A catalyst is a substance which alters the rate of a chemical reaction but is not consumed in the reaction. In earlier days of chemical processing, catalysts used to promote commercial chemical processes were most often made of inordinately expensive Aprecious metals such as platinum or rhodium. Over the last decade or so, Abase metal catalysts such as manganese oxide and copper chromite have gained favor because of their lower cost and greater availability.
Oxidizers that incorporate catalysts have gained favor for air pollution control of volatile and hazardous organics because they reduce fuel requirements. In accelerating the oxidative reaction, the catalyst converts volatile organics to carbon dioxide and water at much lower temperatures than do thermal oxidizers. Catalytic incinerators offer a separate and perhaps increasingly important benefit in that their lower peak temperatures significantly reduce the amount of a secondary pollutant, nitrogen oxide, formed during combustion.
If, using the above disparate families of catalysts noted above, one extrapolates to determine the ultimate catalyst, it would be one that is ubiquitously available (or renewable) at minimal cost and functions at atmospheric temperature. 'Dirt' obviously meets the availability and cost criteria. Few, however, realize that soil (or readily available components thereof) meet the third criterion as well. Such earth components have been demonstrated to catalyze the oxidation of volatile organics at near-ambient temperature, far below temperatures common to conventional catalytic incinerators. Just as the (honeycomb) supporting structure was found critical in the design of conventional catalytic
oxidizers, structural support has long been known as an elusive key to obtaining long term performance from compost-based catalysts. This paper will describe the structural configuration and engineering performance of one manufacturer of modern bioreactors using this low temperature oxidation system.