When grain is fed to animals there is an obvious net loss of food compared to using the grain to feed humans. With beef this can be as high as using 10 kg of grain for each kilo of beef. Pigs are more efficient and chicken better still.
Many people say that the world will have to change to a vegetarian diet to support the 9 billion inhabitants of 2040, but perhaps a compromise would be better.
There are many wet or hilly areas of the world where arable crops are just not feasable, but grazing by cattle, sheep or goats can produce significant amounts of meat. Even in the UK, much land in Wales, Cumbria and western Scotland produces lush grass due to ample rainfall but would struggle as arable land.
Animals are also great at turning food waste in to new food. In the UK we have a massive problem with huge amounts of food waste going in to landfill and then emitting methane gas. Unfortunately, the spread of foot and mouth disease a few years ago was blamed on a pig producer who had fed waste food containing imported, infected meat. The government panicked and stopped the practice of swill feeding instead of tightening up and policing swill feed rules.
Most swill feeders were doing an excellent job of collecting, boiling and safely feeding waste and could do so again under sensible but strict regulations.
So perhaps in the future we should have a diet that has less meat and very little from grain fed animals except chicken.
The population of the Earth has always gone up in line with our ability to provide sufficient food and it could be argued that the population explosion of the last 60 years has been possible in large part because of artificial nitrogen fertilizer.
Good crop growth depends on sufficient soil nitrogen, and in the past farmers spread manure,and used nitrogen fixing crops such as peas, beans and clover to replenish reserves. There was also imports of guano and other nitrogen rich natural deposits.
The real breakthrough came in the early twentieth century when the german chemists, Fritz Haber and Carl Bosch invented a way to use hydrogen to capture atmospheric nitrogen and form ammonia.
The application of large amounts of nitrogen fertilizer has boosted yields to such high levels that Professor Vaclav Smil of Manitoba University estimates that ‘without nitrogen fertilizers no more than 53% of today’s population could be fed at a generally inadequate per capita level of (year) 1900 diets’.
The green revolution, using high yielding new crop verieties would have been impossible without nitrogen fertilizer produced this way but has the world population expanded on the back of an unsustainable method.
The process needs vast amounts of energy which has been mainly provided by cheap natural gas and the production of nitrogen is responsible for a large part of farmings carbon emission. We know that gas supplies will eventually decline and become expensive, probably causing a switch to using coal as the feedstock, which would be much worse for carbon emissions at a time when world leaders are commiting us to huge reductios in all greenhouse gas emissions.
We could say that the availability of cheap nitrogen fertilizer has allowed the massive overpopulation of the world and that when it becomes much more expensive as demand outstrips supply, nitrogen shortages will contribute to peak food.