Biofuels are of course nonsense from energy efficiency standpoint. Biogas is produced for a different purpose: it results in storable energy, which is theoretically supposed to balance energy produced by intermittent sources. Overally, biofuels are not supposed to be energy-efficient or net energy positive. If we can one day produce oil from nothing spending 2x the energy the resulting oil will contain it will be a great achievement, even a holy grail of all renewable energy work: storable, high density renewable energy good for peak loads and for transport (worst case: airplanes).