Pyrolysis method recycles motor oil into fuel

Estimates suggest that changing the oil in cars and trucks produces about eight billion gallons of used motor oil each year around the world. In the US and some other countries, some of that dirty oil is collected and re-refined into new lubricating oil or processed and burned in furnaces to heat buildings. However, such uses are far from ideal because of concerns over environmental pollution from re-refining oil and burning waste oil.

’Transforming used motor oil into petrol can help solve two problems at once,’ said Howard Chase, professor of biochemical engineering at Cambridge University. ’It provides a new use for a waste material that’s too-often disposed of improperly, with harm to the environment. In addition, it provides a supplemental fuel source.’

One technique used to convert motor oil into fuel uses pyrolysis, a process that involves heating oil at high temperatures in the absence of oxygen. Pyrolysis breaks down the waste oil into a mix of gases, liquids, and a small amount of solids. The gases and liquids can then be chemically converted into gasoline or diesel fuel. However, the current processes heat the oil unevenly, producing gases and liquids not easily converted into fuel.

Chase and his research team state that their new pyrolysis method overcomes this problem. In lab studies, his doctoral students, Su Shiung Lam and Alan Russell, mixed samples of waste oil with a highly microwave-absorbent material and then heated the mixture with microwave radiation. The new pyrolysis technique appears to be highly efficient, converting nearly 90 per cent of a waste oil sample into fuel. So far, the scientists have used the process to produce a mixture of conventional gasoline and diesel.

’Our results indicate that a microwave-heated process shows exceptional promise as a means for recycling problematic waste oil for use as fuel,’ Chase and Lam said. ’’The recovery of valuable oils using this process shows advantage over traditional processes for oil recycling and suggests excellent potential for scaling the process to the commercial level.’