« May 2009 Table of Contents
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
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
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
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
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
"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
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
Transportation is only a small piece of the picture. The
production phase of a product accounts for 83 percent of the
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
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
population is depleted. This highlights a major
for seafood in a carbon-constrained
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
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
seafood purchasing efforts, says there is a lot of work to do
before the carbon information can be translated into
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
Carbon emissions can't be considered in a vacuum, she
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,