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Green diesel derived from sustainable biomass is an alternative and potential energy source to petroleum fossil fuel replacement in response to reducing carbon footprint and achieving a circular economy, which has sparked public interest and concern in advancing renewable energy development. Catalytic deoxygenation (CDO) is a promising method because it can process a wide variety of feedstocks and produce a diverse range of fuels. The CDO of soybean oil (SO) was executed using a modified low-cost dolomite catalyst denoted as NiO-CD catalyst and its performance has been compared with commercial zeolite heterogeneous-based catalysts such as ZSM-5, HY-zeolite and FCC. The NiO-CD catalyst exhibited exceptional deoxygenation ability, attaining an 88.6 % removal efficiency of oxygenated compounds, markedly surpassing all commercially available zeolite catalysts. The highest degree of CDO of SO via decarboxylation/decarbonylation (deCOx) reaction was achieved due to improvement in particle size, mesoporous structure and the presence of the synergistic effect of modified bi-functional acid-base properties of NiO-CaO/MgO catalyst. To investigate the effect of NiO-CD catalyst loading ranging from 1 to 7 wt%, a One Factor At a Time (OFAT) optimisation study was performed. The current study found that an optimised NiO-CD catalyst loading of 5 wt% yielded the highest green diesel (50.5 wt%) with an 88.63 % hydrocarbon composition. The influence of catalyst loading on deoxygenation activity is significant in green diesel production using NiO-CD catalyst.

Energy generation from waste biomass offers a promising solution for reducing greenhouse gas emissions and promoting a circular economy. This study investigates the energy potential of various organic materials, including rice husk, soybean, lemon myrtle, waste coffee ground, and empty fruit bunch, co-pyrolysed with HDPE at 500 °C and 50:50 blending ratio for 1 h. Proximate, ultimate, and thermogravimetric analyses were conducted up to 700 °C to determine elemental composition and thermal behaviour. Dulong's formula, modified Dulong's formula, and Vandralek's equation were utilised to assess energy content. Proximate analysis revealed rice husk as the highest in volatile matter (73.08 %), while waste coffee ground had the lowest (32.0 %), and HDPE showed 89.90 %. Ultimate analysis showed organic waste carbon ranges from 25.59 % to 48.75 %, and HDPE at 82.24 %. Pyrolysis reactions yielded distinct distributions of bio-oil, char, and gas, with empty fruit bunch producing the highest oil percentage (26.49 %), lemon myrtle yielding the highest gas (31.07 %), and waste coffee ground favouring char production (74.89 %). Discrepancies in heating values were observed, with Dulong's formula underestimating values for rice husk, soybean, and waste coffee ground (−10 % to −35 %) and slightly overestimating for lemon myrtle, empty fruit bunch, and HDPE (1 %–25 %). The modified Dulong formula accentuated underestimations, particularly for soybean (−451 %). The Vandralek formula showed positive error ranges (8 %) for biomass samples but underestimated HDPE. This study underscores biomass and HDPE as viable alternatives to conventional energy sources and suggests avenues for future research while highlighting environmental benefits.

This work investigates the optimization of reaction parameters with the Taguchi method for catalytic deoxygenation of waste cooking oil (WCO) as an alternative renewable fuel process. Commercial sulphated-ferric (II) oxide/alumina oxide catalyst has the potential as a deoxygenation catalyst due to its good physicochemical properties which enhance the removal of oxygenated species. The obtained pyrolysis oil analysed by GC-MS revealed the selectivity of the pyrolysis oil mostly in the range of light diesel and kerosene fraction. From an analysis of variance (ANOVA), temperature awarded the most significant impact (86.62%) in this catalytic deoxygenation as compared to three other parameters followed by reaction time > N2 flow > catalyst loading. From the GC-MS analysis, the maximum renewable diesel fraction of 49.66% was obtained at 400 °C, 1 wt% of catalyst, 90 min of reaction time and 20 cm3/min N2 flow. The predicted model by Taguchi in the present study validated by the experimental work shows a promising application in optimising the catalytic pyrolysis process for future use.