What's That Smell? — Chromatography Helps Neutralise Recycled Plastics

Most people will be familiar with all the different bins we know need to put outside on ‘bin-day’. In the last twenty years or so, households in the UK have separate bins for recycled and non-recycled waste — the exact bin make-up varies between local authorities as recycling policies differ. And the introduction of environmental standards — such as ISO14000 — has seen enlightened manufacturers increase the amount of material sent for recycling. But recycling can be a smelly business — especially for some plastics. A recent press release from the Austrian company Starlinger & Co. GmbH, highlights how the industry is addressing the issue — and chromatography plays a role.

Mountains of plastic

The EU has set a target for UK households to recycle 50 per cent of waste by 2020, with the UK setting a recycling target for plastics of 57% by 2020. In recent years, the amount of plastic collected for recycling is around around 500,000 tonnes. The quantities are growing slowly — but with plenty of room for growth.

Recycle Now — the national recycling campaign for England estimates that each UK household uses 480 plastic bottles per year, but only recycles 270 of them — meaning almost 16 million plastic bottles are not recycled each year in the UK. But even if we did recycle all our bottles — until recently, not all of them could be reused.

What’s that smell?

Some plastic bottles take on the odour of their contents. And this is bad news for bottle recycling plants. Bottles made from some types of polyolefins can acquire the smells of whatever they contained — food, cosmetics, cleaners and washing-up liquids can all impart their odours to some plastics. And during the recycling process, these create smelly recycled plastics that cannot be used for certain applications. Would you want your fabric conditioner to smell of pine disinfectant?

The Austrian company Starlinger has developed a three-stage process to help eliminate odour from plastics. The stages include:

• Material preparation — the plastic is heated and mixed, volatile odours extracted.
• Degassing — the surface area is increased allowing efficient degassing and permanent exclusion of odours.
• Post-treatment — post-granulation, and the final extraction unit removes the most persistent odours.

Chromatography and a nose — perfect harmony

The development of the process was helped by gas chromatography — and the human nose, with GC used to analyse the odours emitted as the process was developed. The use of gas chromatography to analyse volatile samples is discussed in the article, A New Method for Fast Residual Solvents Analysis and Untargeted Unknown Identification. Faster Sample Throughput and Shorter GC Runtimes Using GC-VUV and Static Headspace.

With the process they have developed, Starlinger’s technology means that more plastic can be reused — which is good news for plastic recyclers, consumers and the environment as more recycling means less use of natural resources.

So, thanks to chromatography, a nose and some smart Austrian technology — plastic recycling can nose ahead of the game.