Fuel Characteristics and Phytotoxicity Assay of Biochar Derived from Rose Pruning Waste.

The aim of this study was the characterization and evaluation of applicability as a soil amendment of biochar derived from rose pruning waste at different pyrolysis temperatures (200-500 °C) and process durations (20-60 min). The biochar properties were compared to the raw material. The biochars produced at 300 °C for 40 and 60 min demonstrated the best fuel properties. These variants showed high energy gain rates (77.6 ± 1.5% and 74.8 ± 1.5%, respectively), energy densification ratios (1.35 ± 0.00 and 1.37 ± 0.00, respectively), high heating values (24,720 ± 267 J × g-1 and 25,113 ± 731 J × g-1, respectively), and relative low ash contents (5.9 ± 0.5% and 7.1 ± 0.3%, respectively). Regarding fertilizer properties, such as pH value, ash content, heavy metal content, and pollutant elution, the biochars showed better qualities than the raw material. All tested biochar did not exceed the permissible values for heavy metals, including Cr, Cd, Ni, and Pb. The most optimal properties for soil amendments were noted for biochar variants of 400 °C for 40 min, 450 °C for 20 min, and 500 °C for 20 min. Generally, biochars produced at temperatures ≥400 °C did not inhibit root elongation, except for the material produced at 450 °C for 60 min (4.08 ± 23.34%). Biochars obtained at ≥300 °C showed a positive impact on seed germination (86.67 ± 18.48-100 ± 24.14%).

Study on the Effect of Hydrothermal Carbonization Parameters on Fuel Properties of Sewage Sludge Hydrochar.

In the wake of economic and population growth, increased wastewater production poses a challenge related to sewage sludge treatment, which is problematic given its high moisture content, amount, and hazardous characteristics. This study focuses on the hydrothermal carbonization of sewage sludge to produce carbonous material-hydrochar, which may be an alternative to fossil fuels. The effect of process parameters, namely, temperature (180, 240, 300 °C) and duration time (30, 90, 180 min), on hydrochar properties (proximate and ultimate analysis, heating values) and process performance were studied. Obtained results indicate and confirm that hydrothermal carbonization, especially temperature increase, improves the fuel properties of carbonized sewage sludge. The highest low heating value was obtained for hydrochar derived at 300 °C in 180 min (~23 MJ × kg-1). The highest energy gain was noted for hydrochar derived at 240 °C in 180 min (~23%). As well as relatively high mass and energy yield in comparison to other hydrochars, these parameters are considered the most favorable for sewage sludge hydrothermal carbonization. However, high energy consumption (over 1300 kJ × g-1) suggests that more research on the process's economical efficacy is required.

Influence of Pre-Incubation of Inoculum with Biochar on Anaerobic Digestion Performance.

The application of biochar as an additive to enhance the anaerobic digestion (AD) of biomass has been extensively studied from various perspectives. This study reported, for the first time, the influence of biochar incubation in the inoculum on the anaerobic fermentation of glucose in a batch-type reactor over 20 days. Three groups of inoculum with the same characteristics were pre-mixed once with biochar for different durations: 21 days (D21), 10 days (D10), and 0 days (D0). The BC was mixed in the inoculum at a concentration of 8.0 g/L. The proportion of the inoculum and substrate was adjusted to an inoculum-to-substrate ratio of 2.0 based on the volatile solids. The results of the experiment revealed that D21 had the highest cumulative methane yield, of 348.98 mL, compared to 322.66, 290.05, and 25.15 mL obtained from D10, D0, and the control, respectively. Three models-modified Gompertz, first-order, and Autoregressive Integrated Moving Average (ARIMA)-were used to interpret the biomethane production. All models showed promising fitting of the cumulative biomethane production, as indicated by high R2 and low RMSE values. Among these models, the ARIMA model exhibited the closest fit to the actual data. The biomethane production rate, derived from the modified Gompertz Model, increased as the incubation period increased, with D21 yielding the highest rate of 31.13 mL/gVS. This study suggests that the application of biochar in the anaerobic fermentation of glucose, particularly considering the short incubation period, holds significant potential for improving the overall performance of anaerobic digestion.

Effects of Iron, Lime, and Porous Ceramic Powder Additives on Methane Production from Brewer's Spent Grain in the Anaerobic Digestion Process.

The process of anaerobic digestion used for methane production can be enhanced by dosing various additive materials. The effects of these materials are dependent on various factors, including the processed substrate, process conditions, and the type and amount of the additive material. As part of the study, three different materials-iron powder, lime, and milled porous ceramic-were added to the 30-day anaerobic digestion of the brewer's spent grain to improve its performance. Different doses ranging from 0.2 to 2.3 gTS × L-1 were tested, and methane production kinetics were determined using the first-order model. The results showed that the methane yield ranged from 281.4 ± 8.0 to 326.1 ± 9.3 mL × gVS-1, while substrate biodegradation ranged from 56.0 ± 1.6 to 68.1 ± 0.7%. The addition of lime reduced the methane yield at almost all doses by -6.7% to -3.3%, while the addition of iron powder increased the methane yield from 0.8% to 9.8%. The addition of ceramic powder resulted in a methane yield change ranging from -2.6% to 4.6%. These findings suggest that the use of additive materials should be approached with caution, as even slight changes in the amount used can impact methane production.

Study on the Effect of Hydrothermal Carbonization Parameters on Fuel Properties of Chicken Manure Hydrochar.

Economic development and population growth lead to the increased production of chicken manure, which is a problematic organic waste in terms of its amount, environmental threats, and moisture content. In this study, hydrothermal carbonization, an emerging way of waste disposal, was performed on chicken manure to produce an energy-rich material called hydrochar. The effects of hydrothermal carbonization temperature (180, 240, 300 °C) and process time (30, 90, 180 min) were summarized. Proximate and ultimate analysis, as well as low and high heating values were applied both on raw material and derived hydrochars. Additionally, the performance of the process was examined. The obtained results show that hydrothermal carbonization is a feasible method for chicken manure disposal and valorization. Although the process time did not influence the fuel properties of chicken manure considerably, a higher temperature led to a significantly higher heating value, reaching 23,880.67 ± 34.56 J × g-1 at 300 °C and 180 min with an improvement of ~8329 J × g-1 compared with raw chicken manure (15,551.67 J × g-1). Considering the energy gain value, the hydrochar derived at 240 °C in 30 min had the best result. Moreover, the energy consumption for this process was relatively low (124.34 ± 8.29 kJ × g-1). With its still feasible fuel properties and high heating value of 20,267.00 ± 617.83 kJ × g-1, it was concluded that these parameters of chicken manure hydrochar are the most beneficial and present a potential alternative for conventional fuel.

The Use of Barley Malt as a Binder in Molding Sand Technology.

The aim of this study was to attempt to use barley malt as a natural, organic binder in the technology of molding sand. TGA analysis of the binder was performed, during which temperatures of thermal decomposition of its components were determined. The results of TG/DTG analysis show that a loss of ~75% of mass of the MB binder is organic matter. Over 50% of this is starch. The results indicate the possibility of using a binder made of barley malt as a binding material for quartz sand grains. This fact was confirmed by tests carried out with use of SEM. During the observations, it was found that barley malt forms smooth bridges connecting individual grains of quartz sand. The typical properties of molding sands with barley malt were also determined, compared to sands containing commonly used binders. At the same time, the influence of the content of this binder on flowability, permeability, strength properties, and wear resistance was assessed. It has been found that increasing the binder content in molding mass results in an increase in strength and wear resistance, as opposed to flowability and permeability. Test castings were also made. It was found that the addition of a binder made of barley malt has a positive effect on the surface quality of castings. This was confirmed by roughness measurements of the test castings. At the same time, a tendency to excessive gas evolution during pouring was shown, with higher contents of this binder. Moreover, greater amounts of barley malt in the molding sand (MB 5%) as compared to the lower content (MB 2%) increased the thickness of the burnt layer of the sand by 25%. This is due to the exothermic reaction when more binder is burnt. It is extremely important from the point of view of the regeneration of molding sand.

The Influence of Low-Temperature Food Waste Biochars on Anaerobic Digestion of Food Waste.

The proof-of-the-concept of application of low-temperature food waste biochars for the anaerobic digestion (AD) of food waste (the same substrate) was tested. The concept assumes that residual heat from biogas utilization may be reused for biochar production. Four low-temperature biochars produced under two pyrolytic temperatures 300 °C and 400 °C and under atmospheric and 15 bars pressure with 60 min retention time were used. Additionally, the biochar produced during hydrothermal carbonization (HTC) was tested. The work studied the effect of a low biochar dose (0.05 gBC × gTSsubstrate-1, or 0.65 gBC × L-1) on AD batch reactors' performance. The biochemical methane potential test took 21 days, and the process kinetics using the first-order model were determined. The results showed that biochars obtained under 400 °C with atmospheric pressure and under HTC conditions improve methane yield by 3.6%. It has been revealed that thermochemical pressure influences the electrical conductivity of biochars. The biomethane was produced with a rate (k) of 0.24 d-1, and the most effective biochars increased the biodegradability of food waste (FW) to 81% compared to variants without biochars (75%).

Carbonized Solid Fuel Production from Polylactic Acid and Paper Waste Due to Torrefaction.

The quantity of biodegradable plastics is increasing steadily and taking a larger share in the residual waste stream. As the calorific value of biodegradable plastic is almost two-fold lower than that of conventional ones, its increasing quantity decreases the overall calorific value of municipal solid waste and refuse-derived fuel which is used as feedstock for cement and incineration plants. For that reason, in this work, the torrefaction of biodegradable waste, polylactic acid (PLA), and paper was performed for carbonized solid fuel (CSF) production. In this work, we determined the process yields, fuel properties, process kinetics, theoretical energy, and mass balance. We show that the calorific value of PLA cannot be improved by torrefaction, and that the process cannot be self-sufficient, while the calorific value of paper can be improved up to 10% by the same process. Moreover, the thermogravimetric analysis revealed that PLA decomposes in one stage at ~290-400 °C with a maximum peak at 367 °C, following a 0.42 reaction order with the activation energy of 160.05 kJ·(mol·K)-1.

Lab-Scale Study of Temperature and Duration Effects on Carbonized Solid Fuels Properties Produced from Municipal Solid Waste Components.

In work, data from carbonization of the eight main municipal solid waste components (carton, fabric, kitchen waste, paper, plastic, rubber, paper/aluminum/polyethylene (PAP/AL/PE) composite packaging pack, wood) carbonized at 300-500 °C for 20-60 min were used to build regression models to predict the biochar properties (proximate and ultimate analysis) for particular components. These models were then combined in general models that predict the properties of char made from mixed waste components depending on pyrolysis temperature, residence time, and share of municipal solid waste components. Next, the general models were compared with experimental data (two mixtures made from the above-mentioned components carbonized at the same conditions). The comparison showed that most of the proposed general models had a determination coefficient (R2) over 0.6, and the best prediction was found for the prediction of biochar mass yield (R2 = 0.9). All models were implemented into a spreadsheet to provide a simple tool to determine the potential of carbonization of municipal solid waste/refuse solid fuel based on a local mix of major components.

The Prediction of Calorific Value of Carbonized Solid Fuel Produced from Refuse-Derived Fuel in the Low-Temperature Pyrolysis in CO2.

The decrease in the calorific value of refuse-derived fuel (RDF) is an unintended outcome of the progress made toward more sustainable waste management. Plastics and paper separation and recycling leads to the overall decrease in waste's calorific value, further limiting its applicability for thermal treatment. Pyrolysis has been proposed to densify energy in RDF and generate carbonized solid fuel (CSF). The challenge is that the feedstock composition of RDF is variable and site-specific. Therefore, the optimal pyrolysis conditions have to be established every time, depending on feedstock composition. In this research, we developed a model to predict the higher heating value (HHV) of the RDF composed of eight morphological refuse groups after low-temperature pyrolysis in CO2 (300-500 °C and 60 min) into CSF. The model considers cardboard, fabric, kitchen waste, paper, plastic, rubber, PAP/AL/PE (paper/aluminum/polyethylene) composite packaging pack, and wood, pyrolysis temperature, and residence time. The determination coefficients (R2) and Akaike information criteria were used for selecting the best model among four mathematical functions: (I) linear, (II) second-order polynomial, (III) factorial regression, and (IV) quadratic regression. For each RDF waste component, among these four models, the one best fitted to the experimental data was chosen; then, these models were integrated into the general model that predicts the HHV of CSF from the blends of RDF. The general model was validated experimentally by the application to the RDF blends. The validation revealed that the model explains 70-75% CSF HHV data variability. The results show that the optimal pyrolysis conditions depend on the most abundant waste in the waste mixture. High-quality CSF can be obtained from wastes such as paper, carton, plastic, and rubber when processed at relatively low temperatures (300 °C), whereas wastes such as fabrics and wood require higher temperatures (500 °C). The developed model showed that it is possible to achieve the CSF with the highest HHV value by optimizing the pyrolysis of RDF with the process temperature, residence time, and feedstock blends pretreatment.

Oxytree Pruned Biomass Torrefaction: Process Kinetics.

Oxytree is a fast-growing energy crop with C4 photosynthesis. In this research, for the first time, the torrefaction kinetic parameters of pruned Oxytree biomass (Paulownia clon in Vitro 112) were determined. The influence of the Oxytree cultivation method and soil class on the kinetic parameters of the torrefaction was also investigated. Oxytree pruned biomass from a first-year plantation was subjected to torrefaction within temperature range from 200 to 300 °C and under anaerobic conditions in the laboratory-scale batch reactor. The mass loss was measured continuously during the process. The relative mass loss increased from 1.22% to 19.56% with the increase of the process temperature. The first-order constant rate reaction (k) values increased from 1.26 × 10-5 s-1 to 7.69 × 10-5 s-1 with the increase in temperature. The average activation energy for the pruned biomass of Oxytree torrefaction was 36.5 kJ∙mol-1. Statistical analysis showed no significant (p < 0.05) effect of the Oxytree cultivation method and soil class on the k value. The results of this research could be useful for the valorization of energy crops such as Oxytree and optimization of waste-to-carbon and waste-to-energy processes.

Oxytree Pruned Biomass Torrefaction: Mathematical Models of the Influence of Temperature and Residence Time on Fuel Properties Improvement.

Biowaste generated in the process of Oxytree cultivation and logging represents a potential source of energy. Torrefaction (a.k.a. low-temperature pyrolysis) is one of the methods proposed for the valorization of woody biomass. Still, energy is required for the torrefaction process during which the raw biomass becomes torrefied biomass with fuel properties similar to those of lignite coal. In this work, models describing the influence of torrefaction temperature and residence time on the resulting fuel properties (mass and energy yields, energy densification ratio, organic matter and ash content, combustible parts, lower and higher heating values, CHONS content, H:C and O:C ratios) were proposed according to the Akaike criterion. The degree of the models' parameters matching the raw data expressed as the determination coefficient (R2) ranged from 0.52 to 0.92. Each model parameter was statistically significant (p < 0.05). Estimations of the value and quantity of the produced torrefied biomass from 1 Mg of biomass residues were made based on two models and a set of simple assumptions. The value of torrefied biomass (€123.4·Mg-1) was estimated based on the price of commercially available coal fuel and its lower heating value (LHV) for biomass moisture content of 50%, torrefaction for 20 min at 200 °C. This research could be useful to inform techno-economic analyses and decision-making process pertaining to the valorization of pruned biomass residues.