What should be done with the millions of used tyres?

In 2021, 53.8 mil­lion tyres – across all cat­e­gories – were placed on the mar­ket¹. That’s more than 567,000 tonnes of a mix­ture of rub­ber, car­bon, sil­i­ca, steel, tex­tiles, and chem­i­cals. And yet tyres have a lifes­pan of just a few years… Do you know what hap­pens to our used tyres? In the same year, over 532,000 tonnes of tyres were col­lect­ed, giv­ing a nation­al col­lec­tion rate of 111.5%²!

Since 2003, organ­i­sa­tions that place tyres on the French mar­ket – man­u­fac­tur­ers, dis­trib­u­tors, etc. – have been oblig­ed to take respon­si­bil­i­ty for tyres at the end of their life cycle, based on the prin­ci­ple of extend­ed pro­duc­er respon­si­bil­i­ty (EPR). In Europe, despite there being no spe­cif­ic leg­is­la­tion gov­ern­ing the sec­tor, two direc­tives apply. As a result, many Euro­pean coun­tries are imple­ment­ing EPR or oth­er schemes to ensure the col­lec­tion of used tyres. In a study of 51 coun­tries around the world³, it is esti­mat­ed that more than 17 mil­lion tonnes of end-of-life tyres are col­lect­ed each year, leav­ing 8 mil­lion tonnes uncol­lect­ed. Chi­na, the Unit­ed States, Europe, Cana­da, India and South Korea are among the biggest and/or best collectors.

We need to recov­er used tyres in one way or another

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Once they have been col­lect­ed, they can be recy­cled in a vari­ety of ways. In France in 2021, 15% of used tyres will be reused. Most of the used tyres col­lect­ed (46.8%) are recov­ered for ener­gy pur­pos­es, almost exclu­sive­ly in cement works. In this case, instead of using fos­sil fuels, tyres are used as an alter­na­tive fuel to pro­duce the ener­gy need­ed for cement kilns. The final way of recov­er­ing used tyres is through recy­cling. By 2021, 35.8% of used tyres will be recy­cled. Reduced to aggre­gate, melt­ed down in cement works or steel­works, or shred­ded: a whole range of new lives open up for tyres recov­ered as mate­ri­als. “Most of the tyres we recy­cle are trans­formed into mould­ed objects – such as speed bumps – sport pitch­es, drainage mate­r­i­al or are used in steel­works to replace some of the anthracite”, explains Jean-Philippe Fau­re from Ali­a­pur. In 2010, the organ­i­sa­tion assessed the envi­ron­men­tal impact of sub­sti­tut­ing end-of-life tyres for prod­ucts from dif­fer­ent sec­tors⁴. The ben­e­fits are clear for Astro­turf, mould­ed objects and cement works, but min­i­mal for reten­tion basins. A num­ber of envi­ron­men­tal indi­ca­tors exist. For exam­ple, sub­sti­tu­tion for Astro­turf avoids the emis­sion of 3 tonnes of CO₂ equiv­a­lent for each tonne of used tyres recov­ered. The process also uses 15 m³ less water.

Mate­r­i­al recov­ery from used tyres is the pre­ferred method of recov­ery under the Envi­ron­ment Code⁵, after re-use. How­ev­er, most end-of-life tyres are recov­ered in the form of ener­gy. “This sit­u­a­tion is spe­cif­ic to France; we don’t see the same trends in oth­er Euro­pean coun­tries,” explains Jean-Philippe Fau­re. “But it’s a one-off sit­u­a­tion and linked to recent Euro­pean reg­u­la­tions – aimed at ban­ning the incor­po­ra­tion of microplas­tics and the use of rub­ber gran­u­lates in syn­thet­ic sports pitch­es.” Anoth­er obsta­cle to recy­cling is the pos­si­ble out­lets. “We need to recov­er used tyres in one way or anoth­er, and the ener­gy recov­ery require­ments of cement works mean that they can absorb large vol­umes. We need to cre­ate ways of recov­er­ing mate­ri­als that require large vol­umes, and there­fore with suf­fi­cient added val­ue.” says Ludovic Moulin. Tougher reg­u­la­tions could, how­ev­er, push the indus­try to increase the pro­por­tion of end-of-life tyres recy­cled. “In 2020, the anti-waste law imposed a new tight­en­ing-up on the sec­tor: com­pa­nies must be accred­it­ed,” explains Thomas Grandin. This require­ment will be laid down in a decree and an order⁶ in 2023, set­ting out the spec­i­fi­ca­tions for the sector’s eco-organ­i­sa­tions. These impose recy­cling tar­gets on the tyres col­lect­ed: from 40% in 2024 to 42% in 2028 of the quan­ti­ties of waste col­lect­ed. “We have also not­ed that social accep­tance is a bar­ri­er, but there is no tech­ni­cal bar­ri­er to recy­cling,” asserts Jean-Philippe Faure.

Tyres are made up of over 200 dif­fer­ent mate­ri­als. But ful­ly devel­oped sep­a­ra­tion process­es do exist. The aim is to iso­late the dif­fer­ent com­po­nents to offer prod­ucts with a high added val­ue. “For some years now, the trend has been towards the devel­op­ment of pyrol­y­sis,” points out Ludovic Moulin. By heat­ing the tyre to a very high tem­per­a­ture and in the absence of oxy­gen, it is pos­si­ble to recov­er a num­ber of prod­ucts: car­bon black, pyrol­y­sis oil, steel-met­al rein­force­ments, gas, tex­tiles, etc. Although still mar­gin­al in many coun­tries, this process is the main way of recov­er­ing end-of-life tyres in Chi­na, Thai­land, Indone­sia and Mex­i­co, “because of insuf­fi­cient or non-exis­tent envi­ron­men­tal con­straints,” explains Ludovic Moulin. “Between the health cri­sis and fears about raw mate­r­i­al sup­plies, the cir­cu­lar econ­o­my is gain­ing momen­tum and the mar­ket is now open­ing up to these new prod­ucts,” com­ments Thomas Grandin. In Europe, Miche­lin has announced the cre­ation of the first pyrol­y­sis site with Swedish start-up Envi­ro, which is set to han­dle 1 mil­lion tonnes of used tyres by 2030. “Oth­er projects are under­way in Ger­many (Pyrum Inno­va­tions), Spain (L4T and Green­val Tech­nolo­gies) and the UK (Bold­er Indus­tries),” adds Jean-Philippe Fau­re. “This approach is set to take off in the next few years.”

Fund­ed by the Euro­pean Union and coor­di­nat­ed by Miche­lin, the Black Cycle project⁷ aims to demon­strate the via­bil­i­ty of the cir­cu­lar econ­o­my for pyrol­y­sis. The con­sor­tium aims to opti­mise the pyrol­y­sis process. The aim? Zero waste. Both the car­bon black and the pyrol­y­sis oil – trans­formed into car­bon black – recov­ered will be entire­ly reused to man­u­fac­ture new tyres. Oth­er projects aim to explore new ways of recov­er­ing used tyres. “Pub­lic works are the most promis­ing sec­tor for the future,” says Jean-Philippe Fau­re. “For exam­ple, there is a need for new types of back­fill, capa­ble of absorb­ing shock and being light and flex­i­ble.” Recy­cled tyres could even be incor­po­rat­ed into pave­ments using a mix­ture of recy­cled con­crete and rub­ber aggre­gates⁸.

In France, the joint lab­o­ra­to­ry for advanced mate­ri­als recy­cled by vapother­mol­y­sis (Mar­vapol) is also work­ing on the cre­ation of new prod­ucts to make the most of used tyres. “Vapother­mol­y­sis is a ther­mo­chem­i­cal sep­a­ra­tion process, on the bor­der­line between pyrol­y­sis and solvol­y­sis [editor’s note: a dis­so­lu­tion process using a sol­vent],” explains Ludovic Moulin. “We use super­heat­ed steam at ambi­ent pres­sure to sep­a­rate the rein­forc­ing fillers from the rub­ber.” What is the advan­tage of vapother­mol­y­sis? This sep­a­ra­tion process pro­duces recy­cled car­bon black with dif­fer­ent prop­er­ties that are of inter­est to man­u­fac­tur­ers. “The out­put oil is also recov­ered as a mate­r­i­al, a prod­uct that is now of inter­est to the chem­i­cal indus­try,” com­ments Ludovic Moulin. A pletho­ra of pos­si­bil­i­ties are open­ing up for tyre recy­cling in the future.

Anaïs Marechal