Factors Affecting Algal Growth By: Sarah Perez

Research Question Which of 13 different silicate samples will, when in the presence of algae, yield the most algal growth over a set period of time? How will algal growth be affected when grown in different pH’s?

Background Information All that is necessary for algae to sustain life is water, CO2, and nutrients (nitrogen,etc.) One of fastest growing plants in world Great potential for an alternative energy source 50% of its mass is oil Biofuel: can produce 1000-5000 gallons of oil per acre compared to 10-100 gallons of oilseed crops AACT plant

Background: AACT Photo Bioreactor: grows algae Anaerobic Bioreactor: converts algal biomass into fuel for power generation and fertilizer Organic Carbon Engine: uses biomass to produce syngas, biochar, and bio-oil. Residual heat and CO2 that is created is recycled back in GPH system to grow algae

Procedure: Silicate Test 3 different trials testing 2 different factors SILICATE TRIALS: Independent Variable: 13 different silicate samples Dependent Variable: amount of algal growth Controlled Variables: amount of water (3 L), amount of algae to start (100 ml), amount of fertilizer (50 ml), amount of light (plant light, 18 hrs on, 6 off), amount of silicate (1.2 ml) Two trials conducted, lasting three weeks each Did not use CO2 tank for second trial

Procedure: pH Test pH TRIAL: Five different pH’s tested with two of each pH 3, 5, 7, 9, 11 Independent Variable: pH Dependent Variable: amount of algal growth Controlled Variables: water (3 L), amount of algae to start (100 ml), amount of light 1 trial lasting 3 weeks Did not use CO2 tank or fertilizer

Ranked subjectively by 2 people Data: Silicate Trial 1 MOST 13 11. 10 2 12. 6 12 13. 1 Mash control 14. 4 7 15. CO2 control 11 8 9 5 3 Ranked subjectively by 2 people

Ranked subjectively by 2 people Data: Silicate Trial 2 MOST Control 12. 5 11 13. 4 13 14. 1 12 9 8 10 7 6 3 2 Ranked subjectively by 2 people

Data: pH Trial MOST pH 11 (#1) pH 9 (#1) pH11 (#2) pH 9 (#2) pH 5 (#2) LEAST

Comparison: Silicate Trials Sample 12 Sample 13

Sample 1 Sample 4

Sample 8 Sample 3

Conclusion: Silicate Samples In the silicate sample trials, there were inconsistencies between the results of which sample produced the most algal growth. The samples that yielded the most and least algal growth, however, were uniform in both experiments. Samples 12 and 13 were consistently in the top 3; therefore, it can be concluded that when algae is in the presence of silicate samples 12 and 13, it will grow more than when in the presence of samples 1-11. Likewise, samples 1 and 4 yield the least algal growth.

Conclusion: pH Trial I have only conducted 1 test, so my results are not definite. The results of my one test offer the conclusion that algae grows better in higher pH’s, specifically 9 and 11, and less in lower pH’s. I would need to run more tests to confirm these results, however.

Improvements: Silicate Trials Same controlled variables for all 3 tests CO2 tank mash More accurate method for measuring amount of starting algae More precise way of comparing algal growth at end of trials

Improvements: pH Trial I could have conducted one or two more identical trials to strengthen my results Tested more pH’s (even numbers) More accurate way of comparing algal growth at end of trial Better way to measure starting amount of algae

Acknowledgements I would like to thank AACT, and specifically Robin Kelson and Makena Johnson, for helping with the setup of these trials and giving us a tour of their facility. It was a really great experience and I am so glad I was given the opportunity to work with this innovative company.

References "Algae Basics - Benefits of Algae." Algae Basics - Benefits of Algae. N.p., n.d. Web. 13 Jan. 2015. "Smithsonian National Museum of Natural History." Algae Research / Department of Botany, National Museum of Natural History, Smithsonian Institution. Smithsonian Museum, 2015. Web. 12 Jan. 2015. “Information about Why Algae Grow in Lakes." Information about Why Algae Grow in Lakes. Access Washington, n.d. Web. 12 Jan. 2015.