Methane produced by ruminant livestock accounts for more than 10% of Australia’s net total greenhouse gas emissions. Reducing these emissions will have an immediate benefit for the environment, will improve the ‘clean and green’ image of Australian beef and may also have a positive impact on the animals’ energetic efficiency. Our current understanding of the microbial processes underpinning methane production is incomplete and the key to manipulating these emissions in the future will flow from fundamental improvements in our knowledge of metabolic schemes that provide alternatives to methanogenesis as sinks for hydrogen. This project has been able to define at the molecular level the key microbial populations involved in methanogenesis and the bacteria that could compete for hydrogen through the metabolic processes of reductive acetogenesis and fumarate reduction. This has enabled both the isolation of potent hydrogen utilising bacteria and the development of a suite of molecular tools to monitor the abundance and function of these populations in the rumen. Feeding strategies that reduce methanogenesis can now be evaluated accurately for their potential to promote alternative sinks for hydrogen that result in the capture of energy for use by the animal rather than being lost as methane.