LEAVES - October 27, 2011

Every year at this time, we collect the discarded leaves of our beautiful green city. We pay to have them swept up and taken away, with many of them composted for eventual use as mulch and fertilizer for our lawns and gardens. This composting is a vast improvement on the earlier practice of burning most of them and releasing the CO2 into the air. However, it is still distinctly inferior to subjecting them to anaerobic digestion, in which much of the chemical energy that our thousands of trees have stored in them is made available for chemical energy of a very high level, compared with the CO2, which is generally acknowledged as a pollutant and a contributor to the warming of the planet. Of course, even the digestion gives off part of its output as CO2, but in the case of the composting, the part of the organic process yields methane, which is a far worse product than the CO2. Also, the sludge that is the residue of the composter is a far richer fertilizer, since its proteins and oils have not been degraded by the oxidation of the rest. In addition, the average time needed to reduce the leaves to mulch is much less in the digester than in the open air, even when deprived of O2. There is of course an investment needed in the building of a digester, but the additional energy needed (if any) can easily be provided by solar cells yielding both power and heat to run the digester. For a city that hopes to be graced by its new Inst. of Discovery, it is a step further into the world of the future than the one on the ceremonial quarter, which features a cow, corn and cheese. As the modern efforts abandoned in the past century to avoid the pretended threat of commonism, it would be a claim on the kind of world we hope to build.