TPAD of whole and thin bioethanol residues

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The market for Distillers Dried Grains with Solubles (DDGS) is saturated and excess stillage is a waste problem to the bioethanol industry. Stillage handling is one of the major limitations of the corn to ethanol process, since DDGS drying and stillage evaporation account for approximately 30.3 and 16.5% of total process energy consumption, respectively. Each litre of ethanol can generate up to 20L of stillage with total chemical oxygen demand of (TCOD 100-200 g/L), and thin stillage evaporator condensate is the largest wastewater contributor. Although anaerobic digestion (AD) has lower alkalinity and nutrient requirements compared to aerobic biodegradation and has great potential to reduce the organic pollution of stillage and produce methane as fuel for the bioethanol plant, it has not been applied with the magnitude possible. Studies to date focus on digestion of thin stillage, leaving the majority of the methane potential of the stillage untreated. However, if whole stillage (3-5 times more concentrated than thin stillage) can be treated directly in AD at practical solid reaction times (SRT) bypassing evaporation and drying it could make existing and new bioethanol facilities energy-independent while solving a major bottle neck and waste problem. Establishment of this technology would also open international markets for Canadian industry. The main objective of this research is to study the biodegradation performance and kinetics [biogas production, TCOD, total solid (TS) and volatile solids (VS) removal efficiencies] of whole and thin stillage using batch and continuous-flow AD under both thermophilic, mesophilic and temperature phased digestion (TPAD) (thermophilic/mesophilic or mesophilic/thermophilic;T/M vs M/T) conditions.