Application of Caffeine for Higher Anaerobic Digestion Stability

Anaerobic digestion (AD) is a simple industrial process that can utilize most types of organic wastes and provides various benefits such as pollutants degradation, pathogen removal and generation of methane gas as biofuel product. The stability is one of the primary limitations of this process due to the fragile nature of microorganisms (especially methanogens). Caffeine is generally considered to be toxic to microbes and it contributes as an environmental stress factor when seasonal and scattering coffee processing wastewater is treated at the AD system. The wastewater generated from de-pulping and de-husking steps contains high caffeine content, causing the instable AD operation. Our preliminary research demonstrates that long term exposure under relatively low level of caffeine doesn’t affect the performance of AD reactors, but significantly increases their caffeine tolerance. The microbial community analysis did not reveal an obvious change on microorganisms, suggesting that whole bacteria community survived under the high caffeine habitat.