GB2425702A

GB2425702A - Photosynthetic apparatus and method using algae

Info

Publication number: GB2425702A
Application number: GB0509011A
Authority: GB
Inventors: Guillaume Stewart-Jones
Original assignee: QUESTOR Ltd C
Current assignee: QUESTOR Ltd C
Priority date: 2005-05-04
Filing date: 2005-05-04
Publication date: 2006-11-08
Also published as: GB0509011D0

Abstract

The apparatus comprises a series of platforms made from a plastic base, covered with a thin, clear plastic film, the base and film being spaced apart by flexible connecting spacers. In use the apparatus is filed with water containing an algal seed culture, nutrients and dissolved carbon dioxide. The algae capture the carbon dioxide by photosynthesis and can be harvested at various points in the system. Oxygen produced during the process can be released through collection valves located at elevated positions through the system.

Description

Contained Flow High-Density Aqueous Photosynthetic Platforms

DESCRIPTION

Background

There are several technologies currently being developed for harvesting carbon dioxide from industrial and domestic sources. However only a small number of tenninal disposal technologies for the collected gas are currently available.

With the advent of a worldwide global carbon "trading" systems, methods of capturing and storing carbon dioxide are of increasing interest to both industry and government, it is therefore reasonable to forecast that technologies designed to counter the global flux of carbon dioxide emissions will become of increasing commercial value. Indeed, it is foreseeable that some governments may decide to mandate such mechanisms as integral components of numerous emission sources.

Several billions of years ago, in the pre-biotic era, the earth's atmosphere contained virtually no oxygen and was hugely enriched in carbon dioxide. This ratio was reversed by the process of photosynthesis to the point where, today 21% of the earth's atmosphere is oxygen, and 0. 05% is carbon dioxide; an almost complete polar reversal of the pre- hiotic situation. Just about all of the oxygen present in the earth's atmosphere today has been generated by photosynthesis. This demonstrates the earth's proven capacity for the effective sequestration and conversion of carbon dioxide by the photosynthetic process on a massive scale.

Unfortunately, the historic rate of conversion is no longer able to keep pace with mankind's rising production of carbon dioxide and this has lead to "global warming" due to the "greenhouse effect".

Current problem No other current man-made mechanism has been identified or developed that can absorb carbon dioxide on the scale that natural photosynthesis has managed over the millennia.

With an increasing percentage of carbon dioxide in the atmosphere, it is only logical to find a way to supplement the natural photosynthetic process and exploit it in order to counteract the continually escalating problem of increasing global carbon dioxide emissions.

Essential features of the Contained Flow High-Density Aqueous Photosynthetic Platforms The technology proposed here involves a mechanism that will efficiently harness nature's photosynthetic power in order to convert substantial quantities of carbon dioxide into algal or cyannobacterial biomass which will release gaseous oxygen within a contained photosynthetic platform.

The principle components affecting photosynthesis are: 1) light intensity 2) temperature and 3) carbon dioxide concentration 4) chlorophyll 5) plant nutrient substrate Optimising all these parameters will enable a considerably greater net photosynthetic turnover that will allow an unsurpassed carbon dioxide capture capability per km2 surface area compared to conventional plant cultivation.

To optimise the light parameter, deserts would be most suitable as a venue fbr the development of the invention as cloud cover is minimised and light intensity is maximised. Additionally, deserts are largely barren, uninhabited areas that are unsuitable for agricultural or urban development, where the human population is low and thus there is minimum ecological disturbance by such positioning.

The structure of the contained flow high-density aqueous photosynthetic platforms consist of a sturdy plastic base that is highly impregnable to sharp edges or points and which is superimposed by a clear plastic film with flexible connecting spacers of plastic material that allow the inflation of the platform with a 20cm layer of water (either sea, freshwater or high salinity non potable water) when filled. The spacers are positioned at a suitable distance from each other to ensure the distance between the base and upper plastic layers remain broadly at a constant 20cm separation across the surface area covered. These platforms may be manufactured as roll-out' devices that can be transported to the site, opened out and filled with water.

The surface areas of these devices can vary from small surface areas of I 00m2 to interconnected platforms covering thousands of square kilometres and can also be arranged in various shapes and patterns to suit the contours of the positioning location.

The contents of the platforms would be a nutrient-optimised solution of minerals, ions and other growth stimulants for the fastest growth and photosynthetic flux of the organisms under the conditions of growth. The algal or cyannohacterial organisms contained within the platforms would be selected for their compatibility with the growth environment, and their photosynthetic capability. The system ideally lends itself to cyannobacterial and algal species from marine or freshwater sources for the source of chlorophyll for the bio-conversion of the carbon dioxide to oxygen.

Ideally single-celled photosynthetic organisms that readily remain in suspension during the continuous flow and circulation of the aquatic bed are utilised. The density of the organisms (numbers of cells per unit volume) would be adjusted at the outset during the injection stage to optimise the photosynthetic capture of carbon dioxide throughout the passage of the fluid across a stretch of platform. This may, at some points, involve overcoming the problem of cellular density within the lumen of the platform to avoid light penetrating the topside of the device being entirely absorbed by the photosynthetic biomass, with little luminosity reaching the bottom-side of the device. This problem is best resolved by ensuring movement of the biomass.

The bottom-side of the device can be coloured white or metallic silver, so as to reflect most of the light that reaches the bottom of the device back through the photosynthetic suspension, thus enhancing net light intensity within the photosynthetic layer.

The input system would mix high-density algal seed culture' obtained from the platform exit point with sea or fresh water in addition to the required balance of nutrients and growth stimulants to optimise growth throughout the passage in the platform. Additionally carbon dioxide would be dissolved into the water at this point to saturate this parameter for optima! carbon dioxide conversion without compromising growth from overelevated carbon dioxide concentrations.

Supplementary nutrients and carbon dioxide would be injected at various points downstream on the initial water/nutrients/seed algae injection point to counterbalance the consumption of these raw materials during passage of the photosynthetic suspension through the platform and enhance total photosynthetic flux per surface area of the platfonn at large. Biomass is harvested at various points along the platform and replaced with nutrient-rich water, allowing a more uniform high-density photosynthetic rate everywhere in the platform in a continual-dilution' laminar flow system.

The advantage of this system is that there is no evaporation due to the contained nature of the photosynthetic platform, thus allowing continuous functioning of the system in arid areas of the world over large surface areas. Additionally there would be no contamination with other water-born plant or animal organisms, thereby allowing a high degree of control over the biology of the system's operation and hence it's carbon dioxide sequestering capability.

The problem associated with traditional agricultural fertilisation is that most of the fertiliser is leached out of the soil. However, 100% efficiency in fertiliser delivery and localisation can be maintained in the contained flow high-density aqueous photosynthetic platforms. One essential parameter governing the rate of photosynthesis is temperature and, in the desert, the temperature of the platforms would be high due to the sun's heat, thus optimising this parameter.

Organisms known to thrive in elevated temperatures may also be used (eg thermophilic organisms) and the temperature of the platform may be modulated by the water-height in the lumen and the shape of the surface, such that heat can be lost at night and an overall equilibrium reached during the day-night cycle allowing control of the peak day temperature. This system bears some similarities with the efficient processes of modern hydroponics, and expertise in this field has benefited the development of the contained flow high-density aqueous photosynthetic platform technology.

Preferably the contained flow high-density aqueous photosynthetic platforms would be operated on flat terrain.

As the contained flow high-density aqueous photosynthetic platforms photosynthesise, gaseous oxygen will be generated and accumulate on the upper-side of' the platform. The contained flow high-density aqueous photosynthetic platforms will have regular collection valves positioned at slightly elevated points attached to the top-side that will allow the release of the oxygen and collection from a network of tubes. This pure oxygen can be sold as an immediate product, or released into the atmosphere and sold on the carbon trading market. This latter product constitutes a novel product in the carbon trading sector, which is traditionally based on carbon dioxide emissions and sequestration rates.

The oxygen collected from the contained flow high-density aqueous photosynthetic platforms and released into the atmosphere can also be volumetrically measured very accurately, as compared to the inaccurate carbon dioxide sequestration estimates performed with reforestation carbon-trading proposals. Indeed, it is proposed that the photosynthetic efficiency per surface area will he enormously higher using the platform technology than conventional wood-production via forestry.

The output from the contained flow high-density aqueous photosynthetic platforms contains a high density of biomass, which contains the absorbed carbon. The algal biomass must be efficiently harvested from this mixture and stored appropriately in accordance with the carbon-trading regulations. One method of separation is via precipitation in large tanks and then harvesting the biomass from the base of the tank.

Certain aluminium salts are known to induce precipitation of algae from a suspension state, and can be used. Continual flow centrifugation is another means by which the biomass can be concentrated, and once concentrated the biomass can be dried in the desert heat and sold as foodstuffs or fuel. It can also be processed to obtain other products or stored in accordance with the relevant carbon trading guidelines.

Clarified water containing residual amounts of nutrients can be reinjected into the platform and recycled. Complete clarification is not desirable as a relatively high density seeding starter influx culture would be required at re-injection.

A highly concentrated algal slurry could be transported via pipelines or tankers to sub-oceanic storage vaults or stored as frozen biomass on Antarctica to ensure long- term storage of the carbon dioxide.

Claims

Claims: I) Any algal growth system involving a sealed photosynthetic

bioreactor fed by an external CO2 source designed for use in an open desert.
2) Any algal growth system involving a sealed photosynthetic bioreactor led by an external CO2 source designed for use in an open ocean.
3) Any algal growth system involving a sealed photosynthetic bioreactor fed by an external CO2 source designed for use in any context.
4) The designs and concepts of the flat plastic structures involved in the contained flow high-density aqueous photosynthetic platform.
5) The designs and concepts of the plastic spacers and circulation/turbulence systems involved in the contained flow highdensity aqueous photosynthetic platform.
6) The design and concept of photosynthetic oxygen bubble collection structures in the designs of the plastic structures involved in the contained flow high- density aqueous photosynthetic platform.
7) The design and concept of oxygen collection valves in the contained flow high-density aqueous photosynthetic platform.
8) Any oxygen-harvesting pipe network for collected oxygen from a contained flow high-density aqueous photosynthetic platform.
9) Any multi-point CO2 (as gas liquid or as an aqueous solution) injection system into a contained flow high-density aqueous photosynthetic platform.
10) A sedimentation chamber connected to a contained flow high-density aqueous photosynthetic platform.
11) The integrated concept and design of solar-powered pump systems associated to a contained flow high-density aqueous photosynthetic platform with a continual harvest, CO2 injection, 02 collection and algal growth fluid circulation system.
12) Any heat regulating surface on a contained flow high-density aqueous photosynthetic platform.
13) Any associated continual algal harvesting system involving filtration.
14) Any associated continual algal harvesting system involving sedimentation.
15) Any associated continual algal harvesting system involving centrifugation.