The key to recycling is effectively separating waste into categories of materials that can be efficiently reused. The current trend is for most of this sorting to be done by householders and local recycling centers – more and more cities and communities provide multiple bins for different categories of waste, and dumps sort through garbage to extract anything that has residual value. The problem is the process isn’t all that efficient and a large amount of waste still goes to landfill. That doesn’t just take up landfill space – pollution can leak out of buried waste for years, damaging the soil and contaminating ground water.
One of the biggest sources of inefficiency is imperfect separation – paper and card bins often contain quantities of plastic from packaging, and can be soaked with food waste too. This limits their recycling potential unless they’re resorted. Conventional sorting procedures often miss small items made from recyclable materials, and millions of small items every day quickly adds up. There are some materials that nobody has even found a way to recycle yet, including concrete – and millions of tons of building rubble are collected every year.
Now German engineering company Fraunhofer is looking at a new way to recycle that could make the process far more efficient and reduce the flood going to landfill to a trickle. Innovative technologies break down waste to the smallest possible unit for separation; its component molecules. Ultimately all waste is made of chemical compounds and with the right equipment it’s possible to sort it at that level.
One problem with conventional recycling is that high grade materials are effectively reduced to lower grade ones in the process. Glass, for example, comes in many grades. Discarded consumer electronics increasingly contain high-grade glass in components like screens, sensors and even optical fiber, but this often gets mixed with lower grade glass used in windows, light bulbs and bottles. The difference is purity – lower grades, and colored glass, contain higher levels of metals and other minerals. Fraunhofer have developed a technique to extract iron atoms from molten glass, actually allowing them to turn glass waste into a higher grade than it started out.
A lot of waste contains large amounts of metal in the form of salts, and currently that mostly goes to landfill. Now it’s possible to use microorganisms to extract these salts from the waste and separate them, allowing the metal to be chemically extracted. The concentrations of recovered metal are low but with huge quantities of waste involved it’s becoming economical to do this. A bonus of this method is that waste which can’t be recycled at the moment – such as wood that’s been treated with preservatives – becomes reusable once the potentially toxic chemicals have been removed from it and reprocessed.
Concrete rubble is a difficult material to process but Fraunhofer have developed a technique that pulverizes it using high-energy electrical arcs. This process separates out the various ingredients of the concrete, some of which can be recovered. For example the gravel content can be reused once the surrounding cement has been removed, and in the future it may even be possible to recover the sand and cement.
Finally there are options for scavenging materials from waste that goes to the incinerator. Much of the mass of incinerated waste is released as smoke, and specialized filters can extract several valuable metals including germanium, zinc and phosphorous.
Not all of these advanced techniques are ready for commercial use yet, but some would be viable now and others will be in the near future. Current recycling methods are a good start but too many scarce resources are still being buried in dumps. If technology can be harnessed to increase the percentage of waste that gets reused that could make an enormous difference.