By Alan McCrindle
The Take away – The most important variable in energy consumption and carbon dioxide production in food is in your hands – the way you cook your food is the major leverage point in the total food production-consumption system – are you cooking with the lid on the pot?
The Background – The Rise of Global food supply chains has people concerned that this is reducing sustainability and accelerating global warming by increasing carbon dioxide emissions and energy consumption
With the rise of globalisation it is no surprise that food production has been globalising too. Examples such as Salmon farmed in Canada and flown to China for processing before being flown to California have many people interested in sustainability and global warming up in arms.
One response to this concern, that globalisation of the food chain is contributing to a rise in energy consumption and carbon dioxide production, has led to the concept of food miles – the distance that food travels from where it was produced to where it was consumed. Local food production and local growers markets are also on the rise – in part driven by the desire to have fresher food that has lost less of its nutrients due to long travel times and cold storage.
The Reality – is that the majority of the energy consumed and carbon dioxide produced in the total food chain is produced by the consumer in cooking the food and driving to buy it
While one response is to feel relatively powerless against the perceived “monster of globalisation” for threatening our sustainability, it turns out that our intuitive analysis of the situation is in many cases simply wrong.
The fact is, that in the case of food that we buy and cook at home, we the people are responsible for the largest use of energy and production of carbon dioxide in the total food supply chain.
For some reason when most of us think about the energy used and carbon dioxide produced with food only think about it in terms of the food we buy in the shops – we forget about the energy that we use to get to and from the shops to buy the food, the energy we use when we cook the food (and wash the dishes) and the energy used in disposing the waste.
When we add these energy consuming stages into the equation to get a full “seed to waste life cycle analysis” it turns out that the major energy consuming steps in the chain are created by us driving to buy the food and cooking the food. And of these two cooking takes up the most energy. And this analysis excludes the energy cost of washing the dishes.
You can see this represented graphically in two charts I found on the internet that measure the total carbon footprint / energy consumption for potatoes and broccoli in the UK.
For those of you who aren’t that good with graphs, the vertical bars in each graph measure the total energy used / carbon emitted to deliver one kilogram of potatoes and broccoli to the plate at home. The different energy consuming steps in this process are represented by the different colours – the hights of each colour represents the amount of energy used in that stage.
As you can see if the case of potatoes, approximately 11 mega joules (M J) of energy is consumed getting a kilogram of potatoes to a cooked state. And when you look at the light blue part of the bar you can see that just over 4 M J – about 37 percent – is used by us processing the potato at home. And this excludes the cost of driving to buy the potatoes.
In the case of broccoli – the graph compares broccoli sourced from Spain and the UK. The vertical bars measure the amount of carbon dioxide produced in the chain and the light green bars – the biggest in all cases – represent the energy used at home. This varies from around 50 to 60 percent of the total carbon dioxide.
The bottom line is that you can save more energy and carbon dioxide emissions by boiling your potatoes with the lid on the pot than by buying local produce.
In terms of transport economics the car is the most energy intensive form of oil powered transport. A large ship can carry one ton of food 8oo miles on a gallon of fuel. In comparison a train can move the same ton 60 miles, a truck 20 miles and a car 10 miles. When you see these statistics it is easy to see why the cat of driving to the shops to buy food is a relatively energy intensive part of the food chain.