Gary,

Some incredibly obvious points:

1) The same amount of grass eaten by different animals does not produce the same amount of methane in their digestive tracts.

2) Decomposition is not done only by anaerobic bacteria. Depending on where it happens (e.g. in the air where oxygen is available or in a digestive tract where far less oxygen is available) the amount of energy in sugars that'll get turned in to methane will vary greatly.

4) As I mentioned in my post, the type of grass eaten has a huge impact on the amount of methane produced. Do some web searches on this and you'll find experiments in Australia, New Zealand, the United States and Italy (and probably more) comparing the amount of methane produced from cattle and sheep fed different grasses. This research is aimed at coming up with grass combinations that'll reduce methane emissions from livestock.

5) Cattle do compete with wolves, foxes, buffalo, and other critters. In some cases (e.g. against buffalo) cattle compete by eating the same food. In other cases (e.g. wolves) cattle compete because ranchers do not allow the wolves. Absent the cattle the wolves would have more other animals to eat.

5) Land returns from farming to forests if abandoned for crop farming and not taken up for grazing. Take away the grazing demand and there'll be more forests.

6) Much of the land converted to grain crop growing is done so to produce grain to feed to cows and other livestock. So there'd be more rain forest in Brazil if we were all vegetarians.

Hi Randall,

"The same amount of grass eaten by different animals does not produce the same amount of methane in their digestive tracts."

True. Only ruminants can digest it. It passes right through horses, people, pigs, birds and such. The same methane is produced in the end though, since a steaming pile of dung is good habitat for methane producing bacteria.

"Decomposition is not done only by anaerobic bacteria. Depending on where it happens (e.g. in the air where oxygen is available or in a digestive tract where far less oxygen is available) the amount of energy in sugars that'll get turned in to methane will vary greatly."

Unless a pile is aerated the oxygen is exhausted quickly, and so most of the work is done by anaerobic bacteria. That's why composters go to such pains to aerate their piles by turning them, or do clever hacks with pipes and such.

"the type of grass eaten has a huge impact on the amount of methane produced."

It's the cellulose component that matters. Efforts to reduce methane emitted by ruminants try to feed more sugary forages (including grains) since they bypass the rumen. Increased soil fertility helps. It's the cations such as calcium that increase sugars (brix).

"Cattle do compete with wolves, foxes, buffalo, and other critters. . . "

At that level of abstraction every animal competes with every other. But a careful analysis shows that polycultures aren't only more productive for swards. Multispecies grazing is more productive too. Coupled with a diverse sward total productivity is increased greatly. The trouble is that the market for wolves and foxes is immature. That may change. A number of policies ranging from agro-tourism to direct subsidies (a sort of reverse ESA) have been discussed as ways to reward range managers for diversity the market ignores. Premium prices for their products paid by caring yet price-insensitive consumers can help a bit.

"Land returns from farming to forests if abandoned for crop farming and not taken up for grazing. Take away the grazing demand and there'll be more forests."

That depends on the place and other management behaviors. Fire and grazing are natural controls for forests. Grasslands are not something we created. The American Great Plains, for example, were never forested, at least not since the ice retreated. There may have been a time in deep history when there were forests there. All the staple foods of humans are annual grasses, it's just that we can only digest the seeds. The perennial grasses that dominate grasslands don't make as many seeds. If they did cropping would be very different and far less destructive.

"Much of the land converted to grain crop growing is done so to produce grain to feed to cows and other livestock. So there'd be more rain forest in Brazil if we were all vegetarians."

It's mostly to feed European and Chinese chickens and pigs, which do not thrive on grasses. Some is also fed to fatten cattle for market, but this is alien to the grass based culture of Brazil. Their national cuisine requires grass finished meats. There would not be more rain forests if we were all vegetarians, they'd just grow soya to fatten people or cane and corn for fuel. One way or another the forests will go unless they have greater value intact. It's just silly to blame cattle. Of all the principals in this drama they are the most innocent.

Still, if you wish to be rational there are improvements that can be made. Graze ruminants on grasslands, which are as valuable ecologically as forests, but skip the livestock that have less robust digestive systems and need richer foods than grass. Cut down on hogs, fowl and farmed fish, for example, since they have poor digestive systems like humans and so compete directly with people for food. Also stop feeding people food to ruminants. They don't need it to thrive. It makes them sick - fat and sick.

To have healthy ecologies you must have grazers. Many species of plants, animals and insects depend on them. Grazers need predators too. Wolves and big cats once did this job, but they have a taste for people and their pets too so it's not possible to rely on them alone. People have to do part of the job.

A day may come when we stop cropping and also stop raising food animals, but not soon. In the meantime it would be wise to try to do a good job with general farms that raise all sorts of foods, or have independent specialists in a region that together can function as an integrated general farm on a large scale.

Gary,

Cellulose is not the only thing in grasses that affects how much of the grasses get converted to methane. Other compounds in grasses either suppress anaerobic bacteria or do something else that affects methane production. Again, scientists are feeding grasses to ruminants and comparing amounts of methane production.

How do you know the same amount of methane gets produced by grasses broken down out in the open versus in digestive tracts of cows? Sounds like you are guessing.

People feed to ruminants: But if the people food has less celluose in it doesn't it cause the ruminants to create less methane?

Maybe human growth of human foods has led to a decrease in bacterial methane production. On the one hand, more of what comes out of fields is human digestible. On the other hand, the fertilizer and pesticides and irrigation cause more total plant growth.

Another factor: higher atmospheric CO2. That'll cause more plant growth. So will it too cause more methane production?

Brazilian rain forests: Yet the demand for meat is causing the destruction of rain forests.

It's the same bacteria doing the decomposition in the rumen as in the wild. The amount of methane produced by a given amount of forage on a dry matter basis depends on the composition of the forage. If it is higher in simple carbohydrates and protein then there is less complex carbohydrates like cellulose.

The most promising work to reduce methane, and increase CO2, is to engineer bacteria that live in anoxic environments but don't produce methane.

The reason this is promising isn't that cattle (and goats, sheep etc.) would produce less if inoculated so much as that landfills, swamps and rice paddies could be inoculated too. Maybe. Aerobic bacteria are oxidizing cellulose, which makes heat, enough to start fires under some conditions. This must be avoided.

There are risks in doing this since we don't fully understand how tinkering up bacteria for release into the wild will turn out in the long term. They will evolve, and will also swap genetic material horizontally with other organisms. This is much more risky than GE maize for example. Perhaps they can be bred rather than engineered, though it's not clear that this does in fact reduce risk. It will be more politically palatable at least.

"if the people food has less celluose in it doesn't it cause the ruminants to create less methane?"

Yes, and no. There is less produced in the gut of ruminants but the cellulose not fed to them still needs to be decomposed. Picking out the grain and leaving the leaves and stalks, for example, can give the illusion of reduced methane, but it's just a hide-the-pea game for the most part. However, if that material is burned or otherwise prevented from decomposing naturally then it's CO2 rather than methane that is produced. Besides, it's bad for their health and degrades their meat and milk, and so is bad for us too. Not a good solution.

One way or another the carbon cycle happens unless the carbon is sequestered. For example, bio-char (charcoal of a sort) can apparently remain in soil for eons. This is produced by low temperature pyrolosis, and if not subsequently burned as a fuel is quite stable.

But think. Ruminants are the only animals that can digest cellulose. This allows them to thrive on foods that no other animal can use. History is filled with examples of the advantages of ruminant based herding civilizations thriving when others have failed. They are symbiotic with humans in a sense. When insightfully managed they overcome all kinds of apparent obstacles since they are happy to fetch their own foods as well as spread their own wastes. The cellulosic wastes humans can't consume can be left in the fields and grazed, and so turn field trash into fertility for another crop.

Ruminants aren't a problem, they're a solution, a boon for a world that can't feed its growing population. But they can be improved. For example, the current popular breeds weren't always as they are now. They are bred larger or smaller depending on markets and methods. In a world where grain is dear and conversion efficiency is needed then smaller animals are better. There are miniature versions of every breed now. They are curiosities in most places, but in developing countries they are often prized for their efficiency, needing less forage to produce meat and milk since less in needed for body maintenance. Selecting for qualities in breeding programs pays off. In regions that do not feed grains, such as New Zealand, the same breeds have been selected for grazing efficiency rather than grain efficiency. Those genetics are now exported around the world as semen for AI.

Millions and millions of ruminants on almost all continents have existed for millenia. That certain breeds have been domesticated and are now managed by humans doesn't change this. Bison, for example, a breed you want to say is a competitor with cattle, can interbreed with them. It sometimes fails, producing a sterile male or being rejected from the womb, but we've been raising them for almost 50 years now, and was done in eastern Europe in the 19th century though that line has since been abandoned.

It seems confused to focus on ruminants as methane sources. It's like focusing on swamps. Clearly ruminants and swamps aren't the problem, it's something to do with people. That's why methane concentrations have gone flat. Clean-up of leaks in fossil fuel production has had an effect. But there is still a lot leaking out of coal mines and farm fields. Millions of tons are released from plowed soil every year. No-till farming would be a much more effective way to reduce methane emissions than worrying about cow belches (and calling them farts). Coal mining is more problematical. Since between 80% and 90% of the world's energy comes from fossil fuels it will be a long time before that problem goes away. Still, seeing that this is the problem is a necessary first step, and methods to capture the methane may be developed. Coal bed methane production is a growing business (with problems, mostly about water).

"Brazilian rain forests: Yet the demand for meat is causing the destruction of rain forests."

This is false. The demand for agricultural products is causing more land to go into production. This is happening and will continue, meat production or not. To prevent forest lands from being used the forests themselves must have a greater value than alternative uses. We can stamp our feet and hold out breath but unless they have value the forests will go. Indonesian forests are being repurposed for palm oil production and such. Brazilian forests will continue to be cropped. Sometimes they are grazed for a short while to prepare them better for cropping (rain forest soils have very low fertility), but recent data shows that within a year of clearing they are cropped.

Laws can be passed to artificially protect forests, but laws can change again and will do so in the end as demand for food and fiber rises. Permanent protection requires more than laws. Current efforts to devlop such protections include things like sustainable forestry, tourism and attempts to value ecosystem services. It's all pretty weak at this point and prospects don't look good for the forests.