GHG Emission Reduction and Renewable Energy Production Through Anaerobic Digestion of Organic Wastes and Biogas Production

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This research plan is designed to cover three main research directions related to biogas production and anaerobic digestion including, nutrient recovery, feedstock recipe optimization and Anaerobic Digestion (AD) process modelling. The main goals are: I) to develop an integrated nutrient recovery process for Nitrogen, Phosphate and Potassium (NPK) recovery from anaerobic digestate to use as biofertilizer, II) to optimize the feedstock recipe to maximize biogas production and minimize the process inhibition using different combinations of varied types of organic materials, and III) to model the AD process including pre-treatment, digestion and downstream processing considering all possible inhibitory effects, ammonia removal and nutrient recovery in the process. Based on this detailed research plan, there are several breakdown objectives for each of these directions ultimately leading to address these current important challenges in the biogas field. In the first research direction, the focus will be on separating NPK from digestate for two objectives. First, to produce a nutrient-rich product as biofertilizer replacing commercial inorganic fertilizers reducing GHG emission and closing the loop for nutrients. Second, to decrease the volume of the digestate to avoid the current transportation costs and environmental issues. The separation methods to be tested include electromagnetic phosphorous removal and biopolymer treatment techniques. Different separation techniques such as membrane filtration, evaporation, slope screen and the combination of these techniques will be investigated to develop a process to produce biofertilizer and water from digestate. In the second research direction, the main focus will be on developing a guideline to formulate the optimized feedstock recipes maximizing the productivity and minimizing the process inhibition while providing all necessary substrates for healthy biogas plant operation. This will allow to formulate the feedstock recipe based on each material category (protein, fat, CHO, lignin and fiber content) to predict the biogas production in the plants where specific feedstock materials are available. The main benefit would be maximizing the productivity without the need to run time-consuming and expensive lab-tests. Finally, the focus of the third research direction will be on developing a model to simulate AD processes from front-end to back-end including pretreatment, digestion and downstream processing. One of the main focuses of this project will be investigating the inhibitory effect of ammonia and also to enhance the model by incorporating the ammonia stripping process. The main benefits of the proposed project include evaluation of new substrates with unknown behavior, reduced cost for substrate evaluation, process stability verification, prediction of critical components, simulating the anaerobic digestion combined with ammonia striping and substrates behavior of complex interactions in a digester.