Ahmed Atta A

Introduction  Algae are a diverse group of primarily aquatic, single celled, plant like organisms. Most algae have characteristics in common with plants; they have cell walls, contain the green pigment chlorophyll, and manufacture their own food through the process of photosynthesis.  Algal Biomass is made up of three major components namely, Carbohydrates, proteins and Lipids. Most of the oils present is made up of triglycerides.

Cycle of conversion of Algae

Benefits of Producing Algae Oil  Algae is fast growing – each oil-producing cell can mature in just hours  Algae is oil-rich — contains as much as 60% of its dry weight in oil  Algae is carbon neutral – meaning that it does not affect climate like petroleum  Algae is fuel efficient – as much as 1000 times more productive than corn

Challenges of Producing Algae Oil  How to maximize light exposure and CO2 absorption for optimum growth  How to optimize algae biomass harvesting and oil extraction  How to keep energy requirements low and make systems affordable  How to refine algae oil and biomass into finished products

Constituents

Mechanism

Definition  Algae oil is a highly viscous oil so in order to achieve maximum efficiency it needs to be converted to a less viscous oil.  Algal oil is converted into biodiesel through a transesterification process. Oil extracted from the algae is mixed with alcohol and an acid or a base to produce the fatty acid methylesters that makes up the biodiesel.  An excess of methanol is used to force the reaction to favor the right side of the equation. The excess methanol is later recovered and reused. If biomass is grown in a sustained way, its combustion has no impact on the CO2 balance in the atmosphere, because the CO2 emitted by the burning of biomass is offset by the CO2 fixed by photosynthesis.

Growth of culture  Growth of algae culture can be achieved in two ways: open ponds and photobioreactors (PBR). A photo bioreactor is closed equipment which provides a controlled environment and enables high productivity of algae. As it is a closed system, all growth requirements of algae are introduced into the system and controlled according to the requirements.  The photo bioreactor itself is used to control environmental parameters including light. The cylinders are usually made of acrylic, designed to regulate light and dark intervals to enhance growth rate.  Also PBR’s have a built in cleaning system that internally cleans the tube without affecting production. PBRs facilitate better control of culture environment such as carbon dioxide supply, water supply, optimal temperature, efficient exposure to light, culture density, pH levels, gas supply rate, mixing regime.

Photobioreactors

Process Diagram for Biodiesel Production from Algae

Harvesting of culture  Microalgae are grown in a photobioreactor, which is a closed vessel that allows light to penetrate to a  growth medium consisting of water, nutrients, and algal cells.  2) Microalgae harvesting separates the oil rich algae from the water, allowing the water and some algae to  recycle back to the photobioreactor.  3) Oil extraction from the harvested algae. This is most commonly done by solvent extraction, and may be  preceded by mechanical cell disruption as well. The solvent is recovered and reused after this step.  4) Biodiesel production is most often done by transesterification with alcohol and a catalyst.

Conclusion  Biodiesel derived from oil crops is a potential renewable source and carbon neutral alternative to petroleum fuels. However, the high cost and limited supply of renewable oils prevent it from becoming a top competitor for petroleum fuels. As petroleum fuels cost rise and supplies decrease, biodiesel will become more attractive to both investors and consumers. Because biodiesel from oil crops, waste cooking oil and animal fat cannot fulfill a small fraction of the existing demand for transport fuels, microalgae appear to be the only source of renewable biodiesel that is capable of meeting the global demand for transport fuels.

Finance  It is reported that one company could produce 180,000  gallons of biodiesel every year from just one acre of algae, which comes to about  4,000 barrels; at a cost of $25 per barrel or $0.59 per gallon.  Compared to the cost of Petroleum which costs $67.

Feasibility CompanyLocationBusinessFinance support Inventure Chemical Seattle, USAAlgae-jet fuelImperium Renewables; Cedar Grove Investment; Origin OilCalifornia, USAAlgae biodiesel technology Public held ALG Western Oil South AfricaAlgae biodiesel technology Odyssey Oil & Gas

Disadvantages  Highly expensive to setup infrastructure for synthesis of Algae into Biodiesel.  Processing in commercial scale is relatively difficult, mostly processed on small scale (Laboratory).

Alternative  Due to the static cost associated with oil extraction and biodiesel processing and the variability of algal-biomass production, future cost-saving efforts for algal-oil production should focus on the production method of the oil rich algae itself.  This needs to be approached through enhancing algal biology (in terms of biomass yield and oil content) and culture-system engineering.