Fertilizer Demand Research Articles

Enhancing phosphorus use efficiency in wheat grown on alkaline calcareous soils

Phosphorus (P) use efficiency is crucial for sustainable wheat production, particularly on alkaline calcareous soils. This study investigates the relative importance of two factors; P acquisition efficiency (PAE) and P utilization efficiency (PUtE), in determining P use efficiency (PUE) in wheat. A field trial with ten wheat genotypes was conducted under two P levels (no P application and P application at 110 kg P2O5 ha−1). Results revealed significant genetic variability in PUE, PAE, and PUtE among wheat genotypes under varying P availabilities. Genotypes MK-4 and MK-8 exhibited superior PUE, making them ideal candidates for soils with differing P levels. PAE played a more substantial role in influencing PUE, with PUtE contributing less to the variability. The findings underscore the importance of improving PAE, particularly for wheat genotypes grown in P-deficient conditions. Moreover, selecting genotypes with lower grain P concentration can enhance PUtE, contributing to improved PUE. These insights can improve breeding efforts and crop management practices to enhance P use efficiency in wheat, ultimately reducing production costs and fertilizer demand, especially in P-limited alkaline calcareous soils.

Design and Experiment of an Electric Control Spiral-Pushing Feed Mechanism for Field Fertilizer Applicator

Due to the unique structural characteristics of the traditional spiral fertilizer applicator, the instantaneous filling coefficient cannot be determined, which is not conducive to achieving precise control of the fertilizer discharge rate. Therefore, a spiral-pushing fertilizer applicator has been designed. By using a structure of variable diameter and variable spiral pitch to squeeze fertilizer gradually, precise control of the fertilizer discharge is achieved. The study analyzes the effects of screw pitch, screw diameter, and rotational speed on the filling coefficient; it uses spiral pitch elongation percentage, spiral diameter elongation percentage, and rotational speed as experimental factors, and filling coefficient and particle axial velocity coefficient as experimental indicators. Through quadratic orthogonal rotation combination design experiments, the fertilizer discharge performance of the spiral-pushing fertilizer applicator was optimized. The experimental results indicate that for the filling coefficient, x1x2 has an extremely significant impact, while for the axial velocity coefficient of particles, x1 and x3 have an extremely significant impact. When the rotational speed x3 is 30 r/min, the optimized spiral pitch elongation percentage x1 is 189.82–200%, the spiral diameter elongation percentage x2 is 102.75–106.76, the filling coefficient is greater than 95%, and the particle axial velocity coefficient is less than 10%, achieving the best fertilizer discharge performance. An electrically controlled fertilizer discharge system was also designed, and bench tests were conducted on it. The results show that the average deviation between the fertilizer discharge performance of the spiral-pushing fertilizer applicator driven by the electrically controlled fertilizer discharge system and the preset value is 2.14%. This proves that, when the fertilizer demand changes, the fertilizer discharge flow can be adjusted through the electrically controlled fertilizer discharge system to achieve precise fertilization. This study provides a reference for the design of spiral fertilizer applicators.

Reuse of sediment as a soil conditioner in a semiarid region dominated by subsistence farming: sediment characterization at the regional scale and effects on maize crop

PurposeThe increasing demand for fertilizers and their rising prices has led to the search for new nutrient sources, especially in rural areas where family farming predominates. In this study, we assessed the potential of reusing sediment deposited in surface reservoirs as a soil conditioner in a semiarid region, focusing on two features: the characterization of sediment physicochemical properties at the regional scale and the effect of the substrate containing sediment on the growth and physiology of maize.MethodsSediment from the beds of 14 reservoirs was investigated, and two of them were used for the preparation of substrate for maize cultivation. Differences between the physicochemical properties of the sediments were analyzed using ANOVA and Tukey’s test at a significance level of 0.05. The experimental design of the plant experiment was entirely randomized, in a factorial arrangement of two sources and four doses of sediment: 25, 50, 75, and 100% of the economic dose of 100 t ha−1 previously proposed in the study region. Two treatments were considered as controls: a substrate containing only soil and a treatment containing soil and chemical fertilizer. The data for each treatment were submitted independently considering the doses and sediment sources, and the means were compared by Tukey’s test.ResultsIn general, nutrient contents were higher in the sediment of the surface reservoirs than in the soil. For instance, the concentrations of nitrogen and potassium were three to 10 times higher in the sediment, compared to the soil, and the organic matter content was up to six times higher. In the plant experiment, the dose and source of the sediments influenced all of the analyzed variables. The addition of sediments to the soil increased the chlorophyll content, photosynthesis rate, and growth of the leaves in relation to the treatment containing only soil. There were no significant differences between the biomass production and the plants’ nutrient extraction with the largest dose of the most enriched sediment when compared to the treatment with chemical fertilizer.ConclusionsThe experiment of maize plant growth showed the feasibility of using sediment deposited in reservoirs as a soil conditioner due to the enrichment of nutrients, organic matter, and fine particles. Therefore, sediment reuse has potential to improve livelihoods and food security, as well as contributing to a circular economy. However, prior analysis is required to avoid soil contamination and to set the most appropriate sediment dose, due to the high spatial variability of the sediment characteristics.

The spatial and seasonal variability of nutrient status in the seaward rivers of China shaped by the human activities

Understanding the riverine nutrient status is of paramount importance to the management of coastal ecosystems. This study investigated the spatial and seasonal variability of nutrient status in the seaward rivers of China at a national scale, using the latest observational data (2020–2023). A total of 126 rivers were considered, covering nearly all rivers in China that enter adjacent seas. The average flux of total nitrogen (TN) to the sea amounts to about 8968 tons d-1, while the total phosphorus (TP) and ammonium (AN) flux are about 329 tons d-1 and 276 tons d-1, respectively. In general, the river nutrient fluxes are higher in summer, with the Southern China (SC) showing higher levels than the Northern China (NC). This pattern is largely regulated by the spatio-temporal characteristics of runoff. By contrast, the spatio-temporal pattern of riverine nutrient concentration differs from it slightly. Riverine TN/TP concentration typically shows higher levels in NC, peaking in winter/summer, while the spatio-temporal variations of AN are minimal. The coal-fired heating prevalent in NC during winter causes severe atmospheric nitrogen pollutions, contributing to the heightened TN concentration in local rivers. At the meantime, the vast cropland in NC creates a substantial demand for the phosphorus fertilizer, responsible for the elevated TP concentration in northern rivers. The seasonal variation of TP concentration is mainly driven by rainfall, which exacerbates the loss of phosphorus from croplands into nearby rivers, leading to a simultaneous increase in riverine TP and turbidity levels during summer. This process is particularly pronounced in NC, due to elevated phosphorus levels in croplands and more concentrated summer rainfall. The present study suggests the crucial role of human activities in shaping the riverine nutrient status in China, which will be of practical significance for the future environmental management.

Effect of the Combined Nutrient Fertilization on Elephant Foot Yam under Coastal Condition

As the demand for chemical fertilizers has seen a steep upward trend which has resulted in damage of soil as well as human health. Integrated use of chemical fertilizers along with organic manures has been seen as a alternative method to reduce the dependence upon chemical fertilizers. Hence a the field experiment was carried out to study the effect of intergrated nutrient management practices on available nitrogen, phosphorus, potash in soil along with uptake and economics of elephant foot yam (Amorphophallus paeonifolius (Dennst.) Nicolsan) cv. Gajendra. The study was laid out in randomized block design with thirteen treatments with three replications. Corms were cut into pieces weighing 800 g for planting, dipped in cow dung slurry and placed for drying. After drying, they are placed in the pits and covered with soil. The treatments comprised of three levels of Farmyard manure (FYM) (20 t ha-1), Vermicompost (5 t ha-1), consortium bio fertilizer (5 Kg ha-1) and organic manures of different combinations. The observations of soil properties were recorded before and after harvesting. From the study it was observed that soil organic content was increased significantly due to the application of organic manures along with biofertilizers, whereas soil physical and chemical properties were unaffected.

In a nutshell: almond hull and shell organic matter amendments increase soil and tree potassium status

Abstract Background Crop residues used as organic matter amendments have been shown to release potassium (K) into the soil, promoting K cycling in agronomic systems. Orchard field trials are needed to evaluate K dynamics under almond hull and shell amendments, which contain high K concentrations. Methods Three field trials in commercial almond orchards were conducted to assess the effects of surface-applied almond hull and shell amendments on K cycling within plant and soil systems. Amendment K concentrations over time, soil exchangeable K, and tree K status were measured as well as decomposition rate and crop yield. Results Hulls and shells released K rapidly under irrigation and rainfall, significantly increasing soil exchangeable K in the upper 0–10 cm soil within 2–7 weeks. Amendments increased tree leaf K status within the first 1–3 years to varying degrees depending on site. Initial amendment K concentrations decreased by at least half by dry weight within the first 25.4 cm (10 inches) of water (irrigation and precipitation) within the irrigated zone. Conclusions Almond hulls and shells can increase soil and plant K status when used as amendments on the soil surface. This practice can address byproduct utilization issues, recycle potassium (K), and reduce orchard K fertilizer demand by replacing the majority of tree K demand. Growers can tailor application rates to meet orchard-specific K management goals. Off-ground harvest preserved the hull/shell organic layer over time and maximized K cycling. Hull/shell amendments applied on the soil surface cover more soil area within the irrigated wetted zone compared to banded K fertilizer. This practice can reduce reliance on K fertilizers and reduce associated costs while providing a convenient outlet for hulls and shells.

Organo-mineral Fertilizer Containing Struvite from Liquid Digestate for Cucurbita pepo L. Seedling Production

The increasing demand for sustainable fertilizers has made phosphorus recovery from waste a win–win solution. The present study shows the effects of two different types of organo-mineral fertilizers, derived from liquid digestate, on Cucurbita pepo L. (zucchini) seed germination and seedling growth. Organo-mineral fertilizers (OMF) were obtained from two biogas plants—one in Cyprus and one in Sardinia. In Cyprus, it was extracted from the digestate of mixed agricultural by-products. In Sardinia, it was extracted from the digestate of bovine slurry. Different treatment levels, compared with the traditional fertilizers, were applied in a nursery: (i) business-as-usual (0.04 g of N, 0.03 g of P2O5, 0.07 of K2O per seedling), (ii) half business-as-usual level, (iii) double business-as-usual level. Agronomic, physiological, and quality parameters were assessed. At the germination level, comparable results were shown for traditional fertilizers and OMF treatments. A significant rate-response effect was observed for leaf number and area. Cyprus OMF and traditional fertilizer showed a comparable trend with the highest value at the double business-as-usual level or fertilizer. A similar trend was observed for other biometric parameters and for fresh and dry biomasses. The highest total polyphenol and anthocyanin values were recorded under Cyprus OMF and traditional fertilizer treatments at the business-as-usual level. Cyprus OMF at the highest level (2BAU, business-as-usual) presents a comparable effect on seedling growth and to traditional fertilizers probably due to the use of different agro-industrial by-products and suggesting its potential use as an alternative nutrient supply.

Organic Fertilizer Marketing Strategy

The issue of waste management is a significant concern in the NTB Province, Indonesia. Mataram City produces 314 tons of waste per day, with the majority (273 tons) being sent to landfills. Similarly, West Lombok Regency generates 175.4 tons of waste daily, with only 01.76 tons allocated for landfill disposal. Notably, Kebon Kongok landfill serves as a disposal site for both areas. In addressing this waste issue, the Lingsar Regional Integrated Waste Processing Site (TPST) has emerged as a vital player, employing Black Soldier Fly (BSF) Bioconversion Technology to process organic waste. This aligns with the government's flagship program of achieving zero waste in West Nusa Tenggara by efficiently managing, reducing, and utilizing waste, ultimately contributing to economic development. One key aspect of the study pertains to the organic fertilizer market strategy at the UPTD Regional Waste Landfill of NTB Province. It aims to understand the Price Effect (X1), the Promotion Effect (X2), and their combined influence on demand (Y) for organic fertilizer. The research employs a quantitative descriptive method conducted at the UPTD TPA Regional Waste province BSF Lingsar Unit, involving 30 farmer respondents. Data is analyzed using Regression Analysis and Multiple Correlation (Multiple Regression Analysis) through the SPSS Program. Results indicate that respondents exhibit a high perception of demand for organic fertilizer. The Multiple Linear Regression model showcases the effects of Price and Promotion strategies on Demand. The F Test (Anova) confirms that both strategies significantly impact demand. Further analysis reveals that the Price strategy (X1) has no significant individual effect on demand, while the Promotion strategy (X2) partially influences demand. The Coefficient of Determination Test (R2) indicates that Price and Promotion strategies jointly contribute 40.5% to the demand for organic fertilizer, leaving the remaining 59.5% influenced by other independent variables. This research underscores the importance of strategic pricing and promotion in driving demand for organic fertilizer in Lingsar District, West Lombok Regency, and the broader implications for waste management and economic development in the NTB Province.

Analisis Kelayakan Investasi Alat Bioreaktor Anaerob Sebagai Reaktor Proses Fermentasi Nutrisi Organik

Farmers in Papungan Village, Blitar Regency, are experiencing problems, namely the lack of subsidized fertilizer from the government to meet the demand for fertilizer for their agricultural land. To meet this shortage, farmers apply organic nutrient fertilizers as a substitute for non-subsidized and chemical fertilizers, but the process of making organic nutrient fertilizers requires a long fermentation process, which is 16-30 days. Therefore it is necessary to have an Anaerobic Bioreactor to help speed up the fermentation. This tool is quite expensive for farmers in Papungan village, so it is necessary to analyze the level of investment feasibility of the Anaerobic Bioreactor tool to find out whether it is worth buying or investing. From the calculation results obtained NPV (Net Present Value) of IDR 9,266,620, IRR (Internal Rate Of Return) of 40.1513% and BCR (Benefit Cost Ratio) of 1.0289 so it can be concluded that the purchase of Anaerobic Bioreactors is feasible. Keywords: Bioreaktor Anaerob, Investment, Organic Nutrient Fertilize.

Does day length matter for nutrient responsiveness?

For over 2500 years, considerable agronomic interest has been paid to soil fertility. Both crop domestication and the Green Revolution shifted photoperiodism and the circadian clock in cultivated species, although this contributed to an increase in the demand for chemical fertilisers. Thus, the uptake of nutrients depends on light signalling, whereas diel growth and circadian rhythms are affected by nutrient levels. Here, we argue that day length and circadian rhythms may be central regulators of the uptake and usage of nutrients, also modulating responses to toxic elements (e.g., aluminium and cadmium). Thus, we suggest that knowledge in this area might assist in developing next-generation crops with improved uptake and use efficiency of nutrients.

Floodplain lakes as an indicator of increasing industrial pollution – Case study from a fertilizer factory in Poland

Despite the development of organic farming, the demand for mineral fertilizers is still high. Processes of fertilizer production are water-consuming, which is why factories are often located near large rivers. Such facilities should be monitored in detail because they might pose a threat to water quality. The aim of this study was to analyse the impact of a nitrogen fertilizer factory chemical wastewater treatment plant (CWTP) on the water quality of nearby river-lake systems. Potential contamination could indicate installation defects. Six floodplain lakes were selected for analysis: three located within the embanked area and three outside the embanked area, all close to the CWTP. Two similar lakes 30 km upstream were chosen as controls. Water samples were taken monthly from March to November 2022. We analysed pH, electrical conductivity (EC), the content of Cl−, total nitrogen (TN), NH4+, NO3−, total phosphorus (TP), PO43−, dissolved organic carbon (DOC), Ca2+, K+, Mg2+ and Na+. Statistical analysis indicated that the canal that drains, among others, the cooling towers wastewater, might have an impact on the nearby lakes, significantly increasing their content of Cl− and Na+. On the other hand, the concentration of NH4+ was significantly higher in the lakes located downstream of the CWTP, although they did not have any surface connection with the CWTP reservoir. This fact and NH4+-polluted water seeping under the dike indicate that the CWTP reservoir might be leaking. Further research on underground water is required to establish whether the CWTP reservoir is properly secured. It is extremely important because the CWTP is located in the Vistula River valley, which supplies drinking water to almost 2 mln people. Any damage to the reservoir, e.g., during a flood, would lead to an ecological disaster involving not only the Vistula but also the Baltic Sea, affecting millions of people.

Fluorides immobilization through calcium aluminate cement-based backfill: Accessing the detailed leaching characterization under torrential rainfall

Urbanization and economic development have increased the demand for fertilizers to sustain food crop yields. Huge amounts of by-products, especially phosphogypsum (PG), are generated during the wet processing of rock phosphate to produce fertilizers. Chronic exposure to fluoride in phosphogypsum in groundwater as a result of the weathering of fluoride-containing waste poses a significant health risk to millions of people. We propose a method for using calcium aluminate cement (CAC) to remediate high fluoride contents in solid waste. Column leaching tests under harsh rainfall conditions confirmed the efficient fluoride immobilization capacity of a CAC binder. Although the fluoride concentrations in leachates during the first 1–2 days (1.25 mg/L) slightly exceeded the threshold of 1.00 mg/L, the concentrations over 3–28 days (ranging from 0.98 to 0.83 mg/L) consistently remained well within the acceptable range. Furthermore, our characterization and geochemical modeling revealed the fluoride retention mechanisms of CAC-stabilized PG under laboratory-simulated conditions of torrential rainfall. During leaching, physical encapsulation prevents fluoride from contacting leachate. However, an unfavorable pH value can cause the release of fluoride from the cement matrix, which is subsequently captured by aluminate hydrate through adsorption or co-precipitation. We quantified the carbon footprint of CAC for immobilizing 1 mg of fluoride in PG, obtaining a remarkably low value of 4.4 kg of CO2, in contrast to the emissions associated with the use of ordinary Portland cement (OPC). The findings suggest a unique opportunity for extensive PG remediation. This opportunity extends the horizons of achieving zero-waste emissions in the phosphorus industry and has practical significance in the context of reducing carbon emissions.

Comprehensive Evaluation and Development of Irish Compost and Digestate Standards for Heavy Metals, Stability and Phytotoxicity

Recent EU circular economy, bioeconomy policies and the New Green Deal promote the recycling of organic wastes into soil improvers and fertilisers, thereby reducing the use of mineral fertilisers. This has renewed interest in the use of compost and digestate as fertilisers. At the same time, the Russian invasion of Ukraine has strengthened the demand for sustainable domestic fertilisers to guarantee the security of supply. It is now more important than ever that quality standards in Ireland are fit for the purpose of aiding the sustainable local production of fertilisers. Quality standards for compost and digestate ensure and protect the environment. This study collated the results of the analysis of Irish compost and digestate samples and made comparisons of the Irish data to databases, reports and standards from other countries, including the EU Fertiliser Products Regulation 2019/1009. This paper, therefore, provides comprehensive information on heavy metal, stability and phytotoxicity standards from a number of European and other countries. In addition, it includes actual data on these parameters from Ireland and a few European countries. From this collation and comparison process, we propose to update the heavy metals and stability limits in the Irish compost standard (IS 441) and heavy metals and stability limits in a new digestate standard (whole, liquid and fibre). Our methodology and collated data can be used as templates for countries, especially in Europe, which have not developed their own standards. Having an updated compost quality standard supports the development of a circular economy while still respecting the precautionary principle of avoiding pollution when compost and digestate are used on the soil.

Potential Soil Remineralizers from Silicate Rock Powders (SRP) as Alternative Sources of Nutrients for Agricultural Production (Amazon Region)

The demand for mineral fertilizers has increased over the years. In the states of Amazonas and Roraima, acquiring conventional fertilizers used in agriculture is challenging due to the distance from large production centers. In these regions, alternative fertilizers are needed to maintain food security. However, research in agrominerals of silicate rock powders (SRP) is still incipient. The objective of this research was to characterize three important Units of Agrogeological Interest in the Manaus/Boa Vista axis in the Amazon region of Brazil: (i) EBAM Quarry: quartz monzonites from the Água Branca suite, partially potassified, (ii) Granada Mining Quarry: basalts from the Apoteri formation, and (iii) Samauma Quarry: riolites from the Iricoumé Group. Samplings were carried out followed by chemical analyses for determining macro and micronutrients, in addition to potentially toxic elements; petrographic analyses were performed for mineralogical characterization as well as granulometric analyses of the powders collected in the quarries. The results showed that the EBAM quarry rock powder meets the standards established by Brazilian legislation. It also has low levels of potentially toxic elements and only 15% quartz, indicating good safety in the use of this SRP, in addition to the large supply of the material already crushed, for which there is still no market. At the Granada Mineração quarry, SRP also has the necessary characteristics to classify as a soil remineralizer, including K2O content above 1%. At Pedreira Samauma, although SRP does not qualify as an agromineral, it has more than 5% K2O and 77% aphanitic matrix, which could result in a more accessible release of abundant K and Si to the soil–plant system. Using laser granulometry analysis, it was possible to make some considerations about the effects of the crushing process in such different lithotypes and, finally, to characterize and classify the prospects of greatest interest for “rochagem” in the Amazon.

Computational Fluid Dynamics of Ammonia Synthesis in Axial-Radial Bed Reactor

Ammonia synthesis by the Haber–Bosch method is a typical and effective implementation of the chemical process in the large-scale fertiliser industry. Due to the growing demand for fertilisers and food, it is desirable to study this process thoroughly using modern numerical methods to improve the operation of existing devices and facilitate the design of new devices in industrial installations. This manuscript focuses on the influence of the catalyst bed parameters on the ammonia synthesis process. Variants with different sizes of catalyst particles and modifications of the geometry of catalytic beds were considered. The axial-radial Topsoe converter with magnetite as a catalyst, commonly used in modern fertiliser industry beds, was investigated using Computational Fluid Dynamics. As a result, contours of velocity, pressure, concentration, and rate of ammonia formation were obtained. The analysis of the obtained results made it possible to determine the gradient of ammonia production rate in the catalyst bed and designate zones with negligible reaction rates. The authors also proposed possible bed geometry modifications to reduce bed volumes without affecting the converter’s performance.

An Assessment of Options to Improve the Removal of Excess Nutrients from European Wastewater

In this contribution we quantify the potential to reduce the discharge of excess nutrients with European wastewater, by modelling pollution, greenhouse gas emissions and the costs of measures under various scenarios. We analyse two types of strategies, namely extending the requirement of nutrient removal to broader areas and increasing the removal efficiency of nitrogen and phosphorus. As the former strategy usually entails some infrastructural investment while the latter entails an optimization of the existing processes, the two imply different costs, and increasing efficiency usually shows a better cost–benefit ratio. In any case, actions increasing nutrient removal are expected to pay for themselves in terms of the benefits they bring in abating water pollution and (for nitrogen) greenhouse gas emissions. Nitrogen removal becomes even more attractive whenever the infrastructural investments that we assume may be avoided, thanks to the possibility of an optimized use of the existing infrastructure. Phosphorus removal may become even more attractive with the progress of technologies for its recovery from wastewater and sludge, and with the increase of its demand for fertilizers and other industrial uses.

Impact of chemical fertilizer on soil fertility of oil palm plantations in relation to productivity and environment

Indonesia produces around 45 MT of CPO in 2020. It is predicted that the demand of world palm oil will remain. Most of the oil palm plantations are grown on acidic soils with low fertility levels, such as Peat soils, Podzolic soils, and Acid sulfate soils. The domestic demand of phosphate and Kalium fertilizer still fulfilled by importation. Production of oil palm had depend on this fertilizer. Various research results have found that fertilizing oil palm using chemical anorganic fertilizers, especially Urea, TSP, KCl and Kieserit, has produced fresh fruit bunches which are quite high and profitable. Fertilizing oil palm crops requires a very large cost of around 30% of production costs. Currently, non-subsidized chemical fertilizers are rocketing, which is very burdensome for oil palm farmers. Some research results indicate that the continuous use of chemical fertilizers in oil palm plants causes to the land degradation. The use of organic fertilizers can improve sour and less fertile land, can increase the weight and number of oil palm fruit bunches. This paper aims to examine the impact of the use of chemical fertilizers on oil palm fruit production, as well as provide alternative organic fertilizers which sources are mostly around plantations.

Nitrogen fertilization promoted microbial growth and N2O emissions by increasing the abundance of nirS and nosZ denitrifiers in semiarid maize field.

Nitrous oxide (N2O) emissions are a major source of gaseous nitrogen loss, causing environmental pollution. The low organic content in the Loess Plateau region, coupled with the high fertilizer demand of maize, further exacerbates these N losses. N fertilizers play a primary role in N2O emissions by influencing soil denitrifying bacteria, however, the underlying microbial mechanisms that contribute to N2O emissions have not been fully explored. Therefore, the research aimed to gain insights into the intricate relationships between N fertilization, soil denitrification, N2O emissions, potential denitrification activity (PDA), and maize nitrogen use efficiency (NUE) in semi-arid regions. Four nitrogen (N) fertilizer rates, namely N0, N1, N2, and N3 (representing 0, 100, 200, and 300 kg ha-1 yr.-1, respectively) were applied to maize field. The cumulative N2O emissions were 32 and 33% higher under N2 and 37 and 39% higher under N3 in the 2020 and 2021, respectively, than the N0 treatment. N fertilization rates impacted the abundance, composition, and network of soil denitrifying communities (nirS and nosZ) in the bulk and rhizosphere soil. Additionally, within the nirS community, the genera Cupriavidus and Rhodanobacter were associated with N2O emissions. Conversely, in the nosZ denitrifier, the genera Azospirillum, Mesorhizobium, and Microvirga in the bulk and rhizosphere soil reduced N2O emissions. Further analysis using both random forest and structural equation model (SEM) revealed that specific soil properties (pH, NO3--N, SOC, SWC, and DON), and the presence of nirS-harboring denitrification, were positively associated with PDA activities, respectively, and exhibited a significant association to N2O emissions and PDA activities but expressed a negative effect on maize NUE. However, nosZ-harboring denitrification showed an opposite trend, suggesting different effects on these variables. Our findings suggest that N fertilization promoted microbial growth and N2O emissions by increasing the abundance of nirS and nosZ denitrifiers and altering the composition of their communities. This study provides new insights into the relationships among soil microbiome, maize productivity, NUE, and soil N2O emissions in semi-arid regions.

(Invited) Next Generation Electrified Membrane Technology for Simultaneous Wastewater Treatment and Production of Nitrogen Fertilizer

Recovery and repurposing of wastewater nitrogen such as nitrate (NO3 −) and nitrite (NO2 −) receive increasing attention as the current approaches of biological nitrogen removal or conversion into nitrogen gas (N2) renders high energy footprints. This study reported the first electrified membrane upcycling of NO3 − into NH3 that further converted into ammonia sulfate (NH4SO4), a liquid fertilizer readily for use. Paired electrolysis was used to couple simultaneous cathodic and anodic electrochemical half-reactions to enable nitrate reduction and eliminate the external acid/base consumption. Under a partial current density of 63.8±4.4 mA·cm−2 on a cathodic membrane made of a mixed-valence copper oxide and a polytetrafluoroethylene (PTFE) hydrophobic substrate, a recovery rate and energy consumption of 3100±91 g-(NH4)2SO4·m−2·d−1 and 21.8±3.8 kWh·kg−1-(NH4)2SO4 were achieved with the synthetic feed solution (150 mM NO3 −) flowing into the cathode chamber and the produced NH3 migrating across the cathodic membrane into a trap and anode chambers filled with the flowing 0.5 M Na2SO4 solution. 99.9% NO3 − was removed in the feed after 5 h operation with a NH3 recovery rate of 99.5%. This electrified membrane process was demonstrated to achieve comparable performances of synergistic nitrate decontamination and nutrient recovery using real nitrate wastewater with durable catalytic activity and stability. Specifically, the required electricity cost for converting 10 to 100 mM NO3 − to (NH4)2SO4 was $675 to $408 ton−1, respectively. The obtained (NH4)2SO4 may be sold as fertilizer at a price of 533 $·ton−1 (according to USDA) and further offset the cost of the NO3 − removal.According to the International Fertilizer Association, in 2018 the U.S. ranked second in nitrogen production, representing 11.6% of global production. However, it still requires the importation of nitrogen fertilizer, to fully meet the national demand. The US Environmental Protection Agency reports that in 2013, ~38 kg of nitrogen per acre per year was used for fertilization, and in 2016, 94 million acres of corn were planted in the US, representing ~40% of US fertilizer demand. Roughly, this equates to ~8.9 billion kg of nitrogen per year needed to meet total US fertilization demand. The nitrogen available in drinking water sources is roughly 65 million kg per year, and the nitrogen available in wastewater sources is roughly 2.4 billion kg per year. Thus, by fully recovering the nitrogen from wastewater 34.3% of the US nitrogen fertilizer requirement could be met. This could also further mitigate the increase in nitrogen fertilizer prices due to blocked nitrogen fertilizer imports and even free the US from nitrogen fertilizer imports. According to U.S. Department of Agriculture, the average U.S. farm price of sulfate of ammonium fertilizers is $533 per ton. Even leaving aside the revenue generated by the treatment of nitrogen-containing sewage, the market size of nitrogen fertilizer produced through sewage is as high as $12.8 billion.

Ammonia as an SOFC Fuel

The conventional production route of ammonia relies on natural gas as a source of hydrogen and is thus very CO2 intensive; almost 2% of global anthropogenic CO2 emissions stems from ammonia synthesis. This will have to change over the next two to three decades, where a “green route” to ammonia must be deployed to ensure required emission reductions.The annual production of ammonia is currently around 180 million tons of which ~80% is used for fertilizer production. This will likely increase due to increased fertilizer demand, but also because ammonia is a promising energy vector and a potential green fuel for the shipping sector. The expected energy demand for global shipping by 2050 is in the order of ~15 EJ [1]. It will be difficult to cover such a large demand by bio-mass derived fuels (e.g. methanol) considering global limitations in sustainable biomass resources and the needs of other sectors like aviation, heavy transport and chemical industry [1]. Hence, for the green transition efficient and sustainable routes to green ammonia are important, as will be efficient technologies to convert ammonia to electricity.Ammonia is an excellent fuel for SOFCs as previously reported in several studies [2], [3]. We have in the framework of the project “SOC4NH3” [3] investigated the impacts of firing an SOEC with ammonia in terms of its impact on overall losses, the cell degradation mechanisms as well as potential benefits.SOEC durability, when operating on ammonia, was followed over extended test periods between 2000 and 6000 hours at single cell level at different temperatures and current densities. The cells were Ni/YSZ-supported thin electrolyte cells of a 5*5 cm2 foot-print. The degradation rates observed when feeding with ammonia were very similar to degradation rates observed for the same cells when operated in a 1:3 gas mixture of N2/H2.Also the detailed electrochemical performance was explored at different temperatures using impedance spectroscopy. An example of impedance spectra obtained when feeding ammonia to the cell or a N2/H2 gas mixture at ca. 850 oC and 675 oC is presented in Figure 1. When feeding ammonia a cooling is observed due to the endothermic nature of the cracking reaction. This leads to a slight increase in both series resistance and polarization resistance. Therefore, the impedance responses in the ammonia experiments is in the Figure compared to responses obtained in N2/H2 at a slightly lower furnace set-point temperature (5-10 oC lower). Evidently, at around 850 oC, the only effect on the impedance response of feeding ammonia directly is the slight reduction in temperature; the N2/H2 and NH3 responses are practically identical when comparing characteristics at furnace set-point temperatures of 845 oC and 850 oC for N2/H2 and NH3, respectively. In contrast, if the same experiment is conducted at around 675 oC a difference between the response in ammonia and the response in N2/H2 is observed. The difference in behavior cannot be compensated by just lowering the furnace temperature a bit to simulate the impact of a cooling. The impedance at high frequency in ammonia is clearly much larger than for the N2/H2 feed. Note here, that the Rs in the two different feeds is practically identical. Hence, we have to conclude that there is a direct negative effect of the presence of ammonia at the electrode on the hydrogen oxidation kinetics. The effect is stronger than what can be ascribed to cooling and dilution of the H2. The details will be discussed in the paper.SOFC operation on ammonia and its impact at stack level was also explored. Potential advantages of ensuring that a part of the ammonia cracks inside the stack, as opposed to up-stream the stack, was addressed by modelling. Finally, a TSP1 SOFC stack from Topsoe A/S was operated with some internal ammonia cracking. The results will be presented and discussed to elucidate benefits and limitations in operating SOFC stacks with internal cracking of ammonia. Acknowledgment The work was supported by the EUDP-project SOC4NH3; Grant Agreement 64018-0546. References MarEfuel Project report; “Electro-fuels for long range maritime transport”, 2021. https://orbit.dtu.dk/en/projects/electro-fuels-for-long-range-maritime-transport, available from Orbit DTU. J.B. Hansen, J. Madsen, J.U. Nielsen, N. Christiansen, Proceedings European SOFC Fuel Cell Forum, Luzern, Switzerland (2010), and A. Hagen. Risø International Energy Conference 2007, Risø-R-1608(EN) 3. John Bøgild Hansen and Peter Vang Hendriksen 2019 ECS Trans. 91 2455. Figure 1