Could Radical Carbon Offsetting be Used to Absorb Atmospheric Carbon?
Last week I wrote about my despair at the idea that global leaders can ever agree to effectively slow or even reverse the growth of greenhouse gas emissions and save their peoples from the catastrophic effects of serious climate change.
I suggested that the only way to avert disaster this would be to pay fossil fuel companies to leave the gas, oil and coal in the ground because as long as it is profitable to remove it, they will do so. Just as countries with valuable rainforests need to be paid not to fell them, so companies whose profits rest upon the extraction of fossil fuels would demand to be compensated for not doing so.
The bottom line is that concentrations of greenhouse gases in the atmosphere have continued to increase regardless of any international negotiations. The challenge for Paris 2015 is to find an agreeable legal framework that every nation can sign up to that is actually effective. It does not matter what people say; only the measured results count. Given that by 2020, when any legally binding agreement takes force, we will have passed the point at which emissions can be limited to 450 ppm, it will become necessary not only to reduce emissions but also to remove carbon from the atmosphere in order to make the future safe for the majority of the human population. That is why I have come up with this proposal.
The solution I'm proposing I am calling radical carbon offsetting. Conventional carbon offsetting involves paying someone to invest in a renewable energy project. A prime example of this is the Clean Development Mechanism associated with the Kyoto Protocol, a key criteria of which is that any power generation project financed must be additional to those which would have happened anyway. But key areas of doubt have always been about whether any project can truly be additional, and whether the provision of power always leads to a thirst for more power – which may not be renewably supplied.
Radical carbon offsetting, by contrast, involves capturing carbon from the atmosphere and putting it in a place where it cannot escape, at least for the foreseeable future. Radical carbon offsetting schemes would permit the extraction of fossil fuels providing that an adequate and equivalent amount of carbon was removed from the atmosphere to that which will be released by the fossil fuels' combustion.
Fossil fuel companies would finance radical carbon offsetting schemes involving technologies some of which are traditional and some of which are currently in development and expensive but which, when they achieve scale, would be cost competitive. They would help accelerate their route to market.
Removing atmospheric carbon
Removing atmospheric carbon at scale is the only way that the current rate of increase of concentrations of greenhouse gases in the atmosphere can be reduced and perhaps even reversed so that it may reach again the safe limit of 350 ppm which it was around the middle of the last century. Currently it is at 400 ppm and the international negotiations that are ongoing are designed to limit the maximum concentration to 450 ppm, at which it is alleged global average temperature rises would peak at 2°C.
During the Eocene geological period between 56 and 34 million years ago atmospheric concentration of carbon dioxide was up to 4000 ppm. There were no ice caps and the sea level was much higher than today. The means by which it reduced to 350ppm, enabling human life to flourish, was, according to paleoceanographer and climatologist Professor Paul Pearson, through the carbonisation of calcium to create limestone. But this took millions of years.
What other, faster, techniques are there for removing carbon dioxide from the atmosphere? Below I list a few so that you can see the potential and the wide variety of opportunities that exist:
Techniques for removing atmospheric carbon
Building with timber
Simply building with timber creates a market for forest products and encourages their plantation. Provided that the trees are harvested when mature and not allowed to decay (emitting methane) then they will have absorbed a significant amount of atmospheric carbon. Using the timber in construction then locks away that carbon in the building fabric for at least the lifetime of the building. If we consider Tudor architecture and how many Tudor buildings survive today, we can see that timber is a durable construction material, so this lifetime can be long. And it's not just timber. Many building materials exist which are made from plants that will have absorbed atmospheric carbon, including forms of insulation, cladding, sheeting, flooring and so on.
Zero or negative carbon concrete
Concrete accounts for around 5-8 % of total CO2 emissions in the form of greenhouse gases, making it the third highest producer of CO2 after transport and energy generation. A major disadvantage of concrete is its large carbon footprint, one tonne of Portland cement resulting in the emission of approximately one tonne of CO2. In conventional cement manufacture the majority of the CO2 is released from the conversion of limestone (CaCO3) to lime (CaO).
Whilst there are several low carbon cement alternatives in development, only two actually absorb atmospheric carbon. These are Hemcrete and magnesium silicate cement.
Building with timber and hemcrete. Courtesy Lime Technologies.
Hemcrete, a hemp-lime composite, is sold by Oxfordshire-based Hemcrete Projects. Hemp produces a very strong fibre which is used to bind the breathable lime to create a concrete-like product. The carbon locked up in the hemp compensates for carbon produced during lime manufacture, resulting in a zero-carbon building product which is excellent at regulating temperature and humidity inside buildings. The company has combined it with hemp-based insulation and wooden frames to create two products, Hembuild – used to build the wall of a building - and Hemclad, used for cladding timber frames – that can be manufactured off-site and quickly installed during construction. Both Hembuild and Hemclad products use a layer of Hemcrete on the inside, and a layer of hemp insulation on the outside, combining thermal inertia and insulation in a single product. Together they create a kit that can be used to construct a negative carbon building.
Hemcrete does not have the same tensile or resistive strength as Portland cement, but can be used for small buildings such as houses. It could not be used for the foundations of large buildings, roads, etc., so a different product will be needed. This would instead be cement made from the accelerated carbonation of magnesium silicate (commonly known as talc) under high temperature and pressure. The resulting carbonates are then heated at low temperatures to produce magnesium oxide, with the CO2 generated being recycled back in the process.
The use of magnesium silicate eliminates the CO2 emissions from raw materials processing. Also, the low temperatures required allow the use of fuels with low energy content or carbon intensity (i.e. biomass), thus potentially further reducing carbon emissions. Furthermore, production of the carbonates absorbs carbon dioxide by carbonating part of the manufactured magnesium oxide using atmospheric/industrial CO2. A number of companies are developing this method. Overall, manufacturers claim that making one tonne of cement using this method absorbs up to 100kg more CO2 than it emits, making it a carbon-negative product.
The only disadvantage of this (besides the current cost) is that magnesium silicate is not as evenly distributed throughout the world as the calcium carbonate in limestone that is used to create Portland cement.
(Aside: other techniques for making low carbon cement such as CeraTech's, which uses a process located at power plants to convert waste fly ash (otherwise landfilled) into a cement-like product, do not sequester atmospheric carbon, although they are laudable. The same is true for the high temperature cement-making process developed at George Washington University which a patent application says could be provided by concentrated solar thermal power, yielding a low-carbon cement at a price of $43/tonne.)
Zero-carbon concrete infographic, courtesy Cemfree: similar math applies to other brands.
Duke Energy is piloting a system at East Bend Natural Gas Power Station in Northern Kentucky that recycles the carbon dioxide in flue gas to grow algae in photobioreactors. The algae can later be fed into an anaerobic digester to produce methane gas that the power plant can burn for fuel, or it can be dried and processed into fish food or animal feed, or processed into biodiesel or even jet fuel. Ways to use algae as a third generation biofuel are being pioneered by many companies across the world.
Liquid Light of Monmouth Junction, New Jersey is also intending to capture carbon dioxide from power plants' combustion processes using a technology currently being prototyped to produce ethylene glycol. This is a building block of products as diverse as polyester fibre, plastic bottles and antifreeze.
Dioxide Materials of champaign, Illinois, has another prototype in development aimed at producing acrylic acid – a constituent of paint and glue – from carbon dioxide. It has partnered with glue maker 3M to bring the product to market.
Carbon capture and storage
The last three examples place carbon capture and storage, the current great white hope of the fossil fuel industry, in perspective. Why go to all the trouble of piping the carbon dioxide to a nearby suitable geological repository when you can turn it into something profitable right on your doorstep, one might ask? The great expectations pinned upon CCS in the past have proved relatively chimeric because of the cost: power produced with add-on CCS is at least 20% more expensive – if not double the price. Yet the algae and glue- or plastic-making chemicals do not sequester the carbon – they turn it into a form which is temporarily out of the atmosphere but to which it can return (with algae almost immediately), so merely displacing fossil fuels. An advantage, true, but not as great as putting it out of reach for a century or more.
My proposal for radical carbon offsetting could provide a way of financing some of these projects and more. It would encourage innovation and new markets. I love the concept becaude it is a win-win-win solution: it has at least three benefits:
- we tackle global warming,
- create employment, and
- produce useful and valuable products that displace the need to burn fossil fuels.
To make the idea work, a global market for carbon with an appropriate price attached would be needed, plus, of course, a legal agreement that all countries in the world must sign up to. It could for example form part of the agreement being progressed for post-2015 by the UNFCCC. A summary of progress of the negotiations is here and the US' ideas for it are here. It's a distant hope for me, but at least it provides a potential route out of despair.
David is Special Consultant of this website. He's author of Energy Management in Buildings, Energy Management in Industry, Sustainable Transport Fuels, Solar Technology, Sustainable Home Refurbishment, Solar Photovoltaics Business Briefing, and much more. His new book, The One Planet Life, is due out in November. He's also a novelist, script and comics writer, journalist, and editor. He was ...
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