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Monday, March 10, 2008

More on solar panels

Solar Energy Firms Leave Waste Behind in China


In China, a country buckling with the breakneck pace of its industrial growth, such stories of environmental pollution are not uncommon. But the Luoyang Zhonggui High-Technology Co., here in the central plains of Henan Province near the Yellow River, stands out for one reason: It's a green energy company, producing polysilicon destined for solar energy panels sold around the world. But the byproduct of polysilicon production -- silicon tetrachloride -- is a highly toxic substance that poses environmental hazards.

"The land where you dump or bury it will be infertile. No grass or trees will grow in the place. . . . It is like dynamite -- it is poisonous, it is polluting. Human beings can never touch it," said Ren Bingyan, a professor at the School of Material Sciences at Hebei Industrial University.

This next part bring up questions for me...

Made from the Earth's most abundant substance -- sand -- polysilicon is tricky to manufacture. It requires huge amounts of energy, and even a small misstep in the production can introduce impurities and ruin an entire batch. The other main challenge is dealing with the waste. For each ton of polysilicon produced, the process generates at least four tons of silicon tetrachloride liquid waste.

When exposed to humid air, silicon tetrachloride transforms into acids and poisonous hydrogen chloride gas, which can make people who breathe the air dizzy and can make their chests contract.

While I've long known that the manufacture of solar panels is far from being environmentally neutral or safe, and required tremendous energy in production, I haven't known a great deal about the details involved. The paragraphs above apply to solar panel manufacturing in general. I hadn't realized is was quite so dangerous. Even with other manufacturing in other countries that recycle and otherwise treat the waste to render it safe, the process itself seems to be quite dangerous.

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