Integrated Modeling Tool to Optimize Co-digestion of Solid Wastes

摘要

Anaerobic digestion processes can be improved by engineering the addition of other organic wastes of different compositions to the feedstock. This paper presents an integrated model to determine the optimal ratio of such additions once the practical characteristics and hydrolysis kinetics of each feedstock are known. Several model nodes were built in an integrated manner around the International Water Association Anaerobic Digestion Model Number 1, (IWA-ADM1) using the Matlab-Simulink simulation platform. Transformer model nodes were developed to estimate the waste fractions of carbohydrates, proteins and lipids to generate a detailed input for ADM1. Hydrolysis nodes were modeled separately for each feedstock. The fluxes from the hydrolysis nodes were combined and generated a detailed input vector to the IWA-ADM1. The integrated model was applied to a co-digestion case study of diluted dairy manure and kitchen wastes. The integrated model implementation lead to an improved simulation speed that made it feasible to run calibration and optimization of this case study. The integrated model was used to calibrate the hydrolysis kinetics of each waste and particulate fractions using bench scale experiments. An optimization case study based on 100 steady state simulations determined the operational limits for maximum methane production. For the tested waste concentrations, the optimum retention time was 10 days with an optimal kitchen waste to diluted manure ratio of 75%.