Recycling is now an important part of our economy. Today not only is recycling an important source of material for the production of consumer goods, but it also protects the environment and can save energy. But unlike paper or glass, plastic has been a notorious exception. Most plastics in use are not biodegradable, and therefore can cause permanent damage to the environment. The difficulty and expense of recycling plastic into other products is also a barrier.
However, the non-biodegradable nature of plastic can be an asset as structural material that has to resist decay, such as building materials and road covers. Alessandro Marseglia, an engineer at CETMA in Brindisi, Italy, tells us why.
Your company, CETMA is the holder of a patent in the reuse of plastic waste into concrete. What is new in your approach?
The novelty is that the recycled plastic expands in an extruder by adding gypsum to it. This works in a similar way to adding baking powder to a cake mix. From an initial recycling product, densified flakes, we create expanded nodules and obtain a material similar to the expanded clay that is added to structural concrete. Such concrete has some interesting advantages as a construction material: it is a good thermal and acoustic insulator, and it is lighter.
And what about the mechanical strength of these materials?
As a supporting structure, it is weaker than conventional concrete. But there are applications where mechanical strength is less important, such as inside partitions or wall coverings. It is also suitable as a material for road surfaces.
Is there interest in this material from industry?
Yes, we are in what I call the "explanation" stage, and we are dealing with a large cement manufacturer in Italy. We have several samples that are now being tested in a laboratory.
Will this material be able to compete with conventional materials on the market?
Yes, at the moment we are 30 percent cheaper than our competitors and there is interest in our business model. If a company buys our licence, invests about 1.1 million Euro in equipment and produces 5000 tonnes of the concrete per year, it will make a profit. The return on investment will be about 7 percent for the first year, and then about 20 percent in subsequent years.
However, you will need incentives to encourage the recycling of plastic.
Yes, in Italy you obtain 90 Euro for the recycling of one tonne of mixed plastic. However, we need better government policies to encourage the recycling of plastic into construction materials.
By Alexander Hellemans