Replacing crude oil with plant derived chemicals

To become truly carbon neutral we will have to leave the oil in the ground and use the carbon that is already in the air around us.

Dr Ben Greatrex, Pharmacy, School of Rural Medicine

Our modern life has been built on oil. The energy from oil powers our cars and planes, and oil is used to make the plastics and polymers in consumer products and the drugs that we use to improve our health. However, oil is finite and its extraction and use increases the amount of carbon dioxide in the air which is leading towards catastrophic global warming.

Replacing oil in the transportation sector is underway, the internal combustion engine is going the way of the dodo, and the rise of the electric car is inevitable. But what about the chemicals we need to sustain modern life that are all based upon the element carbon mainly derived from oil? To become truly carbon neutral we will have to leave the oil in the ground and use the carbon that is already in the air around us. This is still difficult and expensive for humans, however, plants are experts at collecting carbon from the air.

A team of researchers based in the Disciplines of Chemistry and Pharmacy has been using plant based chemicals as oil replacements for the manufacture of human drugs. Most carbon captured by plants is converted to cellulose which is used to give structure to the plant and is a unique challenge due to the nature of the molecule. Dr Ben Greatrex, a chemist who leads the team of researchers, explains; “Cellulose is a very long polymeric material which is difficult to use chemically. Humans have historically either burnt the cellulose which is found in wood for heating or turned it into paper, but haven’t previously used it as a chemical building block. Chemists work with discrete small molecules when manufacturing drugs, analogous to building a model out of Lego blocks; cellulose is the equivalent of the Millennium Falcon, with all the pieces already joined together. It has to be broken down before we can make something new.”

The UNE team works with an Australian company Circa, that operates a facility in Tasmania and uses pyrolysis (heating without oxygen) to transform cellulose present in woodchips and other plant products that would otherwise be waste. Adding catalysts to the mixture before heating, the pyrolysis process is selective and mainly one small molecular building block known as levoglucosenone is formed. This compound has not been available in large amounts before, so the types of chemistry that can be used with this molecule have not been investigated.

The team have been investigating how this bio-based chemical could react, believing that this might lead to shortcuts to making valuable small molecules, like drugs. The teams insights proved to be correct and they have developed synthetic procedures to turn this bio-based chemical into the important HIV drug Indinavir (IDV), effectively converting sawdust into a material almost as valuable as gold! Other materials that have been made include dairy lactone, the compound in milk that provides flavour, which has been done in collaboration with the French research institute AgroParisTech, and the development of a bio-based solvents has been explored with the University of Strathclyde in the UK. The use of plant derived solvents has the potential to replace toxic petrochemical derivatives with biodegradable alternatives.

The shift away from oil in the chemicals sector is still in its infancy, and lags behind other industries that are moving to renewable solutions. An understanding of the chemistry of the materials derived from plants, particularly cellulose, will be the first step to increase adoption of these materials in the future.