Ammonia synthesis is a topic of high interest in the industry as the market continues to expand and demand increases. The current ammonia production route is very energy and carbon-intensive, relying greatly on natural gas both as feedstock as well as for heat and power generation within the plant. In the present work, a cradle-to-gate environmental assessment of conventional and greener hydrogen production routes integrated with ammonia synthesis is carried out according to ReCIPe impact assessment method. Hydrogen production through conventional steam methane reforming coupled with gas-liquid carbon dioxide absorption by amines and chilled ammonia, electrolysis, and iron-based chemical looping are analysed and compared. Mass and energy balances from process flow modelling are used as inputs for the environmental evaluation using Life Cycle Assessment. The system boundaries considered in this work include: i) main processes: ammonia production, hydrogen production, carbon dioxide separation; ii) upstream processes: nitrogen, natural gas, ilmenite, Methyl-DiEthanol-Amine, chilled ammonia and catalysts supply chains, iii) downstream processes: carbon dioxide compression, transport and storage, degradation/disposal of solvents/oxygen carrier. The results show that natural gas-based ammonia synthesis integrated with chemical looping hydrogen production gives the highest reduction in Global Warming Potential while six out of the nine investigated impact indicators (excluding Global Warming Potential) suffer an increase between 30% and 60%. In the case of hydrogen produced from electrolysis, unless the electricity necessary for electrolysis is obtained from non-fossil sources, it results in the highest overall emissions to air, water and soil.

随着市场的不断扩大和需求的增加，氨合成是该行业的一个重要话题。当前的氨生产路线非常耗能和碳密集，极大地依赖天然气作为原料以及工厂内的热能和发电。在目前的工作中，根据ReCIPe影响评估方法，对常规和更绿色制氢路线与氨合成相结合进行了从摇篮到大门的环境评估。分析和比较了通过常规蒸汽甲烷重整制氢，以及胺和冷氨吸收气液二氧化碳，电解和铁基化学环化的过程。来自过程流建模的质量和能量平衡被用作使用生命周期评估的环境评估的输入。这项工作考虑的系统边界包括：i）主要过程：氨生产，氢生产，二氧化碳分离；ii）上游过程：氮气，天然气，钛铁矿，甲基二乙醇胺，冷冻氨水和催化剂供应链，iii）下游过程：二氧化碳压缩，运输和储存，溶剂/氧气载体的降解/处置。结果表明，基于天然气的氨合成与化学循环制氢相结合可最大程度降低全球变暖潜势，而研究的九个影响指标中有六个（不包括全球变暖潜势）增加了30％至60％。