Stanley Manahan's research is in the area of environmental/analytical chemistry with emphasis on the development of novel approaches to destruction of refractory hazardous wastes.

One major area of ongoing research involves the use of reverse-burn gasification for the destruction and immobilization of wastes. This process uses gasification as an alternative to incineration to destroy wastes, such as stable organochloride compounds, by a high temperature process that is quite different from incineration. Wastes are fed to a gasification reactor, often on a macroporous carbon matrix, and gasified in a stream of oxygen by the action of a flame front that moves in a direction counter to the flow of oxygen. The downstream end of the flame front is reducing, which makes the process very effective in removing bound halogen atoms and prevents the formation of undesirable byproducts that are often produced in incineration. The support matrix serves to retain heavy metals and may be subsequently greatly reduced in volume by combustion to produce a slag material that is ideal for the immobilization and disposal of heavy metal or radionuclide residues. Essentially no fly ash is produced. The product of waste gasification is a combustible gas from which water is condensed (removing most nongaseous contaminants) and which is filtered through a char filter, which is recycled back through the gasifier. The gas product is burned before it is released. This method of waste treatment is capable of achieving 99.9999 percent ("six nines") destruction of refractory organic compounds. It has been applied to the destruction of highly stable organochloride compounds, refractory organic compounds mixed with heavy metals, mixed wastes consisting of organic materials and radioactive substances, contaminated soils, scrap rubber, and a variety of sludges, including sewage sludge. It has also been applied to the reactivation of spent activated carbon. Research on reverse-burn gasification of wastes has been supported by the U. S. Department of Energy, U. S. Environmental Protection Agency, Dow Chemical Company, McDonnell Douglas, and Purgo.

A current area of research emphasis involves gasification of wastes in a bed of granular conducting material heated by an electrical discharge. Extremely high temperatures are attained with this "electrothermophotochemical process." Since no external oxidant or fuel is required, formation of byproducts is minimized. Because an electrical discharge produces the energy used and combustion is not required, a variety of additives, such as highly reducing hydrogen gas, may be added to the reaction medium for specialized waste destruction.

One of Prof. Manahan's particular interests is the preparation of course and reference materials in environmental chemistry and related areas of toxicological chemistry and environmental biochemistry. His book on environmental chemistry (Environmental Chemistry, 5th ed., Lewis Publishers/CRC Press, 1991) has been in print continuously since 1972. His courses in environmental chemistry and toxicological chemistry are taken by a variety of kinds of students in addition to those majoring in chemistry. These include students of engineering, agriculture, biochemistry, and nuclear science. A number of these students hold full-time positions, and Prof. Manahan is active in establishing industrial ties in the environmental area.