54 | New Scientist | 17 August 2019
Beef with tofu
From an environmental perspective,
is it better to eat imported foods like
tofu, quinoa and sweet potato or
beef from the farm a few kilometres
up the road?George Monbiot
Oxford, UK
This question is easy to resolve. In
a paper in Nature last year, a team
led by Timothy Searchinger of
Princeton University examined
the impact of various foodstuffs in
terms of carbon. This shows that
protein from beef is 73 times
worse than protein from soya.
A kilogram of beef protein has
the equivalent carbon emissions
of a passenger flying from London
to New York and back. The overall
carbon cost of 1 kilogram of beef
protein is equivalent to 1250 kg of
CO2. Aircraft emissions for long-
haul flights are roughly 110 grams
per passenger per kilometre, and
the return distance is 11,170 km –
so 1229 kg of CO2.
In discussing the carbon costs of
food, we have greatly exaggerated
the role of transport and greatly
downplayed the impacts of land
use. With the exception of food
that is flown, transport tends to
constitute a small proportion of
the total carbon cost. The crucial
environmental task is minimising
the area used by farming. Beef is a
highly inefficient use of land. Soya,
grown in prime sites, is a very
efficient use of land – though not
without its own major problems.
It is also worth noting that there
might be more soya in your steak
than in your slab of tofu, as the
great majority of the world’s soya
is grown for animal feed, and
conversion efficiencies (especially
when producing beef) ensure
that you need to pump far more
protein into an animal than you
get out. So even if you want to eat
less soya, you should eat soya.Ann Bliss
London, UK
From an environmental point
of view, meat from any source is
definitely a non-starter (or main).The question was asked by
someone in Suffolk in the UK.
There happens to be a quinoa
grower there, as well as others
around the country. I stopped
eating imported quinoa when
I found out that the cost of this
staple had gone up prohibitively
for the Peruvians because it was
being exported to Europe.
Swedes can be substituted for
sweet potato. As for tofu, soya
beans are grown in Norfolk in the
UK and go into tofu sold in outlets
in Norwich as well as online. We
don’t have to make compromises.
Just buy locally grown, seasonal
foods. You won’t go hungry.Michael Le Page
London, UK
A lot of people think local is better,
but this isn’t true for producing
meat and often even for crops.
When crops are grown in heated
greenhouses with extra lighting,
the carbon dioxide emissions can
be several times higher than those
from transporting the producethousands of miles. So-called
vertical or indoor farming,
which is promoted as being local
and eco-friendly, is especially
bad because it typically relies on
artificial lighting.
Proponents say the lights can
be powered by renewable energy.
But this would require an area of
solar panels at least 10 times larger
than that to grow the crop.
Louis Albright of Cornell
University in New York has worked
out that lettuce grown outdoors in
California and taken by road, rail
or plane to New York has a carbon
footprint of 0.7 kilograms per
kilogram of lettuce on average.
For lettuce grown locally in heated
greenhouses with supplemental
lighting it is 2.4 kg. And for lettuce
grown entirely under artificial
light it is 8 kg.Clean limbs
There has been much speculation
on Twitter recently about whether
we should wash our legs when
in the shower. I think legs don’t
specifically need washing, and I
suspect we overwash generally.
How often should we wash, for
health benefits or other reasons?
(continued)Hillary Judd
Exeter, Devon, UK
The question implies that the
water running down the legs
from the rest of the body while
showering is sufficient to wash
them. But observation suggests
that water runs down in rivulets,
leaving areas of unremoved sweat,
skin cells and grime. Drying such
an area with a towel might not be
looked upon favourably by anyone
who has to do the laundry.
When preparing walls for
redecoration, the advice is to wash
from the bottom up as dirty water
from the higher portions will be
more easily removed from a clean
surface. Perhaps the same idea
should be applied in the shower.Lisa Prickett
Newick, East Sussex, UK
Previous respondents were
male and made good arguments
against leg washing in the shower
to use as little soap as possible,
unless you are a gardener.
To add a different perspective,
there are many women, and some
men (particularly keen cyclists),
who shave their legs daily in
the shower. Applying a foaming
agent or soap helps to reduce
irritation and avoid missed
strips. Although washing isn’t the
primary purpose, in this situation
they do get washed daily. ❚This week’s new questions
Fresh fruit Most fruit and vegetables sold in supermarkets
come with a label saying “wash before eating”. What are
the risks of eating unwashed produce and does a quick
sluice under the tap reduce them significantly? Ian Cairns,
Seaford, East Sussex, UKEnd of an era Dinosaurs went extinct 66 million years ago,
apparently as a result of an asteroid impact. How much time
elapsed between that event and the death of the very last
dinosaur? Sami Franssila, Helsinki, FinlandWant to send us a question or answer?
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HERO IMAGES/GETTYIs rinsing tomatoes under
the tap enough to wash
anything harmful off them?