Life cycle analysis in animal agriculture

In Reducing the environmental impact of farming, I talked about Nathan Pelliter’s work on Agricultural Life Cycle Analysis as a way to evaluate which farming methods have the least environmental impact. While the ideas apply to any type of farming (or really to the production of anything), his main work is actually on animal agriculture.

The return on investment of most types of animal agriculture is small compared to that of plant agriculture. For example, cattle require about 6 pounds of feed to produce 1 pound of muscle. All of the water, fertilizer, and pesticides required to grow 1 pound of plant material is thus multiplied by 6 to produce 1 pound of beef. Granted, it isn’t quite that simple, as parts of plants that aren’t used for human food can be fed to animals, but the point holds, even in organic systems.
Demand for animal protein is increasing rapidly both in developed and developing countries. This means that the amount of land used to produce food for animals will also increase. Some lands that aren’t suitable for plant agriculture may be better put to use as pasture land, but those areas can not possibly supply per capita demand for meat – more than 200 lbs per year per person in the US, according to the USDA (and that’s an average, theoretically factoring in the 3.2% of vegetarian and vegan Americans). This image from the University of Arizona concerning the uses of the US corn crop is a little old, but is essentially still true (and the story is similar for soybeans).

Ironically, many people condemn corn ethanol as wasteful and environmentally damaging but continue to consume animal products that account for a far higher percentage of the US grain crop – but that’s another story.

So, what are we to do? The planet would breathe a metaphorical (metaphysical?) sigh of relief if each person just ate lower on the food chain a few meals per week (see Nathan’s pictorial presentation Calories in Context). We’ve been told to reduce meat consumption for our health and for the planet, but it seems like no one is listening. Nathan’s response to the environmental degradation associated with animal protein production is to use LCAs to find which types of animal agriculture provide the most return on investment. At his seminar at Iowa State, I asked how his results can be used to influence consumer habits. We talked about possible taxes based on environmental impact so that food prices reflect the actual price to the environment, but we’ll leave that to the economists.

Nathan, along with Peter Tyedmers, wrote about LCAs in Biophysical accounting in aquaculture: insights from current practice and the need for methodological development, which was part of the FAO Fisheries document Comparative assessment of the environmental costs of aquaculture and other food production sectors. One of the most striking tables in the paper was a ranking of foods “by ratio of edible protein energy output to industrial energy inputs” on page 234. Intensive carp farming is by far the most efficient (when done properly, carp is even better than plants), while cultured shrimp grown in Thailand are by far the worst. Pastured beef is better than feedlot beef (barely), and industrial eggs are a terrible waste of inputs. See the full table at the end of this post.

Industrial energy inputs only tell part of the story, though, because they do not consider any negative outputs like waste or negative effects like spread of disease to wild populations. Ecological impact assessments also do not consider many effects. That’s why we need LCAs. According to the paper, LCAs frequently consider the following Impact Categories:

Impact Category Description of Impacts
Global Warming Contributes to atmospheric absorption of infrared radiation
Acidification Contributes to acid deposition
Eutrophication Provision of nutrients contributes to Biological Oxygen Demand
Photochemical Oxidant Formation Contributes to photochemical smog
Aquatic/Terrestrial Ecotoxicity Creates conditions toxic to aquatic or terrestrial flora and fauna
Human Toxicity Creates conditions toxic to humans
Energy Use Depletes non-renewable energy resources
Abiotic Resource Use Depletes non-renewable resources
Biotic Resource Use Depletes potential primary production
Ozone Depletion Contributes to depletion of stratospheric ozone

Nathan and Peter have focused on salmon farming, which can greatly benefit from LCAs. Production of feed is the most energy intensive and environmentally damaging aspect of aquaculture (and all animal agriculture). Replacing conventionally grown plant based feed with organic had a little effect, but replacing animal based feed with plant based has a huge effect. Some might say that we should just eat wild salmon instead, but again, the problem is demand. Wild salmon would be extinct if we tried to supply the current demand with them exclusively.

All of the options are complex, but two lessons of LCAs stand firm – reduce or eliminate synthetic nitrogen fertilizer (which can be done at least partially with genetic engineering), and decrease per capita meat consumption.

Food Type technology, environment, locale Protein Energy Output/Industrial Energy Input (percent)
Carp extensive freshwater pond culture, various 100 – 11
Herring purse seining, North Atlantic 50-33
Vegetable Crops various 50-33
Seaweed marine culture, West Indies 50-25
Chicken intensive, U.S.A. 25
Salmon purse seine, gillnet, troll, NE Pacific 15 – 7
Tilapia extensive freshwater pond culture, Indonesia 13
Cod trawl and longline, North Atlantic 10 – 8
Mussel marine longline culture, Scandinavia 10 – 5
Turkey intensive, U.S.A. 10
Carp unspecified culture system, Israel 8.4
Wild caught seafood all gears, marine waters, global average 8
Milk U.S.A. 7.1
Swine U.S.A. 7.1
Tilapia freshwater unspecific culture system, Israel 6.6
Tilapia freshwater pond culture, Zimbabwe 6
Shrimp trawl, North Atlantic and Pacific 6.0 – 1.9
Beef pasture-based, U.S.A. 5
Catfish intensive freshwater pond culture, U.S.A. 3
Eggs U.S.A. 2.5
Beef feedlot, U.S.A. 2.5
Tilapia intensive freshwater cage culture, Zimbabwe 2.5
Atlantic salmon intensive marine net-pen culture, Canada 2.5
Shrimp semi-intensive culture, Colombia 2
Chinook salmon intensive marine net-pen culture, Canada 2
Lamb U.S.A. 1.8
Seabass intensive marine cage culture, Thailand 1.5
Shrimp intensive culture, Thailand 1.4
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