Najmudeen, T.M.; Febna, M.A.A.; Rojith, G., and Zacharia, P.U., 2019. Characterisation of biochar from water hyacinth Eichhornia crassipes and the effects of biochar on the growth of fish and paddy in integrated culture systems. In: Jithendran, K.P.; Saraswathy, R.; Balasubramanian, C.P.; Kumaraguru Vasagam, K.P.; Jayasankar, V.; Raghavan, R.; Alavandi, S.V., and Vijayan, K.K. (eds.), BRAQCON 2019: World Brackishwater Aquaculture Conference. Journal of Coastal Research, Special Issue No. 86, pp. 225–234. Coconut Creek (Florida), ISSN 0749-0208.

Conversion of water hyacinth into useful products is a sustainable way to address the menaces created by them, along with an exploration of beneficial applications. The present study focused on the conversion of water hyacinth into a climate-resilient product ‘biochar’ and its applications in integrated paddy and fish culture systems. The integrated culture of fish with a saline tolerant variety of paddy Pokkali is characterised by low productivity as a traditional culture method. Biochar was produced by pyrolysis technique with water hyacinth, Eichhornia crassipes as substrate. The elemental composition and structural characterization of biochar were done using CHNS analyser, FTIR, XRD, and SEM, respectively. Optimum pyrolysis conditions were finalized and pyrolysis at 300°C for 30 minutes was used for the production of sufficient quantities of biochar for further experiments. Biochar was incorporated into the feed of tilapia, Oreochromis mossambicus in the ratio of 0.5 and 1% and was fed to the fishes grown in tanks for 6 weeks. Weight and length of the fish were found to be enhanced significantly in biochar mixed feed, and the highest growth rate was recorded for the fishes fed with 1% of biochar mixed feed. Biochar amendment to the soil in the culture system at 1% concentration enhanced the specific growth rate of O. mossambicus. Varying proportions of biochar were mixed to soil @ 1, 2, 3, 4 and 5% and the effect of biochar-amended soil on the growth of pokkali was studied for the parameters, root length, shoot length and plant height. Highest growth performances were observed in 4% biochar-soil mixture in comparison to the control. The results of water hyacinth biochar experimentation on fish and paddy growth have been promising, and the work could be considered as a milestone towards further optimization and field level trials to enhance the productivity of integrated culture systems.