A joule of lower heating value from coal is thermodynamically and
economically much less valuable than a joule as electricity. Lardon
et al., for example disregard the influx of solar energy to the system
and show a range from 2.6 MJ lost to +105 MJ gained per kg of algae
biodiesel produced. These values may, for example, all become
negative if the input of solar energy is counted. However, this does
by no means invalidate all algae-based diesel concepts.