David L Babcock <[email protected]> wrote:
> Re many things running out, I agree that we are starting to learn how to > work around looming shortages in various critical materials, but many of > these are going to prove hopelessly expensive to implement. I offer > phosphorus as an example: where do you find a replacement for that, feeding > 7 billion people, when the mines run out? > Well, the stuff does not vanish. Mass is conserved. It is not blown in small particles into the landscape the way some Pd in catalytic converters is. So let's see . . . Most is used for fertilizer to grow plants. In the U.S. most plants are fed to livestock, and the rest is eaten by people. So the P ends up in . . . pee, and manure and sewage. So that's where you will find it. With cheap, limitless energy we can easily recycle it. There isn't much in seawater: 0.1 ppm, but I expect we will be purifying vast amount of seawater so maybe we can get some from that. In the future I expect meat production will be done in vitro. This will use far less P. It will eliminate most pollution from manure run-off. It will eliminate the need for a large fraction of agricultural land. Breakthroughs such as this can greatly reduce our need for resources. In the long term, I expect we will build space elevators and begin exploiting asteroids and other off-planet sources of raw materials. I hope we also transfer most heavy industry to geosynchronous industrial complexes at the terminals of space elevators. There is plenty of space in space. Way more than on earth. For details, see Clarke, "Profiles of the Future." - Jed
