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Abstract This work investigated the optimization of process parameters in the upgrading of the oil extracted from Scenedesmus obliquus microalgae using a novel nickel-impregnated biochar catalyst. The effects of temperature, dodecane-to-oil mass ratio and pressure on the upgraded liquid-phase biofuel yield were evaluated and optimized by central composite design of the response surface methodology (RSM). The model equation generated from RSM showed that dodecane-to-oil mass ratio and pressure, as well as the quadratic effects of all the three factors, were significant model terms in predicting the yield of upgraded liquid-phase biofuel. Maximum liquid biofuel yield was attained at 246.89 °C, 3.72 (w/w) dodecane-to-oil mass ratio, 3.84 MPa hydrogen pressure and 6 h processing time. Validation runs resulted in an upgraded biofuel yield of 69.4%, which was in close agreement with predicted values generated by RSM. The upgraded biofuel comprised of 100% green liquid hydrocarbons containing 94% alkanes and 6% alkenes. Its main fuel properties, such as heating value (43.78 MJ kg−1), elemental composition, density, and viscosity, exceeded those of the fatty acid methyl ester standard and were found comparable to those of petroleum diesel. More importantly, the results of the ultimate analysis and confirmed by the findings from Fourier transform infrared and gas chromatography – mass spectroscopy analyses, showed significantly low oxygen and nitrogen content and absence of sulfur in the upgraded biofuel. Graphical abstract Image Highlights • Novel catalyst was synthesized from rice hull biochar. • The catalyst was used to upgrade Scenedesmus obliquus oil to high-quality biofuel. • Response surface methodology was used to optimize biofuel yield. • High optimum biofuel yield at 69.4 wt. % was obtained. • The biofuel consisted of 100% green liquid hydrocarbons and HHV of 43.78 MJ kg−1. [ABSTRACT FROM AUTHOR]

The continuous development of the economy and the constant improvement of living standards have stimulated the development of animal husbandry. This development has been accompanied by the massive production of animal manure with various bad odors and high heavy metal content, constituting severe damage to ecological security and human health. Traditional disposal methods, including composting and anaerobic digestion, are difficult to achieve satisfactory results due to long processing time, water and soil eutrophication, and toxic gas emissions. However, converting animal manure into bioenergy through pyrolysis is a clean, safe, and promising technique to reduce the amount of waste and produce valuable products. Co-pyrolysis with other materials can decrease the content of heavy metals in biochar and ameliorate the properties of products. The application of catalysts influences the pyrolysis process and product properties positively. The objective of this review is to analyze the properties of animal manure and discuss the recovery of biofuel from harmful animal manure by pyrolysis. A comprehensive analysis of animal manure pyrolysis and related product characteristics will provide a foundation for the sustainable management and scientific disposal of hazardous manure waste. [Display omitted] • Biochar is the primary product of conventional pyrolysis of animal manure. • High temperature enhances the immobilization of heavy metals in biochar. • Co-pyrolysis promotes the reduction of heavy metal content. • The addition of co-feedstock or catalyst influences product properties greatly. [ABSTRACT FROM AUTHOR]

The Antarctic krill, referring to Euphausia superba , feeds phytoplankton, grown up with photosynthesis for CO 2 fixation. Therefore, the use of krill as a raw feedstock for energy production is a highly carbon negative approach, not disturbing the food supply chain of human. Although the krill has high lipid content (up to 40 wt%, dry basis), its use as a raw feedstock for biodiesel production has not been considered. In this study, the feasibility of Euphausia superba to be used as a biodiesel feedstock was scrutinized. Prior to biodiesel production, an annual biodiesel production potential from the krill without disruption of ecosystems was estimated (129% larger than current biodiesel production in Korea). Because krill oil contains high fraction impurities, (trans)esterification with acid catalyst resulted in low yield of biodiesel (6.5 wt%), while non-catalytic transesterification achieved 94.7 wt% of biodiesel yield. To maximize the utilization of krill, solid residue obtained after biodiesel production was synthesized to krill biochars, and they were used as sorptive materials for adsorption of toxic chemicals. Among different model pollutants (Cd(II), Cr(VI), and methylene blue), krill biochar had the best adsorption capacity for Cd(II) (13.7 mg g−1), which is comparable value with other studies. [Display omitted] Biodiesel production from transesterification of lipid in krill and conversion of krill solid residue into biochar, available for adsorption of environmental pollutants. [ABSTRACT FROM AUTHOR]