Sunday, 7 April 2013

Energy: Horses for courses

Energy is everywhere. In fact if we follow on from Einstein and the notion of modern physics that there is no wave-particle duality and everything is simply waves, then there is only energy. It takes on different forms, and we measure it in different ways. In very large amounts it is the mass of the matter, so perhaps we shouldn't be worrying about an energy problem at all. Getting the energy out of the matter has had mixed reviews though.

The energy in our food is usually measured in calories, which actually are kilo calories.

Electricity is bought and sold in kilowatt hours, kWh.

Oil, petrol and paraffin, the latter also known as gasoline and kerosene, come in litres or gallons.

Gas is measured in cubic metres or British thermal units, BTUs.

It's almost as if someone were trying to make it difficult to compare them.

The average calorie intake in the world takes a few searches to find. At first almost every hit is on a website about healthy eating and dieting, telling you what your calorie intake should be, or how to get it under a certain level. I guess people who are starving to death don't use the internet! There's a list on wikipedia by country. No points for guessing which country comes top of the list at almost 3,800 kilocalories per person per day. The European average is a little less with the UK weighing in at 3,400. The Japan average is significantly lower at 2,800. Converting to Joules, the standard SI way of measuring energy, US consumption corresponds to 5.8 gigajoules per capita per annum; Japan 4.2 gJ/a; UK 5.3 gJ/a.

The Food and Agriculture Organisation of the UN recommends a daily minimum of 1,800, which is a little under half the US and European consumption. The actual figures are probably a little exaggerated, as they refer to market consumption, and don't account for food wasted between production and table, or table and mouth.

Here is another angle on energy consumption and energy waste.

In energy consumption, the US comes in 11th with 300 gigajoules per capita per annum, beaten by several gulf oil states, Trinidad and Tobago and its northern neighbour Canada. Iceland comes top of the list with over twice the consumption. Japan around half, at 160 gigajoules pa. UK less still at 140 gJ/a.

So, comparing food and other human energy use, we use something like twenty times more energy than we eat. My first reaction to this was one of pity, that we need so much more energy for our tools and toys than for our bodies.

One consequence of this is that biofuels could be devastating. If we tried to produce 1% of our energy needs by biofuels, this would mean 20% less land is available for food. This would likely be the 20% that the poorest 80% of the world live off. Advice on keeping calorie intake down would probably still ride to the top of the internet hit list.