Correct me if I am wrong, but did the author make a calculation error?

The number of required energy comes in at the order of 10^20 J or 90000TWh:

https://www.wolframalpha.com/input?i=300+quadrillion+BTU+in+...

but if I multiply the energy return from biofuels with these alleged 1billion hectares of land, I get much, much more energy, billions of TWh:

https://www.wolframalpha.com/input?i=582Mwh%2Fm%5E2+*+1billi...

So unless there's a mistake somewhere, only a marginal fraction of land would be needed to cover all needs.

So what went wrong here? I think it's the MWh per square meter number. 500MWh in PV would be a 500kW solar installation in Germany. I am quite sure you cannot fit that into a square meter.

But even if we assume 580MWh per hectare per year, the output from 1billion hectares would be 580000TWh. So there's probably more wrong in that post.