Saturday 9 June 2001 12:16PM (view full episode)

If CO2 is absorbed by concrete, will our high rise buildings made of concrete be weakened by the rise in atmospheric carbon dioxide. And if so, what can we do about it?


Robyn Williams: Well, President Bush has just got a scientific note confirming that the heat is on and Co2 is one of the problems. This is Graham Farquar's field. He's the one, you may recall, who topped our most quoted list of international scientists. Professor Farquar was involved with Biosphere 2, an experiment in which people tried to live in ecological isolation, depending on systems contained within a great big giant dome. The experiment produced some unexpected clues about carbon dioxide.

Graham Farquar: During my first visit to Biosphere 2 the second mission as it was called was still in progress, so there was a team of Biospherians dressed in the appropriate suit that looked like it was fresh out of a TV series, and things had happened like the oxygen level had dropped precipitously in this sealed environment because they had used a lot of organic matter in the soil to get good food yields for the Biospherians, not realising that as the organic matter oxidised it would take oxygen from the air and raise the CO2 levels to higher levels. It was a fascinating scientific problem that the oxygen had gone down to the level of Mount Everest, so people were running the whole time with altitude sickness. But the CO2 levels hadn't raised to match the depletion in oxygen. This was a mystery that was only solved by a student who was visiting reporting the matter to his father who was an engineer, a construction engineer, and being a good construction engineer he said, Well, surely it must be going into the cement.

And it turns out of course, that when you make cement you make calcium oxide which can react with carbon dioxide and make calcium carbonate. It struck me as quite an interesting thing, because I'm involved with Greenhouse accounting, in fact I'm Deputy CEO (Chief Executive Officer) of the CRC (Cooperative Research Centre) for Greenhouse accounting and the cement people are a bit put out because their activities in releasing CO2 caused by making this calcium oxide are recorded along with fossil fuel emissions, but nobody, as far as I'm aware, takes into account that as buildings age and the concrete crumbles the CO2 is taken up. So there might be some work for our CRC in dealing with cement companies in sorting that out.

And also, it means I suppose, that as the CO2 levels rise, as they continue to do, that concrete will age more quickly.

Robyn Williams: How severe?

Graham Farquar: I've not done the calculations, but carbon dioxide diffuses into the rock and the sort of equations people used to finally solve the mystery of Biosphere 2 seem to be the kind of equations that building engineers use all the time, and I assume it's just proportional to the concentration. And so I guess we are probably aging concrete now two and a half times as quickly as we were at the beginning of the industrial revolution.

Robyn Williams: So, it has become noticeable already, presumably?

Graham Farquar: Yes, well it was an issue that this construction engineer was conscious of, but I've not seem much press about it in the reports, and I do follow many of them, but of course it's not exactly my area since I work mainly in vegetation. But having said it on radio, now I suppose I'd better look into it.

Robyn Williams: I must say it's a bit of a worry with all these huge buildings going up if C02 is becoming more concentrated in the atmosphere, there's more of it and therefore the effect is more substantial, two and a half times as you said. Then we'd better look carefully and quick.

Graham Farquar: Yeah, I am speaking as a complete novice here and it may well be that building researchers here in Australia have already done such calculations, and if it hasn't been done I'll get some calculations started.

Robyn Williams: Going to the fundamental work you are doing in using plants as sinks for Greenhouse, I've seen, even in the last few days, there's been some noise about how much trees, forests, pine plantations can actually take out. How do you view the potential of planting trees as a sink for CO2 at the moment?

Graham Farquar: Well, we see planting trees as a very useful thing to do in the short term to buy time, perhaps only a decade or so's worth of uptake. But when you look at the infrastructure that's involved in the supply of energy, it's a big aircraft carrier to turn around and it's really a bit unfair to ask society, that's invested a lot of money, to completely stop the big aircraft carrier with possible consequent changes to the economy, too fast. I think we need to work on all kinds of fronts and the nice thing about our work with terrestrial carbon sinks is that, in many cases, we're talking about responses that you might like to see for other reasons.

I mean, many people report to us how appalled they are by the degradation in areas of the country that has been overgrazed and so on, and the kinds of environmental rehabilitation that many people would like to see have never had the sustained economic backing that's required from farmers to do what they themselves would like. I mean, often I find, speaking to land owners, that they are much more aware of what's going on than those of us living in cities but they are caught between a rock and a hard place. They have to make a quid and feed the kids so to speak, and it's with them in mind that I say it could be that some carbon economy, if properly managed, might just provide the bit of financial glue that would enable us to stick together the kinds of rehabilitation programs we'd like to see, maintaining biodiversity and so on, while simultaneously reducing the build up of CO2 levels from what they otherwise would have been.

Robyn Williams: Graham Pearman, (Chief, CSIRO Atmospheric Research) just came back from overseas and said there's a consortium ready to use that famous dumping of iron in the ocean as a means to form a carbon sink. It works, does it not, by fostering the growth of certain life forms which can then take up the CO2? Apparently, they are free to go ahead because the law of the sea can't stop them. Or it seems so at the moment. Do you think that's a promising venture?

Graham Farquar: I hasten to say that it's something that needs to be looked at and examined. But like it says, there are two kinds. One for the longer-term ecological consequences. I mean, presumably the primary fixes will respond, those that are limited in iron. Presumably the things that eat those primary producers will also respond, so it's not clear to me for how long there is a gain. I hope that there are good marine biologists involved in the assessment.

Nevertheless, there are a lot of things that can happen, particularly here in Australia, because it's so stable geologically and because we've got such expertise in mining. There's a lot of potential for putting CO2 underground, and I was pleased to hear from people at the Australian Petroleum Exploration Association Meeting in Hobart recently, that this is something that can go when the price signal is there - and the signal doesn't actually have to be that large Robyn. So it's quite interesting that if society wished to do so they could sequester a lot of carbon underground. I would like to say though, that it's important in all these things that we keep looking hard at the basic science - even at the most fundamental levels - about the Greenhouse that are not well understood. Research in the area has to continue and all the basic assumptions have to be tested and re-tested to make sure we're following the right track.

Robyn Williams: Very quickly, how would you sequester this carbon underground in mines and so on?

Graham Farquar: Well, carbon dioxide is already used to force the last amounts of oil from oil wells, one adapts the same process. One forces the CO2 underground and caps it. It's best to do it of course at the site where the CO2 is produced, and so one foresees where CO2 could go down into either pre-existing mines or perhaps into oil wells in areas that are geologically stable, in the North West shelf you know may be such an example.


Professor Graham Farquar
Deputy CEO, Cooperative Research Centre for Greenhouse Accounting Professor of Environmental Biology
Research School of Biological Sciences
Institute of Advanced Studies
Australian National University
GPO Box 475
Canberra City ACT 2601 Australia
Fax: +61 (0)2 6125 4919


Robyn Williams
Polly Rickard