Hello friends! I have just finished my first ecobrick! Hooray!
Ecobricks are basically, a plastic bottle that you stuff with soft plastics (they are calling it "hard plastic" when it's like, candy wrapper consistency, and "soft plastic" when it's like, grocery store bag consistency; but to most people, hard plastic is the bottle itself and soft plastic is all the wrapping types). You have to really pack it in there with a stick so that it is dense enough. You have to weigh it to get a certain density to make it solid enough to build with.
the almost halfway point
You can learn all about ecobricks and how to make them here.
My finished ecobrick weighs in at 519g, which is just dense enough to pass.
People register their ecobricks on the site (there's an app, but I couldn't find it so I just used the website), so they keep records of how much plastic was contained. The idea is to contain it so it doesn't break down into microplastics in the environment. You can use these to make furniture like stools, but eventually it needs to be sealed up inside a wall or something so it doesn't break down and let loose the plastic. People can donate their bricks toward projects that are using them, or make a project yourself.
There is even a blockchain component to it, which I didn't realize until today when I was registering mine, where I think people who verify the registered bricks earn coins.
It's a worldwide movement, and very cool, imo. We can all do our part to minimize the harm of human pollution.