Aquilant Scientific – Processing algae and other biomass to form biopolymer by-products

For many years the conversion of biomass into biofuel and ethanol was a time-consuming and multi-step procedure that was both economically inefficient and wasteful.  Additionally conventional methods are inhibited by water.  However this investigation using Teledyne Isco syringe pumps shows that there is a fast, single step and efficient method for the conversion of biomass into biofuel and sugars to produce ethanol that can be performed in the presence of water.This method includes a feedstock that is hydrolysed or derivatized in a reactor in a presence of an optional acid catalyst, and optionally in the presence of water in a pressurized reactor to yield the desired products.  The feedstock for this process can be for example algae or other oil-containing material that may also contain potentially fermentable cellulosic material, protein or both.  Prior to reaction the feedstock can be dried or wet.

The dried algae or other feedstock is ground to reduce its particle size and then transferred to the loading vessel, wherein the feedstock is mixed with the selected reagents to form biomass slurry.  In order to keep the biomass suspended and agitated, the biomass slurry is pumped in a loop from the loading vessel to the high pressure pumps, where the slurry is extracted as needed, and then back to the loading vessel.  One of the major challenges of conducting these experiments on a laboratory scale in a continuous manner is the ability to pump the solid biomass in the form of liquid slurry into the reactor in a continuous manner without pulsing.   This is not a large obstacle with scaled up processes, since commercially available pumps used in the petroleum and waste treatment industry are readily available.  However in the laboratory we must run at much lower flow rates in order to study the kinetics and avoid the other constraints that such a large pump would impose on a small reactor and laboratory setting.

The required conditions were a pump that could:

• Inject material into a pressurized system
• Be continuous without pulsing
• Have a relatively low flow rates of less than 150ml per minute
• Have tunable flow rates
• Be capable of keeping the biomass in suspension without settling

To achieve these desired pump conditions, 2 Teledyne Isco Syringe Pumps (model 500HV-High Viscosity) and their corresponding overhead mixers and 3/8” continuous flow air valve package were used.

After the biomass slurry passes through the pumps it enters the reactor zone.  The continuous pipe reactor is designed to allow sufficient residence time for the reaction to complete and is operated under a target pressure and temperature range.  The pipe allows for reasonable reaction to occur with minimal vessel complexity.  The reaction can be carried out for a period of between 1-120 minutes, depending on the selected reaction system and operating temperature.

The reaction product slurry typically consists of the algae or biomass pulp (containing cleaved cellulosic material, shortened petides, and amino acids), crude free fatty acids and fatty acid derivatives, excess alcohol, catalyst, water and glycerine.  The resulting cleaved cellulosic materials will be in the range of 0-50wt% of the product slurry.  The reaction slurry is transferred to a Liquid/Solid Separation system.  In this step, the liquid fraction is separated from the solids portion, and each biomass fraction is further separated and purified.

Algae and other biomass feedstocks are normally difficult to unbind and separate into their free biomass constituents, such as fractions consisting of protein, polysaccharides and fats.  However it is shown here that alternative biomass feedstocks can be reacted under well-designed conditions to facilitate the conversion of these feedstocks into their desired products of free carbohydrates, free amino acids, free fats and shorter chain oligomers and derivatives of biomass constituents.

The importance in accomplishing this task on a laboratory scale is the need of a versatile pump in order to facilitate the biomass slurry into the reactor under the desired pressures and flow rates.

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