Welcome to the Cquestrate blog
We have recently commissioned two pieces of research to develop the process.
The first part addresses the Energy Balance of the process – how much energy is required to drive the process? While we know how much energy is required to thermally decompose (calcine) limestone into lime and carbon dioxide (this is after all what people in the lime industry do every day), we need to change the process slightly, so that we are able to capture pure carbon dioxide, which is much easier to sequester. Through contacts from this website I have been in touch with the German Lime Association who have been able to provide some very useful and encouraging information on current energy requirements and indications on what the requirements for the altered system might be. At the same time as we are gathering empirical data, we are also creating a computer model of the energy requirements of the altered calcination system – this work is being undertaken by Dr Panos Parris and Dr George Manos both at University College London. They will be reporting out in the first week in September.
The second piece of research is on the environmental impact of adding the lime to seawater. This work is being carried out by Professor Gideon Henderson, Dr Heather Bouman and Dr Ros Rickaby, all at the Department of Earth Sciences at the University of Oxford. This research will be a preliminary assessment of the effects of the process and will identify further areas of research to determine whether, and how, this process can be conducted in an environmentally beneficial way. They will be reporting out in the middle of September.
As part of the open source approach we are taking, we will publish the research results on the website as soon as we receive them
A number of posts have referred to the amount of energy that is required to distribute the lime to the oceans. The cost will be significant, but in energy terms 85-95% of the energy used in the manufacturing of lime (from mining the limestone out of the ground, crushing it and transporting it and heating it up until it calcines into lime and CO2) is required in the form of heat. The total heat energy requirement is approximately 2GJ per tonne of limestone calcined which yields a figure of approximately 3GJ per tonne of CO2 sequestered. The exact amounts will depend on the exact process (how much heat from the CO2 generated is recaptured, etc).
Unless we can generate electricity extremely cheaply it is likely to be too expensive to drive this process. Here’s why: 1 kilowatt-hour is 3.6MJ – so 1GJ is approximately 278 kWhrs. If you have cheap electricity at say $0.05 per kWhr, then to generate 1GJ will cost ~$14. In comparison, natural gas can be much cheaper. There are numerous deposits of ’stranded gas’ where the cost of extracting the gas out of the ground is less than $1 per GJ, but it would cost so much to transport to a market, that it is not worth doing so. Because this process can be performed anywhere where limestone, energy and the sea are in close proximity, it is possible to use that stranded gas.
Electricity is an extremely high-quality form of energy, which is absolutely necessary to run our modern society (including this computer). But for this process we require heat, not high-quality energy and the process of turning heat (from say a power station) into electricity and then turning the electricity into heat is inefficient and unnecessary. Better to use heat directly.
Thank you to Steaphany Waelder who sent me an email with some contacts in Australia who are investigating generating high-grade heat from solar irradiation. This is exactly the sort of information that we are looking for. If we can use solar irradiation that would be ideal, as there would be no CO2 from heat generation – my concern is the cost of the equipment and that is what we will be looking into.
Thank you also to Henry Brown with his post on Opensource maps. The code you have written at the end of your post is, I’ll admit, quite beyond me, but I’m told by someone who knows that this will generate maps of the various elements that we need to pull together – genius!
With a couple of days left before the website launches we’re just finalising content, producing explanatory videos and making sure that everything is working properly.
We’ve had to move very quickly to ensure that everything is in place as soon as possible. With the first phase of the website almost complete it’ll soon be a case of making sure that word goes out to the people who can help further this project.
The scope is so large that we need a wide spread of expertise – if you, or anyone you know anyone, can help in any way then we look forward to your input. Have a look at the questions we need to answer and leave your comments on the relevant pages.
The idea works like this:
- First, you heat limestone to a very high temperature, until it breaks down into lime and carbon dioxide.
- Then you put the lime into the sea, where it reacts with carbon dioxide dissolved in the seawater.
The important point is that when you put lime into seawater it absorbs almost twice as much carbon dioxide as is produced by the breaking down of the limestone in the first place.
This has the effect of reducing the amount of carbon dioxide in the atmosphere. It also helps to prevent ocean acidification, another problem caused by the increase in the amount of carbon dioxide in the atmosphere.
If done on a large enough scale it would be possible to reduce carbon dioxide levels back to what they were before the Industrial Revolution.
The first step of the process – breaking down limestone into lime and carbon dioxide – seems counterintuitive as it uses a lot of energy and actually produces carbon dioxide. But this carbon dioxide can either be safely stored away or used to help grow crops in very dry areas. You can find out more about this here.
One of the questions I often get asked is: if this is so simple why hasn’t it been done before? The idea has been around for a number of years. It was first suggested by Haroon Kheshgi in 1995, but it was considered uneconomic as the process uses a large amount of energy. What we are interested in doing is using stranded energy to drive the process.
Stranded energy is energy that is remotely located, so it is not economically viable to exploit. For example, in a desert there is plenty of energy available, but it would cost too much to transfer the energy to where anyone wants it, so it never gets used. So, paradoxically, in a desert energy is abundant and cheap, but worthless. This process can use that stranded energy.
We couldn’t have got this far without the help of a large number of people who have been extremely generous with their time and expertise. We are developing this project in an open source way, so, if you are interested to help, please get involved.