Oil from old computers

Printed circuit boards from old computers and other electronic equipment could provide a new hydrocarbon feedstock for the petrochemical industry, according to European researchers.

Anyone who has worked with computers for more than a year or two will be all to familiar with the crushing pressures to upgrade software for more bells and whistles, improved security, and other factors. Of course, the new versions of operating systems, applications, and security software usually require a more powerful computer to operate at full speed and so there is pressure from two sides - hardware and software. Conversely, with Moore's Law still telling us of the doubling of computer power every year and a half, there is the pressure to upgrade hardware to make even the older software perform faster.

All this upgrading stacks up to an enormous waste of discarded computer parts, monitors, circuit boards, hard drives, keyboards and mice, which rarely make it to re-use centres. Even if there were a mere 20 million computers in the UK and users were upgrading their complete setup only once every five years, that means on average 4 million computers to dispose of every year. Add to that, business computing waste, broken down gadgets and unfashionable mobile phones discarded for simply being the wrong shape or size and one can see a huge waste stream just waiting to be tapped.

However, such a homogenous mountain of electronic waste is difficult to recycle because of the multifarious materials and elements contained within. Now, researchers in Romania and Turkey have developed a simple, efficient method for recycling printed circuit boards into raw materials for use in fuel, plastics manufacture, and other useful consumer products. The team uses various analytical techniques, including Fourier transform infrared and nuclear magnetic resonance spectroscopy to track the progress of the reclamation process as well as atomic absorption spectroscopy to test for toxic heavy metal content in the raw "oil".

C. Vasile, M. A. Brebu, M. Totolin, and H. Darie of the Romanian Academy, "Petru Poni" Institute of Macromolecular Chemistry, Department of Physical Chemistry of Polymers, in Iasi, Romania, working with fellow chemists J. Yanik and T. Karayildirim at Ege University, in Izmir, Turkey, have found that their approach removes almost all toxic components from the retrieved oil, which could then safely be used as feedstock for various industries.

"Plastic waste is one of the major problems facing the consumer societies of Europe, Japan, and North America," explain the researchers. Waste electrical and electronic equipment, WEEE, directives in the European Union and legislation elsewhere are forcing manufacturers and consumers alike to use alternatives to landfill or other waste disposal for electronic goods. Indeed, the European Commission's WEEE directive, requires that all such goods are collected separately from domestic and other waste and that each type of material, plastics, metals, and composites be separated and recycled.

The researchers point out that degradation using pyrolysis has become of increasing interest for retrieving useful materials from waste streams without generating high levels of pollutants associated with simply burning them for disposal. However, the plastic fraction of WEEE remains particularly problematic in terms of recycling, partly because of the wide range of polymer types used in the manufacture of different devices. Thermoplastics, such as acrylonitrile-butadiene-styrene (ABS), high-impact polystyrene (HIPS), and polycarbonate (PC) polymers are used for casings, for example, while thermoset plastics, epoxy resins, are a major component of the printed circuit boards on which the functionality of myriad devices rests.

Moreover, those hoping to recycle WEEE also have to cope with dozens of different additives such as toxic heavy metals, including cadmium, chromium, lead, and mercury, used in batteries, circuitry, and other components. WEEE may also contain halogenated flame retardants, such as polybrominated compounds like polybrominated diphenyl ethers or tetrabromobisphenol A. These all represent significant environment pollutants that must be dealt with diligently.

Previous researchers have investigated pyrolysis of epoxy resins as a means to recycling these materials. Various additives and catalysts have been tested, some are relatively efficient, others cause severe charring, while the release of extremely toxic flame retardants remains a significant obstacle.

Vasile and colleagues have now experimented with a new approach to pyrolysis that allows them to upgrade the resulting pyrolysis oils to hydrogenated materials. In their latest study, published in May 2008, they have focused on the degradation of waste printed circuit boards using coupled thermal, catalytic, and dehalogenation (absorption) procedures. The ultimate aim is to obtain pyrolysis products with low amounts of heteroatoms (bromine, chlorine, nitrogen, or oxygen. The resulting oils would essentially represent a synthetic hydrocarbon feedstock not dissimilar to crude petroleum oil, that might be processed further by the petrochemical industry.