Biofuel production is possible through anaerobic digestion of activated sludge. Most anaerobic digesters are installed at farms and wastewater treatment facilities where large-scale waste generation is an issue and they wish to produce biofuel from methane gas output of anaerobic digesters. It is known that activated sludge is a feasible feed source for anaerobic microbacteria, but other feed sources high in lipid content may be combined with sludge to produce similar effects.
Cultivated microalgae Chlorella and activated sludge from Amherst, MA Waste Water Treatment plant were studied in three digesters containing differing ratios, 100% algae, 50/50 algae to sludge, and 100% activated sludge to determine if co-digestion of algae and activated sludge is a viable option of gas productivity. During a 28-day cycle of feeding and wasting 50mL of specified sample, the chemical oxygen demand (COD), total solids, nitrogen, phosphorous, proteins, alkalinity, volatile acid alkalinity, and pH were analyzed to ensure the maximum health of the digesters. The gas quantities were collected daily and the contents were analyzed weekly. It is apparent that the 50/50 algae to sludge ratio produced the most amount of gas. Therefore, these results conclude that co-digestion with a 2% algal solution and activated sludge is an alternative feed source for anaerobic digestion.