"Our greatest responsibility is to be good ancestors."

-Jonas Salk

Tuesday, November 3, 2009

'Tis not Mete. Or is it?

Well, my dog food calculations went awry, as Richard Reiss pointed out in the comments. I slipped a digit.

To recall, there have been recent allegations that having a dog does as much damage as driving a large SUV, on account of the carnivorous habits of the dog. Now there's some question as to how much of the damage due to meat should be attributed to the dog, but even given a proportionate impact by weight, I found at a rough cut that supporting the dog was the equivalent of driving the SUV no more than 5 miles per day. It turns out that my particular calculation was wrong by an order of magnitude, and that it has to be corrected, but it needs to be corrected AWAY from the calculations of Vale & Vale, in favor of the dog. Even fed a diet of sirloin, it appears that the dog's daily impact is on the order of driving about a half mile.

But this leaves me in a quandary. My prior result was in the same ballpark as Eshel & Martin's famous result that personal transportation and personal food consumption in the US are of comparable scale insofar as greenhouse gas impact is concerned. Counting the human as triple the dog, and the vehicle thus as driven 15 miles per day, seemed consistent with that estimate. But now I'm left at a loss, since the meat impact is now coming out as tiny.

And now here comes a Worldwatch white paper claiming that meat dominates transportation!

This level of confusion is ridiculous. How the hell are we supposed to cap and trade stuff that we have such a fuzzy grasp of?

Let's revisit the fuzziest numbers in my calculation. I erred by a factor of 10 in the power consumption of the vehicle going at 40 mph, which I took to be 10KW but was listed at 100KW. The first number seemed more plausible to me, but it;s easy to check. Let's suppose the vehicle is getting 20 mpg. Then it is consuming two gallons of gasoline per hour. Googling "energy per gallon of gasoline" is immediately successful, yielding US gallon = 115000 Btu = 121 MJ along with another handy energy conversion reference page. So I get 33,700 W, neatly splitting the difference between the small number I expected and the large number I should have used!

OK, now it's an extra factor of 3 in favor of the dog (compared with prior calculations). A dog eating ribeye steaks is worth about two miles of SUV travel daily; a human about six.

The per capita mileage in Martin & Eshel was 200 per week, supposedly compatable to human impact, so I have only a factor of five to make up. Still a bit awkward. (Update: And half of that comes back because most people aren't riding SUVs. As Marcus points out in the comments, some of that comes from my neglect of methane and nitrous oxide in the dietary impact. So maybe we are still in the irght ballpark.)

This past weekend I saw a presentation at the Texas Book Fair (at the State Capitol, an innovation for which I have Laura Bush to thank, of all people) on the subject of Texas barbecue as a repository of authentic rural Texas culture. I love Texas barbecue; not the famous places like the Salt Lick, but the still-authentic ones like Black's in Lockhart. It would be a real pity to have to sacrifice this oddly satisfying and evocative bit of authenticity to sustainability. It's just not the same with barbecuing a chicken. Never mind a tofu.

To be sure, there are real ethical issues with even the smallest bit of meat. I don't deny that for a moment. But the environmental ones are new, and they need to be properly calibrated. I'm afraid the numbers are all over the map.

I'm totally unconvinced that the impact of a dog compares to that of an SUV, even lightly driven. My latest calculation moves things a factor of three in further favor of the dog, although to be sure the dog cannot carry as much cargo. But I'd really like to pin down just how guilty I should feel when I bite into a Texas brisket sandwich. Are these pleasures of the blessed or pleasures of the damned? The estimates have way too much variance. This question has a real answer, maybe not within a factor of two, but surely within a factor of fifty!

Let's get quantitative. How many miles in an SUV is a piece of brisket worth? Surely I should feel more guilty that I drove my Prius the thirty miles to Lockhart than that I stopped there for supper?

Oh, yeah, I parked the Prius around the block.

You cain't really pull into Black's in a Prius. It's hoard to expline. Sort of a Tixes thang.

Update 12/31/09: Similar calculations here.


turboblocke said...

FWIW a 1983 Honda Civic CRX supposedly required 10 hp to travel at a steady 50mph.

Marlowe Johnson said...

An important point to remember in all of this is that the 'meat' that is used for dog food is not typically the variety that would end up on your table so from an LCA perspective it's debatable that you would attribute any emissions at all to it, since it could be argued that it is a waste product. If you accept this argument then you're dog is carbon neutral :)

marcus said...

"This level of confusion is ridiculous. How the hell are we supposed to cap and trade stuff that we have such a fuzzy grasp of?"

Well, the point of a market mechanism is that you _don't_ have to calculate the impact of a final behavior, it should automagically take into account all the myriad interconnections.

Having said that, of course, a problem still exists in that cap-n-trade and other market mechanisms don't cover the land-use change (LULUCF) emissions very well (or at all). But that's an accounting problem on the other end of the chain...

marcus said...

Also, did your "food" calculation take into account methane and N2O produced from agriculture? You had a "400 gallons of gasoline a year for a human's food intake" number, but I'm not convinced that captures the full lifecycle analysis.

(of course, you'd also want to take into account car manufacture, etc. etc., which is why full lifecycle analysis is not easy)

David B. Benson said...

I recommend buying a dog cart and using the meat-eating dog to pull you around. :-)

Michael Tobis said...

Marcus, I'm all in favor of market mechanisms, but some of the relevant terms here are biologically mediated.

Any tax or rebate would have to be estimated after the fact rather than simply levied at a high-capital fossil fuel point source.

the_heat_is_on said...

IIRC, there's ongoing research to quantify carbon fixation by forests and other natural sinks. This shouldn't be a serious problem.
On the topic of GHG emissions in food production those of us living in Argentina must cut our beef consumption (1, 2) I've already eliminated beef consumption in the week (using poultry and vegetable protein as substitutes) and only eat red meat on some weekends (3)

1- http://en.wikipedia.org/wiki/Argentine_beef
2- http://www.allcountries.org/uscensus/1370_per_capita_consumption_of_meat_and.html
3- http://en.wikipedia.org/wiki/Asado

Michael Tobis said...

I believe the Texas barbecue tradition is similar. In any case it is much influenced, like all of Texas culture, by Mexico.


Marion Delgado said...

I hope we can all learn from Super- and normal Freakonomics that just because one angle on a situation gives you (and the you in this case is Vale and Vale, but it can be any of us) an "aha" you can't take that to the bank until you've gotten feedback and critiques.

I was going to say that I'd not seen previous similar claims pan out re pets vs. SUVs, but I hadn't wanted to take the time to dig into it.

Even if their numbers were good, or yours weren't off, I have stated why they're off base, it's similar to why the ruminant methane is worse than transportation claim is suspect, even though its numbers are superficially accurate.

Also, marcus is spot on about the purpose of either cap-and-trade or a carbon tax. And about what is not covered/fixed by them.

ac said...

Depends how much the dog farts, doesn't it?

jules said...

a. rats are the best pets and since you're never more than 50 feet from one anyway, no significant impact on the planet keeping one in a cage, and they'll even eat the bones left over from the BBQ.

b. cycle to the restaurant, not cos of the planet but cos of balance = use the brisket to fuel the vehicle that takes you to the restaurant.

King of the Road said...

As a quick order of magnitude check, food is fuel for a dog, gas is fuel for a SUV. For a SUV getting 20 m.p.g. (I get 21 in my Land Rover LR3 but I'm eccentric, 10000 km/year at $3/gallon is $2.55/day in fuel.

Looking online, a dog should eat about 2% of its body weight/day, so a 50 pound dog should eat a pound of food per day. Mid-range quality dry dog food costs $1.25/pound So the dog eats $1.25/day in food.

This leaves out, of course, all manner of considerations of vehicle life cycle impacts (though I think it's safe to say that these are small compared to daily fuel use), infrastructure (though these impacts are amortized of the +/- 2*10^8 cars in use), etc.

But I'd say that it is a good indication that a medium size dog has about half the impact of a lightly driven SUV.

Michael Tobis said...

I suppose you can just measure impact in dollars as a first cut! But the whole reason we have a topic here is that the first cut doesn't work, and that many of the impacts are offloaded from the users of the resource to the non-users of it.

King of the Road said...

That's true for both though. I'm willing to multiply a car by two to account for "externalities" but the dog multiplier would not be one.

I think the closest you'll get is within a single digit factor anyway, even figuring my LR3 in Southern California vs. someone else's in Austin would yield different numbers.

Michael Tobis said...

I disagree. That's the whole point of thinking about things in terms other than dollars.

First, there's a presumption that the price of a thing to the consumer is the cost to the producer, as well as that the cost to the producer is the cost to the world. But never mind that for now.

Multipliers can be huge or tiny, and aren't even necessarily non-negative.

For instance, as others have pointed out, the dog can be seen to have negative impact by reducing the quantity of meat by-product that needs to be incinerated.

There's a lot of dairy cows out there. They don't live forever.

You have to calculate the impact on meat prices taking into account the elasticity of meat demand (and demand for other animal products and services) to do that right. I'd guess the impact of the dog is very small unless you actually feed the dog food that humans would compete for.

King of the Road said...

So... you think that, failing to sell animal by-products to the pet food industry, the meat processors would simply throw them away (i.e., incinerate them)? I'm not an expert on that industry but I suspect they'd be sold for use in a huge variety of other products from livestock feed to fertilizer to medicine to pretty much you name it. See here for more (somewhat disgusting) information.

But using information I gathered for my blog post here and looking just at energy, I'd estimate that owning a medium sized dog would use about 8*10^9 joules in total for feeding and the 10,000 km in a 20 mpg SUV would use about 5*10^10 joules, or about 6.25 times as much as the dog. These include "well to wheel" efficiency for the SUV and a ration of about 8.5:1 for the energy used in production to available for the dog.

So I'm sticking with more but less than 10 times more. But I'm very skeptical about a multiplier less than 1 for the dog - dogs have their own costs beyond fuel. For example, they need to be driven to the veterinarian, their waste needs to be disposed of, and most importantly, they drink lots of water.

And I like dogs.

King of the Road said...


You didn't slip a digit, the table to which Richard Reiss refers is incorrect. I demonstrated this in the original post. Obviously, cars vary, but 10^4 watts is definitely a better order of magnitude than 10^5 for a reasonable SUV at 40 m.p.h.


Michael Tobis said...

Well, I did slip a digit, because I was referring to the same table.

But I am pleased that I slipped the digit, because as you point out, the number I used was better than the number in the table. And I did check my 10^4 against other expectations.