Inexpensive culturing of freshwater algae in a simulated warm environment using chicken manure medium

Abstract

In recent years, growing algae for biomass production for different purpose has received large interest around the world, because it provides various potential advantages for biofuel production, carbon dioxide mitigation, wastewater treatment, food production and so on. In this study, the freshwater microalgae Chlorella vulgaris and a newly isolated Scenedesmus strain named SIMRIS002 were cultured as cheap and simple as possible aiming at developing an inexpensive method that can be used in developing countries in areas without any facilities. A greenhouse was built which successfully simulated an acceptable arm environment. Plastic bags were manually modified as cheap photobioreactors for algae cultivation Two volumes, 3L and 5L, were tested and the most suitable volume was found to be 3L for cultivations in plastic bags. One type of waste product (chicken manure) was used as a cheap culture nutrient source in the medium. Compared to previous studies, lower amounts of biomass was produced from the algae in this study when growing them in 2%, 6%, 10% and 14% (dry wight per liter) chicken manure. The reason could be that the low chicken manure level provided low concentrations of carbon, nitrogen and phosphorus, which were not enough for optimal algae growth. In addition, because the plastic bag culture were placed under natural Swedish summer light conditions, more than 10000 W/m2 light intensity was reached and therefore the algal growth could be inhibited. Three different gas-exchange methods were investigated during the plastic bag culturing: non-bubbling, natural bubbling and automatic continuous bubbling. Efficient air delivery and good mixing were provided by the bubbles. Thus, growth was clearly improved in automatically bubbled cultures and two times more biomass was found at the end of the cultivations compared to when no bubbling was used. Furthermore, the alkaline environment provided in chicken manure was not suitable for C.vulgaris but was preferred by Scenedesmus SIMRIS002.