Combustion and fuel characterisation of wheat distillers dried grain with solubles (DDGS) and possible combustion applications

The present transition to a sustainable global energy system requires that biomass is increasingly combusted for heat and power production. Agricultural fuels considered include alkali-rich fuels with high phosphorus content. One such fuel is wheat distiller’s dried grain with solubles (wheat DDGS) from wheat-based ethanol production. Further increases in ethanol production may saturate the current market for wheat DDGS as livestock feed, and fuel uses are therefore considered. Fuel properties of wheat DDGS have been determined. The ash content (5.4 ± 1.6 %wt d.s.) is similar to many agricultural fuels. In comparison to most other biomass fuels the sulphur content is high (0.538 ± 0.232 %wt d.s.), and so are the contents of nitrogen (5.1 ± 0.6 %wt d.s.), phosphorus (0.960. ± 0.073 %wt d.s.) and potassium (1.30 ± 0.35 %wt d.s.). To determine fuel-specific combustion properties, wheat DDGS and mixes between wheat DDGS and logging residues (LR 60 %wt d.s. and DDGS 40 %wt d.s.), and wheat straw (wheat straw 50 %wt d.s., DDGS 50 %wt d.s.) were pelletized and combusted in a bubbling fluidised bed combustor (5 kW) and in a pellets burner combustor (20 kW). Pure wheat DDGS powder was also combusted in a powder burner (150 kW). Wheat DDGS had a high bed agglomeration and slagging tendency compared to other biomass fuels, although these tendencies were significantly lower for the mixture with the Ca-rich LR, probably reflecting the higher first melting temperatures of K–Ca/Mg-phosphates compared to K-phosphates. Combustion and co-combustion of wheat DDGS resulted in relatively large emissions of fine particles (<1 μm) for all combustion appliances. For powder combustion PMtot was sixteen times higher than from softwood stem wood. While the Cl concentrations of the fine particles from the the mixture of LR and wheat DDGS in fluidised bed combustion were lower than from combustion of pure LR, the Cl- and P-concentrations were considerably higher from the wheat DDGS mixtures combusted in the other appliances at higher fuel particle temperature. The particles from powder combustion of wheat DDGS contained mainly K, P, Cl, Na and S, and as KPO3 (i.e. the main phase identified with XRD) is known to have a low melting temperature, this suggests that powder combustion of wheat DDGS should be used with caution. The high slagging and bed agglomeration tendency of wheat DDGS, and the high emissions of fine particles rich in K, P and Cl from combustion at high temperature, mean that it is best used mixed with other fuels, preferably with high Ca and Mg contents, and in equipment where fuel particle temperatures during combustion are moderate, i.e. fluidised beds and possibly grate combustors rather than powder combustors

Synthesis of sustainable mesoporous sulfur-doped biobased carbon with superior performance sodium diclofenac removal: Kinetic, equilibrium, thermodynamic and mechanism

Over the last years, the strategy of employing inevitable organic waste and residue streams to produce valuable and greener materials for a wide range of applications has been proven an efficient and suitable approach. In this research, sulfur-doped porous biochar was produced through a single-step pyrolysis of birch waste tree in the presence of zinc chloride as chemical activator. The sulfur doping process led to a remarkable impact on the biochar structure. Moreover, it was shown that sulfur doping also had an important impact on sodium diclofenac (S-DCF) removal from aqueous solutions due to the introduction of S-functionalities on biochar surface. The adsorption experiments suggested that General and Liu models offered the best fit for the kinetic and equilibrium studies, respectively. The results showed that the kinetic was faster for the S-doped biochar while the maximum adsorption capacity values at 318 K were 564 mg g−1 (non-doped) and 693 mg g−1 (S-doped); highlighting the better affinity of S-doped biochar for the S-DCF molecule compared to non-doped biochar. The thermodynamic parameters (ΔH0, ΔS0, ΔG0) suggested that the S-DCF removal on both adsorbents was spontaneous, favourable, and endothermic

Enhanced biobased carbon materials made from softwood bark via a steam explosion preprocessing step for reactive orange 16 dye adsorption

The growing textile industry produces large volumes of hazardous wastewater containing dyes, which stresses the need for cheap, efficient adsorbing technologies. This study investigates a novel preprocessing method for producing activated carbons from abundantly available softwood bark. The preprocessing involved a continuous steam explosion preconditioning step, chemical activation with ZnCl2, pyrolysis at 600 and 800 °C, and washing. The activated carbons were subsequently characterized by SEM, XPS, Raman and FTIR prior to evaluation for their effectiveness in adsorbing reactive orange 16 and two synthetic dyehouse effluents. Results showed that the steam-exploded carbon, pyrolyzed at 600 °C, obtained the highest BET specific surface area (1308 m2/g), the best Langmuir maximum adsorption of reactive orange 16 (218 mg g−1) and synthetic dyehouse effluents (>70 % removal) of the tested carbons. Finally, steam explosion preconditioning could open up new and potentially more sustainable process routes for producing functionalized active carbons

Gasification of pure and mixed feedstock components: Effect on syngas composition and gasification efficiency

The aim of this work was to investigate whether the use of individual tree components (i.e., stem wood, bark, branches, and needles of spruces) as feedstocks during oxygen blow gasification is more efficient than using mixtures of these components. Experiments were performed at three oxygen levels in an 18-kW oxygen blown fixed bed gasifier with both single and mixed component feedstocks. The composition of the resulting syngas and the cold gas efficiency based on CO and H-2 (CGE(fuel)) were used as response variables to evaluate the influence of different feedstocks on gasification performance. Based on the experimental results and data on the composition of similar to 26000 trees drawn from a national Swedish spruce database, multivariate models were developed to simulate gasifier performance under different operating conditions and with different feedstock compositions. The experimental results revealed that the optimal CGE(fuel) with respect to the oxygen supply differed markedly between the different spruce tree components. Additionally, the models showed that co-gasification of mixed components yielded a lower CGE(fuel )than separate gasification of pure components. Optimizing the oxygen supply for the average tree composition reduced the CGE(fuel) by 1.3-6.2% when compared to optimal gasification of single component feedstocks. Therefore, if single-component feedstocks are available, it may be preferable to gasify them separately because doing so provides a higher gasification efficiency than co-gasification of mixed components

High surface area activated carbon prepared from wood-based spent mushroom substrate for supercapacitors and water treatment

Edible white-rot fungi are commonly cultivated on wood-based substrates and selectively degrade lignin to a larger extent during their growth. Spent mushroom substrate (SMS) is produced in huge amounts by the mushroom industry and today there is a lack of proven methods to valorize this kind of biomass waste, which in most cases is landfilled or used as fuel. This study demonstrates that birch wood-based SMS from the cultivation of oyster mushrooms can be converted into high-quality activated carbon (AC) with an extremely high surface area of about 3000 m2 /g. These activated carbons showed good performance when used in electrodes for supercapacitors, with energy storage parameters nearly identical to AC produced from high-quality virgin birch wood. Moreover, AC produced from SMS showed high potential as an adsorbent for cleaning reactive orange-16 azo dye from aqueous solutions as well as contaminants from synthetic effluents and from real sewage water. The kinetics of adsorption were well represented by the Avrami fractional order model and isotherms of adsorption by the Liu model. The theoretical maximum reactive orange-16 adsorption capacities were approximately 519 mg/g (SMS-based carbon) and 553 mg/g (virgin birch-based carbon). The removal of contaminants from synthetic effluents made of different dyes and inorganic compounds was around 95% and 83% depending on the effluent composition. The removal of contaminants from raw sewage water was around 84%, and from treated sewage water was around 68%. Overall, the results showed that activated carbon prepared from waste generated during cultivation of white-rot fungi is as good as activated carbon prepared from high-quality virgin wood

Activated carbons with extremely high surface area produced from cones, bark and wood using the same procedure

Activated carbons have been previously produced from a huge variety of biomaterials often reporting advantages of using certain precursors. Here we used pine cones, spruce cones, larch cones and a pine bark/wood chip mixture to produce activated carbons in order to verify the influence of the precursor on properties of the final materials. The biochars were converted into activated carbons with extremely high BET surface area up to similar to 3500 m(2) g(-1) (among the highest reported) using identical carbonization and KOH activation procedures. The activated carbons produced from all precursors demonstrated similar specific surface area (SSA), pore size distribution and performance to electrodes in supercapacitors. Activated carbons produced from wood waste appeared to be also very similar to "activated graphene" prepared by the same KOH procedure. Hydrogen sorption of AC follows expected uptake vs. SSA trends and energy storage parameters of supercapacitor electrodes prepared from AC are very similar for all tested precursors. It can be concluded that the type of precursor (biomaterial or reduced graphene oxide) has smaller importance for producing high surface area activated carbons compared to details of carbonization and activation. Nearly all kinds of wood waste provided by the forest industry can possibly be converted into high quality AC suitable for preparation of electrode materials

Preparation of highly porous nitrogen-doped biochar derived from birch tree wastes with superior dye removal performance

Heteroatom doping is a highly effective strategy that can be used to modify carbonaceous adsorbents to improve their chemical reactivity and increase their adsorptive properties. Herein, a simple method is reported for the preparation of nitrogen-doped biochar using a natural and abundant biowaste from birch trees and melamine as a nitrogen dopant for the adsorption of Acid red 18 (AR-18) dye from water. The doped biochars were also characterized for their performance during the treatment of synthetic effluents. The physicochemical characterization results showed that the N-doping process provoked remarkable chances on the biochar morphology, pore structure, and surface functionalities. N-doped biochar showed abundant nitrogen functional groups with 5.4 % of N in its structure while non-doped carbon showed traces with 0.47 %. Moreover, the specific surface area of doped biochar was dominated by mesopores (86.4 %) while non-doped was dominated by micropores (67.8 %). Raman analysis showed that the incorporation of N created more defects in the biochar structure. The adsorption experiments showed that the N-doping boosted the biochar adsorptive performance. The maximum adsorption capacity of the doped biochar was 545.2 mg g−1, while the non-doped exhibited 444.5 mg g−1, i.e., an increase of 22.6 %. The kinetic and equilibrium studies showed that Avrami fractional order and Liu models were the most suitable for describing the experimental AR-18 dye adsorption data. The equilibrium parameters were found to obey a nonlinear relationship with the temperature. Since the biochars are highly porous, pore filling was the main adsorption mechanism, however; AR-18 dye removal suggests that interactions such as electrostatic, hydrogen bonds, Lewis acid-base, and π-π between the adsorbent and the dye are involved. The thermodynamic studies showed that the removal of the AR-18 dye from the solution is dependent on temperature, exothermic, and spontaneous. The N-doped biochar showed excellent removal performances of contaminants from synthetic effluents confirming their high efficiency for color removal. This research shows that N-doping is an efficient strategy to design effective, low-cost, and sustainable adsorbents to remediate dye contamination in wastewater

Collecting eco-evolutionary data in the dark : Impediments to subterranean research and how to overcome them

Caves and other subterranean habitats fulfill the requirements of experimental model systems to address general questions in ecology and evolution. Yet, the harsh working conditions of these environments and the uniqueness of the subterranean organisms have challenged most attempts to pursuit standardized research. Two main obstacles have synergistically hampered previous attempts. First, there is a habitat impediment related to the objective difficulties of exploring subterranean habitats and our inability to access the network of fissures that represents the elective habitat for the so-called "cave species." Second, there is a biological impediment illustrated by the rarity of most subterranean species and their low physiological tolerance, often limiting sample size and complicating laboratory experiments. We explore the advantages and disadvantages of four general experimental setups (in situ, quasi in situ, ex situ, and in silico) in the light of habitat and biological impediments. We also discuss the potential of indirect approaches to research. Furthermore, using bibliometric data, we provide a quantitative overview of the model organisms that scientists have exploited in the study of subterranean life. Our over-arching goal is to promote caves as model systems where one can perform standardized scientific research. This is important not only to achieve an in-depth understanding of the functioning of subterranean ecosystems but also to fully exploit their long-discussed potential in addressing general scientific questions with implications beyond the boundaries of this discipline.Peer reviewe

Shiitake spent mushroom substrate as a sustainable feedstock for developing highly efficient nitrogen-doped biochars for treatment of dye-contaminated water

Edible white-rot mushrooms are organisms that are cultivated at an industrial scale using wood-based substrates. The mushroom industry has an estimated annual production of 34 Mt of edible mushrooms, and approximately 70 wt% of the substrate is left as waste known as spent mushroom substrate (SMS). The huge volumes of SMS generated by mushroom farms hinder proper recycling, meaning that combustion or open-field burning are common disposal practices. This paper shows a concept that could help reduce the environmental impact of the mushroom industry. SMS from the cultivation of shiitake mushroom was used as a carbon precursor for the production of nitrogen-doped activated biochar that was used to remove reactive orange-16 (RO-16) azo dye from water, as well as contaminants from two synthetic effluents and real sewage water. Melamine was used as a nitrogen dopant and phosphoric acid as an activating agent. Samples without the addition of melamine were used for comparison. The doping/impregnation process was carried out in one-step, followed by pyrolysis at 700 and 900 ◦C for 1 h. BET, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) were used for the characterization of the biochars. The specific surface area of the doped samples was slightly lower, i.e., 1011 m2 /g (SMS-700 ◦C), 810 m2 /g (SMS-700 ◦C + N), 1095 m2 /g (SMS900 ◦C), and 943 m2 /g (SMS-900 ◦C + N). Raman spectroscopic analysis showed that the N-doped biochars had more defective carbon structures than the non-doped ones. XPS analysis showed that doping with melamine led to the formation of N-functionalities on the surface of the biochar particles. The kinetics of adsorption were well represented by the Avrami model. The adsorption isotherms were well-fitted by the Liu model. The maximum adsorption capacities (qmax) of RO-16 were much higher for the N-doped biochars, i.e., 120 mg/g (SMS-700 ◦C), 216 mg/g (SMS-700 ◦C + N), 168 mg/g (SMS-900 ◦C), and 393 mg/g (SMS-900 ◦C + N). N-doped biochar samples were more effective for the removal of contaminants from synthetic effluents and sewage water. Ndoped biochar produced at 900 ◦C showed good recyclability. This work concludes that SMS is a valuable waste that could be used for the production of activated carbon and that N-doping helped to improve the adsorption performance to a great extent

Microalgae biomass as a sustainable precursor to produce nitrogen-doped biochar for efficient removal of emerging pollutants from aqueous media

Preparing sustainable and highly efficient biochars as adsorbents remains a challenge for organic pollutant management. Herein, a novel nitrogen-doped carbon material has been synthesized via a facile and sustainable single-step pyrolysis method using a wild mixture of microalgae as novel carbon precursor. Phosphoric acid (H3PO4) was employed as activation agent to generate pores in the carbon material. In addition, the effect of melamine (nitrogen source) was evaluated over the biochar properties by the N-doping process. The results showed that the biochar’s specific surface area (SSA) increased from 324 to 433 m2 g− 1 with the N-doping process. The N-doping process increased the percentage of micropores in the biochar structure. Chemical characterization of the biochars indicated that the N-doping process helped to increase the graphitization process of the biochar and the contents of oxygen and nitrogen groups on the carbon surface. The biochars were successfully tested to adsorb acetaminophen and treat two synthetic effluents, and the N-doped biochar presented the highest efficiency. The kinetics and equilibrium data were well represented by the General-order model and the Liu isotherm model, respectively. The maximum sorption capacities attained were 101.4 and 120.7 mg g− 1 for the non-doped and doped biochars, respectively. The acetaminophen adsorption mechanism suggests that the pore-filling was the dominant mechanism for acetaminophen uptake. The biochars could efficiently remove up to 74% of the contaminants in synthetic effluents