Taking an extremely unlikely scenario to illustarte what this means, the numbers in the table show what would be required of the land in 2010 and in 2035 assuming that all oil is produced from the land. Many of the numbers used have come from the CIA website, an excellent source of data, an example of which is shown below. The key number is the use of oil each day, the number is 80,000,000 bbl per day (barrels per day) today and this is likely to double by 2035.
|Year||barrel of oil used per day||barrels of oil used per year||area required to "grow" this oil||total arable land area||percent of arable land required to "grow" oil|
On the earths surface there are 148,940,000 km2 of land, of which 13.35% is arable (land you can use for growing crops), so the amount of land at our disposal is 19883500 km2. For various reasons this land is also being lost at a rate of 100,000 km2 per year, so by 2035 this number will be 17383500 km2. So by 2035 this would be 17% of the worlds surface, or about a third the area of the USA.
The problems are clear with biofuel use, forests will be removed, fuel crops will compete with food crops in a hungry world and the quality of the land and soil will be eroded. The scenaro is extreme here and unlikely and is intended only to illustrate the scale of the issue.