[dredmorbius]

This does not sound promising. Scaled linearly to the current level of oil production, this would cover more land area than Brazil and India put together.

All biofuel options have this limitation. Peak production for canola oil is around 100 gallons/acre. Yields for algae are higher, around 5,000 - 10,000 gallons (120-240 bbl) /acre for open-air operations (some greenhouse-based operations claim higher productivity though there's a great deal of skepticism over these), but scaling algae biofuel productions up has been extremely problematic to date. All values on an annual basis.

At present rates of consumption in the US (20 million bbl/day, or 7.3 billion annually), you'd need 30 - 75 million acres devoted to fuel production, if I'm getting my math right. Yield claimed here are for 280 gal/acre, or 6.7 bbl/acre.

The vast majority of oil goes to transportation (where it provides 95%+ of the energy used). In some cases (rail, urban/metro private vehicles, transit, canal traffic) electricity or batteries can be substituted. For others (shipping, and especially air traffic) there are few alternatives to liquid fuels, though ships could move on pelletized biomass and/or wind.

Cutting transportation energy requirements would help, but the expectation of much of the world that it will have access to Western levels of per-capita resource utilization would put a huge burden on biological productivity. I don't see the expectations being fulfilled.

Other alternatives include synthesis of hydrocarbons using electricity. The US Navy is researching such methods, which might be able to synthesize aviation fuel using surplus generating capacity from nuclear-powered aircraft carriers (aviation fuel effectively limits cruise duration as it must be frequently resupplied, cost is another factor), and the ability to obtain both carbon and hydrogen from seawater is a benefit, but the process requires _billions_ of gallons of water to be processed. Again, scale of operations is a significant constraint.

[throwaway_yy2Di]

"At present rates of consumption in the US (20 million bbl/day, or 7.3 billion annually), you'd need 30 - 75 million acres devoted to fuel production, if I'm getting my math right. Yield claimed here are for 280 gal/acre, or 6.7 bbl/acre."

My math disagrees with yours, I'm getting 1.1 billion acres? That's about 1/5th of the figure I got for the globe.

https://www.google.com/search?q=%2820+million+oil+barrels+%2...

[dredmorbius]

I was giving acreage for algae at 120 - 240 bbl/acre.

At 6 bbl/acre for jatropha as described in the article, you'd need 1200 million acres. On the high end, that's a region 1370 miles on a side -- roughly half the area of the US (very roughly -- I'm using a 1000 mi x 3000 mi rectangle as an approximation). Wikipedia says 3,717,813 mi^2, 570,000 of those are Alaska. Yeah, 60% of the non-Alaskan land area of the country.

There are 409 million acres of arable farmland in the US (about 17% of the total land area).

Your 1/5 estimate works out as the US consumes about 20% of global oil extraction.