Discovery News: Environmental

Organic Motivations

CNN carried a story about a study concluding that organic produce does not contain more nutrients than the same five fruits and veggies (carrots, kale, mature peas, apples and potatoes) conventionally grown.

That is certainly a bummer for the organic food industry, which would no doubt like to make nutrition claims about the food. But, Michaeal Pollan, in The Omnivore's Dilemma, cites a similar 2003 UC Davis study that found corn, strawberries and blackberries grown organically had more vitamin C and polyphenols than conventionally grown ones in neighboring plots. So, does it vary from plant to plant, place to place, or is something else going on?

More to the point, I don't think most people buy organic food because they believe it has more vitamins. I think they do it because they don't want to risk eating food with any pesticide residues. They may also do it because they want to reduce the amount of pesticides and petrochemical fertilizer entering the environment, or because they want to support agricultural practices in which the workers aren't exposed to such chemicals.

As with so many things, though, organic farming is not an across-the-board win. Sigh. The CNN story mentions a 2006 report by the University of Manchester Business School investigating the environmental impacts of food. While organic food used less pesticide, the land requirements were often greater--presumably because the crop yield was reduced.

The energy requirements for organic milk were less than conventional, but the land use was greater, and the greenhouse gas emissions per gallon were higher for organic. And, according to the study summary, "organic wheat production has higher impact than non-organic," mainly because its eutrophying emissions are higher.

This is just one example of why shopping these days is such a paralyzing experience: when choosing which apple to buy becomes a trade off between deforming the local frogs or drowning the polar bears, it feels easier to go hungry.

Fortunately, Consumer Reports offers some advice on which fruits and veggies are worth buying organic--at least from a pesticide perspective.

(Image: Flickr user Scoobymoo. Some rights reserved.)

Meat, Meat, Meat

The take home message from everyone I’ve been speaking with recently is that meat--especially beef--is just no good for the environment.

First, Christopher Weber at Carnegie Mellon University published findings showing that shifting a quarter of the average American’s red meat consumption to other foods saved as much greenhouse gas emissions as going entirely local, i.e. red meat has a really big carbon footprint.

Then, I spoke with researchers highlighting the importance of considering our “nitrogen footprint”, too. “Meat is one of the main drivers of acceleration of the cycle,” said Alan Townsend of the University of Colorado at Boulder. “To have meat diets under modern agriculture takes a lot of nitrogen. You end up having to have a lot of fertilizer and a big chunk of field to grow a few cows or pigs.”

Finally, the Stockholm International Water Institute issued a report about water… You guessed it: meat production takes lot of water. Their report estimates that about 50 percent of calories grown in fields never make it to the table, and about half of that loss is animal feed that doesn’t end up as a calorie on a cow, pig, chicken, or other edible critter. Growing those lost calories takes a lot of water.

For the most part, each of these impacts comes from the same cause: growing a pound of meat requires (much) more than a pound of grain. A pound of beef, for instance, requires eight. (The conversions are better for other types of meat, but never 1:1).

This inefficiency amplifies the demand for nitrogen fertilizer and irrigation, and leads to more of the greenhouse gas emissions associated with growing crops. These emissions come from energy for making fertilizer and release of nitrous oxide (N2O)—a super greenhouse gas almost 300 times more potent than CO2—by bacteria acting on fertilizer in the soil.

With cattle, greenhouse gas emissions also result from methane (23 times more potent than CO2) released by digestion, and nitrous oxide production from manure. 

The SIWI report points out that demand for meat is rising fast. Here are some meat consumption numbers for different parts of the world:

--Southeast Asia: ~88 lbs/person/year in 2002, a sevenfold increase from 1961, when it was 13 lbs.
--India: Projected at 22 lbs/person/year in 2050 (Thanks to a largely vegetarian population.)
--China: Projected at 183 lbs/person/year in 2050
--US: 200 lbs/person/year in 2005, up 22 lbs from 1970

It’s also worth pointing out that dairy creates these impacts, too, though not to the same extent as meat.

Is Grass-Fed Beef Better?
So grain-fed beef is no good… but what about grass-fed? If you read Michael Pollan’s book, The Omnivore’s Dilemma, you might have been convinced, like me, that eating a bit of grass-fed beef was fine--even good. When cows eat grass, they’re converting plant calories that we can’t eat (i.e. grass) into calories that we can. This is an efficient way to harness the energy from the sun in food form in places that aren’t suitable to grow crops.

But, how much does the greenhouse gas footprint change when you switch to grass-fed beef? Then you don’t need those eight pounds of grain. Christopher Weber kindly did some math to help answer this question (Thanks, Christopher!). He cautions that these numbers are approximate and un-reviewed, but here they are:

“By switching to grass fed, you remove around 20% of the CO2 and 60% of the N2O in the supply chain of making and delivering grain to the farms.
So, if there is no increase in methane and manure emissions (of CH4 and N2O) are not being captured at the feedlot, there's approximately a 25% reduction in life cycle greenhouse gas emissions in grass fed vs. grain fed.”

But don’t stop reading. Studies have shown that grass-fed beef produces more methane than grain-fed beef. (Though at least one study has reported the opposite, Weber said.) This offsets some of the gains:

“If the grass-fed has 15% more methane, which is around the number I've seen cited, then grass fed is only 20% better.”

So, while there may be other advantages to eating grass-fed beef over grain-fed, it’s still not a climate-neutral choice. And, as Marshall Burke of Stanford University pointed out, if everyone switched to grass-fed beef, there wouldn’t be enough pastureland to go around.

To the climate conscious: learn to love lentils.

(Photo: Grant Hutchinson)