Publications

The research impact of catalysts on the hydrothermal carbonization (HTC) process remains an ongoing debate, especially regarding the quest to enhance biomass conversion into fuels and chemicals, which requires diverse catalysts to optimize bio-oil utilization. Comprehensive insights and standardized analytical methodologies are crucial for understanding HTC’s potential benefits in terms of biomass conversion stages. This review seeks to understand how catalysts enhance the HTC of biomass for liquid fuel and hydrochar production, drawing from the following key sections: (a) catalyst types applied in HTC processes; (b) biochar functionality as a potential catalyst; (c) catalysts increasing the success of HTC process; and (d) catalyst’s effect on the morphological and textural character of hydrochar. The performance of activated carbon would greatly increase via catalyst action, which would progress the degree of carbonization and surface modification, alongside key heteroatoms. As catalytic HTC technology advances, producing carbon materials for thermochemical activities will become more cost-effective, considering the ever-growing demands for high-performance thermochemical technologies.

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 very fast growing Oxytree (Paulownia Clon in Vitro 112) is marketed as a promising new energy crop. The tree has characteristically large leaves, thrives in warmer climates, and requires initial pruning for enhanced biomass production in later years. We explored valorizing the waste biomass of initial (first year) pruning via thermal treatment. Specifically, we used torrefaction (‘roasting’) to produce biochar with improved fuel properties. Here for the first time, we examined and summarized the fuel properties data of raw biomass of Oxytree pruning and biochars generated via torrefaction. The effects of torrefaction temperature (200~300 °C), process time (20~60 min), soil type, and agro-technical cultivation practices (geotextile and drip irrigation) on fuel properties of the resulting biochars were summarized. The dataset contains results of thermogravimetric analysis (TGA) as well as proximate and ultimate analyses of Oxytree biomass and generated biochars. The presented data are useful in determining Oxytree torrefaction reaction kinetics and further techno-economical modeling of the feasibility of Oxytree valorization via torrefaction. Oxytree torrefaction could be exploited as part of valorization resulting from a synergy between a high yield crop with the efficient production of high-quality renewable fuel.

This work compares reactive (castor) and non-reactive (rapeseed, sunflower, linseed, and used cooking) oils, each at a dosage of 10 wt%, when incorporated into an in-house two-component polyurethane (PU) parquet adhesive. A commercial market adhesive was tested only as an external benchmark and was not modified. Mechanical properties were evaluated according to EN ISO 17178, inorganic leaching according to EN 12457-4, and volatile organics were screened by headspace GC–MS (not comparable to ISO 16000-9 chamber protocols). All in-house formulations met the EN ISO 17178 acceptance limits. The sunflower oil variant showed the highest shear strength, whereas rapeseed and castor oils provided stable tensile performance. HS-GC-MS did not yield high-confidence VOC identifications; therefore, no regulatory emission claim is made. The formulation with used cooking oil exhibited the largest variability and elevated leaching of Zn and Sb, underscoring the need for feedstock quality control. At 10 wt% loading, standard-compliant performance was obtained with both reactive and non-reactive oils, suggesting that physical modification can be sufficient, while castor oil may additionally react. In contrast to derivatized oils reported elsewhere, our approach employs unmodified oils, thereby avoiding extra reaction steps—such as epoxidation, hydroxylation, and transesterification—that typically increase the carbon footprint, while still meeting relevant standards. Full VOC chamber testing and LCA are beyond the scope of this study.

The present study sought to investigate the formation of carbon monoxide (CO) during aerobic biostabilization (AB) of the organic fraction of municipal solid waste (OFMSW) in forced aerated piles. Understanding the factors influencing CO formation may be important not only for safety, but also for environmental and technical reasons. The objective of the study was to determine the effect of the technical parameters of the piles on the concentration of CO in the process gas during AB of the OFMSW in a full-scale waste treatment system: rate of waste aeration (from 3365 to 12,744 m3∙Mg−1), waste mass loads in the pile (from 391 to 702 Mg), thermal conditions, application of sidewalls as an element of pile bioreactor construction, concentration of O2 and CO2 in the waste piles and the duration of the process from 6 to 9 weeks. The temperature and concentration of O2, CO2, CO, CH4 were measured in each pile at weekly intervals. All six reactors provide stable thermal and aerobic conditions, but the presence of CO was observed, ranging from a few to over 2000 ppm, which demonstrated that ensuring optimum conditions for the process is not sufficient for CO to be eliminated. A moderate, non-linear rise in CO concentration was observed along with a rise in the temperature inside the reactors. Concentrations of CO were not highly correlated with those of O2 or CO2. An increase in waste mass loads increased the CO concentration in waste piles, while application of sidewalls decreased CO concentration. Increasing aeration rate had an influence on CO production, and the highest CO concentrations were noted under air flow rate 5.3 m3·Mg−1·h−1.

Knowledge of kinetic parameters of CO production during biowaste composting is significantly important for the prediction of its course and estimation of total gas quantity. This allows increasing the control of the process, to minimize its negative impact on the environment and to protect the occupational safety of employees exposed to CO in the biowaste composting plant. For the first time, a full study of the influence of temperature and biowaste sterilization on the kinetics of CO production is presented. The lab-scale experiments used a mixture of green waste, dairy cattle manure, and sawdust in two variants: sterilized and non-sterilized samples. The process was carried out in controlled temperature reactors with measuring the concentrations of CO, O2, and CO2 every 12 h.CO production and k value increased with temperature. However, higher CO production was observed in biotic conditions between 10~50 °C, suggesting the biotic CO formation and 1st-order kinetics. The abiotic (thermochemical) process was more efficiently generating CO above 50 °C, described with a 0-order kinetic model. Additionally, the rate constant (k) value of CO production under biotic conditions was increasing up to a temperature of 60 °C, above which a slight decrease in CO production rate was observed at 70 °C. The presented results are the basis for further studies focused on the feasibility of (1) the mitigation and (2) valorization of CO production during the biowaste biostabilization are warranted.

The aim of the study was to obtain alginate oligosaccharides by using two degradation methods of sodium alginate (SA): with hydrochloric acid (G—guluronate, M—mannuronate and G + M fractions) and hydrogen peroxide (HAS—hydrolyzed SA), in order to assess and compare their biological activity and physico-chemical properties, with an attempt to produce gels from the obtained hydrolysates. The efficiency of each method was determined in order to select the fastest and most efficient process. The ferric ion reducing antioxidant power (FRAP), the ability to scavenge DPPH free radicals, rheological properties, Fourier Transformed Spectroscopy (FTIR) and the microbiological test against Escherichia coli and Staphylococcus aureus were performed. In order to check the functional properties of the obtained oligosaccharides, the texture profile analysis was assessed. The hydrolysis yield of acid SA depolymerization was 28.1% and from hydrogen peroxide SA, depolymerization was 87%. The FTIR analysis confirmed the degradation process by both tested methods in the fingerprint region. The highest ferric reducing antioxidant power was noted for HSA (34.7 µg), and the highest hydroxyl radical scavenging activity was obtained by G fraction (346 µg/Trolox ml). The complete growth inhibition (OD = 0) of alginate hydrolysates was 1%. All tested samples presented pseudoplastic behavior, only HSA presented the ability to form gel.

A significant challenge in the utilization of alternative gaseous fuels is to use their energy potential at the desired location, considering economic feasibility and sustainability. A potential solution is a compression, transportation in pressure tanks, and generation of electricity and heat directly at the recipient. In this research, the potential for generating syngas from abundant waste substrates was analyzed. The sewage sludge (SS) was used as an example of a bulky and abundant resource that could be valorized via gasification, compression, and transport to end-users in containers. A model was developed, and theoretical analyses were completed to examine the influence of the calorific value of the syngas produced from the SS gasification (under different temperatures and gasifying agents) on the efficiency of energy transportation of compressed syngas. First, the gasification simulation was carried out, assuming equilibrium in a downdraft gasifier (reactor) from 973–1473 K and five gasifying agents (O2, H2, CO2, water vapor, and air). Molar ratios of the gasifying agents to the (SS) C ranged from 0.1–1.0. The model predicted syngas composition, lower calorific values (LHV) for a given molar ratio of the gasification agent, and compressibility factor. It was shown that the highest LHV was obtained at 0.1 molar ratio for all gasifier agents. The highest LHV (~20 MJ∙(Nm3)−1) was obtained by gasification with H2 and the lowest (~13 MJ∙(Nm3)−1) in the case of air. Next, the available syngas volume in a compressed gas transportation unit and the stored energy was estimated. The largest syngas volume can be transported when O2 is used as a gasifying agent, but the highest amount of transported energy was estimated for gasification with H2. Finally, the techno-economic analyses showed that syngas from SS could be competitive when the energy of compressed syngas is compared with the demand of an average residential dwelling. The developed syngas energy transport system (SETS) concept proposes a new method to distribute compressed syngas in pressure tanks to end-users using all modes of transport carrying intermodal ISO containers. Future work should include the determination of energy demand for syngas compression, including pressure losses, heat losses, and analysis of the influence of syngas on storage and compression devices.

Abstract Anaerobic digestion (AD) is a useful process that could be utilized for food waste (FW) management. Previous studies have shown that carbon materials (CMs) could be an important additive for increasing biomethane yield. However, why CMs improve AD is still uncertain. A significant body of research has been dedicated to investigating the impact of CMs supplementation on biogas production. However, this article specifically emphasizes examining this effect concerning the specific surface area and the functional groups (e.g. hydroxyl groups, carbonyl groups, or unsaturated carbon structures) present on the surface of CMs, produced by torrefaction—TP (240 °C/60 min), pyrolysis—BC (600 °C/60 min), and hydrothermal carbonization—HC (240 °C/60 min/6–10 Bar) processes. The analyses showed that the size of the specific surface area of the CMs (TP—7.72 m 2 g −1 , BC- 115.00 m 2 g −1 , HC—5.46 m 2 g −1 ), does not correspond to the production of biomethane. The highest biomethane potential was found for CMs with the lowest SSA, precisely TP and HC, equal to 407 and 394 mL gVS −1 , which was about 13 and 9% higher than production from FW as a sole source of carbon, respectively. The FTIR analysis confirmed the abundance of different organic functional groups on the surface of TP and HC, which could contribute to improved AD performance. These organic residuals, as thermal degradation products, could be an additional source of carbon for microorganisms. The addition of BC, with the highest SSA, decreased the first-order biomethane rate constant k by 16.4% in comparison to food waste without CMs, which could be related to the presence of harmful, more complex organic compounds on the surface of biochar.

Abstract To date, only a few studies focused on the carbon monoxide (CO) production during waste composting; all targeted on CO inside piles. Here, the CO net emissions from compost piles and the assessment of worker’s occupational risk of exposure to CO at large-scale composting plants are shown for the first time. CO net emissions were measured at two plants processing green waste, sewage sludge, or undersize fraction of municipal solid waste. Effects of the location of piles (hermetised hall vs. open yard) and turning (before vs. after) were studied. Higher CO net emission rates were observed from piles located in a closed hall. The average CO flux before turning was 23.25 and 0.60 mg‧m −2 ‧h −1 for hermetised and open piles, respectively, while after – 69.38 and 5.11 mg‧m −2 ‧h −1 . The maximum CO net emissions occurred after the compost was turned (1.7x to 13.7x higher than before turning). The top sections of hermetised piles had greater CO emissions compared to sides. Additionally, 5% of measurement points of hermetised piles switched to ‘CO sinks’. The 1-h concentration in hermetised composting hall can reach max. ∼50 mg CO·m −3 before turning, and >115 mg CO·m −3 after, exceeding the WHO thresholds for a 1-h and 15-min exposures, respectively.