At some point, some weapons scientist is going to realize that supplying power to tanks/large war machines is the biggest hurdle, and that that biological matter can be easily broken down into energy and try to make a war machine that feeds on biomass – #Future

Yes, this is very similar to the plot for the video game Horizon Zero Dawn, but I believe it's based in some real science. Smaller war machines (like say drones) could be made to use solar power for energy. But most large machines like tanks would need more than that.

Would it be possible to use biological processes and enzymes to create a machine that could feed off bio mass like plants, animals or humans to sustain it's energy? If so, it's only a matter of time before someone tries this right? Have people been trying this already?