• Energy Research

Abstract Hydrothermal co-liquefaction of biomass has attracted considerable research interest as it has potential to reduce logistics costs, increase biocrude yield and improve biocrude quality. This work summarizes hydrothermal co-liquefaction of various biomass, in which co-liquefaction effect (either synergistic, antagonistic or additive) on biocrude yield of was examined. Observed synergetic effects must be critically assessed due to inconsistent reaction/separation conditions, uncertain statistical significance of experimental data and varied indicator of co-liquefaction effect in the studies reported. The chemical interactions among biomass model components (cellulose, hemicellulose, lignin, lipid, and protein) were also thoroughly investigated to explore the origin of co-liquefaction effect. Recent progresses on modeling hydrothermal liquefaction was reviewed as well, including quantitative models for predicting product yield as a function of the biochemical composition of biomass feedstock and/or reaction parameters, and kinetics models of reaction network among individual component of biomass. These models are useful tools to investigate co-liquefaction effect, optimize feedstock mixing for co-liquefaction, and ultimately facilitate more efficient biomass conversion. The major challenges in the study of co-liquefaction are identified such as statistical significance of co-liquefaction effect, evaluation of co-liquefaction effect under identical liquefaction and separation conditions, and understanding of co-liquefaction effect at a molecular level.

Abstract Hydrothermal co-liquefaction of biomass has attracted considerable research interest as it has potential to reduce logistics costs, increase biocrude yield and improve biocrude quality. This work summarizes hydrothermal co-liquefaction of various biomass, in which co-liquefaction effect (either synergistic, antagonistic or additive) on biocrude yield of was examined. Observed synergetic effects must be critically assessed due to inconsistent reaction/separation conditions, uncertain statistical significance of experimental data and varied indicator of co-liquefaction effect in the studies reported. The chemical interactions among biomass model components (cellulose, hemicellulose, lignin, lipid, and protein) were also thoroughly investigated to explore the origin of co-liquefaction effect. Recent progresses on modeling hydrothermal liquefaction was reviewed as well, including quantitative models for predicting product yield as a function of the biochemical composition of biomass feedstock and/or reaction parameters, and kinetics models of reaction network among individual component of biomass. These models are useful tools to investigate co-liquefaction effect, optimize feedstock mixing for co-liquefaction, and ultimately facilitate more efficient biomass conversion. The major challenges in the study of co-liquefaction are identified such as statistical significance of co-liquefaction effect, evaluation of co-liquefaction effect under identical liquefaction and separation conditions, and understanding of co-liquefaction effect at a molecular level.

Abstract Microwave-assisted hydrothermal liquefaction (MW-HTL) is a promising technology for the production of biocrude from biomass that usually consists of saccharide, lipid, protein and lignin. A few attempts have been recently made to study the MW-HTL of biomass, however exploration on biocrude formation under MW irradiation presents a gap in the research. MW-HTL of biomass model components and their mixtures were carried out, and it was found that saccharide and lipid interacted synergistically to produce higher volumes of biocrude under MW irradiation, while the antagonistic interaction was observed for protein-lipid and lignin-lipid. The influence of microwave and conventional heating on the yield/quality of biocrude was also compared by HTL of model components (individual, binary, ternary and quaternary mixtures) and actual feedstocks. The results of this comparison revealed that the influence of heating method depends on the nature of feedstock, for instance, MW irradiation led to a lower biocrude yield for saccharide, comparable biocrude yield for protein and lignin, and higher biocrude yield for lipids than conventional heating. HTL of Chlorella sp. microalgae under MW irradiation produced more biocrude than conventional heating, but HTL of spent coffee grounds and sawdust was not affected by different heating methods. The heating method also had negligible influence on the chemical composition of the resulting biocrude. Principle component analysis of the vast dataset obtained in this study also suggested that the influence of the selected heating method was highly associated with the substrates, however there is no certain preference on one heating method over the other.

Abstract Microwave-assisted hydrothermal liquefaction (MW-HTL) is a promising technology for the production of biocrude from biomass that usually consists of saccharide, lipid, protein and lignin. A few attempts have been recently made to study the MW-HTL of biomass, however exploration on biocrude formation under MW irradiation presents a gap in the research. MW-HTL of biomass model components and their mixtures were carried out, and it was found that saccharide and lipid interacted synergistically to produce higher volumes of biocrude under MW irradiation, while the antagonistic interaction was observed for protein-lipid and lignin-lipid. The influence of microwave and conventional heating on the yield/quality of biocrude was also compared by HTL of model components (individual, binary, ternary and quaternary mixtures) and actual feedstocks. The results of this comparison revealed that the influence of heating method depends on the nature of feedstock, for instance, MW irradiation led to a lower biocrude yield for saccharide, comparable biocrude yield for protein and lignin, and higher biocrude yield for lipids than conventional heating. HTL of Chlorella sp. microalgae under MW irradiation produced more biocrude than conventional heating, but HTL of spent coffee grounds and sawdust was not affected by different heating methods. The heating method also had negligible influence on the chemical composition of the resulting biocrude. Principle component analysis of the vast dataset obtained in this study also suggested that the influence of the selected heating method was highly associated with the substrates, however there is no certain preference on one heating method over the other.

AbstractTransesterification is the most common method of producing biodiesel from vegetable oils. A comparative study on the optimization of reaction variables for refined canola oil, unrefined canola oil, and unrefined camelina oil using a four-factor (temperature, time, molar ratio of methanol to oil, and catalyst loading) face-centered central composite design (FCCCD) was carried out. The optimum settings of these four factors that jointly maximize product, fatty acid methyl ester (FAME) and biodiesel yields for each of refined canola, unrefined canola and unrefined camelina were determined. Results showed that the optimized conditions were associated with the fatty acid profile and physical properties of the parent oils. The optimum temperature of vegetable oil with low polyunsaturation degree was higher than that of oils with high polyunsaturation degree. High free fatty acid content in parent oils led to low optimized catalyst concentration, and the decreased reaction rate could be compensated by increased reaction temperature due to significant interaction effect between reaction temperature and catalyst loading in the transesterification process. The highest biodiesel yields from the optimum setting for refined canola oil, unrefined canola oil, and unrefined camelina oil were 97.7%, 95.2%, and 95.6%, respectively. This study provided guidelines on how to optimize different reaction variables taking economic viability and feedstock availability into consideration when producing biodiesel at plant scale.

AbstractTransesterification is the most common method of producing biodiesel from vegetable oils. A comparative study on the optimization of reaction variables for refined canola oil, unrefined canola oil, and unrefined camelina oil using a four-factor (temperature, time, molar ratio of methanol to oil, and catalyst loading) face-centered central composite design (FCCCD) was carried out. The optimum settings of these four factors that jointly maximize product, fatty acid methyl ester (FAME) and biodiesel yields for each of refined canola, unrefined canola and unrefined camelina were determined. Results showed that the optimized conditions were associated with the fatty acid profile and physical properties of the parent oils. The optimum temperature of vegetable oil with low polyunsaturation degree was higher than that of oils with high polyunsaturation degree. High free fatty acid content in parent oils led to low optimized catalyst concentration, and the decreased reaction rate could be compensated by increased reaction temperature due to significant interaction effect between reaction temperature and catalyst loading in the transesterification process. The highest biodiesel yields from the optimum setting for refined canola oil, unrefined canola oil, and unrefined camelina oil were 97.7%, 95.2%, and 95.6%, respectively. This study provided guidelines on how to optimize different reaction variables taking economic viability and feedstock availability into consideration when producing biodiesel at plant scale.