Comprehensive Use of Waste Rubber in a Scientific and Orderly Manner by Classified Treatment and Echelon Utilization
Click:7    DateTime:Mar.10,2022

Qi Xuezhi, Zhou Hong, Liu Jiahong

The central government was attaching more and more importance to the development of circular economy in 2021, as the requirements of Carbon Neutrality and Carbon Peaking were specified more clearly. Recently, the National Development and Reform Commission sought for public opinions on the amendment of the circular economy law, reflecting that the country is highly bracing for the work of circular economy under new conditions. It is foreseeable that the circular economy industry will be endowed with deeper connotation and more significance in strategic position as well. In response, the Scrap Rubber Comprehensive Utilization Branch of China Rubber Industry Association extensively solicited opinions and then regulated that the waste rubber industry should carry out classified treatment and echelon utilization so as to make the production process clean and environmentally friendly as well as the adopted materials safe and green. To be specific, the reuse of rubber powder and reclaimed rubber should be encouraged, tire retreading should be reduced, and thermal cracking should be regarded as a final harmless guaranteed process. China's rubber circular economy should adhere to ageneral development route of "giving priority to waste reduction and recycling, while having harmless treatment as a bottom line".

After years of development, China's rubber products industry has been significantly expanded, consisting of tires, hand cart tires, rubber hose tapes, rubber wares, rubber shoes, latex, etc. By 2020, China's rubber industry contributed an output value of more than RMB2 trillion and the rubber products were widely applied in automobile, mining industry and daily necessities. Nowadays, the concept of waste rubber is a combination of waste tires and various scrapped and replaced rubber products. Thus, the rubber recycling issue is not only about waste tires, but a whole rubber recycling industry covering all rubber products.

Despite a growing number of waste rubber categories, China's waste rubber comprehensive utilization industry keeps classifying them into four key types - vulcanized rubber powder, reclaimed rubber, tire retreading and thermal cracking.

Waste rubber, including waste tires, should be treated in different ways because of the difference in products and material composition. Tires of trucks and passenger cars above 9.00 (section width, inches, the same below) have long been the main raw material for the production of rubber powder and reclaimed rubber because their rubber content is high and the main component is natural rubber. The ties of passenger cars below 9.00 cannot be well used as the raw material of reclaimed rubber because the rubber content is relatively small and the composition is relatively complex with synthetic rubber as the main component. At present, rubber wares, such as conveyer belt, hand car tire, rubber shoes, rubber gloves and a variety of sealing strips, are difficult to be recovered due to their complex composition. Thus, adopting harmless bottom-line treatment while prioritizing resources should be implemented to achievethe thorough and complete recycling of the rubber industry.

Tire retreading to be reduced

Tire retreading is one of the comprehensive utilization and treatment methods of waste rubber encouraged by the government. However, it has been decreasing in recent years as affected by the policies of controlling vehicle overload and overspeed. The capacity utilization rate of most tire retreading enterprises is not high. In 2020, the rate even retreated in the light of the epidemic.

According to the current market situation, the sales proportion of retreaded tires is very small, as tire retreading enterprises mainly sign cooperation agreements with large mining and transportation companies for the retreading business of tires, most of which are truck tires. It is a usual thing that the carcass of off-the-road tires is seriously damaged, so the scrap rate is high. Inface of it, big enterprises prefer to use old tires of famous brands for retreading so as to ensure the quality of products.

Today, there are two production processes in China: pre vulcanization process and molding process. More and more enterprises adopt the former, as it is featured with high production efficiency, low single tire energy consumption and good wear resistance. The process has been widely used in our country.

The reuse of rubber powder and reclaimed rubber to be encouraged

The use of rubber powder and reclaimed rubber should be encouraged in China, according to China’s national conditions. Geographically speaking, China's natural rubber production is largely concentrated in Hainan, Guangdong and Guangxi, but the output is far from meeting the needs of the domestic rubber industry. The output of synthetic rubber was 7.398 million tons in 2020, up by 0.5% year on year. The imported natural rubber and synthetic rubber (including latex) totaled 7.468 million tons in 2020, an increase of 13.6% versus 6.572 million tons in 2019. In 2020, the output of natural rubber was only 693 000 tons in China, which indicated that the self-sufficiency rate was too low to meet the needs of China's rubber industry.

In 2012, reclaimed rubber, together with synthetic rubber and natural rubber, was listed as three strategic resources in the rubber industry by the Ministry of Industry and Information Technology. Reclaimed rubber takes a crucial position in China's rubber industry and is widely used in the production of various rubber products, such as tires, hand cart tires, rubber hose tapes, rubber shoes, rubber products, and waterproof coiled materials. More than 70% of the world's reclaimed rubber output is from China and Chinese reclaimed rubber producers are settled in all over China's provinces, cities and autonomous regions, except Macao and Hong Kong. Following the continuously improving production mode, the direct application of rubber powder is drawing more and more attention. In addition to being used to produce reclaimed rubber, rubber powder is applied in the production of waterproof coiled materials, highway asphalt modification and some rubber products.

According to rough statistics, China’s reclaimed rubber output reached 4.6 million tons in 2020, flat with the previous year. With rubber powder as the raw material of reclaimed rubber, 4.2 million tons of rubber powder were required for 4.6 million tons of reclaimed rubber. This, together with 850 000 tons of directly applied rubber powder, led to 5.05 million tons of rubber powder output in total. Table 1 shows the output of rubber powder, reclaimed rubber and waste tires in China from 2014 to 2020.

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In 2021, especially in the second half of the year, the supply of waste tires became tight in line with a rapid increase in the prices of waste tires, causing many reclaimed rubber manufacturers to halt production, particularly in Jiangxi, Shanxi, Hebei, and Shandong. If the situation continues, the development of reclaimed rubber industry will be significantly hampered. The ongoing plant shutdowns will even seriously affect the whole rubber industry, further push up the prices of natural rubber, and weaken the competitive edge of China's rubber industry eventually.

Thermal cracking to be regarded as harmless bottom line

Thermal cracking is one of the comprehensive utilization and treatment methods of waste rubber in China. It is regarded as the bottom line of harmless treatment.

There has been a wave of investments in thermal cracking since 2019. According to information disclosure, the capacity of thermal cracking investment projects publicly unveiled has reached whopping 3.1 million tons since 2019. Based on the source data of waste tires, the domestic output of waste tires in 2020 was 13.9 million tons, including nearly 10 million tons of truck tires and the rest 3.9 million tons of passenger car tires.

Therefore, the thermal cracking projects with huge production capacity will be definitely stuck with the problem of insufficient raw materials, especially the shortage of passenger car waste tires. The supply of raw materials is far from meeting the existing capacity of thermal cracking, even with 3.5 million tons of other scrapped rubber products such as tires and rubber shoes counted in. Correspondingly, the prices of waste tires have increased significantly since 2019. The prices of waste tires above 9.00 were RMB800/ton in 2019, and the prices in some areas reached RMB1 560/ton in October 2021, according to the latest data of the Association, which nearly doubled the former. The prices of small vehicle tires also rose from RMB400/ton to RMB1 200/ton. As a result, there were buying sprees of waste tires in some regional markets, and a number of reclaimed rubber manufacturers were struggling to survive.

New trend from 2020

There has been new trend in the industry since 2020, that is, although the vehicle holdings keep increasing, the yield of waste rubber has been falling from a peak since 2020. Tires of truck and passenger cars are the main sources of waste tires, but with the emergence of more wear-resistant tires and the implementation of highway overload control, the scrap cycle of truck tires has been extended from 7-9 months in 2019 to more than one year by now. The Association estimated that the production of waste tires in China decreased by about 600 000 tons in 2020.

The lower yield of waste tires further exacerbated the conflict between the supply of thermal cracking and reclaimed rubber manufacturers. Some thermal cracking manufacturers began to use a big number of truck tires for cracking because they did not have sufficient raw materials, which wasted valuable rubber resources and pushed up the prices of waste tires as well. More seriously, with a rapid rise in the prices of electricity and coal from October 2021, some power generation factories added rubber powder to coal, but most of the added rubber powder was directly from tire rubber powder above 9.00, which not only caused significant waste in valuable rubber resources, but also exerted new pressure on environmental protection. This situation is not conducive to the healthy development of the industry.

To avoid wasting by comprehensive utilization in a scientific way

In a nutshell, China's waste rubber industry should avoid waste of resources, blind investment, environmental pollution and disorderly competition in the comprehensive utilization of waste rubber. Enterprises should adhere to classified treatment and echelon utilization, attach importance to a general development route of "giving priority to waste reduction and recycling, while having harmless treatment as a bottom line". They should maximize the resource utilization of rubber and realize high-value utilization, so they can not only solve the problem of black waste generated by waste rubber, but also complete scientific recycling of rubber resources so as to save resources and reduce carbon emission.