Use vertical farming to grow food for humans and livestock and return current farmland to nature.
A drinking cup that can be dropped off after use at many different places so they can be returned to cafeterias for reuse.
Standard-sized office paper with printing on only one side could be collected for printing on the second side. The used paper could have a message printed over the original used side to promote the idea and also avoid confusion about which side is the new one.
Aquatic garbage could be collected and sequestered using "artificial whales" that swim through affected areas "filter feeding" as baleen whales do. They would sort items by size and material using 3D printed electroactive polymers in conjunction with 3D printed plastic filters and other components. Larger sea creatures would avoid them. Smaller ones capable of free swimming which were captured would be given the opportunity to swim out of the tank they were funneled into whereas the garbage would stay behind. ... more
