Charcoal is carbon. Activated charcoal is charcoal that has been treated with oxygen to open up millions of tiny pores between the carbon atoms. The use of special manufacturing techniques results in highly porous charcoals that have surface areas of 300-2,000 square metres per gram. These so-called active, or activated, charcoals are widely used to adsorb odorous or coloured substances from gases or liquids.

The word adsorb is important here. When a material adsorbs something, it attaches to it by chemical attraction. The huge surface area of activated charcoal gives it countless bonding sites. When certain chemicals pass next to the carbon surface, they attach to the surface and are trapped.

Activated charcoal is good at trapping other carbon-based impurities (“organic” chemicals), as well as things like chlorine. Many other chemicals are not attracted to carbon at all — sodium, nitrates, etc. so they pass right through. This means that an activated charcoal filter will remove certain impurities while ignoring others. It also means that, once all of the bonding sites are filled, an activated charcoal filter stops working. At that point you must replace the filter.

With no end in sight and the continuation of unprotected strikes spreading across South Africa, the effect on domestic growth for the third quarter will be adverse and also affect the output in 2013.
Gross domestic product rose by an annualised rate of 2.7% during the third quarter and 3.2% in the second. But, depending on the duration and spread of the strikes, economists predict it could slow down to anywhere between 2% and 2.5%. Unrest in the mining sector affected growth in the previous two quarters which caused fluctuations.

An illegal strike at Impala Platinum during the first quarter caused growth in the sector to drop to minus 16.8%. Its recovery in the second quarter saw it bounce back to 31.2%, significantly boosting GDP.

It is almost certain that the ongoing strikes will have an even worse effect on GDP going forward. Two weeks ago, South African Reserve Bank governor Gill Marcus said the bank’s forecast had been revised down to 2.6% in 2012 and 3.4% in 2013, compared with previous forecasts of 2.7% and 3.8%.

In efforts to supplement fossil fuels, renewable energy—geothermal, wind, and solar—has been the chief beneficiary in much of the world. Most bets for renewable power focus on wind.  But two major constraints still prevent wind from achieving the means of substantially reducing the combustion of coal.  The first is financial: wind, like most renewable energy technologies, thrives in part because consumers are generally not exposed to its full costs. Where wind is expanding most rapidly, it relies on large public subsidies. Yet wind generators happily sell their product at a loss thanks to the generous subsidies. Subsidies were originally intended to help wind (and other technologies) gain a foothold in the market, but the industry is still not viable without them. As wind installations grow, so will the cost and visibility of these subsidies, raising questions about their political sustainability.

[source:  bostonreview.net]