Since the middle fifties, my thoughtlife has been dominated by ‘non-replenishable natural resources’ – especially the fossils.  I continue to be obsessed by `the noble substance’, petroleum (“nobody ever said the stuff will last forever”), leaving environmental concerns to other people.  “Just think,” I have told countless audiences since the ‘50s, “it will be difficult to do much polluting in the Post-Petroleum Age.”  ‘Carbon footprint’, however, is a different matter.  For example, coal will continue in abundance, and coal-fired power plants are proliferating.  Sure, that enables electric trains and trolleys to displace gas guzzlers and reduce congestion; however, coal is almost entirely carbon, making the concept of ‘clean energy from coal’ something of an oxymoron.  SF Telegraph readers will doubtless prefer an article about green solutions not problems like that. 

To make sure I am not too far out of date, I clicked up the ‘sustainability’ article in Wikipedia and found an immense subject.  Still, the objective, living in equilibrium with the impoundment of solar energy (“equilibrating” was the word I have used since 1953), continues to be tyrannized by a harsh reality: Whatever its abundance, the sun's energy is spread out diffusely over the earth's surface.  As I said in my chapter “The Perpetual Sun,” that amounts “to one calorie per minute per square centimeter -- at high noon, on a clear day, near the equator.”  Today, green plants are increasing in popularity as nature’s marvels, each with a negative carbon footprint (in the daytime).  They act as tireless automatons casting solar shadows and fixing atmospheric carbon – for their own benefit, of course, not ours. Still, without complaining, green plants take up water and nutrients from fertilized soil and manufacture replacements for themselves, while providing nourishment for various parasites including us.  Green plants package up energy, too, as hydrocarbons.  Only a fraction of that kind of energy comes from burning carbon, the rest comes from burning the ‘hydro’ part, producing water, which is not a greenhouse gas.  That would be splendid but not exactly sustainable, it turns out. ‘Biomass’ must be harvested then processed into ‘biofuels’.  That takes energy.  Whereas some biofuels can act in place of petroleum in internal combustion engines for cars and buses and trucks, there is this one critical question: If it takes more than one unit of energy from either fossil fuel or biofuel to produce one unit of energy from biofuel, what’s the point?

For the most part, achieving sustainability seems to take the form of individual human endeavors in conservation, in recycling, in changing life-styles.  Advances in large-scale energy technologies continue to be far-off and fraught with political viscosity.  Nevertheless, there was one especially pleasant surprise for me and it may be news for some SF Telegraph readers: For a given amount of solar shadow, ‘photovoltaics’ are much more efficient than green plants at the art of converting sunlight to electrical energy.  You don’t have to irrigate and fertilize and harvest them and burn their husks in a furnace.  Manufacturing solar cells does take energy and other resources, including money, but once installed, they repay all that and go on year after year supporting a truly sustainable source of – pre-distributed! – power, all without emitting greenhouse gases.  As for costs, silicon technology may be most famous throughout its history for crashing through old ideas about economies of scale.
 

A coal-energized electric car has a larger 'carbon footprint' than a deisel powered SUV (work in process).