Urine is filtered through sand, and the resulting fluid is sterilised with ultraviolet light.

ECONOMIST: Monitor: Flushed with pride | The

On reaching the shale, the mixture of water and fracking fluid bursts open the rock and the sand keeps the fractures open, allowing the gas to flow to the surface.

ECONOMIST: Fracking

Hydraulic fracturing involves the injection of fluid consisting of approximately 99.5% water and sand (the rest consists of common industrial or even household chemicals or materials) through wells constructed with protective casing and cement, into producing shale formations.

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Carbo Ceramics ( CRR - news - people )(CRR, 73) , a Houston firm that makes various forms of "proppant, " particles (sand or a synthetic substitute) injected along with the fracking fluid to keep the fissures propped open after the pressure is withdrawn.

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