GB2462865A

GB2462865A - Marine based carbon sequestration device

Info

Publication number: GB2462865A
Application number: GB0816859A
Authority: GB
Inventors: Julian Icarus Allen; Paul John Somerfield; Timothy James Smyth
Original assignee: PLYMOUTH MARINE LAB
Current assignee: PLYMOUTH MARINE LAB
Priority date: 2008-09-15
Filing date: 2008-09-15
Publication date: 2010-02-24
Anticipated expiration: 2028-09-15
Also published as: GB2467845A; GB0816859D0; WO2010029285A3; WO2010029285A2; GB2462865B; GB2467845B; GB201002474D0

Abstract

A marine-based carbon sequestration device 1 and method comprising a light collector 2, a light conduit 3 for transferring light from the collector to a deeper marine level and means for emitting light from the conduit at a deeper marine level whereby to provide a light zone (80, fig 1) for promoting organic growth. In use, resulting organic material sinks to greater depths and becomes incorporated into seabed sediment. The light collector may be positioned in the vicinity of the water surface. The light conduit may comprise one or more light pipes, optical fibres or a plastic block. An alternative device utilizing an energy source such as a solar cell array, energy conduit and means for emitting light at a deeper marine level powered by the energy source is also claimed (fig 5).

Description

Improvements in or Relating to Carbon Sequestration The present invention relates generally to improvements in or relating to carbon sequestration and particularly to a marine-based carbon sequestration device and a marine-based method of carbon sequestration.

Increasing levels of the greenhouse gas, carbon dioxide, are a major cause of climate change on Earth. There is therefore an urgent need to find innovative and novel methods for increased carbon sequestration. This involves taking carbon dioxide from the atmosphere or the ocean and incorporating the carbon into materials into which it will be securely bound for many years.

Plants remove carbon dioxide from the atmosphere and/or the oceans through photosynthesis, which is the basis of their life and growth. This form of carbon sequestration is very important but is in general relatively short-lived. For example, the woody material of trees may exist for one hundred years but then the material rots and releases carbon dioxide back into the atmosphere. In the oceans, sequestration through phytoplankton production is limited by the availability of nutrients and by the continuous recycling of organic material in the mixed layer of the photic zone at or close to the water surface.

Various marine-based solutions have previously been proposed, including the pumping of nutrient rich water from the deep ocean up to the photic zone, or fertilising the phofic zone with limiting micronutrients (such as iron). In both cases the intention is to stimulate the growth of phytoplankton and in doing so to increase the uptake of carbon dioxide for sequestration. However, the increased phyfoplankton growth occurs at or towards the surface of the water and a high proportion of the carbon dioxide is respired back into the atmosphere.

S The present invention seeks to address the problems with known carbon sequestration techniques.

According to a first aspect of the present invention there is provided a marine-based carbon sequestration device comprising: a light collector; a light conduit for transferring light from the collector to a deeper marine level; and means for emitting light from the conduit at the deeper marine level whereby to provide a light zone for promoting organic growth.

The present invention is based on the concept that in order to provide an environmental benefit not only must primary production be promoted, but the results of the production must lead to long-term sequestration. Production can be increased by providing something which is limiting, and the present invention provides a light zone away from the photic zone of a marine environment where a naturally nutrient rich environment can support increased primary production. Furthermore, rather than enhancing production in the photic zone within reach of the surface where by being consumed or metabolised the carbon may return to the atmosphere, by stimulating the production in the deep sea a large proportion of the resulting organic material will sink to greater depths. The organic material will then be incorporated into deep seabed sediments and remain sequestered for thousands if not millions of years. The recycling time may be on a geological scale, for example with the seabed being subducted into volcanoes.

The intention of the present invention is therefore to create a sink in deep marine environments which will draw carbon dioxide down from the atmosphere through the photic zone and into a phytoplankton bloom stimulated by an artificial light zone.

S The device may further comprise light filtering means. The present invention encompasses both unfiltered and filtered light. However, filtered light may provide certain advantages.

The approximate absorbance maxima of green chlorophyll are 430nm and 662nm and therefore light in the region of these values may be filtered for emission to promote photosynthesis.

Blue light may be preferred for some applications and the filtering means may provide light wavelengths selected from the range 400 to 550nm for emission.

The filtering means may remove red light to stop localised warming of the water.

Ultraviolet light may also be removed.

The point of filtration could be anywhere in the device, such as the point of collection or emission. Indeed the light conduit itself may comprise the light filtering means. For example, certain types of conduit may filter the light as it passes from the collector to the light zone.

The depth of emission may be variable. This could be particularly useful lithe optimum depth for a light zone is not constant.

The depth of emission may be varied in response to changes in temperature, light intensity or pressure. In some embodiments an array of temperature sensors are provided on the device and a feedback loop is used to adjust the emission depth to optimise production and sequestration.

The collector may have a generally parabolic shape. For example a parabolic mirrored surface may be used to reflect light into the light conduit.

The collector may be positioned above, at or in the vicinity of the waler surface. This may necessitate some means of preventing accumulation of sea salt spray, such as a cover or canopy.

The collector may comprise or form part of a buoy. A floating device would be simple to install and could be tethered or untethered.

The means for emitting light may comprise a point source, or may comprise a diffuser.

This may be dependant on the type of organic growth which is to be promoted.

The light conduit may form at least part of the light emission means. In some embodiments a plurality of flexible light pipes are allowed to float freely to form a spread of light emitters.

The light conduit may use a total infernal reflection process to transfer the light. For example the light conduit may comprise one or more light pipes, such as optical fibres.

It is feasible to use recycled optical fibres to form a conduit.

The light conduit may comprise a Perspex (RIM) block, such as a rod or cylinder.

Biofouling is the undesirable accumulation of microorganisms, plants, algae, and animals on submerged structures. The device may comprise anti-biofouling means.

This could be particularly relevant for the emission means to prevent intensity reduction or loss of the light zone. Various coatings are known (such as copper and copper-based compounds) which could be used, or a regular cleaning programme could be established.

It is noted that stratified marine environments may be particularly well suited to the present invention. Stratified environments include a thermocline. which is a thin but S distinct layer in a large body of water, such as an ocean, sea or lake, in which the temperature changes more rapidly with depth than it does in the layers above or below. The fhermocline may be thought of as an invisible blanket or barrier which separates an upper mixed layer from a calm deep layer below. Depending largely on season, latitude and turbulent mixing by wind, thermoclines may be a permanent or semi-permanent feature of the body of wafer in which they occur, or they may form temporarily in response to phenomena such as the radiative heating/cooling of surface water during the day/night. Factors that affect the depth and thickness of a thermocline include seasonal weather variations, latitude and local environmental conditions, such as tides and currents.

Thermoclines are a barrier to mixing between the upper mixed layer and the calm deep layer and thus primary production stimulated below a thermocline is more likely to lead to organic material which sinks and becomes incorporated into sea sediment.

It is considered that the range +/-30° latitude represents a good area for stable fhermoclines. Temperate oceans display more seasonal stratification and may be useful for different applications of the present invention.

The means for emitting light may be adapted to provide the light zone at between 50 to 200m below the water surface.

Thermoclines often form at around 100 to 150m below the surface. The means for emitting light may be adapted to provide the light zone at or below a thermocline, for example at up to 1 OOm below a thermocline.

The deep chlorophyll maximum (DCM) is a sub-surface maximum in the concentration of chlorophyll in the ocean or other bodies of wafer. The means for emitting light may be adapted to provide the light zone in the region of the DCM.

Although it may not be possible in all circumstances, a device with no moving parts is considered to be particularly advantageous because of the reduction in potential for breakdown and damage, and because of the removal or reduction of maintenance required.

An array or flotilla of devices may be deployed effectively to create an enlarged light zone. This reduces the chances of ocean currents moving phytoplankton away from the light zone.

According to a second aspect of the present invention there is provided a marine-based method of carbon sequestration, comprising the steps of: providing a light collector; providing a light conduit for transferring light from the collector to a deeper marine level; and providing means for emitting light from the conduit at the deeper marine level whereby to provide a light zone for promoting organic growth.

According to a third aspect of the present invention there is provided a marine based carbon sequestration device comprising: an energy source; an energy conduit for transferring energy from the source to a deeper marine level; and means for emitting light from the conduit at the deeper marine level powered by the energy source whereby to provide a light zone for promoting organic growth.

The present invention will now be more particularly described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic overview of the sequestration method of the present invention; Figure 2 is a schematic representation of a sequestration device formed according to a first aspect of the present invention; Figure 3 is a schematic representation of a sequestration device formed according to an alternative embodiment of the first aspect of the present invention; Figure 4 is a schematic representation of a sequestration device formed according to a further embodiment of the first aspect of the present invention; and Figure 5 is a schematic representation of a sequestration device formed according to a third aspect of the present invention.

Referring first to Figure 1 there is shown a marine environment, in this case an oceanic region, generally indicated 10. The region 10 includes a Ihermocline 20 which separates the region into a mixed layer 30 and a below mixed layer 40. A deep chlorophyll maximum region 50 is present in the region of the thermocline 20.

On the left hand side of the Figure the natural state of the region 10 is illustrated, with the mixed layer 30 characterised by a photic zone with high light levels, low nutrients and low primary production; and the below mixed layer 40 characferised by low or no light, high nutrients and no or low primary production. The result is that carbon export from the below mixed layer to the seabed is low.

On the right hand side of the Figure some of the principles of the present invention are illustrated, A light catcher 60 is provided for collecting solar light and reflecting it into a light conduit 70 which transports captured light through the mixed layer 30 and below the thermocline 20 whereupon it is emitted to form a light zone 80 resulting in increased primary production and consequential increase in carbon export to the sea bed. The thermocline acts as a barrier to prevent exchange of material back into the mixed layer and accordingly carbon dioxide passes from the atmosphere into the mixed layer, through the thermocline and is used in the primary production in the light zone 80 so that the light zone 80 effectively becomes a carbon sink.

The organic material in the bloom 50 will die or be respired. A large proportion of the material may fall directly to the ocean bed whilst some may be recycled but also eventually sequestered into deep ocean sediment.

Referring now to Figure 2 there is shown a carbon sequestration device generally indicated 1. The device 1 comprises a floating light collector 2 which receives sunlight and channels it into a light conduit 3. The conduit 3 comprises a fibre optic cable which transmits the light by total internal reflection to a diffuser 4 which then emits the light to promote a phytoplankton bloom 5.

Referring now to Figure 3 there is shown a carbon sequestration device 101 formed according to an alternative embodiment. The device 101 is very similar to the device I shown in Figure 2 except that instead of a single light pipe, the light conduit 103 comprises a plurality of fibre optic cables which are protected and constrained by a sheath 103a along their length until they reach the required light zone at which point they are no longer constrained and thus fan out to create a light emitting array.

Referring now to Figure 4 there is shown a sequestration device 201 formed according to an alternative embodiment. The device 201 is very similar to the device 1 shown in Figure 2 except that in this embodiment the diffuser 204 can be lowered or raised to alter the depth of the light zone. The light conduit 203 is composed of a plurality of flexible fibre optic cables and is provided with a plurality of temperature sensors 206 along its length. In this embodiment the system is configured to position the light diffuser a set distance below the thermocline 220 and accordingly the sensors 206 are used to determine the current position of the diffuser 204 with respect to the therrnocline 220. If the position of the thermocline changes the diffuser 204 is raised or lowered accordingly. For this purpose the cables of the light conduit 203 are held on a rotatable drum which can be wound or unwound to alter the position of the diffuser 204.

Referring now to Figure 5 there is shown a carbon sequestration device 301 formed according to an embodiment of an alternafive aspect. In this embodiment the sunlight is not collected and transferred but rather is used as a power source harvested by a solar cell array 307. Power from the array 307 is transmitted via an electrical conduit 308 to a light source 309 which provides the light zone for Ihe phytoplankton bloom 305.

The same principles apply for this embodiment as for the embodiments shown in Figures I to 4 in that the intention is for primary production to be enhanced at or below the Ihermocline 320 so that there is high carbon export to the sea bed.

Claims

CLAIMS1. A marine-based carbon sequestration device comprising: -a light collector; -a light conduit for transferring light from the collector to a deeper marine level; and -means for emitting light from the conduit at the deeper marine level whereby to provide a light zone for promoting organic growth.
2. A device as claimed in Claim 1, further comprising light filtering means.
3. A device as claimed in Claim 2, in which the filfering means provides light wavelengths selected from the range 400 to 550nm for emission.
4. A device as claimed in Claim 2, in which the filtering means removes ultraviolet light prior to emission.
5. A device as claimed in any of claims 2 to 4, in which the light conduit comprises the light filtering means.
6. A device as claimed in any preceding claim, in which the depth of emission is variable.
7. A device as claimed in Claim 6, in which the depth of emission is varied in response to changes in temperature.
8. A device as claimed in any preceding claim, in which the collector has a generally parabolic shape.
9. A device as claimed in any preceding claim, in which the collector is positioned at or in the vicinity of the water surface.
10. A device as claimed in any preceding claim, in which the collector comprises or forms part of a buoy.
11. A device as claimed in any preceding claim, in which the means for emitting light comprise a point source.
12. A device as claimed in any of Claims 1 to 10, in which the means for emitting light comprise a diffuser.
13. A device as claimed in any preceding claim, in which the light conduit forms at least part of the light emission means.
14. A device as claimed in any preceding claim, in which the light conduit uses total internal reflection to transfer the light.
15. A device as claimed in any preceding claim, in which the light conduit comprises one or more light pipes.
16. A device as claimed in any preceding claim, in which the light conduit comprises one or more optical fibres.
17. A device according to any of claims 1 to 14, in which the light conduit comprises a Perspex block.
18. A device as claimed in any preceding claim, in which the device comprises anti-biofouling means.
19. A device as claimed in any preceding claim, in which the means for emitting light is adapted to provide the light zone at between 100 to 200m below the water surface.
20. A device as claimed in any preceding claim, in which the means for emitting light is adapted to provide the light zone at or below a thermocline.
21. A device as claimed in any preceding claim, in which the means for emitting light is adapted to provide the light zone at up to lOOm below a thermocline.
22. A marine-based method of carbon sequestration, comprising the steps of: -providing a light collector; -providing a light conduit for transferring light from the collector to a deeper marine level; and -providing means for emitting light from the conduit at the deeper marine level whereby to provide a light zone for promoting organic growth.
23. A marine based carbon sequestration device comprising: -an energy source -an energy conduit for transferring energy from the source to a deeper marine level; and -means for emitting light from the conduit at the deeper marine level powered by the energy source whereby to provide a light zone for promoting organic growth.
24. A marine-based carbon sequestration device substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.
25. A marine-based method of sequestration device substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.Amendments to the Claims have been filed as follows:CLAIMSL A stratified marine environment-based carbon sequestration device comprising: -a light collector; -a light conduit for transferring light from the collector to a deeper marine level at or below a thermocline; and -means for emitting light from the conduit at the deeper marine level whereby to provide a below-thermocline light zone for promoting organic growth such that, in use, resulting organic material sinks to greater depths and becomes incorporated into marine bed * S.. * Ssediment.S *...* * S2. A method of sequestering carbon into marine bed sediment comprising the stepsof: providing a light collector; *...: providing a light conduit which transfers light from the collector to a deeper * S marine level at or below a thermocline; and providing means for emitting light from the conduit at the deeper marine level to provide a below-thermocline light zone for promoting organic growth such that resulting organic material sinks to greater depths and becomes incorporated into marine bed sediment.3. A method of sequestering carbon into marine bed sediment comprising the steps of: -collecting light; -transferring the light to a deeper marine level at or below a thermocline; and -emitting the light at the deeper marine level to provide a below-thermocline light zone for promoting organic growth such that resulting organic material sinks to greater depths and becomes incorporated into marine bed sediment.4. A device or method as claimed in any preceding claim, in which the means for emitting light is adapted to provide the light zone at up to lOOm below a thermocline.5. A device or method as claimed in any preceding claim, in which the means for emitting light is adapted to provide the light zone at between 100 to 20Dm below the water surface. e * *6. A device or method as claimed in any preceding claim, further comprising light filtering means. *. ** * * * * *7. A device or method as claimed in Claim 6, in which the filtering means provides light wavelengths selected from the range 400 to 550nm for emission.8. A device or method as claimed in Claim 6 or Claim 7, in which the filtering means removes ultraviolet light prior to emission.9. A device or method as claimed in any of claims 6 to 8, in which the light conduit comprises the light filtering means.10. A device or method as claimed in any preceding claim, in which the depth of emission is variable.11. A device or method as claimed in Claim 10, in which the depth of emission is varied in response to changes in temperature.12. A device or method as claimed in any preceding claim, in which the collector has a generally parabolic shape.13. A device or method as claimed in any preceding claim, in which the collector is positioned at or in the vicinity of the water surface.14. A device or method as claimed in any preceding claim, in which the collector comprises or forms part of a buoy. * S.. * . S...* S 15. A device or method as claimed in any preceding claim, in which the means for emitting light comprise a point source. *.*16. A device or method as claimed in any of Claims ito 14, in which the means for emitting light comprise a diffuser.17. A device or method as claimed in any preceding claim, in which the light conduit forms at least part of the light emission means.18. A device or method as claimed in any preceding claim, in which the light conduit uses total internal reflection to transfer the light.19. A device or method as claimed in any preceding claim, in which the light conduit comprises one or more light pipes.20. A device or method as claimed in any preceding claim, in which the light conduit comprises one or more optical fibres.21. A device or method according to any of claims ito 19, in which the light conduit comprises a Perspex (RIM) block.22. A device or method as claimed in any preceding claim, in which the device or method apparatus comprises anti-biofouling means.23. A stratified marine environment-based carbon sequestration device substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.24. A method of sequestering carbon substantially as hereinbetore described * * with reference to, and as shown in, the accompanying drawings.**S*.. * * ** 15 S. ** * . S * SS..... S *