Combustion of thermochemically torrefied sugar cane bagasse

Effects of water washing and KOH activation for upgrading microalgal torrefied biochar

Torrefaction is an effective pathway for microalgal solid biofuel upgrading, and alkali metal activation is also an efficient method to enhance fuel properties. This study explores the comparison of torrefaction alone and KOH activation combined with torrefaction to determine a better operation for biochar production from the microalga Nannochloropsis Oceanica. The results indicate that the HHV ranges of KOH-activated biochar and unactivated biochar are 25.611-32.792 MJ·kg-1 and 25.024-26.389 MJ·kg-1, respectively. Furthermore, KOH-activated biochar is better than unactivated biochar, with less residue, broader pyrolysis and combustion temperature ranges, higher elemental carbon, and less combined carbon. Moreover, KOH-activated biochar is close to the unactivated one from the viewpoint of expense calculation and life cycle assessment and thus possesses a better comprehensive performance. Overall, KOH activation is an efficient method for upgrading microalgal solid biofuel. The results are conducive to exploring further modification of microalgal solid biofuel production with better properties, thus leading to a greener and more efficient approach for upgrading fuel performance.

Catalytic torrefaction effect on waste wood boards for sustainable biochar production and environmental remediation

Wood boards used in construction are generally treated with toxic chemicals, making them unsuitable for further use and causing environmental pollution. This study evaluates the possibility of using catalytic torrefaction as a pretreatment to improve wood pyrolysis and combustion for greener biochar production. Waste beech boards were impregnated with different K2CO3 solutions (0-0.012 M), then torrefied between 5 and 60 min at 275 °C. The ICP-AES showed that the board's surface held more potassium than the core. Torrefaction coupled with potassium decreased the C-O and -OH stretches. Thermogravimetric analysis of torrefied wood showed that the board's internal heating degraded the core more than the surface. The exothermic reactions made potassium's catalytic action more efficient in the core. Interactions between the potassium content and torrefaction duration decreased the pyrolysis' maximum devolatilization temperature. During combustion, potassium decreased the ignition temperature by up to 9% and 3% at the surface and core, respectively, while the torrefaction increased it. The catalytic torrefaction significantly decreased the devolatilization peak during combustion, thus making the wood's combustion similar to that of coal, having only the char oxidation step. These findings highlight the advantages and challenges of waste wood's catalytic-torrefaction for biochar production to reduce environmental pollution.

Torrefaction interpretation through morphological and chemical transformations of agro-waste to porous carbon-based biofuel

In the current study, two agro-waste lignocellulosic corncob (CC) and rice husk (RH) were thermally torrefied at 200-300 °C into a porous carbon-enriched biofuel. The scanning electron microscopy (SEM) of produced biofuel confirmed the rounded, homogenous, and spherical structure of the produced biofuels with higher porosity at a temperature between 250 and 300 °C with 60 min retention time. Brunauer-Emmett-Teller (BET) analysis indicated the high surface area (CC: 1.19-2.87 m2 g-1 and RH: 1.22-2.67 m2 g-1) and pore volume (CC: 1.23-2.81 ×10-3 m3 g-1 and RH: 1.46-2.58 ×10-3 m3 g-1). Crystallinity index decline percent (CC= 62.87% and RH=57.10%) estimated thermal stability and rise in amorphous cellulose reformation during (250-300 °C)/60 min that would efficiently hydrolyze during oxidative pyrolysis carbon reactive sites the rise in surface area and total pore's volume, having higher conversion rate as compared to raw materials. Carbon content was upgraded to 94% by eliminating hydrogen and oxygen from lignocellulosic agro-waste to produce energy-dense CC and RH. The lignin macromolecule transformation extent was estimated by O/C trend, which was equal to 63% and 47% for CC and RH, respectively, at 300 °C for 60 min. Due to low bulk density and pre-grinding energy requirements, torrefied biofuel with decomposed fibrous structure have lower transportation costs.

Kinetic Mechanisms and Emissions Investigation of Torrefied Pine Sawdust Utilized as Solid Fuel by Isothermal and Non-Isothermal Experiments

This study comprehensively investigated the utilization of torrefied pine sawdust (PS) as solid fuels, involving the characterization of torrefied PS properties, the investigation of combustion behaviors and kinetic mechanisms by non-isothermal experiments, and the evaluation of emissions during isothermal experiments. Results show that torrefaction significantly improved the quality of the solids. The upgradation of torrefied PS properties then further enhanced its combustion performance. For the kinetics mechanisms, degradation mechanisms and diffusion mechanisms were respectively determined for the volatile combustion and the char combustion by using both Coats-Redfern (CR) and Freeman-Carroll (FC) methods. Further, after torrefaction, the emission of NO for volatile combustion reduced while it increased for char combustion. An inverse relationship was found between the conversion of fuel-N to NO and the nitrogen content in the torrefied samples. This study provided comprehensive insights for considering torrefaction as a pretreatment technique for PS utilization as a solid fuel.

Influence of Torrefaction on Biomass Devolatilization

The present study investigated the effect of torrefaction on the devolatilization characteristics of three lignocellulosic biomass feedstocks with different degrees of torrefaction together with their parent fuel, palm kernel shell, a residue of palm oil production. Thermogravimetric (TG) analysis was employed for the study of the devolatilization process. A kinetic model based on three parallel reactions corresponding to biomass chemical components was applied to TG data and used for the evaluation of reaction kinetics. The results obtained indicated that the torrefaction process led to a significant reduction of the hemicellulose content of the investigated biofuels. The characterization of volatile products evolved during biofuel devolatilization was performed by TG analysis coupled with Fourier transform infrared spectroscopy. The emission characteristics and the yields of the main volatile products were assessed. Specific linear correlations between volatile yields and the torrefaction degree could be observed.

Impacts of non-oxidative torrefaction conditions on the fuel properties of indigenous biomass (bagasse)

Biomass is considered as the largest renewable energy source in the world. However, some of its inherent properties such as hygroscopicity, lower energy content, low mass density and bio-degradation on storage hinder its extensive application in energy generation processes. Torrefaction, a thermochemical process carried out at 200-300°C in a non-oxidative environment, can address these inherent problems of the biomass. In this work, torrefaction of bagasse was performed in a bench-scale tubular reactor at 250°C and 275°C with residence times of 30, 60 and 90 mins. The effects of torrefaction conditions on the elemental composition, mass yield, energy yield, oxygen/carbon (O/C) and hydrogen/carbon (H/C) ratios, higher heating values and structural composition were investigated and compared with the commercially available 'Thar 6' and 'Tunnel C' coal. Based on the targeted mass and energy yields of 80% and 90% respectively, the optimal process conditions turned out to be 250°C and 30 mins. Torrefaction of the bagasse conducted at 275°C and 90 min raised the carbon content in bagasse to 58.14% and resulted in a high heating value of 23.84 MJ/kg. The structural and thermal analysis of the torrefied bagasse indicates that the moisture, non-structural carbohydrates and hemicellulose were reduced, which induced the hydrophobicity in the bagasse and enhanced its energy value. These findings showed that torrefaction can be a sustainable pre-treatment process to improve the fuel and structural properties of biomass as a feedstock for energy generation processes.

Influence of biomass components, temperature and pressure on the pyrolysis behavior and biochar properties of pine nut shells

The aim of this work was to compare the yields, proximate composition, structure and surface morphology of biochar derived from lignin, cellulose, hemicellulose and pine nut shell (PNS) at 400-700 ℃. PNS biochars obtained at different pyrolysis pressures in the range of 0.1-2.0 MPa were also studied. The results indicate that the interactions of lignin, cellulose and hemicellulose have smaller effects on the ash content, yield and higher heating value (HHV) of the biochar than they do on the fixed carbon and volatile matter contents. Increasing the pyrolysis temperature improves the HHV of the biochar, and increasing the pyrolysis pressure enhances the biochar yield, surface functional groups and combustion characteristics. The kinetic data for Pb²⁺ adsorption are best fitted by a pseudo-second-order model, indicating a chemisorption-controlled process. The PNSB550 and PNSB1.0 data are optimally fit by the Freundlich and Langmuir models, respectively. The maximum Pb²⁺ adsorption capacity is 237.3 mg/g.

Use of cork granules as an effective sustainable material to clean-up spills of crude oil and derivatives

The use of cork granules for cleaning up crude oil or oil derivative spills and further oil recovery appears as a promising option due to their unique properties, which allow a high oil sorption capacity, low water pickup and excellent reuse. The present work reports the effect of oil viscosity on cork sorption capacity by using five types of oils (lubricating oil, 5.7 g_oil g_cork^-1; heavy oil, 4.2 g_oil g_cork^-1; light oil, 3.0 g_oil g_cork^-1; biodiesel, 2.6 g_oil g_cork^-1; and diesel, 2.0 g_oil g_cork^-1). The cork sorption capacity for light petroleum was also evaluated as a function of temperature and sorbent particle size. Additionally, improvements on oil recovery from cork sorbents by a mechanical compression process have been achieved as a result of a design of experiments (DOE) using the response surface methodology. Such statistical technique provided remarkable results in terms of cork sorbent reusability, as the oil sorption capacity was preserved after 30 cycles of sorption-squeezing steps. The sorbed oils could be removed from the sorbent surface, collected simply by squeezing the cork granules and further reused. The best operational region yielded near 80% oil recovery, using a cork mass of 8.85 g (particle size of 2.0-4.0 mm) loaded with 43.5 mL of lubricating oil, at 5.4 bar, utilising two compressions with a duration of 2 min each. Graphical abstract.

Effect of torrefaction on rice straw physicochemical characteristics and particulate matter emission behavior during combustion

In this work, the effects of different torrefaction temperatures and durations on the physicochemical properties of rice straw (RS), and the emission characteristic of PM₁₀ (particulate matter with aerodynamic diameters of ≤10 µm) during torrefied RS combustion, were investigated. Results indicate that the release of Cl and K, and decomposition of the organic matrix demonstrated a promoting effect during torrefaction. However, the removal of Cl and K did not reduce the emission of PM₁. The emission concentration of PM₁ and PM_1-10 generated from torrefied RS was enhanced, and the yields of PM_1-10 was much higher than those of PM₁. The concentrations of K and Cl in PM_1-10 increased with torrefaction temperature, combined with the microstructure, indicating that the torrefaction pretreatment promoted the heterogeneous condensation of KCl vapour to form PM_1-10.

Food loss and waste management in Turkey

Food waste can be an environmental and economic problem if not managed properly but it can meet various demands of a country if it is considered as a resource. The purpose of this report is to review the existing state of the field in Turkey and identify the potential of food waste as a resource. Food loss and waste (FLW) was examined throughout the food supply chain (FSC) and quantified using the FAO model. Edible FLW was estimated to be approximately 26milliontons/year. The amount of biodegradable waste was estimated based on waste statistics and research conducted on household food waste in Turkey. The total amount of biodegradable waste was found to be approximately 20milliontons/year, where more than 8.6milliontons/year of this waste is FLW from distribution and consumption in the FSC. Options for the end-of-life management of biodegradable wastes are also discussed in this review article.

Predictions of biochar production and torrefaction performance from sugarcane bagasse using interpolation and regression analysis

This study focuses on the biochar formation and torrefaction performance of sugarcane bagasse, and they are predicted using the bilinear interpolation (BLI), inverse distance weighting (IDW) interpolation, and regression analysis. It is found that the biomass torrefied at 275°C for 60min or at 300°C for 30min or longer is appropriate to produce biochar as alternative fuel to coal with low carbon footprint, but the energy yield from the torrefaction at 300°C is too low. From the biochar yield, enhancement factor of HHV, and energy yield, the results suggest that the three methods are all feasible for predicting the performance, especially for the enhancement factor. The power parameter of unity in the IDW method provides the best predictions and the error is below 5%. The second order in regression analysis gives a more reasonable approach than the first order, and is recommended for the predictions.

Polycyclic aromatic hydrocarbons on particulate matter emitted during the co-generation of bioenergy and biochar from rice husk

The aim of this study was to evaluate the emissions of polycyclic aromatic hydrocarbons (PAHs) bound to the particulate matter (PM) during the combustion of raw pyrolysis volatiles (bio-oil and pyrogas mixture) generated from the pyrolysis of rice husk. Five different raw pyrolysis volatiles were produced at varying pyrolysis temperatures (400-800°C) and subsequently combusted in a laboratory-scale, continuous pyrolysis-combustion facility at 850°C. 15 priority pollutant PAH levels in the resulting biochar, bio-oil, and PM were evaluated. Results showed that combustion of the raw pyrolysis volatiles produced at elevated pyrolysis temperatures resulted in greater concentrations of PM-bound PAHs (119% increase between 400 and 800°C) due to the increased PAH and oxy-aromatic content of the bio-oil fraction. Significantly increased benzo(a)pyrene (BaP) - equivalent toxicity of the biochar and PM was observed at elevated pyrolysis temperatures.