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Technology: CO2 absorption by microalgae to generate biomass

Technology: CO2 absorption by microalgae to generate biomass Date: 22/06/10
Technology Definition:Bubbling CO2 through algal cultivation systems can greatly increase production yields of algae. There has been significant interest in the last few decades in the potential of algae to produce vast quantities of oil at a price that is competitive with crude oil.
Proponents:Many companies and research institutes globally (reportedly 200 or more ventures exist). Several large global companies including BP, ExxonMobil, Chevron, Connoco Philips, Virgin Fuels, Anglo Coal and Royal Dutch Shell all have sizeable research interests.

Item Specific sub-criterion Score Evaluation comments
Technology Maturity
1.01 Timeframe to deployment 2 Although large-scale open systems do exist the use of CO2 to enhance growth is not common practice with the majority of systems operating today which typically produce high value nutraceuticals rather than energy products (e.g. transport fuel).There are many technological and operational issues to be addressed before a robust large scale system can produce oil at a price competitive with crude oil. Despite claims of some firms, most proponents of the technology agree that there is great potential but the technology is 5-10 years away from commercial realisation.
Scale-Up Potential
2.01 Scale-up potential 2 Where algal oil is used as a feedstock for biodiesel production, The potential market is very large. The market for other products of algae (e.g. algal meal) may not be as large, though algal meal could also be further processed into commodity products such as char.Algenol currently propose a project in Mexico capturing and reusing 1.5Mtpa CO2, which would demonstrate the concept on a large scale on a single site. It remains to be seen whether this project will be fully implemented.
2.02 Geographical constraints on the production system 2 The amount of CO2 which can be captured from a point source will be constrained by the land available on a case by case basis. Systems are ideally suited to locations with high solar irradiance and adequate marginal land. Access to a water source is also desirable. Products can be readily transported using existing methods and infrastructure.
Value for Money
3.01 Commercial viability 2 The use of recycled CO2 for algae cultivation is still in the early research and development stages. There are currently no large scale algae cultivation projects in operation to support the potential economic and commercial feasibility of the technology.The likely use of the algae would be for the large scale production of biomass fuel which has a large potential market. It is forecast that by 2022 algae biofuels will be the largest biofuel category overall, accounting for 40 billion of the estimated 109 billion gallons of biofuels produced.14Algae farms require a large amount of suitable land and ideally these would be located close by the CO2 source. Some initial research done at universities and during pilot projects suggest that it could take an open pond of about 8 square miles (5120 acre pond) to produce enough algae to remove carbon dioxide from a midsized – 500 MW – power plant.15 This high land requirement may limit the commercial viability of the technology in areas with high land prices.
3.02 Competitiveness with other emerging technologies 1 Algae biofuel would need to compete with alternative biofuels such as those derived from food feedstock (e.g. rapeseed oil, soyabean oil and hemp) as well as those derived from vegetable and animal fats. However, given the biofuel forecasts stated in 3.01 There is significant potential for algae biofuel to enter the market. Furthermore, algae biofuel may be a suitable alternative to those using feedstock as it will not be affected by the relative demand of the feedstock as a food source as it does not use these often valuable crops as feedstock. However, The relative costs of production of these biofuels will be the key driver.On a wider scale algae biofuel will have to compete with current fuel sources (e.g. petroleum) if it is to be considered as a commercial alternative for use as a transport fuel. Again, The determining feature of its success will be its price competitiveness in the market. At its current stage of development the technology is expensive (the current cost of producing algae for carbon sequestration in BC (British Columbia) is $793 per tonne of CO2). At present the cost of producing the end product (biomass fuel) is very high in comparison to existing products (Assuming that algal biomass had content of 25 per cent oil, Then the estimated cost of production would be $20,000/tonne of oil, or over 20-fold higher than current vegetable or crude oil prices).16At present it appears unlikely that algae biofuel will be able to compete with alternative products in the current market.
3.03 Barriers / Incentives / Drivers 1 There are a number of barriers which will affect the value for money and commercialism of this technology including:
  • The use the technology is most suited to regions with high solar resource and large areas of marginal land surrounding point CO2 sources (providing the most productive environment for algae cultivation) which will inhibit the implementation of the technology in many regions.
  • Algae farms are large and appropriate land large enough to accommodate technology for the CO2 generation of a power plant will be difficult to source and expensive (Estimated capital cost of algal farm per hectare is: $138,000 with operating costs of $43,800 pa).17
  • At the current stage of development the technology is expensive (the current cost of producing algae for carbon sequestration in BC (British Columbia) is $793 per tonne of CO2).18
  • The cost of producing the end product (biomass fuel) is very high in comparison to existing alternative fuel sources.
  • Current studies assume that the algae production takes place at the site of the CO2 source (with CCS costs of c.$40 tonne) and so additional transport and storage costs will need to be accounted for.19

The research into the technology has attracted both public funding from Department of Energy and Department for transport in the UK and funding from a number of private investors.

CO2 Abatement Potential, Environmental and Social Benefits
4.01 Permanence of Storage 2 CO2 which is absorbed by algae is used to generate biomass. Dependant on the system there may be a mixture of end products produced from this. A basic system may generate only biodiesel in this case the storage is temporary as the CO2 is re-released when the fuel is burnt. Another system may generate biodiesel, supply crude algal oil for processing to plastics, useful nutraceuticals may be extracted and used in food supplements, The algal biomass remaining after extraction may then go on to produce animal feed, fertiliser, or biochar, or be digested anaerobically to produce biogas. Some of these avenues will result in permanent storage. The second ‘biorefinery’ option is more desirable as risk is spread across several supply chains.
4.02 Lifecycle CO2 analysis 3 The production of algae consumes CO2 at the rate of 1.8 tonnes of CO2 for every tonne of algal biomass produced. However is likely the majority of this CO2 will be re-released. There will also be some CO2 produced during cultivation due to the power requirement of pumping large volumes of water as well as CO2 production from any downstream processing operations.Edge Environment Case Study Result: 0.41t CO2-e/t reused.Case Study Description: Algae farm integrated with a coal-fired power station in Eastern Australia, with process requirements similar to those identified in public documents of MBD Energy.
4.03 Environmental Benefit (Non CO2 abatement related) 1 Algae cultivation systems can be used as a step in waste water treatment – to remove certain compounds from waste water/sewage.
4.04 Social Benefit (Non CO2 abatement related) 1 Algae systems which are constructed on marginal land and used to produce biofuels would not compete with food crops for arable land. The use of algal biofuels avoids the current food vs. fuel problems surrounding first generation soy/palm/corn/ wheat/canola biofuels.
Developing Countries
5.01 Applicability to developing countries 2 Does not specifically favour developing countries. Solar irradiance and available marginal land are the main factors which will constrain the development of such systems.

14 Biofuels 2010: Spotting the Next Wave; Joshua Kagan the Promoteus Institute | Travis Bradford the Prometheus Institute (December 2009)

15 Algae based CCS, CO2 Carbon Capture Algae biosequestration – Power Plant CCS. http://www.powerplantccs.com/ccs/ cap/fut/alg/alg.html

16 Opportunities and challenges in algae biofuels production; A position paper by Dr. John R. Benemann in line with Algae World 2008

17 Greenhouse gas sequestration by algae – energy and greenhouse gas life cycle studies; Peter K. Campbell, Tom Beer, David Batten

18 Microalgae technologies and processes for biofuels/bioenergy production in British Columbria; The Seed Science Ltd (January 2009)

19 Opportunities and challenges in algae biofuels production; A Position Paper by Dr. John R. Benemann in line with Algae World 2008