Feedstock Type Research Articles

Thermal Response of Biocarbon-Filled Hemp Fiber-Reinforced Bioepoxy Composites.

We investigated the thermal conductivity of materials based on pyrolysis temperature, filler loading, filler size, and type of biomass feedstock. Hemp stalk and switchgrass were pyrolyzed at 450, 550, and 650 °C and crushed into 50, 75, and 100 μm particle sizes. Biocarbon fillers (10, 15, and 20 wt %) were added to the bioepoxy polymer matrix. The study showed increased filler loading and particle size increased thermal conductivity-the biocomposite samples with 20 wt % filler loading of 100 μm particle size of the biocarbon obtained at 650 °C showed the maximum thermal conductivity in both hemp biocarbon-filled composites (0.59 W·m-1·K-1) and switchgrass-filled composites (0.58 W·m-1·K-1) with the highest flame time. Biocarbon in biofiber-reinforced polymer composites can improve thermal conductivity and extend the flame time. These findings significantly contribute to developing hemp-based bioepoxy composite materials for thermal applications in various fields. These include insulating materials for buildings and thermal management systems, energy-efficient applications, and help in material selection and product design with a positive environmental impact.

Effect of Bamboo biochar on strength and water retention properties of low plastic clay and silty sand

Biochar is a carbon-rich stable product derived from the thermochemical decomposition of biomass. The properties of biochar vary with types of feedstock, heating rate, pyrolysis temperature, etc. Consequently, the mechanical and hydrological properties of biochar amended soil (BAS) also differ with types of biochar and soils. However, the effect of bamboo biochar (BB) amendment on soil strength and water retention properties is missing in the previous literature. Bamboo biomass was pyrolysed at 600 °C to produce biochar. BB and soils (low plastic clay (CL) and silty sand (SM)) were mixed to prepare BAS. The samples were prepared by mixing BB in five ratios, i.e., 0%, 1%, 2%, 3.5% and 5% of dry soil weight. The biochar application has increased optimum moisture content, alkalinity (pH) and Atterberg limits, whereas, reduced maximum dry density and specific gravity of both the soils (CL and SM). The unconfined compressive strength (UCS) of CL soil was noted to increase by 10.5% with 2% biochar content and decreased after that, whereas the UCS of SM soil was found to decrease continuously with the biochar content increment. Therefore, the unconfined compressive strength (UCS) result showed that biochar application has contrary effects on both soils. The measured gravimetric water content (GWC) of BAS was increased with biochar increment in both soils. However, GWC increased more in CL than in SM soil at the same biochar content. The microstructural analysis showed that the biochar amendment filled the pore space of the soil matrix, resulting in an increase in UCS and GWC values. The increased water retention capacity and strength (UCS) of biochar amended CL soil provides evidence that it could be used as a landfill cover material.

Benefit analysis of multi-approach biomass energy utilization toward carbon neutrality

To reduce greenhouse gas (GHG) emissions, biomass has been increasingly developed as a renewable and clean alternative to fossil fuels because of its carbon-neutral characteristics. China has been investigating the rational development and use of bioenergy for developing its clean energy and achieving carbon neutrality. Substituting fossil fuels with multi-source and multi-approach utilized bioenergy and corresponding carbon reduction in China remain largely unexplored. Here, a comprehensive bioenergy accounting model with a multi-dimensional analysis was developed by combining spatial, life cycle, and multi-path analyses. Accordingly, the bioenergy production potential and GHG emission reduction for each distinct type of biomass feedstock through different conversion pathways were estimated. The sum of all available organic waste (21.55 EJ yr-1) and energy plants on marginal land (11.77 EJ yr-1) in China produced 23.30 EJ of bioenergy and reduced 2,535.32 Mt CO2-eq emissions, accounting for 19.48% and 25.61% of China's total energy production and carbon emissions in 2020, respectively. When focusing on the carbon emission mitigation potential of substituting bioenergy for conventional counterparts, bioelectricity was the most effective, and its potential was 4.45 and 8.58 times higher than that of gaseous and liquid fuel alternatives, respectively. In this study, life cycle emission reductions were maximized by a mix of bioenergy end uses based on biomass properties, with an optimal 78.56% bioenergy allocation from biodiesel, densified solid biofuel, biohydrogen, and biochar. The main regional bioenergy GHG mitigation focused on the Jiangsu, Sichuan, Guangxi, Henan, and Guangdong provinces, contributing to 31.32% of the total GHG mitigation potential. This study provides valuable guidance on exploiting untapped biomass resources in China to secure carbon neutrality by 2060.

Mechanistic understanding of perfluorooctane sulfonate (PFOS) sorption by biochars

Biochar has recently emerged as a cost-effective solution to combat per- and polyfluoroalkyl substances (PFAS) pollution in water, but mechanistic understanding of which physicochemical properties of biochars dictate PFAS sorptive removal from water remains elusive. Herein, 15 biochars were pyrolyzed from five feedstocks (corn, Douglas fir, eucalyptus, poplar, and switchgrass) at three pyrolysis temperatures (500, 700, and 900 °C) to investigate their removal efficiencies and mechanisms of perfluorooctane sulfonate (PFOS) from water. A commercial biochar was also included for comparison. Biochar physiochemical properties, including elemental composition, pH, specific surface area (SSA), pore structure, hydrophobicity, surface charge, surface functional groups, and crystalline structure were systematically characterized. Batch sorption data showed that the Douglas fir 900 biochar (Douglas fir and 900 are the feedstock type and pyrolysis temperature, respectively; this naming rule applies to other biochars), poplar 900 biochar, and commercial biochar can remove over 95% of PFOS from water. Structural equation model (SEM) was used to elucidate which biochar properties affect PFOS sorption. Interestingly, biochar pore diameter was identified as the most critical factor controlling PFOS removal, but pore diameter/pore volume ratio, SSA, pyrolysis temperature, hydrophobicity, and elemental composition all played variable roles. Hypothetically, biochars with small pore diameters and large pore volumes had a narrow yet deep pore structure that traps PFOS molecules inside once already sorbed, resulting in an enhanced PFOS sorption. Biochars with small pore diameter, low nitrogen content, and high pyrolysis temperature were also favorable for enhanced PFOS sorption. Our findings advance the knowledge of using biochars with optimized properties to remove PFOS and possibly other similar PFAS compounds from water.

Biochar seeding properties affect struvite crystallization for soil application

Struvite crystallization is a viable approach for recovering phosphorus from phosphorus-rich solutions such as urine and wastewater. However, designing seed materials to promote crystal growth and enhance the efficiency of struvite crystallization remains an area of active research. In this study, we investigated the seeding characteristics of biochars on struvite crystallization and the impact of biochar feedstock type and production temperature on the process. Microwave-pyrolyzed biochars produced from different feedstocks and under different temperatures were examined as seeding materials for struvite crystallization from urine and the influence of biochar properties on the overall struvite yield, nutrient recovery and struvite crystal size. Sawdust biochar (lignocellulosic biomass) produced at 500 ​°C had the highest struvite yield (7.91 ​g ​L−1), phosphate (97.9%) and ammonium recovery (87.1%), and relative crystal size (85.2%) compared to the non-seeded treatment due to its higher surface area, pore volume, and hydrophobicity of the biochar. Manure pellet biochar (non-lignocellulosic biomass) produced at 500 ​°C also exhibited performance comparable to sawdust biochar produced at 500 ​°C. Increasing pyrolysis temperature increased biochar's hydrophobicity, zeta potential, electrophoretic mobility and bulk density, irrespective of the feedstock type, thereby improving the seeding process. The ash content of biochar was negatively correlated with its surface area, pore volume, and particle size, but positively correlated with biochar's bulk density and suspension stability. In conclusion, feedstock type and pyrolysis temperature significantly affected biochar properties, which interactively influenced struvite crystallization. Therefore, biochars should be carefully selected to improve their efficiency for phosphorus recovery from phosphorus-containing solutions such as urine and wastewater, with the recovered phosphorus being used for soil applications.

Comparative analysis of the properties of biochars produced from different pecan feedstocks and pyrolysis temperatures

Pecan is an important woody oil and nut tree and it generates a large amount of residues during cultivation and management. However, the utilization of pecan residues remains largely unexplored. In this study, three types of pecan feedstocks (branches, leaves and nut shells) were selected as feedstocks to produce biochars at four pyrolysis temperatures (300, 400, 500 and 600 ℃), and their properties were evaluated for agricultural and environmental applications. The biochar yield decreased with increasing temperature, and the highest yield was generally obtained from leaf biochars. As the pyrolysis temperature increased from 400 to 600 ℃, specific surface area and total pore volume increased sharply while with an obvious decrease in the average pore diameter as a whole. The pH of different biochars presented an upward trend with increasing temperature, while the electrical conductivity and cation exchange capacity (CEC) showed a complex trend, among which the CEC of the biochars produced at 500 ℃ was the highest. The application of pecan biochars improved the water holding capacity of saline-alkali soil overall (except for the biochars produced from nut shells at 500 and 600 ℃). The element analysis suggested that the organic carbon contents in the branch and nut shell biochars were significantly higher than those of leaf biochars; the branch and leaf biochars contained significantly higher total phosphate, available phosphate (AP) and zinc contents; the total potassium and available potassium (AK) levels were highest in the branch biochars, and the highest levels of total nitrogen and other metallic elements were obtained in the leaf biochars. Notably, the levels of some elements (AP, AK, calcium, magnesium, iron, manganese and copper) generally increased with increasing temperature. Pearson’s correlation analysis showed the associations among the biochar properties, and principal component analysis demonstrated that the properties of pecan biochars were generally determined by the interactions of feedstock type and pyrolysis temperature. In conclusion, biochar with known properties produced from different feedstocks and pyrolysis temperatures could be chosen as a suitable soil conditioner or adsorbent applied to agricultural and environmental fields.

Evaluating fundamental biochar properties in relation to water holding capacity

Biochar products that hold and release water within a stable carbonised porous structure provide many opportunities for climate mitigation and a range of applications such as for soil amendments. Biochar that are produced from various organic feedstocks by pyrolysis can provide multiple co-benefits to soil including improving soil health and productivity, pH buffering, contaminant control, nutrient storage, and release, however, there are also risks for biochar application in soils. This study evaluated fundamental biochar properties that influence Water Holding Capacity (WHC) of biochar products and provides recommendations for testing and optimising biochar products prior to soil applications. A total of 21 biochar samples (locally sourced, commercially available, and standard biochars) were characterised for particle properties, salinity, pH and ash content, porosity, and surface area (with N2 as adsorbate), surface SEM imaging, and several water testing methods. Biochar products with mixed particle size, irregular shapes, and hydrophilic properties were able to rapidly store relatively large volumes of water (up to 400% wt.). In contrast, relatively less water (as low as 78% wt.) was taken up by small-sized biochar products with smooth surfaces, along with hydrophobic biochars that were identified by the water drop penetration test (rather than contact angle test). Water was stored mostly in interpore spaces (between biochar particles) although intra-pore spaces (meso-pore and micropore scale) were also significant for some biochars. The type of organic feedstock did not appear to directly affect water holding, although further work is needed to evaluate mesopore scale processes and pyrolytic conditions that could influence the biochemical and hydrological behaviour of biochar. Biochars with high salinity, and carbon structures that are not alkaline pose potential risks when used as soil amendments.

Challenges and advancements in bioprocess intensification of fungal secondary metabolite: kojic acid

Kojic acid is a fungal secondary metabolite commonly known as a tyrosinase inhibitor, that acts as a skin-whitening agent. Its applications are widely distributed in the area of cosmetics, medicine, food, and chemical synthesis. Renewable resources are the alternative feedstocks that can fulfill the demand for free sugars which are fermented for the production of kojic acid. This review highlights the current progress and importance of bioprocessing of kojic acid from various types of competitive and non-competitive renewable feedstocks. The bioprocessing advancements, secondary metabolic pathway networks, gene clusters and regulations, strain improvement, and process design have also been discussed. The importance of nitrogen sources, amino acids, ions, agitation, and pH has been summarized. Two fungal species Aspergillus flavus and Aspergillus oryzae are found to be extensively studied for kojic acid production due to their versatile substrate utilization and high titer ability. The potential of A. flavus to be a competitive industrial strain for large-scale production of kojic acid has been studied.

Hydrochar Application Improves Growth and Intrinsic Water Use Efficiency of Populus alba, Especially during Hot Season

Hydrochar, carbon-rich material produced during the thermochemical processing of biomass, is receiving increased attention due to its potential value as soil amendment. It can increase agroforestry systems’ productivity through direct and indirect effects on growth and soil quality. Hydrochar may also directly help mitigate climate change by sequestering stable carbon compounds in the soil and perhaps indirectly through increased C uptake by trees. In this research, we aim to evaluate how the application of hydrochar produced by two feedstock types, Cynara cardunculus L. (Hc) residuals and sewage sludge (Hs), and in two different doses (3 and 6 kg m−2) could improve the growth and water use efficiency of Populus alba L., a fast-growing tree species largely used in agroforestry as bioenergy crops and in C sequestration. We considered five plants per treatment, and we measured apical growth, secondary growth, leaf area and intrinsic water use efficiency in each plant for the whole growing season from February to October 2022. Our results highlighted that hydrochar applications stimulate the growth and water use efficiency of plants and that the double dose (6 kg m−2) of both hydrochars, and particularly Hc, had positive effects on plant performance, especially during extremely hot periods. Indeed, the year 2022 was characterized by a heat wave during the summer period, and this condition allowed us to evaluate how plants, growing in soils amended with hydrochar, could perform under climate extremes. Our findings showed that the control plants experienced severe damage in terms of dried stems and dried leaves during summer 2022, while hydrochar applications reduced these effects.

Non-Catalytic Partial Oxidation of Hydrocarbon Gases to Syngas and Hydrogen: A Systematic Review

The review contains a comparative analysis of studies on the production of hydrogen and syngas based on the processes of partial oxidation of natural gas and other types of gas feedstock. The results presented in the literature show the high potential of non-catalytic autothermal processes of partial oxidation of hydrocarbons for the development of gas chemistry and energetics. The partial oxidation of hydrocarbons makes it possible to overcome such serious shortcomings of traditional syngas production technologies as technological complexity and high energy and capital intensity. The features of non-catalytic partial oxidation of hydrocarbon gases, the obtained experimental results and the results of kinetic modeling of various options for the implementation of the process, which confirm the adequacy of the kinetic mechanisms used for the analysis, are considered in detail. Examples of industrial implementation of processes based on partial oxidation and proposed alternative options for its organization are considered. Designs of reactors used to ensure stable conversion of rich mixtures of hydrocarbons with an oxidizer are presented. The possibility of obtaining other chemical products by partial oxidation of hydrocarbons is discussed.

Comprehensive Review on Lipid-based Biomasses as Biodiesel Raw Materials from Ghana

Ghana is a country rich in natural resources, including biodiversity and large water bodies, but it is also plagued by food and energy shortages. Fuel prices are also increasing. Biodiesel made from lipids will attract increasing attention as researchers and experts look for a solution. However, the obvious cheapest option of edible feedstock will be insufficient to meet rising energy and food demand, necessitating the need for a guaranteed feedstock. As a result, this research was conducted to identify lipid-based biomass feedstocks that would be ideal for biodiesel production in Ghana. This research seeks to give current information on the biofuel feedstock currently existing (mostly biodiesel) synthesis from lipid-based biomasses in Ghana. Edible plant oils were the first generation of lipid-based feedstocks, whereas alternative types of feedstocks were identified and reported as the second generation. Non-edible oils, like Jatropha oil, Neem oil, Karanja oil, Nagchampa oil, Calophyllum inophyllum oil, Mahua indica oil, Rubber seed oil, and other non-edible feedstocks are used to make second-generation biodiesels. Vegetable oil waste, industrial wastes and by-products, animal fats, and lipid-derived from microorganisms and insects are also among the 2nd generation feedstocks discussed in this paper. The advantages of 2nd generation feedstocks are the low-cost, high-yielding, and the fact that they do not economically or ethically compete with edible oils (food crops). Nevertheless, all 2nd generation feedstocks are often free fatty acids and having high moisture, which have a significant detrimental impact on the conventional biodiesel synthesis process. As a result, this article contains basic information on processing procedures that can handle 2nd generation feedstocks.

Biochar as a Green Sorbent for Remediation of Polluted Soils and Associated Toxicity Risks: A Critical Review

Soil contamination with organic contaminants and various heavy metals has become a global environmental concern. Biochar application for the remediation of polluted soils may render a novel solution to soil contamination issues. However, the complexity of the decontaminating mechanisms and the real environment significantly influences the preparation and large-scale application of biochar for soil ramification. This review paper highlights the utilization of biochar in immobilizing and eliminating the heavy metals and organic pollutants from contaminated soils and factors affecting the remediation efficacy of biochar. Furthermore, the risks related to biochar application in unpolluted agricultural soils are also debated. Biochar production conditions (pyrolysis temperature, feedstock type, and residence time) and the application rate greatly influence the biochar performance in remediating the contaminated soils. Biochars prepared at high temperatures (800 °C) contained more porosity and specific surface area, thus offering more adsorption potential. The redox and electrostatic adsorption contributed more to the adsorption of oxyanions, whereas ion exchange, complexation, and precipitation were mainly involved in the adsorption of cations. Volatile organic compounds (VOCs), dioxins, and polycyclic aromatic hydrocarbons (PAHs) produced during biochar pyrolysis induce negative impacts on soil alga, microbes, and plants. A careful selection of unpolluted feedstock and its compatibility with carbonization technology having suitable operating conditions is essential to avoid these impurities. It would help to prepare a specific biochar with desired features to target a particular pollutant at a specific site. This review provided explicit knowledge for developing a cost-effective, environment-friendly specific biochar, which could be used to decontaminate targeted polluted soils at a large scale. Furthermore, future study directions are also described to ensure a sustainable and safe application of biochar as a soil improver for the reclamation of polluted soils.

Advancement of biodiesel fuel quality and NOx emission control techniques

Sustainable waste derived biodiesel can substitute significant amount of fossil-based fuels currently used for marine propulsion, agricultural processes, small scale power generation, and in heavy goods vehicles. However, biodiesel fuel quality varies depending on the feedstock type, production method and storage conditions. Meeting biodiesel standards and reduction of NOx emissions are two main challenges when biodiesels are being used in the internal combustion engines. This study aims to address these two challenges by using biodiesel-biodiesel blending and various NOx reduction techniques. Biodiesels produced from waste resources and inedible plant seed oils are investigated. Fuel properties, biodiesels standards, and engine test results are reviewed. It was found that blends of animal fat biodiesels and vegetable oil biodiesels are likely to improve fuel properties and combustion characteristics. The biodiesel-biodiesel blends also help to reduce exhaust pollutants. The saturation level of the biodiesel fuel is increased through this technique. Animal fat biodiesels are composed of saturated fatty acid methyl esters, and vegetable oil biodiesels are composed of unsaturated fatty acids. The NOx gas emission reduction techniques are investigated and categorised under three sub-groups, fuel treatment, engine adjustment and exhaust after-treatment. Based on the state of art review, scopes for future R&D topics are presented for researchers and relevant industries.

Assessing the biotechnological potential of cotton type-1 and type-2 diacylglycerol acyltransferases in transgenic systems

The chemical and physical properties of vegetable oils are largely dictated by the ratios of 4–6 common fatty acids contained within each oil. However, examples of plant species that accumulate from trace amounts to >90% of certain unusual fatty acids in seed triacylglycerols have been reported. Many of the general enzymatic reactions that drive both common and unusual fatty acid biosynthesis and accumulation in stored lipids are known, but which isozymes have evolved to specifically fill this role and how they coordinate in vivo is still poorly understood. Cotton (Gossypium sp.) is the very rare example of a commodity oilseed that produces biologically relevant amounts of unusual fatty acids in its seeds and other organs. In this case, unusual cyclopropyl fatty acids (named after the cyclopropane and cyclopropene moieties within the fatty acids) are found in membrane and storage glycerolipids (e.g. seed oils). Such fatty acids are useful in the synthesis of lubricants, coatings, and other types of valuable industrial feedstocks. To characterize the role of cotton acyltransferases in cyclopropyl fatty acid accumulation for bioengineering applications, we cloned and characterized type-1 and type-2 diacylglycerol acyltransferases from cotton and compared their biochemical properties to that of litchi (Litchi chinensis), another cyclopropyl fatty acid-producing plant. The results presented from transgenic microbes and plants indicate both cotton DGAT1 and DGAT2 isozymes efficiently utilize cyclopropyl fatty acid-containing substrates, which helps to alleviate biosynthetic bottlenecks and enhances total cyclopropyl fatty acid accumulation in the seed oil.

Unravelling the Recent Developments in the Production Technology and Efficient Applications of Biochar for Agro-Ecosystems

Considerable interest is being shown in using biochar production from waste biomass with a variety of disciplines to address the most pressing environmental challenges. Biochar produced by the thermal decomposition of biomass under oxygen-limited conditions is gaining popularity as a low-cost amendment for agro-ecosystems. The efficiency of biochar formation is affected by temperature, heating rate, feedstock type, particle size and reactor conditions. Properties such as pH, surface area and ash content of produced biochar increases with increasing temperatures. Biochar produced at lower heating rates may have high porosity and be beneficial for morphological changes in the soil. Biochar can help to enhance soil health and fertility as well as improve agricultural yield. As a result, biochar can assist in increasing food security by promoting sustainable agricultural systems and preserving an eco-friendly environment. Biochar is also widely being used as a sorbent for organic and inorganic pollutants, owing to its large surface area, allowing it to be immobilized from soil with ease. The functional groups and charges present on the surface of biochar play an important role in pollutants removal. This review focuses on the mechanisms of biochar production using different waste materials as a feed stock, factors that influence biochar quality as well as application of biochar in agricultural soil and their reclamation as well. This article also discusses knowledge gaps and future perspectives in the field of biochar-based toxic-pollution remediation.

Life cycle analysis of biodiesel derived from fresh water microalgae and Karanja

Biodiesel is regarded as a feasible substitute for fossil fuel; thus, to fulfil the tremendous need for energy, potential non-edible feedstocks must be identified and assessed in terms of their environmental consequences and energy requirements for biodiesel production. Cradle to Grave life cycle approach (LCA) is currently being used to compare the environmental impacts and energy requirements of biodiesel obtained from two types of biodiesel feedstock i.e., Karanja (Pongamia Pinnata) and Microalgae. Sensitivity analysis was also performed to explore the influence of elements such as agricultural systems and energy sources on LCA systems in the given conditions. Karanja feedstock and microalgae have energy ratios of 3.57 and 0.45, respectively. GHG emissions from well to wheel for oil methyl esters derived from Karanja feedstock are estimated to be 63.81 gCO2eq/MJ, while microalgae feedstock emissions are 85.37 gCO2eq/MJ. According to the sensitivity study, both emission and energy estimates were significantly sensitive to biodiesel output. Karanja excelled in all GHG-emitting processes, with reduced GHG emissions and a greater energy ratio. Microalgae, on the other hand, would be the preferable feedstock in the long run since it has demonstrated competitive performance in terms of carbon dioxide emissions, and energy ratio, and has no detrimental influence on the food cycle.

Incorporating Chemometric Methods in the Undergraduate Curriculum: A Problem Set Activity for an Upper-Level Analytical Elective Course

In this paper, a problem set activity focused on understanding and applying unsupervised and supervised chemometric methods for the analysis of biodiesel–diesel blended fuels is described. This problem set was utilized in two upper-level analytical elective courses aimed for junior and senior level students. The data set consists of peak areas taken from gas chromatograms comprising various biodiesel concentrations and feedstock types. Students are tasked with analyzing the data set using principal component analysis (PCA), hierarchical cluster analysis (HCA), and k-nearest neighbors (kNN). The primary purpose of this problem set is to gain hands-on experience manipulating and drawing conclusions about large data sets using chemometric methods. The problem set activity utilizes a large GCMS data set with many varieties of sample types and can be included at any institution with no need for a GCMS instrument on campus.

Biochar-Soil-Plant interactions: A cross talk for sustainable agriculture under changing climate

Biochars provide several agricultural and environmental benefits, such as soil health improvement, better crop growth and yield, carbon sequestration, decreasing greenhouse gas (GHGs) emissions, and regulation of nutrient dynamics. This review highlights the role of biochar in transforming the soil’s physiochemical and biological properties, and their impact on improving seed germination and seedling growth, altering crop physiological attributes, enhancing crop resistance against biotic and abiotic stresses, improving crop productivity, curtailing GHGs, and controlling nutrient leaching losses. However, the type of feedstock used, pyrolysis temperature, application rate and method, soil type and crop species largely influence the biochar performance under different environmental conditions. Application of biochars at low rates help to promote seed germination and seedling growth. Biochar modified the abiotic and microbial processes in the rhizosphere and increased nutrient mineralization and enhanced the nutrient availability for plant uptake. Hence, biochar enhanced the plant resistance against diseases, reduced the availability of heavy metals and improved the plant resilience against environmental stressors. By providing a comprehensive analysis about the variable impacts of biochars on soil physicochemical properties, plant growth, development and productivity and mitigating environmental problems, this review is quite valuable for developing an efficient soil and crop specific biochar with desired functionalities. It could be helpful in improving crop productivity, ensuring food security and better management of environment. Furthermore, this review identifies the knowledge gaps and suggests future outlooks for the commercialization of biochar applications on large-scale.

Biochar yield prediction using response surface methodology: effect of fixed carbon and pyrolysis operating conditions

AbstractGenerating value from wastes via pyrolysis has been increasingly researched in recent times. Biochar is a versatile pyrolysis product with yields based on many process parameters, including feedstock type and particle size, and operating conditions such as pyrolysis reactor, heating rate, residence time, and reaction temperature. The heterogeneous nature of waste biomass creates challenges in controlling the pyrolysis’ product selectivity. Intensive and time-consuming experimental studies are often required to determine product distribution for the pyrolysis of each unique feedstock. Alternatively, prediction models that learn from a wide range of existing experimental data may provide insight into potential yields for different biomass sources. Several advanced models exist in the literature which can predict the yield of biochar and subsequent products based on operating temperature. However, these models do not consider the combined effect of biomass characteristics and operating conditions on biochar yield, which is considered a decisive factor for biochar formation. As such, the objective of this study is to develop a prediction model based on the biomass’ fixed carbon content (14–22%), reaction temperature (350–750 °C), and heating rate (5–10 °C/min) using the response surface methodology. Biomasses, date stones, spent coffee grounds, and cow manure have been used to design a Box-Behnken experiment based on the three factors for the biochar yield response. An empirical equation is developed based on a statistically significant quadratic model to produce optimized biochar yield with high prediction accuracy. The study discussed the 3D response and diagnostic plots and conducted validation experiments to confirm the applicability of the developed model. The biochar yields are significantly affected by the fixed carbon content of the feedstock and the reaction temperature, and the experimental validation confirms the accuracy of biochar yield quantification. The model can be easily applied for further process flow modeling of biomass pyrolysis, only relying on proximate feed analysis, operating temperature, and heating rate.

Aqueous phase reforming of starch wastewater over Pt and Pt-based bimetallic catalysts for green hydrogen production

This work analyses the application of aqueous phase reforming (APR) for green hydrogen production from starch industry wastewater. This work reports for the first time on the direct conversion of a high molecular weight biomass polymer contained in wastewater in contrast to low molecular weight substrates mainly reported in the literature. The potential of this type of feedstock was evaluated by varying the starch source (rice, potato, sweet potato and cassava) and the type of catalyst (carbon supported Pt, PtRu, PtPd, PtRe and PtRh catalysts). In APR experiments at 220 °C with synthetic wastewater, PtRu/C and Pt/C catalysts achieved the highest H2 yield values, around 51 mmol H2 per g of organic carbon in the initial wastewater, close to 2.6 times higher than that reported in the literature of brewery wastewater, a promising substrate. The lack of free aldehyde or keto groups due to glycosidic bonds between glucose units in starch results in higher conversion to gas and H2 production compared to APR of glucose. This fact shows that APR has more feedstock flexibility than that previously reported for light compounds. In the experiments with real wastewaters, the organic matter removal was influenced largely by the starch source: the best APR performance (28.5 mmol H2 gTOCi−1) was obtained for rice processing wastewater, which is characterized by the highest starch concentration and the lowest protein content. Poor performance was observed in the APR of potato processing wastewater, probably due to catalyst deactivation caused by protein fraction.