Toward Enhanced Fixation of CO2 in Aquatic Biomass: Focus on Microalgae

The need to reduce the CO2 footprint of human activities calls for the utilization of new means of production and new sources of products. Microalgae are a very promising source of a large variety of products, from fuels to chemicals for multiple industrial applications (e.g., dyes, pharmaceutical products, cosmetics, food and feed, new materials for high tech manufacture), and for processes such as wastewater treatment. Algae, as photosynthetic organisms, use light to energize the synthesis of organic matter and differently from most terrestrial plants, can be cultured on land that is not used for crop production. We describe the main factors contributing to microalgae productivity in artificial cultivation systems and discuss the research areas that still need investigation in order to pave the way to the generation of photosynthetic cell factories. We shall comment on the main caveats of the possible mode of improving photosynthetic efficiency and to optimize the partitioning of fixed C to products of commercial relevance. We address the problem of the selection of the appropriate strain and of the consequences of their diverse physiology and culture conditions for a successful commercial application. Finally, we shall provide state of the art information on cell factories chassis by means of synthetic biology approaches to produce chemicals of interest.

section_content:  The algae-based products industry is expanding rapidly for higher value (non-fuel/energy) products, providing near term opportunities (bioenergy production in a biorefinery context, as a coproduct) but also increased competition for algal products markets and suitable land for siting facilities • Growth rates are 10-30 g m - 2 day -1, depending on location and cultivation system, with realistic algal oil content of 12-20%

• Oil and biomass productivity inverse relationship is main target of strain engineering to increase biofuel yields
section_name: Global Industrial Development of Algae Technologies

section_content: The quantity of water (whether fresh water or saline water) required  for algae cultivation and the quantity of freshwater addition and water purge to maintain the appropriate water chemistry. Supply  of the key nutrients for algal growth-nitrogen, phosphorus, and CO 2 needs to be ensured to not impact global supplies Appropriate  land area with suitable climate and slope, near water and nutrient sources Energy  return on investment (EROI). Algal biofuel production would have to produce sufficiently more energy than is required in cultivation and fuel conversion to be sustainable.
section_name: Sustainability considerations

section_content: . Algal biofuel production would have to produce a GHG benefit relative to other fuel options such as fossil fuels. Estimates of life-cycle GHG emissions of algal biofuels span a wide range, and depend on many factors including the source of CO 2 and the disposition of bio-products. • Calculations using one TEA model applied to algae productivity estimated at 6 different locations show a 3. 5-fold range in estimated costs of production, (3. 1 -11. 0 € kg -1 )

• All of these projected costs are 6-10-fold higher than what is considered to be economically viable for fuel production • Large range in net CO 2 per MJ biofuel produced (-2. 6-7. 3 kg CO 2 eq MJ -1 )

• LCA modeling choices are major driver, as are processing differences • A standardized/harmonized approach is needed for LCA/TEA modeling • Macroalgae yields range widely, 5 -30 tonnes ha -1 yr -1, with up to 20,000 m 3 biomethane potential ha -1 yr -1

• Unlikely that cast seaweed resource sufficient to provide large quantities of liquid transportation fuels, however biogas can be upgraded and injected into the existing gas grid to supplement methane fuel demands

• Cast and cultivated seaweeds may have to be combined, perhaps also with terrestrial biomass, to achieve a consistent year-round supply of either gaseous or liquid biofuels
section_name: GHG emissions over the life cycle of algal biofuels 

section_content: IEA Bioenergy has authored a comprehensive updated report on the status and prospects for algae-based bioenergy production, "State of Technology Review -Algae Bioenergy" The report will e-publish in the next week and be available on both IEA Bioenergy's and Task 39's web sites:  http://www. IEABioenergy. com  http://www. Task39. org
section_name: Conclusions

section_content: Algae remain a promising source of bioenergy feedstock thanks to high photosynthetic efficiency but prospects for primary algae-based energy/fuels production are poor in the near-to mid-term due to the relatively high cost of growing and harvesting algal biomass Algae processing in a biorefinery context may permit economically feasible coproduction of bioenergy products in nearer term, as may integration with wastewater treatment  There is a clear, urgent need for more open data sharing and harmonization of analytical approaches, from cultivation to product isolation, to TEA and LCA modeling, to identify and prioritize the barriers that need to be overcome for commercialization
section_name: Key Findings:

section_name: Project Participants' & Contributions

section_content: Task members, spanning 5 tasks (34, 37, 38, 39, 42)
section_name: Broad contributions from IEA Bioenergy Executive Committee and 

section_content: Thank you! Are there any questions? www. IEABioenergy. com
section_name: and 8 countries