Biochar Carbon Research Articles

Spindle-shaped CeO2/biochar carbon with oxygen-vacancy as an effective and highly durable electrocatalyst for oxygen reduction reaction

Highly durable and active CeO2 on biochar carbon (CeO2/BC) derived from Spirulina platensis microalgae and synthesized by simple one-pot hydrothermal treatment and further activated through pyrolysis approach. A spindle-shaped morphology of CeO2 with predominant (111) facet was evidently observed from X-ray diffraction patterns and electron microscopy images. The structural features such as high specific surface area, defect-rich carbon with N & P atoms, increased oxygen vacancy and π-electron transfer play an important role for the improved oxygen reduction reaction (ORR). The considerable amount of Ce3+ and higher proportion of pyridinic N and graphitic N species are substantially contributed to the superior ORR performance of CeO2/BC700, which surpasses other similar catalysts and competing with Pt/C. Hence, the significant kinetic ORR parameters and extended stability (no loss after 5000 potential cycles) of the CeO2/BC700 catalysts provides the promising insight to develop the rare-earth metal oxide nanostructures as a possible candidate for ORR in alkaline medium.

Small-scale biochar production on Swedish farms: A model for estimating potential, variability, and environmental performance

Several small-scale pyrolysis plants have been installed on Swedish farms and uptake is increasing in the Nordic countries. Pyrolysis plants convert biomass to biochar for agricultural applications and syngas for heating applications. These projects are driven by ambitions of achieving carbon dioxide removal, reducing environmental impacts, and improving farm finances and resilience. Before policy support for on-farm pyrolysis projects is implemented, a comprehensive environmental evaluation of these systems is needed. Here, a model was developed to jointly: (i) simulate operation of on-farm energy systems equipped with pyrolysis units; (ii) estimate biochar production potential and its variability under different energy demand situations and designs; and (iii) calculate life cycle environmental impacts. The model was applied to a case study farm in Sweden. The farm’s heating system achieved net carbon dioxide removal through biochar carbon sequestration, but increased its impact in several other environmental categories, mainly due to increased biomass throughput. Proper dimensioning of heat-constrained systems is key to ensure optimal biochar production, as biochar production potential of the case farm was reduced under expected climate change in Sweden. To improve the environmental footprint of future biochar systems, it is crucial that expected co-benefits from biochar use in agriculture are realised. The model developed here is available for application to other cases.

Effect and mechanism of biochar on CO2 and N2O emissions under different nitrogen fertilization gradient from an acidic soil

“Nature based solutions” has been proposed at COP25 as an important venture for combating anthropogenic climate change, and soil biochar amendment have been proposed to have vast carbon sequestration potential. On the other hand, biochar carbon storage in soils is confronted with both biochar and soil carbon and nitrogen loss. The superposition of these two influences leads to complex variation in net greenhouse gas emissions from biochar-amended-soils. Nitrogen fertilization is a common agriculture practice in China and worldwide. To study the effects and mechanisms of biochar on soil net greenhouse gas emissions (CO2, N2O) under different nitrogen fertilization gradient in a ferrallitic soil, a soil column experiment was conducted. Maize straw derived biochar (pyrolysed at 500 °C) and nitrogen fertilizer (ammonium sulfate) were investigated at varying application rates. It was found that biochar amendment increased CO2 emissions by 51.1%–57.1% and N2O emissions by 50.0%–73.7%, respectively, when soil was incubated with 50 mg N/kg nitrogen fertilization. The N2O emission in soil was dominated by nitrification, and the labile fraction of biochar played the dominant role in increasing soil CO2 and N2O emissions. Therefore, water or acid washing of biochar before its application would significantly reduce the net GHG emissions. When the nitrogen fertilization was applied at the unusually high level of 450 mg N/kg, the N2O emissions mainly came from denitrification. Biochar amendment introduced less soil CO2 emission increment, and suppressed N2O emissions by inhibition of denitrification via adsorption protection mechanism (towards nitrogen) and aeration effect. A chain mechanism has been illustrated and results from this study suggest that biochar is best applied to an environment or the circumstance that maximizes adsorption protection mechanism and aeration effect to achieve total greenhouse gas emission reduction. This study therefore provides basis for the scientific sound application and regulation of biochar amendment in soils.

Application Research of Biochar for the Remediation of Soil Heavy Metals Contamination: A Review.

Soil contamination by heavy metals threatens the quality of agricultural products and human health, so it is necessary to choose certain economic and effective remediation techniques to control the continuous deterioration of land quality. This paper is intended to present an overview on the application of biochar as an addition to the remediation of heavy-metal-contaminated soil, in terms of its preparation technologies and performance characteristics, remediation mechanisms and effects, and impacts on heavy metal bioavailability. Biochar is a carbon-neutral or carbon-negative product produced by the thermochemical transformation of plant- and animal-based biomass. Biochar shows numerous advantages in increasing soil pH value and organic carbon content, improving soil water-holding capacity, reducing the available fraction of heavy metals, increasing agricultural crop yield and inhibiting the uptake and accumulation of heavy metals. Different conditions, such as biomass type, pyrolysis temperature, heating rate and residence time are the pivotal factors governing the performance characteristics of biochar. Affected by the pH value and dissolved organic carbon and ash content of biochar, the interaction mechanisms between biochar and heavy metals mainly includes complexation, reduction, cation exchange, electrostatic attraction and precipitation. Finally, the potential risks of in-situ remediation strategy of biochar are expounded upon, which provides the directions for future research to ensure the safe production and sustainable utilization of biochar.

In situ growth of carbon nitride on titanium dioxide/hemp stem biochar toward 2D heterostructured photocatalysts for highly photocatalytic activity.

In this work, hierarchical structure TiO2/hemp stem biochar carbon (HSBC) and C3N4-TiO2/HSBC were successfully fabricated, which were used as efficient visible-light photocatalyst degradation for ammonia nitrogen from aqueous solution. The as-prepared C3N4-TiO2/HSBC hybrid catalyst showed the higher efficient photocatalytic activity for decomposition of ammonia nitrogen than those of pure TiO2 and TiO2/HSBC, suggesting suppressed recombination of photogenerated charges and promoted mass transfer due to synergistic effect, and thus increased photocatalytic degradation activity. The degradation of ammonia follows a pseudo-first-order kinetics. All prepared catalysts demonstrated extremely photocatalytic efficiency under visible-light and UV light illumination; the ammonia nitrogen photocatalytic degradation activity of C3N4-TiO2/HSBC can reach 90.3% under UV light while the degradation activity achieved about 50.7% under visible-light irradiation. The results revealed that the h+ was dominantly active intermediates in the process of photocatalytic degradation. The prepared catalysts are promising for the degradation of ammonia nitrogen from water resource.

Chemical and physical characterization of rice husk biochar and ashes and their iron adsorption capacity

After flooding in rice crops, the Fe3+ ions from iron oxide minerals are reduced to Fe2+ in the anaerobic conditions, making it soluble. The excess of Fe2+ in soil solution can be toxic to plants, resulting in decreasing rice yield. Pyrolyzed materials from rice crop residues, such as rice husk, can be an environmentally friendly option to reduce iron availability in soil solution, provided they have appropriate chemical and physical characteristics regarding iron adsorption. In this study, rice husk biochar (RHB) and rice husk ashes (RHA1 and RHA2) were characterized regarding physical and chemical characteristics and the iron adsorption capacity. The different oxygenation conditions in obtaining the materials resulted in chemical and physical differences (e.g., biochar carbon content of 46% and ashes of 16% and 0.93%), but there were no significant differences related to iron adsorption capacity in aqueous solution. The iron adsorption capacity of the biochar was 5.53 mg Fe2+ g−1 and of the ashes was 6.74 and 7.22 mg Fe2+ g−1 for the two materials tested, which demonstrates potential of these materials to mitigate iron toxicity in flooded rice crops.

Biochar from cookstoves reduces greenhouse gas emissions from smallholder farms in Africa

Biochar produced in cookstoves has the potential to contribute to negative carbon emissions through sequestration of biomass carbon while also providing other benefits for sustainable development, including provision of clean renewable energy and increased yields in tropical agriculture. The aim of the reported research was to estimate effects on food production, household energy access and life cycle climate impact from introduction of biochar-producing cookstoves on smallholder farms in Kenya. Participatory research on biochar production and use was undertaken with 150 Kenyan smallholder farming households. Gasifier cookstove functionality, fuel efficiency and emissions were measured, as well as biochar effects on agricultural yields after application to soil. Cookstoves provided benefits through reduced smoke, fuel wood savings and char production, but challenges were found related to labour for fuel preparation, lighting and refilling. On-farm trials with varying rates of biochar inputs, in combination with and without mineral fertilizers, have led to a sustained increase of maize yields following one-time application. The climate impact in a life cycle perspective was considerably lower for the system with cookstove production of biochar and use of biochar in agriculture than for current cooking practices. Climate benefits from biochar production and use are thus possible on smallholder farms in sub-Saharan Africa, through reduced use of biomass in cooking, reduced emissions of products of incomplete combustion and sequestration of stable biochar carbon in soils. Biochar-producing cookstoves can be implemented as a climate change mitigation method in rural sub-Saharan Africa. Successful implementation will require changes in cooking systems including fuel supply, as well as farming systems, which, in turn, requires an understanding of local socio-cultural conditions, including power relations and gender aspects.

Biochar as supporting material for heterogeneous Mn(II) catalysts: Efficient olefins epoxidation with H2O2

A novel type of hybrid catalytic materials [MnII-L@BC] has been developed using biochar (BC) as support material for covalent grafting of a MnII Schiff-base catalyst (MnII-L). The hybrid [MnII-L@BC] materials have been evaluated for an important catalytic process, epoxidation of olefins using H2O2 as oxidant. A number of different substrates were used, with cyclohexene achieving the highest yields. When compared to the non-grafted, homogeneous MnII-L, the hybrid catalysts [MnII-L@BC] show a significant enhancement of the catalytic efficiency i.e. as documented by the increase of Turnover Numbers (TONs) (826 for [MnII-L-SS550ox] and 822 for [MnII-L-SW550ox]) and Turnover Frequencies (TOFs) (551 h−1 for [MnII-L-SS550ox] and 411 h−1 for [MnII-L-SW550ox]). The interfacial catalytic mechanism and the role of the BC support have been analyzed by Raman and Electron Paramagnetic Resonance spectroscopies. Based on these data we discuss a mechanism where the high efficiency of the hybrid materials involves the biochar carbon layers acting as promoters of the substrate and products kinetics. To a broader context, this work exemplifies that biochar-based hybrid materials are potent for oxidative catalysis technologies.

The financial trade‐off between the production of biochar and biofuel via pyrolysis under uncertainty

AbstractThere is a lack of widespread interest in slow pyrolysis biochar pathways relative to other bioenergy pathways because of the perceived absence of biochar's market value when produced at a commercial scale. Thus, most refereed techno‐economic analyses focus on fast pyrolysis. This study quantifies the carbon price point at which the economic feasibility of the slow‐pyrolysis pathway for biochar production is equal to or greater than a fast‐pyrolysis pathway for biochar and biofuel production using baseline minimum carbon prices (MCP). These factors are then modeled under uncertainty to generate stochastic cash flows for the calculation of a 20‐year net present value and carbon abatement cost probability distributions. This article examines whether a slow‐pyrolysis pathway is ever more financially attractive than a fast‐pyrolysis pathway at realistic carbon prices. The results show fast pyrolysis to fuels and biochar achieving the lowest baseline MCP of $61.38/Mg, while the slow pyrolysis to biochar and methanol at 450 °C scenario yields the highest baseline MCP of $642.40/Mg. A notable result is the baseline MCP for the slow pyrolysis to biochar scenario achieving $123.48/Mg, when compared with the fast pyrolysis to fuels and electricity scenario, resulting in a baseline MCP of $182.03/Mg. The results suggest that carbon prices, when high enough, can incentivize biochar carbon sequestration produced from slow‐pyrolysis pathways rather than carbon abatement with biofuels, and that slow pyrolysis to biochar and methanol scenarios require a higher baseline MCP and are less financially competitive than the other pathways. © 2020 Society of Chemical Industry and John Wiley & Sons, Ltd

Effect of calcium dihydrogen phosphate addition on carbon retention and stability of biochars derived from cellulose, hemicellulose, and lignin

Pyrolysis of biomass with phosphate compound is a promising method to improve biochar characteristics. However, how phosphate compound affects the three components of biomass during the biochar formation is still unclear. In this study, a typical phosphate compound, calcium dihydrogen phosphate (Ca(H2PO4)2), was premixed with cellulose, hemicellulose, and lignin reagent, at the ratio of 20% (w/w) for biochar production through pyrolysis, aiming to investigate the effects of Ca(H2PO4)2 addition on biochar formation. Results show that, with Ca(H2PO4)2 additions, carbon retention of biochars from cellulose (MCBC) and hemicellulose (MHBC) increased by 63.4% and 48.3%, respectively, but that of lignin (MLBC) decreased by 6.7% due to the reactions between lignin and Ca(H2PO4)2. Moreover, the stable carbon proportion in the biochar decreased by 10.2% for MCBC, almost unchanged for MHBC, and increased by 6.15% for MLBC based on the potassium dichromate oxidation. During the pyrolysis process, Ca(H2PO4)2 addition fixed more volatile and/or labile carbon in biochar, resulting in greater carbon retention. Declined carbon stability of biochar might be caused by the inhibited formation of aromatic-C, evidenced by the Fourier transform infrared spectroscopy analysis. This study highlights the importance and potential mechanisms of calcium dihydrogen phosphate influencing the carbon retention and stability of biochar derived from three biomass components.

Effects of biochar application on crop water use efficiency depend on experimental conditions: A meta-analysis

It is widely reported that biochar has the benefit of improving water use efficiency (WUE). However, a lot of researches indicated that the percentage changes in WUE to biochar application were variable (from +312.5 % to -35.9 %). A total of 43 studies with 284 data pairs were collected and divided into two categories: plant water use efficiency (PWUE) and leaf water use efficiency (LWUE), and then a meta-analysis was conducted with the aim to 1) estimate the effects of adding biochar to soils on WUE; and 2) identify the experimental conditions that benefit WUE compared to the control. Results showed that there was a statistically significant positive effect of biochar on WUE with a grand mean increase of +18.8 % in PWUE and +20.0 % in LWUE. However, the effectiveness was limited to specific soil properties, biochar parameters, and management factors. In soil analyses, no significant difference was observed between soil texture categories, while with regard to soil pH there were significant differences in WUE responses and evident contrasting effects of biochar application on PWUE and LWUE. Greatest increases in PWUE were found in soils with pH > 8 (33.4 % on average, 95 % CI: 28.7 %–38.3 %), while negative effects on LWUE were obtained (-8.9 % on average, 95 % CI: -22.5 %–7.0 %). This suggests that one of the main mechanisms for WUE responses to biochar application may be ‘the addition of alkaline biochar to alkaline soils’, stressing the matching of biochar pH and soil pH. Through the analyses of biochar carbon (C) content, we concluded that the increase in WUE depressed with increasing C content of biochar and proposed another mechanism ‘excess carbon released from biochar’. It illustrates why wood biochar showed a significantly small increase in WUE compared to biochar made from herbaceous material. The finding that the highest positive effect on PWUE (32.4 % on average, 95 % CI: 23.3 %–42.2 %) was observed at less than 20 t ha−1 biochar application rate agrees with and further validates this mechanism. In addition, biochar K content and N application rate could be used as an effective predictor of WUE responses to biochar application according to significant differences between such categories. Our findings can provide suggestions for rational biochar application to improve WUE in crop production, but it is limited by the lack of the longevity of the effects, which is important for developing sustainable biochar policy.

Soil carbon increased by twice the amount of biochar carbon applied after 6 years: Field evidence of negative priming

AbstractApplying biochar to agricultural soils has been proposed as a means of sequestering carbon (C) while simultaneously enhancing soil health and agricultural sustainability. However, our understanding of the long‐term effects of biochar and annual versus perennial cropping systems and their interactions on soil properties under field conditions is limited. We quantified changes in soil C concentration and stocks, and other soil properties 6 years after biochar applications to corn (Zea mays L.) and dedicated bioenergy crops on a Midwestern US soil. Treatments were as follows: no‐till continuous corn, Liberty switchgrass (Panicum virgatum L.), and low‐diversity prairie grasses, 45% big bluestem (Andropogon gerardii), 45% Indiangrass (Sorghastrum nutans), and 10% sideoats grama (Bouteloua curtipendula), as main plots, and wood biochar (9.3 Mg/ha with 63% total C) and no biochar applications as subplots. Biochar‐amended plots accumulated more C (14.07 Mg soil C/ha vs. 2.25 Mg soil C/ha) than non‐biochar‐amended plots in the 0–30 cm soil depth but other soil properties were not significantly affected by the biochar amendments. The total increase in C stocks in the biochar‐amended plots was nearly twice (14.07 Mg soil C/ha) the amount of C added with biochar 6 years earlier (7.25 Mg biochar C/ha), suggesting a negative priming effect of biochar on formation and/or mineralization of native soil organic C. Dedicated bioenergy crops increased soil C concentration by 79% and improved both aggregation and plant available water in the 0–5 cm soil depth. Biochar did not interact with the cropping systems. Overall, biochar has the potential to increase soil C stocks both directly and through negative priming, but, in this study, it had limited effects on other soil properties after 6 years.

Different alkaline minerals interacted with biomass carbon during pyrolysis: Which one improved biochar carbon sequestration?

During the pyrolytic production of biochar, only 50% of carbon (C) could be retained in biochar, and about 10% C would be mineralized after biochar is amended into soil. In this study, we aim to search a material to pretreat the biomass and improve carbon sequestration along biochar production and application. Alkaline minerals are widely reported to have catalytic effect on biomass pyrolysis and alter the liquid and gas products, while few studies have focused on their influence on biochar C sequestration. This study selected KCl, NaCl, MgCl2, and CaCl2 to dope in a biomass, cow manure, to explore their influence on the carbon sequestration based on carbon retention before and after pyrolysis and the carbon stability assessed by K2Cr2O7 oxidation and biological mineralization in real soil. Results showed that dosage of these minerals with a mineral/biomass ratio of 1: 5 (w/w) increased C retention in biochar from 49.8% (without minerals) to 52.5% (KCl), 53.7% (NaCl), 64.1% (MgCl2), and 60.7% (CaCl2), respectively. However, only MgCl2-fixed C in the produced composite biochar (Mg-BC) exhibited significant C stability both for bulk C (about 60.0%) and surface C (5.0 mg CO2·kg−1 soil). Addition of CaCl2 also could retain more C in biochar during pyrolysis, while the C in this composite biochar was not stable indicated by K2Cr2O7 oxidation and biological mineralization. Crystals of MgO and MgO3(CO3)2 were detected on the surface of Mg-BC by X-ray diffractometer (XRD), which could sorb small organic molecules such as C3–C7 compounds from the thermal decomposition verified by thermogravimetry-mass spectrum analysis (TG-MS). Moreover, a physical barrier was formed covering on biochar surface and enhance its capacity against oxidation and biological mineralization. This study offers a potential strategy to strengthen biochar-carbon sequestration by Mg-doping from the production of biochar to the application in soil environment.

Gamma-radiated biochar carbon for improved supercapacitor performance.

Biochar carbon YP-50 exposed to gamma radiation at 50 kGy, 100 kGy, and 150 kGy was used as an electrode for an electric double-layer capacitor. The gamma radiation affected the pore structure and pore volume of the biochar electrodes. The optimized surface morphology, pore structure, and pore volume of the biochar with an irradiation dose of 100 kGy showed outstanding specific capacitance of 246.2 F g−1 compared to the untreated biochar (115.3 F g−1). The irradiation dose of 100 kGy exhibited higher specific power and specific energy of 0.1 kW kg−1 and 34.2 W h kg−1 respectively, with a capacity retention of above 96% after 10 000 cycles at a current density of 2 A g−1. This improvement can be attributed to the decrease in average particle size, an increase in the porosity of biochar carbon. Besides, the charge transfer resistance of supercapacitor is significantly reduced from 21.7 Ω to 7.4 Ω after treating the biochar carbon with 100 kGy gamma radiation, which implies an increase in conductivity. This gamma radiation strategy to pretreat the carbon material for improving the properties of carbon materials can be promising for the development of high-performance supercapacitors for large-scale applications.

Biochar of distillers' grains anaerobic digestion residue: Influence of pyrolysis conditions on its characteristics and ammonium adsorptive optimization.

To promote the sustainable development of the liquor/ethanol industry and environment protection, alternative ways to dispose of anaerobic digestion residue (ADR) are urgently required. This research aims at studying the effects of different residence times (RTs) (30, 60 and 120 min) and heating rates (HR) (2.5, 5.0 and 10.0°C min-1) under 700°C on characteristics of ADR biochar as well as the optimization of ammonium (NH4+) adsorption. Results showed that, with the increasing RT and HR, the aromaticity as well as the content of fixed carbon and elemental carbon of ADR biochar increased, but the pyrolysis yield, volatile matter content, elemental hydrogen, oxygen and polarity decreased. Biochar prepared at 60 min and 5.0°C min-1 under 700°C presented the best development of orderly and honeycomb shape structures, highest specific surface area and maximal amount of NH4+ adsorption (3.15 mg N g-1). The multilayer heterogeneous adsorption process dominated the NH4+ adsorption behaviour. And the maximal amount of NH4+ adsorption was achieved with 4 g biochar L-1 at pH 11.0 along with the order of the competitive effect of K+ > Na+ > Ca2+ > Mg2+. Furthermore, NH4+ adsorption was exothermic. Thus, the present study demonstrated that ADR biochar has potential to adsorb NH4+ from NH4+ polluted water to meet environmental standards.

Evaluation of the Influence of Individual Clay Minerals on Biochar Carbon Mineralization in Soils

Although association between mineral and biochar carbon have been speculated in some studies, still there is no direct evidence for the influence of individual clay minerals on the mineralization of biochar carbon in soils. To address this, we conducted an incubation study using monomineralic soils constituted by separately mixing pure minerals, i.e., smectite, kaolinite, and goethite, with a sandy soil. Switch grass biochar (400 °C) was added to the artificial soils and samples were incubated for 90 days at 20 °C in the laboratory. The CO2-C mineralized from the control, and biochar amended soil was captured in NaOH traps and the proportion of C mineralized from biochar was determined using δ13C isotopic analysis. The clay minerals significantly decreased the cumulative total carbon mineralized during the incubation period, whereas biochar had no effect on this. The least amount of total C was mineralized in the presence of goethite and biochar amended soil, where only 0.6% of the native soil organic carbon (SOC) (compared to 4.14% in control) and 2.9% of the biochar-C was mineralized during the 90 days incubation period. Native SOC mineralization was significantly reduced in the presence of biochar and the three minerals. Goethite was most effective in stabilizing both biochar and the native soil organic carbon. The short-term data from this study demonstrate that biochar application in Fe oxide rich soils may be an effective strategy to sequester biochar carbon, as well as to stabilize native soil carbon.

Aggregation-dependent electron transfer via redox-active biochar particles stimulate microbial ferrihydrite reduction

Microbial Fe(III) reduction plays an important role for biogeochemical carbon and iron cycling in sediments and soils. Biochar is used as a soil amendment to increase fertility and lower N2O/CO2 emissions. It is redox-active and can stimulate microbial Fe(III) mineral reduction. It is currently unknown, however, how the aggregation of cells and Fe(III) minerals with biochar particles influence microbial Fe(III) reduction. Therefore, we determined rates and extent of ferrihydrite (Fh) reduction in S. oneidensis MR-1 cell suspensions with different particles sizes of wood-derived Swiss biochar and KonTiki biochar at different biochar/Fh ratios. We found that at small biochar particle size and high biochar/Fh ratios, the biochar, MR-1 cells and Fh closely aggregated, therefore addition of biochar stimulated electron transfer and microbial Fh reduction. In contrast, large biochar particles and low biochar/Fh ratios inhibited the electron transfer and Fe(III) reduction due to the lack of effective aggregation. These results suggest that for stimulating Fh reduction, a certain biochar particle size and biochar/Fh ratio is necessary leading to a close aggregation of all phases. This aggregation favors electron transfer from cells to Fh via redox cycling of the electron donating and accepting functional groups of biochar and via direct electron transfer through conductive biochar carbon matrices. These findings improve our understanding of electron transfer between microorganisms and Fe(III) minerals via redox-active biochar and help to evaluate the impact of biochar on electron transfer processes in the environment.

Production, Characterization and Observation of Higher Carbon in Sargassum wightii Biochar From Indian Coastal Waters

Ajith, S.; Rojith, G.; Zacharia, P.U.; Nikki, R.; Sajna, V.H.; Liya, V.B., and Grinson, G., 2019. Production, characterization and observation of higher carbon in Sargassum wightii biochar from Indian coastal waters. In: Jithendran, K.P.; Saraswathy, R.; Balasubramanian, C.P.; Kumaraguru Vasagam, K.P.; Jayasankar, V.; Raghavan, R.; Alavandi, S.V., and Vijayan, K.K. (eds.), BRAQCON 2019: World Brackishwater Aquaculture Conference. Journal of Coastal Research, Special Issue No. 86, pp. 193–197. Coconut Creek (Florida), ISSN 0749-0208.Seaweed farming gains significance as a climate resilient strategy owing to significant carbon sequestration potential and research advances to valorize products from seaweed resources. Conversion of seaweeds to biochar enhances further carbon sequestration. In this study Sargassum wightii, belonging to brown algae has been converted into biochar under different conditions of pyrolysis for possible application in aquaculture sector. The prepared biochar was subjected to elemental (CHNS) analysis to assess the nutrient profile. Further, comparative analysis has been done on raw seaweed and biochar based on the structural characterization using SEM, XRD and FTIR spectra. Functional group changes were evidenced from FTIR and XRD spectra, whereas surface modifications were elucidated by SEM analysis. The optimum temperature for biochar pyrolysis of S. wightii to yield higher carbon content has been identified. A significant observation is that seaweeds in Indian coastal waters are capable of higher carbon sequestration than in other waters.

Biophysical Potential of Crop Residues for Biochar Carbon Sequestration, and Co‐benefits, in Uganda

To what extent greenhouse gas emissions could be offset by soil biochar amendment is hotly debated. Residues from staple food crops are an obvious and promising choice, for gasifier energy appliances and biochar production in farming system of tropical Africa, for example, Uganda. Yet until now, the quantities of biomass residues from staple crops available for these technologies and their potential carbon sequestration have not been comprehensively investigated. Our interdisciplinary research demonstrates that biochar from unused biomass waste on farms in Uganda presents substantial opportunities for mitigation of climate change, generation of low-carbon energy, and intensification of agriculture. Photo credit: D. Roobroeck. Photo credit: D. Roobroeck. These photographs illustrate the article “Biophysical potential of crop residues for biochar carbon sequestration, and co-benefits, in Uganda” by Dries Roobroeck, Rebecca Hood-Nowotny, Dianah Nakubulwa, John-Baptist Tumuhairwe, Jackson Majaliwa, Isaac Ndawula, and Bernard Vanlauwe published in Ecological Applications. https://doi.org/10.1002/eap.1984

Effect of feedstock and microwave pyrolysis temperature on physio-chemical and nano-scale mechanical properties of biochar

Biochars were produced from softwood chips (spruce–fir mix) and hemp stalk biomasses in an in-house-developed microwave pyrolysis reactor. A kilogram batch raw biomass mixed with 10 wt% microwave absorber was pyrolyzed at 60-min residence time. Microwave power levels were set at 2100, 2400, and 2700 W with optimum heating rates ranging 25–50 °C/min. The proximate analysis indicated a progressive gain in biochar carbon content with power level increase. Both biochars showed a H:C ratio of < 1.2 with a graphite-like structure, which is an important observation for their potential use as a filler in bio-composites structural strength increase. Fourier Transfer Infrared (FT-IR) spectra showed a major loss of functional groups as the power level increased. Brunauer–Emmett–Teller (BET) surface area and porosity distribution contained higher volume of smaller pores in the hemp biochar. The char hardness and Young’s modulus, obtained via nanoindentation technique and load–depth curve analysis, indicated that hemp biochar possessed a higher Young’s modulus and lower hardness than softwood chip biochar.