Pollution from tyre debris
By TA News Bureau:
Amid the debate in India on switching to an all-electric car fleet by 2030 to cut pollution and wean the country away from petroleum, a technologist and industry consultant is urging the need to curb pollution from tyre debris and landfills for end-of-life tyres. Dr SN Chakravarty, who initiated a debate on the environmentalimpact of tyre use at the Bureau of Indian Standards’ (BIS) committee dealing with pneumatic tyres (BIS TED7), says appropriate action on this issue are very much in needed. Rubber loss, which includes debris and particles that get released into the environment, caused by tyre wear has detrimental environment impact. Moreover, the tyre industry should publically share data such as tyre size, weight, pattern, ply rating and non-skid depth for calculating the quantum of rubber loss for different categories of tyres in order to analyse more accurately rubber loss impact on the environment
When Dr SN Chakravarty raised the issue of tyre pollution at a specialised committee meeting of Bureau of Indian Standards, he was prompted by concerns about the negative impact on the environment of rising rubber losses from tyres as the country’sautomobile population gallops.
Dr Chakravarty, a well-known industry consultant and polymer scientist, recently initiated a debate on the environmental impact of tyre use at the Bureau of Indian Standards’ (BIS) committee dealing with pneumatic tyres (BIS TED7) .
He says appropriate action on this issue are very much needed and standardisation measures should be taken by the government. Rubber loss, which includes debris and particles that get released into the environment, is caused by tyre wear leading to environmental hazards.
Moreover, he feels the tyre industry should publically share data such as tyre size, weight, pattern, ply rating and non-skid depth for calculating the quantum of rubber loss for different categories of tyres in order to analyse the true impact on the environment.
He is optimistic that the government, which is pushing electrification of the automotive sector, would also look into the tyre issue and develop effective regulatory norms and standards similar to those in vogue in the European Union and the parameters recommended by United Nations Economic Commission for Europe (UNECE).
While giving a perspective on the impact of tyre usage on the environment, he said BIS TED7 is considering these issues.
“During drive, the tyre abrades,” he said adding that the Non Skid Depth (NSD) reduces to a point when the tyre is no safer to drive due to different factors. “This NSD varies strongly, depending on the tyre size and type and its application.”
The question is where do the worn tyre material goes when the tyre abrades and NSD gets reduced? “Obviously to the atmosphere. Rubbers and chemical particles flowin the air. It is this particulate matter which we inhale,” he warns.
In this context one has to remember that many such petro-products are restricted under European Union regulation called REACH – Registration, Evaluation, Authorisation and Restriction of Chemicals – and other laws.
These are taken care of by the technologists who produce tyres in compliance with these regulations. In India similar regulations need to be in place, a subject that Dr Chakravarty presented in the BISTED 7.
It is the tread of the tyre that wears. It is made of rubbers, reinforcing agents (fillers such as carbon black, silica), process oils, chemicals(zinc oxide, stearic acid, and accelerators), sulphonamides,thiurams, diphenylguainidine, mercaptobenzo thiazol derivatives etc.
Tread also contains antioxidants and antiozonants – mostly p-phenylene diamine and quinoline derivatives, bonding agents – resorcinol products /cobalt naphthenate etc.), and waxes. These, except silica and zinc oxide, are all petro-products.
While running, the tyre goes through millions of cycles of compression and deflection (hysteresis). The tyre heats up (mechanical energy converted to heat energy). The heat acts as an accelerating factor for the oxidative degradation (ageing) of rubber used in the tyre and it increases the abrasion of tread.
Dr Chakravarty says all these have adverse environmental impact. As there are many types of tyres, many key data are not available in public domain for experts to make accurate calculations. Hence, one has to go for approximation by taking the “average” value for each category of the tyre.
Despite the handicap of not having comprehensive data, Dr Chakravarty has made an attempt to figure out the rubber/chemicals particles in the atmosphere. Based on the data of 127.34 million tyres produced in India in 2016-17, he reckons that 60% tyres have ended up at landfill sites or got incinerated.
The ‘bubble’ effect has the potential to damage to the landfill liners that are installed to help keep landfill contaminants in check, thus leading to a higher probability of pollution not just in the ground surface but also the groundwater.
Technology has to be extensively employed if India wants environmental solutions to manage its landfill sites and control air and land pollution. Burning of rubber results in the emission of carcinogenic pollutants, such as polycyclic aromatic hydrocarbon, dioxin, furans and oxides of nitrogen, which are extremely hazardous to the environment and human health.
Tyre wear that occurs during driving results in particulate matter getting released into the environment, mostly chemicals and sulphur (free sulphur in vulcanized rubber as all sulphur of the compound does not crosslink or get chemically bound with RHC).
These particulate matters may react with atmospheric oxygen to produce CO, CO2, NOx, SO2 which in turn may react with moisture in the atmosphere to produce acidic material. All these are detrimental to human health.
Tyre is also exposed to weather wherein ozone and humidity are present which can react with the rubber particles, first forming ozonide which gets hydrolysed by the humidity present generating acids. As is well known all the sulphur added in the compound does not go into the chemical reaction (cross link) and free sulphur is always present in vulcanised rubber which can be extracted. These could be then detrimental to the environment.
Simple calculation shows 6756.83 MTof rubber material (without tractor tyre and OTR) is going to the atmosphere in a timeframe which is again not very clear. Some tyres are abraded in a short time (say 6 months) while others take longer from one to three years. A large part of bias tyres isretreaded / recapped and the balance of other tyres, both bias and radial, are used for producing reclaim rubber, subjected to incinerator, land filling etc.
It is suggested that further studies on these types particulate matters are carried out to understand the environment pollution aspect. Only then can India take corrective measures with the involvement of rubber and tyre technologist.
“For such studies rubber and tyre industries should collaborate with elite institutions such as the Indian Institutes of Technology,” Dr Chakravarty said. The situation warrants urgent action by the government and the tyre and rubber industry.