Low-density Polyethylene (LDPE) and Linear Low-density Polyethylene (LLDPE) Agricultural Waste Trial
The aim of this particular trial is to demonstrate the use of recycled LDPE and LLDPE – derived from agricultural film, such as crop cover and silage wrap – in the manufacture of rotationally moulded products. Examples of products manufactured via rotational moulding include outdoor bins and traffic management cones, which are traditionally produced using virgin high-density polyethylene (HDPE).
At present, there are very few markets for recycled agricultural film and there is a maximum value that it can achieve, which makes recycling uneconomical. However, by accessing another end market, it may mean a higher value can be realised.
The objective of this project is to demonstrate the successful incorporation of as much recycled LDPE and LLDPE film as technically possible, in a bid to encourage other rotational moulders to reduce their reliance on virgin polymer. This will drive demand for recycled agricultural film in Wales and contribute to the Welsh circular economy.
Trial partners include: Axion Recycling Ltd (lead partner); B&J Parr; Crompton Mouldings Ltd; and MDS Recycling Ltd.
Progress update (August 2020) – valuable insights gained from an ambitious first trial
The aim of this trial was to incorporate as much recycled LDPE and LLDPE, recovered from agricultural film, as possible into products produced using rotational moulding. Products manufactured using rotational moulding are commonly hard-wearing, durable plastics. Incorporating a significant proportion of recycled agricultural film is challenging due to the level of contamination, characteristics of LDPE and the technical specifications that the new products must meet.
One tonne of material, comprised of 50% crop cover (made from LDPE) and 50% silage wrap (made from LLDPE), was pre-washed to reduce contamination levels and then reprocessed. Despite technical challenges with milling different grades of recycled polymer, the LDPE / LLDPE blend was successfully transformed into an 800 µm powder of suitable quality for use in the rotational moulding process.
Our environmental assessment revealed that the estimated carbon emissions associated with this recycled material stand at just 20% compared to virgin polymer. Whilst an economic assessment showed that recycled polymers could provide a cost-effective alternative.
The powder was used to manufacture a product made of 100% recycled content. However, its surface was rough and pitted with ‘pin holes’. The reason is believed to be the low Melt Flow Index (MFI) of the molten polyethylene (PE) – it was too viscous to flow evenly into the mould.
Despite the 100% recycled content not meeting the product specifications, this ambitious trial has provided valuable insights. The successful milling of the recycled PE and the positive environmental and economic benefits of using it warrant further investigation. As a next step, we plan to test a blend of recycled and virgin PE powders to increase the MFI. Our aim will be to demonstrate that a suitable product can be produced using at least 20% of the recycled powder, which would still represent a cost-saving to the moulder and reduce the carbon footprint of the product.
Further supply chain demonstration projects
In total, WRAP Cymru has embarked upon four projects to demonstrate the environmental and economic case for the use of recycled content in manufacturing. For information regarding the other three trials, please use the following links: