For lab grown meat, you normally start with cells, not necessarily DNA, although you can genetically modify the cells to carry whatever DNA. But, it wouldn't be much harder to harvest your cells instead of DNA, albeit a bit more painful.

Honestly, this isn't a crazy idea. If we can grow meat, the initial cell culture is trivial and I can see a company like this existing as soon as the stigma goes away a little bit. Unless human meat is particularly bad, it will definitely be something on the menu, and maybe even be billed as an ethical choice (you are eating yourself instead of another being).

Thinking about it, using solar power to grow your own cells to then eat it for energy would be a convoluted form of photosynthesis.