The world is not going to suddenly run out of oil, but after the inevitable production peak is reached and the decline in production begins, we will no longer have the cheap, plentiful and reliable supplies on which our modern food production and distribution infrastructure depends. We will then be in a time of resource conflicts when demand is so much higher then supply that prices will be many times more than now and when any oil shock such as middle east war or terrorist attacks on oil installations would cause the diesel tanks to run dry on many farms.
We will then have to realise the true value of the energy in a barrel of oil. Around 50 litres of refined diesel fuel costing about £20 today will do all the cultivation, fertiliser and pesticide application, harvesting, transport and handling on 1 acre of arable land. A few years ago it would have only cost about £5, but is still a bargain for the amount of energy involved. We are, in fact, still in the cheap oil era, but it cannot last forever. Oil is finite and natural depletion of reserves or geo-political events will at some time push us in to the post cheap oil era.
This is bound to be a time of massive disruption unless we prepare in advance. We now use about 10 calories of fossil fuel energy to produce 1 calorie of food energy. When the availability of fossil fuel energy per person declines, then so must the availability of food per person if we have no substitute.
In the past, the energy needs of farming and transport were met by using around 25% of the available land to grow food for the horses that provided the power. It has been suggested that we will have to go back to that system, but it would take many years to breed the millions of horses needed and train millions of men to handle them, nor can we afford to lose the amount of land needed to feed them.
But farm machines can run on bio diesel made from crops such as oilseed rape. One acre of rapeseed will yield about 450 litre of bio diesel which is roughly enough to provide fuel for 10 acres. This is much more efficient than feeding horses, but in addition, the seed residue after removing the oil can be used for animal feed and the straw can be burnt to produce electricity .
We would also need to go back to sensible crop rotation with legumes to fix nitrogen as supplies of natural gas based supplies dry up. Careful recycling of other plant nutrients would also be needed.
If we do not start planning for the post cheap oil era now, we have no chance of feeding the 8 billion population expected by 2025 especially as we will also be coping with more droughts and floods caused by global warming.