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[Display omitted] • Efficient co-valorization of waste cooking oil into biofuel and carbon nanotubes. • Natural biochar shows excellent deoxygenation performance and good stability. • Correlation between AAEM in biochar and selectivity of A&E and HCs in bio-oil. • Potential for obtained biofuel to serve as a precursor for jet fuel. • Feasibility and profitability of integrated production process demonstrated. Valorizing renewable precursors into high-quality biofuel and functional carbon nanomaterials can considerably improve the economic viability. Here, we propose a process for integrated production of high-quality biofuel and carbon nanotubes from waste cooking oil via catalytic pyrolysis coupling with chemical vapor deposition (CVD) technology. The natural biochar catalyst demonstrates excellent deoxygenation performance and good stability in catalytic pyrolysis process. The alkali/alkaline earth metal species (AAEMs) content in biochar catalysts has a strong correlation with the selectivity of esters and hydrocarbons in bio-oil. The biofuel obtained under optimal conditions exhibited potential as a precursor for jet fuel. The CVD process convert pyrolysis gas into carbon nanotubes with yield of 2.13%. The technical–economic analysis demonstrated the feasibility of the integrated process, projecting profitability and substantial total profit over a ten-year period. Overall, this study improves the economic viability of the waste cooking oil pyrolysis process and supports its wider commercial application. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Three types of biochar can efficiently activate hydrogen peroxide. • Biochar/H 2 O 2 systems exhibited high tetracycline degradation efficiency. • Catalytic property of biochar depends on the amounts of PFRs. • Biomass types and its compositions were crucial for the formation of PFRs. • Electron transfer pathways could be the catalytic mechanisms of biochar. Abstract Biochar, a green material that possesses high catalytic potential due to its persistent free radicals (PFRs), has attracted increasing attention in the removal of refractory pollutants from water. The influences of biomass types (bamboo, corn stalk, and pig manure) and its compositions (metals and phenolic compounds) on the formation of PFRs in biochar were investigated by electron paramagnetic resonance (EPR). It was found that the amounts of PFRs in biochar would decrease sharply with the decrease of the initial metals and phenolic compounds existed in biomass, and the effect of metals contents on PFRs formation was much greater than that of phenolic compounds contents. This finding was supported by the results obtained from elemental analysis and molar H/C analysis of three types of biochar, which suggested that pig-manure biochar (PM500) had the highest concentrations of PFRs of 14.13 × 1018 spins·g−1 due to the high content of metals and phenolic compounds in pig manure. The EPR trapping experiment and Linear sweep voltammetry (LSV) measurements in biochar/H 2 O 2 systems showed that OH was the dominant reactive radical and electrons transfer pathways might be responsible for the activation of H 2 O 2 by biochar. Possible degradation pathways of the tetracycline in biochar/H 2 O 2 systems were also proposed. Besides, high degradation efficiency and good stability were observed in real wastewater application of the PM500/H 2 O 2 system. These findings would provide a clearer insight into the formation mechanisms of PFRs in biochar, and also present a better strategy for biochar preparation and application in Fenton-like system. [ABSTRACT FROM AUTHOR]

Energy recovery via waste utilization in gasification process is an attractive alternative energy source which is expected to supersede part of the energy from fossil fuels. To enhance the H 2 -rich syngas production from residual biomass mixed with polymeric waste, a dual stage process involving catalytic steam gasification and tar cracking was integrated as a promising alternative technology for clean fuel production. Generally, the presence of tar causes syngas degradation and has been identified as one of the major impurities from the gasification process. This study shows the results obtained from an integrated process with optimization process conditions to enhance H 2 -rich syngas yield. Nickel and dolomite were used as cheap and effective catalysts in fluidized and fixed bed gasifiers respectively, which resulted in high-quality syngas production with a maximum hydrogen yield of 284.1 g H2 kg −1 feedstock and carbon conversion efficiency (CCE) of 92.4 wt%. Furthermore, the study eventuates the upgrading of the bio-char to carbon nano-tubes (CNT). In fact CNT could be further employed either in gasification process or as electrocatalyst supporting materials for low-temperature fuel cells. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new technique was developed to measure the kinetics of fast pyrolysis up to 380 K/s. • The decomposition activation energy was greatly reduced in fast pyrolysis conditions. • TGA-derived kinetic parameters failed to represent the fast pyrolysis process. • Fast pyrolysis enhanced bio-oil products by minimizing secondary reactions. • Fast pyrolysis slightly increased pore volume and surface area of biochar product. Converting algal biomass to clean energy via a thermochemical pathway is an emerging technique for tackling environment and energy issues. Traditional kinetic studies on biomass pyrolysis employ a thermogravimetric analyzer (TGA) which heats the biomass sample at a rate of 0 ∼ 2 K s−1, so TGA could only replicate the thermal behavior of the biomass sample in a fixed bed reactor. However, biomass samples can be heated at a rate over ∼102 K s−1 in industrial reactors, including fluidized beds, spouted beds, or rotary kilns due to the direct contact between biomass samples and the solid heat carriers, thus TGA is incapable to reproduce these thermal behaviors. In view of the limitation of TGA in fast heating cases, this study has developed a fast-heating thermo-balance consisting of wire-mesh and wireless power supply technique to investigate the kinetics of fast pyrolysis. Seaweed is fast-growing and can be considered a promising feedstock for biofuel production. Therefore, this study selected seaweed as representative biomass waste and compared the pyrolysis behaviors under both slow and fast pyrolysis conditions. A key finding was the TGA-derived kinetic parameters were unable to describe the pyrolysis rate under fast pyrolysis conditions with significant overestimation. When compared to slow pyrolysis, fast pyrolysis can increase bio-oil yield by about 3–17%, but the N- and S-containing compounds in the bio-oil increase by about 1.1% and 0.15% respectively at a final temperature of 700 °C. Fast pyrolysis produced about 16–53% more CO 2 than slow pyrolysis above a final temperature of 500 °C. The polarity of compounds in biochar was reduced with increasing temperature and the presence of CaO was only found in biochar at a high temperature of 700 °C. The specific surface area of biochar was higher under fast heating pyrolysis (5.534–7.469 m2 g−1) than that under slow heating pyrolysis (4.076–6.414 m2 g−1). [ABSTRACT FROM AUTHOR]

• Co-pyrolysis is an eco-friendly sewage sludge treatment process. • Mixing co-feed biomass with sewage sludge reduced the environmental burden. • All examined scenarios reduced the global warming potential. • All scenarios achieved positive energy balance with product energy recovery. • Transportation distance significantly affects scenarios' environmental outcome. To address the gaps in current research on sewage sludge (SS) pyrolysis, this study examined the feasibility of the environmental and energy demands of co-pyrolysis as an SS treatment process. The analyses included a cradle-to-gate life cycle assessment, carbon emission and credit assessment, energy recovery calculations, and sensitivity analysis. Sawdust (SD) and wheat straw (WS) were chosen as co-feeds for the co-pyrolysis scenarios; four mixing ratios (20, 40, 60, and 80 wt%) were examined for each co-feed. The functional unit was 1000 kg of bio-oil. Mixing the co-feed biomass with SS reduced the overall environmental burden by 58–83 %; WS/SS co-pyrolysis performed better than SD/SS in this respect. All examined scenarios reduced the global warming potential (GWP) and achieved a net positive energy balance; SD/SS co-pyrolysis was more desirable owing to high energy recovery. The additional gas turbine operation generated a process energy demand of 23–224 %. GWP and terrestrial ecotoxicity potential are indicators that are significantly affected by co-feed material transportation. Sensitivity analysis revealed that the transportation of feedstock and pyrolysis products should be prioritised to limit the environmental burden of the process. Co-pyrolysis is an eco-friendly SS treatment method, and its economic viability should be further investigated. [ABSTRACT FROM AUTHOR]

Abstract: Alkali lignin as an example of waste plant biomass was subjected in a batch reactor to decomposition in sub- and supercritical water. Hydrothermolysis of alkali lignin with relatively highmolecular-weight led to the production of phenolic compounds such as guaiacol and catechol, as well as phenol, m-cresol, p-cresols and o-cresol. Both an increase growth in conversion time and an increase in reaction temperature promoted secondary reactions: degradation of alkali lignin decomposition products, leading to, their repolymerization and carbonization. The components of the liquid fractions of products were examined by GC–MS and HPLC, whereas the solid charred post-reaction residues were analyzed by elemental analysis and FTIR. [Copyright &y& Elsevier]