| How much CO2 does a cow emit in its
there significant contribution through its waste?
|Question Date: 2017-03-09|
Animals, plants, fungi, algae, even many bacteria
produce CO2 . Every time an animal
breathes out, there goes CO2 that we
make when we break down food to release energy.
Fungi do the same thing, even they don’t quite
breathe. When they have light, plants and algae do
photosynthesis to make sugar, but they also break
down sugar when they don’t have light, just like
us, making CO2. Think about it, a tree
is made of cells, but only the cells in the leaves
are doing photosynthesis, the rest live off the
sugar the leaves make. When plants lose their
leaves, they survive on sugar or starch (long
chains of sugars) until they get leaves again.
So why do people blame cows for global
warming? That’s more about what comes out the
other end. Cows produce a lot of methane
gas as the bacteria in their stomachs break
down food. Methane is a powerful greenhouse gas.
Pound for pound it causes over 20 times more
warming than carbon dioxide. I found a source
that said, “average cow produces enough methane
per year to do the same greenhouse damage as four
tons of carbon dioxide.” That’s a lot of gas.
Their manure is also a source of methane as
bacteria break it down. One source said that a cow
produces about 100 kg of methane a year. This has
about the same impact as driving a car about 8,000
miles. As you can see, these estimates are very
different, but the idea is the same: cows
produce a lot of methane.
Global warming is not all due to cows. Any
time we burn gas, oil, coal, wood, or similar
things, more carbon dioxide is released. You might
think that you don’t burn any of those things, but
most of our electricity in the US comes from
burning fuels. When we cut down trees and other
plants, we get rid of things that remove carbon
dioxide from the environment.
What are some things that people could do to
produce less carbon dioxide (“reduce their carbon
Thanks for asking
Calculate the number of calories that a cow
intakes in a day, multiply that by the number of
days in a cow's life, and you get your answer. I
don't know what either of those numbers are, but
CO2 output is just the chemical
byproduct of burning sugars, which is used to
burn energy, so if you know the energy requirement
of an animal, you can calculate its CO2
output. It isn't related to waste.
You may be thinking of methane, i.e.
CH4, not CO2, which I know
cow stomachs also produce but I know less about
the mechanism (I know that the methane actually
comes from archaea and that the chemical reaction
is the oxygen-less fermentation of the sugars in
the grasses, but not the amount of methane
produced per kilogram of grass).
A cow can produce anywhere from 70-120kg of
methane in it’s lifetime. Methane is a
greenhouse gas, like CO2, but it’s much
worse for our climate. To compare, a cow that
releases 100kg of methane per year is the
equivalent of it producing 2,300kg of
CO2 that year. That’s the same amount
of carbon dioxide generated by a car after 7,800
miles of driving! So yes, cow waste, whether it be
burping, farting, or manure, significant
contributes to our world’s greenhouse gas
emissions. The good news, though, is there’s a lot
of research and experimentation going on to try
and turn cow manure into a renewable energy
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