inefficient conversions and our food

Energy can be converted from one type to another, , but the process of moving from one specific type to another is usually inefficient.  Sunlight falls on green plants and photosynthesis does some chemistry that stores some of the energy in sugars (among other things) that animals and people can use.  The process is usually less than one percent efficient.  

We can eat the plants directly or we can eat animals that eat the plants.  The conversion process from plant to growing animal is also inefficient.  Not only is the animal inefficient at turning plant into animal, but food and animal must be transported.  The economics of farming attempts to optimize the growth rate of the animal - grow them fast and slaughter them as soon as possible, use foods that are optimized for growth, make sure they don't exercise too much, etc - but the process is still very inefficient.  (optimizing animal growth and lowering cost diminishes the quality of life of the animal too, but most people ignore that.  It is strange that the most energy efficient methods may be the least humane).

There are other problems when you make a lot of certain types of animals.  Some of them emit large quantities of methane - a green house gas that is much more potent that carbon dioxide.  Processing, refrigerating and moving the meat around adds other ocsts. The February, 2009 issue of Scientific American has a short article (online version here) that quantifies some of the environmental costs of eating different types of meat.  Beef is particularly bad (cows emit a lot of methane).

snip

Pound for pound, beef production generates greenhouse gases that contribute more than 13 times as much to global warming as do the gases emitted from producing chicken. For potatoes, the multiplier is 57.

Beef consumption is rising rapidly, both as population increases and as people eat more meat.

Producing the annual beef diet of the average American emits as much greenhouse gas as a car driven more than 1,800 miles.

You can work the numbers, but the average meat consumption of people in the US yields a greenhouse gas footprint by itself that is too large to stabilize greenhouse gases at current levels even if we stop using other forms of greenhouse gas emitting energy,  Moving to environmentally more friendly meats and eating less seems reasonable, but beef consumption is rising rapidly worldwide.

The FAO report Livestock's Long Shadow is referenced.  We've mentioned it here before.  Fascinating reading.  I have serious doubts people will make serious changes to their diets.  I have a difficult time dealing with more inhumane treatment of our food supply, but that is more efficient.  This may be a case where lower prices from efficiency increase total consumption and erase the benefits of lower emissions.

Comments

[Jessica]

I've heard contradicting opinions about whether grass-fed organic beef produces more co2 than factory corn-fed beef. Do you happen to know or have suspicions?

[Sukie]

It is a sad reality that sometimes what is best for one reason is worse for another. For example, there had been one study indicating that toddlers fed factory farm chicken were more likely to get infections, so it was expected that free range chicken would have fewer types of serious bacteria (though some things which infect young children are less of a problem for other humans). Well, the study that compared factory farm poultry with free range poultry found more diseases in the free range poultry. If I recall right the first study may have been one of the Slavic countries and the second in one of the Scandinavian countries. So, mixed results, but not a clear reason to figure that free range is automatically better in all ways.

It sure would be better if anything that was best in one way would be best in all ways, but life rarely gives completely clear choices like that.

There apparently is one way that life gives a pretty clear choice. I recently asked Steve if anyone had looked at how much increases in human intestinal gases offset the decrease in methane production by ungulates, and it sounds like enough work has been done to know that choosing a diet that is higher in vegetable food sources and when meat is eaten using poultry instead of ungulates as much as possible is helpful.

I personally get sick when I try to be entirely vegetarian, even with a balanced diet, as a decent number of people seem to do, but I have reduced my animal protein sources and the amounts, and that is good in many ways, plus I am more attentive to the types of animal protein and their amounts.

[Sukie]

Corn isn't a great food source, but grass is worse, and the more processing the animal has to do, the more methane will be produced. So, on the surface it appears that grass would probably be worse.

Ungulates have their own special modes of digestion.

Back when I studied primates we looked at diets of various ones. When there was leaf eating the animals concentrated on eating young leaves because those could be more easily digested by the symbiotic bacteria in the intestines (the source of much of primate gas, thank you very much) and the young leaves also turned out to contain more nutrients and less fiber.

So, I suspect that the amounts of gases measured from the free-ranging ungulates would vary across seasons with the lowest production in the Spring since the leaves would be young, less fibrous, and more nutritious.