Anaerobic digestion of thin stillage for energy recovery and waste management

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IGPC Bioethanol produces 170 million litres of ethanol per year, along with 120,000 tons of distillers grains. This process results in production of 3.4 billion litres of thin stillage with high organic content. Currently, thin stillage is concentrated within an energy intensive process using evaporators, corn oil extracted from the syrup for biodiesel production and the concentrated syrup is added to the distiller's grain. Given that the process of evaporation of thin stillage is energy intensive and IGPC has recently developed the capability to produce high quality protein distiller's grain which can not be combined with the syrup, finding alternative application for thin stillage is crucial. The objective of this project is threefold. First, we aim to reduce the organic contaminants present in waste streams of corn-bioethanol industries and thus to mitigate their adverse environmental impacts using anaerobic digestion technology. Second, as a result of anaerobic digestion of organic wastes, energy will be produced for electricity generation to be used in the bioethanol production plant. The third objective is to recycle the effluent of anaerobic digester to the front end of the plant in order to reduce the amount of fresh water required in the process. Production of each liter of corn-ethanol results in generation of 20 liter of waste streams with high level of organic contaminants, namely thin stillage. Therefore, management of thin stillage waste streams using the technology of anaerobic digestion will largely improve the sustainability of corn-bioethanol production. Given that limited fresh water resources are available on earth, development of a technology that enables recycling of the industrial wastewater to be used in the plant is significantly important. To this end, the main objective of this project is to establish the optimum operation conditions of an Anaerobic Baffled Reactor (ABR) that lead to the highest bioconversion rate of organic contaminants present in thin stillage into biogas as a source of energy. Establishment of the optimum condition for the highest performance of the bioreactor informs process design for scaling up the reactor.