An interesting blog from Robert Rapier appeared on R-Squared Energy Blog recently. Robert made some back of the envelop calculations to find out how much biodiesel the total amount of arable land can support. He comes to the remarkable conclusion that only one third of the current oil consumption can be replaced by biodiesel (this is the best possible case as no energy needed to produce the fuel was taken into account). Since the energy source for the biodiesel is eventually the sun and the fact that photosynthesis is a quite inefficient process ¹, the question arises whether it would not be better to use solar cells instead to convert sunlight to usable energy forms rather through the indirect way of bio fuels? Of course there are quite a number of issues with solar energy as well (such as not everywhere sufficiently available, not all the time available, storage is difficult, infrastructure changes needed etc. etc.) as also becomes clear from the string of comments to Robert’s blog. Use the link in the first sentence to go to Robert’s blog.
1. Of course for nature this efficiency is no problem at all, enough plants are growing to sustain the planet’s ecosystem. This changes, however, if we are going to burn sunlight faster (through the bio fuels) then the photosynthesis per unit area can keep up with! See for some more language on this my book.
Copyright © 2007 John E.J. Schmitz