Process Integration Working Group

The concept of anaerobic digestion as a ‘free-standing’ energy production platform with dedicated feedstock is relatively new. Conventionally, AD has been part of a more complex industrial process, such as wastewater treatment, where it is used as a means of treating wastes either at end-of-pipe or as process side streams. AD is now almost always considered when proposing a biorefinery concept, as it provides a means of recovering energy from the waste biomass streams after extraction or conversion of the targeted component. This occurs in bioethanol production and also for biodiesel, plant fiberising processes, polylactide production; and is likely to be the case in algal-based biorefineries. In addition, AD is likely to be the technology of choice for processing the aqueous residue streams from pyrolysis, high temperature liquefaction (HTL) and gasification. Although such ideas have been proposed, little data is available on how this can be achieved or how the resources entering the biorefinery can best be optimised. Process modelling is proving to be a powerful tool for optimising energy and materials usage in industry, and has become an essential part of any evaluation of a chemical plant, using techniques like Pinch Analysis for heat and water integration, and software such as the industry-standard Aspen Plus for full process energy and utility stream integration.