Sustainable Production of Algal Biomass and Biofuels Using Swine Wastewater in North Carolina, US

Algae were recently considered as a promising third-generation biofuel feedstock due to their superior productivity, high oil content, and environmentally friendly nature. However, the sustainable production became the major constraint facing commercial development of algal biofuels. For this study, firstly, a factorial experimental design was used to analyze the effects of the process parameters including temperatures of 8-25 degrees C, light intensity of 150-900 molm(-2)s(-1), and light duration of 6-24 h on the biomass yields of local alga Chlamydomonas debaryana in swine wastewater. The results were fitted with a quadratic equation (R-2 = 0.9706). The factors of temperature, light duration, the interaction of light intensity-light duration, and the quadratic effect of temperature were statistically significant. When evaluating different scenarios for the sustainable production of algal biomass and biofuels in North Carolina, US, it showed that: (a) Growing C. debaryana in a 10-acre pond on swine wastewater under local weather conditions would yield algal biomass of 113 tonnes/year; (b) If all swine wastewater generated in North Carolina was treated with algae, it will require 137-485 acres of ponds, yielding biomass of 5048-10,468 tonnes/year and algal oil of 1010-2094 tonnes/year. Annually, hundreds of tonnes of nitrogen and phosphorus could be removed from swine wastewater. The required area is mainly dependent on the growth rate of algal species.