Biochar Mass Research Articles

Critical impact of biochar on hydroxyl radical generation during humin oxidation

The production of hydroxyl radicals (·OH) via reduced humin oxygenation is well established. As biochar is widely used in environmental restoration, its coexistence with humin in restored soils may affect ·OH generation due to its electron transfer ability. However, the role of biochar in ·OH generation remains largely unexplored. Herein, we investigated the ·OH generation by humin-biochar at different mass ratios. Our results indicated that biochar could significantly enhance the ·OH production by humin when the mass of humin exceeded that of biochar. Notably, when the mass ratio of humin to biochar was 50, the ·OH produced reached 67.3 μM, which is nearly 1.5 times the amount generated by humin alone (43.1 μM). Both single-electron and two-electron transfer pathways coexisted in ·OH generation by humin-biochar. C = O in humin were necessary conditions for the production of ·OH, while the presence of C = C in biochar promoted the generation of ·OH. Using graphene and carbon nanotubes both rich in C = C groups as the model compounds, humin-graphene and humin-carbon nanotubes produced ·OH at 122 μM and 98.8 μM, respectively, significantly higher than those generated by humin alone (43.1 μM). This result confirmed the promoting effect of aromatic C = C bonds on ·OH generation. By contrast, when the biochar mass was greater than or equal to that of humin, ·OH generation was inhibited due to the significant reduction of C = O. In this case, environmentally persistent free radicals (EPFRs) in biochar were the primary structures responsible for ·OH production. This study provides comprehensive insights for the first time into the influence of biochar on ·OH generation by humin and offers a new potential method for the green and efficient removal of pollutants.

Study of Methylene Blue dye adsorption onto biochar derived from Austrocylindropuntia subulata plant

Abstract The reuse of treated wastewater in drinking water supply and irrigation emerges as a potent solution to address water scarcity. Recent years have witnessed a growing interest in wastewater treatment using ecological, non-toxic, and biodegradable materials. In this study, Austrocylindropuntia subulata was employed for the first time to adsorb a synthetic dye, methylene blue. The feedstock underwent pyrolysis followed by chemical activation using orthophosphoric acid, resulting in the formation of biochar. Characterization through SEM, XRD, and FTIR analyses reveals that the biochar surface possesses functional groups such as alcohol and amide. Microscopic images highlight a diverse array of particle shapes and sizes, along with varying proportions of calcium and carbon in the biochar. Adsorption tests demonstrate that the optimal mass of biochar is 0.5g, ensuring a remarkable 99.8% adsorption of methylene blue dye within a 30 minutes contact time. The findings of this study underscore the compelling adsorbent capabilities of biochar derived from the Austrocylindropuntia subulata plant, suggesting its potential as a valuable resource in wastewater treatment.

Regulating bacterial dynamics by Mg-modified biochar addition to mitigate gaseous emissions during pig manure composting

Gaseous emissions (i.e. Greenhouse gases (CH4 and N2O) and NH3) were a serious environmental problem during composting. Magnesium salt could effectively reduce NH3 emission with the principle of struvite crystallization. Biochar, particularly modified biochar, could be served as a new type of adsorbent for gaseous reduction. In this study, Mg-modified biochars were successfully prepared with different magnesium to biochar mass ratios, and then used as additives in pig manure composting. Mg-modified biochars exhibited excellent properties in terms of functional groups, porous structure and composition. Adding Mg-modified biochar improved composting performance, and thus synergistically reduced CH4, N2O and NH3 emissions. Especially, Mg-modified biochar prepared with the magnesium to biochar mass ratio of 0.50 (MBC-0.50) achieved the best reduction effects during pig manure composting. Both additive and composting phases could influence the bacterial composition by regulating temperature, pH, electrical conductivity and moisture content. Besides biochar adsorption, NH3 could be further reduced with the formation of struvite crystallization (MgNH4PO4·6H2O) by adding Mg-modified biochar. Pristine and modified biochars inhibited the proliferation of denitrifying bacteria (e.g. Pseudoxanthomonas and norank-f-Methylococcaceae) and anaerobe methanogenic bacteria (e.g. Jeotgalibaca and Lactobacillus) to further mitigate N2O and CH4 emissions. Results from this study provided unique insights to the development of Mg-modified biochar additive for mitigating CH4, N2O and NH3 emissions during composting.

Microorganisms facilitated the saline‐alkali soil remediation by biochar: Soil properties, microbial communities, and plant responses

AbstractSaline‐alkali soil degradation is a significant environmental problem with a negative impact on sustainable agroforestry development. Therefore, efficient remediation methods are urgently required. A potential solution to this problem is using biochar produced from bamboo waste and inoculated with plant growth‐promoting microbes as cleaner production materials for saline‐alkali soil. The present study investigated the potential of combining biochar, microbes, and dwarf bamboo to improve saline‐alkali soil. Different application rates (1%, 3%, and 5% of soil mass) of biochar were added to coastal saline soil planted with dwarf bamboo (Pleioblastus argenteastriatus) in pot experiments. Soil physicochemical properties, microbial communities, and plant responses were systematically studied. Bamboo and microbial‐modified biochar effectively decreased soil pH and electrical conductivity and increased soil nutrient contents. Compared with untreated soil, the relative abundance of the dominant bacterial phyla Acidobacteria, Actinobacteria, and Chloroflexi, and dominant fungal phyla Basidiomycota increased after applying biochar and modified biochar. With the increase in application concentration, the antioxidant activities of modified biochar decreased, biochar peroxidase and catalase content decreased, and the malondialdehyde content of bamboo biochar and microbial‐modified bamboo biochar decreased. The biomass of bamboo with added biochar and modified biochar was significantly higher than that of untreated soil. Comprehensive correlation and redundancy analyses showed that the bacterial and fungal communities were greatly affected by soil factors, especially soil pH, electrical conductivity, total organic carbon, potassium, and sodium ions. The findings of this study suggest that 5% bamboo biochar and 3% modified biochar benefit soil remediation, improve the stress resistance of dwarf bamboo, and enhance plant growth. Therefore, combined biochar–microbe remediation has great potential for the sustainable improvement of saline‐alkali soil.

Straw pyrolysis for use in electricity storage installations

A concept has been proposed for an installation designed to store excess electricity periodically occurring on the grid. Excess electricity will be used for straw pyrolysis. The main pyrolysis product, gas, will be used to generate electricity using a combustion generator to feed back power into the grid during periods of shortage. The resulting biochar from the pyrolysis can be introduced into the soil to improve soil quality and play a significant role in carbon sequestration. The system uses an electrically heated reactor with a screw conveyor.To preliminarily assess the feasibility of this system, experiments were carried out using wheat straw at temperatures of 300, 400, 500, 600, and 700 °C for the pyrolysis reactor. The resulting gas-to-feedstock mass ratio ranged from 29.04 % at 300 °C to 52.7 % at 700 °C reactor temperature, the biochar mass yield ratio to feedstock varied from 39.41 % to 27.36 % (at 700 °C), and the pyrolysis liquid ranged from 31.55 % to 27.36 % (at 700 °C). The pyrolytic liquid contained a high water content relative to its mass, reaching up to 95.2 % at 700 °C, rendering it less suitable as an energy feedstock.At a reactor temperature of 700 °C, the energy value of the gas produced from the feedstock was twice that of the electricity used for the pyrolysis process. These results suggest the feasibility and operation of the proposed installation.

Biochar improved the solubility of triclocarban in aqueous environment: Insight into the role of biochar-derived dissolved organic carbon

Biochar as an effective adsorbent can be used for the removal of triclocarban from wastewater. Biochar-derived dissolved organic carbon (BC-DOC) is an important carbonaceous component of biochar, nonetheless, its role in the interaction between biochar and triclocarban remains little known. Hence, in this study, sixteen biochars derived from pine sawdust and corn straw with different physico-chemical properties were produced in nitrogen-flow and air-limited atmospheres at 300–750 °C, and investigated the effect of BC-DOC on the interaction between biochar and triclocarban. Biochar of 600∼750 °C with low polarity, high aromaticity, and high porosity presented an adsorption effect on triclocarban owing to less BC-DOC release as well as the strong π-π, hydrophobic, and pore filling interactions between biochar and triclocarban. In contrast and intriguingly, biochar of 300∼450 °C with low aromaticity and high polarity exhibited a significant solubilization effect rather than adsorption effect on triclocarban in aqueous solution. The maximum solubilization content of triclocarban in biochar-added solution reached approximately 3 times its solubility in biochar-free solution. This is mainly because the solubilization effect of BC-DOC surpassed the adsorption effect of biochar though the BC-DOC only accounted for 0.01–1.5 % of bulk biochar mass. Furthermore, the high solubilization content of triclocarban induced by biochar was dependent on the properties of BC-DOC as well as the increasing BC-DOC content. BC-DOC with higher aromaticity, larger molecular size, higher polarity, and more humic-like matters had a greater promoting effect on the water-solubility of triclocarban. This study highlights that biochar may promote the solubility of some organic pollutants (e.g., triclocarban) in aqueous environment and enhance their potential risk.

Use of waste marble powder for the synthesis of novel calcium-rich biochar: Characterization and application for phosphorus recovery in continuous stirring tank reactors

This study investigates—for the first time—the synthesis of a novel Ca-rich biochar (N–Ca–B) and its potential use for phosphorus (P) recovery from both synthetic solutions (SS) and treated urban wastewater (TUW) in a continuous stirring tank reactor (CSTR) mode. The novel biochar was synthesized by pyrolysis at 900 °C of a mixture composed of three different materials: animal biomass (poultry manure; PM), lignocellulosic waste (date palm fronds; DPFs), and abundant mineral waste (waste marble powder; WMP). Characterization of N–Ca–B showed that it has good textural properties: well-developed porosity, and high specific surface area. Furthermore, high calcium hydroxide (Ca(OH)2) and calcium oxides (CaO) nanoparticle loads were observed on the biochar surface. The dynamic CSTR assays indicated that the P recovery efficiency mainly depended on the biochar mass, P influent concentration, and, especially, the Ca content of the feeding solution. Owing to its richness in Ca cations, TUW exhibited the highest adsorbed P amount (109.2 mg g−1), i.e., about 14% larger than the SS. P recovery occurs through precipitation as hydroxyapatite, surface complexation, and electrostatic interactions with positively charged biochar particles. In real-world scenarios, CSTR systems can be applied as a tertiary treatment step in existing wastewater treatment plants (WWTPs). Decanted P-loaded biochar can be used in agriculture as a slow-release fertilizer instead of commercial products.

A novel solar disk chamber reactor for agricultural waste recycling and biochar production

The quality and properties of biochar are generally influenced by the nature of the raw materials and pyrolysis techniques. To assess the quality of sesame biochar production, a disc chamber reactor set on a solar parabolic dish concentrator was proposed as a modified slow pyrolysis technique. To evaluate the physicochemical characterizations of the produced biochar, two pyrolysis settings were used: 470 °C for 1 h (T1) and 440 °C for 2 h (T2) to produce biochar from sesame stalk feedstock (SS) using the proposed solar disk chamber reactor. Ash content, mass fraction of elements (C, H, and O%), pH, surface area, zeta potential, Fourier transform infrared (FTIR), and scanning electron microscope (SEM) were investigated. The results showed that the mass of T1 biochar decreased by 5% when compared to T2, while ash content, pH, fixed carbon, and volatile gases for both biochars were relatively close. The H/C and O/C molar ratios were below 1.00 and 0.4, respectively, indicating a loss of degradable polar contents and the formation of aromatic compounds. The surface area of T2 biochar was three times the surface area of T1, with the opposite trend in mean pore diameter. Two biochars showed the same FTIR peaks and SEM data, with small differences in their characteristics, demonstrating that pyrolysis time and temperature had a tight relationship. Both biochars showed approximately similar properties. The reactor’s efficiency is mainly affected by solar energy and atmospheric conditions during operation, which influence the average surface temperature. In Egypt, climatic conditions would be more favorable in the summer to improve the efficiency of parabolic solar dish concentrators for producing high-quality biochar.Graphical abstract

CO2 assisted Ca-based additives on pyrolytic characteristics and products from the co-pyrolysis of sewage sludge and biomass

In this study, the CO2-looping system was firstly attempted to build for exploring the effect of calcium-based (Ca-based) additives on pyrolytic characteristics and products in co-pyrolysis of sewage sludge (SS) and biomass. Then, an innovation method for the consumption of CO2 (CPCO2) evaluation was proposed and carried out in the CO2-looping system, in which it was evaluated based on the syngas volume and CO2 proportion. The results revealed that the addition of CaO and Ca(OH)2 could significantly improve CPCO2 by 21.2% in the co-pyrolysis of 500 ℃, while the CaCO3 addition decreased the CPCO2 by 1.0%. Besides, the co-pyrolysis temperature more than 700 ℃ would play more significant role on the CPCO2 than the addition of Ca-based additives. Then the effect of Ca-based types on biochar characteristics was also identified accompanied by the bio-oil composition. Results showed that the CaO and Ca(OH)2 additives not only increased biochar mass and pH, but also enhanced the dissolved organic carbon content and the variety of dissolved organic matter, and reduced the total HMs content. Meanwhile, it was 15 types of components that was identified in bio-oil by NIST mass spectral library, found that the intensity of heptadecanenitrile and estra-1,3,5(10)-trien-17 beta-ol was influenced by Ca-based additives. Moreover, the CaO and Ca(OH)2 played important roles for improving the CPCO2 in the CO2-looping system, which was further verified by Fact Sage. Finally, the mechanism for the Ca-based additives on CPCO2 was proposed at different co-pyrolysis temperatures. These findings can widen paths for biochar application and development of CO2 capture materials.

Effect of biochar content and particle size on mechanical properties of biochar-bioplastic composites

The recent increase in plastic use and the resulting pollution have put bioplastics in a strong position to expand. However, better understanding of bio-fillers and their effect on popular bioplastics, such as poly (lactic acid) (PLA), is required for this to occur. Biochar (BC), a stable form of carbon derived from high temperature conversion of organic material, has potential as a plastic filler. Although BC's effect on petroleum-based plastics has been widely studied, there are still major gaps in the literature surrounding BC use as a filler in PLA/starch composites. In this work, the effects of BC particle size and mass loading were examined when paired with a PLA/starch matrix. Mechanical and thermal testing was performed on composites that varied in filler loading (0–20 wt%), as well as particle size following a factorial design. At 20 wt% BC, the finer BC particles produced a drop in the viscosity, which could be attributed to degradation of polymer chains. Mechanical characterization showed that increasing the BC filler loading increased the stiffness of the composite. A similar effect was seen when decreasing the particle size of the BC at a constant loading. The most significant finding was that a combination of decreased particle size and filler loading of 5 wt%, increased the tensile strength by about 54% relative to the control (no BC) and slightly increased the elongation, thereby increasing the composites toughness. These results indicate that particle size and loading are important design considerations when using BC as a filler.

Adsorption Characteristics and Mechanism of Ammonia Nitrogen in Water by Nano Zero-valent Iron-modified Biochar

The adsorption performances of ammonia nitrogen (NH+4-N) in water by unmodified biochar are ineffective. In this study, nano zero-valent iron-modified biochar (nZVI@BC) was prepared to remove NH+4-N from water. The NH+4-N adsorption characteristics of nZVI@BC were investigated through adsorption batch experiments. The composition and structure characteristics of nZVI@BC were analyzed using scanning electron microscopy, energy spectrum analysis, BET-N2 surface area (SSA), X-ray diffraction, and FTIR spectra to explore the main adsorption mechanism of NH+4-N by nZVI@BC. The results showed that the composite synthesized at the iron to biochar mass ratio of 1:30 (nZVI@BC1/30) performed well in NH+4-N adsorption at 298 K. The maximum adsorption amount of nZVI@BC1/30 at 298 K was remarkably increased by 45.96% and reached 16.60 mg·g-1. The pseudo-second-order model and Langmuir model fitted well with the adsorption process of NH+4-N by nZVI@BC1/30. There was competitive adsorption between coexisting cations and NH+4-N, and the sequence of coexisting cations to the adsorption of NH+4-N by nZVI@BC1/30 was Ca2+> Mg2+> K+> Na+. The adsorption mechanism of NH+4-N by nZVI@BC1/30 could be mainly attributed to ion exchange and hydrogen bonding. In conclusion, nano zero-valent iron-modified biochar can improve the adsorption performance of NH+4-N and enhance the application potential of biochar in the field of nitrogen removal from water.

The Opportunity of Cyanobacterial Sludge and Bagasse Biomass Energy in the Biggest Change in a Century

Through orthogonal test and single factor experiment, biochar (BC) was ready by exploitation cyanobacterial sludge and bagasse to explore the potential of changing completely different energy at different carbonization temperatures and the result of Cr(VI) removal by BC. Biochar was prepared from dried cyanobacterial sludge and bagasse under 500 °C, 400 °C and 300 °C at 3.0 h, 2.5 h and 2.0 h under high temperature limited oxygen, respectively. Orthogonal experiments were used to conduct L9(34) three-factor and three-level experiments. Combined with single factor experiments, the optimal combination conditions for Cr(VI) removal were explored. Solid-state energy mainly was in the form of biochar yield. Higher temperature and content of biochar from bagasse had lower solid-state energy by biochar yield (44.00%±0.35%). Cyanobacterial sludge has wide application prospect and nice potential and application prospect in energy conversion. The dismissal of Cr(VI) with biochar was the primary to extend, and so decrease with the rise of charring temperature. The highest expulsion of Cr(VI) was attained once the mass quantitative relation of mixed biochar was 3:1. With a charring time of 2.5 hours, a charring temperature of 400 °C, and a biochar mass quantitative relation of 3:1, up to 98% of Cr(VI) was removed most effectively. Medium temperature biochar and biochar prepared from the mixture of cyanobacteria sludge and bagasse are beneficial to the production of solid energy. Cyanobacterial sludge-based biochar has broad application prospects, especially in energy conversion. In the orthogonal experiment, the sequence of influences of various factors on Cr(VI) removal rate was as follows: carbonation temperature > carbonation time > biochar ratio. The following were the ideal conditions for removing Cr(VI) from biochar: acieration temperature (400 °C), acieration time (2.5 hours), and biochar mass-quantity ratio of 3:1.

Assessment of the properties of aging biochar used as a substrate in constructed wetlands

Biochar has gained global recognition as an effective tool for environmental remediation, and is increasingly being used as an alternative substrate in constructed wetlands (CWs). While, most studies have focused on the positive effects of biochar for the pollutant removal in CWs, less is known about aging and longevity of the embedded biochar. This study investigated the aging and stability of biochar embedded in CWs post-treating the effluent of a municipal and an industrial wastewater treatment plant. Litter bags containing biochar were inserted into two aerated horizontal subsurface flow CWs (350 m2 each), and retrieved on several dates (8–775 days after burial) for assessment of weight loss/gain and changes in biochar characteristics. Additionally, a 525-day laboratory incubation test was conducted to analyze biochar mineralization. The results showed that there was no significant biochar weight loss over time, but a slight increase in weight (2.3–3.0%) was observed at the end, likely due to mineral sorption. Biochar pH remained stable except for a sudden drop at the beginning (8.6–8.1), while the electrical conductivity continued to increase (96–256 μS cm−1) throughout the experiment. The sorption capacity of the aged biochar for methylene blue significantly increased (1.0–1.7 mg g−1), and a change in the biochar's elemental composition was also noted, with O-content increasing by 13–61% and C content decreasing by 4–7%. Despite these changes, the biochar remained stable according to the criteria of the European Biochar Foundation and International Biochar Initiative. The incubation test also showed negligible biochar mass loss (<0.02%), further validating the stability of the biochar. This study provides important insights into the evolution of biochar characteristics in CWs.

Nutrient Recovery from Poultry Wastewater by Modified Biochar: An Optimization Study

In this work, we proposed and tested a method for utilizing agricultural waste and alum sludge as an effective adsorbent to treat poultry wastewater. The product was also targeted to be used as fertilizer for agriculture. Modified biochar was produced from crop residues, sludge from a water treatment plant, and magnesium salt. The produced biochar was characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, Brunauer-Emmett-Teller analysis, and X-ray diffraction. The adsorption of ammonia and phosphate in both synthetic and actual poultry wastewater by the produced biochar was conducted. The effect of experimental conditions such as N to P ratio, initial concentrations of ammonium and phosphate, pH, and the amount of biochar on the adsorption capacity for ammonia and phosphate were also investigated. The results from the experiment showed that the best adsorption capacities were 60.64 mgNH4+-N/g and 66.24 mgPO43--P/g, which were produced at the optimum conditions of N to P ratio of 1.25, initial concentration of 90 mg/L, pH 6, and biochar mass of 0.105 g. These results create an opportunity for the effective production of slow-release fertilizer from crop residues and alum sludge for ecological agriculture in the future.

Oxidation absorption of nitric oxide from flue gas using biochar-activated peroxydisulfate technology

Biochar-activated peroxydisulfate oxidation technology has received more and more attention due to its low metal ion leakage rate and low solid waste post-treatment requirement. In this paper, rice straw biochar-activated peroxydisulfate oxidation technology is used for the first time to oxidize nitric oxide (NO) from flue gas through inducing free radicals. The mechanism of NO oxidation removal is mainly explored. The main factors affecting NO removal, removal products and free radicals are also systematically studied. Results show that the main product of NO oxidation removal is NO3− and no extra by-product is formed. ·OH is identified as the first important free radical for oxidizing NO, while SO4−· is determined to be the second important free radical for oxidizing NO. Peroxydisulfate oxidation only plays a minor supplementary role in NO removal. Increasing rice straw biochar mass concentration and operation temperature promote NO removal. Increasing NO concentration and solution pH value are found to be harmful to NO removal. Increasing peroxydisulfate concentration first increases and then decreases NO removal efficiency. Under optimized process parameters, the maximum NO removal efficiency reaches 95.2%.

Characterization of biochar produced from Al Ghaf Tree for CO2 Capture

Climate change, global warming, and rise in water levels are environmental problems caused by the high emissions of greenhouse gases, and the most harmed one is carbon dioxide. Biochar is a material produced by thermochemical conversions with oxygen-depleted conditions of organic materials, and this process calls pyrolysis. Recently, it has been evaluated as a carbon dioxide capture, and its porous structure, structural properties, and production methods are easy. Al Ghaf (Prosopis cineraria) tree is one of the United Arab Emirates’ national trees with a wide range of intriguing properties, including high nutritional value, medicinal/pharmaceutical potential, and biosorption. This paper focuses on the biochar synthesized from three parts of the Al Ghaf tree: leaves, roots, and branches, to determine which part can achieve the maximum carbon dioxide capture. The ability of the produced biochar to capture carbon dioxide was tested through direct gas–solid​ interaction inside an integrated fluidized bed reactor. The carbon dioxide adsorption capacity was expressed by two methods related to (a) the loaded biochar mass and (b) the total amount of carbon dioxide fed to the reactor. The carbon dioxide adsorption capacity results concerning the loaded mass were 6.88%, 5.50%, and 3.63% for leaves, roots, and branches, respectively. At the same time, the results based on the total amount of carbon dioxide fed were 65.5%, 58.7%, and 37.7% for leaves, roots, and branches, respectively. Such results were confirmed by the physicochemical characteristics of the synthesized biochar using Scanning Electron Microscopy with Energy Dispersive X-ray Analysis, Thermogravimetric analysis (TGA), and X-ray diffraction analysis. Al Ghaf tree requires further study and inquiry to identify the most appropriate applications.

Biochar Derived from Sesbania sesban Plant as a Potential Low-Cost Adsorbent for Removal of Methylene Blue

In this study, biochar made from the Sesbania sesban plant, under slow pyrolysis at 300°C was used to adsorb methylene blue (MB) in aqueous solution. The biochar properties were clarified by diverse analytical methods such as FTIR, SEM, and BET. The results indicated that the surface of biochar was relatively smooth, had porous texture, and stacked evenly. In addition, the biochar had a large specific surface area of 561.8 m2/g and the pHpzc value was 6.9. The effect of adsorbent dosage, initial pH, contact time, and concentration of dye solution on biochar were investigated. The optimum conditions for MB adsorption were found at the MB concentration of 50 mg/L, initial pH of 11, biochar mass of 0.6 mg, and contact time of 30 min. Under these optimal conditions, MB dye removal efficiency was above 90%. Adsorption isotherm data were fitted with the Langmuir isotherm model (R2=0.897) suggesting the adsorption was monolayer, and its maximum adsorption capacity was about 6.6 mg/g. The adsorption kinetic models showed that the linear pseudo-second-order by R2=0.999 was well fitted. The results indicated the enormous potential of Sesbania sesban plant to produce biochar as a low-cost and rather high-effective adsorbent for dye removal from wastewater as well as water quality improvement.

The Effect of Activation on the Structure of Biochars Prepared from Wood and from Posidonia Oceanica: A Spectroscopic Study

The structure of two biochars and of their activated carbons was investigated by Electron Paramagnetic Resonance, Solid State Nuclear Magnetic Resonance, and Fourier Transform Infrared spectroscopies, together with X-ray diffraction and nitrogen adsorption/desorption isotherm measurements. The biochars were obtained from wood and Posidonia Oceanica by slow pyrolysis up to 600 °C, whereas the activated carbons were prepared from the biochars by impregnation with KOH, heating up to 800 °C. Two different KOH:biochar mass ratios were tested in the case of Posidonia, namely 4:1 and 2:1, while only the 4:1 ratio was used for wood. When the larger ratio was used, activation significantly increased the microporosity of the starting biochar, also creating bottle-neck pores not accessible to water molecules, and induced the formation of larger condensed aromatic networks arranged in interconnected conducting domains. In the case of Posidonia, activation using the 2:1 ratio mainly created mesopores and induced an increase in organic radical content by almost four orders of magnitude. This huge increase was related to the presence of minerals in the starting biochar.

Pyrolysis and gasification integrated process of empty fruit bunch for multi-biofuels production: Technical and economic analyses

The use of renewable energy sources has been promoted with concern about limited fossil fuels and increased environmental impact. Empty fruit bunch (EFB), which is a valuable biomass residual from palm oil milling processes, is one of the most promising renewable energy sources that can be used to increase the monetary value of EFB through the pyrolysis and gasification integrated process for multi-biofuels production. This work aims to perform technical and economic analyses of the pyrolysis and gasification integrated process using EFB for multi-biofuels production. Firstly, the pyrolysis and gasification integrated process model is developed by using Aspen Plus simulator and employed to determine optimal conditions through a parametric analysis. Then, the design of a heat exchanger network is also incorporated to enhance the energy efficiency of the process using Aspen Energy Analyzer. Finally, the key economic performance indicators, i.e., payback period (PB), net present value (NPV), and internal rate of return (IRR), of the process are analyzed using Aspen Process Economic Analyzer. The results show that the integrated process should be operated at steam to biochar mass ratio of 2.7, gasifier temperature of 900 °C, steam to syngas mass ratio of 3.0, and WGS temperature of 240 °C to produce the maximum hydrogen, gases, gasoline, naphtha, kerosene and diesel at 140, 290, 657, 729, 298 and 811 kg h−1, respectively. Furthermore, in terms of heat integration, the minimum hot and cold utilities are required at 21,554 and 5,247 MJ h−1, respectively. The economic analysis results indicate that the proposed process is economically feasible and attractive with 5.98 years of PB, $ 249,951,964 of NPV, and 22% of IRR.

Inclusion of biochar in a C dynamics model based on observations from an 8-year field experiment

Abstract. Biochar production and application as soil amendment is a promising carbon (C)-negative technology to increase soil C sequestration and mitigate climate change. However, there is a lack of knowledge about biochar degradation rate in soil and its effects on native soil organic carbon (SOC), mainly due to the absence of long-term experiments performed in field conditions. The aim of this work was to investigate the long-term degradation rate of biochar in an 8-year field experiment in a poplar short-rotation coppice plantation in Piedmont (Italy), and to modify the RothC model to assess and predict how biochar influences soil C dynamics. The RothC model was modified by including two biochar pools, labile (4 % of the total biochar mass) and recalcitrant (96 %), and the priming effect of biochar on SOC. The model was calibrated and validated using data from the field experiment. The results confirm that biochar degradation can be faster in field conditions in comparison to laboratory experiments; nevertheless, it can contribute to a substantial increase in the soil C stock in the long term. Moreover, this study shows that the modified RothC model was able to simulate the dynamics of biochar and SOC degradation in soils in field conditions in the long term, at least in the specific conditions examined.