Utility of Duckweeds as Source of Biomass Energy: a Review

The quest for alternative sources of energy has evoked the interest in exploring potentials of living biological wastes as new energy materials. Duckweeds are produced abundantly as weeds in freshwater surface bodies and can be a source of biomass for bioenergy productions. There are approximately 40 species of this group worldwide belonging to five genera (Spirodela, Lemna, Wolfiella, Wolffia and Landoltia). The structural peculiarities (small plant size, limited life cycle, high duplication rate, etc.) and chemical characteristics (dry weight basis): 17.6-35 % (carbohydrate), 21-38 % (starch), 16-41.7 % (crude protein), 8.8-15.6 % (crude fibre) and 4.5-9 % (lipid) make duckweed as possible feedstock for biomass-based energy operations. The high contents of valuable fatty acids (palmitic acid and linoleic acid) and starch (3-75 %) in duckweed biomass suggest its utility in biorefinery. Recent lab-scale studies have shown remarkable results in terms of energy yield during the processes like anaerobic digestion, incineration, pyrolysis, gasification, oxidation, etc. Another good quality of duckweeds is its hyperaccumulative properties for a variety of water pollutants. Therefore, this group of weeds has been recommended widely for designing on-site phytoremediation system for community wastewater treatment. Thus, duckweed technology can be adopted as coupled technology to harness two environmental approaches, i.e. wastewater treatment and energy biomass production for sustainable development of the human society.