Coke and Oil
Everyone knows these days that the price of food is going up, as is the price of energy. There’s a much documented relationship between the price of food and the price of oil:
- corn, which is a major input to processed foods and meats can be converted to ethanol when fuel prices are high, which reduces the amount of food produced
- oil is used in agriculture to produce chemical fertilizers, run tractors and pump water
I don’t eat much corn, but corn is also used in soft drinks like Coca Cola. What’s the relationship between Coke and Oil?
Cost
Today I paid $4.39/gallon to fill my tank with unleaded. Safeway is selling 2 liters of coke for $1.89 ($3.63/gallon). The two substances are comparable in cost.
Energy content
A gallon of coke has 1680 kilocalories.
- This is about the number of calories a small inactive person uses in a day. (The average amount is closer to 2400 kcal).
- Spread over a 24 hour period, it represents about 80 Watts of average power.
- It’s also enough energy to raise me about 400meters higher than I am now, or allow me to bike about 40miles or so.
Gasoline contains about 35MJ/liter. This is 132MJ/gallon, or 31600 kcalories. Gasoline is roughly 19 times more energetic than Coca Cola by volume. If we could eat gasoline maybe we wouldn’t have to spend so much on actual food. 
Or is it just that Coke is really overpriced in terms of energy. A bushel of corn costs about $6 and has 130000 kcal. Comparing the cost and energy content of substances:
- corn: 21000 kcal/$
- gas: 7100 kcal/$
- coke: 844 kcal/$
I can see why the biofuels people think that ethanol will be a hit. What would things be like if all fuel was produced agriculturally?
Land Use
Let’s assume that I’m on a 2400kcal/day diet. I need about 7 bushels of corn to provide all of my caloric needs for a year. (7 bushels of corn would also translate into about 200 pounds of chicken - yum!)
Current US corn production averages about 150 bushels per acre, so my slice of calories if I ate only corn could come from a patch of land 50 feet on a side.
Now let’s look at my car. Let’s say I drive 15000 miles a year, at 30mpg, for a total gas consumption of 500 gallons. This would take about 1.5 acres to produce depending on the method invoved, about 30 times the amount of land needed to produce what is needed to eat.
If we did this for all of the 240 million cars in the US, it would take about 400,000 square miles of productive land, about five times the size of Nebraska. Clearly this is a long way off.
Summary
Biofuels seem like an important piece of the energy puzzle, but it seems that they are only a partial solution to the energy problem. The real solution is to drive less and to live in such a way that we can meet our needs without moving around so inefficiently.