Climate change

August 10, 2010

Balancing carbon with smoke and mirrors

Filed under: Livestock's long shadow, nitrous oxide emissions — Barry Brook @ 2:17 pm


Guest Post by Geoff Russell. Geoff is a mathematician and computer programmer and is a member of Animal Liberation SA. His recently published book is CSIRO Perfidy.

Have I got a deal for you! I’ll be marketting my new patent-pending sandals in China and if just 1% of the population buy them, then I’ll sell 13 million pairs. To test my business plan, I gathered 100 Chinese into a room and sold 3 pairs of sandals. How can my plan fail?

The Wentworth Group of concerned scientists released a paper recently called “Optimising Carbon in the Australian Landscape”. It has a similar deal, but one for all Australians. It quotes a CSIRO estimate that there is a biophysical capacity to store 1,000 million tonnes of CO2eq in soils and vegetation every year for the next 40 years. The Wentworth group isn’t aiming to capture 1% of this “market”, but 15%. A mere 15% would offset 25% of estimated annual greenhouse emissions for the next 40 years. Who could resist a deal like that? How could it fail?

Leaving aside any problems with the methods behind the CSIRO estimate, it seems reasonable to ask just how hard this “market” is. Why pick 15%? Why not 20%? or 10%? But even more important than a justification of the number is the definition of the slippery little word offset. It needs examination. This isn’t semantics, but goes to the heart of the possibilities of climate change stabilisation.

Climate target constraints

First I’ll repeat the physical ground rules for new BNC readers. These basic limits come from James Hansen and coworkers recent paper Target atmospheric CO2: Where should humanity aim?. Hansen has simplified the presentation in his book Storms of My Grandchildren. He calculates what will happen to atmospheric CO2 levels over the next century if we can phase out unsequestered coal use entirely by 2030. This is unlikely considering the number of coal fired power stations still being built, but where would it put us in 2150? It would give us an atmospheric CO2 level of about 400 ppm and continued climate change with risks of crossing points of no-return to a climate of more and bigger storms and even more serious global food problems than presently. So, even the daunting challenge of phasing out coal by 2030 isn’t enough. Pulling the CO2 level down below 350 ppm will require further action. If we actually want to undo ongoing ocean acidity changes and arctic sea ice shrinkage, then Hansen suggests that a level of perhaps 300-350ppm is required. In addition, we must cut non-CO2 forcings … black carbon and methane being the biggest.

What is the most that a total roll back of 200 years of deforestation could yield? According to Hansen and the best available estimate of what those 200 years of deforestation have contributed to the atmosphere, the most is about 60 ppm … and we need it all.

This is the scenario within which the Wentworth Group of Concerned Scientists and others are discussing offsetting and carbon credits.

Offsetting within a constraint

If you accept Hansen’s target and understand that the long atmospheric lifetime of CO2 severely hampers your pathways toward that target, then this determines the kind of offsets that make sense.

Hansen understands this implicitly when he says that deep cuts in non-CO2 forcings can allow us to slow the rate at which we reduce CO2 emissions (the coal phase out). Similarly, cuts to cooling aerosols will need to be offset by even quicker cuts to CO2 emissions or non-CO2 forcings.

It clearly makes sense to use the term offsets when trading emission reduction methods. If you increase one, you must offset this with a decrease in the other. But can reforestation be regarded as an offset for some positive emission? No, because it is already being used for something … namely the restoration of 350 ppm. Likewise if you use the shutdown of a coal station as an offset for some other emission, then you have achieved nothing.

A numerical example will help. Suppose that, as part of our goal to get to 350 ppm by 2150, we plan to reforest N million hectares. Now lets say we propose some activity which leads to CO2 emissions … for example that we increase the national cattle herd by a million animals which turn carbon dioxide into methane … massively increasing its warming impact for the next decade or so. Whatever we do to offset these animals must be over and above the reforestation, because that reforestation already has a purpose. It is spoken for. To regard it as a cattle offset is double counting.

Grazing and balancing

Recently, Barry Brook had an email from Tony Lovell of Queensland Accountancy firm AllStatePartners who was interested in increasing soil oxidation to absorb methane from cattle.

In the previous section I outlined why any increase in cattle can’t be balanced by reforestation, unless it is by an increase in reforestation over and above the level required to get us back to 350 ppm by 2150. Can an increase in either soil carbon or soil’s ability to absorb methane be used to offset methane from current cattle populations?

In principle, yes. But we must avoid double counting. Here’s how to run the calculations. Let’s assume for now that we can just use increases in soil carbon to offset methane.

Consider a grazing area g with a particular herd you wish to offset.

  1. Calculate what the rolling back of deforestation and soil carbon losses on g would contribute (if anything) to the 60 ppm achievable from a global deforestation roll-back. Call this the sequestration potential S(g) of area g. Cleared rainforest in Queensland has a huge reforestation potential, cleared mallee rather less. Some areas of deforested land are simply unavailable for reforestation … we live on them. But, in Australia, this is only 2 million hectares out of the total of 100 million cleared since white arrival. The sequestration potential of any area we can’t reforest has be made up … somehow.
  2. Now calculate the carbon difference associated with keeping the land under grass for cattle with a normal management regime rather than reforesting it. Call this the foregone sequestration F(g) that results from running cattle.
  3. Lastly we add in the amount of carbon required to offset the various emissions (particularly methane and nitrous oxide) from the cattle. This is the production cost P(g).

The amount of soil carbon and/or reforestation you need to provide to offset the herd on g is thus F(g)+P(g). If you are finishing the cattle with feed or fodder grown elsewhere on land needs to be kept clear, rather than reforested, then you will need to add in a further foregone sequestration amount. If you are running the cattle on uncleared land, then F(g) may be quite small.

Here’s a simplified concrete example. Consider a grazing area near Daintree in Far North Queensland. Assume it was cleared and will support a rainforest with a carbon sequestration potential of around 500 tonnes per hectare when fully reforested. If we leave the cattle in place the pasture may have a soil carbon content of perhaps 100 tonnes per hectare. The NSW Department of Primary Industries is telling farmers they can add 0.3 to 1 tonne per hectare for perhaps 50 to 100 years using improved management practices. Being very generous, this amounts to 200 tonnes per hectare, giving us a 300 tonne per hectare shortfall over straight reforestation. F(g) per hectare over the area is 300. Add in a number for P(g) and this is what your improved management practices really need to be delivering to compensate for keeping the land under cattle rather than returning it to its previous state.

Balancing and capping and trading

The fundamental shortcoming of cap and trade and carbon taxes is the presumption is that if we just stopping emitting carbon, everything will be okay. This belief is intuitively plausible but not supported by the science. The carbon already in the atmosphere won’t decline quickly without our active efforts to sequester it. To do this we must stop global burning and other activities which prevent reforestation from drawing down carbon and oxidising other trace gases.

Under a cap and trade system foregone sequestration doesn’t appear. It is an off balance sheet item.

And then there’s triple counting

The third step in the grazing balance formulation above, the calculation of what you need to do to offset production emissions is quite complex and I’ve just glossed over it in my example … not that the first two steps are really simple either!

The methane and nitrous oxide from cattle can be dealt with in various ways. You can sequester some quantity of carbon to account for it, or you can arrange for the soil to oxidise an equivalent amount of both gases or some mixture of the two.

But it isn’t enough that the soil under the cattle oxidise an amount of methane equivalent to that produced by the cattle. Why not?

That soil was always oxidising methane, even back in preindustrial times when atmospheric methane was 0.7 ppm rather than the the 1.82 ppm that it is now. Ignoring other methane sinks in the upper atmosphere, the soil oxidised the methane produced in wetlands, bogs and the like. It’s like a see-saw with a block of natural methane emissions on one side and natural breakdown on the other. There was, at human time scales, a rough balance. It was 0.65 ppm in 1600 and just 0.7 ppm 200 years later. Now however, people are quantifying that natural methane breakdown block on one end of the see-saw and saying, ”Wow, we can put an equivalent block of cattle on the other end of the see saw and the emissions will be offset. Beef can be carbon neutral!” Of course, there is a way to make beef carbon neutral … remove an equivalent number of other natural emitters … drain some wetlands, for example. This is a popular method for making grazing country in the South East of South Australia. But just counting natural oxidation as offsetting additional cattle is double counting, plain and simple.

This kind of double counting of a natural sink is over and above the double counting we discussed previously, which is where we take increases in forest cover or soil carbon that are absolutely imperative to bring us to 350 ppm and think we can use them in offset calculations. Combine the two and we have the real possibility of triple counting.

It’s all in the numbers

Here’s a little quantitative background on soil oxidation of methane.

Back in January 2010 US Environment news source Grist ran a story about cattle in which all sorts of claims were made. Including the following:

In contrast, one cow’s worth of healthy land actually absorbs one hundred times the methane emitted by that cow in any given year.

The claim turned out to be based on an article in the Australian last year which mentioned high country in the Monaro region of New South Wales that could oxidise 8.7 tonnes of methane per annum per hectare.

How does that number look to you? Tonnes?

A paper published last year surveyed areas in temperate, Mediterranean and sub-tropical regions of Australia with sites in both forested and pastured land found a range of absorption per hectare of -0.8 to 2.6 kg of methane per annum in pasture and 0.08 to 4.3 kg per annum in forest. That’s right kilograms in the peer reviewed journal and tonnes in the Australian. I’d been meaning to chase that descrepancy for months and finally did it when I decided to write this piece.

It’s a mistake. A microgram figure got promoted to milligrams. Ouch. Off by a factor of a thousand. It happens. Everyone can be thankful it isn’t in an IPCC report or we’d have high-country-gate! Professor Mark Adams has kindly sent me a conference paper which gives correct figures and a correction has been printed (see previous link). Unfortunately, the myth will live on and be circulated far and wide by cattle friendly bloggers … not everybody sees corrections … and the correction doesn’t seem to have made it to the original newspaper!

The bottom line is that the high country can oxidise 2 or perhaps 3 times more methane than the other areas measured, but not a thousand times. Grass fed cattle might produce 83 kg of methane per annum so it may take 10 hectares of high country to deal with each cow, assuming it wasn’t already dealing with other emissions. Remember, even after the mistakes have been rectified, this is still just double counting.

Here’s a quote from the conference paper that Adams supplied:

Given the parameters of this [beef] production system that equates to 5.4 tonnes CH4 produced annually.

Given the average rate of CH4 oxidation … for each landscape element, multiplied by the area represented in this production system, total sequestration amounts to 7.6 tonnes, or a 2.2 tonnes offset to enterprise scale emissions of CH4

So the natural methane oxidation is being claimed, not just to offset the beef methane, but the excess (in this case) is considered a further offset asset.

Rewriting environmental history

Part of the reason people think they can get away with double counting is a warped view of the history of animal life on earth. Lovell in his email to Barry paints a depressingly common, but wrong, picture to support his scheme:

We have had billions of ruminant animals on the planet for millions of years, without any issues until human management and mismanagement got involved. Nature has a way of balancing things, and the simplest way to balance the bacteria in a rumen that produce methane is to have some other bacteria in the soil that oxidise methane.

Not true … in a number of ways.

Ruminants evolved about 50 millions years ago as small (less than 5 kg) forest dwelling omnivores. While animals we would easily recognise as cattle are perhaps 2-3 million years old, there weren’t very many of them until very recently.

Here’s a chart from a few posts ago showing some relevant animal populations in 1500 and now. There were a couple of hundred million largish ruminants in 1500 and a couple of billion now.

The current total population of wild ruminants is estimated at a mere 75 million and most of those are quite small animals. There are, all up, 46 times more domestic ruminants. That’s right 3.5 billion. And there are not just many more of them, but many have been artificially selected to be bigger. Our agricultural selection pressures have totally changed the metabolic processes in the animals. Dairy cattle, for example, aren’t just bigger, but they now produce about 2.5 times more milk than a wild variety of similar size would produce. N.B. If you understand allometric equations, then you will understand the full import of this sentence. More milk requires more feed and thus entails more methane. Second, many of the large grassland areas that have emerged during the past 8,000 years are anthropogenic. Following the last ice age, global forests expanded as the ice receded, a process which lasted 8,000 years or so.

The prairies of the US were far smaller 18,000 years ago than 8,000 years ago. The large bison herds at the time of European arrival in North America were a human creation, not some non-anthropogenic natural phenomena. People with fire can clear forest and have been doing it for thousands of years. But until recently there weren’t that many people. The current explosion of humans and ruminants, not to mention other domestic animals is unprecedented.

Another of Lovell’s misunderstandings is his apparent belief that nature made soils with the aim of balancing that ruminant methane. Nature doesn’t give a damn about balance and has no goals of any kind. This is demonstrated by the way that the planet has whip-sawed with speed and violence between ice ages and hot ages as recorded in ice core and other climate records. When things move slowly on human time scales, we infer balance, but on longer time scales it is quickly seen as an illusion.

Similarly, evolution doesn’t strive for balance or efficiency or perfect form and function. Many of its “inventions” are suboptimal kluges that would embarrass any engineer. Others are elegant or efficient or both. Evolution always has to build on what went before. Unlike an intelligent designer, it can’t start with a blank page. Sometimes we judge the result to be brilliant, sometimes not.

It is humans who seek balance and it is us, along with many other animals, who have goals and desires. We have thrived during the recent few thousand years of relatively stable climate and we desperately want it to continue … well some of us do.

Offsets, carbon trades and all the other financial paraphernalia have some lawyers and accountants salivating overtime with dreams of trotters in the trough. It may be inevitable that such mechanisms will be put in place, given the prevailing economic ideology. But they need to be solidly constructed so that they don’t undermine what we absolutely must do in the coming couple of decades.

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