|Stolen Copper wire from Australian train lines. (Source: Herald Sun/Bill Mcauley.)|
Metal Prices. As described by Kooi , high metals demand on the international market is a key driver leading to scrap metal theft. The prices of metals can change as fast as by the half-hour, reflecting the instantaneous updates of supply and demand. A number of companies (e.g. Kitco) monitor price fluctuations in common "base" metals (e.g. Aluminum, Copper, Lead, Nickel, Zinc) as well as the more precious or scarce metals (e.g. Gold, Silver, Platinum, Palladium, and Rhodium). Prices change quickly over even the course of a day: for example, earlier this month over an 18-hour span, the price of Copper ranged between $3.95 and $4.03 USD per pound, a non-trivial difference of 2%. Over a 30-day span the price of copper has ranged between $4.38 and $3.91 USD per pound, a difference of more than 10%. A quick look at the other metals listed above shows Copper is not the only metal with a rapidly fluctuating value.
Common Metal Forms. Many of the metal items targeted for theft are those in common and recognizable forms. Kooi  has reviewed many of these forms, illustrating a world-wide problem of metals stolen for scrap. (A Google search will find many more examples). Copper (and brass) is commonly stolen from a number of sources such as plumbing suppliers, construction sites, vacant luxury homes, cemetery headstones, fire hydrants, and even live electrical transformer stations. Telephone land lines, street lights, and traffic signals are also frequently cut for their Copper wiring.
Metal theft patterns changes with market prices: as Copper prices dropped mid-way last year, increasing theft of steel and Aluminum metals was reported . Steel is a frequent target for theft because it is common, simple, and easy to steal - as car frames, concrete re-bar, construction materials, beer kegs, manhole covers, assembled bridges, and even playground steel slides - then sold quickly at scrap value . Even railway tracks have been stolen, which are then cut down and sold as scrap. Aluminum is often stolen as castings from construction sites, car wheels, house siding, bike frames, and plumbing. But it is not only these easily identifiable, common forms which are targets for theft. The "scientific community should be on guard, too. Steel vacuum chambers, electrical cables, chilling units stuffed with copper and aluminum tubing, and other metal-laden laboratory accoutrements all look like money to metal thieves..." .
Scarce Metal Forms. The more scarce (and generally more valuable) metals are also targets for theft. Catalytic converters on cars, for example, are a key target which contain thin coatings of Platinum, Palladium, and Rhodium - which in 2008 were respectively valued at approximately $65, $15, and $290 per gram . While in a given catalytic converter there is not a considerable amount of these metals (a total mass in the range of ~3-7 grams depending on the converter), with increasing prices there is considerable financial motivation: converter recyclers will buy scrap converters at $70-$100 each . (Recently, Platinum in the form of jewelery has also become a common target for theft.)
Despite their value, not all metals are easy to sell. As described by Kooi , stolen Gold or Silver jewelery has intrinsic value and can be sold in scrap or melted form or in their original shape. In contrast, base metals Copper, Aluminum, brass, Zinc, Nickel, Platinum, etc. are generally not worth much (or not easy to sell) outside of scrap form; and so these metals are generally melted and re-shaped by scrap dealers or the thieves themselves. On the other hand, the valuable metals in catalytic converters reside on a porous ceramic substrate and can not be extracted for sale using simple methods. To extract the metals, the entire assemblies must be heated with the ceramic up to temperatures in excess of 1500 degrees Celsius, then further refined. The complexity of this refinement limits the number of buyers for stolen converters, most of whom are designated converter recycling depots.
Valuable metals used in electronics also fit into the category of difficulty in extraction and low theft return. However, with increasing volume of waste electronics, a correspondingly large volume of valuable metals become locked away. I previously wrote on this subject with respect to scarce metals: Japan's 'urban mines' contain approximately 6,800 tons of Gold (currently ~$48 per gram), 60,000 tons of Silver (~$1 per gram), and 1,700 tons of Indium (approaching ~$1 per gram). As the price of metals increase (and as the electronic device lifetime decreases), the value of electronic waste will become greater. For example, a U.S. Geological Survey 2006 report  estimates that an average cell phone (weight 113 grams) contains approximately $1 worth of Copper, Silver, Gold, Palladium, and Platinum combined. While this may appear to be a rather trivial amount, millions of cell phones are discarded annually. The overall reward is great enough for 'urban miners' to harvest, so thievery can't be far behind as metal prices increase.
Other Materials: Polymers and Ceramics
While metals have value in both product and raw form, polymers have a much smaller market for recycling or use as raw material outside of combustible fuel. One of the key reasons for this difference is the degradation of polymers with time and use. For example, the mechanical properties of many polymers (e.g. thermoplastics which can be melted and re-shaped or re-purposed) decrease with increasing number of re-cycles. This is due to breakdown of the polymer chains over time and limited "mix-ability" of polymers from different sources. Such breakdown is very different from metals, which can be recycled a far greater number of times - essentially infinite so long as alloy elements can be separated and oxides removed/reduced. In contrast, many polymers include additives which can not be easily separated from the base polymer, thus complicating recycling. A second reason, it requires much more energy to produce metals from mined or native sources (e.g. ore) than from recycled sources; in this way, metals more than polymers also have far greater value once in a usable form.
In a functional device, the value of polymeric parts is at its highest; the value also increases with the functionality of the part. For example, carbon fiber bicycle frames are high targets for theft, not because of the price of the carbon fiber but because its function as part of a light-weight frame enables a high immediate resale value. Another example, the polymer Dyneema is used in ballistic armor vests, among other applications. The polymer is an ultra-high molecular weight polyethylene, which has the same monomer unit as the polyethylene used in plastic shopping bags. The value in one form is clearly larger than that in the other; but unfortunately between the two recycle-ability is not equally directional.
Ceramic materials (e.g. granite, marble, diamond, etc.) also find themselves in the same category as the polymers and fibers: they are most valuable while providing functionality (and/or possessing immediate resale value in their current form), there are not considerable cost savings by producing from recycled sources, and the two-directional recycle-ability is limited.
Material Solutions to Theft
Solutions are required in order to identify stolen materials, but also to alert users and technicians of critical missing materials, e.g. power cables which can be hazardous if a circuit is incomplete. There have been a number of policy changes, regulatory agencies, and security measures adopted which have helped reduce the occurrence of thievery, e.g. . In the case of catalytic converters, additional measures have targeted supply chain bottlenecks (converter recycling depots) and thus reduce the success of selling stolen parts. Complimenting these strategies, below are some of the materials and engineering solutions which have been implemented in an effort to reduce materials theft.
Identification Labels. This is a truly fascinating field; and with novel Material Re-Design approaches below, I believe this represents the future of materials research and engineering in theft. A few examples commercially available are:
- One example, SmartWater  is a liquid-based solution which uniquely 'tags' targets (e.g. Copper wire), thereby allowing for exact detection of a stolen material under UV light. This coded liquid remains intact on the conductor jacket even if the wire insulation is burned . Spraying devices can also cover the offender in the liquid, which can't be easily removed or washed off.
- Another example, MicroDotDNA technology "consists of thousands of polyester substrate microdots, each the size of a grain of sand, onto which unique information is laser etched."
- Proof-positive Copper  uses laser-etching methods to add serial codes and reference numbers directly on copper wires; this method can provide information on the material's owner as well as installation location and date.
Mechanical Additions. Finally, a number of commercial products exist to help deter or slow theft of frequently-targeted materials. These include devices such as the Copper Keeper (to prevent theft of copper wires), as well as the Catlock and CatClamp (to prevent theft of catalytic converters). As outlined by Kooi , these devices enable better security for the materials but at a cost nearly equal to replacing them. And with increasing market prices for these sought-after metals, more sophisticated prevention approaches will be needed in the future.
Materials targeted for theft require a certain ease of identification and understanding of value; financial longevity, stability, and flexibility; omnipotence and malleability in shape and form; and so on. Metals find themselves with all these characteristics, and are thus the most frequent target for theft. But as explained above, all materials can be targets for theft if there is immediate resale value and if the thief understands the value of what is being stolen.
 B.R. Kooi. Theft of Scrap Metal. Problem-Oriented Guides for Police - Problem-Specific Guides Series, No. 58. U.S. Department of Justice, April 2010. ISBN: 978-1-935676-12-6. (Available On-Line.) Also see L. Bennett. Assets under attack: metal theft, the built environment, and the dark side of the global recycling market. Environmental Law & Management, Vol. 20 (2008), pp. 176-183. (Available On-Line.)
 J. Grimaldi. Thieves ditch copper for other metals. The Hamilton Spectator (Hamilton, Ontario), July 13, 2010, p. A03.
 Stealing metal, metal allergy. Chemical & Engineering News, Vol. 85, No. 46 (2009), p. 56.
 A. Tullo. The Catalyst Caper. Chemical & Engineering News, Vol. 82, No. 22 (2008), p. 32.
 Recycled Cell Phones - A Treasure Trove of Valuable Metals. U.S. Geological Survey, Fact Sheet 2006-3097 (July 2006). (Available On-Line.)
 BT launches nationwide campaign against cable theft; 'SmartWater' invisible paint deployed to 'tag' metal thieves. ENP Newswire, July 27, 2010.
 Proof positive Copper: SouthWire's solution to the Copper theft epidemic. Transmission & Distribution World, Vol. 62, No. 4 (2010), p. 18.
 S. El Haggar and L. El Hatow. Reinforcement of thermoplastic rejects in the production of manhole covers. Journal of Cleaner Production, Vol. 17 (2009), pp. 440-446.