If fossil fuels are used to produce biodiesel, this is mostly a matter of fuel substitution - yielding only 15 to 16 GJ per hectare (RME).
(fossil fuels; are used; to produce biodiesel) (fossil fuels; to produce; biodiesel) (this; is mostly; a matter of fuel substitution)
fossil fuels fossil fuels this
are used to produce is mostly
to produce biodiesel
biodiesel
a matter of fuel substitution