This just in. Oh wow, future food is algae - gross. I have actually eaten some. Well, it smells like cat urine. Honestly, it tastes even worse. Still, we do need our protein source. Blue-green algae such as spirulina could be grown commercially to feed us. It is really cheap to grow. Mostly, it uses waste products such as sewage. Hey, the tanks would be massive. Do hope that I do not get a job processing sewage.