Single use paper cups are a common part of our day to day lives, with an estimated 1 billion being used in Australia every year. They may look recyclable, as they are made of paper, but many are lined with plastic to keep the cup from going soggy. The plastic lining prevents them from recycled, and as a result around 90% of these single use cups end up in land fill every year.
With increasing public awareness on the importance of recycling, biodegradable alternatives to the traditional plastics used in everyday life are becoming more prevalent. While most single use paper cups are still lined in polyethylene (plastic), biodegradable alternatives are starting to become more common in our local coffee shops.
Polyethylene is a non-biodegradable plastic. Polyethylene is one of the most used plastics in the world today.
Polylactide is a biodegradable biopolymer made from corn starch. Given its high abundance and low cost, it is one of the more popular bio alternatives to plastics.
To confirm whether the single use paper cups have correct labels on whether they are recyclable or not, Portable Spectral Services analysed eight single use paper cups from local coffee shops using FTIR spectroscopy to determine whether a plastic or biodegradable polylactide lining was being used. FTIR stands for Fourier Transform InfraRed and is a commonly used technique for identifying materials. It generates a spectrum that can be matched against a reference library of known materials for identification.
Bruker Alpha II benchtop FTIR with ATR sampling mode (pictured below)
The cup linings were analysed using the Bruker Alpha II benchtop FTIR instrument. The cup lining material was identified by spectral matching, using a comprehensive reference library (Table 1). Three of the cup linings were identified as biodegradable polylactide (Fig. 3), while the remaining five were identified as the plastic polyethylene (Fig. 4).
Correct labelling had been used and all cups that were identified as biodegradable had the correct polylactide lining. The use of biodegradable linings does not impact the quality of the cup or the drink within, and so the ability to substitute a non-recyclable plastic for a more environmentally friendly biodegradable material is a great alterative option.