Digestion Of Food Waste Research Articles

Effect of biochar addition on the anaerobic digestion of food waste: microbial community structure and methanogenic pathways.

This study assessed the effects of the addition of biochar prepared at 700 °C with different dosages on the anaerobic digestion of food waste. The biochar addition at a concentration of 10.0 g/L increased the cumulative methane yield by 128%, and daily methane production was also significantly promoted. The addition of biochar derived from poplar sawdust significantly increased the relative abundance of dominant bacteria for anaerobic digestion by 85.54-2530% and promoted the degradation of refractory organic matter and the transfer of materials between the hydrolysis and acid production stages. Further analysis has demonstrated that Bathyarchaeia and hydrogenotrophic methanogens were enriched by the biochar addition. Meanwhile, the relative abundances of functional genes, including C5-branched dibasic acid metabolism, and pyruvate metabolism, were increased by 11.38-26.27%. The relative abundances of genes related to major amino acid metabolism, including histidine metabolism, lysine biosynthesis, and phenylalanine, tyrosine, and tryptophan biosynthesis, were increased by 11.96-15.71%. Furthermore, the relative abundances of genes involved in major replication and repair were increased by 14.76-22.76%, and the major folding, sorting, degradation, and translation were increased by 14.47-19.95%, respectively. The relative abundances of genes related to major membrane transport and cell motility were increased by 10.02 and 83.09%, respectively.

Assigning strategic COD flow to enhance denitrification coupled with anaerobic digestion and anammox for systematic upgradation of advanced nitrogen removal from food waste digestate

Anammox is a low-carbon and efficient technology for treating high-strength ammonium in food waste digestate (FWD). However, achieving superior low-nitrogen effluent levels to meet strict discharge standards remains challenging. This study proposes an anammox-based process that integrates simultaneous denitrification and methanogenesis (SDM), partial nitrification (PN), and simultaneous anammox and denitrification (SAD) to realize advanced nitrogen removal from FWD by strategically utilizing influent organic matter. The SAD process achieved an inorganic nitrogen removal efficiency of 94.0 %, with the anammox reaction contributing 96.0 %. Residual nitrate in the SAD effluent was recirculated into SDM, maintaining a removal efficiency of 95 %–97 %. Profiling wastewater and material flows in the integrated process showed a 97.2 % nitrogen removal efficiency, with effluent nitrogen levels meeting discharge standards (<70 mg/L for municipal sewer systems). 3D-fluorescence analysis indicated that quasi-humic acid was effectively removed through SDM. Soluble microbial by-products of FWD served as carbon source for the denitrifying bacteria in SAD. Controlling influent bypass flow and effluent recirculation allowed for strategic allocation of chemical oxygen demand (COD) flow, achieving a total removal efficiency of 71.8 %. SDM removed 45.8 % COD, followed by PN at 13.4 % and SAD at 12.6 %. Compared with those of conventional nitrification and denitrification process, the economic cost, greenhouse gas emission, and total environmental impact of this integrated process were reduced by 85.8 %, 35.8 %, and 84.1 %, respectively. This study provides new insights into the application of anammox-based process for attaining advanced nitrogen removal while minimizing environmental impact.

Effect of the inoculum mixing ratio on the anaerobic digestion of food waste: Reactor performance and microbial community

Anaerobic digestion (AD) of food waste (FW) needs to break the hydrolysis limit and improve efficiency. Mixed inoculants of different sources are often used to enhance AD performance, while the mechanism of interaction between mixed inoculants of different sources is uncertain. The effect of the mixing ratio of two different inoculants, Baijiu pit mud (PM) and anaerobic digested sludge (ADS), on the AD of FW was examined. Specifically, the five ratios of PM:ADS (1:0, 3:1, 1:1, 1:3, and 0:1, based on volatile solids) on the AD performance and microbial community were evaluated. Biogas production was 551.70 % higher under a PM:ADS ratio of 1:3 (408.62 mL/g VS) compared with a ratio of 0:1. The acidification rate in 1:3 was 84.05 % and it was 41.85 % higher than 0:1(42.2 %). The abundance of unclassified_f_Comamonadaceae (degradation of cellulose), Petrimonas (acid and hydrogen production) and Methanobrevibacter were higher following the PM addition. Furthermore, the abundance of key enzymes (F420 hydrogenase) and methane metabolism (ko00680) varied under different ratios of PM:ADS. These results suggest that the addition of PM promotes the acidification and methanogenic phases of the AD of FW.

Riboflavin modified carbon cloth enhances anaerobic digestion treating food waste in a pilot-scale system.

Previous laboratory-scale studies have consistently shown that carbon-based conductive materials can notably improve the anaerobic digestion of food waste, typically employing reactors with regular capacity of 1-20L. Furthermore, incorporating riboflavin-loaded conductive materials can further address the imbalance between fermentation and methanogenesis in anaerobic systems. However, there have been few reports on pilot-scale investigation. In this study, a 10m2 of riboflavin modified carbon cloth was incorporated into a pilot-scale (2m3) food waste anaerobic reactor to improve its treatment efficiency. The study found that the addition of riboflavin-loaded carbon cloth can increase the maximum organic loading rate (OLR) by 40% of the pilot-scale reactor, compared to the system using carbon cloth without riboflavin loading, while ensuring efficient operation of the reaction system, effectively alleviating system acidification, sustaining methanogen activity, and increasing daily methane production by 25%. Analysis of the microbial community structure revealed that riboflavin-loaded carbon cloth enriched the methanogenic archaea in the genera of Methanothrix and Methanobacterium, which are capable of extracellular direct interspecies electron transfer (DIET). And metabolic pathway analysis identified the methane production pathway, highly enriched on the reduction of acetic acid and CO2 at riboflavin-loaded carbon cloth sample. The expression levels of genes related to methane production via DIET pathway were also significantly upregulated. These results can provide important guidance for the practical application of food waste anaerobic digestion engineering.

The effects of microalgae use as a biofertilizer on soil and plant before and after its anaerobic (co-)digestion with food waste

The increase in food waste generation has resulted in significant challenges for its sustainable management. Anaerobic digestion coupled with microalgae-based ponds for digestate treatment can be used as a low-cost eco-friendly technology approach. In this case, microalgal biomass harvested from the ponds may be valorized into bioenergy (biogas) and soil conditioner and/or biofertilizers. The aim of the present study was to evaluate the microalgal biomass produced from a food waste digestate treatment ponds as agricultural fertilizer. For this purpose, microalgal biomass was tested before and after anaerobic digestion and co-digestion with food waste, exploring its potential for valorization. The inorganic fertilizer urea and soil with no fertilization were also used as treatments. The experimental design consisted of applying the treatments in pots cultivated with hybrid grass Brachiaria cv. Sabiá and distributed in randomized blocks in a controlled greenhouse. Microalgal biomass was mainly composed by Scenedesmus sp.. The assessed parameters showed comparable results on plant growth (i.e. number of tillers, fresh and dry matter and Chlorophyll content index) for fresh and digested microalgal biomass and inorganic fertilizer. Furthermore, it was observed that fresh microalgae provided the highest Phosphorus content in the leaf (21 %). Additionally, there were increases of 9 % in Nitrogen and 12 % in organic matter in the soil after applying digested microalgae compared to the control group without any fertilization. Finally, experimental data obtained suggests that microalgae-based biofertilizer holds the potential to replace inorganic fertilizer as a nutrient source. Moreover, it contributes to the valorization of by-products from organic waste treatment.

Waste-green infrastructure nexus: Green roof promotion by digestate and digestate biochar from food waste

Waste—Green Infrastructure Nexus is crucial to mitigate carbon emissions in waste disposal and promote eco-functions of green infrastructure in a circular bio-economy. Our purpose is to verify the feasibility of the nexus via “food waste anaerobic digestion — digestate/digestate biochar — green roof promotion”. The results found that food waste digestate and digestate biochar significantly promoted green roof plant growth, evapotranspiration, rainwater retention, runoff reduction, and prevention of nutrient leaching. Digestate treatments were better than digestate biochar for the green roof promotion. The promotion ranked consistently with 20 % digestate > 10 % digestate > 20 % digestate biochar > 10 % digestate biochar > control in stolon growth, leaf emergence, branching of Paspalum vaginatum, green roof establishment, rainwater retention, runoff reduction, and the leaching of nitrogen, phosphorus, potassium. This study demonstrated that food waste could be regenerated to promote urban green infrastructure to form a circular bio-economy by the Waste—Green Infrastructure Nexus.

High-efficiency anaerobic digestion of soybean curb residue with simultaneous phosphorus recovery by Mg[sbnd]Fe layered double hydroxides addition

Anaerobic digestion of food waste faces several technical problems, such as process failure caused by over-acidification, low heating value of biogas, and high treatment cost of liquid digestate. Layered double hydroxides (LDH) are expected to simultaneously enhance biogas production and quality and immobilize soluble phosphorus in AD due to their excellent anion exchange capability. This study first verified the above hypothesis, indicated by a dramatically enhanced methane yield of 17 folds under a high substrate load and a high quality of generated biogas with 89 % methane content and 90 % lowered hydrogen sulfide. Meanwhile, the soluble phosphorus was efficiently reduced to 3 mg/L after AD. Moreover, the calcined product of LDH showed comparable performance, indicating the possibility of reusing LDH in the AD process. The above results implied the great potential of LDH as a multifunctional material for enhancing the efficiency of waste treatment and energy/resource conversion in the AD process.

Hydrothermal-enhanced pyrolysis for efficient NOX reduction and biochar valorization from food waste digestate

Pyrolysis has emerged as a promising technology for valorizing digestate resulting from the anaerobic digestion of food waste. However, the high NOX emissions during pyrolysis limit its application. This study proposed a hydrothermal coupled pyrolysis process to control the element transfer in digestate during biochar production. The efficient reduction of NOX emissions and the improvement of biochar adsorbability were realized. The hydrothermal process reduced the nitrogen content in solid digestate by 49.10 %–81.79 %, thus reducing the NOX precursors in syngas and the N-containing substances in bio-oil. Additionally, the specific surface area and the total pore volume of biochar were enhanced from 25 m2/g to 60–73 m2/g and 0.06 cm3/g to 0.12–0.14 cm3/g, respectively. More defects, oxygen-containing functional groups, and doped Ca on the biochar resulted in a high phosphate removal efficiency of 94 %. The proposed technology provides an efficient and environmentally friendly way to utilize the digestate.

New insight of combined hydrothermal and ultrasonic pretreatment for methane production from anaerobic digestion of food waste

ABSTRACT Food waste (FW) biotransformation into bioenergy has garnered a lot of scientific interest as a way to address the energy crisis and trash disposal issues. FW is converted into biogas, a gaseous combination of biomethane and carbon dioxide. In order to valorize FW, anaerobic digestion (AD) with combined pretreatment (hydrothermal (HT) and ultrasonic (US)) is used as a potential method. Three digesters were investigated: the control (unpretreated), HT(121°C) + US, and HT(134°C) + US, respectively. Based on changes in the combined pretreatment conditions, the paper assessed the methane productivity. Furthermore, kinetic modeling was evaluated with six kinetic models. The results show that the HT pretreatment at 121°C combined with US improves the volatile solid (VS) removal to 73 ± 5% and the methane yield to 529.7 ± 11 NmL/gVS. Both the Transference model and the first order have the greatest fits in terms of R2, and they also have the best fits in terms of relative errors, and methane production rate, respectively. The combined pretreatment has a positive impact on increasing methane yield as well as stabilizing the anaerobic digestion process.

Influence of Nitrogen Content in Food Waste on Biogas Production

AbstractHigh carbon content and high‐level biodegradability are major constraints of the anaerobic digestion of food waste. In the present study, anaerobic digestion of model food waste was carried out in a fed batch digester. Nitrogen content in model food waste was adjusted by the addition of ammonium chloride at the desired C/N ratio. Biogas production at ammonium chloride percentages of 0, 0.8, 1.5, 2.14, and 3.2 % (weight basis) were carried out under mesophilic conditions in a pilot plant scale floating drum digester. At an ammonium chloride percentage of 1.5 % that balances C/N ratio 25, highest biogas production of 0.42 m3 kg−1 of VS was attained while biogas production from food waste without ammonium chloride of 0.06 m3 kg−1 of VS was obtained. The highest methane yield of 0.323 m3 kg−1 of VS was found at ammonium chloride of 1.5 % while methane yield of 0.042 m3 kg−1 of VS was achieved from food waste without ammonium chloride. The highest percent increase CH4 yield of 669 % was obtained at an ammonium chloride percentage of 1.5 %. Biogas productivity obtained at ammonium chloride percentage of 1.5 % was 0.6 L L−1 d−1. Hence, the optimum ammonium chloride percentage obtained was 1.5 % which balances the C/N ratio at 25.

Improving anaerobic digestion performance after severe acidification: Unveiling the impacts of Fe3O4-bentonite composites in co-digestion of waste activated sludge and food waste

Acidification recovery in anaerobic digestion of food waste is challenging. This study explored its in-situ recovery using a co-substrate of food waste and waste activated sludge. Fe3O4 and bentonite were used as conductor and carrier, respectively, to enhance AD performance under severe acidification. The application of Fe3O4-bentonite resulted in a 152% increase in cumulative methane in the Fe3O4-bentonite 10 digester, demonstrating its effectiveness in restoring the acidified AD system. In acidified systems, bentonite enhanced the diversity and richness of microbial communities due to its buffering capacity. The excessive non-conductive polysaccharides excreted by bacteria in extracellular polymeric substances reduced the possibility of electron transfer by Fe3O4. However, in the synergistic application of Fe3O4 and bentonite, this resistance was alleviated, increasing the possibility of direct interspecies electron transfer, and accelerating the consumption of volatile fatty acids. This approach of integrating carrier and conductive materials is significant for in-situ restoration of acidified systems.

Investigating the potential of mineral precipitation in co-pyrolysis biochar: Development of a novel Cd (II) adsorption material utilizing dual solid waste

Ionic cadmium (Cd (II)) in water is a significant threat to ecosystems, the environment, and human health. Research is currently focused on developing efficient adsorption materials to combat Cd (II) pollution in water. One promising solution involves co-pyrolyzing solid residue from anaerobic digestion of food waste with oil-based drill cuttings pyrolysis residue to create a biochar with high organic matter content. This biochar has a lower heavy metal content and leaching toxicity compared to China's national standards, making it both safe and resourceful. It exhibits a high adsorption capacity for Cd (II) in water, reaching up to 47.80 ± 0.37 mg/g. Raising the pyrolysis temperature above 600 °C and increasing the amount of pyrolysis residue beyond 30 % enhances the biochar's adsorption capacity. The adsorption process is primarily driven by mineral precipitation, offering a promising approach for dual waste resource management and reducing heavy metal pollution.

Effects of microbial electrolysis cell on anaerobic digestion of food waste: Acidification and recovery

The effects of a microbial electrolysis cell (MEC) applying 1.2 V on the acidification and recovery in the anaerobic digestion (AD) of food waste were studied by semi-continuous experiments. The experimental results showed that the MEC reduced the accumulation of volatile fatty acids (VFAs), enhanced acidification, accelerated the conversion of VFAs during recovery, and accelerated recovery by decreasing the relative abundance of Aminobacterium and norank_f__W27 and increasing that of Methanobacterium. The MEC reduced the production of propionic and butyric acids by decreasing the abundance of functional enzymes (such as fumarate reductase, propionate CoA-transferase, phosphate butyryltransferase, and butyrate kinase) and bacteria (such as Aminobacterium and norank_f__W27). The MEC increased the rates of four AD steps with a maximal rate of 11.47–32.32 %. The MEC promoted electron transfer by enriching the electroactive bacterium Trichococcus (10.91–28.80 %) and Methanosaeta (8.17–24.43 %). The MEC increased the abundance of the most critical functional enzymes in the bacterial community during the entire test and those in the archaeal community during recovery.

The Impact of Raw and Composted Food Waste Anaerobic Digestates on Soil Organic Carbon Management: A Pot Study

PurposeEver increasing food waste production has promoted anaerobic digestion and composting for its proper management, producing a relevant amount of recycled organic waste (OW) for possible agricultural uses. However, little is known regarding soil carbon management using this type of OW.MethodsIn this study, an anaerobic digestate from the wet digestion of food waste (WETD), and one from the dry-batch process (DRYD), along with their respective composts (WETC and DRYC), were utilized in a pot test over two growing cycles (84 + 84 days), with and without mineral nitrogen (N) fertilization, and were compared with a bio-waste compost (BWC) and a chemical reference (Chem). At the end of the two growth cycles (days 84 and 168), the ryegrass dry biomass (DW) and the N uptake were assessed.ResultsThe pot soil was analyzed for soil organic carbon (SOC) and the potassium permanganate (KMnO4) oxidizable fraction (CL) as well as δ13C and Δ13C. At day 84, the SOC (g kg− 1) was the highest in DRYD and DRYC (8.53) > WETD and WETC (7.71) = BWC (7.86) > Chem (6.68), and performed similarly at day 168. At day 84, the carbon management index (CMI) was > 100% in all the organic treatments in comparison with Chem, except for WETD. At day 168, a + 30% CMI was registered in WETD and WETC> BWC> DRYD and DRYC> Chem.ConclusionThis pattern was related to a generally marked δ13C depletion being confirmed by Δ13C, thus indicating the conservation of the carbon form compost, this very likely being related to the preferential lignin accumulation.

Synergistic treatment of sewage sludge and food waste digestate residues for efficient energy recovery and biochar preparation by hydrothermal pretreatment, anaerobic digestion, and pyrolysis

The safe disposal of sewage sludge (SS) and food waste digestate residues (DR) is a tough issue considering the difficulty of dewatering and the environmental risks from heavy metals and pathogens. This study combined hydrothermal pretreatment (HP), anaerobic digestion (AD), and pyrolysis to synergistically dispose of SS and DR to enhance dewaterability, recover energy, and prepare biochar with heavy metal immobilization. The results showed that the solid contents of centrifuged cakes increased after HP at 180 °C of SS with the addition of 25% and 50% mass fractions of DR. The centrate from co-HP had a high chemical oxygen demand (COD) and was further treated by AD at 37 °C, producing 193.75 and 210.39 mL/g CODinput (25 °C and 1 atm) of cumulative CH4 under the addition of 50% and 75% mass fractions of DR, respectively. The methanogenic types in AD converted from hydrogen utilization to acetic acid utilization with increasing DR ratio. Zn, Cu, Ni, and Pb were primarily left in the biochar after 50% mass fraction of DR was mixed in the HP combined with pyrolysis at 700 °C; the chemical fractionation of Zn, Cu, Cr, and Pb in the biochar increased to over 85% of the residual fractions, resulting in the lowest potential ecological risk index (15.22, low risk). The CH4 produced from the AD of the co-HP centrate (50: 50, w/w) can supply heat for the HP process, reducing the energy input by 89%. This co-disposal strategy can effectively recover carbon resources from solid wastes to reduce carbon emissions.

Multi-stage aeration regime to regulate organic conversion toward gas alleviation and humification in food waste digestate composting

Aerobic composting has been considered as a pragmatic technique to convert food waste digestate into high-quality biofertiliser. Nevertheless, massive gaseous emission and immature product remain the primary challenges in food waste digestate composting. Thus, the performance of multi-stage aeration regimes to improve gaseous emissions and organic humification during food waste digestate composting was investigated in this study. In addition to continuous aeration with a constant intensity of 0.3 L kg·dry mass (DM)−1·min−1, two multi-stage decreased aeration regimes were designed as “0.3-0.2-0.1” and “0.3-0.1-0.1” L·kg·DM−1·min−1 from the thermophilic to cooling and then mature stages, respectively. Results showed that the decreased aeration regimes could alleviate nitrous oxide (N2O) and ammonia (NH3) emission and slightly enhance humification during composting. The alleviated N2O and NH3 emission were mainly contributed by abiotically reducing gaseous release potential as well as biotically inactivating denitrifers (Pusillimonas and Pseudidiomarina) and proliferating Atopobium to reduce nitrate availability under lower aeration supply. The “0.3-0.2-0.1 L kg·DM−1·min−1” regime exhibited a more excellent performance to alleviate N2O and NH3 emission by 27.5% and 16.3%, respectively. Moreover, the decreased aeration regimes also favored the enrichment of functional bacteria (Caldicoprobacter and Syntrophomonas) to accelerate lignocellulosic biodegradation and thus humic acid synthesis by 6.5%–11.2%. Given its better performance to improve gaseous emissions and humification, the aeration regime of “0.3-0.2-0.1 L kg·DM−1·min−1” are recommended in food waste digestate composting in practice.

Enhancement of Anaerobic Digestion from Food Waste via Ultrafine Wet Milling Pretreatment: Simulation, Performance, and Mechanisms

Particle size reduction is a commonly used pretreatment technique to promote methane production from anaerobic digestion (AD) of food waste (FW). However, limited research has focused on the effect of micron-sized particles on AD of FW. This research presented an ultrafine wet milling (UFWM) pretreatment method to reduce the particle size of FW particles. After four hours of milling, D90 was reduced to 73 μm and cumulative methane production boosted from 307.98 mL/g vs. to 406.75 mL/g vs. without ammonia inhibition. We evaluated the performance of the AD systems and explored their facilitation mechanisms. Kinetic analysis showed that the modified Gompertz model predicted experimental values most accurately. UFWM pretreatment increased the maximum methane production rate by 44.4% and reduced the lag time by 0.65 days. The mechanical stress and collisions of milling resulted in a scaly surface of the particles, which greatly increased the voids and surface area. A rise in the XPS peak area of the C–N and C=O bonds proved the promotion of the liberation of carbohydrates and fats. Further microbial community analysis revealed that the relative abundance of Bacteroidota and Methanosarcina were enriched by UFWM. Meanwhile, methane metabolism pathway analysis confirmed that module M00567, module M00357, and related enzymes were stimulated. This study provided a theoretical basis for UFWM pretreatment applications and improvements in AD of FW.

Unveiling the bioaugmentation mechanism of Clostridium thermopalmarium HK1 enhancing methane production in thermophilic anaerobic digestion of food waste

To enhance methane production and ensure system stability in the thermophilic anaerobic digestion (TAD) of food waste (FW), bioaugmentation is a straightforward and effective strategy. This study investigated the bioaugmentation effect of Clostridium thermopalmarium HK1 on the TAD of FW. The results showed that the cumulative methane production (CMP) and the average methane content after bioaugmentation increased by 23.67% and 22.69%, respectively. Moreover, the addition of C. thermopalmarium HK1 contributed to alleviating ammonia inhibition and promoting volatile fatty acids (VFAs) conversion, thus maintaining the system stability. The dominant hydrolytic bacteria and hydrogenotrophic methanogens were enriched in the early stage after bioaugmentation. The genus Clostridium was positively correlated with methane content. Metagenomic analysis further suggested that methane metabolism was strengthened, and the relative abundances of genes encoding the key functional enzymes associated with hydrogenotrophic and acetoclastic methanogenic pathways were enhanced. Therefore, bioaugmentation with C. thermopalmarium HK1 had great potential for improving the efficiency of the TAD of FW.

Leaching characteristics of nutrients in food waste digestate-derived biochar

Food waste anaerobic digestion requires proper utilization of solid digestate, and pyrolysis emerges as an effective method to produce nutrient-rich biochar. This study investigated the leaching characteristics and speciation changes of nutrients in food waste digestate (FWD)-derived biochar pyrolyzed at 350 °C (BC350), 450 °C (BC450), and 550 °C (BC550). BC350 featured inorganic nitrogen, while BC450 and BC550 contained elevated organic nitrogen. Nitrogen, potassium, and dissolved organic carbon were released via a quick surface wash-off process. Polyphosphates prevailed in BC350 and leached through a fast diffusion-controlled process. BC450 and BC550 were dominated by Ca/Mg orthophosphates and released via a slow dissolution-controlled process. Leachates from BC450 and BC550 stimulated the shoot length of wheat seeds. After 5 leaching cycles, there were more aromatic dissolved organics, and BC450 and BC550 exhibited higher abundance of C-N and O-P-O. Overall, pyrolysis of FWD at 450 °C and 550 °C shows potential in producing slow-release biochar fertilizers for resource recycling.

Isolation of ammonium bicarbonate by reactive distillation of food waste digestate liquor

Distillation is among the best techniques for management of ammoniacal nitrogen in anaerobic digestate; however, the suitability of the conventional system is neglected in favor of using more advanced setups. This investigation proves the reliability of the classical batch distillation apparatus for high throughput separation of solid crystals of ammonium bicarbonate from food waste digestate (FWD) liquor. Three replicates were carried out: 80 g of FWD liquor with a content of 50 g/L NH4HCO3 was processed for 7.5 h under minimum heating power (<60 °C) and 200 rpm to avoid excessive foam formation. After performing the reactive distillation, 81 % of NH4HCO3 was recovered as white solid crystals at the top of the distillation still. Although the distillation provided a solid material with the same structure and composition as those of the reagent-grade NH4HCO3, the stability of the isolated inorganic fertilizer was poorer, and it could lead to pollution swapping.