Amy Millmier Schmidt
Date of this Version
Goedeken, M. K. 2017. Cultivation of Chlorella sorokiniana using beef feedlot runoff holding pond effluent.
A study was conducted to test the suitability of utilizing beef feedlot runoff holding pond effluent for cultivating algae. The algae strain used, Chlorella sorokiniana, was previously identified as a potential energy feedstock for cattle. The previous research was initiated in pursuit of a goal to develop a cycle of utilizing nutrients from beef manure to cultivate algae and then utilizing dewatered algae as a feed supplement for beef cattle.
Runoff holding pond effluent samples were collected from commercial beef production operations in Nebraska during spring 2016. Equal portions of samples from each cooperating farm were composited and then aliquoted into vessels to which treatments were randomly applied. Treatments were designed to evaluate algae growth under varied dilutions of effluent, pre-treatment processes, and supplementation with nitrogen and phosphorus. Growth characteristics under treatments were compared to algae growth in Bold’s Basal Medium (BBM).
Algae concentration under treatments was evaluated daily by manual enumeration using a hemocytometer and via light absorbance using a spectrophotometer. A prediction equation was then developed to assess the effectiveness of using light absorbance as a rapid method for quantifying cell density in runoff holding pond effluent.
Only one treatment, 60% autoclaved pond effluent diluted with water, was effective for cultivating algae to a concentration similar (p < 0.05) to the BBM treatment. The prediction model was reliable (R2=0.75) for samples with algae concentrations greater than 200,000 cells mL-1.
Study results suggest that the nutrient profile of beef feedlot runoff holding pond effluent is suitable for growing Chlorella sorokiniana, but competition for nutrients or consumption by other organisms inhibits growth. While the prediction of algae cell concentration in solutions containing beef feedlot runoff holding pond effluent using light absorbance appears to be valid at algae cell concentrations above 200,000 cells mL-1, suspended solids in effluent, the presence of non-algae microorganisms, and low algae cell density at the initiation of the trials limits the ability of the model to accurately predict cell counts under these conditions.
Advisor: Amy Millmier Schmidt and Yufeng Ge