Innovation allows the human population to develop new techniques for providing additional food in the same area of space. In some ways this happens through domesticating crops such as corn or bananas and increasing the size of the produce until it hardly looks like the wild version of the produce, which can be seen below for the banana. For a fruit that is roughly the same size an individual will receive a great deal more energy than with the wild fruit.
In many cases our cattle, pigs and chickens are being raised in some pretty terrible living conditions. These living conditions cause pollution of our land, cause diseases and can be smelled for hundreds of miles away from the farm. The production of the meat isn't healthy for the animals nor for the people that live near them. However, for most people it's out of sight out of mind, or they can't afford to pay the market for humanely raised animals (grass fed beef or free range chickens).
In the US there's child hunger, but there is famine in other parts of the world. Part of this is due to poverty, water shortages or powerful people withholding the food that is available. What technologies are out there that may be able to address some of these problems?
One of the most interesting me to me is Lab Grown Meat. This would remove the requirement of using killing animals to provide the meat and proteins we need to survive. Currently, these meats don't taste all that great and most people would likely be against eating it. However, it could actually lead to a lot of other benefits. For one, if we are able to get cow meat to taste right, that means that we have the muscle and fat ratio correct. This could also allow us to use the same method to rebuild muscle mass for people who have been injured. Other benefits for people with special diets, like vegetarian or vegan, may be able to eat the meats because they aren't coming from animals.
Labs devoted to growing animal meat would reduce the amount of corn and grains going to cattle and would increase the general supply of these foodstuffs. Additionally, the area required to grow animal meat would be a lot smaller than that to raise a herd of cattle. We won't be able to replace every source of meat with this, but it is likely that it could replace a lot of it.
Another interesting idea is called the Vertical Farm Project. Instead of a farm taking up huge tracts of land, the farm could be contained in a single structure. It could take the idea of local to the extreme. There could be different floors for each type of crops and the crops could be grown using hydroponics or in a more traditional method if desired. These towers are planned to help power themselves through wind and solar power collectors. The crops would receive both artificial and natural sunlight through large windows and UV lights.
It is also likely that aside from simply providing crops the lower levels could also be used to house a version of grass fed cattle. The number of cows in the herd would have to be very small, but the manure could provide the nutrients some of the crops require. Additionally, since the air would be filtered it would reduce the impact of the smell of the cattle in the surrounding areas. The air circulation equipment could also filter out methane that the cows release and use that as an additional power source by burning it. The idea of a vertical farm like that would essentially ensure that all the material within the farm would be reused and maximize the sustainability of the farm.
At this point these ideas aren't yet proven to work. It is going to be some time before these technologies are going to be fully workable and deployed to the general public. They could work in both the developed world and the developing. The vertical farm could seriously help the sub Sahara countries in Africa as it is likely that a vertical farm like that would be able to provide crops that normally would not grow outside of the farm. Additionally, the vertical farm could have a water collector on the top and use sun light to convert ocean water into drinkable water through a evaporation and collection.