In 1930, the English economist John Maynard Keynes took a break from writing about the problems of the interwar economy and indulged in a bit of futurology. In an essay entitled “Economic Possibilities for Our Grandchildren,” he speculated that by the year 2030 capital investment and technological progress would have raised living standards as much as eightfold, creating a society so rich that people would work as little as fifteen hours a week, devoting the rest of their time to leisure and other “non-economic purposes.” As striving for greater affluence faded, he predicted, “the love of money as a possession . . . will be recognized for what it is, a somewhat disgusting morbidity.”

This transformation hasn’t taken place yet, and most economic policymakers remain committed to maximizing the rate of economic growth. But Keynes’s predictions weren’t entirely off base. After a century in which G.D.P. per person has gone up more than sixfold in the United...

Sir, The debate over the use of hydrogen as a future carbon-neutral fuel is a distraction. We do not need hydrogen to meet carbon-zero targets, as there are more readily available alternatives.

The world dumps about 100 billion tonnes of biogenic waste into the environment every year, including food waste, sewage, animal slurries and agricultural residues, which ferment and produce methane. Were we to capture those wastes and their methane, we could produce renewable, carbon-negative energy known as biogas, as well as composts to return humus to our badly deleted soils.