Methane
– is it really 30 times worse than Carbon Dioxide?
Given
the amount of news coverage devoted to oceanic pollution, it is not
surprising that most Kiwis believe reducing waste is more important
than addressing climate change.
It
is also alarming, because it is wrong. Why is the message about
Climate Change not getting through? Possibly because it is
complicated.
Perhaps
this statement will help. If we continue emitting greenhouse gases
into the atmosphere, within a generation, we will have set the Planet
on a course to devastation that is irreversible.
The
two most important greenhouse gases are carbon dioxide (CO2) and
methane. Of the two, methane is more potent, more immediate and, in
the short term, more important.
It
is complicated to compare gases to each other because they are all
different. Different molecular weight, different half lives,
different heat holding capacities. Scientists try to make things
less complicated by reducing the variables. So they compare all
greenhouse gases to CO2, which is used as the standard.
So
a gas’s Global Warming Potential (GWP) is a comparison one ton of that gas to one ton
of CO2. However, since gases survive in the atmosphere for different
amounts of time, the comparison to CO2 is measured over an arbitrary
time period. The time period used is generally 100 years. This is
probably sensible when comparing CO2 to nitrous oxide (NO2), because
NO2 survives for around 114 years, and CO2 survives for more than 500
years.
The
problem is that some gases, like methane, survive for much shorter
periods of time. Most methane is broken down in the atmosphere
within 12 years (confusingly it mostly oxidizes to CO2, but that is
another story). So when you compare methane to CO2 over a 100 year
period, for the last 88 years of the comparison, there is very little
methane left. This means that the vast majority of the damage done
by methane happens in those first 12 years.
If
you compare methane to CO2 over the standard 100 year period, methane
traps 30 times more heat. But if you do a 20 year comparison,
methane comes out 85 times more potent than CO2. This means that if
you produce 1 ton of methane from biodegradable material by sending
it to landfill, that 1 ton produces the same warming as 85 tons of CO2.
Think
about that for a moment. The average household in New Zealand sends
to landfill around 1 ton of biodegradable material every year, mostly
food scraps, green waste and paper.
Reducing
waste is a significant part of what we need to do to help save the
Planet, but the most important part is understanding what types of
waste we need to reduce. Diverting household bio waste from landfill
is the simplest and most significant thing you can do to help.
The
good news is that within 12 years the actions you take today to
mitigate methane production will be felt by the Planet. That,
coincidentally, is the amount of time we have left to change the
course of history.
Additional Information