Addition to original question on methane from cows causing global warming

[Rich0292]

It was answered that methane (gut bacteria working on cellulose) from cows does add towards greenhouse gases. However I want to know if it causes a net increase to the greenhouse effect or not.

Grass must balence it's root mass with that of it's leaf mass, when a cow bites off the leaf mass the grass lets a proportion of it's root mass die which is brocken down by soil bacteria to build humus. Obviously the root mass is a product of carbon the grass has taken from the air.

So in the same way a tree can lock in carbon by taking it from the atmosphere, soil can do the same thing despite the fact most people are unaware of this.

Since grazing takes carbon out of the atmosphere does this negate the addition of methane? (considering the different propensities for heat insulation in both gases).

I'd settle with more people being aware of this factor and cows are not evil (if grazed expertly) even if the question is unanswerable

[johnpost]

fart reference

http://www.straightdope.com/columns/...ths-atmosphere

[Michael63129]

A much bigger concern is methane from melting permafrost and methane hydrates, since, like fossil fuels, this represents a more or less permanent addition of methane and CO2 to the atmosphere; by contrast, living things more or less recycle all of their carbon, you also see this when people claim that breathing adds CO2 to the atmosphere. It is also true that atmospheric methane concentrations rose over the past century or two, although concentrations had reached a plateau until recent years (likely related to permafrost and hydrate melt). Also of note, the cattle population, at least in the U.S., is near historic lows, and that before this year's drought, so I wouldn't worry about cattle methane at all.

Incidentally, it isn't just cattle:

If the high bison population estimate is taken for this comparison, wild ruminants in the pre-settlement period emitted as much methane as the current domestic ruminants in the United States.

Of course, most of those bison (and other animals) are now gone, with current emissions, mainly from deer, at only 3.6% of domestic animals, so overall emissions haven't increased that much. Of course, it is better to have all of those wild animals than a vast monoculture of cows, but such is the human way.

Also, forgot to add, to put things into perspective:

Emissions of methane and nitrous oxide from enteric fermentation and manure management (i.e., the total livestock contribution to GHG emissions) was 202.9 Tg CO2 Eq./yr, or 47% of the agricultural emission, but only 2.9% of all GHG emissions in the U.S.

47% sounds pretty bad, but agriculture is only a small source of greenhouse gas emissions (of course, you might say I am biased by the notion that I might be doing great harm by enjoying beef, which is the most common meat I eat, but this data doesn't suggest that it is that bad).

[jmrcm]

If the cows didn't eat the grass, wouldn't it just reach the end of its' life cycle and then be digested by methane producing microbes?

The whole cow methane thing. A lot of the answers seem to be just of the top of peoples heads. If you feed cattle antibiotics to kill methane producing microbes, won't methane producing microbes eventually eat the cows' manure.

[Blake]

Originally Posted by Rich0292

Grass must balence it's root mass with that of it's leaf mass, when a cow bites off the leaf mass the grass lets a proportion of it's root mass die...

Do you have any evidence for this claim? While there is of course a long-term relationship between above ground and below ground biomass,there's no particular reason to assume that something as ephemeral as the removal of leaves will lead a plant to shed root mass.

What you say isn't implausible, but at the moment it lacks evidence.

... which is brocken down by soil bacteria to build humus. Obviously the root mass is a product of carbon the grass has taken from the air.

I'm not sure what your point is here.

The amount of root material that is converted to resistant humus is only a tiny fraction of the total root mass and the amount of root mass that would be lost due to defoliation would be only a tiny fraction of the leaf mass. IOW the amount of carbon converted to humus would be at least an order of magnitude less than the amount of leaf removed. Since leaves also decay to produce humus, there's at least an equal chance that cattle reduce the amount of carbon stored in soil.

The reality is that soil carbon sequestration under grazing is an incredibly complex and poorly understood process that depends on a great many factors such as grazing pressure, use of fire, pasture composition and climate amongst many, many others. Declaring that grazing by cattle increases soil carbon content without rigorous scientific studies can't possibly be justified.

Originally Posted by jmrcm

If the cows didn't eat the grass, wouldn't it just reach the end of its' life cycle and then be digested by methane producing microbes?

Probably not. Methanogens are fairly rare and only live in regions where there is no oxygen. Cows guts are good, dry soil not so good. You normally only get substantial methane production from leaf material in waterlogged soils. So if you are grazing water buffalo what you say is probably true. If you are grazing cattle it's probably not.

In tropical regions the picture is complicated by termites. Termites are also notorious methanogens, and grass not eaten by cattle tends to be eaten by termites. So the effects of cattle in tropical regions is usually less than in temperate.

The whole cow methane thing. A lot of the answers seem to be just of the top of peoples heads. If you feed cattle antibiotics to kill methane producing microbes, won't methane producing microbes eventually eat the cows' manure.

To some degree, but the important point is that by that stage most of the nutrition has been extracted bu the cow itself. So whatever methane is produced in the manure, it can only ever be a tiny fraction of what is produced int he rumen.

In simple terms, you can produce a lot more smoke burning grass than you can by burning the shit of cows that have eaten the grass.

[jmrcm]

Originally Posted by Blake

Probably not. Methanogens are fairly rare and only live in regions where there is no oxygen. Cows guts are good, dry soil not so good. You normally only get substantial methane production from leaf material in waterlogged soils. So if you are grazing water buffalo what you say is probably true. If you are grazing cattle it's probably not.

I went to see if I could find a paper on it, and found this. Methane production by ruminants: its contribution to global warming
http://www.bashaar.org.il/files/125122005103109.pdf

I think they tagged the 'its contribution to global warming' on to sex it up. It's mostly about methanongens and ruminants diet. It's interesting. Cattle have an abnormally high methanogenesis in their gut (or guts). If the methanongens can be reduced or wiped out, then their milk and meat yields would significantly increase - because the methane is useless to their diet and they just fart it.

So, either by breeding or adding things to their diets, the cattle methane problem could be taken care of, and product yields would increase.

The paper should have been titled

Methane production by ruminants: How your cattle are farting the money you're spending on feed into the sky, instead of into milk and beef.

[Blake]

Farting has nothing to do with it. Read Cecil's column.

[jmrcm]

Originally Posted by Rich0292

Since grazing takes carbon out of the atmosphere does this negate the addition of methane? (considering the different propensities for heat insulation in both gases).

I'd settle with more people being aware of this factor and cows are not evil (if grazed expertly) even if the question is unanswerable

The question is unanswerable in the sense that any answer would be an approximation.

The amount of methane produced by domesticated ruminants, is probably a quirk due to their breeding. Solve that problem and their contribution to atmospheric methane could be significantly reduced. It would increase agricultural yields - and would be worthwhile for that alone.

As for the global warming thing. Over the years people have muddied the waters - especially people with no science background or training, taking to the internet and half baking a lot of cakes.

The issue has nothing to do with the propensity of either CO2, or methane for heat insulation. It's to do with a specific aspect of the characteristics of their absorption of radiation(sun light).

People make statements like Methane is 21 times more powerful a greenhouse gas than CO2. Then they do back of the beer mat calculations, and make predictions that if we keep producing methane as we are, within a relatively short period of time, the earth's atmosphere will be hot enough to melt lead. ...."Not even wrong", doesn't begin to describe it.

The methane to CO2 argument. Maybe it's a marginal difference, maybe it's significant. It's not something you do calculate on the back of a beer mat - and the seas are not about to start boiling.

[Irishman]

Originally Posted by jmrcm

Methane production by ruminants: How your cattle are farting the money you're spending on feed into the sky, instead of into milk and beef.

Well, I'm not sure I'd want them farting into the milk and beef. YMMV.

[jmrcm]

Originally Posted by Irishman

Well, I'm not sure I'd want them farting into the milk and beef. YMMV.

Irishman, I'm Irish.....I've worked on Irish dairy farms....if you've ever drank Irish milk..there's been a little shit in it. Sorry, it was unavoidable. Very busy, and lots of ladies to attend to.

[Michael63129]

Originally Posted by jmrcm

The amount of methane produced by domesticated ruminants, is probably a quirk due to their breeding. Solve that problem and their contribution to atmospheric methane could be significantly reduced. It would increase agricultural yields - and would be worthwhile for that alone.

Not a quirk; if you look at my previous post, you'll see that wild ruminants contributed just as much methane before they were mostly wiped out; this is a characteristic of all ruminants, not just cows. Of course, feeding cows corn doesn't agree well with their gut, another reason to (if you can) get grass-fed beef and milk (this also applies to other animals, feeding animals food crops is also an inefficient use of food; then again, using food to fuel cars (40% of corn now goes to ethanol) is much worse).

[jmrcm]

Originally Posted by Michael63129

then again, using food to fuel cars (40% of corn now goes to ethanol) is much worse).

Yes, well now smug, misanthropic, upper middle-class Americans, have organic fuel to go along with their organic lettuce, and organic bread.

[gamerunknown]

Originally Posted by jmrcm

It's not something you do calculate on the back of a beer mat

Is that how you'd characterise these calculations?

[jmrcm]

Originally Posted by gamerunknown

Is that how you'd characterise these calculations?

A few fractions of a Watt per square metre of the troposphere. I would characterise them as hardly apocalyptic.

And arm waving is arm waving, even if it's peer reviewed and emanates from the Goddard space institute.