• Energy Research
• Closed Access close

Although lignin is one of the most abundant renewable organic materials in the world, it is principally a waste product of the paper industry which is used for the production of heat and power. Hydrothermal lignin depolymerisation aids in facilitating the valorization of lignin in aqueous solutions or suspensions. For the recovery of valuable phenolic products from lignin it is crucial to understand the main reaction pathways of lignin degradation and the reaction kinetics. Batch experiments were carried out for studying the depolymerisation of an enzymatic hydrolysis lignin from spruce wood in near critical water. Phenolic products were extracted from the aqueous phase and quantified via gas chromatography. The main reaction products were grouped (lumped), the main reaction pathways of hydrothermal lignin depolymerisation were discovered and formal kinetic rate coefficients were determined. Optimization of these formal kinetic parameters yielded a satisfying approximation of the experimental yields of phenolic products and describes the most important tendencies over temperature and residence time of solid residue and gas. The model is validated by the comparison with other kinetic studies of the degradation of lignin as well as the decomposition of intermediate phenolics, such as catechols and methoxyphenols.

Although lignin is one of the most abundant renewable organic materials in the world, it is principally a waste product of the paper industry which is used for the production of heat and power. Hydrothermal lignin depolymerisation aids in facilitating the valorization of lignin in aqueous solutions or suspensions. For the recovery of valuable phenolic products from lignin it is crucial to understand the main reaction pathways of lignin degradation and the reaction kinetics. Batch experiments were carried out for studying the depolymerisation of an enzymatic hydrolysis lignin from spruce wood in near critical water. Phenolic products were extracted from the aqueous phase and quantified via gas chromatography. The main reaction products were grouped (lumped), the main reaction pathways of hydrothermal lignin depolymerisation were discovered and formal kinetic rate coefficients were determined. Optimization of these formal kinetic parameters yielded a satisfying approximation of the experimental yields of phenolic products and describes the most important tendencies over temperature and residence time of solid residue and gas. The model is validated by the comparison with other kinetic studies of the degradation of lignin as well as the decomposition of intermediate phenolics, such as catechols and methoxyphenols.

The interest in third generation biofuels from microalgae has been rising during the past years. Meanwhile, it seems not economically feasible to grow algae just for biofuels. Co-products with a higher value should be produced by extracting a particular algae fraction to improve the economics of an algae biorefinery. The present study aims at analyzing the influence of two main microalgae components (lipids and proteins) on the composition and quantity of biocrude oil obtained via hydrothermal liquefaction of two strains (Nannochloropsis gaditana and Scenedesmus almeriensis). The algae were liquefied as raw biomass, after extracting lipids and after extracting proteins in microautoclave experiments at different temperatures (300-375°C) for 5 and 15min. The results indicate that extracting the proteins from the microalgae prior to HTL may be interesting to improve the economics of the process while at the same time reducing the nitrogen content of the biocrude oil.

The interest in third generation biofuels from microalgae has been rising during the past years. Meanwhile, it seems not economically feasible to grow algae just for biofuels. Co-products with a higher value should be produced by extracting a particular algae fraction to improve the economics of an algae biorefinery. The present study aims at analyzing the influence of two main microalgae components (lipids and proteins) on the composition and quantity of biocrude oil obtained via hydrothermal liquefaction of two strains (Nannochloropsis gaditana and Scenedesmus almeriensis). The algae were liquefied as raw biomass, after extracting lipids and after extracting proteins in microautoclave experiments at different temperatures (300-375°C) for 5 and 15min. The results indicate that extracting the proteins from the microalgae prior to HTL may be interesting to improve the economics of the process while at the same time reducing the nitrogen content of the biocrude oil.

Abstract The brown algae Fucus vesiculosus, Laminaria saccharina and Alaria esculenta were subjected to hydrothermal liquefaction (HTL) for 15 min at 350 °C in batch microautoclaves. Further optimization was carried out in view of optimizing the biocrude oil yield, varying the temperature from 330 to 370 °C. The maximum conversion to biocrude was 29.4 ± 1.1 wt.% at 360 °C for A. esculenta. The reaction pathways for macroalgae HTL and its capability for recycling nutrients were also investigated. The aqueous phase showed potential for a partial recovery of the nitrogen (21.2–28.6 wt.%) and sulfur (25.8–34.6 wt.%) from the initial biomass, and an almost total recovery of potassium and sodium. Results indicate that HTL as a sole conversion method to produce biofuel as single product is not recommended for macroalgae due to the low conversion to biocrude oil. At such conditions, its use as post-treatment for the remaining biomass after extracting valuable compounds (especially from the carbohydrate fraction) might be more interesting, and is suggested as the future direction for research.

Abstract The brown algae Fucus vesiculosus, Laminaria saccharina and Alaria esculenta were subjected to hydrothermal liquefaction (HTL) for 15 min at 350 °C in batch microautoclaves. Further optimization was carried out in view of optimizing the biocrude oil yield, varying the temperature from 330 to 370 °C. The maximum conversion to biocrude was 29.4 ± 1.1 wt.% at 360 °C for A. esculenta. The reaction pathways for macroalgae HTL and its capability for recycling nutrients were also investigated. The aqueous phase showed potential for a partial recovery of the nitrogen (21.2–28.6 wt.%) and sulfur (25.8–34.6 wt.%) from the initial biomass, and an almost total recovery of potassium and sodium. Results indicate that HTL as a sole conversion method to produce biofuel as single product is not recommended for macroalgae due to the low conversion to biocrude oil. At such conditions, its use as post-treatment for the remaining biomass after extracting valuable compounds (especially from the carbohydrate fraction) might be more interesting, and is suggested as the future direction for research.