The ethanol bunfight continues: Patzek's response to Farrell

[GliderGuider]

In an earlier thread I posted a link to an article critical of biofuel production, that relied in part on the work of Drs. Pimentel and Patzek. This drew a rebuttal citing a short metastudy paper by Farrell et al published in Science in January, 2006 that was in turn critical of the published work of Pimentel and Patzek.

My response at the time was that I felt the methodology of the Farrell paper was flawed. Later Pigwidgeon posted a link to a series of papers by Dr. Patzek (thanks, Pigwidgeon:thumbsup:). One of them, The Real Biofuel Cycles (pdf warning) written in March, 2006, is devoted to a very thorough analysis of and response to the Farrell paper. In it, Patzek lays out his assumptions, methodology and conclusions related to the main points of disagreement with Farrell.

I was happy to see my concern about Farrell's treatment of system boundaries confirmed. As well, this paper contains an extensive discussion of the dispute surrounding DDGs in addition to a lengthy discussion of process energy balance, why it's important and how to calculate it. As well, Patzek talks about the essentially political nature of the debate.

In the end, Patzek reveals himself to be an ecologist first, last and always, with a primary goal of protecting the environment in such a way that it will provide a sustainable future for all its inhabitants. He draws explicit conclusions: that corn production is not sustainable in the context of large scale ethanol manufacture and that in fact it is unavoidably devastating because of thermodynamic limitations; that cellulosic ethanol is not on the horizon; that we should stop thinking about ethanol as a possible holus-bolus replacement for fossil fuels; and that conservation and other demand-side measures are much more productive avenues of inquiry. All these positions are fully supported in the paper.

IMO Dr. Patzek has done the cause of science a great service with an article that directly addresses what appear to be essentially political attacks cloaked in the language (but not the substance) of science. I recommend it to all who are interested in the debate and have the inclination to wade through the science presented to support the conclusions.

[GliderGuider]

1. Net energy of ethanol - further consideration

One of the interesting things in Patzek's paper The Real Biofuel Cycle is that he presents calculations for the net energy of corn production that includes the energy cost of environmental remediation. These numbers are not generally included in the energy calculations for biofuel production. Such calculations are of course open to debate, but Patzek does provide references back to the sources of his numbers, and says he is using conservative values.

Patzek presents the net energy calculations for ethanol production in two stages. First, the energy inputs necessary to produce the corn (with its embedded solar energy providing the output energy) and remediate the land is derived. Next the energy required to manufacture ethanol from raw corn is determined. These two values can be combined to give the net energy for the entire ethanol process from corn planting to final delivery. The traditional value for net energy including DDGS credit is about 1.3, but as mentioned above this value ignores the cost of the environmental remediation necessary to ensure a sustainable process.

The result obtained from combining these two stages reveals a net energy of 0.72 if DDGS is not credited, or 1.13 if it is. Patzek further points out that the market for DDGS will saturate before all the potential output from ethanol production could be fed to cattle. This implies that some discount must be applied to the DDGS credit. That conclusion plus the unavoidable margin of error in the numbers, implies that the net energy is right around unity.

An EROEI of 1:1 is the point at which very serious questions must be asked about the value of the energy process under consideration. I can think of a lot of things I'd rather do with all that corn, related organic material, fossil fuel and sunlight than make ethanol to pour into a fuel tank.

[phantom power]

2. Seems to me that any fuel cycle with net energy < 2 is pretty weak.

Especially considering margin for error. Even net energy for PV is around 4. Likewise for cellulosic ethanol (hypothetically speaking, unless those guys with the thermal cellulose ethanol process are for real)

[GliderGuider]

3. I agree

But I'm prepared to discuss the value of low-net-energy processes (like AA batteries?) if a valid justification for them can be presented. So far I haven't seen one for plant biofuels. The implications of the sustainability costs are disturbing.