Fuels that are produced from nonpetroleum-based biological sources may become greener and more affordable, thanks to research performed by the University of Birmingham and University of Illinois’ Prairie Research Institute that examines the use of a processing catalyst made from palladium metal and bacteria.

Biofuels are made from renewable materials such as plants or algae, and offer an alternative to petroleum-based sources. However, many biofuels are costly to produce because the precursor product, bio-oil, must be processed before it is sent to the refinery to be turned into liquid fuel. The research team have identified and tested a new processing method.

Professor Joe Wood of the University of Birmingham said, “Bio-oils could potentially form an increasing part of the transport fuel mix. Although the government intends to phase out petrol vehicles by 2040, biofuels could still be required for hybrid vehicles, as well as haulage, aviation and marine applications. The conversion of algae to crude bio-oil is attractive because it does not use food crops and is near carbon neutral”.

Published in the journal Fuel, their findings point to a cheaper, more environmentally friendly and renewable catalyst for processing that uses common bacteria and the metal palladium, which can be recovered from waste sources such as discarded electronics, catalytic converters, street sweeper dust and processed sewage.

The bio-oil produced in the lab from algae contains impurities like nitrogen and oxygen, but treating it with palladium as a catalyst during processing helps remove those impurities to meet clean-air requirements.

For the palladium to do its job, the bio-oil needs to flow past it during processing. Previous studies have shown that allowing the oil to flow through porous carbon particles infused with palladium is an effective method, but those carbon particles are not cheap.

Professor Lynne Macaskie, from the School of Biosciences at the University of Birmingham, developed techniques for supporting an array of metal nanoparticles on bacteria, which act as a renewable catalyst support.

“For many years we have collaborated to test such particles in a range of catalytic applications in Chemical Engineering, ranging from organic chemistry to fossil fuel upgrading, so this work represents the next step in making renewable biofuels using the catalysts”, said Professor Wood.

To test the effectiveness of the new method, the team performed a variety of chemical and physical analyses to determine if their new processing treatment produced a liquid fuel that is comparable in quality to one made using the commercially produced catalyst.

“We found our product to have similar effectiveness to a commercial catalyst” said Professor Wood. “Key to the increase in the biofuel market is the removal of nitrogen and oxygen components to make them more in-line with fossil fuel compositions so they can be blended with diesel for use in engines”.

The more costly commercial catalyst has the added benefit that it can be used over and over without extensive processing, whereas this group’s palladium-on-bacteria catalyst would need to undergo processing to be reused.

The researchers at Biosciences are working on developing recycled catalyst using second life bacteria from fermentation processes and precious metals extracted and recycled from road dust.

The work was carried out in collaboration with Dr B.K. Sharma of the Prairie Research Institute, University of Illinois at Urbana Champaign funded through the Birmingham-Illinois Partnership for Discovery, Engagement and Education programme. The Natural Environment Research Council, UK also supported this research.

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The paper “Nanoparticles of Pd supported on bacterial biomass for hydroprocessing crude bio-oil” is available online. DOI: 10.1016/j.fuel.2017.08.007