Utilization of food processing wastes for biological production will ease part of the disposal problem, especially the potential hazards of eutrophication, and at the same time recycle the inherently rich plant nutrients in the waste materials.
The present investigation is an attempt to study the feasibility of using five food processing wastes, including carrot, coconut, eggshell, soybean, and sugarcane, for culturing Chlorella pyrenoidosa (a unicellular green alga).
When using test tubes as culture tubes, all the concentrations (0.5, 1, 3, and 5% weight/volume aqueous extracts) of eggshell waste had similar growth rates, whereas all the concentrations of sugarcane and carrot wastes had higher growth rates of algal cells compared with the control group using Bristol solution as the culture medium. However, only 0.5 and 1% soybean waste and 3 and 5% coconut waste had higher algal growth than the control.
When larger containers were used, similar results were obtained except for 5% soybean waste, which produced the highest growth rate. This was possibly due to the modified growing conditions. Chlorella pyrenoidosa harvested from soybean and sugarcane wastes had higher cell numbers, dry weight, and protein contents than those cultivated in the Bristol solution.
These waste materials contained high levels of essential plant nutrients including nitrogen, phosphorus, and potassium. However, the rather high levels of organic carbon and soluble carbohydrate in some of the wastes, such as coconut and carrot wastes, seemed to affect the contents of protein and chlorophyll of the waste-grown algae.
The fact that these waste materials contained no hazardous substances would render the algal products safe for subsequent usage (as animal feeds or even for human consumption), unlike the sewage-grown algae which accumulated a substantial level of trace metals.
It is suggested that the process of algal culture could be incorporated in large-scale food processing industries for the dual purpose of treating the wastes and mass producing edible protein.