In July, scientists at the University of Maryland announced the development of bioengineering techniques that could be used to mass-produce a new food for public consumption: meat that is grown in incubators.

The process works by taking stem cells from a biopsy of a live animal (or a piece of flesh from a slaughtered animal) and putting them in a three-dimensional growth medium -- a sort of scaffolding made of proteins. Bathed in a nutritional mix of glucose, amino acids and minerals, the stem cells multiply and differentiate into muscle cells, which eventually form muscle fibers. Those fibers are then harvested for a minced-meat product.

Scientists at NASA and at several Dutch universities have been developing the technology since 2001, and in a few years' time there may be a lab-grown meat ready to market as sausages or patties. In 20 years, the scientists predict, they may be able to grow a whole beef or pork loin. A tissue engineer at the Medical University of South Carolina has even proposed a countertop device similar to a bread maker that would produce meat overnight in your kitchen.

There are still several major hurdles to clear, like figuring out a way to get stem cells to proliferate cheaply enough that meat could be mass-produced. But if in vitro meat becomes viable, the environmental and ethical consequences could be profound. The thought of beef grown in the lab may turn your stomach, but in vitro meat would avoid many of the downsides of factory farming, most notably pollution: in the United States, livestock produce 1.4 billion tons of waste each year. What's more, once a meat-cell culture exists, it could function the way a yeast or yogurt culture does, so that meat growers wouldn't need to use a new animal for each set of starter cells -- and the meat industry would no longer be dependent on slaughtering animals.