Environmental Technology

Luo, Liwen; Chu, Puiyan; Liang, Jialin; Johnravindar, Davidraj; Zhao, Jun; Wong, Jonathan W.C.

doi: 10.1080/09593330.2022.2157759pmid: 36524382

The influence of biochar on anaerobic digestion (AD) of organic waste have been widely studied. However, the effect of biochar on the mitigation of acidification and subsequently the stimulation of methanogenesis recovery during mono food waste (FW) digestion process under a low inoculum to substrate (I/S) ratio (i.e. a high organic loading) is rarely investigated. In this study, the benefit of biochar with respect to methane production from FW was explored in a mono FW AD system with four different additional amounts of biochar, i.e. 0, 5, 10 and 15 g/L. Results revealed that biochar boosted methane production in AD at a low I/S ratio by 390–530% through stimulating methanogenic activity, improving organics removal and enhancing process stability. The biochar dosage of 10 g/L demonstrated the highest biodegradability of 92.3% and the highest specific methane production of 553.0 mL/g VSremoved among all groups. Without biochar addition, volatile fatty acids (VFAs) accumulated to 20 g/L and the highest total ammonium-N (TAN) was > 1200 mg/L. The suppression of methanogenesis was significantly correlated with VFA and TAN (p < 0.05). Therefore, biochar addition presented a positive effect on VFAs degradation and buffering capacity which could be an effective approach to enhance methane production from FW digestion at a low inoculum to substrate ratio without the fear of system failure.

Johnravindar, Davidraj; Kumar, Rajat; Luo, Liwen; Jun, Zhao; Manu, M. K.; Wang, Hailong; Wong, Jonathan W. C.

doi: 10.1080/09593330.2022.2161949pmid: 36546529

High accumulation of volatile fatty acids (VFAs) is one of the major concerns during mesophilic anaerobic co-digestion of food waste (FW) and sewage sludge (SS). Therefore, improving the stability of the anaerobic digestion process could surpass quick acidification while accelerating methanogenesis. In this study, the suitability of biochar-assisted co-digestion was evaluated at different inoculum and substrate ratios (I/S ratios: 0.1, 0.3, 0.6, and 0.9). The maximum methane yield of 256.85 mL/gVSadd was observed at an I/S ratio of 0.6. The results indicated fast volatile solid removal (∼ 47.17% to 73%) and a critical role of biochar addition in alleviating the underlying inhibitions. Substantial changes in the microbial community composition including Methanosata, Methanobrevibacter, and Methanosarcina were also observed which predominated and stabilised the methanogenesis process at higher I/S ratios. These results emphasised that the anaerobic co-digestion of FW/sludge is a promising approach, wherein the biochar amendment at different I/S ratios should be well maintained to avoid inhibitions from excess microbial VFA acidification of organic waste feedstocks.

Li, Dongyi; Kumar, Rajat; Johnravindar, Davidraj; Luo, Liwen; Zhao, Jun; Manu, M. K.

doi: 10.1080/09593330.2022.2161950pmid: 36546563

Food waste digestate (FWD) disposal is a serious bottleneck in anaerobic digestion plants to achieve a circular bioeconomy. FWD could be recycled into nitrogen-rich compost; however, the co-composting process optimisation along with bulking agents is required to reduce nitrogen loss and unwanted gaseous emissions. In the present study, two different-sized bulking agents, namely, wood shaving (WS) and fine sawdust (FS), were used to investigate their impact on FWD composting performance along with the nitrogen dynamics. The mixing of FWD with different bulking agents altered the physiochemical characteristics of composting matrix and the effective composting performance was observed through reduced ammonium nitrogen and increased seed germination index during 28 days of composting. The carbon loss of 19–22% through CO2 emission indicated similar carbon mineralisation with both types of sawdust; however, the nitrogen transformation pathways were different. Only WS treatment demonstrated the nitrification process, whereas the nitrogen loss was higher with FS. A total nitrogen loss of ∼15% was observed in treatments with FS, whereas WS treatments displayed a nitrogen loss of 12%. The outcome of the present study could significantly contribute to the practical aspect of the FWD composting operation with the promotion of the bio-recycling economy.

Priyanka, Kumaresan; Umesh, Mridul; Preethi, Kathirvel

doi: 10.1080/09593330.2022.2164220pmid: 36579848

Massive accumulation of unprocessed banana peels enthralls sustainable issues as they are eventually dumped as landfills leading to emission of obnoxious gasses. To avoid these persisting challenges the present study shims lights on chitosan production from the characterised fungal strain using banana peel hydrolysate as an effective medium. Substantial amount of carbohydrate in banana peels serves as a potential solution for fungal chitosan production in a view to attain a circular bioeconomy and repurposed for synthesis of beneficial products in a cost effective manner. Presence of fermentable sugars in banana peels qualifies them as a feasible substrate which could be exploited for scaling up of fungal chitosan synthesis. Screened isolate was subjected to statistical optimisation using formulated medium to elucidate the influential factors that had significant effect on chitosan production. The harvested chitosan biomass was characterised through standardised techniques and evaluated for further studies. Statistical optimisation reveals that ammonium nitrate (5 g/L), pH (6) and incubation time (144 hrs) were the three PBD variables that had a greater influence on fungal chitosan yield. The validated developed model exhibited maximum yield of 200 mg/L, a 4.4 fold increase than unoptimised medium (45 mg/L). These findings emphasise the fermentative synthesis of chitosan through valorisation of banana peel prop up a complementary approach in concomitant with preserving renewable resources and bioproduct formation.

Goswami, Rahul Kumar; Agrawal, Komal; Mehariya, Sanjeet; Rajagopal, Rajinikanth; Karthikeyan, Obulisamy Parthiba; Verma, Pradeep

doi: 10.1080/09593330.2023.2166429pmid: 36621003

Microalgal-based bioprocess offers several advantages including wastewater reclamations, therefore present study assessed the usability of the combination of untreated municipal sewage wastewater (UTMSWW) and secondary treated municipal sewage wastewater (STSWW) for nutrient removal and recovery by Tetraselmis indica (T. indica) BDUG001. The present study optimized the additional nutrient supplementations (e.g. ASN-III) percentage and day-night cycle, pH and pH with aeration for monitoring high-rate biomass production and nutrient recovery. The study results showed that the combination of 75% UTMSWW + 25% ASN-III supported maximum biomass production (2.65 ± 0.07 g/L). In the optimized day-night cycle (12:12 h), T. indica BDUG001 showed improved biomass production (2.75 ± 0.07 g/L), biomass productivity (165.63 ± 4.42 mg/L/d), and photosynthetic pigments production. Under optimized pH∼ 7.0 with aeration, maximum total nitrate (TN) removal efficiency (87.67 ± 3.08–91.55 ± 1.92%) was observed, while COD and TP removal was maximum at pH ∼ 9.0. The maximum biomass production (2.35 ± 0.07–2.77 ± 0.04 g/L) with biomass productivity (93.75 ± 167.19 ± 2.21 mg/L/d) and lipid content (42.98 ± 1.86–47.85 ± 0.21% DCW) were also at pH 7.0. with aeration. The present study verified the utilization of UTMSWW with the combination of conventional medium, optimized day-night cycle, pH with aeration along with designing low-cost PBR. It was the ideal system for the cultivation of T. indica BDUG001 for the recovery of nutrients from wastewater, production of biofuels and value-added feedstock.

Kumari, Rekha; Sharma, Rozi; Sharma, Neeraj Kumar; Pant, Deepak; Malaviya, Piyush

doi: 10.1080/09593330.2023.2176259pmid: 36729847

Chemical fertilizers boost crop production; however, their continued use decreases soil fertility in the long run. Nutrient recycling by the beneficiation of poultry manure into biochar and application as a soil amendment is a long-term solution for plant nutrition. The effect of poultry manure, poultry biochar and crop irrigation with 50% and 100% greywater (GW) was assessed on soil properties and growth of wheat (Triticum aestivum L. HD-2967) on the 7th and 14th day of sowing. This resulted in greater nutrients (OC, OM, C:N have values of 3.51%, 6.58%, and 16.52, respectively) in soil on the 14th day after sowing irrigated with 100% GW for soil and 10 g biochar amendments than manure. The germination and growth were boosted to 100% on day 6 after seed sowing soil and 5 g biochar. The maximum number of leaflets (4), rootlets (7) and shoot length (26.58 cm) was obtained for soil and 10 g biochar amendments with 100% GW on the 14th day of sowing. The significance of the work is that greywater and poultry biochar has been used for the irrigation of wheat as a step towards the management of both solid and liquid waste. Biochar being a potential adsorbent reduces the pollutant load of greywater while increasing the nutritive value of soil substratum and influencing plant growth. The findings could offer crucial knowledge for creating agronomic procedures to repurpose the nutrients in poultry manure and biochar to grow crops by adding value to waste and meeting the goal of bioeconomic sustainability.

Srinivasan, Subramanian; Kaarmukhilnilavan, R.S.; Murugesan, Kumarasamy

doi: 10.1080/09593330.2023.2179943pmid: 36779287

Water resources are being heavily contaminated due to the huge load of toxic pollutants released by industrial activities. Among various physical and chemical methods, adsorption is considered as a promising method for rapidly removing contaminants from wastewater. In the present study, a novel carbon-based adsorbent was prepared through controlled pyrolysis of disposable facemasks. The properties of carbonized compound (CC) were characterized by FTIR, XRD, SEM and EDX. The pollutant removal efficiency of CC was initially investigated with synthetic dyes Malachite Green (MG) and Congo Red (CR). The peaks observed in FTIR spectra corresponding to C=O and C=C and C–N functional groups on adsorbed CC surface confirm the interaction between dye and CC. The XRD spectra of CC showed strong peaks at 2θ = 26.629, 27.488, 27.810 and 29.404 which correspond to the disordered graphitic plane. The SEM images of CC showed good porosity nature. A quadratic model was developed through response surface methodology by conducting a series of Box–Behnken design experiments. Adequacy of this model variables was ensured by ANOVA tests at P-value <0.05. The lower P-value (<0.0001) and higher F-value (44.54) of the quadratic model showed it was a significant model for dye removal. Finally, the optimal condition to obtain maximum MG removal (rate >99%) was identified by desirability function as CC 1000 and MG 212 mg/L and adsorption time 180 min. Adsorption kinetic study indicates that a pseudo second-order kinetic model showed the best fit with R 2 =  0.999.

Chakraborty, Debkumar; Palani, Sankar Ganesh; Ghangrekar, Makarand M.; Wong, Jonathan W.C.

doi: 10.1080/09593330.2023.2186272pmid: 36872877

The present work focused on extracting lactic and acetic acids from the leachate collected from leached bed reactor (LBR) during acidogenesis of food waste using the reactive extraction (RE) process. A wide range of diluents was screened either alone by physical extraction (PE) or in combination with extractants using RE to extract acids from the VFA mix. Aliquat 336-Butyl acetate/MIBK extractants in RE demonstrated higher distribution coefficients (k) and extraction yield (E %) than PE. The response surface methodology (RSM) was used to optimize the extraction of lactic and acetic acids from the synthetic acid mix, using three variables (extractant concentrations, solute/acid concentration and time). Consequently, these three variables were optimized for LBR leachate. The RE was promising, and extraction efficiencies of 65% (lactate), 75% (acetate), 86.2% (propionate) and almost 100% for butyrate and medium-chain fatty acids (MCFA) were achieved after 16 h of extraction. The RSM optimization predicted a maximum E % of 59.60% and 34.67% for lactate and acetate in 5.5 and 1.17 min, respectively. In the leachate experiment, an increase in E% and k was observed with increasing extractant concentration and lactate and acetate concentrations over time. Using a 1M reactive extractant mix and 1.25 and 12 g/L of solute concentrations, the maximum E % of acetate and lactate were 38.66% and 61.8% in 10 min. The results could contribute to developing a rapid in-situ product recovery system integrated with food waste acidogenesis for lactate and acetate recovery, contributing to the bio-economy.

Xia, Haihong; Li, Jing; Zhao, Jun; Zhou, Minghao; Jiang, Jianchun

doi: 10.1080/09593330.2023.2206526pmid: 37129277

Cyclopentanol (CPL) was an eco-friendly solvent as well as important platform chemical which could be generated from biomass-derived furfural (FFA). In this paper, a series of Ni, Cu, Mo, Co bimetallic catalysts with different metals loadings supported on carbon nanotubes (CNT) were synthesized by an impregnation method for aqueous-phase hydrogenation of FFA to obtain CPL. Various effects of reaction parameters such as reaction solvent, reaction temperature, reaction time and different loading amounts of Ni over bimetallic Ni-based CNT catalysts were fully investigated. Among the catalysts studied, (15 + 5) wt% NiCu/CNT catalysts showed a high conversion of FFA and 88% selectivity towards CPL in water and 96% selectivity towards acetal in methanol at the mild condition of 160℃, 2 MPa hydrogen and 4 h reaction time. NiCu bimetallic synergistic effect was interpreted through H2-TPR and NH3-TPD measurement and a possible pathway was proposed. The features of the CNT-supported catalysts were investigated via XRD, XPS, TEM, H2-TPR and NH3-TPD. The Ni and bimetallic NiCu catalysts synthesized in this work were inexpensive and simple, which made them a promising candidate for the conversion of biomass-derived FFA to CPL.

Dey Chowdhury, Sanket; Suhaib, K. Hasim; Bhunia, Puspendu; Surampalli, Rao Y.

doi: 10.1080/09593330.2023.2215458pmid: 37192135

To meet the current need for sustainable development, vermicomposting (VC), a natural, eco-friendly, and cost-effective technology, can be a wise selection for the bioconversion of organic wastes into value-added by-products. However, no one has tried to establish the VC technology as an economically sustainable technology by exploring its linkage to circular bioeconomy. Even, no researcher has made any effort to explore the usability of the earthworms (EWs) as a protein supplement while assessing the economic perspectives of VC technology. Very few studies are available on the greenhouse gas (GHG) emission potential of VC technology. Still, the contribution of VC technology towards the non-carbon waste management policy is not yet explored. In the current review, a genuine effort has been made to inspect the contribution of VC technology towards the circular bioeconomy, along with evaluating its capability to bioremediate the organic wastes generated from domestic, industrial, and agricultural premises. The potential of the EWs as a protein source has also been explored to strengthen the contribution of VC technology towards the circular bioeconomy. Moreover, the linkage of the VC technology to the non-carbon waste management policy has been comprehensively demonstrated by highlighting its carbon sequestration and GHG emission potentials during the treatment of organic wastes. It has been observed that the cost of food production was reduced by 60-70% by replacing chemical fertilizers with vermicompost. The implication of the vermicompost significantly lessened the harvesting period of the crops, thereby helping the farmers attain higher profits by cultivating more crops in a single calendar year on the same plot. Furthermore, the vermicompost could hold the soil moisture for a long time, lessening the water demand up to 30–40%, which, in turn, reduced the frequency of irrigation. Also, the replacement of the chemical fertilizers with vermicompost resulted in a 23% increment in the grapes’ yield, engendering an extra profit of up to 110000 rupees/ha. In Nepal, vermicompost has been produced at a cost of 15.68 rupees/kg, whereas it has been sold to the local market at a rate of 25 rupees/kg as organic manure, ensuring a net profit of 9.32 rupees/kg of vermicompost. EWs embraced 63% crude protein, 5–21% carbohydrates, 6–11% fat, 1476 kJ/100 g of metabolizable energy, and a wide range of minerals and vitamins. EWs also contained 4.11, 2.04, 4.43, 2.83, 1.47, and 6.26 g/kg (on protein basis) of leucine, isoleucine, tryptophan, arginine, histidine, and phenylalanine, respectively, enhancing the acceptability of the EW meal (EWM) as the protein supplement. The inclusion of 3 and 5% EWM in the diet of broiler pullets resulted in a 12.6 and 22.5% increase in their feed conversion ratio (FCR), respectively after one month. Similarly, when a 100% fish meal was substituted by 50% EWM and 50% fish meal, the FCR and growth rate of Parachanna obscura were increased substantially. The VC of maize crop residues mixed with pig manure, cow dung, and biochar, in the presence of Eisenia fetida EWs, yielded only 0.003–0.081, 0–0.17, and 130.40–189.10 g CO2-eq.kg−1 emissions of CO2, CH4, and N2O, respectively. Similarly, the VC of tomato stems and cow dung ensured 2.28 and 5.76 g CO2-eq.kg−1 CO2 emissions of CH4 and N2O, respectively. Additionally, the application of vermicompost at a rate of 5 t/ha improved the soil organic carbon proportion and aggravated carbon sequestration. The land application of vermicompost improved micro-aggregation and cut down the tillage, reducing GHG emissions and triggering carbon sequestration. The significant findings of the current review suggest that VC technology potentially contributes to the concept of circular bioeconomy, substantially negotiates potential GHG emissions, and complies with the non-carbon waste management policy, reinforcing its acceptability as an economically sound and environmentally benevolent organic waste bioremediation alternative.