Using 3D printing technology to clean key pollutants from fuel oils

Introduction

Recircle Ltd (Recyclatech Group Ltd) has developed a unique devulcanisation (i.e. desulphurisation) biotechnology that enables the controlled reprocessing of used tyres into reusable rubber. The company is also involved in the biodesulphurisation of thiophenes present in diesel and other petrochemical derivatives and the production of biosurfactants as nutraceuticals. Recircle has extensive experience in the cultivation of the biotechnologically important alkanotrophic bacteria routinely employed in its research activities.

The company is involved in biotechnological projects that fit into decarbonisation leading to the reduction and elimination of anthropogenic contribution of pollutants and greenhouse gasses to the atmosphere, in this case oxides of sulphur, through reduction of sulphur in fuels.

Challenge

Environmental targets require the reduction in the sulphur content of fuels, however, current inorganic catalysts used in fuel desulphurisation are expensive and have high associated energy costs. A potential alternative lies in biodesulphurisation (BDS) – using biological processes to remove the sulphur. It is thought that the mild temperature and pressure conditions, and the inexpensive cellular biocatalysts used, would save on expensive metallic catalysts, energy costs and the use of hydrogen, even if only small numbers of the traditional hydrodesulphurisation processes were replaced.

The problem, however, is that BDS technology needs to overcome issues such as low enzyme activity, low mass transfer rates, and cellular deactivation, in order to be commercially possible.

Solution

IBioIC awarded £49,990 to enable Recircle and the University of Edinburgh to develop and test 3D printed bioreactors for the deep desulphurisation of fuel oils. This proof of concept project would establish whether immobilising the desulphurising bacteria would improve the efficiency of the process.

Simone Dimartino’s group at University of Edinburgh developed a novel 3D printed hydrophobic support (gyroid) material, on which biofilms of alkanotrophic desulphurising bacteria were formed.

The bacteria-laden gyroids exhibited biodesulphurisation reactions when a wholly aqueous medium was used as the feed.

Experimentation using biphasic medium containing 10% hexadecane with polluting organosulphur compounds (thiophenes) generated positive results, leading to the next steps to construct robust pilot-scale reactors.

Outcome

This project advanced work on a commercial biodesulphurisation process using the University of Edinburgh’s expertise in 3D printing to create a scaffold to support Recircle’s proprietary bacteria.

The continuous flow process developed is also applicable to other commercially interesting areas for the company.

Recircle has been able to demonstrate the value of desulphurising bacteria and Simone Dimartino’s group has been able to explore a practical application of their 3D printing technology for bacterial bioreactors.

This work will underpin future grant applications and has already resulted in a scientific paper containing some of the work involved.