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Going Green: Carbon footprints revisited

Air freight doesn't always fly with sustainable seafood

By Lisa Duchene
May 01, 2009

Everything we produce, buy and eat is under scrutiny: Is it carbon-smart? Welcome to the carbon-constrained world, where averting the most severe effects of climate change means releasing far less carbon dioxide and other greenhouse gases.

The good news is that seafood's carbon footprint generally shines compared to red meat. When Christopher Weber, a research engineer at Carnegie Mellon in Pittsburgh, dug into the local-food, or "locavore," trend and the carbon emissions involved with food miles, he found that 
replacing a day's worth of red meat-based calories with chicken, fish, eggs or fruits and vegetables cuts greenhouse gas (GHG) emissions just as much as eating an all-local diet.

Red meat is on average 150 percent more GHG-intensive than chicken or fish, according to Weber and CMU researcher and co-author H. Scott Matthews.

But which seafood options offer the lowest carbon profiles?

Emerging scientific research shows general trends of how seafood production and transportation methods compare strictly on emissions of carbon dioxide and other GHGs. Conservationists who advise buyers and consumers on sustainable seafood are grappling with how to weigh that information with a myriad of other environmental factors and translate it all into advice on the most environmentally responsible seafood products.

From a strictly carbon point of view, fresh seafood shipped by 
air is the most GHG-intensive option. Carbon dioxide emissions for air freight are 3.7 times those for truck, 37.7 times (yes - that's nearly 40 times) those for rail transport and 48.5 times (nearly 50 times) those for ocean shipping by container, according to recent work by Weber 
and Matthews.

Already, U.K. super-retailer Tesco has placed an airplane on the label of all air-freighted products. CEO Sir Terry Leahy said Tesco added the airplane symbol "not as we did 20 years ago as a symbol of freshness, but as a basis for informed decision-making."

"In broad strokes, fish should swim, not fly," says Astrid Scholz, VP of knowledge systems at Ecotrust, a non-profit based in Portland-Ore., whose mission is to inspire innovation that represents economic gain, social equity and environmental well-being.

If there could be only one rule governing the carbon footprint of seafood, says Scholz, it would be: "A frozen product that's shipped is best and air-freighted fresh tends to be worst."

Transportation is only a small piece of the picture. The production phase of a product accounts for 83 percent of the average 
U.S. household's food consumption carbon footprint and transportation overall represents only 11 percent of life-cycle GHG emissions, according to Weber and Matthews.

So production is a critical 
part of the equation. Carbon profiles based on the production of various seafood products 
are emerging.

Ecotrust, Dalhousie University in Halifax, Nova Scotia, and SIK, the Swedish Institute for Food and Biotechnology, have partnered to research life-cycle 
analyses of wild and farmed salmon. A life-cycle analysis examines resource use and GHG outputs at every stage of production and disposal.

Peter Tyedmers, an associate professor in the School of Resource and Environmental Studies at Dalhousie, cautions against over-simplified answers. However, a picture is emerging from the group's research.

Generally speaking, seafood products that can be harvested or raised without feed have a lower carbon footprint than those requiring feed, says Tyedmers, so wild salmon is less carbon-intensive than farmed salmon.

For wild stocks, "one of the biggest factors that influences the amount of fuel we burn in catching them is their relative abundance," says Tyedmers. "So seafood from well-managed fisheries exploiting reasonably robust populations will generally have a lower carbon intensity than would be the case if the 
population is depleted. This highlights a major potential upside 
for seafood in a carbon-constrained world."

The reason, says Tyedmers, is that little can be done to lower the GHG emissions represented by raising beef. But as fisheries recover, the already low GHG profile of seafood will theoretically drop even lower.

Carbon footprints among wild fisheries also vary by harvest method. Preliminary data paints an emerging picture indicating purse seining is lower and trolling is higher in carbon dioxide emissions compared to other harvest methods.

For farmed salmon, the GHG emissions profile varies greatly, says Tyedmers, depending on how much fishmeal is used in 
the growing region. Scottish salmon is among the highest in carbon dioxide emissions because that growing region tends to use a higher portion of fishmeal in 
the feed. This early work indicates Norwegian salmon is lower in carbon dioxide emissions, compared to other farmed salmon regions.

According to Tyedmers: The more fishmeal in the salmon 
feed, the higher the GHG emissions; the more plant-based ingredients in the feed, the lower the GHG emissions.

But how does that all shake down into responsible purchasing options? Again, the research is emerging.

Heather Tausig, director of conservation for the New England Aquarium, which advises seafood buyers on their 
sustainable seafood purchasing efforts, says there is a lot of work to do before the carbon information can be translated into 
clear recommendations for seafood buyers.

"Certainly what we all don't want to do is simplify it so that it's not a clear picture of the energy costs," says Tausig. Energy consumption, life-cycle analysis and GHG are becoming another variable in determining the sustainability profile of a seafood product. Tausig and her colleagues are grappling with how to weigh that information along with the other factors like bycatch, habitat effects and abundance of fish stocks.

Carbon emissions can't be considered in a vacuum, she says.

So for now, a product-by-product approach seems wise as carbon dioxide emissions are 
tallied and figured into the overall sustainability profile of seafood options.


Contributing Editor Lisa Duchene lives in Bellefonte, Pa.


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