Bioethanol production from batch and continuous phytoremediation systems

Abstract

The effectiveness of water hyacinth (Eichhornia crassipes) in remediating municipal wastewater and producing bioethanol in batch and continuous systems was compared with water lettuce (Pistia stratiotes) and water spinach (Ipomoea aquatica). Batch experiment was conducted using stagnant wastewater system and compared with continuous experiment in order to determine the best treatment system for nutrients and pollutants removal while producing high amount of biomass for bioethanol production. The batch experiment was conducted for 7 days while continuous experiment was conducted for 18 days for each of the aquatic plant. The results for the comparison between rhizofiltration plants have shown that water lettuce has better removal performance compared with water hyacinth and water spinach. The continuous system showed better performance in treatment rate and biomass production compared to batch system. The biomass harvested from water hyacinth, water lettuce and water spinach were 772±37 g/kg, 794±75 g/kg and 702±69 g/kg, respectively. Dinitrosalicyclic test was conducted to measure the reduction of sugar from plant biomass. The concentration of sugar produced by water hyacinth was 21.2±2.7 g/L, while water lettuce was 23.5±3.8 g/L, which was slightly higher than water hyacinth’s sugar production. Water spinach produced the lowest sugar concentration with only 15.5±3.3 g/L. The production of bioethanol estimated from water lettuce was 0.13±0.01 g/g bioethanol. Meanwhile, water hyacinth produced 0.12±0.01 g/g of bioethanol, a value lower than water lettuce. Due to the low concentration of sugar, water spinach managed to produce only 0.10±0.02 g/g bioethanol. In conclusion, water lettuce shows better performance compared with water hyacinth in remediating wastewater and producing biofuel.