Never heard of EcoBricks?
You can find out more here. But here is a short summary.
Ecobricks are a simple, low-tech, non-capital, plastic transition technology that follows the Earth’s example of carbon care. Ecobricking is a simple way to take personal responsibility for our plastic by keeping it out of industry and out of the biosphere. An ecobrick is a PET bottle packed solid with clean and dry used plastic. Ecobricks are made manually to a set density to to sequester plastic and create reusable building blocks. In this way ecobricks keep plastic from degrading into toxins and microplastics and out of high-energy, high-emission industrial processes.