Cow dung-derived biochars engineered as antibacterial agents for bacterial decontamination

Optimization of Vertical Fixed-Bed Pyrolysis for Enhanced Biochar Production from Diverse Agricultural Residues

This study examines the pyrolysis of agricultural residues, namely, coconut shells, rice husks, and cattle manure, in a vertical fixed-bed reactor at varying temperatures from 300 to 800 degrees Celsius for biochar production. The research aimed to evaluate the potential of biochar as biofuels, adsorbents, and soil amendments. Proximate, ultimate, and elemental analyses were conducted to determine their composition and caloric values. Several analytical techniques were used in the physical and chemical characterization of the biochar (SEM, FTIR, BET). The results indicated that the highest SBET values were achieved under different conditions for each biochar: 89.58 m2/g for BC-CS-700, 202.39 m2/g for BC-RH-600, and 42.45 m2/g for BC-CD-800. Additionally, all three biochars exhibited the highest caloric values at 600 °C. The results showed that 600 °C is the general optimal temperature to produce biochar from an assortment of biomass materials, considering their use for a variety of purposes. BC-CS-800 had the highest elemental carbon content at 93%, accompanied by a relative decrease in oxygen content. The van Krevelen diagram of biochar products shows that biochars derived from coconut shells and rice husks are suitable for use as fuels. Furthermore, FTIR analysis revealed the presence of oxygen-containing functional groups on the biochar surface, enhancing their pollutant adsorption capabilities. This study provides valuable insights into the scalable and environmentally sustainable production of biochar, emphasizing its role in improving soil quality, increasing energy density, and supporting sustainable agricultural practices.

Co-composting with cow dung and subsequent vermicomposting improve compost quality of spent mushroom

In order to determine a feasible degrading process for spent mushroom (SMS) with high lignin content, the present work used cow dung (CD), SMS, and a mixture of CD and SMS as substrates and evaluated the effects of vermicomposting on the microflora and the quality of composting products. Bacterial (R² = 0.548, P = 0.001) and fungal (R² = 0.314, P = 0.005) community both were different between composting and vermicomposting. Vermicomposting and substrates affected enzyme activities indirectly by affecting ammonium, pH, total carbon, richness, and bacterial community composition. These results suggested that appropriate regulation of environmental factors may increase microbial activity. An increase in ion-exchange capacity (up to 139.8%), pH (6.9%), and nitrate (71.1%) and a decrease in total carbon (31.2%) and carbon/nitrogen ratio (32.1%) in vermicomposting indicated that earthworms could further improve product quality. Co-composting with CD and integrated subsequent vermicomposting efficiently promoted the maturity of SMS.

Enhanced wastewater nutrients removal in vertical subsurface flow constructed wetland: Effect of biochar addition and tidal flow operation

Dissolved oxygen (DO) and carbon stock in substrate medium play a vital role in the nutrient removal mechanism in a constructed wetland (CW). This study compiles the results of dynamics of DO, ammonium N (NH₄⁺-N), nitrate (NO₃-N), sulfate (SO₄^-2), phosphate (PO₄^-3), chemical oxygen demand (COD), in three setups of vertical-flow constructed wetlands (TFCWs) (SB: substrate + biochar; SBP: substrate + biochar + Colocasia esculenta plantation; SP: substrate + Colocasia esculenta (SP), operated with tidal flow cycles. Experimental analyses illustrated the continuous high DO level (2.743-5.66 mg L^-1) in SB and SBP after the I and II cycle of tidal flow (72 h flooding and 24 h dry phase). COD reduction efficiencies increased from 15.75 - 61.86% to 48.55-96.80% after tidal operation among operating TFCWs. N (NH₄⁺-N) and N (NO₃-N) removal were found to be 88.16%, and 76.02%; 49.32, and 57.85%; and 40.23%, and 48.94 % in SBP, SP and SB, respectively. The theory of improved nitrification and adsorption through biochar amended substratum was proposed for TFCW systems. PO₄^-3 and SO₄^-2 removal improved from 22.63 to 80.50%, and 19.69 to 75.20%, respectively after first tidal operation in all TFCWs. The microbial inhabitation on porous biochar could promote the transformation of available P into microbial biomass and also helped by the plant uptake process while SO₄^-2 reduction in TFCWs could be mainly due to sulfate-reducing bacterial activity and nitrate reduction process, mainly facilitated by high DO and biochar addition in such setups. The study suggests that effluent re-circulation through tidal operation and biochar supplementation in the substratum could be an effective mechanism for the improvement of the working efficiencies of CWs operated with low energy input systems.

Modified bone char with C-MgO as a green antibacterial household water treatment filter: Comparing the microbial quality with refrigerator cartridge filters

The present study examines the efficiency of modified bone char (BC) with C-MgO nanoparticles (MBC-C-MgO) as media in a cartridge filter as an antibacterial agent to produce a new filter. The filters were operated in a continuous mode using a pre-static pump. MBC-C-MgO were produced and modified with sucrose through the co-precipitation method. The microbial quality of effluent water samples was compared with commercial refrigerator cartridge filters using a heterotrophic plate count (HPC) test and SEM analysis. The results showed that the effluent water from the filter with MBC-C-MgO media had the lowest HPC (177 CFU/mL) compared to bioceramic (271 CFU/mL) and carbon (500 CFU/mL) under similar experimental conditions after 4 months of operation. Maximum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) tests were determined using the broth dilution method on Escherichia coli (ATCC 25922) and Enterococcus faecalis (ACC 29212). The MIC results for E. faecalis and E. coli were 156.25 and 312.5 µg/mL, respectively. Furthermore, the MBC results for E. faecalis and E. coli were 312.5 and 625 µg/mL. The experimental results obviously showed the antibacterial properties of C-MgO nanoparticles and the MBC-C-MgO.