• Sep 23rd 2007 at 9:24AM
  • 6
We know that producing fuels from plant material is probably beneficial from the perspective of carbon dioxide emissions. After all the plants are absorbing carbon dioxide from the atmosphere as they grow rather than just releasing carbon that was trapped in the ground. The overall energy equation is more problematic at least with current feed-stocks like corn, canola and soy. Depending on the processes used, it may well take more energy to grow and process the crops than you get out. As we move toward cellulosic and algae based feed-stocks, the balance should improve dramatically.

However, there is another concern with biofuels. The current crops that are being used require huge amounts of nitrogen-based fertilizers to produce. It turns out that a significant portion of the nitrogen in the fertilizers is actually consumed by bacteria in the ground and then given off as nitrous oxide. Previous estimates had placed this at about two percent of the nitrogen, but new studies place that number closer to three to five percent. Since nitrous oxide has twice the greenhouse effect of CO2, it can offset much of the benefit of using biofuels in place of fossil fuels. Until we can start using feed-stocks that don't require huge amounts of fertilizers (much of which is also produced from petroleum) it may be counterproductive to mess with most current biofuels.

[Source: TreeHugger, thanks to Wyatt for the tip]

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    • 1 Second Ago
      • 8 Years Ago
      ==As we move toward cellulosic and algae based feed-stocks, the balance should improve dramatically. ==

      Do you even *read* the studies you report on?

      Algae requires LOTS of nitrogen.
      Cellulosic "Forages" are no better than Corn.

      • 8 Years Ago
      ==Switchgrass doesn't even NEED fertilization!
      Anyone have a clue?==

      Stop accepting that bullsh*t.

      Destroying the soil, like a plague of locusts isn't sustainable.
      • 8 Years Ago
      Why are not farmers switching to Higher Yielding crops?
      Higher Yields = More Profit( MONEY )

      Switchgrass doesn't even NEED fertilization!
      Anyone have a clue?
      • 8 Years Ago
      ==Corn ethanol does still reduce dependence on imported oil==
      No it doesn't!!

      "Given that the fossil fuels (primarily natural gas) that went into making the ethanol can usually serve as transportation fuels, the amount of transportation fuel that is displaced is only the 8% that was "created". That means that in reality, using our entire corn crop would only displace 1% of our annual gasoline consumption."

      And besides which, why would that even be relevant?
      • 8 Years Ago
      The issue is actually not regular NO or even NO2 but N2O (laughing gas) which has a GWP of 196. Of course, soil bacteria also release this when fertilizer is used to produce food or cattle feed.

      Therefore, no additional N2O is produced unless fields that would otherwise lie fallow are used to grow energy crops. Using agricultural wastes (cellulose) from food and feed production to produce ethanol would also not produce any additional N2O.

      Note that even if the GHG balance for corn ethanol is slightly negative rather than very positive as the industry likes to claim, it does still reduce dependence on imported oil. How much that is worth in terms of subsidies and protectionist tariffs is another matter. A switch to second-gen technology might well come sooner if those cushy government handouts were not available.
      • 8 Years Ago
      Distributed renewable electricity is the ONLY long-term solution. Everything else is just treating the symptoms instead of providing a cure. ICE’s with “electric assist” like the Prius were the first step in electrification. BEVs with ICE or H2 “range extenders” like the Volt are the next. These range extenders will become obsolete once “fast-charge” batteries can be produced economically. This will take Demand, R&D, Scale and Time.
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