"Meating" CO₂ emissions

Recently, an article in The New Scientist "Just how much meat can eco-citizens eat?" by Sujata Gupta provides interesting reading for biology students.  Sujata makes a statement about the waste of animal biomass in the processing of the carcasses.

When we think about how much meat we consume, how many of us think about the rest of the animal?  

What happens to hair and skin of cows, sheep and pigs?

What happens to the feathers of chickens, turkeys and  ducks?

What about all the parts that don't look like meat?

In former days, when people consumed what they produced for themselves, there was no surplus and they ate everything they could while using the rest for tools or other materials.  In many parts of the world today, everything is still used.  In the industrial countries, where people are far removed from the animal processing, little may be recognized by the average person. Here is a good blog of people's suggestions about what is "not used".  Of course the economic nature of animal production, the producers cannot afford to waste so much biomass.

There is huge cultural issue in this.  What people in one country will accept to eat is not the same in another.  I remember seeing cartons from the US of frozen beef and pork kidneys, tripe and spleens in French Triperie stores ( triperie = tripe or in general offal). This is a great opportunity to bring the intercultural aspect of consumption of animal products and biology together.

Yet all these things take food and energy to produce as the animals metabolize and synthesize the proteins for the body parts.  As the animals live and grow, many of them, especially the ruminants, produce methane by the fermentation of cellulose. But keeping birds warm and growing, demands the use of a lot of energy which draws from fossil fuel power plants.  So greenhouse gases are produced as a function of animal husbandry.

The article provides some statistics about how much meat is eaten around the world.  Animal production is cited as producing 80% of all the agricultural CO₂ emissions which is not supported by the graphic above.  But interestingly, the proportion of methane produced by agricultural byproducts is significantly high.

The gist of the article is about how meat consumption is related to greenhouse gas production and whether the eco-conscious consumer can live on less meat.  Will those who can afford to buy and consume the animal products decide to eat less so as to reduce their impact on global warming?  What effect would this really have?

These issues can be raised in class discussion in topic 5 Greenhouse effect.  Additionally, this discussion applies to the pyramid of energy in topic 5 Communities & ecosystems with the energy provided to animals versus the energy received by the consumers, linking in the alternatives of choosing to eat meat or not to reduce wasting energy.  This then links in with option A Special issues in human nutrition and food miles.  How much carbon dioxide is produced just moving our food around?  What is our greenhouse impact based on the food we choose to eat?

I hope these ideas will generate lots of discussions in your classes!