Tuesday, April 14, 2015

Vegetarians use... similar water

The Los Angeles Times has the best tool that I've yet seen for understanding the amount of water used in agriculture.  It lets you put together various proteins, starches, vegetables, and drinks to make a typical dinner, and shows you how much water it takes to produce all those things.  Check it out.

The lowest water-use dinner I could come up with took 135 gallons of water to deliver two eggs, carrots, potatoes, and a glass of beer.  Most dinners are vastly more than that.  The biggest takeaway here is that each person in my family of five uses more water in the food we eat than we use together for the house and back yard.

[Edit: unfortunately, the LA Times article has a serious error, which I made as well in my original version of this post.  They confounded the dry and as-eaten (boiled) weights of peas, lentils, and chickpeas.  This leads to a very large overestimation of the water used per protein delivered.  I have corrected this error in the content and tables below.  Big thanks to Miciah Masters for finding the problem!]

The biggest consumers of water are all proteins: beef, lamb, and pork.  For most meals the protein consumes way more than half of all the water.  I was quite surprised to see that chicken eggs and meat, and goat meat, are about as efficient as vegetarian stables like peas, soy, chickpeas, and lentils.

Arjen Hoekstra, the founder of Water Footprint Network, has spent years researching agricultural water use.  One of his messages is that "animal products demand considerably higher amounts of water than do most other food types."  (Quote of Mr. Hoekstra from LA Times.)  This makes intuitive sense, because animals consume and do not produce protein and carbohydrates.  If you ate the stuff that the animal eats instead, that would have to be a more efficient way to get those proteins and calories than by eating the animal.

But people, even vegetarians, don't eat the stuff we feed animals.  We feed animals cheap vegetables (like grass and grains and corn mash left over from making ethanol), and eat the expensive ones (like carrots and blueberries) ourselves.  Mr. Hoekstra is correct that many animal products demand more water than vegetarian products.  But that's not true of poultry in particular, and it's important to note that chicken is more popular in the U.S. than beef.

This is great news, of course, since it's far easier for most people to eat more chicken and less beef, than it is for them to switch to a vegetarian diet.  It does somewhat skewer Mr. Hoekstra's underlying goal of motivating vegetarianism, but of course that's the danger of working with real data.

So here's my analysis.  The water usage that the LA Times quotes are for an 8 ounce serving of all the various protein-rich foods.  As you might expect, beef has a lot more protein in it than the same amount of lentils.  If I correct the serving size to get the same amount of protein in all servings, the ranking comes out like this, from best to worst:

FoodServing SizeProtein contentFat contentCarb contentWater Used
Peas36 ounces56 g (224 cal)4 g (38 cal)147 g (588 cal)112 gallons
Chicken8 ounces56 g (224 cal)29 g (259 cal)0 g (0 cal)131 gallons
Eggs16 ounces56 g (224 cal)47 g (420 cal)6 g (22 cal)193 gallons
Soy burger12 ounces56 g (224 cal)19 g (168 cal)42 g (168 cal)254 gallons
Chickpeas22 ounces56 g (224 cal)19 g (168 cal)187 g (747 cal)278 gallons
Goat7 ounces56 g (224 cal)19 g (168 cal)0 g (0 cal)282 gallons
Lentils22 ounces56 g (224 cal)0 g (0 cal)127 g (509 cal)294 gallons
Milk (1%)60 ounces56 g (224 cal)17 g (151 cal)84 g (336 cal)359 gallons
Pork9.5 ounces56 g (224 cal)15 g (139 cal)4 g (16 cal)394 gallons
Lamb5.5 ounces56 g (224 cal)48 g (432 cal)0 g (0 cal)465 gallons
Beef8 ounces56 g (224 cal)33 g (298 cal)0 g (0 cal)850 gallons
Almonds9 ounces56 g (224 cal)126 g (1134 cal)56 g (224 cal)1097 gallons

I've added almonds to the table (using Mr. Hoekstra's data again), as they are rich in protein, use a lot of water, and are getting a bad rap in California for their water use right now.  I've also listed fat and carb calories.  For those of us trying to get to a low-carb, high-protein diet, soy and maybe milk look okay but these other veggie options are not great.

Farmers, of course, don't directly care how much protein their products have, but rather how much profit can be made from them.  I wasn't able to get profit numbers, but some quick Googling came up with the following prices.  If a farmer and his inputs are constrained primarily by water, then poultry farming looks like a good way to go, and once again vegetarian staples appear to be a terrible choice.

FoodWater UsedFarm PricePrice per gallon
Eggs1566 m3/tonne$1.90/pound1.013 cents/gallon
Goat5521 m3/tonne$5.25/pound0.794 cents/gallon
Pork5508 m3/tonne$4.06/pound0.615 cents/gallon
Chicken2218 m3/tonne$1.54/pound0.579 cents/gallon
Beef14191 m3/tonne$5.65/pound0.332 cents/gallon
Peas1979 m3/tonne$0.70/pound0.295 cents/gallon
Lamb13007 m3/tonne$4.28/pound0.275 cents/gallon
Milk796 m3/tonne$0.21/pound0.220 cents/gallon
Lentils5874 m3/tonne$0.90/pound0.128 cents/gallon
Almonds16095 m3/tonne$2.00/pound0.104 cents/gallon
Soybeans2145 m3/tonne$0.23/pound0.089 cents/gallon
Chickpeas4177 m3/tonne$0.29/pound0.058 cents/gallon

It's worth mentioning that tap water in California goes for about 0.55 cents/gallon.  If farmers paid for water what I pay, most would stop farming.  On the other hand, if most residential water users were charged similar rates to farmers, most would stop conserving water.  Things are pretty out of whack.

Prices aren't profit, and California farmers aren't all water constrained.  In many places they can pump unlimited (or more precisely, unregulated) amounts of groundwater.  In particular, there has been a trend in California of dairies converting to almond orchards.  The second table above suggests this is exactly backwards if those products have similar profit margins and are water limited.  California farmers are making the move because profit margins on dairy are smaller than almonds and they are not limited by water.