a day and uses the Buhler technology. The Prairieland composting facility isDaneco technology. The plant has been oper- This plant has been operating for a year and located in the City of Truman, Minnesota. Itating for two years, and has a tipping fee of has a tipping fee of $89 per ton. Both the East has a 100 TPD capacity and processes the$87 per ton. (The facility tipping fees cited Central and Wright County plants separate MSW from two counties. The technologyin this article should not be construed as an recyclables from mixed waste streams and used at this facility is the OTVD (Siloda) sys-accurate portrayal of total processing costs compost the residual organics. Nonprocess- tem, and the plant began operations about twodue to varying rates of public subsidy.) able wastes are sent to landfills. years ago. The tipping fee is $75 per ton. The second largest operation is the WrightCounty facility located in Buffalo, Minneso-ta, with a design capacity of ahnost 200 TPD George E. Johnson and Steven L. Crawford are environmental scientists with Malcolm Pimie, Inc. inof MSW. The operation incorporates two Minneapolis, Minnesota. Johnson is the administrator of the Compost Utilization Program.
In fact, progressive highway officials in has “emboldened” the opponents of rubber statessuch as Arizona, California, Florida and asphalt, says Gordon MacDougall, RPA’ s Kansas will push ahead with rubber asphalt executive director, as it “breathes new life use, while their trade group - AASHTO - into the political process.” RR does battle with Sen. Chafee and other leg- islative supporters of recycled product use. The 41-page joint federal report referred to in this This will be a tense confrontation - in late article (A Study of the Use of Recycled Paving October, AASHTO decided to seek a repeal Material) is available for $20.50 as Publication of Section 1038 of Ice Tea. No. PB93-219061 from the National Technical Thus, rubber asphalt use is heading for a Information Service, 5285 Port Roya1 Road, prolonged political match. The amendment Springfield, VA 22161.80 million scrap tires would be utilized annu-ally when the 20 percent use rate is reachedin 1997. RPA estimatesthat if rubber-asphaltwere used for 15 percent of al1paving in the SHRED-TECHU.S., al1the scrap tires generatedin this coun-try would be reclaimed. In fact, the Ice Tea program could leadtostrong competition for scrap tires in stateswhere large whole-tire incinerators operate,such as Connecticut, or in regions where sig-niticant volumes of tires are used in,solid-fuelboilers, such as the Upper Midwest and Pacif-ic Northwest.Growing oppositionThe opponents of mandated rubber-asphaltuse, led by the Ameritan Association of S,tateHighway Transportation Officials and theNational Asphalt Pavement Association, lob-bied heavy and hard to get the requirementrepealed. Rep. Bob Carr (D-MI) introduced anamendment in Section 330 of the $37 billionTransportation Appropriations Bi11 to pro-hibit the use of federal funds to implement,administer or enforce the rubber-asphaltpaving program. Rather, some monies wouldbe allocated for further study of the issues.Some 42 statessaid they agreedwith the Carramendment. The amendment passed theHouse 312-89 on September 23. The Senate then received the brunt of thepolitical furor. The political battle was fre-netic, with The Wall Street Journal editorsasking, “How do these sorts of strange ideastind their way into law?” The nation’ lead- sing business periodical labeled the Ice Tearequirement “an entitlement program” for the 15 members of RPA. On October 6 the Senate followed suit,adopting the Carr amendmentby a 90-9 vote.However, this limited amendment is certain-ly not the death knell of the rubber asphaltindustry, since it does not remove the provi-sions of Ice Tea’ requirements. Further, it sdoes not protect states from the penalties inthe law. Circle 178 on RR service card Resource Recycling December 1993 m
St. Cloud is served by Minnesota’ only s uct quality of MSW compostsproduced with-privately owned operation (Recomp). The in the state with the intent of minimizing thefacility has a current design capacity of 75 uncertainty regarding chemical and biologi-TPD (60 TPD of waste and 15 TPD of an ti A training program for facility opera- cal characteristicsof compost. Sampling andadjunct nitrogen source). This plant has the tors in sampling techniques will con- statistical analysis were necessarybecausenolongest operating history of any composting tribute to improve the consistency databaseyet exists with extensive analysis ofplant in the state or nation - over a decade and reliability of compost samples refuse-derivedcomposts produced in the U.S.- and the current tipping fee is $83.37 per over time and place. Many of the analytical data compiled andton. The St. Cloud operation also sendsfuel- available do not employ standardquality con-quality residuals to a nearby resource recov- (/ Source separation of noncompost- trol methods for consistent material samplingety facility in Elk River, Minnesota. ables by householders will improve and analysis. This lack of uniformity has Minnesota has four other plants with the quality of compost. made it difficult to compare analytical resultscapacities less than 100 TPD. The Penning- from the various compost facilities and tech-ton County facility located in Thief River Falls c/ Minnesota standards should be evalu- nologies.is currently processingapproximately 50 TPD ated (and perhaps revised) in terms of In early 1993, OWM awarded Stillwater,of MSW. The plant is unique, in that the oper- federal standards. Inc. (now associated with Malcolm Pimie,ation not only removes recyclables from Inc.) a $250,000 grant to evaluate the quali-rnixed waste and compoststhe residual organ- ty of compost produced at Minnesota’ facil- sics, but also produces a densified refuse- ities. The national Composting Council, Proc-derived fuel product, which is being burned utes of composts produced at Minnesota’ s ter & Gamble and Buhler (an MSW com-at a local medical facility. The tipping fee is facilities to answer fundamental questions posting technology vendor) offered additional$45 per ton. The Pennington plant has oper- about appropriate applications for compost technical and financia1 assistance to CUP.ated since 1985. material. The objectives of the two-year stndy were to: Minnesota’ three smallest operations are s Minnesota’ CUP concentratedon two pri- s n characterizethe compost produced at Min-in Lake of the Woods, Fillmore and Swift mary objectives. First, CUP was to provide nesota’ composting facilities scounties. These facilities were al1 custom- guided researchand demonstrateMSW com- n assist in developing market outlets for thedesigned. Al1 three operations focus primar- post use in various applications. This work compostily on composting source-separatedorganic is being canied out at the University of Min- W investigate real and perceived environ-materials. nesota, where the departments of Soil Sci- mental risks from compost use The facility in Lake of the Woods Coun- ence, Horticulture and Forestty are al1 con- H determine the benefits and cost of com-ty has a processing capacity of 10,TPD. ducting end-use studies. post productionAlthough the operationprefers to processonly Second,CUP was to characterizethe prod- H ultimately provide technical assistancesource-separated organic wastes,it continuesto receive mixed waste. Commingled andsource-separated recyclables are received ata separatefacility. The Lake of the Woodsplant opened in early 1989, and the fee struc-ture is $80 per household per year. The operationsin Fillrnore and Swift coun- When it comes to leaf collection,ties acceptonly source-separated organic feed-stccks and commingled recyclables. The Fill- ECOLOBAGS stand alone!more operation was originally designed toreceive mixed wastes, but has since amend- ECOLOBAGS provide the perfect solutioned its operations to process only cleaner to both private and municipal leaf collection.organic materials. Source-separated non- They comply with local legislation against the useprocessables received at these facilities are of plastic bags for leaf disposal, plus they can besent to landfills. The tipping fee at the Fill-more County facility, which opened in 1987, more economical than plastic bags. Tests showis $57.67 per ton. The Swift County facility that twice as many leaves can be stuffed into acharges$80 per ton and began its operations 30-gallon * * ECOLOBAG versus a 30-gallonthree years ago. plastic bag.* ECOLOBAGS are constructed of Many of these facilities are undergoing tough two-ply weather-resistant kraftsome degree of expansion or retrofit, and are utilizing a water-resistant adhesiveapplying for additional funding from the Min- throughout, so they can be left at curbside,nesotatOffice of Waste Management. Al1 of even in inclement weather!the operations have encountered some prob-lems, but continue to operate successfully. SELF-STANDING l WEATHER RESISTANT l BIODEGRADABLE l PUNCTURE RESISTANTCompost quality and use Call us today for a free sample at (800) 34&DAN0More than 100,000 tons of refuse-derivedcomposts are being produced annually byMinnesota’ facilities. Because of the diver- ssity of the processing scale, technologies,feedstocks and end-use product quality, Specializing in environmentally safe products for more than 20 years.OWM conceived the Compost UtilizationProgram. The focus of CUP was to examine l Brookhaven, New York study 1989. Copies availab~eupon request. l l approxima tethe physical-chemical and biological attrib- Circle 35 on RR service card Resource Rec.ycling December 1993 m
to composting facilities n Table 2 - Minnesota compost metals contaminant concentrations, May 1993 (1) based on these data. Monthly testing began Cadmium Copper Chromium Mercurv Nickel &J Zincin April 1993. The first ofseven quarterly reports was CWA 503 standards (2) 39 1,500 1,200 17 420 300 2,800submitted to OWM in Minnesota standards 10 500 1,000 5 100 500 1,000November 1993 for review.The database includes ap-proximately 40 different vari- East Central (five-county)(3) 12.1 677.0 210.4 1.2 66.5 393.7 1,820ables determined to be the Fillmore County (3,4) 1.4 73.2 26.8 3.4 6.9 60.7 260most significant indicators of Lake of the Woods County (3) 4.1 227.6 50.5 3.2 21.5 267.2 729compost quality. Some of Pennington County (3) 6.4 638.2 58.1 3.4 41.1 348.8 1,046thesepreliminary data estab- Prairieland (5) ll.9 951.2 105.7 6.8 71.7 379.0 1,918lished the need to modify St. Cloud (5) 13.7 385.4 72.9 6.9 64.7 298.8 831.3analytical techniques and to Swift County (3,4) 2.1 252.4 37.2 4.0 45.8 181.9 1,056researchadditional areas.The Wright County (5) 9.9 346.7 78.9 6.9 60.2 361.8 1,507.2initial report also includesconclusions and recommen- (1) Comparative metals levels, in parts per million. Shaded areas highlight concentrations that exceed Minnesota limitsdationsbasedon the data col- for unrestricted use.lected to date. (2) Standards in the federal Clean Water Act for high-quality sludge/sludge composts. Richard, et al. (3) Single composite (20 to 25 grab) sample taken in May 1993.CUP compost testing (4) Source-separatedorganics feedstock. (5) Average of 15 composite samples taken in May 1993.One-of the primary researchobjectives was to character-ize final product quality. Following the char- regulations for compost land application. rity, texture, pH, cation exchange capacityacterization,markets could be developed,and Issues of land application normally deal with (CEC), etc.risks to the environment could be examined. compost stabilization and contamination by Composts produced at Minnesota’ com- sCompost quality traditionally involves the metals,certain organic compounds (e.g.,poly- posting facilities were sampled by adminis-separateand distinct issues of environmental chlorinated biphenyls), and to a lesser extent, trators of CUP and the individual facility oper-safety and beneficial use. soluble salts and inerts (e.g., glass shards). ators. Becauseof some previously noted dis- Issues of safety are usually wit,hin the Issues of beneficial use are the market-driven parities in sampling results, CUP placed con-purview of state and federal environmental requirementsof nutrient value, compost matu- siderable emphasis on developing a stan- HIGH MOISTURECONTENTCOMPOSTSCREENING CAPABILITY IS NOW AVAILABLE IN A NEW ECONOMCAL COMPACT MULTISCREENTM. MateriaIsScreeningSystems SCREEN A W IDE VARIETY OF ORGANIC MATTER INTO VALUABLE END PRODUCTS. MULTISCREENTM increase your material production,cut costs and will will lengthen your screening season. Economically screens top soil, leaves, yard wastes, municipalyard wastes, sludge, organic wastes from 1 papermills,bioremediationwork, racetrackwastes, agricultura1 residues, i livestockand poultrymanures.Patentedoffset interna1 swinging hammers pulverize material as it passes through the trommel utilizing more screen surface area for single pass screeningoperations. n Externa1& powered interna1brushes clean screen to prevent -4.+&b clogging n Mobile air-cooled diesel or stationary electric power units n Patentedinterna1swinging hammers pulverize material n Optional - trommel diameters, lengths & screen sizes n Power tilt adjustable trommel for various operating load n Optional - rear discharge conveyors for fines and overs conditions n Extremely durable and made in America by a company n 2,4,6 or 8 cubic yard metering bin feeders to match with years of manufacturing excellence loader infeed For further information, literature and a quote contact your n Variable hydraulic speeds and reversing functions regional MUL TISCREEN TMdealer or call for a factory demo today. n 7 years of field tested proven technology with units in service TOLL-FREE 1 -800-243-5438 Manufactured by : MULTITEK @ PO Box 170 / 700 Main St / Prentice WI 54556-0170 / U.S.A. Phone (715) 428-2000 / Fax (715) 428-2700 Circle 30 on RR service cardm Resource Recycling December 1993
dardized sampling method- n Table 3 - Minnesota compost beneficial use parameters June 1993 ology. The method involves compositing 20 to 25 grab Compost auality assessment Resp (1) C:N(2) pI& S salts (3) TKN (4) plsl K.fa samples from various three- dimensional locations with- East Central (five-county) 0.48 20.3 7.3 15.8 1.26 3,576 4,28 1 in the cure pile. Fillmore County (SS) 1.30 17.1 7.9 8.2 1.61 1,727 5,233 A cross section of tbe data Lake of the Woods County 0.68 13.7 8.3 8.0 1.05 3,413 3,731 from the first samplings in Pennington County 0.21 13.1 7.7 19.5 0.84 2,842 5,424May and June at each of Prairieland (6) 0.62 24.8 8.1 16.2 0.98 2,733 5,741Minnesota’ composting fa- St. Cloud (6) s 0.21 27.0 8.2 16.8 1.09 2,496 5,936cilities is shown in Tables 2 Swift County (SS) 1.32 17.1 8.2 10.4 1.63 3,962 9,139 and 3. Wright County (6) 0.69 18.6 8.4 22.0 1.33 2,93 1 7,587 Table 2 presents safety SS= Sourceseparated.issues regulated by the state (1)Respirationcoeffícient. A measurement compoststabilizationas a function of the respiratoryactivity of the resi- ofof Minnesota Pollution Con- dentmicrobialpopulation.The measnrement in mgOYgm Volatile SoIids/hour.A coefficientof 2 mg02/gmVS/honr istrol Agency and includes normally characterizes raw feedstock.A coeffcient of 0.5 mg02/gm/VS/houris an indicatorof a stablizedmateri- aMinnesota’ uppermost lim- s al. Iannotti,et al.its allowable for a Class 1 12)Total carbonand total Kjeldahl nitrogen.compost (unrestricted use). 13)Solublesalts. Conductance a compostsluny. inShadedareasin Table 2 high- 14)Total Kjeldahl nitrogen.light concentrations that 15)Units in partspersamples phosphorum andpotassium(K).in the database, 16)Compositeof 15 million for (P) takenin May 1993. Because a gap of parameters respirationand phos- forexceed Minnesota limits for phomsweretakenfrom datacompiledin June 1993,ratherthanMay. Similar gapsin the St. Cloud andWright Coun-unrestricteduse. MPCA also ty datawere coveredin the samemanner.limits the concentration of Source: MinnesotaOffice of WasteManagement, CompostUtilization Program,1993.polychlorinated biphenyls(PCBs) to cl.0 ppm in a Class 1 compost. Table 3 presents issues of beneficial use. as an accurateand easily determined measureThe analytical results for the PCBs in com- Stabilization is shown as a function of micro- of compost maturity. The other parametersposts have not been included in Table 2 bial respiration. Unstable compostscan result describedin Table 3 are explained in the foot-becausethe results were inconclusive; how- in odor releasefrom the facility and, after land notes. These parameterscan serve to quanti-ever, in severa1cases, PCB levels exceeded application,seedand plant inhibition. Although fy the nutrient value and soil utility of the com-the state standard. These data will be sum- no test for stabilization is universally accept- post after land applicaiton.marized in a later report. ed, respirometry is rapidly gaining acceptance Fourteen indicators of compost quality are We Recycled 22 Mifk Jugs into.. , l Unique Cutter System l Produces Cleanest (Patent Pending) TDFAvailable The Compost No Hassle Ameri-Shred’ unique cutter design, unlike hook type cutters, s allows tires to be sheared instead of ripped. As a result, the shredded material has no protruding Gres, making it easier to 2829 152nd Ave. N. handle. These units also operate at approximately 112 the cost of Redmond, WA 9801 /, other brand tire shredders. Call us for your tire shredding needs. Eastern U. P.O. Box 205, Alpena, MI 49707 700 Riv%i ‘ %8:1 Phone: (517) 356-1593 acVKI#D-I Pittsburgh;‘ PA 152 Circle 168 on RR service card Circle 347 on RR service card Rosource Recycling December 1993m
included in Tables 2 and 3, from approxi- Testing conclusions tend to vary over time and within the pile duemately 40 variables witbin the database. The Minnesota’ mixed MSW composting facil- s to seasonal variations and the intrinsic het-the data presented here, however, are repre- ities show substantial differences in many erogeneity of the incoming feedstock.sentativeof tbe fust-quarter report submitted aspectsof product quality. Recommendationsto OWM for review. The report includes Generally, the four larger facilities had Compost quality is improved signiticantly bydetailed descriptions of individual facility higher contaminant concentrations tban did household and commercial separationof non-process flows, sampling and analytical the four smaller facilities. Differences exist compostableitems fmm the feedstock. Devel-methodologies, sampling and analysis data, between the sampling methods used by each opment of separation programs should beplus conclusions and recommendations. The operation. encouraged.conclusions and recommendations will be The contaminant concentrations of met- To ensure analogous data, facility opera-used to determine the costs and benefits of als and PCBs in compost appearto be an accu- tors need detailed training in the sampling ofcompost production, and to provide techni- rate measureof the effectivenessof tbe MSW product. An operatortraining program shouldcal assistance composting facilities in Min- to pre-treatment and source separation. be designed and implemented.nesota and elsewhere. Analytical data from individual facilities Chemical analysis for selenium should be included in the testing regimen to conform with recently promulgated federal Clean Water Act 503 requirements for land appli- cation of sewage sludge biosolids. Minnesota regulatory agencies should remove restrictions on the use of sludge biosolids in Class 1 composts. Clean sludge biosolids can serve as a valuable source of A COMPOSTER nitrogen and other nutrients to the process, without signilicantly increasing contarninant metals levels. TOO GOOD TO REFUSE Minnesota regulatory agencies should re- evaluate compost contaminant limits based on the federal CWA 503 standards. The State of Minnesota rules use the volatile solids reduction test for demonstrat- ing compost stabilization. The test requires tbat the composting processreduce the avail- able feedstock volatile solids by at least 60 percent. The test methodology does not include a standardmethod of determining the levels of volatile solids in the feedstock. A methodology or benchmark needs to be agreed upon and incorporated into the Min- nesota rules. RR Acknowledgement The authorswould like to thank Elena C. West- brook for her editorial comments. Referentes Iannotti,D.A. et al., “A QuantitativeRespiromet- ric Methodfor Monitoring CompostStability,” Compost Science and Utilization, 1(3):52-65. Johnson, G.E. et al., “SuccessfulCompostingon 100 Tons Per Day,” World Wastes, 36(8):62- Backyard composting programs will work - 67. in cities that offer the Biostacp Composter. Johnson,G.E. et al., “Facilities Evolve to Meet Challengeof Compost,”World Wastes, 36(6): The unique three-tierecl des@ of the Biostack@makes light of the 34-44. Nordhagen, R.D. et al., “Small-scaleMixed Solid hardest part of tbe composting job - tuming the pile. Because it makes Waste Materials Recovery and Composting: composting so easy, the Biostack@ ensures a successful municipal An Operator’ Perspective,”World Wastes, s composting program. And it’ fabricated of 60% recyclecl polyethylene. s (submittedfor publication). Richard,T. et al., “MSW Composts: Impactsof For more information, contact our Separation on Trace Metal Separation,”in Municipal Sales Dept. at (41.5) 383-4415 ext. 7661. Hoitink and Keener(eds.),Science and Engi- neering of Composting: Design, Environmen- tal, Microbiological and Utilization Aspects, 401-421,Renaissance Publications, Worthing- ton, OH. Circle 299 on RR service cardm Resource Recycling December1993