Optimisation and characterisation of water hyacinth-based biochar and bio-oils produced by thermochemical processes for sustainable biocatalyst and biofuel production

The valorisation of water hyacinth-derived biochar and bio-oils produced by thermochemical processes, such as pyrolysis, hydrothermal liquefaction, and microwaves, in commercial applications has recently garnered attention. To the best of our knowledge, there are limited studies that employ water hyacinth-based biochar as biocatalysts and bio-oils fir biofuel production. Hence, the purpose of this study was to use biochar as biocatalysts and bio-oils as feedstocks in the production of biojet fuel and biodiesel. The process time, temperature, biomass content, and adsorbent ratio were varied to maximise the microwave biochar yield (93.27 wt%) and bio-oil yield (4.72 wt%). The pyrolysis productivity was optimised using Box-Behnken design with Response Surface Methodology, generating an optimum biochar yield of 28.77 wt%. The Ni-biochar biocatalyst resulted in the highest biojet fuel yield (63.28 wt%) and biodiesel yield (36.19 wt%). Furthermore, the Ni-biochar biocatalyst was compared with Ni-solid catalysts (Al 2 O 3 , ZSM-5, and Pd/C) for validation, where the biojet fuel yield was 82.19 wt% and the biodiesel yield was 98.19 wt% using the Pd/C catalyst. Bio-oil from microwave treatment resulted in the highest biojet fuel yield of 47.71 wt% and biodiesel yield of 85.98 wt% using the Ni-Al 2 O 3 catalyst, and 16.98 wt% and 64.28 wt% using the Ni-biochar biocatalyst, respectively. The characteristics of the liquid fuels were thoroughly examined, which were comparable to those of commercial fuels and fulfilled the ASTM standard.