14 | New Scientist | 22 February 2020
Analysis EnvironmentCONSUMERS around the world
could be wasting more than
twice as much food as thought,
according to an analysis that
says previous figures have
been gross underestimates.
The Food and Agriculture
Organization of the United Nations
(FAO) said in 2011 that around
a third of food is lost or wasted. Its
report is considered to have played
a key part in food waste reduction
becoming one of the UN’s
Sustainable Development Goals.
But the widely cited estimate
appears to be wrong when it
comes to the amount of food
people waste at home because it
was based on models that failed
to account for affluence – how
much more the rich waste than
less-affluent people.
“The problem is much worse
than we think. We have to wake
up. I hope it’s a wake-up call,”
says Monika van den Bos Verma
at Wageningen University &
Research in the Netherlands.
She and her team took an
unusual approach to calculate
global food waste. Due to a
scarcity of comparable national
data on such waste around theworld, they instead inferred it. First,
they compared how much food is
produced – based on UN data on
its availability – with how much is
eaten, as calculated by the energy
people need to consume and
World Health Organization data
on body mass from 63 countries.
Then they used World Bank data
to factor in affluence.
This suggests that an average
person wastes 527 kilocalories
(kcal) a day. That is about one-fifth
of the 2500 kcals the averageman needs to maintain a healthy
body weight, according to the
UK’s National Health Service, or a
quarter of the daily recommended
intake for a woman. The previous
FAO estimate came to only
214 kcals a day (PLoS One,
doi. org/ggktnh).
The new figures are for 2005,
due to a lag in data availability and
to allow a comparison with the
UN research. Van den Bos Verma
found that food waste starts tobecome a serious issue once
people reach a total spending
power of $6.70 a day.
She says the work shows the
importance of looking at different
consumer attributes. “Food waste
is a luxury when you’re poor, it’s
not when you’re richer. The value
of food, it goes down [as you get
richer]. It’s also availability: the
more you have, the more you’re
likely to waste.”
There are limitations to the
new analysis. It only covers 67 per
cent of the world population and
doesn’t draw on data from some
big food-wasting countries,
including the US.
The FAO says the research
provides new insights, but should
be viewed as part of a body of
literature. Andrea Cattaneo at
the FAO has some doubts about
the results, such as Japan coming
out as a country that wastes lots
of food, which he says is unlikely
to reflect the reality. “The study
is by no means the definitive word
on the levels of consumer waste,”
he says. “It is one more estimate.”
The UK’s waste agency, WRAP,
says it has used a similar modelling
approach to the Dutch team, but
found it tended to significantly
overestimate the amount of food
consumers waste when compared
with approaches that involve
painstakingly collecting real data
on household waste and getting
people to keep waste diaries.
Van den Bos Verma says the
biggest assumption the new
analysis makes is that poorer
countries will develop the same
way as richer ones have in the
past. That risks a “brewing
potential future problem” of
even more food waste, she
and her colleagues warn. ❚BIOSP
HOTO/ALAMY^ STO
CK
PHOTONews
Food waste reduction
is a UN Sustainable
Development Goal527
Average daily food waste per
person in kilocaloriesScale of food waste A widely cited statistic claims a third of
food is lost or wasted – but this doesn’t account for how much
more food richer nations squander, says Adam VaughanPollutionJames UrquhartA SEA of floating, shed tarantula
skins might be an arachnophobe’s
nightmare, but the moults of these
spiders could help mop up ocean
oil spills.
Spider skin is mainly made of
chitin, a biopolymer that is also
found in the tough exoskeletons
of crustaceans. Chitin from
crustaceans is widely used to
clean up oil spills, as its molecular
structure soaks up the oil.
Spider skins have very strong
water-repelling properties, says
Tomasz Machałowski at Poznan
University of Technology in Poland.
This means they could be handy
for cleaning up oil spills, as the
materials used need to not only
attract oil, but also repel water
to stop them from sinking.
Machałowski and his colleagues
wanted to find out if the skin shed
by Peru purple tarantulas of the
genus Avicularia, which moult
many times during their life cycle,
could be an efficient oil sponge.
The team put 100 milligrams of
shed tarantula skin in a dish with
60 millilitres of seawater that had
2 grams of crude oil on the surface,
then measured how much oil was
soaked up. After 2 minutes, the
tarantula skin had captured 63 per
cent of the oil – nearly 13 times
its own weight – while absorbing
very little water (Journal of
Environmental Management,
doi. org/dmnv).
Machałowski says the dense,
bristly hairs trap the oil, while
their irregular arrangement
helps them clump together to
lock the oil in. The oil is soaked
up through a similar mechanism
to capillary action.
“This is a very unusual concept,
but surprisingly effective,” says
Megan Murray at the University
of Technology Sydney. “I’m not
sure how this can scale up, but the
physical mechanism could inspire
new material designs.” ❚Hairy spider skins
could be used to
soak up oil spills