Advanced Biological Platform for Generation of High-Purity Methane and Other Products: A Circular Economy Approach

Conventional organic waste management mainly relies on landfilling, incineration, and composting, all of which are associated with significant environmental impacts including, greenhouse emission, air pollution and soil and water contamination. These technologies are not based on efficient resource recovery or aligned with the circular economy approach. Biological processes such as anaerobic digestion (AD) of organic waste offers potential, however; significant research must be directed towards addressing the technical challenges including variable waste composition and loading rate, low energy yield, process instability, and limited knowledge on the efficient valorization of digestate. Additionally, the implementation of anaerobic digestion in cold climates represents a knowledge gap that should be filled. We aim to address the above challenges by building upon the knowledge generated from our multi-year research into anaerobic digestion-microalgae cultivation biorefinery and develop a novel in-situ biomethanation process for production of high-purity methane from mixed organic waste (e.g., food waste and waste sludge), while recovering nutrients and other bioproducts. In the process of in-situ biomethanation, catalyzed by archaea platform, the bioconversion of carbon dioxide to methane is driven by hydrogen gas supplementation. The major challenges identified is metabolic limitation due to the inhibitory effects of increased partial pressure of hydrogen, and physico-chemical limitation arising from low gas-liquid mass transfer of hydrogen. The configuration of novel Anaerobic Baffled Reactor (ABR), developed in our lab will be modified. We hypothesize that installing a network of pipes for even flow distribution, hydrogen supplementation to the last compartment, which is rich in methanogens and incorporating membrane to reduce wash-out will result in higher biodegradation rate, process stability, methane purity and enhanced robustness with respect to waste heterogeneity and load fluctuation. A closed-loop organic waste valorization approach will be possible by recovering nutrients from digestate. Microalgae cultivation on digestate as well as photobioelectrochemical system will be individually evaluated for nutrient recovery. We hypothesize that innovative system design, acclimatization and developing algae-bacteria consortium will eliminate significant dilution required to overcome the inhibitory effect of digestate constituents on algal growth. Our proposed approach will target the key challenges in the organic waste management sector including the mixed waste heterogeneity, flowrate fluctuation, relative low energy yield and loss of valuable nutrients. Implementing a holistic array of novel advanced archaea-bacteria platform integrated with nutrient recovery approaches offers significant potential to transform organic waste management systems into a sustainable, revenue generating platform, aligned with the concept of circular economy.