Locavore or
vegetarian? What’s the best way to reduce climate impact of food?
November 25, 2015 4.02pm EST
AuthorElliott Campbell
Associate Professor, Environmental
Engineering, University of California, Merced
This year’s
Thanksgiving feast falls only a few days before the start of the global
climate summit in Paris. Although the connections are not always
obvious, the topic of food – and what you choose to eat – has a lot to do with
climate change.
Our global
agriculture system puts food on the table but it also puts greenhouse gases
(GHG) in the air, which represent a huge portion of global emissions. GHG
emissions come directly from farms such as methane from cows and nitrous oxide
from fertilized fields, while other emissions come from the industries that
support agriculture, such as fertilizer factories that consume fossil fuels.
Still other
emissions come from natural lands, which have massive stocks of natural carbon
stored in plants and soils. When natural lands are cleared to make room for
more food production, the carbon in those natural pools is emitted to the
atmosphere as carbon dioxide.
Adding all
these emissions together makes agriculture responsible for between roughly one fifth and one third of
all global anthropogenic, or mandmade, greenhouse gas emissions.
How can these
emissions be reduced? My own research through the University of California Global Food Initiative has
focused on evaluating a wide range of factors from biofuels to local food
systems.
Undoubtedly,
broad emissions reductions must come from political action and industry
commitments. Nevertheless, an enlightened consumer can also help achieve
meaningful reductions in GHG emissions, particularly for the case of food. The
trick is to understanding what food means for your personal carbon footprint
and how to effectively shrink this footprint.
On par with electricity
Zooming in from
the global picture on emissions to a single home reveals how important our
personal food choices are for climate change. You can use carbon footprint
calculators, such as the University of California CoolClimate
Tool, to get an idea of how important food is in relation to choices
we make about commuting, air travel, home energy use, and consumption of other
goods and services.
For the average
U.S. household, food consumption will be responsible for about the same GHG
emissions as home electricity consumption for the average
US household.
Measuring the greenhouse gas
impact of different foods is complex but in general, it’s commonly agreed that
plant-based diets have a lower carbon footprint. davidwoliver/flickr, CC
BY-NC
That’s a
significant portion of an individual’s GHG footprint but it could be seen as a
blessing in disguise. While you may be stuck with your home or your vehicle for
some time and their associated GHG emissions, food is something we purchase
with great frequency. And every trip to the grocery store or farmer’s market is
another opportunity for an action that has a significant and lasting impact on
our climate.
Making concrete
decisions, though, is not always straight-forward. Many consumers are faced
with a perplexing array of options from organic to conventional foods,
supermarkets to farmers markets, and genetically modified organisms to more
traditional varieties.
And in truth,
the carbon footprint of many food options is disputed in the [scientific literature](http://www.researchgate.net/publication/227418948_Where_are_the_best_opportunities_for_reducing_greenhouse_gas_emissions_in_the_food_system_(including_the_food_chain).
Despite the need for more research, there appears to be a very clear advantage for
individuals to chose a more plant-based diet. A meat-intensive diet has more
than twice the emissions of a vegan diet. Reducing
the quantity of meat (particularly red meat) and dairy on the table can go a
long way to reducing the carbon footprint of your food.
Food miles and water recycling
Local food
systems are popularly thought to reduce GHG emissions through decreased food
transport or food miles. But in many cases food miles turn out to be a
meaningful but small piece of the overall GHG emissions from food.
For example, a
broad analysis of the US food supply suggests that food miles may be
responsible for less than 10%
of the GHG emissionsassociated with food. This general trend
suggests that where you get your food from is much less important than
first-order issues, such as shifting to a more plant-based diet.
A little-appreciated way of
reducing the carbon footprint of food is to recycle nearby water rather than
pump it long distances. The Pajaro Valley Water Management Agency (PVWMA) Water
Resources Center in California sanitizes wastewater for direct use or blending
with ground (well) water. US Department of Agriculture, CC
BY
Where, then,
does this leave a rapidly emerging local food movement?
For starters,
there are some cases where food miles have greater importance. For example,
food miles can play a big part in the carbon footprint of foods when airplanes
or refrigeration are required during transport.
There is,
however, untapped potential for locally produced food to deliver carbon savings
around water and fertilizers.
When water is
pumped long distances, it can add to food’s carbon footprint. Re-use of
purified urban wastewater for irrigating crops represents one strategy for
addressing this challenge but is only economically and environmentally feasible
when food production is in close proximity to cities.
Using fossil
fuels to produce fertilizers, such as ammonia, can also be a big piece of the
carbon footprint of food. Nutrients in reclaimed wastewater and urban compost
may provide a low-carbon alternative to fossil fuel-based fertilizers. But
similar to water re-use, reusing nutrients is most easily done when there is a
short distance between food production and consumption.
To be sure, buying
local food doesn’t imply that food or nutrient recycling has happened. But
developing local food systems could certainly be a first step towards exploring
how to close the water and nutrient loop.
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