Fertilisers, “wastes” and energy

  • 21,000 kWh of electricity is the energy cost of one tonne of Nitrogen nutrient in mineral fertiliser.
  • Ancient humans were better at recycling wastes to land than the current generation.
  • We can produce biofuels from crops fertilised with processed wastes.

By Bill Butterworth

20 December 2014


The United Nations (UNESCO) sponsored a bit of research into energy cost of fertilisers (1) a few years back. The study was done on “typical” and therefore relatively efficient (compared with most of the rest of the world typical) manufacturing facilities. The conclusion on mineral Nitrogen fertiliser was that the energy cost of one tonne of Nitrogen nutrient (equivalent, for example, to three tonnes of ammonium nitrate) was 21,000 kW h. Yes, that is twenty one thousand kW hours, or “units” per tonne. Now, the FAO of the UN also predicts that global production of Nitrogen fertiliser in 2016 will be over £11 million tonnes. That will consume at least 231,000,000,000 kWh of electrical power. Most of that will have come from burning fossilised fuels.

Bearing in mind that it is possible to grow really good crops, safely and without mineral fertilisers, that is figure is insane. Repeat; insane.

It is quite possible to recycle a wide range of the wastes human activity produces, nearly all wastes human activity produces, to soil to grow crops safely. Composting outdoors, in vessel composting, AD – anaerobic digestion, TAD – thermophilic aerobic digestion, even just what farmers call direct incorporation (just plough or dig it in) – these are all ways of returning valuable nutrients to the soil. Yes, it is better if it is controlled by a qualified, trained in the art, experienced soil scientist – but it can and has been done.

Fertilisers from “wastes” has, since man first began to farm, been practiced safely and successfully. Like all things, it needs to be done sensibly but it can and does work. Further, recycling to land can produce food, fibres and energy. That energy can come from oil seed rape which is done in the UK to produce “vegetable oil” which can be used to drive a diesel engine. It could be other oil-bearing fruits and seeds such as lupins, oil palm and Jatropha.

Research by Land Network (2) shows that 1 hectare of land growing oil seed rape (see picture above)for either biodiesel or PPO (Pure Plant Oil to drive diesel engines), will produce enough energy to farm that 1 hectare and 9 more (which could be of wheat of whatever crop). In that research, 1 ha of oil seed rape produced enough energy to cultivate 9 ha and plant and harvest 90 tonnes of wheat. It was done using wastes as fertilisers. Nobody was caused to starve and there were no rain forest cut down.

(1) W. Gellings, Kelly E. Parmenter, (2004), ENERGY EFFICIENCY IN FERTILIZER PRODUCTION AND USE , in Efficient Use and Conservation of Energy, [Eds. Clark W. Gellings, and Kornelis Blok], in Encyclopedia of Life Support Systems (EOLSS), Developed under the Auspices of the UNESCO, Eolss Publishers, Oxford ,UK, [http://www.eolss.net

(2) Butterworth B, Reversing global warming for profit. MX Publishing. London.,2010.