Photosynthesis occurs in plants but not humans. Human dependence on food has affected the longevity of the earth negatively. Therefore, we should strive for self-sufficiency.

This is where the green people idea comes in. If I manage to manipulate the human genome so that it has the genes for photosynthesizing skin cells, then humans are going to be green (the green pigment chlorophyll collects light). The benefits of this genetic intervention are less pollution, less waste, and less killing of other species.

Sure, humans would still contribute to global warming, but I predict that the contribution would be much less than that of now. Greens a masculine color anyway. Am I right?

it would be difficult. though i do think it is possible to alter the human DNA to create skin cells with chlorophyll, the structure of a leaf is different to that of skin, since their purposes are different.

but thats just a guess

though i reckon a more practical, yet still viable alternative is to create something similar to a solar panel, with with genetically engineered chlorophyll that creates food

Even assuming you got this to work perfectly (lol), there is no way you could generate even close to enough energy via photosynthesis to power a human body. We evolved the way we did because it is the most efficient way to get the amount of energy we need out of our environment.

This. Either we would have to require a lot less energy, or just use photosynthesis as supplement and continue regular eating habits.

Read Oryx and Crake, then do that.