Waste -> Energy

There is a great article over at the Oil Drum.

In the early oil days, gasoline was a waste product. When refined, they used to dump it wherever possible to get rid of it. It wasn't until someone found out that it could be burned in an engine that it actually became useful.

There is a similar situation developing today:

This story starts about as far away from PV [photo voltaic solar cells] as you could think of, back in mines producing phosphate rock. Phosphates have long been in high demand as fertilizer (phosphorus is an essential element of life) and phosphate rock (fluoroapatite, Ca3(PO4)3CaF2) is today's major mineral source of the P in the KNP of fertilizers. This rock is dissolved in sulfuric acid (H2SO4) to release phosphoric acid, gypsum (CaSO4) and hydrogen fluoride (HF).

Hydrogen fluoride is nasty stuff. Today's method of disposal is to combine it with silicon dioxide (quartz sand) to make fluorosilicic acid, and then neutralize it with sodium hydroxide (lye) to make sodium fluorosilicate, Na2SiF6. This has some minor uses as a source of fluoride for drinking water, but far more is produced than can be used. It's been piling up for a long time. If Fluoride Alert's figures can be trusted, roughly a million tons of this stuff (containing about 600,000 tons of fluorine) is made every year.

That million tons of silicate also contains about 147,000 tons of silicon. It's been sitting there ever since.

That resource got noticed some time ago, during the alt-energy boom which followed the 1970's energy crisis. SRI International engineered a process which mixes sodium fluorosilicate with metallic sodium (Na). The fluorine has a greater affinity for sodium than silicon, so the result is sodium fluoride and elemental silicon. SRI claims that this process is simple and cheap (under $15/kg in volume), and easily scaled up to 1000 tons/year. The process got shelved after energy got cheap during the mid-80's, but the world has changed again and SRI has dusted it off. Per their presentation at last May's Clean Tech conference, the silicon can be turned into solid pellets, or cast directly into round crystals or ribbons.

Enter Evergreen Solar. Evergreen's "string ribbon" process produces 100-micron (0.1 mm) thick polycrystalline silicon ribbons directly from a molten silicon bath. Here's the new prospect for PV silicon: semi-toxic fertilizer waste and metallic sodium in, production-ready rectangular polysilicon wafers out.

Voila'. Cheap photo voltaic solar cells.

Turns out we make enough of this stuff to crank out inexpensively produced photovoltaic cells. Enough cells to produce 10% of the U.S. energy needs each year.

It's a long and wonkish read, but it demonstrates the possiblities of creating efficient energy resources that are clean and reliable.