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Pyrolysis of azolla, sargassum tenerrimum and water hyacinth were carried out in a fixed-bed reactor at different temperatures in the range of 300-450°C in the presence of nitrogen (inert atmosphere). The objective of this study is to understand the effect of compositional changes of various aquatic biomass samples on product distribution and nature of products during slow pyrolysis. The maximum liquid product yield of azolla, sargassum tenerrimum and water hyacinth (38.5, 43.4 and 24.6wt.% respectively) obtained at 400, 450 and 400°C. Detailed analysis of the bio-oil and bio-char was investigated using 1H NMR, FT-IR, and XRD. The characterization of bio-oil showed a high percentage of aliphatic functional groups and presence of phenolic, ketones and nitrogen-containing group. The characterization results showed that the bio-oil obtained from azolla, sargassum tenerrimum and water hyacinth can be potentially valuable as a fuel and chemicals.

Research on biomass conversion has been gaining a lot of interest as biomass is renewable and sustainable in nature. Products from biomass can be obtained by different methods amongst which thermo-chemical route has a very high potential. Biomass is generally available in a localised manner in varying quantities and qualities throughout the year and hence, region specific technologies have to be developed considering the end user requirement. Pyrolysis is a very versatile technique with the above considerations. The process parameters can be tweaked to necessity to produce more bio-oil or bio-char. Thermogravimetric analysis is essential for understanding the decomposition behaviour of the feedstock before the lab scale pyrolysis is carried out. Pyrolysis using several regional feedstocks has been carried out under nitrogen and hydrogen atmosphere and different biomass feedstocks were also liquefied using sub/supercritical solvents. This review aims to provide a comparison of the results obtained using various processes. This helps in the decentralised processing of biomass (dry biomass using pyrolysis and wet biomass by hydrothermal liquefaction) to produce bio-crude which can be upgraded to produce fuels/chemicals/petrochemical feedstocks in an environmental friendly manner.

Pyrolysis of deodar has been carried out at 350 and 400 °C at 0.1, 1, 2 and 3 MPa hydrogen pressure. Pyrolysis under nitrogen atmosphere has been carried out at 300, 350, 400 and 450 °C. The favourable process conditions under hydrogen environment were found to be 400 °C and 2 MPa pressure and in case of nitrogen environment was found to be 350 °C. The products have been characterised using GC–MS, 1 H NMR, FT-IR and SEM. It has been observed that the bio-oil is rich in phenolic compounds under nitrogen and hydrogen atmospheres. Selectivity towards certain compounds such as catechol, vanillin and its derivatives etc. are high under hydrogen atmosphere. Deodar has undergone decomposition significantly which is evident by the absence of most functionality in bio-char and loss of crystallinity. The products formed under hydrogen and nitrogen environments are different from each other owing to the differences in reaction mechanism.

The thermal decomposition of the byproducts of the biodiesel process was studied by thermoanalytical methods. Deoiled algae cake and jatropha seed deoiled cake were pyrolyzed and the catalytic effects of silica supported iron catalysts (Fe/FSM-16 and Fe/SBA-15) and magnetite (Fe3O4) were tested. The evolution profiles of the decomposition products as well as the thermal stability of the samples were determined by thermogravimetry/mass spectrometry (TG/MS). The formation of the volatile products was monitored by pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). The composition and the amounts of the gaseous products changed significantly in the presence of the silica supported iron catalysts: the yield of hydrogen and carbon monoxide considerably increased above the decomposition temperature of 400 °C. Both silica supported iron catalysts had important effects on the yield of the products originating from carbohydrates and lignins. The formation of anhydrosugars and phenolic compounds was hindered...

Effect of different lignins were studied during slow pyrolysis. Maximum bio-oil yield of 31.2, 34.1, and 29.5wt.% was obtained at 350, 450 and 350°C for prot lignin, alkali lignin and dealkaline lignin respectively. Maximum yield of phenolic compounds 78%, 80% and 92% from prot lignin, alkali and dealkaline lignin at 350, 450 and 350°C. The differences in the pyrolysis products indicated the source of lignins such as soft and hard wood lignins. The biochar characterisation revealed that the various ether linkages were broken during pyrolysis and lignin was converted into monomeric substituted phenols. Bio-oil showed that the relative contents of each phenolic compound changes significantly with pyrolysis temperature and also the relative contents of each compound changes with different samples.

Slow pyrolysis of wheat straw and wheat husk has been carried out using microporous zeolite catalysts such as H-ZSM-5, mordenite and Y zeolite. Catalyst testing has been carried out at two positions in the reactor; one where it is mixed with the feed and other, by placing it in a catalyst boat to allow vapour phase contact. The thermal experiments have been carried out at 300, 350, 400 and 450 °C and the catalytic experiments have been carried out at 350 °C. Bio-oil yields are lower in all cases of catalytic pyrolysis of wheat straw compared to thermal run. With wheat husk, most cases of catalytic pyrolysis produced more bio-oil than thermal run. The bio-oil has been characterised using Gas Chromatography–Mass Spectrometry (GC–MS) and 1 H Nuclear Magnetic Resonance ( 1 H NMR) and bio-char using Fourier Transform-Infra Red spectroscopy (FT-IR), X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). It has been observed that the pyrolysis product profile and decomposition mechanism is dependent on the method of contact of catalyst.

Cotton production is accompanied by generation of huge amounts of residue all over the world. Slow pyrolysis of cotton residue has been carried out under nitrogen atmosphere at temperatures of 300, 350, 400 and 450 °C. Maximum bio-oil yield of 38 wt% was obtained at 400 °C. The organic fraction of bio-oil has been characterised using Fourier transform infrared spectroscopy (FT-IR), proton nuclear magnetic resonance (1H-NMR) and gas chromatography–mass spectrometry (GC-MS). Bio-oil contains phenolic compounds which are mostly derived from lignin fraction. The bio-char characterisation using FT-IR, powder X-ray diffraction (XRD) and scanning electron microscope (SEM) indicate the aromatic structure of bio-char. The gas characterisation indicates that decarboxylation and decarbonylation reactions have majorly occurred during pyrolysis.

Hydrothermal liquefaction of rice straw was performed at temperatures from 280 to 320 °C under different reaction environments viz., N 2 , O 2 and CO 2 . N 2 and CO 2 did not show any significant change in the product distribution, however, in case of liquefaction using O 2 , the bio-oil yield was very low. Maximum bio-oil yield (17 wt%) as well as conversion (78%) was observed in case of liquefaction using N 2 . TOC analysis indicated that the maximum organic carbon conversion (77%) was under N 2 environment. Ether soluble bio-oil obtained under O 2 environment showed higher aliphatic proton content than N 2 and CO 2 , whereas, aromatic proton content was higher in case of N 2 and CO 2 than O 2 . 1 H and 13 C NMR showed that bio-oil obtained at all the conditions was highly aliphatic and aromatic in nature. GC/MS showed that bio-oil (ether and acetone soluble) obtained under different reaction conditions was composed of phenol, guaiacol, catechol, syringol and their derivatives.

Hydrothermal liquefaction of rice straw has been carried out using various organic solvents (CH 3 OH, C 2 H 5 OH) at different temperatures (250, 280 and 300 °C) and residence times (15, 30 and 60 min) to understand the effect of solvent and various reaction parameters on product distribution. Maximum liquid product yield (47.52 wt%) was observed using ethanol at 300 °C and 15 min reaction time. FTIR and NMR ( 1 H and 13 C) of liquid product indicate that lignin in rice straw was converted to various monomeric phenols. GC–MS of the liquid product showed the presence of various phenol and guaiacol derivatives. Main compounds observed in liquid product were phenol, 4-ethylphenol, 4-ethyl-2-methoxyphenol (4-ethylguaiacol), 2,6-dimethoxyphenol (syringol), 2-isopropyl-5-methylphenol (thymol). Powder XRD and SEM of bio-residue showed that rice straw was decomposed to low molecular weight monomeric phenols.

Due to the increasing thrust on third generation biofuels, algal research has gained a lot of importance in the recent years. Effective utilization of algal biomass in a single step is necessary as it can produce fungible hydrocarbons in addition to a variety of valuable products. Hydrothermal liquefaction does not require the energy intensive drying steps and is an attractive approach for the conversion of algae which has high moisture content. The objective of this study is to understand the effect of compositional changes of macro algae samples Ulva fasciata (MA’UF), Enteromorpha sp. (MA’E) and Sargassum tenerrimum (MA’ST) on product distribution and nature of products. Various macro algae samples were converted to bio-oil by hydrothermal liquefaction in a batch reactor at 280 °C for 15 min with biomass:water ratio of 1:6. The liquefaction products were separated into ether soluble fraction (bio-oil1), water-soluble fraction, solid residue and gaseous fraction. Maximum conversion of 81% was observed with macro algae (MA) UF. The effect of varying feedstock compositions were reflected in the bio-oil and bio-residue yields. The maximum conversion and bio-oil yield was observed with MA’UF due to the presence of higher carbohydrate content than other feeds. FTIR and NMR spectra showed high percentage of aliphatic functional groups for all bio-oils.

Thermal and catalytic hydrothermal liquefaction of water hyacinth was performed at temperatures from 250 to 300 °C under various water hyacinth:H2O ratio of 1:3, 1:6 and 1:12. Reactions were also carried out under various residence times (15-60 min) as well as catalytic conditions (KOH and K2CO3). The use of alkaline catalysts significantly increased the bio-oil yield. Maximum bio-oil yield (23 wt%) comprising of bio-oil1 and bio-oil2 as well as conversion (89%) were observed with 1N KOH solution. (1)H NMR and (13)C NMR data showed that both bio-oil1 and bio-oil2 have high aliphatic carbon content. FTIR of bio-residue indicated that the usage of alkaline catalyst resulted in bio-residue samples with lesser oxygen functionality indicating that catalyst has a marked effect on nature of the bio-residue and helps to decompose biomass to a greater extent compared to thermal case.

Hydrothermal liquefaction is an attractive approach for the conversion of aquatic biomass like algae as it does not require the energy intensive drying steps. The objective of the study is to understand the effect of various solvents (H2O, CH3OH and C2H5OH) on product distribution and nature of products of hydrothermal liquefaction of macro algae Ulva fasciata (MAUF). Hydrothermal liquefaction of MAUF was performed using subcritical H2O (300 °C) as well as supercritical organic solvents CH3OH and C2H5OH (300 °C). The use of alcoholic solvents significantly increased the bio-oil yield. The bio-oil yield was 44% and 40% in case of liquefaction with CH3OH and C2H5OH respectively whereas the bio-oil yield was 11% with H2O. Use of alcoholic solvents converted the acids obtained in bio-oil to the corresponding methyl and ethyl esters. 1H NMR data showed that use of alcoholic solvents (C2H5OH and CH3OH) increased aliphatic content of bio-oil1 (ether/methanol/ethanol fraction). FTIR and SEM results showed the difference in the bio residue obtained using alcoholic solvents and H2O. The results showed that liquefaction with supercritical alcohols is an effective way to produce functional hydrocarbons for chemical feedstock.

The influence of various solvents (H2O, CH3OH, and C2H5OH) on product distribution and nature of products during hydrothermal liquefaction of sargassum tenerrimum algae has been examined. Hydrothermal liquefaction was performed using H2O (260, 280 and 300 °C) and organic solvents CH3OH and C2H5OH (280 °C) for 15 min. The use of organic solvents significantly increased the yield of bio-oil. In the case of liquefaction with CH3OH and C2H5OH, the bio-oil yield was 22.8 and 23.8 wt.% respectively whereas the bio-oil yield was 16.33 wt.% with H2O. GC–MS analysis of the liquid products indicated the presence of various organic compounds including aromatics, nitrogenated and oxygenated compounds and higher selectivity amount of ester compounds were observed in the presence of alcoholic solvents. NMR and FT-IR showed that present of solvents have an effect on the decomposition of sargassum tenerrimum algae.

The fundamental studies to understand the role of individual biomass components (cellulose and lignin) on the production of valuable hydrocarbons during hydrothermal liquefaction (HTL) is presented. Thermal and catalytic HTL of cellulose and lignin was performed at 280 °C under biomass:H2O ratio of 1:6 at 15 min residence time. The use of alkaline catalysts significantly increased both bio-oil yield and conversion for cellulose as well as lignin. Maximum bio-oil yield (28%) and conversion (90%) in case of cellulose was observed with KOH. Similarly in case of lignin maximum bio-oil yield (17 wt%) as well as conversion (72%) was observed with KOH. From the analysis of bio-oil and bio-residue, it was observed both cellulose and lignin have undergone hydrolytic cleavage during HTL to form low molecular weight liquid products. The FTIR and NMR (1H and 13C) of the bio-oil obtained from lignin indicated the presence of phenols and aromatic ethers.

Hydrothermal liquefaction of lignin was performed using methanol and ethanol at various temperatures (200, 250 and 280°C) and residence times of 15, 30 and 45min. Maximum liquid product yield (85%) was observed at 200°C and 15min residence time using methanol. Increase in temperature was seen to decrease the liquid products yield. With increase in residence time, liquid yields first increased and then decreased. FTIR and (1)H NMR showed the presence of substituted phenols and aromatic ethers in liquid products and breakage of β-O-4 or/and α-O-4 ether bonds present in lignin during hydrothermal liquefaction was confirmed through FTIR of bio-residue. In comparison to the existing literature information, higher lignin conversion to liquid products and maximum carbon conversion (72%) was achieved in this study.

Biomass is a promising feedstock for the production of valuable oxygenated hydrocarbons due to presence of wide range of functionalities. Hydrothermal liquefaction is an attractive approach for the conversion of lignocellulosic biomass as it does not require any drying. The objective of this study is to carry out hydrothermal liquefaction (280 °C for 15 min) of forest (pine wood, deodar) and agricultural (wheat straw, sugarcane bagasse) biomass under non-catalytic and catalytic (KOH, K2CO3) conditions. The analysis of solid residue and bio-oils was carried out to understand the differences in composition with respect to feedstock. Agricultural biomass showed higher conversion under thermal and catalytic conditions compared to forest biomass. K2CO3 showed higher catalytic activity in terms of both bio-oil yield as well as conversion for agricultural (wheat straw and sugarcane bagasse) biomass compared to forest (pine wood and deodar) biomass. Sugarcane bagasse showed the highest conversion (95 %) among the four samples investigated. The compositions of bio-oils from forest biomass residue contained both phenolic compounds and furans. FTIR and Powder XRD analysis of feedstock as well as solid residue showed that the peaks due to cellulose, hemicellulose and lignin became weak in solid residue samples.

With growing concerns of fossil fuel resources availability and the volatility of crude oil price, it is becoming imperative day by day to utilize the renewable sources of energy in a sustainable, environment friendly and energy efficient manner. India is the world’s second largest producer of cotton after China. India also has several agricultural and forest residues, and cotton residue is one of the most abundant agricultural residues after rice and wheat residues. The hydropyrolysis of cotton residues has been carried out at various pressures (1, 20 and 40 bar) and temperatures (300, 350, 400 and 450 °C). The effects of temperature and pressure have been studied to understand their yield patterns, and it has been observed that 20 bar pressure and 400 °C are the optimum conditions. The thermogravimetric analysis shows that cotton residue has two significant decomposition temperatures. The SEM, XRD patterns and FT-IR spectra clearly indicate the decomposition of the macromolecular structure of the cotton residue and formation of low molecular weight hydrocarbons suitable for various applications.

Pyrolysis studies on conventional biomass were carried out in fixed bed reactor at different temperatures 300, 350, 400 and 450°C. Agricultural residues such as corn cob, wheat straw, rice straw and rice husk showed that the optimum temperatures for these residues are 450, 400, 400 and 450°C respectively. The maximum bio-oil yield in case of corn cob, wheat straw, rice straw and rice husk are 47.3, 36.7, 28.4 and 38.1wt% respectively. The effects of pyrolysis temperature and biomass type on the yield and composition of pyrolysis products were investigated. All bio-oils contents were mainly composed of oxygenated hydrocarbons. The higher area percentages of phenolic compounds were observed in the corn cob bio-oil than other bio-oils. From FT-IR and 1H NMR spectra showed a high percentage of aliphatic functional groups for all bio-oils and distribution of products is different due to differences in the composition of agricultural biomass.

Catalytic hydrothermal upgradation of wheat husk was performed at 280 °C for 15 min in the presence of alkaline catalysts (KOH and K2CO3). The effect of alkaline catalysts on the yield of bio-oil products and composition of bio-oils obtained were discussed. Total bio-oil yield (31%) comprising of bio-oil1 (ether fraction) and bio-oil2 (acetone fraction) was maximum with K2CO3 solution. Powder XRD (X-ray diffraction) analysis of wheat husk as well as bio-residue samples show that the peaks due to cellulose, hemicellulose and lignin become weak in bio-residue samples which suggest that these components have undergone hydrolytic cleavage/decomposition. The FTIR spectra of bio-oils indicate that the lignin in the wheat husk samples was decomposed to low molecular weight phenolic compounds. 1H Nuclear Magnetic Resonance (NMR) spectrum of bio-oil1 shows more than 50% of the protons resonate in the up field region from 0.5 ppm to 3.0 ppm.

Background The quest for sustainable production of renewable and cheap biofuels has triggered an intensive search for domestication of the next generation of bioenergy crops. Aquatic plants which can rapidly colonize wetlands are attracting attention because of their ability to grow in wastewaters and produce large amounts of biomass. Representatives of Azolla species are some of the fastest growing plants, producing substantial biomass when growing in contaminated water and natural ecosystems. Together with their evolutional symbiont, the cyanobacterium Anabaena azollae, Azolla biomass has a unique chemical composition accumulating in each leaf including three major types of bioenergy molecules: cellulose/hemicellulose, starch and lipids, resembling combinations of terrestrial bioenergy crops and microalgae. Results The growth of Azolla filiculoides in synthetic wastewater led up to 25, 69, 24 and 40 % reduction of NH4–N, NO3–N, PO4–P and selenium, respectively, after 5 days of treatment. This led to a 2.6-fold reduction in toxicity of the treated wastewater to shrimps, common inhabitants of wetlands. Two Azolla species, Azolla filiculoides and Azolla pinnata, were used as feedstock for the production of a range of functional hydrocarbons through hydrothermal liquefaction, bio-hydrogen and bio-ethanol. Given the high annual productivity of Azolla, hydrothermal liquefaction can lead to the theoretical production of 20.2 t/ha-year of bio-oil and 48 t/ha-year of bio-char. The ethanol production from Azolla filiculoides, 11.7 × 103 L/ha-year, is close to that from corn stover (13.3 × 103 L/ha-year), but higher than from miscanthus (2.3 × 103 L/ha-year) and woody plants, such as willow (0.3 × 103 L/ha-year) and poplar (1.3 × 103 L/ha-year). With a high C/N ratio, fermentation of Azolla biomass generates 2.2 mol/mol glucose/xylose of hydrogen, making this species a competitive feedstock for hydrogen production compared with other bioenergy crops. Conclusions The high productivity, the ability to grow on wastewaters and unique chemical composition make Azolla species the most attractive, sustainable and universal feedstock for low cost, low energy demanding, near zero maintenance system for the production of a wide spectrum of renewable biofuels. Electronic supplementary material The online version of this article (doi:10.1186/s13068-016-0628-5) contains supplementary material, which is available to authorized users.

Additional file 6: Table S4. Proximate and ultimate analysis of A. filiculoides biomass, (% DW).

An amorphous carbon based catalyst was prepared by sulfonation of the bio-char obtained from fast pyrolysis (N2 atm; ≈550 °C) of biomass. The sulfonated carbon catalyst contained high acidity of 6.28 mmol/g as determined by temperature programmed desorption of ammonia of sulfonated carbon catalyst and exhibited high catalytic performance for the hydrolysis of cellulose. Amorphous carbon based catalyst containing -SO3H groups was successfully tested and the complete conversion of cellulose in methanol at moderate temperatures with high yields ca. ⩾90% of α, β-methyl glucosides in short reaction times was achieved. The methyl glucosides formed in methanol are more stable for further conversion than the products formed in water. The carbon catalyst was demonstrated to be stable for five cycles with slight loss in catalytic activity. The utilization of bio-char as a sulfonated carbon catalyst provides a green and efficient process for cellulose conversion.

The increasing concerns over the depletion of fossil resources and its associated geo-political issues have driven the entire world to move toward sustainable forms of energy. Pretreatment is the first step in any biochemical conversion process for the production of valuable fuels/chemicals from lignocellulosic biomass to eliminate the lignin and produce fermentable sugars by hydrolysis. Conventional techniques have several limitations which can be addressed by using them in tandem with non-conventional methods for biomass pretreatment. Electron beam and γ (gamma)-irradiation, microwave and ultrasound energies have certain advantages over conventional source of energy and there is an opportunity that these energies can be exploited for biomass pretreatment.

The transformation to a sustainable and renewable hydrocarbon industry is possible only by the use of biomass as it is the only source of organic carbon. Lignocellulosic biomass can be used to produce fuels, chemicals, and energy in an integrated biorefinery system. Catalysts play a very important role in valorizing the biomass as a whole or its streams to make its use environment friendly and economically viable. Thermochemical biorefinery uses a wide range of catalysts from old natural zeolites to recent hierarchical zeolites in its conversion processes. This chapter aims to educate the reader on the various properties of catalysts that are necessary for a particular process to produce the required products. The various catalysts that have been used to date for several thermochemical methods of conversion have also been explained.

Thermochemical methods are efficient routes for conversion of biomass. Among them, hydrothermal liquefaction is the most promising method as it can convert feedstocks (lignocellulosic biomass and algae) with very high moisture content into bio-oil and platform chemicals without energy-intensive pretreatment. In order to better understand the underlying reaction mechanisms and major experimental variables during hydrothermal liquefaction, this chapter describes the basic understanding of physical and chemical properties of subcritical water, hydrothermal liquefaction studies of individual biomass components as well as whole biomass, and their reaction paths and products. The role of process variables, including biomass composition, temperature, residence times, heating rate, particles size, solvent, catalyst, reactor configuration, and so on, that are important for the bio-oil yield and product quality is discussed in the chapter.

Gasification has been considered as a potential thermo-chemical method of conversion to effectively utilize the carbon (organic content) present in the feedstock. Preparation and handling methods of some of the potential feedstocks (i.e., coal, petroleum residue, biomass, and municipal solid waste (MSW) to produce the synthetic gas) for various applications are discussed. The pre-treatment process for feedstock constitutes the steps that must be imposed on the raw material in preparation for use in a gasification reactor. The properties of fuel that influence the gasification are energy content, moisture content, particle size and distribution, form of the fuel, bulk density of the fuel, volatile matter content, ash content, and composition and reactivity of the fuel.

The increasing concern over availability and cost of fossil fuel resources, coupled with the effects of climate change, has fueled the shift toward usage of renewable and sustainable sources of energy. Biomass, a renewable source of carbon, can be converted by various methods to produce required hydrocarbons in the form of fuel, chemicals, or petrochemicals. Thermochemical methods have several advantages the biochemical methods of conversion in terms of reaction time, feedstock, and flexibility. A thermochemical biorefinery will have one or more thermochemical methods of conversion integrated to produce valuable hydrocarbons/energy. Such systems have high energy efficiency and increase carbon utilization to value-added products. The chapter discusses the concept of thermochemical biorefineries with an aim to explain their significance in reducing dependence on fossil resources by effectively making use of the biomass available.

The inevitability of transition toward a biobased economy is fueled by the problems related to fossil fuel utilization such as climate change due to greenhouse gas emissions. Lignin is a renewable feedstock that can be used to produce hydrocarbons in a sustainable manner. Lignin is obtained as a by-product of several conversion processes when it is isolated from the lignocellulosic biomass matrix. It is the major fraction that contributes to the organic hydrocarbons such as aromatics, phenolics, and platform chemicals that are presently produced from fossil resources. Lignin exhibits different physicochemical characteristics depending on the isolation process used. Lignin, over the years, has been converted to various value-added hydrocarbons (bioenergy, biofuels, biochemicals, and petrochemical feedstocks) using several thermochemical methods of conversion such as pyrolysis, gasification, and liquefaction. Challenges in the valorization of lignin include understanding the effect of source on the lignin structure, development of novel catalysts for conversion, increased selectivity and yield from processes, and effective separation processes.

Pyrolysis of rice straw has been carried out under hydrogen atmosphere at 300, 350, 400 and 450 °C and pressures of 1, 10, 20, 30 and 40 bar and in nitrogen atmosphere, experiments have been carried out at the same temperatures. It has been observed that the optimum process conditions for hydropyrolysis are 400 °C and 30 bar pressure and for slow pyrolysis, the optimum temperature is 400 °C. The bio-oil has been characterised using GC-MS, (1)H NMR and FT-IR and bio-char using FT-IR, SEM and XRD. The bio-oil yield under hydrogen pressure was observed to be 12.8 wt.% (400 °C and 30 bar) and yield under nitrogen atmosphere was found to be 31 wt.% (400 °C). From the product characterisation, it was found that the distribution of products is different for hydrogen and nitrogen environments due to differences in the decomposition reaction mechanism.

Energy security, increasing oil prices, fossil resource depletion, and climate change are some of the greatest challenges faced by mankind at present. Third-generation biofuel feedstock and micro-and macroalgae have many advantages over the first and second generations of biofuels. In addition, defatted algae can also be used as a feedstock for production of hydrocarbons. Thermochemical methods are more efficient than any other routes for conversion of algae. Among thermochemical methods, hydrothermal upgradation is the most promising because it can process feedstock such as algae with very high moisture content. Various reactors, catalysts, and operating parameters have been tested to valorize algae by liquefaction and gasification, and promising results have been obtained. Breakthroughs in reactors and/or catalysts for hydrothermal upgradation, proper utilization of the side products obtained, and integration with various other methods to extract high-value hydrocarbons/products from algae would help make algal biorefinery economical and sustainable.

Increase in fossil fuel prices, greenhouse gas emissions, climate variations, and global warming are the main reasons leading to hydrogen technology. Hydrogen produced from biomass is considered as an environmentally friendly and sustainable system. This chapter basically focuses the different thermochemical processes (gasification and pyrolysis) used to produce hydrogen, which are economically viable approaches and provide the highest potential to become competitive on a large-scale in near future. The advancement in the technology ensures high volume of production. The variation in the hydrogen is due to difference in different operating parameters and feedstock characteristics. The future developments of these technologies including innovations regarding hydrogen production and storage, transport, and effective utilization reduces the dependence on fossil fuels, and green hydrogen will dominate over the traditional energy sources. So, attention needs to pay towards the standardization of the operating parameters, sustainability issues regarding the production of biomass, and logistics of biohydrogen cycle production.

Thermal decomposition and kinetics behaviour of the de-oiled seed cake of African star apple (Chrosophyllum albidum) has been investigated using thermogravimetry under the nitrogen atmosphere from ambient temperature to 900 °C. The thermogravimetric data for the cake decomposition at six different heating rates (5, 10, 15, 20, 30 and 40 °C/min) were used to evaluate the kinetic decomposition of the cake using Friedman (FD), Kissinger-Akahira-Sunose (KAS) and Flynn-Wall-Ozawa (FWO) models. Thermal decomposition of the cake showed thermograms indicating dehydration and devolitilization stages (200–400 °C). The maximum temperature for the decomposition of the cake (Tmax) increases from 289.42–335.96 °C with increase in heating rates. The average apparent activation energy (Ea) values of 153.15, 145.14 and 147.15 kJ/mol were calculated using Friedman, Kissinger-Akahira-Sunose, and Flynn-Wall-Ozawa models respectively. The extent of mass conversion (α) shows dependence on apparent activation Ea values which is an evidence of multi-step decomposition kinetic. The thermal profile and kinetic data obtained could be helpful in evaluating the thermal stability of the cake as well as modeling, designing and developing a thermo-chemical system for the conversion of the cake to fuel.

Publisher Summary The base of thermochemical conversion is the pyrolysis process in most cases. Combustion is the sequence of exothermic chemical reactions between a fuel and an oxidant accompanied by the production of heat and conversion of chemical species. During the combustion of lignocellulosic biomass, the heat is generated due to oxidation reaction, where carbon, hydrogen, oxygen, combustible sulfur, and nitrogen contained in biomass react with air or oxygen. By far the most common means of converting biomass to usable heat energy is through straightforward combustion, and this account for around 90% of all energy attained from biomass. It contributes over 97% of bioenergy production in the world. Combustion is a proven low-cost process, highly reliable technology, relatively well understood and commercially available. There are three main stages that occur during biomass combustion: drying, pyrolysis and reduction, and combustion of volatile gases and solid char. Typically, the biomass contains high moisture and high oxygen content, which causes to have low heating values for biomass. The high moisture content is one of the most significant disadvantage features. Although the combustion reactions are exothermic, the evaporation of water is endothermic. As the moisture content increases, both the higher heating value (HHV) and lower heating value (LHV) decrease. HHV and LHV are used to describe the heat production of a unit quantity of fuel during its complete combustion. In determining the HHV and LHV values of a fuel, the liquid and vapor phases of water are selected as the reference states, respectively. The negative linear relationship exists between the moisture content and the heating value. Fouling (alkali and other elements) and corrosion (alkali, sulfur, chlorine, etc.) of the combustor are typical issues associated with biomass combustion. These are considered to be detrimental because of the resulting reduction in heat transfer in the combustor.

It has been shown that approximately 1 in 250–300 individuals of European descent are homozygous for the hemochromatosis gene, 1 thus identifying hereditary hemochromatosis as one of the most common inherited disorders. In both hereditary hemochromatosis and in the various forms of secondary iron overload, there is a pathologic expansion of body iron stores, due mainly to an increase in absorption of dietary iron. 2,3 Cellular uptake of circulating excess iron results in increased formation of ferritin and hemosiderin found in highest concentration in the parenchymal tissues of several organs (e.g., liver, heart, pancreas). At high tissue iron levels, fibrogenesis occurs in these organs accompanied by functional insufficiency. 2-6 Although best studied in the liver, pathological studies support this association in other organs affected in iron overload as well. Thus, clinical evidence for toxicity and fibrosis in hepatic iron overload has been provided by studies of patients with hereditary hemochromatosis, 4,5 African iron overload, 7 and secondary iron overload due to s-thalassemia8 in which a correlation between hepatic iron concentration and the occurrence of liver damage has been demonstrated or in which therapeutic reduction of hepatic iron by either phlebotomy or chelation therapy has resulted in clinical improvement. Despite clinical evidence for the cellular and tissue toxicity of excess iron, the specific pathophysiologic mechanisms of tissue injury and fibrogenesis in chronic iron overload are still poorly understood.