Composting Systems

In contrast, composting processes utilize a mixture of solids and yard waste under controlled environmental conditions to produce a disinfected, humus-like product. Three common composting systems are a horizontal agitated reactor, a horizontal nonagitated reactor, and an aerated static pile system (nonproprietary). Compost can be marketed as a soil conditioner in competition with such products as peat, soil, and mulch. Although a large potential market exists, significant effort is required to penetrate this market. Yard waste revenue of 6.50/m (S5/yd ) and product revenue of 2.00/m ( 1.50/yd ) appear to be reasonable market values based on various studies reported on the Web. 

A good image for compost can be built up with assured quality and a quality label. Germany, Denmark, the Netherland, and Belgium have developed a composting system which is very important for the quality assurance. Elements of the quality assurance system are quality assurance of European composting and digestion plants (in ECN 2008) ... 

Several workers recommended a promising strategy by boosting the bioremediation of contaminated soil with cheap biomass products such as alfalfa, sawdust, chopped potato waste, apple pomace, cow and chicken manure, straw, or molasses in compost systems [215, 415-417]. These applications have led to transformations of TNT of more than 95% [414,415, 417] and were often accompanied by detoxification effects [414,418]. 

The composting system effectively remediates soils that are heavily contaminated and cannot be treated by in situ methods as well as wastes containing hazardous volatile constituents untreatable by land farming methods. 

Eikum, A. S., Berg, J. D., Selfors, H. Eggen, T. (1992). Simple composting system for biotreatment of PAH-contaminated soil. In Proceedings, International Symposium on Environmental Contamination in Central and Eastern Europe, Budapest, Hungary. October 12-16, 1992. 5 pp. 

J.L. Osmon C.C. Andrews, The Biodegradation of TNT in Enhanced Soil and Compost Systems , ARLCD-TR-77032, US Army ARRADCOM, Dover (1978) 33) R.E. 

Kane, E. B. and T. J. Mullins. Thermophilic Fungi in a Municipal Waste Compost System. Mycologia. 65 1087-1100. 

Mudhoo, A. and Mohee, R. 2006. Sensitivity analysis and parameter optimization of a heat loss model for a composting system. Journal of Environmental Informatics, 8 100-10. 

A polymer s compostability is a function of many factors such as pH, temperature, humidity, microorganisms population, and osmotic pressure. Simulated laboratory conditions as described by ASTM D6400 (//), D5338 (7) and ISO 14855 (6) may be an oversimplification of commercial composting systems which do not completely reflect the conditions in the commercial composting facilities. Therefore, further studies are necessary to assure that laboratory studies can duplicate commercial systems. 

DOD has been evaluating composting systems to treat explosives waste... 

The U.S. Army Environmental Center (USAEQ recently completed a demonstration of windrow composting of explosives-contaminated sods at Umatilla Depot Activity (UMDA) in Hermiston, Oregon. This demonstration represented the second phase of field studies conducted at UMDA, and was part of an ongoing effort to develop a composting system which can provide an economical and effective alternative to incineration for the treatment of explosives-contaminated soils and sediments. 

The U.S. Army conducted an economic evaluation of windrow composting versus the aerated static pile, and a mechanically agitated invessel composting system (MAIV). 

The results of this economic evaluation show that windrow composting treatment costs are less than aerated static pile or mechanical composting. The MAIV composting system is comparable on a cost-per-ton basis to incineration at 290/ton of soil treated compared to 300/ton for incineration. The greatest cost savings in comparison to incineration are seen by the windrow composting system at 187/ton. The aerated static pile system "treatment only" costs are estimated at 236/ton. All estimates... 

In addition to the cost savings demonstrated by windrow composting in comparison to other composting methods, there are other, less quantifiable, advantages associated with the use of a windrow system. For example, the windrow system has significantly less process control requirements, and so has less equipment subject to downtime that could lead to system performance variations. Also, the windrow system has demonstrated RDX (99.8% removal) and HMX (96.8% removal) reduction. The other composting systems have not shown this level of destruction. 

Aqueous-phase bioreactors provide good process control, can be configured in several treatment trains to treat a variety of wastes, and potentially can achieve very low contaminant concentrations. A drawback of bioreactor treatment is that, unlike composting systems which bind contaminants to humic material, bioreactors accumulate the products of biotransformation. In addition, bioreactors have been shown to remediate explosives only at laboratory scale, so the cost of full-scale bioreactor treatment is unknown. Full-scale bioreactors will have to incorporate a variety of safety features that will add to their total cost. 

Much contaminated debris is incompatible with flail-type windrow aeration equipment used for composting due to its large size. Physical size reduction is an effective option for preparing the debris for compatibility with the windrow equipment. Crushing is a standard method to reduce the particle size of rock materials. The size-reduced debris would be returned to the composting system to reduce the explosives concentrations to the remedial action objective levels. The crushing process will use mechanical size reduction equipment to crush the large debris. 

Preston, C.M., Ripmeester, J.A., Mathur, S.P. and Levesque, M. (1 985) Application of solution and solid-state multinuclear NMR to a peat-based composting system for fish and crab scrap. Canadian Journal of Spectroscopy 31, 53-59. 

Aerobic Bacteria - Microorganisms that require free oxygen, or air, to live, and that which contribute to the decomposition of organic material in soil or composting systems. 

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