16 September 2010
While my initial requirements for food were; eating locally and organically (to avoid long-range transportation and petroleum-based fertilizers), I've come to understand that food is also a huge energy user.
This article (Energy Use in the U.S. Food System, by Patrick Canning, Ainsley Charles, Sonya Haung, Karen R. Polenske and Arnold Wasters, ERR-94, USDA Economic Research Service, March 2010, available at
www.ers.usda.gov/publications/err94) is an interesting introduction to the huge amount of energy is used in food every year from; agricultural machinery and fuel for these machines, transportation of food, food processing, food packaging, ovens, stoves, microwaves, home appliances, and even down to the cookware used to make food.
As the article states, "In 2007, the U.S. food system accounted for almost 16 percent of the Nation's energy budget." and "Between 1997 and 2002, over 80 percent of the increase in annual U.S. energy consumption was food related." They identify three main reasons why-even as other energy use has remained stable-food related energy has increased so dramatically.
(1) Population growth has accounted for 25% of food-related energy use. Our nationwide population has grown by more than 14 million in give years from 1997 to 2002. More mouths to feed.
(2) While there has been a greater proportion of foods that used less energy (fresh produce, fish...) purchased over energy-intensive processed foods, this change came with a "substantial increase in food marketed per capita to U.S. consumers) People are eating more food.
(3) We are using more energy-intensive technologies which account for about half of the increase in food-energy. "Businesses faced with increasing labor costs, while energy prices were lower...A shift from human labor to energy-using equipment occurred for all food and food-related commodity groups." More and more household are adopting labor-laving technologies to save time preparing food and cleaning it. "In 1985, 18-64 year olds spent an estimated average of 49 minutes on cooking and cleanup per day. Dureau of Labor Statistics' data indicate average cooking and cleanup times per household fell to 31 minutes per day in 2008."
I wanted to analyze the energy it takes to produce one loaf (1 kg) of bread with various at home methods and industry methods. This first chart shows an energy comparison of only the BAKING energy used (in kWh) for 4 different scenarios: Quick bread (tortillas from earlier post), Bread machine, Manual kneading+Oven baking (at 350 degrees for 1 hour) and Industrial baking.
As you can see, cooking in the oven actually uses more energy (2 kWh) than industrial baking (.7 kWh). This is due to the high volume of bread being made in industrial kitchens. Baking is only a small part of the energy it takes to create a loaf of bread, however. What is interesting, is a comparison of the TOTAL energy it take to create this loaf of bread, looking at all stages of its life cycle. I used this article (
Andersson, K., and T. Ohlsson. (1999) “Life Cycle Assessment of Bread Produced on Different Scales.” International Journal of Life Cycle Assessment 4(1): 25-40.) for my numbers.
The two scenarios I looked at in this chart were an 'Industry' produced loaf of bread (example Sara Lee or Pepperidge farm), versus a 'Home' scenario which ingredients are bought in bulk, and are all local.
_'Consumer phase' refers to how much energy it takes to operate the shopping side of obtaining the bread (grocery store lighting and heating etc),.
_'Packaging phase' is limited in my 'home' scenario because I am buying everything in bulk, there is still a small amount of packaging which food is in when it arrives at the store.
_'Transportation' phase is also limited in the 'home' scenario because I am buying all ingredients locally
_'Food Processing' phase refers to the amount of energy it takes for all processing and baking
_'Agriculture' phase is the same for both scenarios because they are using the same ingredients.
In the end, the 'Industry' scenario used
3.61 kWh to produce one loaf of bread and the 'Home' scenario used
2.02 kWh. The
1.59 kWh saved for each loaf of bread comes from the decreased travel distance (local ingredients) and the lack of packaging (bulk foods).
I also read the following articles when researching this, both very interesting:
Life Cycle Assessment (LCA) of the Production of Home made and Industrial Bread in Sweden
http://www.infra.kth.se/fms/utbildning/lca/projects%202006/Group%2003%20(Bread).pdf
Life-Cycle Based Sustainability Indicators for Assessment of the U.S. Food System:
http://css.snre.umich.edu/css_doc/CSS00-04.pdf
Its been raining quite a bit this week. The other night the rain was pelting so hard it felt like hail. I have to do more laundry when it rains because all the junk off the street gets all over my clothes. 
