Highest Higher Heating Value Research Articles

Evaluation of an operating durian shell charcoal briquette manufacturing line and development of a biorefinery process for higher value products

In assessing the feasibility of carbonization for the treatment of durian shell, a large-scale (10 T) fuel briquette manufacturing line is evaluated, taking into consideration the actual processing time and the effect of the biomass high moisture content on overall efficiency. The fuel product exhibits a high higher heating value (HHV) (33.21 MJ/kg) but with a low production efficiency (10 %) and a high cost of production (0.55 USD/kg briquette). One alternate biorefinery process was proposed to turn durian shells into much higher value materials, including high-methoxyl pectin (DE > 90 %), high surface area activated carbon (>300 m2/g) and mineral-rich biochar, with higher recovery efficiency and selling prices, most notably pectin at 40 USD/kg. The results from this study are then used to provide recommendations for feasible treatment, not only for durian shells but also for a variety of different complex and highly recalcitrant biomass in pursuit of a more sustainable agricultural production.

Sustainable hydrothermal co-carbonization of residues from the vegetable oil industry and sewage sludge: Hydrochar production and liquid fraction valorisation

In this study, the hydrothermal co-carbonization (co-HTC) of residues from the vegetable oil industry (pumpkin oil cake – PC, hemp oil cake – HC) and sewage sludge (SS) was investigated for the first time. The co-HTC was performed at 250 °C and a treatment time of 5 h. The effects of the mass ratio of the feedstocks (1:1, 1:3 and 3:1) on the properties of the HTC products were investigated using various analytical methods (NMR, XRD, 3D-EEM, FTIR, etc.).The co-HTC of SS with oil cakes resulted in improved fuel properties of the hydrochar and an increase in C content from 36.9 to 53.7 wt%, and an increase in the higher heating value (HHV) from 14.8 to 23.6 MJ/kg. The combination with HC gave hydrochars with a higher HHV and higher C content than the combination with PC. The hydrochar yield varied in the range of 39.4–55.3 wt%. NMR analysis revealed a higher proportion of aliphatic (∼60 %) than aromatic compounds (∼35 %) in the hydrochars, as well as a high content of orthophosphate and unsaturated fatty acids. The liquid fractions were rich in nutrients and organic compounds, but toxic to aquatic organisms. The hydrochars and liquid fractions performed well in the germination test with plant species.

Ionic liquid-catalyzed hydrothermal carbonization of sewage sludge: Effect of residence time and liquid phase circulation on hydrochar characteristic

The ionic liquid (IL, [DMAPA]HSO4) was used to catalyze hydrothermal carbonization (HTC) of sewage sludge (SSL), the study discussed how residence time and liquid-phase circulation influence the characteristics of the hydrochar. The decarboxylation process in IL-catalyzed HTC led to lower hydrochar yield but higher higher heating value (HHV). And the secondary hydrochar formation promoted by IL favored the system for high energy feedback (EF), but iron was involved in the secondary hydrochar formation. At the optimum hydrothermal time (90 min), the EF reached 124 % and the removal efficiencies of Fe, Mg, Mn, and Zn were 66 %, 73 %, 96 %, and 90 %, respectively. Functional groups on organic acids (COO–), amides (CO), and polysaccharides (C–O–C) in the SSL were sequentially removed during the IL-catalyzed HTC process, while cross-linking and graphitization occurred, resulting in higher ignition temperatures and lower metal contents. However, multiple cycles of the liquid phase resulted in a decrease in the catalytic properties of IL, resulting in low EF hydrochar with high metal content and functional group intensity. Catalytic graphitization is the key to obtaining hydrochar with high HHV and low metal content. Therefore, future development of catalysts is needed to facilitate the dehydration, decarboxylation and graphitization process of HTC.

Hydrothermal Carbonization of Green Harvesting Residues (GHRs) from Sugar Cane: Effect of Temperature and Water/GHR Ratio on Mass and Energy Yield.

The Valle del Cauca region in Colombia is a significant producer of sugar cane, resulting in large quantities of agricultural residues (green harvesting residues (GHRs)). To ensure sustainable management of these residues, it is crucial to implement proper treatment and disposal technologies while also reusing waste to produce biogas, bioelectricity, or biofuels. The biomass hydrothermal carbonization process offers a means to convert these residues into useful products that serve as fuels or valuable energy materials. This thermal treatment involves the use of water as a solvent and reagent within the biomass's internal structure. In this study, sugar cane cutting residues were collected with relatively high moisture content of 8.5% wt. These residues were subjected to carbonization temperatures ranging from 200 to 300 °C, along with water/GHR ratios between 5/1 and 10/1. The properties of the resulting hydrocarbons were analyzed by using proximate and ultimate analysis. The objective was to produce hydrochar samples with the highest higher heating value (HHV) and energy density compared with the GHRs. The HHV value of the hydrochar showed a significant increase of 69.6% compared with that of the GHRs, reaching 43.5 MJ/kg. Besides, process parameters were optimized for mass yields, energy yields, and ash content. This exploration led us to investigate a new temperature range between 280 and 320 °C, allowing us to establish an optimal value for the hydrochar's properties.

Optimization of Mixing Ratios of Binders and Organic Matter for Charcoal Briquette Using Biochars Derived from Water Hyacinth

Since Ethiopia relies on biomass resources for about 90% of its energy sources, problems such as deforestation and soil degradation have been intensified more than ever. To mitigate these problems, a possibility of using excess aquatic biomass such as water hyacinth as alternative energy is being investigated. In this study, fuel characteristics of biochar briquettes made from combination of water hyacinth biochars, different binders, and organic matter used in Ethiopia were evaluated. Water hyacinth was dried and pyrolyzed at 400 and 800°C (WHB400 and WHB800, respectively). Water hyacinth biochar was mixed with different binders (molasses and Ethiopian soil) at a ratio of [6:4:0] without organic matter, or at a ratio of [6:3:1] with organic matter ([water hyacinth biochar:binder:organic matter]). The experimental results showed that WHB400 with molasses as binder without organic matter [6:4:0] was the best mixing ratio as biochar briquette with the highest higher heating value and the greatest compressive strength among all other biochar briquettes. Therefore, this study showed water hyacinth biochar could be a great potential as an alternative fuel to conventional acacia charcoal.

Torrefaction and hydrothermal carbonization of waste from the paper industry: Effects of atmosphere choice and pretreatment with natural acidic reagent on fuel properties

The hydrothermal carbonization (HTC) and torrefaction of paper sludges and biological sludges from the paper industry were investigated and the effect of pretreatment of the samples with alcoholic vinegar was evaluated. The HTC was performed at two different reaction times, while the torrefaction took place at two different temperatures and two atmospheres. The gas analysis showed that the optimal torrefaction time for the N2 atmosphere can be determined by observing the CO2 content in the gas phase, which is not possible for the CO2 atmosphere. The TGA analysis showed that the choice of atmosphere influences further combustion, with samples torrefied at lower temperatures being more sensitive to it. The carbon (C) content in the thermally treated samples increases from 39.85 to 48.06 wt% for biological sludge and from 40.02 to 60.21 wt% for paper sludge. The H/C and O/C ratios decrease and approach the values of conventional fuels. The fuel ratio is higher for the torrefied samples. The higher heating value (HHV) increased from 17.4 to 21.4 MJ/kg for biological sludge and from 16.2 to 22.4 MJ/kg for paper sludge. Higher temperature and longer treatment time led to products with a higher HHV and a higher energy density. The highest energy yields were achieved during torrefaction at 250 °C, regardless of the atmosphere, with temperature and type of material having the greatest influence. Acidification of the samples or acidic media in the HTC affects the properties of the products by increasing the C content and HHV and affecting combustion.

Hydrochars derived via wet torrefaction of empty fruit bunches: Effect of temperature and time, comparison to oil palm trunks counterpart, and their pyrolysis behavior

In this study, hydrochars derived from the wet torrefaction of empty fruit bunches (EFB) were characterized and compared to those of oil palm trunks (OPT). Then, the kinetics modelling of EFB-derived hydrochars was evaluated and compared with the Distributed Activation Energy Model (DAEM) under logistics distribution via thermogravimetric analysis (TGA) under pyrolytic conditions at different heating rates. Bench-scale pyrolysis of EFB-derived hydrochars were also performed and characterized. This study elucidates the effect of prolonged residence time (3–72 hours) at different temperatures (180–220 °C) on the wet torrefaction of EFB, and comparison to OPT provides an understanding of wet torrefaction mechanisms. The pyrolysis kinetics of EFB-derived hydrochars provide insights into their pyrolysis behavior and their potential in pyrolytic application. Increased temperature and residence time enhanced the higher heating value (HHV) of the hydrochars at the expense of low mass yield. Hydrochars obtained at 220 °C and 72 hours had the highest HHV at 27.4 ± 0.5 MJ kg−1 with a mass yield of 38.3 ± 2 wt%. EFB-derived hydrochars had a higher mass yield than OPT-derived hydrochars. The van Krevelen diagram revealed that dehydration was the primary reaction pathway for EFB and OPT-derived hydrochars. SEM showed the formation of secondary deposits on both EFB and OPT hydrochars. EFB-derived hydrochars obtained at 220 °C and 72 hours had the highest mean activation energy (E0) with a distribution of activation energy (σ) from 176.7 to 181.7 kJ mol−1 and 43.4–49.9 kJ mol−1, respectively. The increased mean and distribution of activation energies were attributed to the lignin-dense structure of the hydrochars. The kinetic parameters of the hydrochars were also independent of heating rates at low heating rates (< 20 °C min−1). The thermal stability of the pyrochars obtained from EFB-derived hydrochars enabled their applications in fields such as carbon support, activated carbon, water purification process, or carbon sequestration.

Comparison of torrefaction and hydrothermal carbonization of high-moisture microalgal feedstock

A comprehensive comparison is conducted to explore the conversion performance of torrefaction and hydrothermal carbonization of high-moisture microalga for producing solid biofuel with low expense and environmental impact. The results suggest that when their solid yields are close, the hydrochar has higher HHV (higher heating value) (21.10–25.39 MJ kg−1) and energy yield (72.48–92.29%) than the biochar. The graphitization degrees of the biochar and hydrochar are 1.298–3.107 and 2.193–3.049, respectively. Considering fuel grade, the biochar is in biomass and peat zones, but the hydrochar is only in the biomass zone. The biochar's elemental valence transformation and graphitization degree are better than hydrochar's. The pyrolysis and combustion characteristics of the hydrochar are better than those of the biochar when considering the thermodegradation data, leading to a lower expense and environmental impact. The results are conducive to efficiently figuring out a solution with a comparative advantage for microalgal thermochemical conversion. The hydrothermal carbonization conditions at 160 °C for 2 h are the best operation for microalgal solid biofuel production.

Comparing Wood Chip Quality from Different Sources across the Southeastern United States

Abstract Global use of renewable energy has risen over the past few decades because of international energy policy changes, new legislation, and an effort to create a more sustainable energy source for a rapidly growing global population. One of these renewable energy sources is biofuels, specifically in the form of wood pellets created from wood chips. Wood pellet manufacturers in the southeastern United States must adhere to rigid quality-control standards of the European markets where their pellets are shipped and consumed. Thus, there is a need to improve our understanding of the factors that influence the quality of the source materials. Higher heating value (HHV), moisture content (MC), ash content, elemental composition, and size stratification are all important quality factors to consider when analyzing wood chips. Variations in these quality factors can cause longer drying times, blockages in feed systems, excess waste, and fluctuations in energy output. The objective of this study was to quantify these quality factors across multiple sources of wood chips. Softwood and hardwood in-woods chip samples as well as softwood mill residual chips were collected from thinnings and clear-cuts across the southeastern United States. Softwoods had a greater HHV and MC than hardwood chips, with 18,949 kJ/kg and 18,242 kJ/kg, respectively. Softwood thinnings had the highest HHV and lowest ash content. However, only 4 of the 60 samples analyzed were from softwood thinnings. This study provides an overview of the variation in wood chip quality across the southeastern United States.

Fe-catalyzed low-temperature hydrothermal liquefaction of coffee shells: Influence of operating parameters on bio-oil yield, distribution of bio-oil products

Coffee shells were hydrothermally liquefied under FeCl3 catalysis to produce crude bio-oils at temperatures ranging from 190 to 300 °C. This study investigated the impact of operational parameters (hydrothermal temperature, residence time, Fe3+ catalyst concentration, extraction solvents) on the bio-oil yield. Optimized hydrothermal conditions resulted in a conversion rate of 68.47 % for coffee shells, leading to an 11.51 % yield of light bio-oil extracted from the aqueous phase and a 35.99 % yield of heavy bio-oil from the solid phase. The chemical composition and distillate distribution of the bio-oil were determined through organic element analysis, GC-MS analysis, and TG/DTG analysis. The light bio-oil primarily consisted of furfural derivatives and phenolic derivatives; however, it only accounted for approximately 14.50 % of the total energy recovered from the feedstock. The components present in heavy bio-oils varied depending on the extraction solvents used but mainly comprised fatty acids and their derivatives. Acetone extraction yielded the highest amount of bio-oil; however, its high O/C ratio reduced its higher heating value (HHV). Ethanol extraction also resulted in higher yields but TG/DTG analysis indicated that these fractions contained more refractory volatiles and solid residues compared to other solvents used for extraction. In comparison, n-hexane extraction had a lower yield than both previous methods but offered a lower O/C ratio and higher HHV instead. Our study demonstrated that Fe-catalyzed hydrothermal liquefaction is an efficient method for obtaining value-added compounds and hydrocarbon fuels from coffee shells.

How do different feedstocks and pyrolysis conditions effectively change biochar modification scenarios? A critical analysis of engineered biochars under H2O2 oxidation

Biochar oxidation is known as a modification method to enhance the beneficial sorption characteristics of biochar. To explore this, a comparative physio-chemical analysis of non-oxidized and oxidized biochar with hydrogen peroxide (H2O2) was conducted using different feedstocks. Biochars were pyrolyzed at temperatures of 350, 450, and 550 °C and were derived from wheat straw, rye straw, wood residues, cherry stone, sewage sludge, and cattle manure, marked as BWS, BRS, BWR, BCS, BSS, and BCM. The pyrolysis temperature of 550 °C in BWS and BRS led to the formation of newly arranged vessels and regular pores scattered in their walls. X-ray photoelectron spectroscopy of wood-based biochars showed a notable increase in surface oxygen-contained functional groups for O-BWR350, O-BWR450, O-BWR550, O-BCS350, O-BCS450, and O-BCS550 with increased values by 6.5 %, 27.9 %, 42.3 %, 3.9 %, 31.2 %, and 52.4 % compared to their correspondent non-oxidized biochars. The sharp peaks of crystallization in non-oxidized biochars diminished after oxidation as detected by X-ray diffractometer analysis. Also, Cd removal efficiency in O-BCS550 (65 %) and O-BWR550 (69 %) appeared with outstanding results among all biochar types. Based on thermo-gravimetric analysis, the lowest and highest mass losses on average were related to BRS (22.5 %), and O-BCM (39.7 %). Also, the high heating value (HHV) analysis showed that BWR550 and BCS550 biochars had the highest HHV with 33.6 and 32.5 MJ kg−1, and O-BSS350 had the lowest value with 10.1 MJ kg−1. By taking feedstock degradability and pyrolysis temperature into account, this work presents a novel approach to maximize the benefits of H2O2-modified biochar. This will enable us to create a variety of engineered biochars in a clean and economical way as opposed to costly activation oxidants.

Hydrothermal liquefaction of Elaeis guineensis trunks: Lessons learned from a case study in Guatemala

The oil palm industry has been under public scrutiny during the last decades due to environmental and social issues related to its practices. Oil palm (Elaeis guineensis Jacq.) trunks (OPTs) are of special interest as they are left idle in the field after the replanting process which is performed every 25 years. This common practice results in harvesting challenges, phytosanitary risks, and a loss of bioenergy potential. Due to their high moisture content and fibrous nature, OPTs present a problem for traditional conversion processes that require a dry and homogeneous material. This study evaluates the feasibility of converting OPTs into a bio-crude oil and biochar to increase the sustainability of the oil palm sector. To date, research efforts have primarily focused on hydrothermal liquefaction (HTL) of OPT without catalysts, resulting in a limited understanding of the potential of OPTs. Thus, the main novelty of this work is the evaluation of the effects of catalyst dosage (0–5 wt%) on the bio-oil yield, reaction temperature (260–300∘C), and residence time (15–60 min) using a half-fraction experimental design methodology. For this, OPTs extracted from two plantations in Guatemala were used. The maximum bio-oil yield (26.77 ± 3.60 wt%) was found at 260∘C for 15 min and 5 wt% catalyst with a high heating value (HHV) of 19.29 ± 1.33 MJ kg−1. Nonetheless, the bio-oils produced without a catalyst at 300∘C and 15 min have higher HHV (27.63 ± 1.35 MJ kg−1) and are similar to Diesel fuel based on their H/C and O/C ratio. These results indicate that there is a potential trade-off between the bio-crude oil mass yield and HHV when using the catalyst.

Co-hydrothermally carbonized sewage sludge and lignocellulosic biomass: An efficiently renewable solid fuel

The objectives of this investigation were to elucidate the potential use of metal oxide-rich sewage sludge obtained from the treated brewery wastewater into a value-added solid fuel via co-hydrothermal carbonization process (co-HTC). Two residue biomass including spent coffee grounds and bagasse were supplied as co-combustion. The effects of sewage sludge and biomass addition on fuel properties were evaluated to optimize the best condition for biocoal-liked production. The chemical composition and mineral phase of solid product were further analyzed. Combustion kinetics analysis including activation energy (E) and pre-exponential factor (A) were derived from thermogravimetric analysis. It was found that the addition of coffee grounds and bagasse enhanced the fuel properties of the solid products, remarkably increasing high heating value (HHV) along with a low ash content, providing an increased fuel ratio of 0.34 – 1.01 and higher HHV as 14.29 – 22.19 MJ/kg. The highest rate of energy recovery was achieved when combining 75 wt% sewage sludge with 25 wt% spent coffee grounds. A substantial decrease of H/C and O/C atomic ratios was distinguished after bagasse addition compared to commercial lignite coal. It was also noticed that the relationship between the sewage sludge and biomass feedstocks during co-HTC is synergistic by increasing the amount of oxidative carbon during the char combustion stage and enhancing the degree of thermal stability. Moreover, it was also emphasized that during co-HTC some carbon and inorganic contents of sludge and lignocellulosic biomass were partially transferred into a liquid phase confirmed by TOC and ICP-OES analyses. A heavy metal leaching toxicity in a liquid product was also determined according to the USA-EPA standard. The combustion reactivity was improved, especially combustion reactivity of the biomass-sewage sludge-derived hydrochar. Interestingly, the hydrochar product was anticipated to possess enhanced safety and stability. Moreover, the co-combustion of hydrochar and coal improved the devolatilization properties and ignition of coal. This strategy revealed that co-hydrothermal process with biomass is a prospective approach to increase the value-added of sewage sludge feedstock as bicoal-like solid fuel.

The feasibility and performance of using producer gas as a gasifying medium

The gasification process in a 20-kW downdraft gasifier is investigated using Computational Fluid Dynamics. The research aims to examine the feasibility of air and producer gas co-injectionas a gasifying medium on the performance of the whole process. To this end, the effect of varying the injected amount of the producer gas on producer gas composition, emissions, H2 production, producer gas yield and higher heating value (HHV), the gasification, and carbon conversion efficiencies are reported. The results reveal promising findings for boosting the producer hydrogen amounts, and the corresponding heating values, with lower CO2 levels. The ratio of the injected producer gas (within the gasifying medium) to the total required amount of air for gasification is defined by z (eqn. (10)), and it is found that optimum z values are around (0.25–0.5). For the same working conditions of moisture content (MC), feedstock, and equivalence ratio (ER), the gasifying medium of z= (0.25–0.5) has higher HHV, gasification, and carbon conversion efficiencies than air gasification up to 33%, 31%, and 19% respectively. Additionally, for the same optimum range of z, it is found that the producer gas yield, and H2 production are higher than air gasification by 10%, and 34% respectively, with a reduction in CO2 by 18%. Consequently, the research presents a significant potential for higher yield, rich H2, and CO2-free syngas production, while demonstrating a promising novelty and technique that is applicable to any sort of the gasification units’ type and capacity.

Modelling and optimisation of intermediate pyrolysis synthesis of bio-oil production from palm kernel shell

A Palm Kernel Shell (PKS) is an enclosed shell obtained as residue from processing palm kernel. Its regarded as lignocellulosic biomass that serves as an abundant renewable energy source. The thermal and physicochemical behaviour was investigated, and results showed a low Fixed Carbon (FC) (22.60 wt%), high Volatile Matter (VM) (74.60 wt%), and high Higher Heating Value (HHV) of 19.78 MJ/kg. The elemental results showed the presence of C (48.70 wt%), H (5.58 wt%), N (0.23 wt%), O (45.02 wt%), and S (0.04 wt%). The fixed-bed pyrolysis reactor was utilised for the decomposition of the PKS to produce an optimum bio-oil of 47.10 wt% at temperature (520 °C), reaction time (15 min), nitrogen (175 cm3/min), particle size (0.70 mm), and heating rate (22.5 °C/min). The efficient Response Surface Methodology (RSM) via Central Composite Design (CCD) was employed to model and optimise the operating parameters. P<0.05, a high F-value for bio-oil makes the established model predicted, suitable, responsive, and reliable. The actual and predicted value for the quantity of bio-oil produced showed clearly that the data is reasonably in consonance with the predicted value. Screening with FT-IR revealed that the peak of 3339.7, 1416 cm−1 attributed to O–H stretching vibrations depicted the presence of alcohol and carboxylic acids, respectively, the resent, while the peak at 1636.3, 1274.7 was due to C–H bend and C–O stretch indicating the presence of aromatic compounds and aromatic ester respectively. The most significant element in the bio-oil obtained via Gas Chromatography–Mass Spectrometry (GC–MS) analysis is phenol, 9, 17 – octadecadienoyl, oleic acids, 2-cyclo pentane-1-one, and pent ethylene glycol are the by-products in the sample. Hence, the bio-oil produced is suitable for high-speed diesel engines, vehicle locomotion, powering heavy machines, marine equipment, manufacturing industries, and mining types of machinery. This is a significant contribution in the field of bio-oil production and application.

Microwave co-pyrolysis of kitchen food waste and rice straw: Effects of susceptor on thermal, surface, and fuel properties of biochar

In this research, microwave co-pyrolysis of kitchen food waste and rice straw under no susceptor, biochar susceptor, and ZnCl2 susceptor was undertaken to investigate the synergistic effects on biochar properties for energy application. The results showed that co-pyrolysis and the addition of susceptors significantly positively affected the thermochemical, fuel, thermal, and surface properties of biochar. Regardless of the susceptor conditions, blending kitchen food waste with rice straw effectively decreased the biochar yield (up to 2.14% and 6% for biochar and ZnCl2 susceptors, respectively) and abundance of –OH functional groups, but improved the chars’ thermal stability and surface area. Biochar produced at a ratio of 1:1 under ZnCl2 exhibited acceptably low ash content coupled with high higher heating value (20.550 MJ/kg), high energy yield (55.944%), and high fuel ratio (≤5.267) thereby demonstrating excellent fuel properties. These findings highlight the exceptional potential of co-pyrolytic biochar as a sustainable and eco-friendly energy source.

Enhancement of biofuel quality via conventional and catalytic co-pyrolysis of bamboo with polystyrene in a bubbling fluidized bed reactor: Coupled experiments and artificial neural network modeling

Experiments and artificial neural network modeling were performed to investigate the effect of operating parameters (temperature, fluidization velocity, and particle size) and catalysts (HZSM-5, red mud, Fe2O3, and dolomite) on co-pyrolysis of bamboo with polystyrene (PS) in a fluidized bed reactor for upgrading bio-oil. The synergistic effect was revealed by analyzing products via various analytical techniques and differences between theoretical and actual co-pyrolysis results. Under the H2-donor source from PS, co-pyrolysis reduced the O content while enhancing the content of aromatic hydrocarbons and higher heating value (HHV) of oil. Depending on the type of catalyst, characteristics and yield of the co-pyrolysis oil were affected along with the proposed reaction pathways. Dolomite was assessed as the most effective catalyst for improving oil quality, with the highest HHV (34.1 MJ/kg) and highest pH value (5.0). An artificial neural network using a back propagation algorithm in Matlab software was applied to predict the liquid yield and HHV of oil. The ANN15 model (15 neurons in the hidden layer) was found to be the best model in validating experimental data with mean deviations of 1.75 % for liquid yield and 0.87 % for HHV of oil.

Chicken meat and bone meal valorization by hydrothermal treatment and anaerobic digestion: Biofuel production and nutrient recovery

In this work, chicken meat and bones (C-MBM) waste is treated through a sequence of stages including hydrothermal treatment (HTT), nutrient recovery and anaerobic digestion, with the aim of evaluating their potential synergy as a circular economy approach. HTT was carried out at 170, 200 and 230 °C, under non-acidic and acidic conditions using 0.5 M HCl (HTT-A). Phosphorous from process water was recovered by chemical precipitation with the addition of a Mg salt, and the liquid effluent was anaerobically treated to degrade organic matter and produce a methane-rich biogas. Hydrochar obtained under non-acidic conditions presented poor combustion characteristics, while HTT-A yielded a bio-oil with high higher heating value (≈38 MJ/kg), good combustibility performance and high reactivity. More than 95% phosphorous (as phosphate) and almost 100% nitrogen (being 30% as NH4–N) content in C-MBM were solubilized in the process water upon HTT-A, while these nutrients were mainly retained in the hydrochar in non-acidic reactions. Chemical precipitation of P and NH4–N from HTT-A process water allowed recovering a crystalline solid identified as struvite and a struvite-apatite mixture, with negligible heavy metals content. High methane production (250–300 mL CH4/g CODadded) and organic matter removal (up to 75%) were achieved in the anaerobic tests. HTT proves to be a suitable treatment for material and energetic valorization of C-MBM, within a circular economy framework, which allows to obtain high value-added products (hydrochar/bio-oil, biofertilizers and biogas).

Employment of conventional and flash pyrolysis for biomass wastes from the textile industry with sustainable prospects

The textile industry generates millions of tons of waste annually, making this sector one of the most polluting in the world. The objective of this research was to study the energy potential of three industrial textile wastes of vegetable and animal origin: CW (card waste), SFW (short fibre waste) and W (wool), using conventional and flash pyrolysis at 500 °C and 750 °C. CW and SFW thermogravimetric profiles were very different from W. In general, the bio-oil yield was higher in the conventional and in the low-temperature flash pyrolysis (up to 55 %). The gas obtained by flash pyrolysis at 750 °C has higher flue gas content and lower CO2 content so their high heating value (HHV) is higher (up to 15.34 MJ/kg). Bio-oils obtained by flash pyrolysis at high temperature stood out for their higher HHV (>30 MJ/kg), with the highest value (34.15 MJ/kg) obtained from SFW waste. Both low temperature flash pyrolysis and conventional pyrolysis produce bio-oils that contain aromatic (35–48 %) and non-aromatic (18–34 %) organic compounds. Additionally, they have high levels of phenols and benzenes. High-temperature flash pyrolysis bio-oils are mainly composed of polycyclic aromatic hydrocarbons. The textile samples are suitable for an energetic valorisation, highlighting the best SWF behaviour.

Thermophysical Properties and Elemental Composition of Black Locust, Poplar and Willow Biomass

Biomass is currently the main renewable energy source (RES) in the EU, particularly in Poland. Solid biomass for energy purposes is primarily sourced from forests, the wood processing industry, and agriculture. A significant source of this energy feedstock could also be short-rotation woody crops (SRWCs), including black locust, poplar, and willow. Since numerous factors determine the SRWC biomass quality, the current study aimed at assessing biomass thermophysical properties and elemental composition depending on the plant species, soil enrichment procedure, and the plant harvest rotation over a consecutive 12-year period of cultivation. The characteristics under study, including the moisture content, ash content, volatile matter, fixed carbon, higher heating value (HHV), and the carbon, hydrogen, nitrogen, sulfur, and chlorine contents, were significantly differentiated by all the main factors, i.e., the SRWC species, the soil enrichment procedure, the harvest rotation, and the interactions between these factors. The SRWC species accounted for the highest percentage of the variation in the biomass moisture content, ash content, HHV, and nitrogen content, while the harvest rotation made the largest contribution to the variation in carbon, hydrogen, and chlorine contents. The black locust biomass was characterized by the significantly lowest moisture content (an average of 38.89%) and the highest sulfur content (an average of 0.033% DM), nitrogen content (an average of 0.91% DM), and chlorine content (an average of 0.032% DM). However, poplar was characterized by the highest HHV (an average of 19.84 GJ Mg−1 DM) and the highest moisture content (56.52% DM), carbon content (56.52% DM), and ash content (an average of 1.67% DM). Willow was characterized by the lowest ash content (an average of 1.67% DM), a medium moisture content, and the lowest nitrogen content (an average of 0.38% DM) and chlorine content (an average of 0.19% DM).