Here is an article from journalist Leo Hickman, about in vitro meat. This is meat from muscle cells grown in artificial culture medium. Hickman stresses the potential gross-out factor of it, and weighs this against the important environmental and ethical problems associated with modern livestock-raising. However, whenever I hear about this sort of ultra-technological, synthetic food production, my first thoughts have to do with thermodynamics. Whether you're talking about meat grown in a lab, or crops grown in hydroponic conditions with artificial light, thermodynamics are always going to be a problem, it seems to me. Normally all life comes from the sun. The sun fuels plant growth, and plants feed humans and animals alike. The amount of sun hitting the Earth is fixed, so all we humans can do to increase food production is increase the efficiency with which plants absorb light. Piling up a bunch of plants in a tall building, for instance, won't increase food production, because the amount of light hitting that building is going to stay the same.
A major way we've found of increasing plant productivity is by using massive amounts of fossil fuel (natural gas-based fertilizers, for instance) to increase the total amount of energy available to plants. Even this tactic though is limited by the Earth's and the sun's natural dynamic, because ultimately fossil fuels are just an accumulation of solar energy from millions of years ago.
All this is to say that Hickman is mistaken to think that in vitro culture might be a more efficient way to obtain meat. Despite his techno-dazed, anti-agrarian assertion that the conversion of grass into protein by living animals is an inefficient process, the fact is that this is actually one of nature's and man's more brilliant and efficient solutions to the problem of producing food. Well-managed livestock has a very important role to play in producing nutritious food from marginal and/or ecologically valuable lands (that can't or shouldn't be plowed and cropped), as well as from inedible waste and byproducts.
So when you hear gee-whiz technological ejaculations at the prospect of non-agricultural, synthetic food production, remember that the energy to drive it has to come from somewhere. The electricity for growing lamps, the nutrient solutions for hydroponic plants and in vitro meat, all this energy ultimately must come from the sun (or its fossil fuel legacy). In a future in which the sun will shine no brighter than it does now, and fossil fuels will become even more scarce, it's naive and dangerous to think that energy-intensive synthetic food will have an important role to play, except as a Nero-fiddling-style novelty.