The goal of this project is to understand the interplay between members of the microbial community in anaerobic digesters that convert food waste to useful methane gas to maximize performance and increase the ability of the reactors to handle various food waste types. The key to success is determining how the microbial communities in the reactors that perform the waste-to-gas conversion are assembled under different environmental conditions. The project will involve a deeply integrated program of reactor experiments, molecular analysis, and mathematical modeling. Graduate and undergraduate students, including students from a historically black university, will be trained during the course of this project. The results have the potential to transform our understanding of the science of waste conversion, and benefit municipalities and waste treatment industries as they seek realistic ways of converting waste to energy, thus increasing our energy efficiency while simultaneously reducing waste generation.<br/> <br/>Directly linking microbial communities to bioreactor function and environmental conditions is a great challenge for biological process engineers. This link can be accomplished by using the ecological theory of microbial community assembly under dynamic conditions to guide the design of hypothesis-driven experiments. The overall objective of this project is to elucidate the relationships between anaerobic co-digester operating conditions, microbial communities, and reactor functions, and to use these insights to achieve faster transitions, higher methane yields, and develop reactors that are more resilient and resistant to perturbations. The specific objectives are: 1) To determine to what extent deterministic and stochastic processes contribute to shaping the assembly in anaerobic co-digesters under changing conditions; 2) To determine the key microbial populations, interactions, and co-occurrences under different and dynamic conditions; 3) To use the insights from microbial community assembly to increase resilience and resistance in response to varying substrate types and loadings, and maintain high methane yields; and, 4) To broaden participation of underrepresented sectors in microbiology and engineering research, and to disseminate the practical implications of the findings to the wastewater community. This study will integrate a methodological and theoretical community assembly frameworks with next generation DNA and RNA sequencing approaches, bioreactor studies, and mathematical modeling to investigate and improve an engineered biological process. This integrated approach represents a novel way of investigating biological processes in engineered systems and opens up a new research field that will address basic questions about anaerobic co-digestion and lead to a better understanding of other biological processes involved in waste treatment, energy production, and resource recovery. This project will contribute to the education of graduate and undergraduate students, including one from St. Augustine's University, for two summers in the areas of engineering, microbiology, and molecular biology. This project will benefit municipal and industrial wastewater treatment plants as they seek sustainable and realistic ways of converting waste to energy. Results from this project will be incorporated in microbiology workshops for wastewater treatment professionals.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.