Sunday, January 21, 2007

Baking Vs. Buying Bread

What is more environmentally sound: baking your own bread or purchasing a loaf of bread baked in an large bread factory? The answer might surprise you.

In this Life cycle assessment of bread production report (starts on page 9), the authors estimate that producing a 1 kg loaf of bread takes, from growing in the field, to milling, to baking: (values are approximate based on my deciphering of the image at left) 4.4 MJ of energy from a large bread factory, 6.2 MJ for a bakery and 8.2 MJ for baking at home in a bread maker. It takes almost twice as much energy to bake the loaf at home and CO2 emissions correspond with the amount of energy used.

Why is this?

The baking process was the most energy-consuming step of the entire bread production process accounting on average for 64% of the total energy demand. The baking process using a domestic bread maker requires 3 times more energy than in a factory and in the bakery, energy demand is still twice as high than in a large bread factory. Due to the close correlation between energy demand and greenhouse effect the same applies to the greenhouse effect as well.
The industrial sized stoves in a large bread factory use energy much more efficiently per loaf of bread produced then a bread maker at home. Due to this greater efficiency in energy use, purchasing a loaf of bread made in a large bread factory is more environmentally sound than baking a loaf at home.

Of course, depending on how far away the store is and how much you purchase, the energy used by your car to transport the bread can be greater than that used to make it.
In contrast to the transport on foot or by bicycle, which involves zero, respectively negligible emissions and demand of energy, the extreme case of a 4 km car transport, with the sole purpose to acquire 1 kg of bread, will entail an energy demand of 18.6 MJ and the emission of 2.2 g SO2–equivalents. That means the energy demand due to the bread transport is 4 times higher and acidification is 2.5 times higher than that caused by the entire preceding bread production chain (conventional crop production assumed).
This report now makes me wonder, which uses less energy: TV dinners or making your own meals? I will have to look into that.


Angela said...

Thanks for the article. I wonder how much difference it makes to make one's own bread from locally grown grain (where available) as opposed to buying bread made who-knows-where. I suppose the important thing when deciding whether to buy a breadmaker is to find out where the raw materials from the bread at the supermarket come from.

Fat Knowledge said...

Glad you liked it, Angela.

I don't think it makes a whole lot of difference as to how far away the grain comes from, as sending flour in bulk doesn't take that much energy (comparatively speaking). If you click on the image in the post, you will see the contribution of transportation to the overall usage of energy and it is not high.

I would recommend that you focus instead on walking or riding a bike to the grocery store> If you can't do that drive to the closest store and shop as rarely as you can. Odds are you will save more energy shopping locally than buying local.

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