Grantee Research Project Results
Final Report: Raceway Reactor for Microalgal Biodiesel Production
EPA Grant Number: SU834696Title: Raceway Reactor for Microalgal Biodiesel Production
Investigators: Khandan, Nirmala , Pegallapati, Ambica Koushik , Ketheesan, Balachandran , Boeing, Weibke , Arudchelvam, Yalini
Institution: New Mexico State University - Main Campus
EPA Project Officer: Page, Angela
Phase: I
Project Period: August 15, 2010 through August 14, 2011
Project Amount: $9,996
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet (2010) RFA Text | Recipients Lists
Research Category: Pollution Prevention/Sustainable Development , P3 Challenge Area - Air Quality , P3 Awards , Sustainable and Healthy Communities
Objective:
Our vision is to demonstrate the practicability of microalgal systems as a sustainable solution to produce biodiesel as a carbon-neutral and renewable energy source and simultaneously sequestering anthropogenic CO2 emissions. The objective under this P3 grant, was to design and demonstrate a novel lab-scale raceway reactor configuration for enhanced algal cultivation and CO2 capture. Specific goals under Phase I of this P3 grant were to:
- construct and evaluate the reactor under a range of operating conditions to identify optimal operating conditions to maximize algal biomass production
- develop a mathematical model of the reactor to predict the energy consumption and algal biomass production
- to calibrate and validate a mathematical model using experimental data.
Summary/Accomplishments (Outputs/Outcomes):
Participating students at New Mexico State University designed and fabricated a 20-L prototype scale version of the proposed airlift/raceway reactor. Preliminary studies on this prototype confirmed that the proposed reactor configuration could be an energy-efficient one for algal cultivation. The following parameters were monitored during these tests: carbon dioxide supply, pH, algal biomass growth, and lipid content. Evaluation methods consisted of development, calibration, and validation of a mechanistic process model for process optimization and scale-up. Key findings from this project can be summarized as follows:
- Power required by the proposed reactor configuration is estimated to be 60-80% less than that the traditional raceway reactors.
- Lipid content in the biomass ranged from 37% with atmospheric air to 75% with 1% CO2-to-air ratio in the case of nannochloropsis; and from 22% at atmospheric air to 35% with 1% CO2-to-air ratio in the case of scenedesmus.
- Supplemental carbon dioxide addition at CO2-to-air ratio of 0.25-0.50% was found to be optimal for lipid production in two algal species: nannochloropsis and scenedesmus.
Conclusions:
Results of this study confirmed that the proposed reactor configuration could be an energyefficient one for algal cultivation. Compared to conventional raceway reactors in use today, the proposed configuration can reduce the energy input by at least 60%. The proposed configuration offers an efficient way to provide supplemental CO2 supply. Compared to CO2 supply from ambient air (at 0.035%), enhanced CO2 supply (at 0.25-0.50%) improved the biomass growth as well as lipid production significantly. By reducing energy input to the process and increasing the lipid yield, the proposed reactor increases the net energy yield in the algal cultivation process. In addition, the ability to utilize CO2 supply can be beneficial in carbon management.
Supplemental Keywords:
Raceway reactor, modeling, sustainability, carbon fixation, algal biodieselThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.