Now ideally the kidneys would filter microplastics as they do other waste and we could happily piss those plastics right out. Sadly that’s not the case (stupid – it really wouldn’t be that hard). But we still only need one kidney to live normally so I’d keep my left, which is slightly larger and does more filtration, and sacrifice my right for microplastics storage. The question assumes that we can store microplastics in a single organ so let’s say I can implement some bioengineering to divert the microplastics into this kidney alone. It would also have to be disconnected from my ureters (tubes connecting the kidneys to the bladder). A few decades down the line, I’d get the kidney – now nearly completely plasticized – removed and discarded (or put on display? for science or art) and live the rest of my days fairly plastic-free.