Dyson’s carbon eating trees

2008-06-05

in Science, The environment

White bridges near 111 Sussex

The New York Review of Books recently featured a couple of book reviews by Freeman Dyson. In them, he shares some interesting ideas:

  • There is a famous graph showing the fraction of carbon dioxide in the atmosphere as it varies month by month and year by year
  • [The graph features] a regular wiggle showing a yearly cycle of growth and decline of carbon dioxide levels. The maximum happens each year in the Northern Hemisphere spring, the minimum in the Northern Hemisphere fall. The difference between maximum and minimum each year is about six parts per million.
  • The only plausible explanation of the annual wiggle and its variation with latitude is that it is due to the seasonal growth and decay of annual vegetation, especially deciduous forests, in temperate latitudes north and south.
  • When we put together the evidence from the wiggles and the distribution of vegetation over the earth, it turns out that about 8 percent of the carbon dioxide in the atmosphere is absorbed by vegetation and returned to the atmosphere every year. This means that the average lifetime of a molecule of carbon dioxide in the atmosphere, before it is captured by vegetation and afterward released, is about twelve years.
  • [I]f we can control what the plants do with the carbon, the fate of the carbon in the atmosphere is in our hands.
  • Carbon-eating trees could convert most of the carbon that they absorb from the atmosphere into some chemically stable form and bury it underground. Or they could convert the carbon into liquid fuels and other useful chemicals.

This is, of course, a geoengineering scheme. As such, it is subject to the two major points of opposition: that we don’t know whether it would work, and that it would probably produce unwanted and unpredictable consequences. That being said, it seems less dangerous in the latter regard than schemes to fertilize oceans or fill the air with aerosols. Ideally, these enhanced trees would just behave like a larger number of normal trees.

Genetic modification of plants is likely to play a role in addressing climate change. Food crops are an obvious area where that is true. They may need to be made more resistant to heat, extreme weather, drought, and floods. They may even need to have their photosynthetic pathways altered. If, along the way, we come up with a mechanism for producing trees that eat more carbon, it could make a useful contribution to the overall effort.

We should not, however, forget the third big danger connected to geoengineering: the risk of falling into the complacent belief that technology will bring an answer. Super carbon eating trees are a long-shot – one worth considering, perhaps, but no excuse to keep on burning forests and coal.

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{ 12 comments… read them below or add one }

Dave June 5, 2008 at 2:30 pm

Interesting post!

Vegetation plays a very important role in the global carbon cycle. However the likelihood of whole scale genetic engineering is small. This is because of a fundamental trade off between the affinity of the key photosynthetic enzyme for CO2 and it’s rate of action. Although this sort of genetic engineering is commonplace in crop systems it’s unlikely to get us anywhere in a hurry. You gain a couple of % effeciency by modifying photosynthetic pathways – enough to increase profits but small in terms of carbon sequestration.

Switching from C3 plants to C4 would be more cost effective than engineering C3 plants to carry out C4 photosynthesis. We could spend millions on researching this topic in the hope that we can pull it off. By all means if you have the cash, spend it.

However, by far the simplest and cost effective method to increase the amount of CO2 stored by vegetation is to increase the land area covered by vegetation.
1. Stop cutting down forests
2. Plant new forests

David June 5, 2008 at 3:23 pm

Carbon-eating trees could convert most of the carbon that they absorb from the atmosphere into some chemically stable form and bury it underground. Or they could convert the carbon into liquid fuels and other useful chemicals.

1. If we are ever going to be able to do something like this, it will take many decades of additional research into genetics and biotechnology.

2. If the IPCC is right about climate change, we don’t have many decades to spare.

Therefore, we are either going to bake before this technology ever exists or we are going to find some other way to mitigate our emissions first.

That being said, it is an interesting long-term prospect. We may not need such trees to deal with climate change, but they could be useful for other reasons.

Tristan June 6, 2008 at 3:21 am

Does anyone honestly still believe, that if the scientists are right about what we need to do to stop catastrophic global warming, that it might be averted except than by some kind of crazy quick fix?

I mean, I’m as opposed to messing with the delicate balance of nature as much as the next guy – but do you really believe that all the rhetoric of sustainability around now is anything more than an excuse to keep doing the same things? The idea that there might be a smooth transition into sustainable living seems ridiculous, and the idea that we might tolerate anything other than a smooth transition, unbelievable. Ergo, geoengineering.

Milan June 6, 2008 at 8:49 am

Tristan,

One answer: Rather than trying to raise awareness and encourage voluntary changes in behaviour we should simply build a society with stable greenhouse gas emissions and do so in a way that requires little input and effort from almost everyone.

Critically, that society should emerge and exist without the need for most people in it to think about climate change at all. For the most part, it should occur by means of changes that aren’t particularly noticed by those not paying attention. In places where change is noticed, it is because the legal and economic structure of society now requires people to behave differently, without ever asking them to consider more than their own short term interests.

Tristan June 6, 2008 at 10:35 am

“that society should emerge and exist without the need for most people in it to think about climate change at all.”

Is this possible within democracy? Ought it even be possible?

Anon June 6, 2008 at 11:29 am

Does anyone honestly still believe, that if the scientists are right about what we need to do to stop catastrophic global warming, that it might be averted except than by some kind of crazy quick fix?

Another answer:

It is entirely possible that the transition to a low-carbon economy will be relatively painless in the long run. Lots of infrastructure needs to change, but that would need to happen anyhow once it reaches the end of its life. There are lots of opportunities for renewables and energy efficiency. Despite its problems, nuclear will play a role.

We just need to fix our eyes on the objective and work steadily towards it over the next 90 years or so.

. June 6, 2008 at 11:34 am

The International Energy Agency, a group that advises industrialized countries, said Friday in a report that investments of at least $45 trillion might be needed over the next half-century to prevent energy shortages and greenhouse gas emissions from slowing economic growth.

Nobuo Tanaka, the agency’s executive director, called for “immediate policy action and technological transition on an unprecedented scale.”

Mr. Tanaka said the world would “essentially require a new global energy revolution which would completely transform the way we produce and use energy.”

Emily June 8, 2008 at 7:00 pm

I had an interesting discussion about the shift away from using oil towards more sustainable options in the car with my uncle the other day. I think one thing that is worth having an eye on is the inevitable migration from the suburbs.

Travelling through Ontario you have vast tracts of farm land, with small suburban hubs dotted here and there. There is no available public transit, and the only method of making a living is by traveling sometimes 100’s of KM to work. Likewise, the food supply also needs to go out of its way 100’s of KM out of major urban cities in trucks needing fuel.

As gas and food prices are rising in tandem, I think we’ll see a lot of families moving into urban centres, appending to bigger cities, as they are running out of options and money. I think the complacent suburbs may ironically be the beginning place of the rumblings of an angry public wanting answers for why they can’t drive to work, and feed their families.

I think it’s maybe unwise to consider that legislation and policy can tip-toe around the problem of the questioning public. I think the momentum towards using reliable alternative energy sources may be helped by an angry, hungry working class.

. November 14, 2008 at 5:26 pm

Crassulacean acid metabolism, also known as CAM photosynthesis, is an elaborate carbon fixation pathway in some plants. These plants fix carbon dioxide (CO2) during the night, storing it as the four carbon acid malate. The CO2 is released during the day, where it is concentrated around the enzyme RuBisCO, increasing the efficiency of photosynthesis. The CAM pathway allows stomata to remain shut during the day; therefore it is especially common in plants adapted to arid conditions.

The C4 pathway bears resemblance to CAM; both act to concentrate CO2 around RuBisCO, thereby increasing usefulness. CAM concentrates it in time, providing CO2 during the day, and not at night, when respiration is the dominant reaction. C4 plants, on the contrary, concentrate CO2 spatially, with a RuBisCO reaction centre in a “bundle sheath cell” being inundated with CO2.

. June 25, 2009 at 11:32 am

News: DoE Considers Artificial Trees To Remove CO2

“CNN is running an article on a new angle of attack to reducing greenhouse gases. After meeting with the US Department of Energy on the concept, the researchers revealed the details that each ‘tree’ (really a small building structure in the concept design) would cost about as much as a Toyota and remove 1 ton of CO2 from the air per day. Don’t worry, they’re accounting for the energy the ‘tree’ uses to operate: ‘By the time we make liquid C02 we have spent approximately 50 kilojoules [of electricity] per mole of C02. Compare that to the average power plant in the US, which produces one mole of C02 with every 230 kilojoules of electricity. In other words, if we simply plugged our device in to the power grid to satisfy its energy needs, for every roughly 1,000 kilograms [of carbon dioxide] we collected we would re-emit 200, so 800 we can chalk up as having been successful.’ Each unit would remove 20 automobiles’ worth of CO2 from the air and cost about as much as a Toyota… so the plan might be a five percent surcharge on automobiles to fund these synthetic tree farms.”

. August 27, 2009 at 3:03 pm

‘Artificial trees’ to cut carbon

By Judith Burns
Science and environment reporter, BBC News

Engineers say a forest of 100,000 “artificial trees” could be deployed within 10 to 20 years to help soak up the world’s carbon emissions.

The trees are among three geo-engineering ideas highlighted as practical in a new report.

The authors from the Institution of Mechanical Engineers say that without geo-engineering it will be impossible to avoid dangerous climate change.
The report includes a 100-year roadmap to “decarbonise” the global economy.

. October 28, 2009 at 4:37 pm

Is Freeman Dyson really “brave”?

Freeman Dyson is a Nobel-winning physicist who’s argued — utterly implausibly — that carbon eating trees will save us and we shouldn’t worry about the whole climate change thing.

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