Friday, July 09, 2010

Increase CO2 utilization in algae biofuel ponds

I have been working in algae based biofuel reactors and applying my work to effective CO2 gas utilization, enhanced nitrate injection and increased circulation of algae. Existing algae systems, although reasonably effective in growing and harvesting algae, have a low CO2 retention time. Spargers generally bubble CO2 gas into the algae stream or bioreactor, and rely on laminar flow to increase retention time and enhance the rate at which algae absorb gas. Most systems lose anywhere from 80 to 95 percent of the gas bubbles in the process, and this becomes either a CO2 emission problem or a CO2 recovery problem.

My system has demonstrated (in a 1000 litre bioreactor) an increase in CO2 utilization from 10 percent to 100 percent. No gas bubbles left the surface of the algae solution. The accepted fact is that algae cannot be blended at high flow rates due to excessive shear rates caused by propellers or turbines. In my system, the shear rate is low enough to blend and pump organic material without harming it. Further, my system allows algae the correct amount of time to fully absorb the available CO2 gas. If a known volume of algae has a specific rate of CO2 absorption, and a system is tuned to deliver that amount, my system can utilize 100 percent of the CO2 gas. This increases or maximizes the algae growth rate and harvest potential.

The main goal of the work is to utilize CO2 emissions from industry and fully convert that CO2 into biomass, biofuel, ethanol, and solid fuel. Existing algae based biofuel systems have two specific weaknesses. Scale-up from the lab, and CO2 utilization. My work in scale-up has been successful largely in part to the mathematical models I have built based on my design. The model uses significantly less power in this scenario. Large scale CO2 sparger or bubbler systems would consume tens of thousands of horsepower on a large refinery-scale. Using my method, this could be less than 500 horsepower in total due to the unique method of delivery.

Large scale pumping and blending of shear sensitive, organic material is indeed possible, and with enhanced CO2 utilization methods, algae based biofuel systems are a practical method of eliminating CO2 emissions in industry.