IRA FLATOW, host:
This is Talk of the Nation Science Friday. I'm Ira Flatow. Up next, how what you eat affects greenhouse gas emissions. By now you've probably heard that you should eat locally. We're all out there trying to buy those locally-grown foods to cut down on the miles your food travels before it gets to your plate. "Locavores," as they're called, say eating food grown close to home cuts down on greenhouse gases that are (unintelligible) in the atmosphere when we fly grapes in from Chile, or we truck lettuce across the continent, or we ship water in from the South Pacific. That one drives me crazy.
But on a soon to be published paper, two researches from Carnegie Mellon University say you can have a much bigger, a much bigger impact on greenhouse gas emissions by switching your diet away from red meat and dairy, switching towards fish, chicken, and veggies. Christopher Weber is assistant research professor in civil and environmental engineering at Carnegie Mellon in Pittsburgh. He joins us by phone. Welcome to Science Friday, Dr. Weber.
Dr. CHRISTOPHER WEBER (Civil and Environmental Engineering, Carnegie Mellon University): Thanks a lot. Glad to be here.
FLATOW: I think we're a little shocked to hear that, you know, that shopping locally is not the answer.
Dr. WEBER: Well, it's, we've certainly gotten that response from a good few people that it was pretty surprising. And you know, I don't really know what to tell you.
(Soundbite of laughter)
FLATOW: But, tell me what you found. What did you find is, why if we switch to fish, chicken and veggies do we cut down on our greenhouse gases?
Dr. WEBER: Well, so essentially, what we were trying to do is look at all of the greenhouse gases that are emitted in both producing food and transporting it back and forth, all the way back through the supply chain. And basically, what we found is that people are very concerned about CO2 and CO2 is this big buzz word, but for agriculture and food products, actually, CO2 is only about half the story. And it's these non-energy-related greenhouse gas emissions caused by methane and nitrous oxide that are mostly related with meat production. And this is what makes meat look fairly bad compared to just eating grains, vegetables, and other products.
FLATOW: And they're very energy intensive? Is that what you're saying?
Dr. WEBER: Well, so actually they're - like, it's not related to energy at all. It is related to energy in that energy causes CO2. But one of the things that people have looked at in the past that have caused people to focus on this food miles concept is looking only at energy. But what we did was bring in these other non-energy related greenhouse gases. And they're so potent. They're you know, about twenty and 200 times the potency of CO2, that even though they're smaller quantities, they end up adding up quite a bit.
FLATOW: And that would be methane?
Dr. WEBER: Yes, methane, which is caused by manure management for the manure that's coming out our, all the animals that we're raising to make meat and dairy, and also nitrous oxide, that's associated with decomposing fertilizers and manure.
FLATOW: So it this, how shall I put it, is, these cows are burping or...
Dr. WEBER: Yes...
FLATOW: Or whatever we...
Dr. WEBER: A large share of the methane is due to what's called ruminant animals. These are the animals that have multiple stomachs and as they digest, they actually produce methane and coming out of both ends.
FLATOW: Passing gas on the other one.
Dr. WEBER: Passing gas and burping, yes.
FLATOW: And that's a lot of methane, you're saying.
Dr. WEBER: It is a lot of methane, actually, if you look over the life cycle of producing the cow for either dairy or beef, it turns out to be quite a bit. Yes.
FLATOW: And it would make a significant impact in greenhouse gas.
Dr. WEBER: Yes, yes, definitely.
FLATOW: Can you give us a figure on that?
Dr. WEBER: Yes, so, like in for example, in the life cycle of beef, we found that transportation, you know, where you're getting your beef from is a very, very small portion of the overall greenhouse gases associated with them. You know, like less than five percent. Whereas the methane that's associated with the manure and the burping and passing gas as you said, is something like 30 to 40 percent.
FLATOW: Wow. And I heard years ago that cows that are malnourished even pass more gas.
Dr. WEBER: Yes, and it - that is true. And one of the unfortunate side effects also is that people like to talk about eating grass-fed cow versus grain-fed cow, and how that will save energy because then you eliminate all the energy that it took to make the grains. But actually, cows that are eating grass as opposed to grain actually burp more methane than the cows that are not eating grain.
FLATOW: This is complicated, isn't it?
Dr. WEBER: It's very complicated, yes.
FLATOW: I mean, to figure out your footprint and which is better to do. Do we feed the cows the grass or feed the cows the grain, or you think you're doing one thing and then you do the calculations looking at it from a different angle and you come up with something else.
Dr. WEBER: Yes, exactly. It is really complicated and that's why you know, we were trying to be kind of all-inclusive and you know, we used these models that let us show all the greenhouse gases associated with the whole life cycle.
FLATOW: So you've come up with the solution and don't consider whether it's grain or grass. Just do away with the cow.
Dr. WEBER: Well, that's certainly what the numbers say, that you know, ruminant animals are no matter what's going on with how they're produced, they're always going to have this problem of burping and passing gas methane. If the manure is managed in a better way, then you can cut out the nitrous oxide and methane emissions there. You know, and if they're fed grass, then you can cut out the energy that's associated with that. But you're never going to get rid of the fact that you know, they're breathing methane, which is a potent greenhouse gas.
FLATOW: And is there any way to take the methane out of the manure so it doesn't go into the air?
Dr. WEBER: Yes, there certainly is. And this is one thing that if you do shop locally and you know your farmers, one of the advantages that, of shopping locally is that you can, you know, get to know the production practices of the farmers you're buying from. And one of the things to ask people is, are you currently capturing your biogas?
And what this means is when the manure is collected usually in the pitch or a lagoon, they can actually put a lid on the lagoon and catch the methane and then burn it to make like heat, to heat the farm. And so that's, you're not only eliminating the methane but you're also recovering that energy that's in the methane and then you won't have to use electricity.
FLATOW: That's quite interesting. And so where do you go from here? Are you going to look at other kinds of, is it methane you're going to concentrate on or other energy saving?
Dr. WEBER: Well, they're certainly doing any type of analysis like you said, like this is really complicated. And moving forward, we're hoping to be able to refine the study a little bit more, and look at some of the more interesting choices that people have like the whole organics versus local question is one that a lot of people like to think about. And of course, in terms of greenhouse gases, greenhouse gases aren't necessarily the reason people buy organic. But they do have an effect on greenhouse gases. So that's one of the things we want to look at going forward.
FLATOW: One last question. So let's say you don't want to go whole hog, so, maybe that's the wrong terminology, giving up beef altogether. Can you just, you know, wean yourself a little bit from the meat and could you have it just once a week and feel like you're making a contribution?
Dr. WEBER: Absolutely. Absolutely. And this is one of the things we were trying to tell people here is that, you know, this is not an all or nothing thing. This is something you can cut a little bit out of your diet. And we actually calculated this in the paper, and said that going all completely local, you would cut out something like four percent of the greenhouse gases in your diet. And you could do the same thing by just shifting one day per week away from red meat and dairy towards basically anything else, chicken, fish, eggs, or vegetables.
FLATOW: One day a week. Let's see if I can get a quick call in here from Helene in Palo Alto. Hi. Welcome to Science Friday.
HELENE (Caller): Hi. Thank you very much. I liked your comment about whole hog, (unintelligible) that pigs are not ruminant animals, and are actually are not nearly as bad as cows. But I did want to say that well, I developed a food carbon calculator. It's at eatlowcarbon.org. And we use a somewhat different analytical framework as what Professor Weber is talking about, but come to the same conclusion, that really, red meat, most red meats and cheese are really the big culprits here.
But we have also found that it's not an either/or situation. And certainly, if you're talking to vegetarians, that they can't do anything if you're just saying you know, get away from red meat. This really is a process of looking at our diets and saying what's healthy for us is also healthy for the planet, less red meat, less cheese, but also local produce. So for those who really want to work toward a more you know, a diet that is more reflective of these concerns, doing both is important, and is ultimately an investment in you know, future food that is inherently more sustainable and lowers greenhouse gas emitting over time.
FLATOW: All right, Helene, we'll go to eatlowcarbon.com.
HELENE: Dot org, dot-org.
FLATOW: Dot org, eatlowcarbon.org and take a look. Thanks for calling.
HELENE: Thank you.
FLATOW: And you're not saying, Chris, to do away with the local eating are you?
Dr. WEBER: Absolutely not, no. One, that's, you know we've gotten some kind of negative responses from proponents of eating local and you know, both me and my colleague, Scott Matthews, who are on this paper, we both buy locally. And there are many, many good reasons to buy locally including reducing the energy used to transport food. We just wanted to show that people have tended to ignore this dietary choices thing in favor of only buying locally. And like our caller said, it's important to do both.
FLATOW: Yes, as far as eating the meat, you said once, once a week. How much should we cut back in our dairy products?
Dr. WEBER: Well, that's, once a week in terms, one day per week of red meat and dairy, is how, is how the calculation came out. But red meat is even worse than your dairy products. So cutting out red meat once a week would be more important than cutting out you know, cheese once a week. But doing both is even better.
FLATOW: 1-800-989-8255. Let's go to Josh in Iowa City. Hi Josh.
JOSH (Caller): Hello.
FLATOW: Hi there.
JOSH: I'd heard several years ago about research to possibly use a vaccine or some kind of injection, I believe on sheep, to change the bacteria in their stomachs to produce less methane, but I haven't heard anything about that research since. Does your guest know anything about that?
Dr. WEBER: That's an excellent question. I've also heard things about that, but I'm not a geneticist, and I've never heard of certainly anyone commercializing something like that. I've - as far as I know, if it is still going on, it's definitely in the research phase.
FLATOW: Thanks for calling, Josh. Well, the cow has to have that stuff to digest the food, right?
Dr. WEBER: Yes. I'm not exactly sure how that would work scientifically.
FLATOW: Yes, so if you're saying if we take some of the cow out of the equation, we can cut back on the grass and everything else.
Dr. WEBER: Yes. The one thing people are looking into now is lab grown meat, which of course, would cut out the whole, the whole digestion problem if we're just going meat in test tubes though a lot of people aren't comfortable with that, of course.
FLATOW: We talked about that a few weeks ago. The idea that it, it wouldn't look, it wouldn't look like you think it's going to look.
Dr. WEBER: No, it wouldn't. It's true, but you know, interestingly enough, People for the Ethical Treatment of Animals has just, you know, put out that prize.
FLATOW: Yes, I know. We did that story. Thank you Christopher, for taking time to be with us.
Dr. WEBER: Yes, thank you.
FLATOW: Christopher Weber is assistant research professor in civil and environmental engineering at the Carnegie Mellon University, talking to us by phone. We're going to take a short break and go on to our next topic.
NPR transcripts are created on a rush deadline by Verb8tm, Inc., an NPR contractor, and produced using a proprietary transcription process developed with NPR. This text may not be in its final form and may be updated or revised in the future. Accuracy and availability may vary. The authoritative record of NPR’s programming is the audio record.