Khosla said he believed 50 million acres of US land could supply all US biofuel needs.

Read 'all our biofuel needs' as biofuel enough to meet US liquid transportation fuel demand (chiefly gasoline), which is the sense of the original discussion. Judge against credible analyses of the land needed to do that with dedicated energy crops, such as miscanthus or switchgrass, at plausible projected yields. Examples are the DOE/USDA Billion-Ton studies, National Academies reports and peer-reviewed land-use studies. The claim is hedged ('I believe'). True: credible analyses find that roughly 50 million acres (35–65 million) could plausibly suffice. Mostly true: about 50 million acres suffices only under optimistic but published yield assumptions, or the credible range is up to about 1.5× that (up to 75 million acres). Mixed: credible studies are split. Mostly false: credible estimates require about 2–3 times as much land (100–150 million acres), or the figure covers only a fraction of the needs. False: estimates are more than 3 times as much, or credible analyses find US land cannot meet those needs at all.

Set before the research began.

1. E1 Biomass as Feedstock for a Bioenergy and Bioproducts Industry: The Technical Feasibility of a Billion-Ton Annual Supply, April 2005 Oak Ridge National Laboratory (ORNL), with USDA Forest Service and USDA Agricultural Research Service (record hosted by OSTI) · 1 January 2005

   “The purpose of this report is to determine whether the land resources of the United States are capable of producing a sustainable supply of biomass sufficient to displace 30 percent or more of the country’s present petroleum consumption”

2. E2 Biomass as Feedstock for a Bioenergy and Bioproducts Industry: The Technical Feasibility of a Billion-Ton Annual Supply, April 2005 Oak Ridge National Laboratory (ORNL), with USDA Forest Service and USDA Agricultural Research Service (record hosted by OSTI) · 1 January 2005

   “Accomplishing this goal would require approximately 1 billion dry tons of biomass feedstock per year.”

3. E3 The Ethanol Answer to Carbon Emissions Issues in Science and Technology (authors: Lester B. Lave, W. Michael Griffin, Heather MacLean) · 1 January 2002

   “To provide sufficient ethanol to replace all of the 130 billion gallons of gasoline used in the light-duty fleet, we estimate that it would be necessary to process the biomass growing on 300 million to 500 million acres,”

4. E4 How Biofuels Can Help End America's Oil Dependence (Growing Energy) NRDC (principal author Nathanael Greene), with contributing authors from Princeton, Michigan State, Dartmouth, ORNL and UCS; hosted on energy.gov · December 2004

   “These policies could reduce our demand further to about 108 billion gallons per year in 2050. To meet this level of demand with our current cellulosic ethanol technology, we would still need nearly 660 million acres.”

5. E5 How Biofuels Can Help End America's Oil Dependence (Growing Energy) NRDC (principal author Nathanael Greene), with contributing authors from Princeton, Michigan State, Dartmouth, ORNL and UCS; hosted on energy.gov · December 2004

   “Having reduced our land requirement to provide all of our gasoline needs in 2050 from 1,750 million acres to 114 million acres, if we can find ways to integrate biomass production with our current agricultural demands, we are within striking distance.”

6. E6 Billion-Ton Update: Energy Crops U.S. Department of Energy, Bioenergy Technologies Office (summarising DOE/EE-0585, August 2011) · August 2011

   “At the highest simulated farmgate price of $60 per dry ton, 22 to 30 million acres of cropland and 40 to 50 million acres of pasture shift into energy crop production, depending on the baseline or high-yield scenario.”

The credible analyses available before the claim put the land needed for biofuel to replace US gasoline far above 50 million acres. Lave et al. (E3) estimate 300 to 500 million acres to replace all light-duty gasoline. The NRDC report (E4) estimates nearly 660 million acres with current cellulosic technology. The same report's most favourable figure (E5) is about 114 million acres for all 2050 gasoline needs, more than twice the claimed figure, and the report says this is "within striking distance" if biomass production can be integrated with current agricultural demands. The Billion-Ton study (E1, E2) aimed to displace only 30 percent of petroleum use and gives no acreage, so it does not support the claim. Two of the three estimates of land needed for all gasoline needs (E3, E4) are more than three times 50 million acres, and the most favourable (E5) is about 2.3 times, which is in the criteria's mostly-false band; on this evidence as a whole, the claim resolves false under the criteria.