Suppose some brilliant scientists devise a surgical operation which allows a human to eat, digest, and gain nutrients from grass, leaves, and all those indigestible plants. The operation costs $1000 USD. What is the best way to utilize this technology for the betterment of humanity?
Clearly the surgery should be promoted as a potential solution to world hunger. Governments would move money around and give the operation to anyone on food stamps or welfare within their own country (financially it's like an investment in reducing future taxes, so even from a purely economic perspective this makes sense), then start throwing money and surgeons into the third world.
I foresee tons of problems with this plan such as getting diseases from the grass, rapid stripping and exhaustion of plants, and people considering eating grass degrading. People in desert or icy climates wouldn't really benefit, which is a big problem. Furthermore, it's quite possible that governments, even those of pretty free countries, would ban cosmetic surgery, draft people into medical school, and in general limit freedom for humanitarian purposes, potentially causing unrest / who knows what. Then you've got your crazies who go sprinkling poison on all the grass, maybe lawsuits because your neighbor ate your grass and got sick, and a whole mess of problems basically.
Alternatively, the governments might take a slower, steadier approach, developing human-friendly, disease-free, hardy grasses and planting edible prairies all over the place and then very slowly, methodically applying the surgery to world hunger once a good framework was in place. However this could cause resentment or even revolt in starving people who think the powers that be are withholding the cure they need.
What is the best way to apply this surgery to bettering the world?