Converting Plastic Waste Into Construction Materials
Each year, about 300 million tons of waste plastic are produced, according to UNEP. Plastic waste accumulates just about everywhere from oceans, bays, and coastlines to riversheds, lakes, and population centers. It’s a well-known global problem, and yet where are the solutions? The Center for Regenerative Design and Collaboration (CRDC), which is based in Costa Rica, has been developing a process to convert waste plastic into building materials like bricks and concrete. The President and CEO at CRDC, Donald Thompson, answered some questions about the materials for CleanTechnica.
How are you able to take waste plastic and use it to make bricks?
We heat extrude shredded commingled plastic that has been pre-conditioned with mineral additives to make a plastic limestone hybrid that is crushed into a coarse sand aggregate. The resulting hybrid resin aggregate looks and performs exactly like natural coarse construction sand but is 1/4 the weight and provides other favorable qualities to the end products. We add this synthetic aggregate to standard concrete mixes up to 10% by volume.
How long does it take to convert the plastic, and how many bricks can you make in a day?
The aggregate production process is shredding-batching-extruding-granulating, the block molding process is totally conventional and is batching-mixing-molding-storing, in a perfect sequence this cycle could take place in a matter of hours from waste plastic to block. We have pilot projects now operational in Costa Rica, New Jersey, and Cape Town that are currently being upgraded to 100 tons of synthetic hybrid aggregate per day, or in terms of regular CMU blocks, this is about 200,000 blocks per day.
Why did you choose Capetown as a target site, and what will be the first project there?
The project started in Costa Rica with the goal to use the unmanaged plastic waste stream as a quality feedstock that would then be sequestered into long term appreciating assets, quality building products. South Africa was a natural next step as they have a plastic waste issue as well as a serious housing deficit. From there, we focused back on the developing world and opened operations in the USA. We currently have interest from around the world.
Are the bricks that contain waste plastic strong enough for home construction?
Our standard CMU concrete block meets or exceeds all ASTM strength and fire requirements. They are recognized as better and more resilient blocks and therefore can be used in any code-compliant building project.
How long can they last once they are used in a structure?
The block will last for the life span of the building, usually, in terms of bank building appraisal, this would mean 50-80 years, at the end of this term the structure was demolished the blocks could be crushed and used again in new structures. This represents the best kind of product “circularity” in that the product is fixed in appreciating assets for the long term and the recycling is indefinite at the end of each extended term.
What is the cost of a brick containing plastic waste relative to a conventional brick?
There are a lot of factors that come into play to answer this question accurately, but we currently charge approximately 5% more per block and correctly market it as a high-quality green building product.
What kind of structures can be built with the bricks?
CMU Blocks are our volume product target, but our synthetic hybrid aggregate can be used in any concrete mix or product, and we are as well testing our aggregate as an asphalt modifier for road construction and in the future will formulate batches specifically as pyrolysis feedstock for waste to energy. Our corporate core business prioritizes the conversion of the plastic waste stream into social housing with the intent to solve two of the world’s largest issues synergistically.