International study develops ground-breaking method of making biodiesel from dirty old cooking oil

A scientist from the University of Plymouth has played a key role in new research which has developed a powerful, low-cost method for recycling used cooking oil and agricultural waste into biodiesel, and turning food scraps and plastic rubbish into high-value products.

The method, outlined in a study published in Nature Catalysis, harnesses a new type of ultra-efficient catalyst that can make low-carbon biodiesel and other valuable complex molecules out of diverse, impure raw materials.

Waste cooking oil currently has to go through an energy-intensive cleaning process to be used in biodiesel, because commercial production methods can only handle pure feedstocks with 1-2% contaminants.

The new catalyst – developed by an international team led by RMIT University in Australia – is so tough it can make biodiesel from low-grade ingredients, known as feedstock, containing up to 50% contaminants.

It is also so efficient it could double the productivity of manufacturing processes for transforming rubbish like food scraps, microplastics and old tyres into high-value chemical precursors used to make anything from medicines and fertilisers to biodegradable packaging.

Dr Lee Durndell, Lecturer in Chemistry at the University of Plymouth, is among the study’s authors along with colleagues from RMIT, University College London, University of Manchester, University of Western Australia, Aston University, Durham University and University of Leeds.

He has spent many years working in the fields of nanomaterials and catalysis science, in particular looking at ways to develop next-generation materials and processes to tackle the grand challenges of society, including green chemicals and energy production.

For this study, he worked on the synthesis and optimisation of material properties, before characterising them using cutting edge electron microscopy analysis.

Dr Durndell said:

“The ability to control how a material or process behaves at the atomic scale is very difficult, due not only to the length of scales we are looking at but also our inability to control the location of individual components with this level of detail. Nature is full of examples where organisms achieve this level of control to produce energy, reproduce or even communicate. Taking lessons from nature, the dream is to be able to replicate this level of control within our own man-made processes – with this work, it seems we are one step closer to achieving this.”

Lecturer in Chemistry, Dr Lee Durndell

To make the new ultra-efficient catalyst, the team fabricated a micron-sized ceramic sponge (100 times thinner than a human hair) that is highly porous and contains different specialised active components.

Molecules initially enter the sponge through large pores, where they undergo a first chemical reaction, and then pass into smaller pores where they undergo a second reaction.

It’s the first time a multi-functional catalyst has been developed that can perform several chemical reactions in sequence within a single catalyst particle, and it could be a game changer for the $US34 billion global catalyst market.

The sponge-like catalysts are cheap to manufacture, using no precious metals, and making low-carbon biodiesel from agricultural waste with these catalysts requires little more than a large container, some gentle heating and stirring.

While the new catalysts can be used immediately for biodiesel production, with further development they could be easily tailored to produce jet fuel from agricultural and forestry waste, old rubber tyres, and even algae.

Co-lead investigator Professor Adam Lee, from RMIT, said:

“The quality of modern life is critically dependent on complex molecules to maintain our health and provide nutritious food, clean water and cheap energy. These molecules are currently produced through unsustainable chemical processes that pollute the atmosphere, soil and waterways. Our new catalysts can help us get the full value of resources that would ordinarily go to waste – from rancid used cooking oil to rice husks and vegetable peelings – to advance the circular economy. And by radically boosting efficiency, they could help us significantly reduce environmental pollution from chemical manufacturing and bring us closer to the green chemistry revolution.”

Professor Karen Wilson, also co-lead on the research, added:

“Catalysts have previously been developed that can perform multiple simultaneous reactions, but these approaches offer little control over the chemistry and tend to be inefficient and unpredictable. Our bio-inspired approach looks to nature’s catalysts – enzymes – to develop a powerful and precise way of performing multiple reactions in a set sequence. It’s like having a nanoscale production line for chemical reactions – all housed in one, tiny and super-efficient catalyst particle.”

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