More efficient algae oil production

Dr. Neil Canter, Contributing Editor | TLT Tech Beat June 2009

A process called Quantum Fracturing provides the nutrients needed to accelerate growth.

KEY CONCEPTS
• In growing algae efficiently, three factors, including the delivery of nutrients, extraction of oil and development of a continuous process, must be taken into consideration.
• A new process called Quantum Fracturing has been developed to more effectively provide nutrients to the algae.
• Algae oil can be isolated more efficiently through the use of microwaves. This process does not involve the use of energy-intensive mechanical methods of organic solvents.

The large increase in energy costs seen in the first half of 2008 has spurred interest in looking at alternative technologies such as renewable sources. A good deal of attention has been paid to determining if biodiesel can be developed into a viable alternative.

As discussed in a recent column, biodiesel is susceptible to oxidation particularly if the vegetable source is soybean oil (1). The addition of specific antioxidants can, if done properly, retard this process.

One other factor in using vegetable oil such as soybean is the negative impact on the food market. This aspect has led those in the alternative energy industry to look at growing algae as an alternative. A recent TLT article discusses the potential for using algae as a source of biodiesel or even hydrogen gas (2).

There are several major challenges in growing algae needed to produce fuel. Dr. Vikram Pattarkine, chief technology officer for OriginOil, Inc., says, “Three factors must be considered in growing algae efficiently. Delivery of carbon dioxide and other nutrients must be done efficiently or else the algae could run out of something and stop growing. The oil that algae generate must be extracted efficiently by a low-energy process. Finally, a continuous, efficient process must be developed to enable algae to grow continuously and produce sufficient oil on a commercial scale.” 

Since algae prefer to grow in reasonably calm environments, carbon dioxide and other nutrients must be introduced into the algae culture with the least amount of agitation. Besides carbon dioxide, algae rely on nutrients such as nitrogen and phosphorus to grow. Pattarkine points out that smaller quantities of micronutrients such as manganese and zinc also are required.

Oil extraction can be very challenging because the algae cell wall is tough. This wall must be pierced to isolate the oil.

New technology is required to enable algae to grow efficiently enough so that the process is cost competitive with petroleum. One approach that has just been developed to address this problem is known as Quantum Fracturing.™ 

QUANTUM FRACTURING
Algae grows best if the nutrients needed are provided at the microscale so maximum absorption can be realized by the cells. This is the principle behind the concept of Quantum Fracturing.

Quantum Fracturing uses a cavitation effect to fracture carbon dioxide, water and other nutrients into microsized bubbles smaller than 60 micrometers.

Ensuring algae have sufficient light is also very important. Pattarkine says, “Imagine a pond containing algae, these organisms will only grow no more than a couple of inches deep because there is not enough light; the algae culture is self-shading. Letting the algae grow naturally will only generate one layer of an algae crop.” 

Better productivity is needed to grow algae commercially. Pattarkine indicates that this is accomplished through the use of a helix bioreactor. He adds, “The bioreactor grows algae layer by layer. This growth is achieved by arranging low-energy lights in a helix or spiral pattern. A rotating vertical shaft moves the lights so that they are in close proximity to the algae. Cells are no more than 0.5 of an inch away from a light source.” 

Depending on the species, algae only use certain wavelengths of light to grow. Pattarkine points out that the main wavelengths used are blue and red. Figure 3 shows a helix bioreactor growing algae.


Figure 3. A helix bioreactor grows algae more efficiently using Quantum Fracturing to deliver nutrients and microwaves to isolate the oil. (Courtesy of OriginOil, Inc.)

Algae do not need to be exposed to light continuously. Pattarkine explains, “For optimum growth, algae usually need to absorb light for one second followed by metabolism for approximately six to 10 seconds. We can tailor the reactor system depending upon the algae species to control the light wavelength used, light intensity and interval between exposures to maximize growth.” 

The time needed to double algae biomass in this fashion ranges from a few hours to 72 hours. The amount of oil produced depends on the species grown. Pattarkine says, “Algae can produce between 10% and 60% oil per cell dry mass.” 

The final step in the process is to fracture the algae cell wall and isolate the oil, which is known as lysing. Current techniques include the use of energy-intensive mechanical methods and the use of organic solvents such as benzene. The former are expensive and energy inefficient, while the latter can lead to handling, safety and disposal concerns.

In a much more effective approach, algae biomass grown in the bioreactor is subjected initially to low wattage, frequency-tuned microwave bursts designed to weaken the cell walls followed by a higher-pressure version that breaks them. This procedure involves the generation and propagation of a shock wave.

Pattarkine says, “Quantum Fracturing combines with other effects such as microwaves to create a more efficient process that uses less energy and does not require solvents.” 

Helix bioreactors can be placed in series or in parallel to grow algae oil on a large scale using this approach. Micron-sized bubbles containing nutrients can be pumped into each of the bioreactors. Once algae have grown sufficiently, the resulting cells can be pumped into an extraction unit to isolate oil and biomass.

When algae have grown sufficiently to fill the volume of the bioreactor, growth will cease, and removal to the extraction unit is required. The system is designed to retain a small percentage of the algae in the bioreactor to maximize productivity.

This operating system is being licensed for use by companies growing and harvesting algae. Further details can be found in a recent U.S. Patent Application (3) and by visiting www.OriginOil.com. 

REFERENCES
1. Canter, N. (2009), “Examining Biodiesel Oxidation,” TLT, 65 (3), pp 18 -19
2. Torrey, M. (2008), “Algae in the Tank,” TLT, 64 (12), pp 26 – 32
3. Eckleberry, N. and Eckleberry, T. (2009), “Algae Growth System for Oil Production,” US Patent Application 2009/0029445 A1

Neil Canter heads his own consulting company, Chemical Solutions, in Willow Grove, Pa. Ideas for Tech Beat items can be sent to him at neilcanter@comcast.net.