Saqib Sohail Toor

Hydrothermal liquefaction of Spirulina and Nannochloropsis salina under subcritical and supercritical water conditions

Six hydrothermal liquefaction experiments on Nannochloropsis salina and Spirulina platensis at subcritical and supercritical water conditions (220–375 °C, 20–255 bar) were carried out to explore the feasibility of extracting lipids from wet algae, preserving nutrients in lipid-extracted algae solid residue, and recycling process water for algae cultivation. GC–MS, elemental analyzer, FT-IR, calorimeter and nutrient analysis were used to analyze bio-crude, lipid-extracted algae and water samples produced in the hydrothermal liquefaction process. The highest bio-crude yield of 46% was obtained on N. salina at 350 °C and 175 bar. For S. platensis algae sample, the optimal hydrothermal liquefaction condition appears to be at 310 °C and 115 bar, while the optimal condition for N. salina is at 350 °C and 175 bar. Preliminary data also indicate that a lipid-extracted algae solid residue sample obtained in the hydrothermal liquefaction process contains a high level of proteins.

Conceptual design of an integrated hydrothermal liquefaction and biogas plant for sustainable bioenergy production.

Initial process studies carried out in Aspen Plus on an integrated thermochemical conversion process are presented herein. In the simulations, a hydrothermal liquefaction (HTL) plant is combined with a biogas plant (BP), such that the digestate from the BP is converted to a biocrude in the HTL process. This biorefinery concept offers a sophisticated and sustainable way of converting organic residuals into a range of high-value biofuel streams in addition to combined heat and power (CHP) production. The primary goal of this study is to provide an initial estimate of the feasibility of such a process. By adding a diesel-quality-fuel output to the process, the product value is increased significantly compared to a conventional BP. An input of 1000 kg h(-1) manure delivers approximately 30-38 kg h(-1) fuel and 38-61 kg h(-1) biogas. The biogas can be used to upgrade the biocrude, to supply the gas grid or for CHP. An estimated 62-84% of the biomass energy can be recovered in the biofuels.

Hydrothermal liquefaction of biomass

Biomass is one of the most abundant sources of renewable energy, and will be an important part of a more sustainable future energy system. In addition to direct combustion, there is growing attention on conversion of biomass into liquid energy carriers. These conversion methods are divided into biochemical/biotechnical methods and thermochemical methods, such as direct combustion, pyrolysis, gasification, liquefaction, etc. This chapter focuses on hydrothermal liquefaction, where high pressures and intermediate temperatures together with the presence of water are used to convert biomass into liquid biofuels, with the aim of describing the current status and development challenges of the technology. During the hydrothermal liquefaction process, the biomass macromolecules are first hydrolyzed and/or degraded into smaller molecules. Many of the produced molecules are unstable and reactive and can recombine into larger ones. During this process, a substantial part of the oxygen in the biomass is removed by dehydration or decarboxylation. The chemical properties of the product are mostly dependent of the biomass substrate composition. Biomass consists of various components such as carbohydrates, lignin, protein, and fat, and each of them produce distinct groups of compounds when processed individually. When processed together in different ratios, they will most likely cross-influence each other and thus the composition of the product. Processing conditions including temperature, pressure, residence time, catalyst, and type of solvent are important for the bio-oil yield and product quality.

Subcritical Hydrothermal Liquefaction of Barley Straw in Fresh Water and Recycled Aqueous Phase

Barley straw was liquefied in fresh water and the aqueous phase obtained after liquefaction process at 300 °C. The effect of water recirculation on bio-oil yield and properties was investigated. Results showed that bio-oil yield increased gradually to 38.4 wt % with the addition of recycled aqueous phase. The bio-oil contained similar functional groups and had higher heating values in the range of 27.29–29.34 MJ/kg. It showed that aqueous phase can be utilized as an effective solvent.

Lignocellulosic Biomass—Thermal Pre-treatment with Steam

With the ever rising demand for more energy and the limited availability of depleted world resources, many are beginning to look for alternatives to fossil fuels. Liquid biofuel, in particular, is of key interest to decrease our dependency on fuels produced from imported petroleum. Biomass pre-treatment remains one of the most pressing challenges in terms of cost-effective production of biofuels. The digestibility of lignocellulosic biomass is limited by different factors such as the lignin content, the crystallinity of cellulose and the available cellulose accessibility to hydrolytic enzymes. A number of different pre-treatment methods are known to enhance the digestibility of lignocellulosic biomass by affecting these limiting factors. Some of them are: milling, thermal pre-treatment with steam or hot water, acid pre-treatment, and alkaline pre-treatment. This chapter will focus on one of the more promising technologies; thermal pre-treatment with steam.

Optimizing the conditions for hydrothermal liquefaction of barley straw for bio-crude oil production using response surface methodology

The present paper examines the conversion of barley straw to bio-crude oil (BO) via hydrothermal liquefaction. Response surface methodology based on central composite design was utilized to optimize the conditions of four independent variables including reaction temperature (factor X1, 260-340°C), reaction time (factor X2, 5-25min), catalyst dosage (factor X3, 2-18%) and biomass/water ratio (factor X4, 9-21%) for BO yield. It was found that reaction temperature, catalyst dosage and biomass/water ratio had more remarkable influence than reaction time on BO yield by analysis of variance. The predicted BO yield by the second order polynomial model was in good agreement with experimental results. A maximum BO yield of 38.72wt% was obtained at 304.8°C, 15.5min, 11.7% potassium carbonate as catalyst and 18% biomass (based on water). GC/MS analysis revealed that the major BO components were phenols and their derivatives, acids, aromatic hydrocarbon, ketones, N-contained compounds and alcohols, which makes it a promising material in the applications of either bio-fuel or as a phenol substitute in bio-phenolic resins.

Experimental Study of Subcritical Water Liquefaction of Biomass: Effects of Catalyst and biomass Species

In this work, hydrothermal liquefaction (HTL) of wood industry residues (wood, bark, sawdust) and macroalgae for producing biofuels has been investigated under subcritical water conditions (at temperature of 300 °C), with and without the presence of a catalyst. The effects of catalyst and biomass type (woody and non-woody) on the biomass conversion, bio-crude yield, and the qualities of products were studied. The results suggested that the addition of potassium carbonate as a catalyst showed a positive effect on bio-crude yield, especially for wood, where it was enhanced to 47.48 wt%. Macroalgae showed a higher biomass conversion and a lower bio-crude yield than other woody biomass investigated in the present study, irrespective of whether the catalyst was used. Meanwhile, the effect of catalyst on macroalgae was less significant than that of woody biomass. The heating values and thermal stability of all bio-crudes were analyzed. The results showed that the higher heating values (HHVs) were in the range of 24.15 to 31.79 MJ/kg, and they were enhanced in the presence of a catalyst, except for that of the macroalgae. The solid residues were characterized by heating value, SEM and FTIR. It was found that the addition of K2CO3 lowered the solids quality in terms of the heating values, while it did not have apparent effect on the functional groups of solid residues. SEM analysis of the raw biomass and solid residues revealed that the char formation for wood, sawdust and macroalgae had initially finished when they were treated in hot compressed water at 300 °C, while conversion of bark had not completed yet.Copyright