As far as the ease of feeding the world, especially since Soylent Green was mentioned, I thought you might find this interesting:
soylent.me (add the http://)
(Note, it is not made of people)
I first heard of this via crowd-sourcing (kickstarter-ish websites), and if I wasn't so broke I actually spend LESS than $255 per month on food, this is what I would be living off of. The biggest downside to something like this going to the poor, especially in the Third World, is that it requires clean water.
There are some threads about Soylent kicking around here.
Here are a few thoughts about Soylent, summarized from the previous conversations:
1. It is not a new concept.
http://www.soyinfocenter.com/HSS/meals_for_millions.php2. It is made from highly-processed food, and is highly wasteful.
3. For the above reason, it is far, far more expensive than equivalent nutrition derived from staple foods such as rice, beans, and collards.
4. It's basically a glorified protein shake.
5. For the most part, people other than weird autistic engineers have zero interest in subsisting entirely on bland processed gruel, to the degree that in many places it is considered inhumane treatment to give prisoners such a diet.