Separation of chemicals obtained from the anaerobic fermentation of organic waste

This project, which includes both computer simulation and experimental investigation, is aimed at the optimisation of distillation conditions for the separation of diluted aqueous mixtures of ethanol and volatile fatty acids (VFA’s), mainly acetic acid and butyric acid. These chemicals are essential in our everyday life and are currently produced in millions of tonnes per year. E.g. ethanol is mainly used as renewable fuel, as an alternative to conventional petrol, while acetic acid is used as an intermediate in the chemical industry for the productions of plastics, paints etc.

The problem is that the current production processes used to manufacture these chemicals raise many doubts about their sustainability and environmental impact. E.g acetic acid is produced from natural gas, a non-renewable fossil fuel, using a high-pressure and high-temperature process, in the presence of heavy metals as catalysts.

As an alternative to the current processes, these chemicals can also be produced by the anaerobic fermentation of organic waste, e.g. municipal solid waste, farm waste, forestry residues and many others. Although anaerobic fermentation of organic waste would be a much more sustainable and environmentally friendly process, one of the main problems that prevents its use for the production of these chemicals at commercial scale is the separation of the chemicals from water after the fermentation process.

Therefore, this project is aimed at the simulation and experimental investigation of the distillation of diluted aqueous solutions of ethanol and VFA’s in order to determine the following:

- the effect of feed concentration and pH on the number of stages and energy requirements of the distillation column(s);
- the effect of the operating parameters of the distillation, e.g. reflux ratio, column pressure, feed location, on the separation efficiency;
- the design of the optimum sequence of distillation columns for the separation of the fermentation products.

The successful candidate should have, or expect to have, an Honours Degree at 2.1 or above (or equivalent) in Chemical Engineering.

Essential background: Chemical Engineering

Knowledge of: Interest in separation, distillation, simulation software and in doing experimental work