I grew up on a cattle ranch, which means I ate beef for every meal. My plates included parts of a cow that would make most readers blush. Chicken might as well have been a vegetable.
When I left rural eastern Colorado, I was surprised to meet people who considered my family’s beef dependance not only unusual but also unethical. My college roommate, who also moved to Boulder from a cattle ranch, actually had tofu thrown at her because she wasn’t a vegetarian. Even the meat-eaters insisted on purchasing only grass-fed, organic beef. Talk about a culture shock.
The reasons for animosity towards omnivores range from trendiness to animal welfare, but often included an argument that meat-consumption is less environmentally friendly. There are at least two reasons cited for this. For one, the calorie conversion by animals, particularly cows, is not very efficient. That is, we get more calories out of eating the corn that a cow would eat than by eating the cow. Additionally, cows and other ruminants literally burp greenhouse gases (GHGs).
As I read an NPR article about cow belches, I found myself wondering whether adjusting the cow’s diet would reduce emissions. If rumination leads to GHG emissions, might strictly grass-fed cows be less environmentally friendly since they ruminate more? To find out, I took to twitter, and asked Amy Young, a staff research associate in a beef cattle genomics and biotechnology lab at UC Davis.
Amy responded with an extensive review of research comparing the carbon footprint of different protein sources, as well as a reader-friendly synthesis of these and other data into a consumer info handout by the primary investigator in Amy’s lab, Dr. Alison Van Eenennaam.
The simple answer to my question provided by these data is yes, cows on a strictly grass-fed diet produce more GHGs; however, the reasons behind my prediction might not be correct. Grass-fed beef, when compared with intensively raised, corn-fattened beef, have a higher emission to protein ratio because they spend more of their life out walking around burning off calories. Strictly range-fed beef take longer to get to market weight, which means more time spent burping methane.
But the issue gets more complicated. For cows fed corn, the environmental impact of growing the corn has to be taken account. If the cows are pasture grazed, then what type of pasture? If the cows feed on dry grasslands not useful for farming, and only eat forage, then there is no loss in terms of land use or wasted calories. But for cows fed on irrigated pasture as many of the happy cows in California are, water use has to be considered. And cows that live in colder states have to be fed bailed hay during the winter to qualify as grass-fed, which means farmland that could be used to grow food is growing feed.
Confused yet? Me too, but the major take home message is simple. There’s a huge range of environmental impact for beef depending on where/when/what/and how they’re fed. The same is true of every single prospective protein source, flora or fauna. Dr. Van Eenennaam summarizes this concept beautifully:
“There is no one sustainable source of protein, and depending upon the question that is being asked (e.g. carbon emissions/water use/land use/energy use per calorie/unit weight/unit protein), different food products will look like the “most sustainable” choice. There are also ethical and religious concerns around animal welfare and/or consuming meat and/or animal products (e.g. eggs, milk). Often there are direct conflicts between what is perceived as the most sustainable production system. Is it the one that best protects animal health/welfare, the one with the lowest environmental footprint per unit of product, or the most efficient? As with all dietary decisions there are tradeoffs among the various pillars of sustainability, and consumers will need to make the choices they consider to be best for their particular family values, budget, and circumstances.”
When it comes to making environmentally conscious dietary decisions in the United States, possibly the most important point to remember is that, regardless of our specific diets, most American’s consume way more protein than they actually need. Perhaps instead of focusing so much on which particular food sources are the most environmentally friendly, we should try to remember that everything we eat has some impact on the environment. Restricting total calorie and protein intake to not surpass what is essential is probably the single clearest dietary step the average westerner can take to decrease their environmental footprint.