Utilization of the saccharification residue of rice straw in the preparation of biochar is a novel strategy for reducing CO2 emissions

Effects of cellulase treatment on properties of lignocellulose-based biochar

As the most abundant renewable carbon source, lignocellulose holds potential as a raw material for biofuels and biochar. The components required for biofuel production differ from those for biochar, so combining processes can reduce costs. Biofuel preparation necessitates cellulase treatment of lignocellulose. This study examines the effects of various enzyme treatment conditions (dosage, time, temperature) on lignocellulose, focusing on the properties of biochar derived from it (BC-SR). A mathematical model was constructed to study the relationship between enzyme treatment conditions and BC-SR properties. BC-SR exhibited high adsorption selectivity for bisphenol A and outperformed untreated biochar in fixed-bed column experiments, demonstrating greater removal efficiency and structural integrity. This study provides insights into the impact of enzymatic treatment on biochar and offers a cost-effective method for producing stable, efficient biochar. Additionally, a highly persistent biochar can enter the carbon trading market as a carbon-neutral technology, further realizing economic and environmental benefits.

Biochar promotes microbial CO2 fixation by regulating feedback inhibition of metabolites

Chemoautotrophs, the crucial contributors to biological carbon fixation, derive energy from reducing specific inorganic substances and utilize CO2 for growth. However, the release of extracellular free organic carbon (EFOC) by chemoautotrophic microorganisms can inhibit their own growth and metabolism. To reduce the feedback inhibition effect, a low-release biochar (BC-LR) was applied to adsorb EFOC. BC-LR not only adsorbed EFOC, but also selectively adsorbed the main inhibitory component, low molecular weight organics, in EFOC. In contrast, ordinary biochar could not effectively adsorb EFOC and its addition inhibited microbial growth and CO2 fixation. In Transwell culture, BC-LR promoted microbial growth by 190% and CO2 fixation by 29%, and exhibited better economic advantage, when compared with granular activated carbon. These findings provide a novel insight into the interaction between biochar and autotrophic microbial metabolism, offering an economically feasible approach to mitigate feedback inhibition of metabolites and promoting biological CO2 fixation.

Resource utilization of rice straw to prepare biochar as peroxymonosulfate activator for naphthalene removal: Performances, mechanisms, environmental impact and applicability in groundwater

Herein, biochar was prepared using rice straw, and it served as the peroxymonosulfate (PMS) activator to degrade naphthalene (NAP). The results showed that pyrolysis temperature has played an important role in regulating biochar structure and properties. The biochar prepared at 900°C (BC900) had the best activation capacity and could remove NAP in a wide range of initial pH (5-11). In the system of BC900/PMS, multi-reactive species were produced, in which 1O2 and electron transfer mainly contributed to NAP degradation. In addition, the interference of complex groundwater components on the NAP removal rate must get attention. Cl- had a significant promotional effect but risked the formation of chlorinated disinfection by-products. HCO3-, CO32-, and humic acid (HA) had an inhibitory effect; surfactants had compatibility problems with the BC900/PMS system, which could lead to unproductive consumption of PMS. Significantly, the BC900/PMS system showed satisfactory remediation performance in spiked natural groundwater and soil, and it could solve the problem of persistent groundwater contamination caused by NAP desorption from the soil. Besides, the degradation pathway of NAP was proposed, and the BC900/PMS system could degrade NAP into low or nontoxic products. These suggest that the BC900/PMS system has promising applications in in-situ groundwater remediation.

Effects of functional group loss on biochar activated persulfate in-situ remediation of phenol pollution in groundwater and its countermeasures

Biochar is considered a good activator for use in advanced oxidation technology. However, dissolved solids (DS) released from biochar cause unstable activation efficiency. Biochar prepared from saccharification residue of barley straw (BC-SR) had less DS than that prepared directly from barley straw (BC-O). Moreover, BC-SR had a higher C content, degree of aromatization, and electrical conductivity than BC-O. Although the effects of BC-O and BC-SR on activation of Persulfate (PS) to remove phenol were similar, the activation effect of DS from BC-O was 73% higher than that of DS from BC-SR. Moreover, the activation effect of DS was shown to originate from its functional groups. Importantly, BC-SR had higher activation stability than BC-O owing to the stable graphitized carbon structure of BC-SR. Identification of reactive oxygen species showed that SO₄•^-, •OH, and ¹O₂ were all effective in degradation by BC-SR/PS and BC-O/PS systems, but their relative contributions differed. Furthermore, BC-SR as an activator showed high anti-interference ability in the complex groundwater matrix, indicating it has practical application value. Overall, this study provides novel insight that can facilitate the design and optimization of a green, economical, stable, and efficient biochar-activated PS for groundwater organic pollution remediation.

Recycling utilization of Chinese medicine herbal residues resources: systematic evaluation on industrializable treatment modes

Traditional Chinese medicine (TCM) is an indispensable part of the world health and medical system and plays an important role in treatment, prevention, and health care. These TCM produce a large amount of Chinese medicine herbal residues (CHMRs) during the application process, most of which are the residues after the decoction or extraction of botanical medicines. These CMHRs contain a large number of unused components, which can be used in medical, breeding, planting, materials, and other industries. Considering the practical application requirements, this paper mainly introduces the low-cost treatment methods of CHMRs, including the extraction of active ingredients, cultivation of edible fungi, and manufacture of feed. These methods not only have low upfront investment, but also have some income in the future. Furthermore, other methods are briefly introduced. In conclusion, this paper can provide a reference for people who need to deal with CMHRs and contribute to the sustainable development of TCM.

Effect of dissolved solids released from biochar on soil microbial metabolism

Dissolved solids released from biochar (DSRB), including organic and inorganic compounds, may affect the role of biochar as a soil amendment. In this study, the effects of DSRB on soil microbe metabolism, especially CO₂ fixation, were evaluated in liquid soil extract. DSRB were found to be released in large amounts (289.05 mg L^-1 at 1 hour) from biochar over a short period of time before their rate of release slowed to a gradual pace. They increased the microbial biomass and provided energy and reducing power to microbes, while reducing their metabolic output of extracellular proteins and polysaccharides. DSRB inputs led to the redistribution of metabolic flux in soil microorganisms and an increased organic carbon content in the short term. This content gradually decreased as it was utilized. DSRB did not improve microbial CO₂ fixation but, rather, enhanced its release, while promoting specific soil microorganism genera, including Cupriavidus, Flavisolibacter, and Pseudoxanthomonas. These heterotrophic genera may compete with autotrophic microorganisms for nutrients but have positive synergistic relationships with autotrophs during CO₂ fixation. These results demonstrated that reducing the DSRB in biochar can improve its role as a soil amendment by enhancing soil carbon storage and CO₂ fixation capabilities.

Effect of rapeseed straw-derived biochar on soil bacterial community structure at tillering stage of Oryza Sativa

Numerous studies have reported the dynamics of microbes when biochar was applied, whereas the information on the alterations of bacterial community after application of rapeseed straw-derived biochar is limited. A pot experiment with two rapeseed straw-derived biochar application treatments (with biochar application at the rate of 200 g/pot, C1) and (without biochar application, 0 g/pot, C0) was conducted. No significant differences were observed in the number of operational taxonomic units, observed species, Shannon index, Simpson index, Chao1, ACE, and phylogenetic diversity whole tree between the C1 and C0 treatments. Taxonomic analysis at the genus level showed that the abundances of Gracilibacter, Lentimicrobium, unidentified Rikenellaceae, Hydrogenophaga, and Bacillus were higher in the C1 compared to the C0 treatment, while Candidatus Solibacter, Candidatus Koribacter, and Lutispora abundances were found to be higher abundant in the C0 compared to the C1 treatment. Obvious clusters were observed between the C1 and C0 in both principal component analysis and non-metric multidimensional scaling. These results indicate that soil bacterial community was altered after rapeseed straw-derived biochar was applied.

Integrated glycolysis and pyrolysis process for multiple utilization and cadmium collection of hyperaccumulator Sedum alfredii

Phytoremediation is a cost-effective and environmentally-friendly method to treat cadmium (Cd) contaminated soils, however, there is still a lack of safe disposal methods of harvested hyperaccumulators. In this study, by integrating glycolysis and pyrolysis, we investigated the possibility of bioproduct production and Cd collection from the hyperaccumulator Sedum alfredii. By means of acid-alkali pretreatment, the degree of cellulose polymerization was reduced by 36.24% while the surface accessibility was increased by 115.80%, resulting in a bioethanol yield of 9.29%. Meanwhile, 99.22% of total Cd of biomass could be reclaimed by collecting H₂SO₄-pretreatment waste. The saccharification residue was subsequently modified by NaOH-pretreatment-filtrate and converted into biochar at 500 °C which possessed a maximum Cd²⁺ sorption capacity of 60.52 mg g^-1 based on the Langmuir model. Furthermore, sustainability analysis indicated that the economic input of this process is acceptable when considering its good environmental benefits. Taken together, our study provides a strategy for simultaneous bioethanol and biochar production during Cd collection from the hyperaccumulator S. alfredii, which could be a promising alternative for the suitable treatment of metal-enriched plants.

Effect of straw decomposition on organic carbon fractions and aggregate stability in salt marshes

Straw addition can increase the content of soil organic carbon (SOC), and affect the content of aggregates and organic carbon fractions. The changes in aggregates and organic carbon fractions in the natural salt marsh, 10-year and 15-year freshwater pumping areas in the Yellow River Estuary were studied by 120-day field in situ culture experiments with Phragmites australis straw addition. The results showed that straw addition mainly enhanced the soil aggregate stability in the 10-year freshwater pumping area, and the organic carbon content of small macro-aggregates increased significantly by 26.36% (P < 0.05). In particular, the content of coarse particulate organic carbon (cPOC) with small macro-aggregates in all areas increased significantly with the addition of straw (P < 0.05). For small macro-aggregates in the 10-year pumping area, the cPOC contents increased significantly by 21.73 g/kg (P < 0.05); and were significantly higher than the fine particulate organic carbon (fPOC) and mineral-associated organic carbon (mSOC) contents, as the fPOC contents in micro-aggregates increased by 85.92% (P < 0.05). Additionally, the cPOC contents of small macro-aggregates and fPOC contents of micro-aggregates increased by 34.59% and 43.24% in the 15-year pumping area. The contents of mSOC were the lowest in different aggregates across all areas. Thus, straw addition had a significant effect on the contents of cPOC and fPOC, while freshwater pumping in the YRE could affect the distribution of fPOC and mSOC with aggregates.

Trace metal elements mediated co-pyrolysis of biomass and bentonite for the synthesis of biochar with high stability

The stability of biochar is a crucial parameter in determining the potential of biochar for carbon sequestration. Many studies have demonstrated that the addition of clay during the pyrolysis of biomass is beneficial for the production of biochar with a high stability, but finding a strategy for a further improvement of stability of clay-modified biochar is still highly desirable. Herein, the co-pyrolysis of biomass and clay mediated by trace metal elements is proposed as a new strategy for the production of biochar with exceptionally high stability. The results indicate that the biochar resistance index for biochar obtained from the trace metal elements mediated the co-pyrolysis of biomass and clay is ~0.75, which is much higher than that of biochars obtained from biomass pyrolysis or the co-pyrolysis of biomass and clay, demonstrating that the presence of metal ions during the co-pyrolytic process can significantly improve the oxidation resistance of biochar. Thermogravimetric analysis reveals that the carbon retention value is reduced when the addition of metal ions during the co-pyrolytic process, and the presence of metal ions can reduce the starting temperature of the pyrolysis reaction and catalyze the process of biomass pyrolysis. In addition, the percentages of CC, CC, and CH in all biochars obtained from trace metal elements mediated the co-pyrolysis of biomass and clay are greater than 41.82%, which are higher than that of original biochar. Besides, the percentage of oxygen-containing functional groups is found to be decreased after the presence of metal ions during the co-pyrolytic process. The presence of metal ions can form metal nano-sulfides and oxides on the surface, which plays a physical barrier to the anti-oxidation performance of biochar. Furthermore, compared to BBC or BC, MnBBC and ZnBBC have a better leaching resistance to P, while FeBBC has almost no leaching resistance to soil P. Overall, the study reveals that the addition of trace element metal ions during the co-prolysis of biomass and bentonite is an effective method to increase the stability of obtained biochar, and it is also beneficial for retarding the release of nutrients in the soil and thus increase the utilization of nutrients.

Reduction of Fermentation-Associated Stresses by Straw-Based Soluble Saccharides for Enhancing Ethanol Production

In this study, the effect of soluble polysaccharides (SPs) derived from agricultural waste, rice straw, on fermentation-associated stresses (temperature and concentrations of glucose and ethanol) was investigated to achieve high-performance ethanol production. The increase in temperature and concentrations of glucose and ethanol significantly inhibited Saccharomyces cerevisiae growth and lowered ethanol fermentation efficiency. Flow cytometric assays indicated that SPs could alleviate membrane permeability damage caused by fermentation-associated stresses. Atomic force microscopy and transmission electron microscopy revealed that fermentation-associated stresses induced cell surface shrinkage, causing a decrease in the cell size, whereas SPs stimulated the formation of extracellular matrices (EMs), which made the cell surface smooth and the cell morphology regular. Cells with EMs induced by SPs could efficiently produce ethanol under severe stresses. As a result, the titer of ethanol in the fermentation with SPs was 1.40-fold (from 26.40 to 36.98 g/L) higher than that in the fermentation without SPs, suggesting the stress-alleviating effect of SPs on ethanol production.

Simultaneous production of cellulase and ferulic acid esterase by Penicillium decumbens with rice straw as the sole carbon source

As well as cellulose and hemicelluloses, rice straw contains phenolic acids. The simultaneous production of monosaccharides and phenolic acids could improve the value of rice straw. In this study, it was confirmed that Penicillium decumbens produces more ferulic acid esterase (FAE) than other cellulase-producing fungi. Cellulose, destarched wheat bran (DSWB), and rice straw were used as carbon sources. Little phenolic acid was released by cellulose- and DSWB-based enzymes during the saccharification of rice straw, whereas rice straw was a favorable carbon source for the simultaneous production of cellulase and FAE. High-performance liquid chromatography showed that during enzyme production, phenolic acids were released from rice straw, and ball-milling affected this release of phenolic acids. Small amounts of phenolic acids induced FAE production. Although the enzymes produced with rice straw showed lower FAE activity than those produced with DSWB, phenolic acids were produced efficiently during the saccharification of rice straw in response to the synergistic effects of cellulase and FAE. Therefore, we suggest that the production of enzymes by P. decumbens on rice straw as the sole carbon source will allow the production of more valuable products from rice straw, making the utilization of rice straw more economic.