Rising oil prices force harder focus on biofuels

21st February 2013

Sugar, domestic waste, grass, wood and even tobacco are being actively investigated as potential biofuels. One of the key targets is algae because they are easy to grow and their oil is very energy efficient.

For example, Californian company OriginOil has unveiled a pilot system for algae growth and harvesting. At the heart of the new system is a series of 200-gallon tanks which can be individually configured and managed for various strains, growth strategies, and lighting geometries. The tanks are illuminated with LED light sticks submerged in icicle-like arrays. A stirrer circulates the algae slowly around the lights.

Once the algae reaches harvest concentration they are sent to the integrated extraction system, a combination of ultrasound generation and low-power electromagnetic pulsing. This new system has a throughput of five gallons per minute, which easily keeps up with the daily output of the pilot system. After extraction, a series of settling tanks separates the oils and biomass for eventual use as fuel and valuable by-products. A water recycling system completes the loop so the process can start again.

The company's dynamic control system manages the operation of the growth phase, releasing carbon dioxide and other nutrients as the algae needs it. While bottled carbon dioxide is currently used, an in-house generator is planned to test real-world scenarios where exhaust gas is processed for its carbon dioxide.

The use of algae as a fuel will also be enhanced by a new production process that uses catalytically actives particles to convert them. US company Sachtleben, a unit of Rockwood, has developed the new particles. It is now working with Augsburg College and biodiesel producer Ever Cat Fuels, which is currently designing the first commercial-scale pilot plant incorporating this innovative fluidised-bed catalyst system at Isanti, Minnesota, near Minneapolis.

The new process is simpler, sustainable and more energy efficient, as opposed to existing biodiesel production that often relies on expensive food crops, primarily cereal grains and soy. In addition, the production of biodiesel, as practiced for many years, involves a catalytic process followed by complex removal of the dissolved catalyst and purification of the biodiesel. As well as algae oil, this new process, also converts inferior fats and paper-industry waste into high-quality diesel fuel.

Sachtleben's catalytically active particles play a major role in the new approach for the significantly simpler production of biodiesel. The particles are, on the one hand, sufficiently stable to withstand the extreme reaction conditions, and are, on the other hand, the factor which makes rapid and complete transesterification of the feedstocks possible at all. Up until now, the reaction time in the process took several hours, whereas the new process utilising Sachtleben particles takes just a few seconds.

For its part, Dow is working with Algenol Biofuels to build and operate a pilot-scale algae-based integrated biorefinery that will convert carbon dioxide into ethanol. The facility is planned to be located at Dow's Freeport, Texas site.

Algenol's technology uses carbon dioxide,salt water, sunlight and non-arable land to produce ethanol.Dow, National Renewable Energy Laboratory (NREL), the Georgia Institute of Technology (Georgia Tech) and Membrane Technology & Research are contributing science, expertise, and technology to the project.

Algenol has submitted its formal request to obtain a grant from the US Department of Energy for financial support to successfully conduct the pilot. Upon approval of the grant, Dow and the other collaborators will work with Algenol to demonstrate the technology at a level to sufficiently prove that it can be implemented on a commercial scale.

In addition to leasing the land for the pilot-scale facility, Dow plans to develop the advanced materials and specialty films for the photobioreactor system. Dow will also provide the technology and expertise related to water treatment solutions and will provide Algenol with access to a carbon dioxide source for the biorefinery from a nearby manufacturing facility. The carbon dioxide will be supplied to the algae in the photobioreactors and will serve as the carbon source for the ethanol produced. The result is a carbon dioxide capture process which converts industrially-derived gas into more sustainable fuels and chemicals.

Meanwhile other technologies are nearer to commercial production. For example, UOP continues to build on its joint venture with Ensyn. Together they offer Ensyn's proven Rapid Thermal Processing (RTP) technology to convert second generation biomass like forest and agricultural residuals to pyrolysis oil for use in power and heating applications (Fig. 1).

The RTP process is a fast thermal process where biomass is rapidly heated in the absence of oxygen. The biomass is vapourised and then rapidly cooled to generate high yields of pyrolysis oil. The process uses a circulating transported fluidised bed reactor system similar to that used in the UOP fluid catalytic cracking technology. RTP typically yields 65-75wt per cent pyrolysis oil from dried woody biomass which can be used as fuel for industrial heat and electrical generation.

Pyrolysis oil itself is clean burning with minimal sulphur and nitrogen content. The pyrolysis oil produced using RTP is almost carbon neutral and is marketed by the jv as an ideal solution for customers wishing to reduce their carbon footprint (Fig. 2).


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