Abstract
A promising solution to rising petroleum prices and depleting fossil fuel resources is microalgae: a fast growing, renewable, environmentally benign crop that can offer energy security without compromising valuable land, water or the environment. But conversion of algae to biofuel has not achieved economic viability. This project offers a solution to algae’s production limitations by designing equipment and processes to cultivate, harvest, extract and transesterify algae’s lipids into an energy positive biofuel. To enhance Spirogyra’s growth, a photoautotrophic bioreactor was engineered with three double walled rotating vessels containing mechanical and air agitation. The inner vessels were filled with algae solution. Each outer vessel was filled with either Helium, Neon, or atmospheric air to determine which gas filtered wavelengths that resulted in the highest photosynthetic efficiency. A controlled nutrient chamber provided 12 cubic ft. of CO₂ and O₂ for the algae solution. A two-fold harvesting system was developed using ionic bonding and pH manipulation. The wet algae slurry was introduced to a pressurized osmotic sonication system engineered to frack Spirogyra’s cell wall for lipid release. The lipids were then recycled through the pressurized system for transesterification using a homogeneous base catalyst, reducing reaction & static time.
Photosynthetic efficiency rates were determined by hemacytometer cell counts during the twelve weeks of testing. Results showed Spirogyra cultivated under red-orange light filtered by Neon gas grew 14% more than Spirogyra cultivated under blue-green light filtered by Helium gas and 20% more than unfiltered natural light. Weekly CO₂ airborne tests confirmed photosynthesis rates increased in direct proportion to CO₂ consumption for the first 8 weeks, but after this optimal growing period, CO₂ consumption outpaced growth rate by 2:1. Weekly pH monitoring confirmed Spirogyra cultivated in Neon conditions absorbed more CO₂, as the average pH level was always more basic than the other vessels’ pH levels. To facilitate flocculation, Spirogyra’s CO₂ diet was terminated and Na₂CO₃ was added to the solution to increase pH. Through ionic bonding and IFAs, the algae cells formed a matrix using Fe₂O₃. The resulting floc produced by the Neon vessel had a volume of 30cm³ versus 26cm³ for the Helium vessel, and 24cm³ for the natural. These results confirmed the hemacytometer findings; Spirogyra cultivated under the red-orange spectrum produced an average of 16.5% more floc than its counterparts. The resulting slurry from each vessel was placed in the “cellulose blaster” that engaged osmotic shock, homogenization and sonication for lipid extraction. Volumetric results revealed Spirogyra cultivated in Neon conditions had a lipid volume of 1.8cm³ compared to 1.4cm³ for Helium and 1.1cm³ for natural. Resulting lipids were transesterified into a biofuel using Ba(OH)₂ and CH₄O, under ultrasonic conditions.
The project’s goal to create innovative processes and equipment to increase algae’s growth and synthesize its lipids into a biofuel was achieved. By eliminating costly multi-steps and harmful reactants, the production of oilgae can become both economically efficient and environmental sustainable.
Photosynthetic efficiency rates were determined by hemacytometer cell counts during the twelve weeks of testing. Results showed Spirogyra cultivated under red-orange light filtered by Neon gas grew 14% more than Spirogyra cultivated under blue-green light filtered by Helium gas and 20% more than unfiltered natural light. Weekly CO₂ airborne tests confirmed photosynthesis rates increased in direct proportion to CO₂ consumption for the first 8 weeks, but after this optimal growing period, CO₂ consumption outpaced growth rate by 2:1. Weekly pH monitoring confirmed Spirogyra cultivated in Neon conditions absorbed more CO₂, as the average pH level was always more basic than the other vessels’ pH levels. To facilitate flocculation, Spirogyra’s CO₂ diet was terminated and Na₂CO₃ was added to the solution to increase pH. Through ionic bonding and IFAs, the algae cells formed a matrix using Fe₂O₃. The resulting floc produced by the Neon vessel had a volume of 30cm³ versus 26cm³ for the Helium vessel, and 24cm³ for the natural. These results confirmed the hemacytometer findings; Spirogyra cultivated under the red-orange spectrum produced an average of 16.5% more floc than its counterparts. The resulting slurry from each vessel was placed in the “cellulose blaster” that engaged osmotic shock, homogenization and sonication for lipid extraction. Volumetric results revealed Spirogyra cultivated in Neon conditions had a lipid volume of 1.8cm³ compared to 1.4cm³ for Helium and 1.1cm³ for natural. Resulting lipids were transesterified into a biofuel using Ba(OH)₂ and CH₄O, under ultrasonic conditions.
The project’s goal to create innovative processes and equipment to increase algae’s growth and synthesize its lipids into a biofuel was achieved. By eliminating costly multi-steps and harmful reactants, the production of oilgae can become both economically efficient and environmental sustainable.