A citrus agent found in waste tyres could yield commercial opportunities beyond those offered by existing recycling technologies, research has discovered.
Stellenbosch University, in partnership with the Recycling and Economic Development Initiative of South Africa, has found that a substance called dipentene, a racemic mixture of D- and L-limonene, can be derived from waste tyres in recoverable amounts.
In 2014, MRW reported the same substance being extracted by steam distillation and microwave diffusion from citrus peel waste in large-scale operations in Brazil and Florida.
Dipentene is found in the liquid oil product of tyre pyrolysis. The university is currently trying to improve the recoverable yield of dipentene, to prepare the process for industrial implementation.
D-limonene is the main odour constituent of citrus and is used in food manufacturing and some medicines, such as a flavouring to mask the bitter taste of alkaloids. It is also used as a fragrance in perfumery, aftershave lotions and bath products.
The mixture of D- and L-limonene is currently used as a solvent for cleaning purposes, such as the removal of oil from machine parts, as a paint stripper, a botanical insecticide or a fragrant alternative to turpentine.
Recycled tyres are generally reused as ground rubber in asphalt or for sporting surfaces, or to generate tyre-derived fuel.