Prospecting the Vulcan Hills for Treasure

NewScientist
Until relatively recently, most used rubber vehicular tyres were buried in landfills and left to slowly rot. But now there are dozens of productive uses to which these rings of vulcanised rubber can be put. A better way of making steel is only one of them:

To conventionally make steel, coke, which is charcoal from coal, and limestone are shoved into a furnace heated to more than 1500º Celsius. The calcium in the limestone scavenges impure elements in the coke, such as silicon and aluminium, creating foamy slag and the product we're after - liquid iron. Just like cappuccino foam, the slag sits atop the liquid iron and insulates it, speeding up the processes of converting coke to iron.

Sahajwalla found that replacing some of the coke with recycled rubber created a more effective slag blanket. The extra heat produced from it reduced energy consumption, and produced more steel. It was the ultimate win-win. Following successful commercial trials in 2007, the technology is now being used in steel mills across Australia and has diverted well over 70,000 tyres from landfill. "It's so satisfying and so exciting," she said. _NS

Another intriguing use for old rubber tyres is to produce carborundum -- silicon carbide -- for tough bits, blades, and tools.

Silicon carbide, known commercially as carborundum, is formed of carbon and silicon atoms arranged in a diamond-like pattern, which results in diamond-like properties. On the Mohs scale of mineral hardness, which has diamond as ten, carborundum scores nine or better. It thus has a wide range of uses, from abrasives and cutting tools to bullet-proof vests and ceramic brakes in sports cars. It is also used as a semiconductor in high-voltage applications.

Normally, silicon carbide is produced by heating sand (which is made of quartz, or silicon dioxide) in an electric furnace with carbon made from oil or coal. The trick used at Tubitak is to get both the carbon and the energy from tyres.

First, the tyres are gasified, a process which is similar to burning but involves less oxygen. This releases a mixture of hydrogen and carbon monoxide, known as syngas, and leaves a residue of amorphous elemental carbon called carbon black. Tyres also contain sulphur, which is added as part of the process of vulcanisation that makes rubber into a suitably resilient material. Gasification liberates this in its elemental form, making it easy to recover. Burning a tyre, by contrast, produces sulphur dioxide, a noxious pollutant.

The carbon black is then mixed with sand and the mixture is heated to between 1,400ºC and 2,100ºC in a syngas-fired oven. The result is high-grade silicon carbide. _Economist

Tyres can also be used to produce valuable oils, carbon black for making more tyres (as reinforcement), and to generate electricity, via pyrolysis.

[Besides re-treading,] Other common uses for scrap tyres include sports and recreational surfaces, landfill engineering, carpet underlay/floor coverings, and road building. Roads manufactured using crumb rubber last longer, have better traction and reduce noise. _Source

Tyres can also be used as structural members when baled, or formed into special block structures.

One can build entire houses and other structures out of used tyres, using the "Earthship" method, the tire bale method, or other creative methods of recycling.

And of course there are always the tyre swing, tyre planters, concrete-filled tyres used as bases for upright poles, rubber sandals made from tyres, and many other commonplace home and hobby uses for worn-out tyres.

The basic point being made is that new and important uses are being found for what was once viewed as trash and environmental hazards. That is where the attention of environmentalists, Greens, activists, and concerned citizens should be focused. Toward innovations which turn the trash into treasure.

Turning Garbage into Treasure -- Human Imagination

Burning tires is like burning money, say executives at RTI Cryogenics, a company that designs and sells equipment and systems that help turn old rubber into cash.

...The Cambridge company installs technology that freezes old tires into a glasslike substance and breaks down that substance into a fine mesh or powder. It also has patent-pending technology that blends rubber with recycled plastic, to turn it into a thermoplastic elastomer that can be used in injection moulding machines. _TheRecord

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Hundreds of millions of scrap tires per year are discarded in the US alone, many of them stockpiled, buried in landfills, or simply incinerated. But entire industries are growing up for the purpose of turning discarded tires into useful, high-value economic products.

In pyrolysis waste to energy technology all of the steel from the tires will be recovered and resold in the recyclables marketplace, slightly lessening our need to import steel. There are approximately three pounds of steel per passenger tire. In California then, the 18 million waste tires generated every year would produce approximately 26,000 tons of steel, with the current rate for recycled steel at about $250 per ton.

With a continuous feed of tires, the 5 to 10 percent carbon char that is generated by a pyrolysis waste to energy system has a myriad of practical uses. The char can be sold to manufacturers to produce many commonly used products. Once again we note that using this technology we not only generate electricity and valuable commodities, but we have nothing left over to go to the landfill – zero waste. _Examiner

Old tires can be turned into liquid fuels, gaseous fuels, electricity, plastics, fertilisers, and much more.

Novo Energies has been granted a worldwide exclusive license to use Precision’s proprietary gasification technology to convert plastic and tire waste into energy products including electricity, synthesis gases and other valuable commodities such as recovered steel.

...Antonio Treminio, CEO and chairman of Novo Energies, stated, “In our search for the most efficient and economical methods to convert plastic and used tires into valuable energy products, we have spent the last 12 months evaluating several technologies, including pyrolysis, gasification and microwave based systems. As a result of such efforts, we have selected Precision’s gasification technology based on the following:

1. 
   Allows efficient conversion of tires and plastic feedstock to energy.
2. 
   Environmentally friendly – the process produces zero toxic emissions, making it a green energy technology.
3. 
   The preliminary synthesis gas resulting from conversion of tires and plastic meets strict standards on quality and consistency.
4. 
   Has the highest carbon conversion of any known gasification system on the market.
5. 
   Self sufficient by using the produced syngas to power the process.
6. 
   Low cost of production.

Novo plans to demonstrate the pilot facility in Denver, Colorado, as a showcase unit for government officials, institutions, utility companies and the investment community, as well as augment its output to reach fully commercial quantities. _AmericanRecycler

Here are more innovative uses for scrap tires:

Highway Sound Barriers -- Many states are turning to absorptive sound barriers—structures that soak up sound—to reduce highway noise. The "Whisper Wall" used in Northern Virginia, starts as a mixture of concrete aggregate, cement, water, and small pieces of shredded rubber from scrap tires. The wall deflects sound waves among its nooks and crannies until they lose energy.

Athletic and Recreational Applications -- Several brands of resilient playground rubber surfacing material are being made from recycled tires and sold at major retailers across the US The material can absorb much of the impact from falls providing added safety to children. This material can also be used as a mulch replacement in medians or decorative areas. Athletic and recreational applications are a fast growing market for ground rubber. An estimated 80 million pounds of scrap tire rubber were used in 2001 for athletic/field turf applications (50 million pounds)—above or below the ground—and as loose cover (30 million pounds).

Railroad Ties -- Highly durable, rubber-encased railroad ties are being produced using scrap tires. These railroad ties have a steel-beam core filled with concrete that is then encased in 80 pounds of ground-up scrap tires and discarded plastic bottles, held together with a special binder or glue. These railroad ties are over 200% stronger than creosote-soaked wooden ties, enabling railroads to use fewer ties per mile. Moreover, rubber-encased railroad ties could last 60 to 90 years versus 5 to 30 years for wood. _Source

Scrap Tire News

Problem-solving human imagination is in short supply these days, largely due to shoddy education, neglectful child-raising, and a culture that is focused on time-wasting entertainments and faux crises at the expense of raising generations of new problem-solvers. The human imagination has been referred to as The Ultimate Resource, and as The Mainspring of Human Progress (PDF). It is both of these and much more.

Empowered by language, it represents much of the difference between humans and apes, and between advanced societies and more primitive societies of humans. Those who can imagine ways of transforming garbage into treasure have much more of a future than those destined to drown in their own detritus.