Following my post, Carbon Sequestration; what no-one tells you, I received a couple comments from a reader, pointing out the potential of chemical sequestration, commonly referred to as enhanced weathering.
Of course, none of this was provided with case studies or research into it’s viability and the individual quickly left the conversation, having made their point.
But it’s worth reviewing, because I’m becoming increasingly aware of two camps, both very distinct, but sharing an absolutism approach to their favoured climate change mitigation strategy; the pro-nukes and the sequestration mob. Both are sure that their answer is the one and only true reply, but neither stack up.
I won’t bother here with the pro-nukes, because I’ve discussed them various times in the past.
Yes, biological sequestration is only one possibility. Even the modest targets set by the current Australian government within “direct action” represent massive effort, as my analysis showed. However, there is another, apparently low energy, form of sequestration which relies on rock chemically reacting with atmospheric CO2 to capture it.
This is know as “enhanced weathering” as it is a natural process in itself and what the fans of this want to do is speed it up. It’s euphemism for enhanced erosion. I’ll get to the numbers in just a moment, but we’re talking about billions of tonnes of material needed, to match the CO2. Who honestly believes that mining to this degree is viable, let alone desirable when we factor in the necessary impact to landscapes and aquatic environments both through the direct mining activities and resulting compounds as residue from this process, which will hit environments (unless we go to even greater effort and expense to again bury it) in far great amounts than the background levels?
As for numbers, looking at the Azimuth Project, two minerals that could be used for this process are Olivine and Serpentine.
The ratios for these;
|Molar Mass (g/mol)||44.01||203.77||140.69||371.73||277.11|
|Weight ratio to CO2||1||4.63||3.2||8.45||6.3|
|Molecules requires for every CO2||–||0.25 to 1||0.25 to 1||0.25||0.25|
|1 unit weight of CO2 requires how many units?||–||1.6 to 4.63||0.8 to 3.2||2.11||1.57|
Annual emissions of CO2 reached 34.5 billion tonnes in 2012. Therefore, for Olivine or Serpentine to capture all of this, we would need between 27.6 and 159.74 billion tonnes of these rocks annually.
From the Azimuth Project page;
Supposedly all the CO2 that is produced by burning 1 liter of oil can be sequestered by less than 1 liter of olivine. The market value of olivine is US $50 to US $100 per ton depending on quality. Plugging in the larger number then 5 trillion dollars a year of this material would absorb all the CO2 currently produced. But of course this calculation is oversimplified, since the spike in demand would send the price much higher.
None of this begins to address the billions of tonnes of residue materials as well.
Some might say that I’m being unfair – most targets aim at around 5% below, say 2000 or 1990 levels. To be generous, let’s say the emissions value was 25 billion tonnes, meaning that we want to reach emissions targets below 23.75 billion tonnes. This means that we want to capture 10.75 billion tonnes of CO2 based on 2012 levels.
This amounts to between 8.6 and 49.77 billion tonnes of Olivine and Serpentine annually for enhanced weathering. This is still a massive industry devoted entirely to scrubbing the atmosphere of our CO2 emissions.
The Australian Prime Minister, Tony Abbott, may call emissions trading a “so-called market in the non-delivery of an invisible substance to no one,” but how can sequestration be anything but a non-delivery market, as much a sink of money as it is carbon?
It doesn’t matter whether you rely on trees, soil, weathering or any other mechanism, sequestration is not the cheap and easy solution that it has been sold as. In every case you are also left with a bank that is useless unless it keeps carbon locked and what then of this material?
There is no such thing as a silver bullet. Reducing our emissions will require a lot of effort, behavioural change and a diversity of solutions, each contributing their own small part. Thus far, very little of this is being addressed or adopted above the barest effort.