Over at The Oil Drum Professor Cutler Cleveland has an essay "Energy Transitions Past and Future that is well worth the time to read. One of the points he makes is about biomass energy and the amount of land needed for biomass to displace oil:
The low energy and power density of most renewable alternatives collides with a second global environmental imperative: human use of the Earth's plant life for food, fiber, wood and fuelwood. Satellite measurements have been used to calculate the annual net primary production (NPP)—the net amount of solar energy converted to plant organic matter through photosynthesis—on land, and then combined with models to estimate the annual percentage of NPP humans consume (Figure 12). Humans in sparsely populated areas, like the Amazon, consume a very small percentage of locally generated NPP. Large urban areas consume 300 times more than the local area produced. North Americans use almost 24 percent of the region's NPP. On a global scale, humans annually require 20 percent of global NPP.
Human appropriation of NPP, apart from leaving less for other species to use, alters the composition of the atmosphere, levels of biodiversity, energy flows within food webs, and the provision of important ecosystem services. There is strong evidence from the Millennium Ecosystem Assessment and other research that our use of NPP has seriously compromised many of the planet's basic ecosystem services. Replacing energy-dense liquid fuels from crude oil with less energy dense biomass fuels will require 1,000- to 10,000-fold increase in land area relative to the existing energy infrastructure, and thus place additional significant pressure on the planet's life support systems.
Note that the current human use of global NPP is only going to go up as populations expand and more affluent populations use more land for plant crops, livestock, and also for biomass energy and wood for structures.
The already extensive harnessing of biomass to produce useful products for humans strikes me as a strong argument against biomass energy. The only compelling argument for biomass is the ability to produce liquid fuels from biomass suitable for use in vehicles. But we can develop ways to use more electricity in transportation including better batteries and methods to make synthetic liquid fuels.
|Share |||Randall Parker, 2007 August 12 11:44 PM Energy Biomass|