Green tyres: alternatives to petrochemical rubber

Traditionally, rubber tyres have been produced from butadiene - a petrochemical with a market size of more than £25 billion. However, the recent trend towards shale gas exploitation, particularly in the US, has led to a significant reduction in the amount of butadiene available.

Natural gas chemical feedstocks contain far fewer C4 hydrocarbons than the traditional oil alternatives utilised in petrochemical production. Butadiene prices have been volatile over the last 12 months, rising by as much as 30 per cent at one point amid concerns regarding the supply gap, which is expected to widen further as shale gas exploitation becomes more commonplace.

For several years, the rubber industry has been searching for alternatives to butadiene, but the need for a viable replacement becomes more and more pressing as production costs soar, while environmental concerns continue to drive interest in so-called 'green tyres'.

Bio-isoprene
One of the most thoroughly-researched options currently being explored centres on the development of a synthetic version of isoprene, a gas given off by a large number of trees, ferns and mosses.Isoprene is utilised by many plants as a method to deal with heat stress as an alternative to evaporation and this attribute is considered to be vital for the production of tyres.

A team from Michigan State University (MSU) used Environmental Protection Agency plants to measure the rates of isoprene emitted and created models to calculate global production of the molecule.

The vast majority of automobile tyres are manufactured using natural rubber derived from latex-bearing trees, and this rubber is made up of isoprene. Since MSU's research showed it is not sustainable to satisfy global tyre demand if reliant solely on natural isoprene, the team then began to search for a man-made version.

Scientists at the university discovered it is possible to genetically engineer an enzyme to produce bio-isoprene from bacteria, and several private companies have taken this research further, discovering the same process can be used to synthesise isoprene from sugar molecules.

This bio-isoprene is then used as a monomer to create a polymer called polyisoprene, which is chemically equivalent to the polyisoprene polymer derived traditionally from petroleum.

Dandelions
Alternative studies are taking place into the possibility of creating renewable rubber for tyre manufacture from one of the most common garden pests - the dandelion.

Researchers from the University of Munster in Germany have investigated an elastic gum found within sap derived from Russian varieties of the garden weed. This was found to be comparable to natural rubber extracted from trees grown in subtropical plantations.

The team is now assessing the growth, extraction and production processes, investigating whether it will be commercially-viable to use this gum in the manufacture of automobile tyres.

Should these trials prove successful, green tyres produced using this molecule would have much less of an environmental impact than the petrochemical-derived varieties, using a sustainable source and making use of fallow land that would otherwise be deemed unfit for the harvest of agricultural crops.As a result of greater requirements from developing nations such as China, India and Brazil, global demand for natural rubber is forecast to exceed supply by as much as 20 per cent by 2020. With the cost of harvesting and transportation comparatively much smaller, the development of alternative molecules for use in the manufacture of green tyres is of significant interest to the wider rubber industry.

Robinson Brothers' Robac Technology team has extensive experience in providing specialist solutions for heightened regulatory health, safety and environmental concerns. Our technical service team will provide bespoke solutions to meet your needs, providing chemicals used in both wet and dry rubber applications, as well as additional polymer additives. To learn more, contact our Robac Technology division [email protected]