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The hydrothermal carbonization (HTC) technique and subsequent pyrolysis were applied. Herein, two different types of biobased feedstocks, sucrose (Suc) and Miscanthus (Mis), were chosen. Urea served as N precursor for the in situ doping. HTC of Suc and Mis with urea leads to N‐doped hydrochars (N‐HCs). Suc and Mis decompose in different, complex degradation pathways, which leads to the emergence of N‐HCs consisting of distinct ratios of N‐containing primary chars (N‐PCs) and secondary chars (N‐SCs). After pyrolysis, maximum N contents of 5.6 wt % and 4.8 wt % of the N‐doped pyrolyzed hydrochar (N‐PHC) electrodes from Suc and Mis, respectively were reached. The role of PC and SC formation on the impact of N‐doping in the context of physicochemical properties of the N‐PHCs was compared with each other. In this study, they were tested with respect to the influence of N‐PCs and N‐SCs on their electrochemical performance in energy storage application. It turned out that the electrical conductivity (EC) and specific capacitances increased. Highest EC value of 129.1 S ⋅ cm−1 was obtained with N‐PHC based on Suc. Simultaneously, enhanced average specific capacitances of 47.0 F ⋅ g−1 at 5 mV ⋅ s−1 and 3.5 F ⋅ g−1 at 100 mV ⋅ s−1 are ascertained with N‐PHCs from Suc and Mis, respectively. [ABSTRACT FROM AUTHOR]

There are increasing demands for syngas production. Fossil‐based fuels are expensive and environmentally unfriendly. Affordable, sustainable, and environmentally healthy alternatives and sustainable fuel sources are needed. This study focused on producing tor‐chars from two different tropical biomasses (from Nigeria, West Africa), which were torrefied and characterized to improve their properties for potential use as sustainable feedstocks in an entrained flow gasifier for syngas production. Torrefaction temperatures of 230, 240, 250, and 270 °C and residence times of 30 and 60 min were used to torrefy sundried sorghum straw (SS) and millet straw (MS) at particle size ≤5 mm. The properties of torrefied MS and SS improved significantly due to torrefaction. The optimum conditions for pretreatment of sundried MS and SS were 240 °C and 60 min, at which increased energy density significantly compensated for the severe mass loss and significant degradation of hemicellulose and cellulose. Under these conditions, the respective mass and energy yields were 53 wt% and 75% for millet straw and 49 wt% and 75% for sorghum straw. The O:C atomic ratio decreased to 0.3 in MS tor‐chars and 0.2 in SS tor‐chars resulting in higher heating values of 25 MJ kg−1 and 27 MJ kg−1, respectively. Under optimum conditions, the ash content increased by 107% to be approximately 7 wt% in MS tor‐char, and by 118% to about 7 wt% in SS tor‐char. These properties are promising for potential feedstocks in co‐firing plants or gasification systems. © 2022 The Authors. Biofuels, Bioproducts and Biorefining published by Society of Industrial Chemistry and John Wiley & Sons Ltd. [ABSTRACT FROM AUTHOR]

Hydrothermal carbonization (HTC) of fructose and urea containing solutions was conducted at 180 °C to study the influence of nitrogen‐containing compounds on the conversion process and HTC products properties. The concentration of fructose was fixed, while the concentration of urea was gradually increased to study its influence on the formation of nitrogen‐containing hydrochar (N−HC). The degradation of urea has an important influence on the HTC of fructose. The Maillard reaction (MR) promotes the formation of N−HC in acidic conditions. However, in alkaline conditions, MR promotes the formation of bio‐oil at the expense of N−HC. Alkaline conditions reduce N−HC yield by catalyzing fragmentation reactions of fructose and by promoting the isomerization of fructose to glucose. The results showed that adjusting the concentration of nitrogen‐containing compounds or the pH value of the reaction environment is important to force the reaction toward the formation of N−HC or N‐bio‐oil. [ABSTRACT FROM AUTHOR]