GB2477181A

GB2477181A - Marine based carbon sequestration device and methods

Info

Publication number: GB2477181A
Application number: GB1021258A
Authority: GB
Inventors: Robert John Huggins; Timothy William Fileman; Paul Lawrence Lonsdale; Julian Icarus Allen; Timothy James Smyth; Paul John Somerfield
Original assignee: PLYMOUTH MARINE LAB
Current assignee: PLYMOUTH MARINE LAB
Priority date: 2010-01-22
Filing date: 2010-12-14
Publication date: 2011-07-27
Also published as: GB201021258D0

Abstract

A marine-based carbon sequestration device1and method comprises means for emitting light in a stratified marine environment, at or below a pycnocline or at a deeper marine level. The device may comprise an energy transformer which converts light into electricity, a conduit3for transmitting the electricity from the transformer to a deeper marine level and means4for emitting light at the deeper level powered by the transmitted electricity thereby to provide a light zone for promoting organic growth such that, in use, the resulting organic material sinks to greater depths and becomes incorporated into the marine bed sediment.

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 info 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 * **...

* 20 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 *.S.

** photic zone with limiting rnicronutrients (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 phytoplankton growth occurs at or towards the surface of the water and a high proportion of the carbon dioxide is respired back into the atmosphere.

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 method of sequestering carbon into marine bed sediment comprising the steps of: emitting light in a stratified marine environment at or below a pycnocline to provide a submarine light zone for promoting organic growth such that resulting organic material sinks to greater depths and becomes incorporated into marine bed sediment.

According to a second aspect of the present invention there is provided a stratified marine environment based carbon sequestration device comprising: means for emitting light cit or below a pycnocline to provide a submarine light zone for promoting organic growth such that resulting organic material sinks to greater depths and becomes incorporated into marine bed sediment.

According to a third aspect of the present invention there is provided a marine-based carbon sequestration device comprising -an energy transformer for converting light into electricity; * U * * ** -an electrical conduit for transmitting electricity from the transformer ****..

* 20 to a deeper marine level; and means for emitting light at the deeper marine level powered by the transmitted ** S * electricity whereby to provide a light zone for promoting organic growth such that, in use, resulting organic material sinks to greater depths and becomes incorporated into marine bed sediment.

According to a fourth aspect of the present invention there is provided a method of sequestering carbon into marine bed sediment comprising the steps of: -providing an energy transformer for converting light into elecfricifY -providing an electrical conduit which transmits electricity from the transformer to a deeper marine level; and -providing means for emitting light at the deeper marine level powered by the transmitted electricity to provide a light zone for promoting organic growth such that resulting organic material sinks to greater depths and becomes incorporated into marine bed sediment.

The principle of these aspects of the present invention is therefore to use light to generate electricity and then to use electricity to provide light which promotes biomass production. When the biomass (for example, algae and phytoplankton) dies it sinks to the marine sediment as marine snow taking fixed carbon with it.

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 *..S enhancing production in the photic zone within reach of the surface where by being * *S...

* 20 consumed or metabolised the carbon may return to the atmosphere, by stimulating the S. S 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 *0* 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 phojic zone_and into a.phytoplankton bloomstimulated by-an-artificial tight zone: -it is noted that stratified marine environments are particularlY well suited to the present invention. Stratified environments include a pycnoclifle which is a thin but distinct layer in a large body of water, such as an ocean, sea or lake. in which the density changes more rapidly with depth than it does in the layers above or below. The pycnoclifle may be thought of as an invisible blanket or barrier which separates an upper mixed layer from a calm deep layer below. Depending argely on season, latitude and turbulent mixing by wind, pycnoClines may be a permanent or semipermanent feature of the body of water in which they occur, or they may form tempOrOrY in response to phenomena such as the radiative heating/Cooing of surface water during the day/night. FaclorS that affect the depth and thickness of a pycnoclifle include seasonal weather variations, latitude and local environmental conditionS, such as tides and currents.

Turbulent mixing produced by winds and waves transfers heat downwards from the surface. n low and mid-latitudes, this creates a surface mixed layer of water of almost uniform temperature which may be a few metres deep to several hundred metres deep. Below this mixed layer, at depths of 200 to 300m in the open ocean, the temperature begins to decrease rapidly down at about 1OOOm. The water layer within * * * 20 whiCh the temperature gradient is steepest is known CS the permanent thermocline.

The temperature ditterenCe through this layer may be as large as 20°C. The permanent * * * thermoCUne coincides with a change in water density between the warmer lowdensitY surface waters and the underlying cold dense bottom waters. The region of rapid S..

*..: density change is known as the pycnocline. and it acts as a barrier to vertical water circulation; thus it also affects the vertical distribution of certain chemicals which play a role in the biology of the seas.

A pycnocline is a dine caused by a strong vertical density gradient within a body of _____ water In freshwater environments such as lakes this density change is primarily caused by water temperature (the thermocline), while in seawater environments such as oceans and estuaries, the rapid density change in the water column is often caused by a combination of decreasing water temperature (thermocline) and increasing salinity (halocline).

Areas where freshwater and saltwater environments meet, such as bays and near river mouths, often have strong, well defined pycnoclines. A large amount of run off from land of warmer freshwater can float upon colder saltwater entering an estuary forming a salt wedge. The amount of mixing from top to bottom will determine the stratification or strength of the pycnocline. With little mixing from the friction of currents the density differences between the fresh and salt water dominate.

Pycnoclines tend to disappear in the open ocean at around 50 or 60 degrees North or South latitude. This is due to lowered salinity and temperature change near the poles.

Clines, for example pycnoclines, are a barrier to mixing between the upper mixed layer and the calm deep layer and thus primary production stimulated below a pycnocline and/or thermocline is more likely to lead to organic material which sinks and becomes *S..

incorporated into sea sediment.

***... * 20

It is considered that the range +1-30° latitude represents a good area for stable S. ***S * thermoclines and pycnoclines. Temperate oceans display more seasonal stratification and may be useful for different applications of the present invention. S. * * . *5

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

The depth of thermoclines and pycnoclines often coincide, but not always.

Thermoclines and pycnoclines 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 pycnocline and/or a thermocline, for example at up to lOOm below a pycnocline and/or thermocline.

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

The device or method may be adapted for use in a stratified marine environment.

Accordingly the means for emitting light may be adapted to provide the light zone at or below a pycnocline and/or a thermocline (for example up to 1 OOm below).

According to a fifth aspect of the present invention there is provided a stratified marine environment-based carbon sequestration device comprising an energy transformer for converting light into electricity an electrical conduit for transmitting electricity from the transformer to a deeper marine level at or below a pycnocline and means for emitting **.* light at the deeper marine level powered by the transmitted electricity whereby to * 20 provide a below-pycnocline light zone for promoting organic growth such that, in use, ** * resulting organic material sinks to greater depths and becomes incorporated into marine bed sediment. * * S..,

According to a sixth aspect of the present invention there is provided a method of sequestering carbon into marine bed sediment comprising the steps of providing an energy transformer for converting light into electricity, providing an electrical conduit which transmits electricity from the transformer to a deeper marine level at or below a pycnocline and providing means for emitting light at the deeper marine level powered -by thetransmitted electricity to provide a-belowpycnocline light zone for promoting -organic growth such that resulting organic material sinks to greater depths and becomes incorporated into marine bed sediment.

According to a seventh aspect of the present invention there is provided a method of sequestering carbon into marine bed sediment comprising the steps of: -converting natural light into electricity; -transmitting the electricity to a deeper marine level at or below a pycnocline; and -emitting light at the deeper marine level powered by the transmitted electricity to provide a below-pycnocline light zone for promoting organic growth such that resulting organic material sinks to greater depths and becomes incorporated into marine bed sediment.

In comparison with other liquids water is relatively transparent to solar radiation, but much less so than air. Of the sunlight penetrating the sea surface, about 50% is composed of wavelengths longer than about 780nm. This infrared radiation is quickly absorbed and converted to heat in the upper few metres. Ultraviolet radiation (<380nm) forms only a small fraction of the total radiation, and it also is usually rapidly * S scattered and absorbed except in the very clearest ocean waters. The remaining 50% a....

* 20 of the radiation comprises the visible spectrum, with wavelengths of between

I

.: approximately 400 and 700nm that penetrate deeper in the sea. These are of

I

* . particular importance for animals with vision and because they are also approximately the same wavelengths used by plants in photosynthesis. These wavelengths are often SI1 referred to as photosynthetically active radiation (PAR).

The means for emitting light may comprise one or more LEDs for example, an array of LEDs. LED5 are particularly useful because they can be used to emit light at particular wavelengths. The light frequency emitted may be variable.

The means for emitting light may be adapted to emit light having a frequency in the range of 400 to 700nni.

The device may further comprise energy storage means. This could allow power to be provided in the absence of sunlight to give continuous light emission.

The energy transformer may comprise one or more photo voltaic cells.

The electrical conduit may comprise one or more wires, cables or the like.

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. **sS

Blue light may be preferred for some applications and the filtering means may provide * 20 light wavelengths selected from the range 400 to 550nm for emission. * * S * *3

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

Ultraviolet light may also be removed. a... a. * * .5 * ,

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

The depth of emission may be varied in response to changes in temperature, light --1ntnsity 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 transformer may be positioned above, at or in the vicinity of the water surface. This may necessitate some means of preventing accumulation of sea salt spray, such as a cover or canopy.

The transformer 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.

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.

* * 20 **S.

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. * *IS.

*. * 25 * _. * * ** V 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.

------

The principle of below-pycnocline light emission could be applied to other aspects of the present invention. For example, rather than electric energy transmission, light could be channelled directly in a light conduit from a light collector for emission.

According to an eighth aspect of the present invention there is provided 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 pycnocline; and -means for emitting light from the conduit at the deeper marine level whereby to provide a below-pycnocline light zone for promoting organic growth such that, in use, resulting organic material sinks to greater depths and becomes incorporated into marine bed sediment.

According to a ninth aspect of the present invention there is provided a method of sequestering carbon into marine bed sediment comprising the steps of: providing a light collector; providing a light conduit which transfers light from the collector to a deeper * 20 marine level at or below a pycnocline; and providing means for emitting light from the conduit at the deeper marine level to provide a below-pycnocline light zone for promoting organic growth such that resulting organic material sinks to greater depths and becomes incorporated into marine bed sediment. * * **..

*. * 25 * * . * .1 According to a tenth aspect of the present invention there is provided 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 pycnoclifle and -emitting the light at the deeper marine level to provide a below-pycnocline light zone for promoting organic growth such that resulting organic material sinks to greater depths and becomes incorporated into marine bed sediment.

The present invention will now be more particularly described, by way of example, with reference to the ccompaflying drawings, in whicft 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 an aspect of the present invention; Figure 3 is a schematic representation of a sequestration device formed according to an alternative embodiment of an aspect of the present invention; Figure 4 is a schematic representation of a sequestration device formed according to an alternative embodiment of an aspect of the present invention; and Figure 5 is a schematic representation of a sequestration device formed according to an alternative aspect of the present invention.

* * 20 Referring first to Figure 1 there is shown a marine environment, in this case an oceanic regions generally indicated 0. The region 10 includes a pycnocline 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 pycnocline 20. * * **

*. * 25 * * S On the left hand side of the Figure the natural state of the region 10 is illustrated, with * S. 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 charaCteriSed 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 solar panel 60 is provided for collecting solar light, transferring it to electrical energy and transmitting it down an electrical conduit 70 which transmits electricity through the mixed layer 30 and below the pycnocline 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 pycnocline 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.

Refenlng now to Figure 2 there is shown a carbon sequestration device generally . 20 indicated 1. The device 1 comprises a floating light harvester 2 which receives sunlight *$S.

and channels electricity into a conduit 3. The conduit 3 comprises electrical wire or cable which transmits the electricity to a LED array 4 which then emits the light to promote a phytoplankton bloom 5. S.,. * S **.

Referring now to Figure 3 there is shown a carbon sequestration device 101 formed S S* according to an alternative embodiment. The device 101 is very similar to the device 1 shown in Figure 2 except that instead of a single wire, the conduit 103 comprises a plurality of cables which are protected by a sheath 1 03a along their length.

The harvester 102 has an associated battery 102a which can selectively store energy and transmit it down the cable 103, for example at night or in low light conditions to provide continuOus power to an LED array 204.

Reterflg now to Figure 4 there is shown ci 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 LED array 204 can be lowered or raised to alter the depth of the light zone. The conduit 203 is composed of a plurality of flexible electric 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 pycnocline 220. If the position of the pycnocline changes the diffuser 204 is raised or lowered accordingly.

Eor 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 flOW to Figure 5 there is shown a carbon sequestration device 301 formed according to an embodiment of an alternative aspect. The device 301 compSeS a floating light collector 307 which receives sunlight and channels it into a light conduit 308. The conduit comprises a fibre optic cable which transmits the light to a diffuser * positioned below the pycnoclifle 320 which emits light to promote a phytoplaflktofl bloom 305. * *1 * ** * * * * * S.. * S..

*. * 25

S S *

Claims

CLAIMS1. A method of sequestering carbon into marine bed sediment comprising the steps of: -emitting light in a stratified marine environment at or below a pycnocline to provide a submarine light zone for promoting organic growth such that resulting organic material sinks to greater depths and becomes incorporated into marine bed sediment.

2. A stratified marine environment based carbon sequestration device comprising: means for emitting light at or below a pycnocline to provide a submarine light zone for promoting organic growth such that resulting organic material sinks to greater depths and becomes incorporated into marine bed sediment.

3. A marine-based carbon sequestration device comprising: -an energy transformer for converting light into electricity; -an electrical conduit for transmitting electricity from the transformer to a deeper marine level; and -means for emitting light at the deeper marine level powered by the **..transmitted electricity whereby to provide a light zone for promoting organic growth such that, in use, resulting organic material sinks to : greater depths and becomes incorporated into marine bed * . sediment. **S. * * S... S*

4. A method of sequestering carbon into marine bed sediment comprising the steps of: providing an energy transformer for converting light into electricity; providing an electrical conduit which transmits electricity from the transformer to a deeper marine level; and providing means for emitting light at the deeper marine level powered by the transmitted electricity to provide a light zone for promoting organic growth such that resulting organic material sinks to greater depths and becomes incorporated into marine bed sediment.

5. A device or method according to Claim 3 or Claim 4, in which the device or method is adapted for use in a stratified marine environment.

6. A device or method as claimed in any of Claims 3 to 5, in which the means for emitting light is adapted to provide the light zone at or below a pycnocline and/or a thermocline.

7. 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 1 OOm below a pycnocline and/or a thermocline.

8. 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 200m below the water surface. * * . * **

9. A stratified marine environment-based carbon sequestration device comprising: * S **S.-an energy transformer for converting light into electricity; * S * * S. -an electrical conduit for transmitting electricity from the transformer to a deeper marine level at or below a pycnocline; and -means for emitting light at the deeper marine level powered by the ---------transrnitted electricity--whereby to provide a below-pycnocIine zone for promoting organic growth such that, in use, resulting organic material sinks to greater depths and becomes incorporated into marine bed sediment.

10. A method of sequestering carbon into marine bed sediment comprising the steps of: providing an energy transformer for converting light into electricity; providing an electrical conduit which transmits electricity from the transformer to a deeper marine level at or below a pycnoctine and providing means for emitting light at the deeper marine level powered by the transmitted electricity to provide a below.IDYCnOCIIfle light zone for promoting organic growth such that resulting organic material sinks to greater depths and becomes incorporated into marine bed sediment.

1 L A method of sequestering carbon into marine bed sediment comprising the steps of: -converting natural light into electdcity -transmitting the electricity to a deeper marine level at or below a pycnocline and -emitting light at the deeper marine level powered by the transmitted electricity to provide a belowPYCnOClifle light zone for promoting organic growth such that resulting organic material sinks to greater depths and becomes incorporated into marine bed sediment. * 0 *0S* 0 a * ***

12. A device or method according to any preceding claim, in which the means for emitting light comprises one or more LED5.

13. A device or method according to any preceding claim, in which the means ________________ ______ for emitting light comprises an array of LEDS.

14. A device or method according to any preceding claim, in which the means for emitting light is adapted to emit light having a frequency in the range of 400 to 700nm.

15. A device or method according to any preceding claim, further comprising energy storage means.

16. A device or method according to any preceding claim, in which the energy transformer comprises one or more photo voltaic cells.

17. A device or method according to any preceding claim, in which the electrical conduit comprises one or more wires.

18. A device or method as claimed in any preceding claim, further comprising light filtering means.

19. A device or method as claimed in Claim 18, in which the filtering means provides light wavelengths selected from the range 400 to 700nm for emission. *S*s * *.. * *

* 20. A device or method as claimed in Claim 18 or Claim 19, in which the filtering * S * * ** *....: means removes ultraviolet light prior to emission. * S *S*. * U **..

* 25 21. A device or method as claimed in any preceding claim, in which the depth * * * * *5 of light emission is variable.

22. A device or method as claimed in Claim 21, in which the depth of light -emission is varied-in-response--to-changesin temperature. --/ 23. A device or method as claimed in any preceding claim, in which the transformer is positioned at or in the vicinity of the water surface.24. A device or method as claimed in any preceding claim, in which the transformer comprises or forms part of a buoy.25. A device or method as according to any preceding claim, comprising a floating platform.26. A device or method according to any preceding claim, in which the means for emitting light comprise a point source.27. A device or method as claimed in any of Claims 1 to 25, in which the means for emitting light comprises a diffuser.28. A device or method as claimed in any preceding claim, in which the device or method apparatus comprises anti-blot ouling means.29. A device substantially as hereinbefore described with reference to, and as **..shown in, the accompanying drawings. * * ***.. 30. A method substantially as hereinbefore described with reference to, and as * S e, shown in, the accompanying drawings.*. * 25 S * * * **