Algae-based Biodiesel: Current Procedures and Innovations

By: Dr. John Kyndt – Head Scientist of the Renewable Energy Program at Advanced Energy Creations Lab .

Here is another article praising the characteristics of these little power sources of the future. Certain microalgae can have a significant amount of lipids as storage material (up to 70 % of their dry weight).

These lipids can be extracted as algal oil and are an excellent source for the production of biodiesel. After extracting the algal oils, detailed analysis on the quality and composition of the oil are performed using high-end technologies (e.g. GC-MS, pyrolis-GC, ICP-MS and LC-MS).

Methods to extract the lipids can typically be divided in two catagories: mechanical and chemical methods…

Chemical methods: Oil extraction using organic solvents (e.g. Soxhlet extraction with hexane) and supercritical fluid/CO2 extraction.

Mechanical methods: include pressing the oil and cavitation (ultrasonic-assisted extraction).

New research in this area is on identifying the biocompatibility of solvents, testing the efficiency of more environmental friendly methods and reducing the overall energy use and costs of these processes.

In addition, to increase the oil yield per liter and drive down the production costs, we are currently developing algae that have increased oil content per biomass unit through genetic engineering and environmental growth control.

Once the oil is extracted it is subjected to transesterification. Esterification is the process whereby glycerol is split off from the more complex lipids to produce biodiesel (fatty acid methyl esters, FAME; mostly C9 through C17 hydrocarbons).

Although it has a complex name, this procedure is fairly simple and can be performed by several well established methods. After removal of the glycerin, the quality of the resulting biodiesel is analyzed and tested to meet standard criteria for high quality biodiesel, e.g. measuring glycerin and glycerides, analyze FAME content, determination of trace methanol and sulfur detection.

Besides the obvious advantages of renewability and sustainability there are several advantages to the use of biodiesel:

•    Biodiesel has superior lubricating properties. This increases the life of fuel injection systems and saves engine maintenance cost.
•    Algae biodiesel has virtually no sulfur content. Sulfur content in microalgae is typically less than 0.1% mass (dry weight), being much lower than the 0.3% mass upper limit for biodiesel specifications and will therefore allow production of fuel without any additional cleanup step. Sulfur is a dangerous pollutant, and has even been suspected in cancer clusters near airport runways where exhaust may fall in concentrated quantities during takeoff.
•    Biodiesel has less dangerous particulate matter (about 47 % less than petrol diesel) and therefore burns cleaner.

In previous articles we have already pointed out the advantages of using algae over other plant sources for biodiesel production, such as the fact that algae has over 200 times the yield compared to the best-performing plant/vegetable oils, algae can grow anywhere there is sunshine, and are not competing with food crops for land space.

The ‘cloud point’, which is temperature at which biodiesel starts to solidify, is typically about 32 0F (0 0C). This is one of the reasons why, in general, biodiesel is offered as a blend with petrodiesel (e.g. B20; 20% biodiesel) in many parts of the world.

Various additives will lower the cloud point of biodiesel making it more suitable in colder climates. Algae based biodiesel could in theory provide enhanced cold weather performance properties.

Algae biodiesel can contain more polyunsaturated fatty acids which tend to decrease the stability of biodiesel. However, polyunsaturates have much lower melting points which could result in much better cold weather properties than biodiesel from many other bio-feedstocks.

This “cold weather optimization” is one of the critical factors to overcome to achieve a global use of biodiesel.

It is the ultimate goal of everyone involved in biodiesel research to develop a streamlined and automated harvesting and extraction system that does not use hazardous chemicals, that generates a high quality green fuel and that can be scaled up easily with cost efficiency in mind.