Utilization of Agricultural Drainage Water for Biodiesel Feedstock Production and Impact of Different Agricultural Management Practices on Soil Ammonia Oxidizing Communities

The potential of microalgae as a source of renewable energy has received substantial attention, but its economic viability and sustainability requires further optimization of upscaled culture conditions and inexpensive harvesting systems. Wastewater from agricultural activity potentially provides a cost-effective medium that can be used for feedstock production. We investigated the potential of using a native algal strain, Picocystis salinarum, grown together with the filter feeder, Artemia franciscana (brine shrimp) in selenium contaminated and high salinity drainage water, to provide biofuel feedstock . P. salinarum is capable of growing in the high salinity and high Se concentration. Managing the photoperiod and addition of key nutrients such as iron and organic carbons improved Picocystis biomass production up to 82% compared to control conditions. A model describing the relationship between glycerol consumption and P. salinarum biomass and lipid production was developed and can be used for estimation of biomass and lipid production under mixotrophic conditions. The survival, growth rate, and biomass production of A. franciscana were determined in laboratory microcosm and mesocosm experiments. Feeding on P. salinarum, A. franciscana production was lower compared to its growth on a commercial feed, indicating the necessity to increase P. salinarum population densities for the system to be economically feasible. In mesocosms, addition of carbon dioxide increased the C:N ratio by increasing carbon availability, while at the same time lowered pH and increased the bioavailability of phosphorus and iron; these changes were associated with an increase in algae biomass. This in turn supported a higher brine shrimp biomass production. This result suggests that mesocosms are promising systems for testing growth conditions of algal -- shrimp populations and environmental variables for eventual scale-up for biofuel feedstock production. P. salinarum showed potential to support A. franciscana production at a mesocosm scale. Further investigation of lipid production under different conditions and total production costs are necessary to determine the economic feasibility of this system.;Ammonia-oxidizing bacteria (AOB) were considered to be solely responsible for ammonia oxidation in soil, until the discovery of ammonia-oxidizing archaea (AOA) identified through metagenomic and cultivation studies from terrestrial and marine ecosystems. However, it is not clear what environmental and agronomic conditions determine the relative abundance of ammonia oxidizing bacteria (AOB) and ammonia oxidizing archaea (AOA). We evaluated the effect of different fertilizer applications--including no fertilizer (NF), mineral fertilizer (MF) or cover crop (CCF)-- on the composition and abundance of soil ammonia oxidizing communities in both a long-term field experiment and under more controlled laboratory conditions. We found that different fertilizers affected population sizes of ammonia-oxidizing microorganisms. In the field trials, AOA abundance was highest in CCF while AOB abundance was highest in MF. Simulating nitrogen inputs in laboratory microcosms, we found a significant relationship between the abundance of AOB and the measured increase of nitrate concentration. We suggest that AOB, and not AOA, are primarily responsible for ammonium oxidation resulting from cover crop inputs.