Hi Horace I can see two ways to do without nitrogen fertilizers:
- seaweed biomass as I suggested in an earlier post.
- use vegetals which feed directly on ambient air's nitrogen, I know there
are some, they may not be edible but they might be perfectly suitable for
biomass production.
Michel
----- Original Message -----
From: "Horace Heffner" <[EMAIL PROTECTED]>
To: <[email protected]>
Sent: Friday, March 10, 2006 12:01 PM
Subject: Re: Farrell responds to Pimentel regarding ethanol
On Mar 9, 2006, at 12:19 PM, Jed Rothwell wrote:
See:
http://rael.berkeley.edu/EBAMM/ERG-NPR-letter-1-30-06.pdf
Farrell agrees with Pimentel that ethanol takes a lot of input energy --
although he does not specify how much in this letter. He says that
Pimentel was wrong and that the Berkeley study did take into account the
energy used by farm machinery.
His main point is that much of the input energy for ethanol production
comes from fuels other than oil, so it produces a net increase in
transportation fuel. Maybe so, but I doubt it is economically viable, I
doubt it does anything to reduce CO2 emissions, and I expect that if the
subsidies were withdrawn no one would buy the stuff.
- Jed
Looking at Farrel's original article, I don't see any mention of the
energy required for soil restoration. Nitrogen fixation alone is
extremely energy intensive. A typical source of hydrogen for this
purpose is natural gas - which could more efficiently be used as a
vehicle fuel directly.
In regard to nitrogen, the detailed spreadsheet model only mentions:
"Nitrogen fertilizer production (MJ/ha)": 66. The total given for
nitrogen, phosphorus and potassium fertilizers is 66 + 67 + 117 Mj = 250
MJ/acre. This seems way low. Also, I don't see natural gas mentioned in
this regard.
http://www.yara.com/en/products/fertilizer/about_fertilizer/
fertilizer_use_inter.html
shows about 170 kg/hectare nitrogen fertilizer use, or about 8 GJ/
hectare. This is 32 times the energy input used in Farrel's model.
Other sites show 100-200 kg/hectare fertilization rates for various
crops. I would expect soil restoration to be extremely energy intensive
if every part of the crop is taken for cellulose digestion. Also, heavy
fertilization itself can produce air and water pollution.
Horace Heffner
