Much as we treehuggers hate the thought, we need to dig up the earth to build a clean power economy. To put solar panels on more roofs, we have to mine silicon. To build the batteries to run an electric-vehicle nation, we need to mine lithium.

Initially at least, building wind turbines and solar panels means digging raw materials like iron ore and silicon out of the earth -- just like we do for supplies of dirty energy, fossil fuels like oil and coal.

The difference is that a dumptruck load of steel for a wind turbine will provide energy for more than 100 years, but a truckload of tar-sand, coal or oil goes up in smoke in a few hours.

Making mining more eco-friendly is part of creating a carbon-neutral world. Caterpillar is taking a step in that direction by unveiling the world's largest electric vehicle this week at the Nevada mining truck expo -- a 345-ton all-electric mining truck that will go into production in 2010. Another model, a 250-ton truck, will be available with electric or combustion-engine options.

Caterpillar, in business for 80 years, has a corner on this market: No other manufacturer is attempting to build trucks heavy enough to be used for mining -- heavier than 200 tons -- with an electric motor. That may have something to do with Caterpillar joining the carbon-responsible industry group USCAP.

In the late 1960s, Caterpillar was one of the first manufacturers to try electric-drive trucks. It abandoned that line of vehicles, but now that we're counting carbon emissions, the company is developing truck models that can be used by a more climate-friendly mining industry.

To reduce impact on the environment, electric-powered mining trucks would need to be charged using clean power from wind, solar or geothermal generation. Currently, mining silicon is dirty primarily because of mining truck diesel emissions.

Wind's greatest potential is often realized out where people don't live (because it's too windy) but mining can be done there. Solar is best where the solar radiation is so intense that evaporated seas full of lithium can be mined there to run all our EVs. Think of the salt deposits in Nevada.

But what if an industrial-scale solar or wind farm in those areas supplied the charging power for electric mining trucks? How much would this reduce the environmental costs of mining?

Photo by Philip Greenspun