See Part 1: https://steemit.com/science/@pinkspectre/catalytic-converters-life-cycle-analysis and check out https://steemit.com/science/@pinkspectre/rhodium for basic info on this element.


Platinum-group metals are scarce, especially rhodium. Even in South Africa, where it is found in highest abundance, its natural occurrence is only about 8 grams per ton of ore (1). As a result, the extraction processes necessitate huge amounts of energy and material resources. This power consumption has been estimated to be 110 Megajoules per catalytic converter produced (2). Since most electricity in South Africa is coal derived, this means ~11 kg of coal must be burned per catalytic converter produced. Coal burning emits significant amounts of carbon dioxide and sulfur dioxide pollutants. Although only 2 grams of platinum group elements are used in a typical catalytic converter, the scarcity of these elements means that it will become more difficult and energy-intensive to extract these metals from the earth in the future.

![coal.jpg](https://cdn.steemitimages.com/DQmYWdC6kPopgshv1jySstLcTpwZsuGjYQHeiuz5hnLqwrv/coal.jpg)South African Coal Plant, Gerhard Roux.<a href="https://commons.wikimedia.org/wiki/File:South_Africa-Mpumalanga-Middelburg-Arnot_Power_Station01.jpg">Wikimedia Commons</a>

The smelting and refining of the catalytic metals are also highly energy intensive. Often high temperatures of over 1000° Celsius are used, usually maintained through the burning fossil fuels (3). Substantial sulfur dioxide emissions are generated through the smelting process. Commonly the metal ore is treated with strong acids during the refining process, to remove more reactive impurities. Once removed, however, a slurry of toxic residue is left behind, with no practical means of disposal. Perhaps even more serious, the smelting process can melt and vaporize toxic compounds in the ore, including dioxin-related compounds which form during incomplete combustion in this stage (3). To ensure the complete capture of such harmful species requires better technology and greater expense.

Shipping and transportation are another factor in monitoring the environmental and economic costs of catalytic converter production. The refined ore is shipped to the factory for product assembly, then shipped to parts warehouses and auto assembly plants across the globe. A less obvious factor that must be considered is the effect of the catalytic converter on automobile performance. Sitting at the end of the exhaust pipe, the device creates significant back-pressure on the engine. To compensate for this pressure, as well as the additional weight of the catalytic converter on the the vehicle, additional gasoline must be burned: as much as 66 kg per unit over its functional life.  The increased gasoline consumption produces additional emissions of pollutants. With this added CO2 emission, a single catalytic converter is estimated to emit 390 kg carbon dioxide over its lifetime (2). Mechanical abrasion of the unit while driving also results in the emission of small particles of Rhodium, platinum and palladium. Though the particles are distributed at a rate of nanograms per kilometer, the biological impact should still be of some concern, as each unit on the road is estimated to lose as much as 3.2 mg of platinum-group metal particles over its life (4).

Although pure rhodium- a noble metal- is inert and non-toxic, many rhodium compounds are known to have toxic biological effects. Finely ground palladium can be pyrophoric; in other words, can burn spontaneously in air. Platinum salts may cause irritation of eyes, nose and throat; long-term exposure may cause respiratory and skin allergies (5).

The use of rhodium, platinum and palladium in catalytic converters have reduced smog and pollution levels but have increased emissions of global pollutants. Widespread use has exacerbated air, water and soil pollution problems in poorer parts of the world as well. Even though catalytic converters have a very high rate of recycling to reuse the metals, the dwindling supplies and environmental costs call for new alternatives to our hydrocarbon-based transportation system.



1. South African Government. Energy Sources, 1999. http:/www.southafrica.net/economy/resouces/sources.html
2. W Amatayakul. Life cycle assessment of a catalytic converter for passenger cars. Master's thesis. Gothenburg (Sweden): Chalmers University of Technology, March 1999.
3. C Lavin. *Catalytic COnverters: An Introduction to the Science and Environmental Concerns*, 2009. http://indian hillmediaworks.typepad.com/energy_matters/2009/06/catalytic-converters-an-introduction-to-the-science-and-environmental-concers.html
4. Wei C, Morrison GM. Platinum analysis and speciation in urban gullyots: the science of the total environment, 1994; 169-174.
5. E Sher. *Handbook of air pollution from internal combustion engines.* Pollutant formation and control, Academic Press (1998).