Saturday, August 12, 2006


Deep thoughts.

One of the greatest concepts in human philosophy comes from the field of thermodynamics, from a man almost unknown outside that discipline, Lars Onsager. Onsager developed a notion for how processes evolve, known as the reciprocal relations or, more colloquially, as Onsager coupling. A very simple example might be air leaking out of a balloon. Molecules flow out and cold "flows in." The greater pressure inside the balloon amounts to a force driving the molecules out (called a "flow"). The product of force and flow is proportional to changes in thermodynamic quantities, such as entropy. For the full nine yards, click here. From a philosophical standpoint, the lesson is that one can couple two productive processes to minimize waste (entropy production). One wonderful example I stumbled across is this A project to reduce the carbon dioxide emissions from oil refineries by using the gas as "fertiliser" in commercial greenhouses has been so successful it is being extended. The project, which adds new meaning to the term "greenhouse gas", is the first in the world. It distributes CO2 from Shell's Pernis refinery outside Rotterdam to 400 greenhouses, saving a large amount of natural gas each year, which is equivalent to 170,000 tonnes of CO2....tripling the concentration of the gas inside the greenhouse they allow the plants to photosynthesise more quickly. This boosts productivity by up to 25% and cuts growing time... So, here, we have two processes: the burning of gas to create electricity and the stimulation of photosynthesis to produce carbohydrates. Each process can occur independently, but relatively-speaking wastefully. By coupling them, one can extract more work out of the same process. By the way, the stimulation of photosynthesis that can be achieved in a greenhouse probably does not happen in global warming. Global warming has other effects, such as elevation of temperature, changes in rainfall pattern, and acceleration of depletion of ozone that overcome the growth stimulus. We human beings tend to think in simplistic terms. Global warming is bad-- indeed it is. But to get out of the crisis, we will need to learn to couple two bads to make a good. The Rotterdam experiment is the sort of thing that needs to be encouraged.
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