145 (0.3-0.5%). • Low pressure drops across the bed, reducing energy requirements and operating costs. • Improved techno-economics and net carbon avoided. Figure 8. Site trial results of CataVAM with 0.19 vol% VAM at various ventilation air flow rates. 3. EMERGING VAM ABATEMENT TECHNOLOGIES Photocatalytic Oxidation An emerging technology of photocatalytic oxidation of fugitive methane has been studied to destroy ventilation air flows containing very low concentration methane (e.g. less than 0.3% and even at ppm levels). The photocatalytic oxidation uses the energy of photons from the light source to activate a catalyst (Figure 9). When photons have higher energy than the band gap of a photocatalyst such as TiO2, they will be adsorbed and electrons in the photocatalyst will be promoted to the conduction band thus leaving positive holes in the valance band. The resultant electron/hole pairs will participate in reduction and oxidation reactions with the substance presented on the photocatalyst surface. For instance, very powerful oxidative hydroxyl radicals are produced by oxidization of moisture with holes. The generated super oxidative species, including holes, will aggressively react with CH4 in the air to oxidize CH4 into CO2, which is a possible mechanism for photocatalytic oxidation destruction of CH4.
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