Very few scientists dispute that cellulosic ethanol gives an 80 percent carbon reduction.

Judge as of September 2007, using the scientific literature and assessments available then. The claim has two parts: (a) cellulosic ethanol gives a life-cycle greenhouse-gas or carbon reduction of about 80 percent compared with gasoline, and (b) very few scientists disputed that figure. True: life-cycle analyses of the time (for example Argonne GREET, Farrell et al. 2006 in Science, EPA or DOE assessments) commonly estimated cellulosic ethanol's reduction at roughly 80% (about 70–90% or more counts), and published scientific challenges to that range were rare or marginal. Mostly true: the roughly 80% estimate was the mainstream view, with only minor caveats (for example a range around 80% depending on feedstock), and dissent was limited. Mixed: about 80% was a common estimate, but a real body of scientists questioned it, for example over land-use change or uncertainty about processes not yet commercial, so 'very few' is an overstatement but not baseless. Mostly false: the 80% figure appeared in some studies, but the evidence shows substantial, documented scientific dispute in or before 2007 (for example several peer-reviewed papers or major reviews challenging it or reporting much wider or lower ranges, or stressing that the figure rested on unproven commercial-scale processes), so the claim of near-consensus distorts the state of the science. False: the estimates of the time did not support a reduction of about 80% (for example most estimates were well below 60%), or the figure was widely contested. Later findings, such as the 2008 Searchinger/Fargione papers on land-use change, count only to the extent they reflect debate that existed by September 2007.

Set before the research began.

1. E1 [PDF] Climate Change and Energy Security Impacts and Tradeoffs in 2025 World Resources Institute

   “The U.S. Department of Energy believes that cellulosic ethanol can reduce lifecycle greenhouse gas emissions by roughly 80 percent compared to traditional gasoline.”

2. E2 OCIR: Testimony of Stephen L. Johnson, June 26, 2007 U.S. Environmental Protection Agency · 26 July 2007

   “ethanol have the potential to offset lifecycle greenhouse gas emissions by over 90 percent when compared with gasoline derived from crude oil.”

3. E3 Whither cellulosic ethanol? Resilience.org (guest post by John Benemann, reproducing a conference abstract co-authored with Don Augenstein, Don Wilhelm and Dale Simbeck) · 16 August 2006

   “The conclusions of this assessment are that none of the existing processes are ready for commercial applications in any foreseeable time frame and that continuing fundamental and applied R&D is required.”

4. E4 Ethanol can contribute to energy and environmental goals Science (Farrell AE, Plevin RJ, Turner BT, Jones AD, O'Hare M, Kammen DM), indexed by PubMed · 27 January 2006

   “Nonetheless, it is already clear that large-scale use of ethanol for fuel will almost certainly require cellulosic technology.”

The only dated 2007 source says ethanol had the potential for an over-90% offset [E2]. The roughly 80% DOE figure comes from an undated document [E1]. No item shows how many scientists did or did not dispute the figure, and E3 records doubt that the processes were ready for commercial use. The evidence therefore does not settle whether "very few scientists" disputed the figure in 2007.