A method for controlling methanogenesis during environmental applications by inhibiting methane production of methanogens located in an environmental medium. The inhibiting of the critical biochemical pathways specific to the methanogens is achieved by providing one or more antimethanogenic reagent (AMR) compounds to the environmental medium. The AMR may include, for example, naturally-occurring statins (which may be found in red yeast rice), essential oils, certain synthetic compounds or combinations thereof. Limiting the methanogens in the environmental medium allows the slower-growing, halo-respiring bacteria that are utilized to dechlorinate containments to utilize the hydrogen donors (either naturally occurring or provided via fermentable substrates provided as part of a reduction process). The AMRs are harmless to the halo-respiring bacteria. The AMRs can be provided alone or along with various organic hydrogen donors, zero-valent iron (ZVI) or other reduced metals in order to enhance the biodegradation
