Burning wood instead of coal?

burnwoodThis blog has frequently commented on the now controversial use of coal as a source of energy for power plants and other industrial energy uses. Since this became a “front-and-center” issue, a lot of research and plant-scale experimentation has gone into how to keep coal as a fuel, an approach termed “Clean Coal” technology. This concept has now reached the end of the road: (a)Scrubbing flue gases with alkalis such as ammonia or caustic is too expensive and/or produces sludges that are difficult to dispose of. (b)Carbon dioxide capture (e.g. in underground caverns) is  also too expensive and only makes sense when a large carbon dioxide demand (e,g, from tertiary oil recovery is nearby(see Sept 8th, 2014 post) – not the case for a most large power plants) and (c) Gasifying instead of burning the coal, which concentrates the CO2 stream has led to the construction of two hugely expensive plants in Missouri (see January 2nd, 2016 post)and Sasketchewan that, even if and when onstream at design capacity, will never be duplicated. There is also the Skyonic approach (see June 26, 2014 post) that makes sodium bicarbonate from the CO2 scrubbed from flue gases, but this technology is nor scalable, since there is limited worldwide demand for sodium bicarbonate. China, which has much greater pollution from coal than the U.S. (particulates as well as carbon dioxide) still talks about Clean Coal, but seems willing to spend the large amount of extra money to, for example, gasify coal instead of burning it.logs

Recently, we have heard that Congress will soon pass a bill that would encourage the use of wood (and other biomass) as an energy fuel that does not add to the carbon footprint. This is conceptually true. The decay of wood releases the contained carbon into the atmosphere, in a sense similar to burning it. The releases carbon is then reabsorbed as a new tree needs the carbon to grow. So, what’s wrong with this picture? Firstly, we need to restrict CO2 release now to deal with global warming, not many decades from now when the presumably (but not guaranteed) reforested trees start to absorb large mount of CO2. Secondly, to make any impact, we would have to decimate much forested land to make any appreciable impact on replacing coal with wood, leaving aside the logistical problem of getting massive amounts of wood to power plants.   It has been pointed out that switchgrass and other such waste biomass has a much shorter carbon cycle, but this again begs the question of getting this material in huge quantities to power plants.

The push for wood as an energy source comes from legislators from states with huge forests. Need I say more? But perhaps readers of this post will cheer that they are really not polluting the atmosphere when they burn wood in their fireplace, because somewhere a tree is being planted that will reabsorb all of the carbon going up their chimney.




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