Sustainable, or renewable, energy sources are among the most important and most challenging goals facing us today. The vast majority of our energy currently comes from fossil fuels: oil, coal, and natural gas. These fuels produce lots of energy but also pollution. However, the biggest problem is their finite nature. Although we certainly haven’t discovered all possible sources of fossil fuels buried in the earth, the undisputable fact is that the total amount in the earth is finite and constantly decreasing as we use it up. The earth is not creating new fossil fuels, at least not at a rate that will make any difference in our lifetime. Estimates vary widely regarding how much time we have left, whether decades or a century or more. But sooner or later mankind MUST find a way to live off sustainable energy sources.

What does that mean? Sustainable energy comes from any source that the earth replenishes naturally, such as the sun, wind, tides, flowing water, or geothermal heat. Today, America and other countries use sustainable sources to a very small degree. One exception is Iceland, which draws most of its energy from geothermal or hydroelectric sources thanks to its active volcanoes and extensive rivers and waterfalls. The rest of us have a long way to go, such a daunting task that it’s hard to know where to begin.

A British physicist named David MacKay explored this question in a fascinating online book called Sustainable Energy – Without the Hot Air . In it, he analyzes British energy consumption and possible sources of sustainable energy production. Starting by removing fossil fuels from the equation, his thesis is simple: we can consume as much energy as we want IF we can produce that energy from sustainable sources. In other words, the equation has to balance. His findings are not pretty. If Britain set up the infrastructure to harness every possible source of renewable energy, it would just barely be enough to cover today’s energy consumption. Realistically, Britain could only produce a portion of its needs. Even more disturbing, America’s per-capita energy consumption is TWICE that of Britain’s, the highest in the world.

So what are we to do? The easy solution is to bury our heads in the sand and hope it will all magically work out. Unfortunately, this solution will likely leave all of us in a serious crisis by the time Brenden is my age. Dr. MacKay recommends drastic changes on both fronts: dramatically reducing our energy consumption and dramatically increasing our investment in renewables. Simple changes such as turning off the lights or unplugging the toaster are nice, but they are a drop in a vast ocean. The real changes we need include electric cars, greatly increased use of mass transit, solar water heaters, setting our thermostats lower in winter and higher in summer. If you don’t have time to read the whole book, Cnn.com posted a nice summary that might take a couple of minutes.