AAAS: Climate-friendly dining meats
The carbon footprints of raising livestock for food
By Janet Raloff
THE FIRST OF TWO PARTS. Followup story is at: http://www.sciencenews.org/view/generic/id/40943/title/AAAS_Climate-Friendly_…
For the good of the planet, we’re all being asked to reduce our carbon footprints – the quantities of greenhouse gases, aka GHGs, associated with our actions. Since some 30 percent of the global warming potential attributable to society’s GHG emissions stems from the production of foods and beverages, menu choices are critical, noted Ulf Sonesson of the Swedish Institute for Food and Biotechnology in Goteborg, today. From this climate perspective, meat eaters are the big hogs.
Sonesson was one of the speakers on a panel titled “Food for Thought” at the American Association for the Advancement of Science annual meeting. This morning’s speakers shared data from largely new analyses on how foods, production techniques, and transportation affect the climate costs associated with our dining choices. And there were some big surprises.
No longer a surprise is the relative energy intensity associated with meat, especially beef. For instance, roughly half of the GHG emissions due to human diets come from meat even though beef, pork and chicken together account for only about 14 percent of what people eat.
From a climate perspective, beef is in a class by itself. It takes a lot of energy and other natural resources to produce cattle feed, manage the animals’ manure (a major emitter of methane, a potent GHG), get the livestock to market, slaughter the animals, process and package the meat, dispose of the greater part of the carcass that won’t be human food, market the retail cuts, transport them home from the store, refrigerate them until dinner time, and then cook the beef.
Tally the GHG emissions associated with all of those activities, Sonesson says, and you’ll find it’s the global-warming equivalent to spewing 19 kilograms of carbon dioxide for every kg of beef served. Swine are more environmentally friendly. It only takes about 4.25 kg of CO2 to produce and fry each kg of pork. At the other end of the spectrum are veggies. The climate costs associated with growing, marketing, peeling and boiling up a kg of potatoes, by contrast, is just 280 grams, Sonesson reported.
Another factor contributing to cattle’s particularly egregious carbon footprint is their relative fecundity, if you will, says Nathan Pelletier of Dalhousie University in Halifax, Nova Scotia. In her lifetime, a mother fish, particularly in protected aquaculture settings, may give birth to hundreds – if not thousands – of surviving offspring. A hen could certainly produce hundreds of chicks. Even a sow can give birth to eight piggies per litter. But a cow: She tends to issue a single calf every year for maybe 10. And while she’s in gestation and then waiting to become pregnant again, farmers have to care for her and perhaps a bull – which are both big, hungry manure factories.
Many environmentalists have argued that finishing up the fattening of beef cattle on corn is worse for the environment than cattle that are raised solely on pasture grass. Pelletier says his team’s analysis finds that at least from a climate perspective, the opposite is true. “We do see significant differences in the GHG intensities [of grass vs grain finishing]. It’s roughly on the order of 50 percent higher in grass-finished systems.”
When an audience member questioned whether he had heard that right, that grass-fed cattle have a higher carbon footprint, Pelletier reiterated, “higher. Yes.” The reason: “It’s related to the much higher volumes of feed throughput and associated methane and nitrous-oxide [GHG] emissions.” He added that most pastures were highly managed, and subject to “periodic renovations and also fertilization.” Finally, with grass-fed cattle “there is also a high [grass] trampling rate. So the actual land area that you need to maintain magnifies that [GHG] difference,” Pelletier said.
But what really concerns his team about the bonus GHG emissions linked to beef is the planet’s growing numbers – and appetite for meat.
Currently, although beef accounts for only about 30 percent of the world’s meat consumption, it contributes 78 percent of meat’s GHG emissions. Pork, at 38 percent of consumption, contributes only 14 percent of meat’s GHGs. Another 32 percent of the meat consumed worldwide comes from chicken, but getting these birds from farm to fork contributes only 8 percent of meat’s global carbon footprint. By shifting some share of beef and pork production to chicken over the next four decades, the increase in meat’s GHG emissions by 2050 might be held to just 6 percent higher than today, Pelletier said, even as the human population grows by another quarter-million each day.
Although meat’s overall carbon footprint is projected to grow only a little over the next 40 years, the global goal is to cut emissions in every sector. Pelletier offered some suggestions on how to do that. Some were considerably more appetizing than others.
For instance, substituting all beef production for chicken would cut meat’s projected carbon footprint by 70 percent, he said. Or perhaps per capita intake of meat could drop from a current average of 90 kilograms per year in the developed world to the 53 kg per person per year that’s been advocated as sufficient for human health by the U.S. Department of Agriculture. Under this scenario, Pelletier said, “I estimate that . . . we could reduce associated [carbon] emissions by roughly 44 percent.”
Swap half of that protein now supplied by meat with soy by 2050, and “you could expect [projected] emissions to decrease on the order of 70 percent,” he said. Take the next big step – eliminating all meat in favor of soy – should drop the protein-associated carbon footprint of Western diets a whopping 96 percent.
Pelletier described that the last scenario as “utopian.” Hmmm. Not for this carnivore. I’m willing to eat chicken much of the time and reserve beef as a big treat – maybe even to be downed only in small portions. But go solely soy? That’s no utopia to me.
That said, would I consider such a sacrifice for survival of the planet? Of course – but I’m hoping someone can shoot me recipes that would made this legume taste like something other than soy. So far I only have one, but it’s dynamite: for chocolate mousse pie.
Next up: What about fish?
AAAS: Climate-Friendly Fish
By Janet Raloff
SUSTENANCEI realized as I was writing this that the late lunch sitting beside my computer included salmon and other types of sushi.J. Raloff
If eating meat in place of other proteins hogs natural resources and spews an overabundance of greenhouse gases into the atmosphere (see last blog), wouldn’t fish be a climate-friendlier menu selection? Usually, but not always. Or so panelists pointed out this morning at the American Association for the Advancement of Science annual meeting, here in Chicago. Focusing on salmon, they showed that fish consumption’s carbon footprint depends on what a fish has eaten, how it has been caught and stored, and how it’s transported to market.
There were some real eye openers within these assessments.
Peter Tyedmers of Dalhousie University in Halifax, Nova Scotia, focused on greenhouse gas – aka GHG – assessments of fish production downstream of food-processing plants. In other words, how fish are reared and caught.
He started by focusing on the big North Atlantic and Chilean sources in Norway, Scotland, Canada and Chile. For every ton of fish harvested, there is a substantial GHG cost measured in terms of the amount of carbon dioxide that would produce equivalent warming. For production of Norwegian fish it’s 1,750 kilograms of CO2 equivalents, 2,250 kg for Chilean salmon, 2,500 kg for the Canadian fish, and 3,300 kg for Scottish farmed stock.
The difference in the warming potential largely traces to what the finned populations have been fed, Tyedmers explains. Scottish farmers feed their salmon the highest proportion of fish meal – almost 70 percent, on average. Those fishy diets account for 85 percent of the greenhouse-gas emissions associated producing Scottish salmon, his team calculated. Elsewhere, fish farming operations tend to substitute plant-based meals and oil or meat byproducts for a share of that fish meal.
Not surprisingly, the higher the proportion of plant sources in a farmed fish’s diet, the lower the climate impacts associated with its rearing.
So why are Scottish salmon fed so much fish? Some markets – particularly France – put a premium on salmon that were reared on fish, arguing that it makes the farmed animals more “natural” than those fed rapeseed or other plant products. Yet clearly, Tyedmers said, if the goal is to reduce our food supply’s carbon footprint, rearing salmon on plant-based feed is a promising tactic.
But just substituting any plant constituent for fish in a salmon’s diet will not always prove beneficial, he noted – at least from a climate standpoint. Some fish are fed fishmeal derived from capelin, which doesn’t have a large GHG contribution. If wheat gluten or even palm oil (which isn’t yet a normal ingredient in fishmeal) were substituted for the capelin, the carbon footprint of the salmon could jump substantially, Tyedmers team calculated.
Data from another assessment, this one in wild fish, showed that fuel use associated with harvesting gear could greatly impact GHG emissions associated with salmon. Purse seining contributed 180 kilograms of CO2 equivalent to the carbon footprint associated with a ton of salmon, gillnetting about 380 kg, and trolling a whopping 1,700 kg. So, do you know how your fish was caught?
Astrid Scholz, a food-production economist at Ecotrust in Portland, Ore., is part of an international consortium that is calculating GHG costs associated with getting salmon to market, independent of how they were raised. Again, there are some big eye openers here in the numbers that her team just crunched in the days leading up to this meeting.
Three-quarters of the world’s harvested salmon comes from three major markets: the Northeast Pacific (including Alaska and British Columbia), the Northeast Atlantic (mostly Norway and Scotland) and Chile. It turns out, her team finds, that the big climate costs for these fish trace to how they reach their designated market – by air, by container ships, or by truck.
And what determines the transport choice in most cases is whether the fish must arrive fresh (i.e. almost immediately), or whether it can arrive frozen at any point over many days or weeks.
In practical terms, for Chicagoans wanting fresh salmon, farmed fish trucked in from British Columbia will always have a smaller carbon footprint than salmon caught anywhere else – because all other fresh salmon must be flown into to the lower 48 states, especially inland cities.
If frozen salmon is acceptable, wild seine-caught Alaskan salmon will invariably prove the most climate-friendly choice at costs of 1 kg CO2 per kg of delivered fish, Scholz says. Although this fish has to travel nearly the same distance to market as will fish from Canada, the Alaskans’ wild foraging means there are no feed costs, which jack up the GHG costs associated with aquaculture.
Where frozen wild, seined salmon is not available, a climate-friendly alternative will be frozen farm-raised Norwegian salmon. Its carbon footprint: just 1.8 kg CO2 per kg of fish.
On a per dollar value, Chilean fish are usually the cheapest salmon in northern markets. But these monetary costs tend to disguise the high climate costs associated with moving South American salmon half-way round the world. There are 3 kg CO2 costs associated with each kg of frozen salmon brought to North America from Chile, and 5.5 times that GHG cost for fresh Chilean salmon flown into the Northern Hemisphere. Meanwhile, British Columbia salmon can be trucked in fresh or frozen for 3 kg of CO2 per kg of fish.
The problem for consumers, all of this morning’s speakers conceded, is that they don’t know any better than to choose their fish on the basis of dollar-cost or fresh-vs-frozen considerations. They certainly have no way of knowing how their fish were pulled from the water or what they might have been fed.This could be remedied by labeling, several of the speakers noted. Indeed, this approach to identifying climate costs associated with our diets is already being explored in a few European countries.
THIS WAS THE SECOND OF TWO PARTS: First part is at: http://www.sciencenews.org/view/generic/id/40934/title/AAAS_Climate-friendly_…