Hydrothermal Liquefaction of Biomass as One of the Most Promising Alternatives for the Synthesis of Advanced Liquid Biofuels: A Review

The use of biofuels offers advantages over existing fuels because they come from renewable sources, they are biodegradable, their storage and transport are safer, and their emissions into the atmosphere are lower. Biomass is one of the most promising sustainable energy sources with a wide variety of organic materials as raw material. Chemical, biochemical, and thermochemical methods have been proposed to obtain biofuels from raw materials from biomass. In recent years, a thermochemical method that has generated great interest is hydrothermal liquefaction. In this paper, a brief review of the main sources for liquid biofuels and the synthesis processes is presented, with special emphasis on the production of biofuels using hydrothermal liquefaction by using waste generated by human activity as raw material.

State-of-the-Art Char Production with a Focus on Bark Feedstocks: Processes, Design, and Applications

In recent years, there has been a surge of interest in char production from lignocellulosic biomass due to the fact of char’s interesting technological properties. Global char production in 2019 reached 53.6 million tons. Barks are among the most important and understudied lignocellulosic feedstocks that have a large potential for exploitation, given bark global production which is estimated to be as high as 400 million cubic meters per year. Chars can be produced from barks; however, in order to obtain the desired char yields and for simulation of the pyrolysis process, it is important to understand the differences between barks and woods and other lignocellulosic materials in addition to selecting a proper thermochemical method for bark-based char production. In this state-of-the-art review, after analyzing the main char production methods, barks were characterized for their chemical composition and compared with other important lignocellulosic materials. Following these steps, previous bark-based char production studies were analyzed, and different barks and process types were evaluated for the first time to guide future char production process designs based on bark feedstock. The dry and wet pyrolysis and gasification results of barks revealed that application of different particle sizes, heating rates, and solid residence times resulted in highly variable char yields between the temperature range of 220 °C and 600 °C. Bark-based char production should be primarily performed via a slow pyrolysis route, considering the superior surface properties of slow pyrolysis chars.

Concept of Biohydrogen Production by Agricultural Enterprises

Biohydrogen production in agricultural enterprises is an urgent matter. It is appropriate to utilize two methods of biohydrogen production: a thermochemical method – from crop-based biomass and anaerobic digestion (fermentation) method – from animal-based biomass.. It is appropriate to use gasifiers for the thermochemical method and biore-actors for fermentation method. The theoretical potential of biohydrogen was established with due regard to the amount of biomass which is necessary for utilization in livestock agriculture, for fields fertilization as well as with the consideration of the coefficients of concordance with hydrogen equivalent and loss factor under biohydrogen production. The theoretical potential of biohydrogen from crop-based biomass in Ukraine amounts to 77 billion m3, during the period of three years (on average 25.6 billion m3 per year).

Fluid inclusions, H-O-S isotopic characteristics and genesis of the Chambishi copper deposit, Zambia

In this paper, fluid inclusions and H-O-S isotope geochemistry of the Chambishi copper deposit in Zambia are studied. According to the fluid inclusion in quartz and H-O-S isotope characteristics, it is concluded that ore-forming hydrothermal fluid is derived from mantle source and crust source magma mingling, the cause of copper precipitation, sedimentary type sulfur layered mineralization are mainly from diagenetic sulfides and seawater sulfate. Sulfate is mainly reduced by thermochemical method. The hydrothermal vein mineralization of Chambishi copper deposit is closely related to the magmatic activity in the middle Neoproterozoic, and the sedimentary stratified mineralization is mainly related to the large-scale orogeny and regional metamorphism in the late Neoproterozoic.

Effect of Torrefaction Temperature, Residence Time and Particle Size on the Properties of Torrefied Food Waste

Municipal solid waste (MSW) in Malaysia mainly consists of food waste. As food waste is of organic compounds, its improper management may cause serious environmental issues, as it may produce greenhouse gases and polluting leachate. Alternative management of the food waste is through its utilization. However, the main issue in the utilization of food waste is its heterogeneity, whereby the diversified cooking methods, as well as food origin, emanates different characteristics. Hence, food waste needs to be pre-treated through the torrefaction process, which is a thermochemical method that converts it to biochar at a temperature between 200–300 °C in an inert environment. The main aim of this work is to evaluate the feasibility of food waste as a potential source of energy through the torrefaction process. The torrefaction of food waste was conducted in a vertical tubular reactor under an inert atmosphere. The results obtained from this study showed that as torrefaction temperature became more severe, the produced torrefied solid is more energy-dense, with apparent higher fixed carbon content and improved heating values. These findings imply that food waste may be able to be utilized as a solid biofuel, with fuel properties comparable to conventional fuels.

Integrated Production of Biofuels and Succinic Acid from Biomass after Thermochemical Pretreatments

The aim of this study was to develop an effective thermochemical method for treatment of industrial hemp, in order to increase its bioconversion to biofuels and bio-products. Industrial hemp was subjected to various thermochemical pretreatments using: alkaline (3 % NaOH), oxidative (3 % H2O2 at pH 11.5) and glycerol-based methods (70-90 % of glycerol, 1-3 % NaOH), prior to enzymatic hydrolysis with Cellic® CTec2/Cellic® HTec2 (15 FPU∙g−1 glucan). Innovative pretreatment with glycerol fraction (80 % glycerol content, 2 % NaOH, 12.5 % biomass loading) showed to be superior over commonly used alkaline and oxidative methods with respect to by-products generation and sugar losses. Integrated process of ethanol production from enriched cellulose fraction (172 kg EtOH∙Mg−1 of dry hemp) and succinic production from xylose-rich residue after ethanol fermentation (59 kg∙Mg−1 of dry hemp) allowed to convert about 97 % of sugars released (glucose and xylose) during enzymatic hydrolysis of pre-treated biomass. The present study showed that it is possible to replace 50 % of the costly yeast extract, used during succinic fermentation as nitrogen source, by alternative nitrogen source (rapeseed cakes) without significant deterioration of succinic yield. Pretreatment liquor after lignin precipitation (52 kg∙Mg−1 of biomass treated) exhibited a high biodegradability (92 %) and allowed to produce 420 m3 CH4/Mg VS). Results obtained in this study clearly document the possibility of biofuels (bioethanol, biogas) and bio-chemicals production from industrial hemp, in a biorefinery approach.