Search Results (73)

Conventional ammonia production uses fossil-based hydrogen, resulting in high greenhouse gas emissions. Given the growing demand for sustainable solutions, it is essential to replace fossil hydrogen with renewable alternatives. This study assessed the technical, economic, and environmental viability of renewable ammonia production in Minas Gerais. To this end, an optimization model based on mixed integer linear programming (MILP) was developed and implemented in LINGO 20^® software. The model incorporated investment costs; raw materials; transportation; emissions; and indicators such as NPV, payback, and minimum sale price. Hydrogen production routes integrated into the Haber–Bosch process were analyzed: biomass gasification (GS_WGS), anaerobic digestion of vinasse (Vinasse_BD_SMR), ethanol reforming (Ethanol_ESR), and electrolysis (PEM_electrolysis). Vinasse_BD_SMR showed the lowest costs and the greatest economic viability, with a payback of just 2 years, due to the use of vinasse waste as a raw material. In contrast, the electrolysis-based route had the longest payback time (8 years), mainly due to the high cost of the electrolyzers. The substitution of conventional hydrogen made it possible to avoid 580,000 t CO₂ eq/year for a plant capacity of 200,000 t NH₃/year, which represents 13% of the Brazilian emissions from the nitrogenated fertilizer sector. It can be concluded that the viability of renewable ammonia depends on the choice of hydrogen source and logistical optimization and is essential for reducing emissions at large scale. Full article

The degradation of electrochemical materials during energy conversion and storage, in particular the electrocatalyst materials, is becoming increasingly important. The selection and design of sustainable materials is an important task. This work examines the synthesis, characterization, and application of an electrocatalyst (based on an amorphous alloy Co75Si15Fe5Cr4.5) having a structured surface in the form of nanocells for a “green” nitrate reduction reaction (NO₃RR), which can serve as an alternative to the well-known Haber-Bosch process for the synthesis of ammonia. The material for the electrocatalyst was obtained by anodizing the alloy in the ionic liquid BmimNTf₂ and characterized by using a combination of modern physicochemical and electrochemical methods. The Faradaic efficiency (FE) for the nanocell catalyst exceeds by more than three-fold and seven-fold catalyst with a polished surface and the initial catalyst having a natural oxide on the surface, respectively. A mechanism of this reaction on the studied electrocatalysts with structured and non-structured surfaces is proposed. It is mentioned that the nanocell electrocatalyst is an extremely stable material that passes all tests without visible changes. The authors consider their work as a starting point for the application of a nanostructured Co-electrocatalyst in NO₃RR. Full article

The N₂ reduction reaction (NRR) under ambient conditions is highly desirable because of its potential to replace the energy-consuming Haber-Bosch process for ammonia production. In recent years, much attention has been devoted to transition metal-based catalysts. However, the development of metal-free electrocatalysts remains a great challenge. Here, the electrocatalytic performance of bilayer borophene is systematically studied based on first-principles calculations. It was found that bilayer borophene has high activity with an overpotential of 0.21 V via the enzymatic mechanism. Bond elongations of nitrogen bond are observed in end-on and side-on patterns, where the bond lengths are stretched to 1.13 and 1.21 Å, respectively. Around 0.36 e⁻ is transferred to the adsorbed N₂ with the contribution of bottom boron atoms. Our results propose bilayer borophene as a novel metal-free catalyst for nitrogen reduction, thus providing an avenue to explore highly efficient electrocatalysts for ammonia production under ambient conditions. Full article

Ammonia production is a cornerstone of the modern chemical industry, essential for fertilizer manufacturing and increasingly relevant in the energy sector. However, the conventional Haber–Bosch (HB) process is highly energy- and carbon-intensive, contributing significantly to global greenhouse gas emissions, releasing approximately 1.6 tonnes of carbon dioxide for every tonne of ammonia produced. In the context of the ongoing climate crisis, exploring sustainable alternatives that can reduce or even eradicate these emissions is imperative. This review examines the potential of ammonia as a future energy carrier and evaluates the transition to green hydrogen-based HB production. Key technologies for green hydrogen generation are reviewed in conjunction with environmental, energy, and economic considerations. The transition to a green hydrogen-based HB process has been demonstrated to offer significant environmental advantages, potentially reducing carbon emissions by up to eight times compared to the conventional method. Furthermore, the economic viability of this process is particularly pronounced under conditions of low-cost renewable electricity, whether utilizing solid oxide electrolysis cells or proton-exchange membrane electrolyzers. Additionally, two emerging zero-emission, electrochemical routes for ammonia synthesis are analyzed in terms of their methodologies, efficiencies, and economic viability. Promising progress has been made in both direct and indirect nitrogen reduction approaches to ammonia. The indirect lithium-mediated pathway demonstrates the greatest potential, significantly reducing ammonia production costs. Despite existing challenges, particularly related to efficiency, these emerging technologies offer decentralized, electrified pathways for sustainable ammonia production in the future. This study highlights the near-term feasibility of decarbonizing ammonia production through green hydrogen in the HB process, while outlining the long-term potential of electrochemical nitrogen reduction as a sustainable alternative once the technology matures. Full article

Global agriculture remains dependent on nitrogen fertilizers produced through fossil fuel-based processes, contributing to greenhouse gas emissions, energy use, and supply chain vulnerabilities. This review introduces plasma-activated water (PAW) as a novel, electricity-driven alternative for sustainable nitrogen delivery. Generated by non-thermal plasma, PAW infuses water with reactive oxygen and nitrogen species, offering a clean, decentralized substitute for conventional synthetic fertilizers derived from the Haber–Bosch and Ostwald processes. It can be produced on-site using renewable energy, reducing transportation costs and depending on fertilizers. Beyond its fertilizer properties, PAW enhances seed germination, plant growth, stress tolerance, and pest resistance, making it a multifunctional input for controlled environment agriculture. We also assess PAW’s techno-economic viability, including energy requirements, production costs, and potential scalability through renewable energy. These factors are crucial for determining its feasibility in both industrial systems and localized agricultural applications. Finally, the review examines PAW’s contribution to the ten United Nations Sustainable Development Goals, particularly in climate action, clean energy, and sustainable food production. By combining agronomic performance with circular production and emissions reduction, PAW presents a promising path toward more resilient, low-impact, and self-sufficient agricultural systems. Full article

Electrochemical nitrogen reduction reaction (NRR) has emerged as a promising approach for sustainable ammonia synthesis under ambient conditions, offering a low-energy alternative to the traditional Haber–Bosch process. However, the development of efficient and sustainable electrocatalysts for NRR remains a significant challenge. Noble metals, known for their exceptional chemical stability under electrocatalytic conditions, have garnered considerable attention in this field. In this study, we report the successful synthesis of nanoporous CuAuPtPd quasi-high-entropy alloy (quasi-HEA) prism arrays through “melt quenching” and “dealloying” techniques. The as-obtained alloy demonstrates remarkable performance as an NRR electrocatalyst, achieving an impressive ammonia synthesis rate of 17.5 μg h⁻¹ mg⁻¹ at a potential of −0.2 V vs. RHE, surpassing many previously reported NRR catalysts. This work not only highlights the potential of quasi-HEAs as advanced NRR electrocatalysts but also provides valuable insights into the design of nanoporous multicomponent materials for sustainable energy and catalytic applications. Full article

This study evaluates the economic feasibility of flexible, renewable ammonia production in Italy through a comprehensive sensitivity analysis of the levelized cost of ammonia (LCOA). Ammonia is produced through Haber–Bosch synthesis from green hydrogen and nitrogen coming from alkaline electrolysis and cryogenic air separation, respectively. The analysis examines the impact of key parameters such as renewable source peak power, Haber–Bosch reactor flexibility, energy mix, electrochemical and hydrogen storage, on the final production cost. The location considered for the PV and wind power output is Southern Italy. The results show that a wind-driven system with minimal battery storage and a flexibility factor (ratio between the minimum operating capacity and the nominal capacity of the plant) of 20% offers the most cost-effective solution, but production is scaled down to 64 tpd. With the 2030 cost structure, battery storage offers better integration with wind systems and flexible operation, even at low levels of turndown. For different combinations of process design choices and flexibility, the optimal LCOA for a green ammonia production is approximately 0.59 USD/kgNH₃ in 2050. This cost of production could be competitive with grey ammonia, provided that a carbon emission allowance of USD 0.12/kgCO₂ is applied. Full article

The electrochemical nitrogen reduction reaction (eNRR) for electrochemical ammonia (NH₃) synthesis is considered a promising alternative to the energy-intensive and highly CO₂-emitting Haber-Bosch process. In numerous experiments, the Nafion membrane has been used as an electrolyte or separator. However, Nafion adsorbs and desorbs NH₃, leading to erroneous measurements and making reproducibility extremely difficult. This study systematically investigates the interaction between NH₃ and Nafion, underscoring the strength of the interaction between ammonium-ions (NH₄⁺) and protons (H⁺). We found that minute quantities of synthesized NH₃ are prone to persist within the membrane, albeit without affecting the ion conductivity and resistivity of Nafion. Consequently, the removal of NH₃ from the membrane can occur under conditions where synthesis is not viable. The objective of this work is to heighten awareness regarding the interaction between NH₃ and Nafion and contribute to the attainment of reliable and reproducible outcomes in eNRRs. Full article

Ammonia synthesis remains a cornerstone of global chemical manufacturing, essential for fertilizer production, energy storage, and emerging carbon capture technologies. This overview examines recent developments in the understanding of elementary reaction mechanisms in heterogeneous catalysis, with emphasis on transition metal thermocatalysts operating under the Haber–Bosch process. Traditionally, the dissociative adsorption of nitrogen (N₂) has been considered the rate-determining step. However, recent studies challenge this view, revealing possible shifts in rate-determining steps and suggesting that alternative mechanistic pathways may be operative. The discussion critiques studies that adhere strictly to the classic dissociative mechanism—often inferred from the reaction order of N₂—while overlooking alternative pathways that could offer more efficient catalytic routes and deeper mechanistic insight into ammonia synthesis. These insights offer a pathway toward more rational catalyst design and improved process efficiency in ammonia synthesis. Full article

Green ammonia, as a zero-carbon energy carrier, has emerged as a core process for achieving energy transition and chemical industry decarbonization through renewable energy-powered electrolytic hydrogen production integrated with low-carbon Haber–Bosch ammonia synthesis. However, the strong coupling among multiple units in green ammonia production systems, combined with operational data characteristics of nonlinearity, uncertainty, noise interference, and multi-timescale dynamics, creates significant challenges in accurately predicting ammonia yields and key process indicators, ultimately hindering online process parameter optimization and restricting improvements in production efficiency with effective carbon emission control. To address this, this study proposes a dual-layer attention LSTM model. The architecture constructs two sequential attention mechanisms: the first layer being an input attention mechanism for screening critical process indicators, followed by the second layer as a temporal attention mechanism that dynamically captures time-varying feature weights, enabling the adaptive analysis of sub-window contribution discrepancies to output variables across multiple time steps. Furthermore, the model is implemented and validated on a simulation platform of a renewable energy-coupled green ammonia demonstration project, with comparative analyses conducted against conventional LSTM and other baseline models. Experimental results demonstrate that the proposed model effectively adapts to complex scenarios in green ammonia production, including fluctuating renewable energy inputs and time-varying reaction conditions, providing reliable support for yield prediction and energy efficiency optimization. The developed methodology not only provides a novel approach for intelligent modeling of green ammonia production systems but also establishes a technical foundation for digital twin-based real-time control and dynamic scheduling research. Full article

Offshore wind energy is increasingly considered a vital resource to contribute to the renewable energy future. This renewable energy can be converted to clean energy alternatives such as hydrogen and ammonia via power-to-x technologies, enabling storage, energy security, and decarbonization of hard-to-abate sectors. This study assesses the techno-economic feasibility of integrating offshore wind energy with hydrogen and ammonia production as sustainable energy carriers and their transportation via pipelines or shipping. The methodology incorporates Proton Exchange Membrane (PEM) electrolysis for hydrogen production, seawater desalination, and the Haber–Bosch process for ammonia production. Offshore transport scenarios are compared to evaluate their cost-effectiveness based on distance and electrolyzer capacity. Results show the levelized cost of hydrogen (LCOH₂) ranges from EUR 6.7 to 9.8/kg (EUR 0.20–0.29/kWh), and the levelized cost of ammonia (LCOA) ranges from EUR 1.9 to 2.8/kg (EUR 0.37–0.55/kWh). Transportation costs vary significantly with distance and electrolyzer capacity, with levelized cost of transport (LCOT) between EUR 0.2 and 15/kg for pipelines and EUR 0.3 and 10.2/kg for shipping. Also, for distances up to 500 km, pipeline transport is the most cost-effective option for both hydrogen and ammonia. Despite high production costs, economies of scale and technological improvements can make offshore hydrogen and ammonia a promising means for a sustainable energy future. Full article

Ammonia (NH₃) plays a vital role in both the agriculture and energy sectors, serving as a precursor for nitrogen fertilizers and as a promising carbon-free fuel and hydrogen carrier. However, the conventional Haber–Bosch process is highly energy-intensive, operating under elevated temperatures and pressures, and contributes significantly to global CO₂ emissions. In recent years, nonthermal plasma (NTP)-assisted ammonia synthesis has emerged as a promising alternative that enables ammonia production under mild conditions. With its ability to activate inert N₂ molecules through energetic electrons and reactive species, NTP offers a sustainable route with potential integration into renewable energy systems. This review systematically summarizes recent advances in NTP-assisted ammonia synthesis, covering reactor design, catalyst development, plasma–catalyst synergistic mechanisms, and representative reaction pathways. Particular attention is given to the influence of key plasma parameters, such as discharge power, pulse voltage, frequency, gas flow rate, and N₂/H₂ ratio, on reaction performance and energy efficiency. Additionally, comparative studies on plasma reactor configurations and materials are presented. The integration of NTP systems with green hydrogen sources and strategies to mitigate ammonia decomposition are also discussed. This review provides comprehensive insights and guidance for advancing efficient, low-carbon, and distributed ammonia production technologies. Full article

The contribution of agriculture to the emission of the main greenhouse gases, CO₂, N₂O, and CH₄, is estimated to be between 25 and more than 50% of the total emissions worldwide. These data indicate that in developed, industrialized countries, severe policies might be successful in strongly reducing greenhouse gas emissions by focusing on agriculture. However, despite its central importance, agriculture is not at the center of political debate or meaningful emission-reducing policies. In this scientific review, current knowledge of the factors affecting the emission of greenhouse gases, including carbon dioxide, nitrous oxide, and methane, from agriculture is critically discussed. The pathways through which the reduction in greenhouse gas emissions from agriculture can be achieved are evaluated. For this purpose, we list the main factors contributing to the emission of greenhouse gases from agriculture and evaluate the roles of agricultural intensification, industrialization, and organic farming in greenhouse gas emissions. If the present trajectory of agricultural development continues, industrialized, intensive conventional agriculture will become an increasing source of greenhouse gas emissions worldwide. Also, the increasing quantitative relevance of energy plants in agriculture will contribute to increasing greenhouse gas emissions. Organic agriculture may offer an alternative means to reduce greenhouse gas emissions by applying the following central boundary conditions: a. the omission of mineral nitrogen fertilizers produced by the Haber–Bosch process, b. the combination of crop and livestock production, and c. the application of nutrient recycling at a regional level. This kind of organic agriculture may combine relatively high and sustainable crop yields with low emissions of greenhouse gases. Industrialized agriculture, whether in its conventional or even its industrialized organic form, is an important source of greenhouse gases with increasing emissions worldwide. Under conditions of agricultural industrialization, industrialized organic agriculture will also contribute to increasing greenhouse gas emissions. At present, there are no political attempts in the countries of the industrialized Western hemisphere to address agriculture-related contributions to greenhouse gas emissions. Full article

A sustainable reaction of electrocatalytic nitrate conversion in ammonia production (NO₃RR) occurring under ambient conditions is currently of prime interest, as well as urgent research due to the real potential replacement of the environmentally unfavorable Haber–Bosch process. Herein, a series of electrocatalysts based on two-component cobalt alloys was synthesized using low-cost non-noble metals Co, Fe, Cr, and also Si. The samples of electrocatalysts were characterized and studied by the following methods: SEM, EDX, XRD (both transmission and reflection), UV–VIS spectroscopy, optical microscopy, linear (and cyclic) voltammetry, chronoamperometry, and electrochemical impedance spectroscopy. Beyond that, the determination of electrochemically active surface area was also carried out for all samples of electrocatalysts. Unexpectedly, the sample having an intermetallic compound (IMC) of the composition Co₂Si turned out to be the most highly effective. The highest Faradaic efficiency (FE) of 80.8% at E = −0.585 V (RHE) and an ammonia yield rate of 22.3 µmol h⁻¹ cm⁻² at E = −0.685 V (RHE) indicate the progressive role of IMC as the main active component of the electrocatalyst. Thus, this study demonstrates the promise and enormous potential of IMC as the main component of highly efficient electrocatalysts for NO₃RR. This work can serve primarily as a starting point for future studies of electrocatalytic conversion reactions in the production of ammonia using IMC catalysts containing non-noble metals. Full article

Ammonia, essential for fertilizers and energy storage, is mainly produced through the energy-demanding Haber–Bosch process. Microbial production offers a sustainable alternative, but natural yeast cells have not yet demonstrated success. This study aimed to enhance ammonia production in Saccharomyces cerevisiae by optimizing amino acid utilization through its deamination metabolism. Adaptive laboratory evolution is a method for rapidly generating desirable phenotypes through metabolic and transcriptional reorganization. We applied it to the efficiently fermenting S. cerevisiae strain CEN.PK113-7D using an unbalanced carbon/nitrogen medium to impose selective pressure. We selected several evolved strains with a 3–5-fold increase in amino acid utilization and ammonia secretion. The multi-step bioreactor strategy of the evolved strain AAV6, supplemented with concentrated nitrogen sources, resulted in the production of 1.36 g/L of ammonia, a value in line with levels produced by other microbial systems. This proof-of-concept study suggests that yeast-based processes can be adapted straightforwardly to ammonia production from high-protein waste derived from several sources. Full article