Catalyzed hydrothermal carbonization (CHTC) was used to produce hydrochar biofuel from wood chips at 240 °C in 1 h batches that included recycling of the process liquid. Infrared spectra showed changes in the chemical structure consistent with dehydration and decarboxylation. The CHTC hydrochar had higher heating values (HHV) of 28.3 MJ/kg, energy yield of 64%, and hydrogen-to-carbon (H/C) and oxygen-to-carbon (O/C) ratios similar to those of coal. The same process without the catalyst (HTC) produced a hydrochar with HHV of 27 MJ/kg, energy yield of 57%, and H/C and O/C ratios similar to those of lignite. Partial recycling of the CHTC process liquid resulted in a 5% increase in the energy yield; elemental composition, HHV, and scanning electron microscopic images of the CHTC hydrochar for different recycles were indistinguishable. Densified CHTC hydrochar pellets were 97% durable and hydrophobic when compared with wood pellets and torrefied-wood pellets, which was shown by water ingress measurements using an electrochemical cell with pellet electrodes. The CHTC process with recycling has the potential to provide a green hydrochar biofuel with excellent handling, storage, and transportation properties, that could be a suitable direct replacement for coal.

The purpose of this study is to optimize the processing conditions (temperature, pressure, process time, yield rate) for the conversion of biomass to a high-energy density biofuel. The hydrothermal polymerization (HTP) catalytic process has been developed for production of biofuel via hydrothermal processing using an acid-based catalyst. This study has shown that the HTP catalytic process for a reference feedstock lowered the temperature by 10 to 40 • C, reduced the pressure requirement by 1 to 2 MPa, increased the rate of yield by 22%, and shortened the total processing time by up to 3 h when compared to the conventional hydrothermal carbonization (HTC) process. FTIR spectrum analysis of the HTP catalytic biofuel has shown that lignin in the biomass is preserved, while the pure HTC process destroyed the lignin in the biomass. GC/MS analysis of the process liquid determined the changes of the intermediate soluble components as a function of time. By measuring the 2,5-hydroxymethyl furfuralde concentration in solution, an endpoint determination could be made. This study also determined the approximate analysis of the HTP biofuel from various organic wastes such as cotton, cow manure, wood waste, paper waste, sugarcane bagasse waste, and food waste.

Catalyzed hydrothermal carbonization of woody biomass produces hydrochar and valuable aqueous products (VAPs) that could potentially be harvested to facilitate commercialization of the process. Acetic acid, formic acid, glycolic acid, levulinic acid, 5-hydroxymethyl-2-furfural, and furfural are potential VAPs found in the process liquid. Recycling the process liquid increased the yields of VAPs not associated with hydrochar production, except for formic acid. Yields increased with the liquid:biomass ratio peaking at 10:1 for all but levulinic acid. The higher heating value of the hydrochar, 27.6 ± 0.3 MJ/kg, was not affected by recycling or the liquid:biomass ratio. The energy yield of catalyzed hydrothermal carbonization increased from 72 to 80% when the process liquid was recycled. Energy yields for hydrochar production increased from 63 to 74% when the liquid:biomass ratio was decreased from 12:1 to 3:1.

A renewable, green activated carbon made from sucrose (sugar) was compared with traditional bituminous coal-based granular activated carbon (GAC). Single and multi-component competitive adsorption of nitrate and phosphate from water was investigated. Langmuir and Freundlich isotherm models were fitted to data obtained from the nitrate and phosphate adsorption experiments. Nitrate adsorption fits closely to either Freundlich or Langmuir model for sucrose activated carbon (SAC) and GAC with a Langmuir adsorption capacity of 7.98 and 6.38 mg/g, respectively. However, phosphate adsorption on SAC and GAC demonstrated a selective fit with the Langmuir model with an adsorption capacity of 1.71 and 2.07 mg/g, respectively. Kinetic analysis demonstrated that adsorption of nitrate and phosphate follow pseudo-second-order kinetics with rate constant values of 0.061 and 0.063 g/(mg h), respectively. Competitive studies between nitrate and phosphate were demonstrated in preferential nitrate removal with GAC and preferential phosphate removal with SAC. Furthermore, nitrate and phosphate removals decreased from approximately 75% removal to 35% removal when subject to multi-component solutions and highlight the need for adsorption analysis in complex systems. Overall, SAC proved to be competitive with GAC in the removal of inorganic contaminants and may represent a green alternative to coal-based activated carbon.

Through the previous study a hydrothermal polymerization (HTP)—a catalytic methodology for treating various biomass and organic wastes—has been developed on a lab scale with a 1 L reactor and the results published. The research work described herein aims to ensure that the catalytic process is scalable for pilot and even commercial scale plants. A 1700 L binary reactor system has been built and the assumptions of a commercial scale plant that would have 10,000 to 20,000 L pressure vessels tested. The HTP catalytic biofuel process converts mono- and polysaccharides into a solid polymer fuel that is based on a furfuraldehyde ring system. The calorific value of the material obtained from the pilot plant is on the order of 27 MJ/kg and the material typically has low ash and fixed carbon content order of 48% which are about same as the lab results for various wood biomass feedstocks. Though a 1700 times scale up binary reactor system the scalability of the HTP catalytic methodology has been confirmed and the mass and energy balance of the binary reactor identified in order to provide fundamental data for commercial scale establishment in future.