It's always confusing when people use different names for the same thing. Natural gas is burned for warmth and to generate electricity after being pumped from underground where it is generated by various processes. It is almost entirely methane ... but it typically contains traces of other gases. Methane is CH4 ... a carbon hooked up to four hydrogens. So when people talk about the hydrogen economy they are talking about a gas that is almost always generated by busting up natural gas. Hydrogen is also famously part of H2O ... water. But splitting water happens to be more expensive than splitting methane.
The quadruple stomachs of a cow or goat are also fine places to generate natural gas. Rotting vegetation generates it in considerable quantities under certain conditions. A compost heap can generate methane if you aren't careful to keep it aerated.
For many decades cattle producers have been interested in reducing the methane from their cattle. Here's a research paper from 1982. The paper claimed to be able to reduce methane by 70 percent ... while citing ever earlier papers. Rarely has a year gone by without one or more news reports from a fresh faced journalist discussing the latest breakthrough with an excited researcher.
It doesn't seem to matter which end of a cow it comes from, or whether it comes from underground, methane invariably generates hyperbole and bullshit. Because it produces less carbon dioxide when burned, people called (and still call) it a transition fuel. Australians, who used to have excellent bullshit detectors, have become extraordinarily gullible over the past 20+ years and have bought that claim ... without question. All sides of politics have been backing what is an extraordinarily potent greenhouse gas. All sides of mainstream politics have backed the cattle industry. The Greens have backed the most environmentally destructive form of the industry (grass fed cattle) while opposing the least environmentally destructive (feedlots). George Monbiot is one of the best environmental thinkers on the planet but it took him quite a while to understand this. Feedlots are an animal welfare
disaster, but that's a different issue.
The trouble with methane, new carbon or old carbon
When you burn natural gas, you end up with carbon dioxide. If you pull natural gas from underground, then the carbon dioxide that results from burning it, is additional to the carbon dioxide that is already in the atmosphere. When cattle produce methane the methane will eventually break down into carbon dioxide and that CO2 is not additional. This has confused all kinds of people who argue therefor that cattle methane is not a problem because it isn't new carbon.
Wrong.
Diving into the ocean is a wonderful feeling. Diving head first into a block of ice is very different. The change of state of the water is critical. So it is with CO2 compared to CH4. Whether the carbon (the C) is now or old doesn't matter (much), what matters is that the heat trapping properties of a tonne of methane are 105 times greater than those of a tonne of CO2 ... and stay that way until it breaks down.
At this point, many readers will be thinking ... "105? no ... that's wrong ... I remember 25"
Greenhouse gases are measured in tonnes or millions of tonnes. The 25 factor is approximate for a molecule. A molecule of CH4 traps 25 more heat than a molecule of CO2. But its very much lighter, so a tonne of CO2 has far fewer molecules in it. Add in a few complex complications and the full impact emerges.
Carbon dioxide equivalence factor? There is no such thing
The whole idea that you can multiply a tonnage of methane by some single number to find the equivalent tonnage of carbon dioxide is dangerously false. As a rough guide to people who understand that this is all it is, it's fine. But it isn't physically true. Think of it this way. Take 100 grams of chick peas. This contains an energy value, typically measured in kilojoules or calories. Is there an chickpea-equivalent weight of apples? There is a quantity of apples with the same calories, but chickpeas have qualities which can't be replicated with apples. So it is with methane and carbon dioxide. Reductions in one change the shape of the temperature trajectory in a way that can't be replicated by changes in the other. I'll show this in a graph at the end of the article; keep reading!
In summary ... a tonne of methane released today will have 105 times the impact of a tonne of carbon dioxide, but that's only a rough guide. There are qualities in the two that this "equivalence" can't capture.
Fugitive Emissions
The powerful impact of methane on the climate has huge implications for Australia's LNG industry.
You can't produce natural gas without gas leaks. And it doesn't take a very big leak to undermine the so-called savings in carbon dioxide you make by burning gas instead of coal. But how do you accurately measure gas leaks? Governments around the world submit greenhouse gas inventories to the UNFCCC each year. They all contain data on leaks ... called fugitive emissions; a wonderful word for a leak. The leaks may not just be at the well head, but over a much wider area.
But recent paper in Nature used ice cores to more accurately quantify the source of the methane in the atmosphere. They estimate that current estimates of fugitive emissions are about 25 to 40 percent too low ... meaning everybody has been underestimating the amount of gas that's been leaking. This is consistent with a 2018 study showing leaks in the US were 60 percent higher than inventories recorded.
If that paper withstands the usual scrutiny, and I'm expecting it will, then all National Inventories around the world will then be misleading in two ways instead of one. They are all misleading in not representing the full impact of methane over the next 20 years ... a rather critical time scale. But they'll also continue to understate the amount of fugitive emissions because you can't bet that the gas industry will fight tooth and nail to keep the current methodology of measuring leaks.
Nevertheless, here are the current inventories of a selection of countries. It shows methane's full impact over the next 20 years relative to CO2.
As you can see ... per person ... methane from our sheep and cattle are our main source of warming. There are a number of features worth noting.
The relatively steep decline in our emissions is mostly due to rising population. The cattle population has been stuck around 28 to 29 million while the human population has increased.
Note the blue area LULUCF ... "land use, land use change and forestry" is negative for Sweden and Canada ... their forests are undergoing a net expansion. Canada's expansion looks to be stopping, but Sweden's is stable. Australia is generally in debit, because we are clearing more land that we reforest. This category of emissions is extremely complex and the conventional no-physical-basis accounting of methane gives Australia a slight LULUCF credit on the official data.
Not France and Sweden have very low electricity emissions ... in France this is because of nuclear power and in Sweden because of a mix of hydro and nuclear. And in Japan you can see the bump as her emissions rose following the Fukushima meltdowns.
Transport? Nothing much is changing. The transport strip looks a little thinner at the end of the graph in Sweden; but that's about all.
Not one, but both
So I may have convinced you that methane is a big deal, but how much of a big deal?
Does it mean methane reductions will have an immediate cooling impact on the climate? Not quite, but it means that they will flatten the curve ... reduce the rate of increase.
Does that mean we should prioritise methane reductions? No.
If we focus on reducing methane and leave carbon dioxide untouched, then we will pay by higher temperatures in the far future.
If we focus on reducing carbon dioxide and leave methane untouched then we will pay by higher temperatures in the near future.
The above graph makes it clear what is going on. It is simplified for clarity from a paper by NASA climate scientist Drew Shindell. It shows what I said. Looked at from an optimisation viewpoint ... if we want to minimise the maximum temperature we hit, then we need to simultaneously hit both carbon dioxide and methane.
The graph also shows something I referred to earlier. Reductions in methane and carbon dioxide have different impacts on the shape of the temperature response. The best response comes with simultaneous reductions in both.
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