As aforementioned there are currently 74 active CSS projects happening all over the world. They can all be viewed here, but I'm going to quickly look at what England is doing with this technique.
There are 4 developing projects happening in the UK to date. Two of the potential schemes are being implemented in Teesside and Lincolnshire, and both use pipelines to transfer pre-combusted carbon into local geology. Both should be complete by 2016 and are in mid-stages of development and testing.
The third project in North Yorkshire is slightly different; whereby the CO2 will be injected into saline formations. As opposed to pre-combustion, the capture type is oxy-combustion, whereby the fossil fuel is burned with pure oxygen as opposed to air and releases almost no nitrogen.
The final project is nearby in South Yorkshire differs slightly, as CO2 will be injected under the North Sea geology to aid oil and gas recovery, and qualified for EPPR funding due to the potential of developing a cluster of sites around the Humber area.
This shows the EU is considering CSS as a serious option for removing atmospheric CO2. Currently the UK government funds CSS through 5 bodies (Department of energy and climate change), and I expect in the future this number will grow; as will the number of CSS projects in England and the whole of the UK.
Wednesday, 28 December 2011
Tuesday, 20 December 2011
CSS
Moving into the 21st century now, carbon capture and storage (CSS) is the newest technique pioneered in 2000 by Weyburn. It's a method of CDR and technologies are currently being developed and applied in 74 countries on a global scale, displayed rather nicely on this interactive map.
CSS stops CO2 being released into the atmosphere at industrial sites by capturing it before it's released. It is then transported via large pipelines (the cheapest way) and stored in geology, deep oceans or in minerals. I'll dwell on the storage options a bit because I think it's interesting
.
Storage in geology
The CO2 is injected into underground formations and be prevented from escaping by physical and geochemical trapping mechanisms:
Diagram illustrating the possible areas of carbon storage underground (Source: Global CSS Institute).
Potential sites for geological storage (IPCC special report)
CO2 can be transported via ships or pipelines to an ocean storage site deep below the thermocline, where it will remain for 100-1000 years out of contact with the atmosphere.
Some ways of ocean injection and storage (IPCC full report)
Mineral storage
Chemical reactions between metal oxides in silicate rocks and CO2 produce carbonates and silica which lock away carbon potentially forever. Ideal materials would be those such as magnesium oxide or calcium oxide; which are naturally abundant, but oxides can also be found in industrial waste. Once the materials are carbonised they will retain the carbon and not leak it back to the atmosphere, making this technique superior in terms of storage. Additionally, this will mean the storage areas will not need to be monitored. The diagram below summarises the technique:
(IPCC)
So it can be reused if it isn't disposed which is unique for CSS.
Potential problems
- High energy requirements
- Cost (although I think relatively cheap compared to other things I've looked at)
- Leakage, especially with ocean storage
- Negative ecological consequences (eg. ocean acidification)
- Carbon may enter groundwater supplies
Overall I think this is a really good idea! CO2 could potentially be stored in geology for millions of years (IPCC), with a 99% likelihood of them retaining the injected Carbon, and if mineral storage is employed it will remain there forever and never escape. Oceans cover 70% of the Earth so they also hold huge potential to keep carbon locked away if buried deep enough.
Humans are less directly affected by offshore burial; with geological storage there is that 1% chance of leakage into soil or groundwater but due to cycling in the ocean acidification is likely to eventually occur; causing a threat to biodiversity.
These reports are really detailed and have everything you'll need to know ever on CSS:
IPCC summary
Full report
CSS stops CO2 being released into the atmosphere at industrial sites by capturing it before it's released. It is then transported via large pipelines (the cheapest way) and stored in geology, deep oceans or in minerals. I'll dwell on the storage options a bit because I think it's interesting
.
Storage in geology
The CO2 is injected into underground formations and be prevented from escaping by physical and geochemical trapping mechanisms:
- injections into oil fields increases the amount of crude oil extraction - this technique is done often in the USA (IPCC 2010).
- In unmineable coal seams, CO2 molecules stick to the coals surface and is absorbed. However, this displaces some of the methane the coal contains, which would either have to be sold, or burned which would offset the positive storage effects.
- Saline water saturated reservoirs are common, have a large area for storage and are of no use to humans. They are currently used in some places to store chemical waste, but more research needs to be done in terms of trapping and leakage as relatively little is known about them in comparison to oil fields or coal seams.
CO2 can be transported via ships or pipelines to an ocean storage site deep below the thermocline, where it will remain for 100-1000 years out of contact with the atmosphere.
- Ship or pipeline injections at 1000-3000m below the surface, forming plumes or lakes.
- Plumes either rise or sink depending on and concentration. Rising plumes causes CO2 to dissolve in the water column. Sinking plumes are more dense and so sink along and inclined seafloor.
- Carbon lakes are reservoirs created at injection depths greater than 3000m.
- Alternatives including combining CO2 with a carbonate such as limestone and depositing it in the deep ocean, or adding carbon to existing clathrates.
Mineral storage
Chemical reactions between metal oxides in silicate rocks and CO2 produce carbonates and silica which lock away carbon potentially forever. Ideal materials would be those such as magnesium oxide or calcium oxide; which are naturally abundant, but oxides can also be found in industrial waste. Once the materials are carbonised they will retain the carbon and not leak it back to the atmosphere, making this technique superior in terms of storage. Additionally, this will mean the storage areas will not need to be monitored. The diagram below summarises the technique:
So it can be reused if it isn't disposed which is unique for CSS.
Potential problems
- High energy requirements
- Cost (although I think relatively cheap compared to other things I've looked at)
- Leakage, especially with ocean storage
- Negative ecological consequences (eg. ocean acidification)
- Carbon may enter groundwater supplies
Overall I think this is a really good idea! CO2 could potentially be stored in geology for millions of years (IPCC), with a 99% likelihood of them retaining the injected Carbon, and if mineral storage is employed it will remain there forever and never escape. Oceans cover 70% of the Earth so they also hold huge potential to keep carbon locked away if buried deep enough.
Humans are less directly affected by offshore burial; with geological storage there is that 1% chance of leakage into soil or groundwater but due to cycling in the ocean acidification is likely to eventually occur; causing a threat to biodiversity.
These reports are really detailed and have everything you'll need to know ever on CSS:
IPCC summary
Full report
Tuesday, 13 December 2011
Surface albedo enhancement
As I'm concious I'm running out of time to complete this, I'm going to lump several surface albedo techniques into one; and evaluate which one I think is better. Rather than dwell on scientific papers I'll link to some I've read on the subject incase you want to challenge my opinion!
The idea of enhancing surface albedo
It's less efficient that enhancing atmospheric albedo, as less radiation reaches the surface, but it is obviously much more practical. Albedo is a measure of how much incoming radiation is reflected back to space, an is measured on a scale of 0-1, where 0 is 0% reflection and 1 is 100%. In context, the albedo of black asphalt is about 0.1, whereas fresh snow is about 0.9 (Gaskill).
Total reflectivity of the Earth's surface is measured at around 0.09, which is an averaged value. Different landsurfaces have different albedo values, which should be accounted for in more localised studies of albedo effects. The book by Alvia Gaskill has some good summary chapters; it's short and readable and available online.
Ways of enhancing
This idea isn't new; it's commonly known that white keeps you cooler and black makes you hotter in the summer. I'm looking at 3 larger-scale ideas to keep the whole planet a bit cooler.
Cool Roofs
'Cool roofs' reflect more sunlight and absorb less radiation than your average dark roof. This is achieved in 3 ways:
There are loads of case studies with regards to cool roofs but I have chosen a recent one from India just to give some exemplary figures:
-Buildings with cool roof coatings were measured for energy savings and emissions reductions.
-Higher reflectance lowered roof temperatures and heat flux throughout the buildings in comparison to roofs with low reflectance.
-As a result, cool roofs saved 20 to 22 kWh/m2 roof area of energy, and used 14-26% less air conditioning energy.
-Direct CO2 reductions due to lower energy usage were estimated to be 11–12 kg CO2/m2 of flat roof area per year (Xu et al. 2012).
Indirect benefits from white roofs can be felt in the environment around the buildings, such as cooling outside air, reducing GHG emissions and decreasing smog, leading to better environmental and health status. Doing this globally can reduce energy and its associated GHG emissions. 70% of buildings in the USA can improve the reflectivity of their roofs (Jo et al. 2010), and the US government take this technique very seriously as they will install a cool roof on any new building or replacement of an old roof for free.
I think there are a huge potential for cool roofs and it's something at a local scale which can be easily applied to help on a global scale to cool the planet.
Desert reflectors
In my opinion this idea seems a very farfetched - covering 60,000km2 of the desert in a reflective sheet? Although potentially it will lead to net cooling very quickly (ScienceDaily 2008) and offset the current level of warming, it does nothing to ease our reliance on fossil fuels or removal of carbon. Also the above article says it is a fairly minimal cost of $280 billion, but that's one of the most expensive techniques I've come across so far, perhaps even the most costly (if you look back to my introduction)! An unpublished paper by Irvine et al (in press) suggests this technique should not be favoured over atmosphere or space based SRM methods. It states these desert mirrors will alter circulation and change the hydrological cycle on a global scale; by lessening precipitation over land and reducing the Indian and African monsoons by as much as 50%. Maybe utilising solar power in desert regions may be a more effective use of land.
Reflective Crops
Potentially a 'high albedo diet' could also contribute to global cooling - this involves normal crops being replaced with GM'd ones, with a strain of higher reflectivity. The technique could take as long as 10-15 years to become effective, as once farmers are encouraged (probably with money) to adopt the new GM varieties, they also need time to be swapped and grown. If anything farmers are likely to see an increase in productivity as a result of using reflective plants, which is also a bonus.
Some figures then - pioneers Ridgwell et al (2009) suggest areas of the world with intense agricultural practices, such as Eurasia and much of N. America could experience summers cooler by at least 1°C.
Unfortunately in a global context, it won't be enough to to offset the positive forcing of doubling CO2 (3.7W/m2), it will only give 0.44W/m2 of globally averaged negative forcing (Lenton and Vaughan 2009). However it is important to remember in this case every little helps, and this is affordable and achievable!
Other
Just as an aside, techniques such as modifying ocean albedo have been suggested (by applying more of that expensive plastic sheeting, adding bubbles amongst other ways) but I won't dwell on them because I don;t think they're particularly important.
In Conclusion:
As with anything, these 3 ways of altering surface albedo have their associated pros and cons. Cool roofs is good at a local scale for reducing the urban heat island effect - the effect is also measurable and the technology is readily available and comparable. The technique has hundreds of case studies associated with it and is probably best at indirectly cooling the planet by reducing the demand for electricity. It does nothing to remove CO2 from the atmosphere and is dependent on climate, but is backed by many reputable organisations and governments on a global scale.
I think it's too risky to implement desert reflectivity sheets, as they alter global climate in a huge way. It has too many unsafe effects compared to the other 2 techniques - it is also extortionately expensive and when viewed within the bigger picture of global geoengineering methods; there are cheaper and more effective methods available.
Lastly, enhancing reflectivity of crops.only for arable areas. sees more local change. I very much like this as I'm in favour of GMing things for our benefit. Although this has lots of moral and ethical issues attached, so does any geoengineering technique and I think it's great if we can modify something we already have for our own benefit without causing any harm. There are very few risks associated with this and it is fairly simple to achieve, as well as being cost effective. Unfortunately, it is limited to arable areas of the world, and produces more local changes which means it is not entirely suitable for producing global cooling.
The winner then of the best method of surface albedo enhancement is 'cool roofs', due to it's global applicability and proven effectiveness, the low level of technology involved and the amount of positive case studies associated with its implementation.
The idea of enhancing surface albedo
It's less efficient that enhancing atmospheric albedo, as less radiation reaches the surface, but it is obviously much more practical. Albedo is a measure of how much incoming radiation is reflected back to space, an is measured on a scale of 0-1, where 0 is 0% reflection and 1 is 100%. In context, the albedo of black asphalt is about 0.1, whereas fresh snow is about 0.9 (Gaskill).
Total reflectivity of the Earth's surface is measured at around 0.09, which is an averaged value. Different landsurfaces have different albedo values, which should be accounted for in more localised studies of albedo effects. The book by Alvia Gaskill has some good summary chapters; it's short and readable and available online.
Ways of enhancing
This idea isn't new; it's commonly known that white keeps you cooler and black makes you hotter in the summer. I'm looking at 3 larger-scale ideas to keep the whole planet a bit cooler.
Cool Roofs
'Cool roofs' reflect more sunlight and absorb less radiation than your average dark roof. This is achieved in 3 ways:
- Being inherently cool - i.e. the roof is made from a material with high reflectivity, for example thermoplastic white vinyl.
- Coated roofs - new or existing roofs are made reflective my applying a special coating. You can look at coated roof product ratings here to decide on the best one.
- Green roofs - A plant is grown on the roof - it reflects less and absorbs more, but this absorbed heat is balanced by evapotranspiration.
There are loads of case studies with regards to cool roofs but I have chosen a recent one from India just to give some exemplary figures:
-Buildings with cool roof coatings were measured for energy savings and emissions reductions.
-Higher reflectance lowered roof temperatures and heat flux throughout the buildings in comparison to roofs with low reflectance.
-As a result, cool roofs saved 20 to 22 kWh/m2 roof area of energy, and used 14-26% less air conditioning energy.
-Direct CO2 reductions due to lower energy usage were estimated to be 11–12 kg CO2/m2 of flat roof area per year (Xu et al. 2012).
Indirect benefits from white roofs can be felt in the environment around the buildings, such as cooling outside air, reducing GHG emissions and decreasing smog, leading to better environmental and health status. Doing this globally can reduce energy and its associated GHG emissions. 70% of buildings in the USA can improve the reflectivity of their roofs (Jo et al. 2010), and the US government take this technique very seriously as they will install a cool roof on any new building or replacement of an old roof for free.
I think there are a huge potential for cool roofs and it's something at a local scale which can be easily applied to help on a global scale to cool the planet.
Desert reflectors
In my opinion this idea seems a very farfetched - covering 60,000km2 of the desert in a reflective sheet? Although potentially it will lead to net cooling very quickly (ScienceDaily 2008) and offset the current level of warming, it does nothing to ease our reliance on fossil fuels or removal of carbon. Also the above article says it is a fairly minimal cost of $280 billion, but that's one of the most expensive techniques I've come across so far, perhaps even the most costly (if you look back to my introduction)! An unpublished paper by Irvine et al (in press) suggests this technique should not be favoured over atmosphere or space based SRM methods. It states these desert mirrors will alter circulation and change the hydrological cycle on a global scale; by lessening precipitation over land and reducing the Indian and African monsoons by as much as 50%. Maybe utilising solar power in desert regions may be a more effective use of land.
Reflective Crops
Potentially a 'high albedo diet' could also contribute to global cooling - this involves normal crops being replaced with GM'd ones, with a strain of higher reflectivity. The technique could take as long as 10-15 years to become effective, as once farmers are encouraged (probably with money) to adopt the new GM varieties, they also need time to be swapped and grown. If anything farmers are likely to see an increase in productivity as a result of using reflective plants, which is also a bonus.
Some figures then - pioneers Ridgwell et al (2009) suggest areas of the world with intense agricultural practices, such as Eurasia and much of N. America could experience summers cooler by at least 1°C.
Unfortunately in a global context, it won't be enough to to offset the positive forcing of doubling CO2 (3.7W/m2), it will only give 0.44W/m2 of globally averaged negative forcing (Lenton and Vaughan 2009). However it is important to remember in this case every little helps, and this is affordable and achievable!
Other
Just as an aside, techniques such as modifying ocean albedo have been suggested (by applying more of that expensive plastic sheeting, adding bubbles amongst other ways) but I won't dwell on them because I don;t think they're particularly important.
In Conclusion:
As with anything, these 3 ways of altering surface albedo have their associated pros and cons. Cool roofs is good at a local scale for reducing the urban heat island effect - the effect is also measurable and the technology is readily available and comparable. The technique has hundreds of case studies associated with it and is probably best at indirectly cooling the planet by reducing the demand for electricity. It does nothing to remove CO2 from the atmosphere and is dependent on climate, but is backed by many reputable organisations and governments on a global scale.
I think it's too risky to implement desert reflectivity sheets, as they alter global climate in a huge way. It has too many unsafe effects compared to the other 2 techniques - it is also extortionately expensive and when viewed within the bigger picture of global geoengineering methods; there are cheaper and more effective methods available.
Lastly, enhancing reflectivity of crops.only for arable areas. sees more local change. I very much like this as I'm in favour of GMing things for our benefit. Although this has lots of moral and ethical issues attached, so does any geoengineering technique and I think it's great if we can modify something we already have for our own benefit without causing any harm. There are very few risks associated with this and it is fairly simple to achieve, as well as being cost effective. Unfortunately, it is limited to arable areas of the world, and produces more local changes which means it is not entirely suitable for producing global cooling.
The winner then of the best method of surface albedo enhancement is 'cool roofs', due to it's global applicability and proven effectiveness, the low level of technology involved and the amount of positive case studies associated with its implementation.
Tuesday, 6 December 2011
Space mirrors
This idea was first considered in the 1980s as a way to cool Venus, and was adapted in 1989 by James Early who suggested creating a large shade (2000km diameter) to block the suns radiation. The cost of something like this is huge (between $1-10trillion) so although it is being considered as a way to reverse climate change, it remains hugely controversial.
How it works
Essentially, objects are sent into space to block the suns rays and lower Earth's insolation, making this a SRM technique. Proposed designs include a huge, single piece shade or a shade composed of trillions of smaller objects. As well as just deflecting radiation, these objects could potentially be used as solar power satellites.
Whether the shade is 1 huge object or made of trillions of smaller ones, both would be situated in space at the Sun-Earth Lagrangian point (L1):
L1 lies about 1.5million km from Earth, and is the only point where an object here will have an orbital period exactly the same as Earth's. Another way to think of it is that any object closer to the sun than Earth will eventually 'overtake' and move away, because the distance round the sun is shorter. At L1, Earth's gravity intensifies and weakens the pull of the sun. Therefore, if the space mirrors are placed just right; they will maintain position between Sun and Earth and be able to prevent some of the Sun's radiation reaching Earth.
A cloud of small spacecraft
Firstly I'll look at creating the shade out of trillions of small objects. Roger Angel is a key researcher in this field and has obtained several grants to further the research into developing this technique. One paper assesses the feasibility of such a huge project..
Starting with the conclusion, Angel (2006) declares 'the same massive level of technological innovation and financial investment needed for the sunshade could, if also applied to renewable energy, surely yield better and permanent solutions." Which makes me wonder why he bothers with any of this and doesn't spend time researching renewables instead, but I digress.
The concept is a 'cloud' of free-flying spacecraft at a length of ~100,000km along the L1 point. Instead of being mirrors, transparent material would be used to deflect the path of radiation (to minimise radiation pressure which may throw them off orbit). This should reduce the sun's heat input by 1.8%, enough to reverse the effects of global warming.
The environmental impact is terrible if electricity is required, coal would be the worst case scenario, needing 30kg of coal for every 1kg of spacecraft launched. So the technique worsens the emissions problem, and although it will offset the emissions it makes from launch it doesn't remove carbon from the environment!
And all this can be yours for a few trillion dollars. I think this is all very clever but I must agree with Angel, maybe investing trillions in a permanent solution would be more sensible.
Alternatively, Early (1989) proposes a 2000km diameter shield, 10μ thick made by moon materials placed in the L1 to block 2% radiation from the Sun. Similarly, this project is also extortionately priced, in the range of $1-10 trillion. As far as I can tell it is similar to Angel's proposition in terms of proportion of radiation blocked and cost, the main difference being more of the work in terms of constructing the shield would have to occur in space, which in itself is less feasible.
So overall then, this is the most expensive geoengineering technique I've come across so far, at between $1-10 trillion. The vagueness in the figure itself highlights the fact more research is needed for this idea if it is ever to be put into practice. The simplicity of it; sending an object into space to block radiation is amazing but the infrastructure and technology required to achieve it is impractical. I feel there might be other ways more suitable to reversing climate change, but still don't think this should be ruled out as it has huge potential to reverse over 150 years of damage.
Angel, R. (2006) 'Feasibility of cooling the Earth with a cloud of small spacecraft near the inner Lagrange point (L1)', Proceedings of the National Academy of Sciences in the United States of America, 103, 46, 17184-17189.
Early, J. T. (1989) 'Space-based solar shield to offset greenhouse effect', Journal of the British Interplanetary Society, 42, 567-569.
How it works
Essentially, objects are sent into space to block the suns rays and lower Earth's insolation, making this a SRM technique. Proposed designs include a huge, single piece shade or a shade composed of trillions of smaller objects. As well as just deflecting radiation, these objects could potentially be used as solar power satellites.
Whether the shade is 1 huge object or made of trillions of smaller ones, both would be situated in space at the Sun-Earth Lagrangian point (L1):
L1 lies about 1.5million km from Earth, and is the only point where an object here will have an orbital period exactly the same as Earth's. Another way to think of it is that any object closer to the sun than Earth will eventually 'overtake' and move away, because the distance round the sun is shorter. At L1, Earth's gravity intensifies and weakens the pull of the sun. Therefore, if the space mirrors are placed just right; they will maintain position between Sun and Earth and be able to prevent some of the Sun's radiation reaching Earth.
A cloud of small spacecraft
Firstly I'll look at creating the shade out of trillions of small objects. Roger Angel is a key researcher in this field and has obtained several grants to further the research into developing this technique. One paper assesses the feasibility of such a huge project..
Starting with the conclusion, Angel (2006) declares 'the same massive level of technological innovation and financial investment needed for the sunshade could, if also applied to renewable energy, surely yield better and permanent solutions." Which makes me wonder why he bothers with any of this and doesn't spend time researching renewables instead, but I digress.
The concept is a 'cloud' of free-flying spacecraft at a length of ~100,000km along the L1 point. Instead of being mirrors, transparent material would be used to deflect the path of radiation (to minimise radiation pressure which may throw them off orbit). This should reduce the sun's heat input by 1.8%, enough to reverse the effects of global warming.
- Total sunshade mass = ~20 million tonnes.
- Transportation cost = $50 per kg.
- The instruments are built on the ground and sent up to avoid the need of an unfolding mechanism.
- Each instrument weighs roughly 1g and would be launched in stacks of 800,000
- Each instrument would last 50 years
The environmental impact is terrible if electricity is required, coal would be the worst case scenario, needing 30kg of coal for every 1kg of spacecraft launched. So the technique worsens the emissions problem, and although it will offset the emissions it makes from launch it doesn't remove carbon from the environment!
And all this can be yours for a few trillion dollars. I think this is all very clever but I must agree with Angel, maybe investing trillions in a permanent solution would be more sensible.
Alternatively, Early (1989) proposes a 2000km diameter shield, 10μ thick made by moon materials placed in the L1 to block 2% radiation from the Sun. Similarly, this project is also extortionately priced, in the range of $1-10 trillion. As far as I can tell it is similar to Angel's proposition in terms of proportion of radiation blocked and cost, the main difference being more of the work in terms of constructing the shield would have to occur in space, which in itself is less feasible.
So overall then, this is the most expensive geoengineering technique I've come across so far, at between $1-10 trillion. The vagueness in the figure itself highlights the fact more research is needed for this idea if it is ever to be put into practice. The simplicity of it; sending an object into space to block radiation is amazing but the infrastructure and technology required to achieve it is impractical. I feel there might be other ways more suitable to reversing climate change, but still don't think this should be ruled out as it has huge potential to reverse over 150 years of damage.
Angel, R. (2006) 'Feasibility of cooling the Earth with a cloud of small spacecraft near the inner Lagrange point (L1)', Proceedings of the National Academy of Sciences in the United States of America, 103, 46, 17184-17189.
Early, J. T. (1989) 'Space-based solar shield to offset greenhouse effect', Journal of the British Interplanetary Society, 42, 567-569.
Tuesday, 29 November 2011
Palaeo BioChar
The creation of biochar (or Terra Preta) is a technique with huge potential for carbon sequestration.
However, this is not a new innovation - it turns out it's been used for thousands of years by the pre-Columbian Amazonians. So although it has a huge potential for present and future climate change mitigation, I'm going to investigate terra preta in a palaeo-geoengineering context.
Here's a little video which is quite good at explaining the concept, it focuses on Australia and features the first Australian agrichar farm:
But aside from that, instead of reviewing a scientific paper on the matter I read a book titled 'Amazonian Dark Earths: origin, properties, and management' - I say read, I selected the chapters I thought would be relevant and read those, because it was a long book..
In this part of the world, the terra preta is called 'Amazonian dark earth'(ADE), or 'terra preta de índio'; which I prefer, it sounds much more exotic.
After much debate in the scientific world, there is now general consensus that ADE is anthropogenic, though whether it was created intentionally or not is still unknown as practices used to form them are not fully understood.
Most known sites are 500-2500 years old, though it is possible earlier sites have disappeared due to soil erosion, sea level rise, mineralization or other environmental factors, as the area has been inhabited for 11,000-10,000 years.
So this means, maybe the population began to rapidly expand 2500 years ago, or, this was the beginning of fully developed sedentary lifestyles. But unlike usual farming practices, it shows the same sites were used for at least 10 years rather than rotating crops every few years.
So what actually caused enrichment of the soil? There are several hypotheses:
So, the carbon sequestration part. Although obviously these people were blissfully unaware of global warming as we know it, their methods of soil improvement have stimulated a modern day innovation of creating biochar as a means of storing carbon.
Pollen analysis of ADE sites shows palms were important in formation; as were river grasses, shellfish shells and household refuse, which all led to primary or secondary sequestration in ADE. It has been calculated that 1 hectare of ADE stores 10Mg or C per year, creating a carbon reservoir of >200Mg C/ha within 25-50 years. Additionally, 14C dating of some soils indicates around 10cm accumulating per decade, which obviously works out as 1cm of this soil being formed per year. Which I think is pretty good considering tropical soils are reknowned for high erosion and depleted nutrients.
So in conclusion, it is clear that the pre-Columbian Amazonians deliberately created this soil, but as a way to improve their crops as opposed to storing carbon. Fire played a central role in the formation of the soil, and household waste was the key to creating such fertile land. In terms of using this ancient idea in the present day, there is the same problem as with afforestation - farmers are not likely to sacrafice their land in order to store carbon, unless there is some sort of reward available or profit to be made. It is estimated it will take 4-6 years before creating ADE will benefit the farmer, I guess it just depends if they are willing to wait this long to reap the benefits. Overall I think there is a lot of potential for this technique to be successful at reversing global warming.
Lehmann, J., D. Kern, B. Glaser and W. Woods(eds) (2003) Amazonian Dark Earths: Origin, Properties, Management, Amsterdam: Kluwer Academic Publishers.
However, this is not a new innovation - it turns out it's been used for thousands of years by the pre-Columbian Amazonians. So although it has a huge potential for present and future climate change mitigation, I'm going to investigate terra preta in a palaeo-geoengineering context.
Here's a little video which is quite good at explaining the concept, it focuses on Australia and features the first Australian agrichar farm:
But aside from that, instead of reviewing a scientific paper on the matter I read a book titled 'Amazonian Dark Earths: origin, properties, and management' - I say read, I selected the chapters I thought would be relevant and read those, because it was a long book..
In this part of the world, the terra preta is called 'Amazonian dark earth'(ADE), or 'terra preta de índio'; which I prefer, it sounds much more exotic.
After much debate in the scientific world, there is now general consensus that ADE is anthropogenic, though whether it was created intentionally or not is still unknown as practices used to form them are not fully understood.
Most known sites are 500-2500 years old, though it is possible earlier sites have disappeared due to soil erosion, sea level rise, mineralization or other environmental factors, as the area has been inhabited for 11,000-10,000 years.
So this means, maybe the population began to rapidly expand 2500 years ago, or, this was the beginning of fully developed sedentary lifestyles. But unlike usual farming practices, it shows the same sites were used for at least 10 years rather than rotating crops every few years.
So what actually caused enrichment of the soil? There are several hypotheses:
- A result of ashfall from the nearby Andes volcanoes
- From sedimentation in tertiary lakes or ponds
- Wind blowing in fertile soils from afar
- As a result of food preparation, cooking and cleaning
- From burning of 'discard areas', aka a large pre-Columbian dump.
So, the carbon sequestration part. Although obviously these people were blissfully unaware of global warming as we know it, their methods of soil improvement have stimulated a modern day innovation of creating biochar as a means of storing carbon.
Pollen analysis of ADE sites shows palms were important in formation; as were river grasses, shellfish shells and household refuse, which all led to primary or secondary sequestration in ADE. It has been calculated that 1 hectare of ADE stores 10Mg or C per year, creating a carbon reservoir of >200Mg C/ha within 25-50 years. Additionally, 14C dating of some soils indicates around 10cm accumulating per decade, which obviously works out as 1cm of this soil being formed per year. Which I think is pretty good considering tropical soils are reknowned for high erosion and depleted nutrients.
So in conclusion, it is clear that the pre-Columbian Amazonians deliberately created this soil, but as a way to improve their crops as opposed to storing carbon. Fire played a central role in the formation of the soil, and household waste was the key to creating such fertile land. In terms of using this ancient idea in the present day, there is the same problem as with afforestation - farmers are not likely to sacrafice their land in order to store carbon, unless there is some sort of reward available or profit to be made. It is estimated it will take 4-6 years before creating ADE will benefit the farmer, I guess it just depends if they are willing to wait this long to reap the benefits. Overall I think there is a lot of potential for this technique to be successful at reversing global warming.
Lehmann, J., D. Kern, B. Glaser and W. Woods(eds) (2003) Amazonian Dark Earths: Origin, Properties, Management, Amsterdam: Kluwer Academic Publishers.
Thursday, 24 November 2011
The cost of polluting
The Guardian today claims it costins the government €4-11bn a year in health and environmental damage because of air pollution from industrial practices! Wow. So what is the solution? Maybe place stricter policies on industrial emissions, or invest in technologies to scrub out the carbon before it enters the atmosphere, or, oh wait no, just tax it!
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