Global Warming, Flatulence and Archaea
Many years ago, we were in New Zealand in their springtime and
were enthralled with the huge number of sheep and newborn
lambs. Against the bright yellow and green hillsides, they made
a beautiful picture. It was disturbing to see an article about them
in the July 16 issue of the National Post, a Canadian paper. With
roughly 47 million sheep and 10 million dairy cows and beef
cattle, approximately half of New Zealand''s greenhouse gas
emissions come from these creatures'' belching and flatulence!
Actually, New Zealand''s percentage of the world''s greenhouse
gas emissions is pitifully small compared to emissions from the
rest of the world, much less than one percent of the total.
However, unlike the U.S., New Zealand wants to see the Kyoto
pact in force and it plans to try to curb these animals'' emissions.
A proposal suggested early on was to impose a "flatulence tax".
The negative reaction of the farmers to such a tax was virtually
unanimous. According to the Post article, New Zealand''s Energy
Minister Pete Hodgson has now ruled out this tax in favor of
more research. A major component of the belched and flatulated
emissions is methane gas. So far, progress has been made in two
areas. A microbiologist named Jenkins has come with a formula
of live microorganisms that improve digestion and also inhibit
the formation of bacteria that promote methane formation in the
digestive system of cows. There is also work in progress to
develop new kinds of grasses that will lower methane production
when these grasses are eaten by the sheep and cattle.
Perhaps some words about the greenhouse effect and global
warming are in order. Over the years, we''ve been fortunate to
have a modicum of greenhouse gases in the atmosphere.
Without them, our earth would be a very cold place indeed and
we would have probably frozen to death. What happens in a
greenhouse, and on earth, is that the light from the sun comes
streaming down at wavelengths that sail right through our
atmosphere. The light gets absorbed and then gets radiated back
into space. However, it gets radiated back at longer
wavelengths. The greenhouse gases don''t let all of this longer
wavelength light go through but absorb some of it and radiate it
back down to earth. This helps keep the earth at the comfortable
temperatures we enjoy.
The problem, of course, is that if we put too much of these
greenhouse gases into the atmosphere, more of this light is
reflected back and the earth heats up. The most talked about
greenhouse gas is the carbon dioxide formed when we exhale,
burn fossil fuels, etc. Another is the fluorocarbon gas that we are
phasing out of our air conditioners and spray cans. Methane is
the problem of concern here. It hangs around the atmosphere for
about ten years typically. However, methane is roughly 20-25
times more efficient at trapping heat than carbon dioxide on a
molecule by molecule basis. A cow burps about half a pound a
day of methane into the air. Multiply that by well over a billion
cows worldwide and you''ve got half a billion pounds of methane
a day from those critters. Sheep only produce a bit over a tenth
as much but there are more of them, at least in New Zealand.
How to solve the problem? We all could become vegetarians I
guess but it would still be good to have wool blankets and leather
baseball gloves and the like. We''d still have to raise some sheep
and cows. It''s such a huge problem that my mind is sore just
thinking about it. Why don''t we take a look at the methane that
is NOT emitted? Remember that we''ve talked in the past about
the methane that sits at the bottoms of our oceans and about (a)
its potential use as a fuel source or (b) the possible terrible
effects that might result if global warming should lead to much
of this methane coming to the surface? Even as we speak, there
are little microbes toiling away making more of the stuff deep
below the surface of the ocean floor.
We need something on our side to help us. It turns out that there
is just such a helper described in articles by Carl Zimmer and by
Victoria Orphan and her coworkers in the July 20 issue of
Science. According to Zimmer, there are over ten trillion tons
of methane buried in the depths of the ocean floor. This is
purported to be more than all the known fossil fuels such as coal
and oil. And these little microbes are down there making more!
You would think that, with all this manufacturing of methane
going on, gobs of methane would be feeding up through the
ocean to our atmosphere and we''d really be in trouble with global
warming, irregardless of our own activities.
About thirty years ago, this problem was recognized but
geochemists found that the methane was reduced to virtually
nothing when they looked at the mud near the surface of the
ocean floor. Somehow, on its way through the mud it was
gobbled up. Speculation was that methane-eating bacteria were
chewing up the methane. Such bacteria had indeed been found,
but not at the bottom of the oceans. The problem was that these
bacteria lived in fresh water and soil where there''s lots of
oxygen. But down in the depths of the ocean bottom, it''s
saltwater and there''s virtually no oxygen.
What geochemists found was that when they measured the
methane level it went to essentially zero at a certain depth below
the floor''s surface. They were surprised to find something else
when they measured sulfate levels. Sulfate is normally present in
seawater and, lo and behold, the sulfate concentration also went
to zero at the same depth. So what to conclude? Obviously, the
same organism that was eating the methane also had a taste for
sulfate. But that would be a really strange bug indeed. So much
so, that the title of Zimmer''s article is "''Inconceivable'' Bugs Eat
Methane on the Ocean Floor".
After a lot of good detective work, through DNA work and
fashioning probes that latch on to the specific kinds of DNA,
researchers managed to ''light up'' the methane-eaters by making
them fluoresce. Sure enough, these critters were not your
ordinary bugs, but clumps of archaea. Archaea are a class of
organisms all by themselves, not bacteria nor fungi but a true
separate form of life. The surprises weren''t over. It turns out that
the ''inconceivable'' bug was not one bug but two! A shell of
bacteria surrounds the clumps of archaea. And what do you
know - the bacteria turned out to belong to a class of bacteria
known to dine on sulfate. Speculation naturally ensued that there
was some kind of arrangement between the archaea and the
bacteria that allowed the archaea to eat methane while the
bacteria could use the waste products of the archaea to help them
digest the sulfate.
Enter the team of Orphan and her coworkers from institutions
ranging from California to Massachusetts. They took samples of
the mud from the Eel River Basin off the coast of California and
used a variety of sophisticated techniques to analyze it. One
technique is known as Secondary Ion Mass Spectrometry, SIMS
for short. I happen to have had some frustrating experiences
trying to use SIMS when at Bell Labs. You essentially shoot
some ions at a sample of your material and see what comes
flying off. It''s a bit more complicated but that''s the essence.
What our intrepid researchers did was measure the ratio of
different carbon isotopes. The reason is that in methane the ratio
of these carbon isotopes is different from the normal ratio. If
they found the carbon isotope ratio to be the same in the two
bugs, that would show that the bacteria do indeed use the carbon
products from the archaea.
As you might expect, they found exactly that, confirming that the
two species have this great living arrangement where both
benefit. The actual chemistry remains to be determined but at
least the nature of the beast is now known. What is interesting
when all is said and done is that this team of archaea and bacteria
are estimated to consume some 300 million tons of methane a
By now, you know I''m a sucker for finding out about my roots.
The article mentions speculation that at one time the methane
levels in the atmosphere were much higher than they are today.
The high methane levels would have helped to keep the earth
from freezing. However, with increasing amounts of other
greenhouse gases, things would have gotten out of hand and the
heat would have fried us. That is, if we were ever born in the
first place. Without the evolution of that archaea/bacteria team,
we might not be here today! So, in the last few weeks, we''ve
considered how the faster decay of antimatter allowed any
ordinary matter to exist at all and now, perhaps, a bug team that
permitted us to form and helps keep us here today.
Meanwhile, let''s hope those New Zealand sheep and cattle can be
prodded into being more circumspect in their digestive behavior.
But let''s not be so smug. When it comes to greenhouse gases, we
in the U.S. are responsible for over one quarter of the earth''s
greenhouse gas emissions! And those blasted SUVs don''t help!
Allen F. Bortrum