The energy cost of the steel, plastics used in the construction of an AD plant, plus the energy involved in construction, can sometime make environmental sense and make a small contribution to energy security, However, it is as well to remember that 1 tonne of Nitrogen fertiliser nutrient, made in a modern and efficient USA fertiliser factory, according to UN-sponsored research, typically takes 21,000 (yes, twenty one thousand!) kWh to produce and deliver. N fertiliser produced in eastern block countries may use as much as 20 tomes more power. So, using fertilisers, to grow crops, to harvest using diesel to cut and transport to an AD plant, to digest to produce methane, to burn in an engine to drive a generator to produce even less electricity is insanity based on ignorance. What is more, that land could be used to produce food and we need food security and so do 100,000,000 people in central Africa which the UN reports are on the edge of starvation death. That is immorality on a global scale sanctioned by ignorant government. in Brussels and Whitehall.
(There is a chapter on renewables in general and AD in particular in “Survival”.)
Bill Butterworth, Land Research Ltd, 31 July 18