Electrification of fertilizer production via plasma-based nitrogen fixation: a tutorial on fundamentals

Abstract

Nitrogen-containing fertilizers are key chemicals for our population, ensuring the constantly growing demands in food production. Fertilizers promote vegetative growth, specifically through the formation of amino acids, the building blocks of proteins. However, the current synthesis method relies on the Haber–Bosch process for ammonia synthesis, one of the largest-volume chemicals made globally, having a significant environmental impact. The need for a sustainable and green industry with low CO₂ emission triggers the demand to reconsider the current fertilizer production approach. In this context, electrified, local, small-scale production emerges as a promising option to address current environmental and economic challenges. This approach allows production to be consumer-oriented while adhering to environmental regulations. In light of this, non-equilibrium plasma technology has gained a wave of attention. Plasma-based nitrogen fixation has a long history, starting more than a century ago. It was one of the first nitrogen fixation methods invented and later replaced by more energy-efficient technologies. In the current paradigm, this approach can fulfill all industrial and social demands: it perfectly aligns with non-stable renewable energy, is carbon-neutral, relatively simple to maintain, and can provide a valuable source of fixed nitrogen on a small-scale, on-farm production with complete control over land processing. The plethora of existing publications on plasma-based nitrogen fixation addresses the concept of synthesizing nitrogen-containing fertilizers. However, despite significant advancements in the field and the availability of numerous reviews, they tend to focus on specific aspects, such as plasma physics (e.g., the role of vibration excitation), plasma-initiated chemistry (e.g., nitrogen oxidation or reduction), or reactor design. This tutorial review aims to bridge these gaps by presenting an integrated and accessible explanation of the interconnections between different aspects affecting plasma-based nitrogen fixation. It is designed both for newcomers to the field and those who want to broaden their knowledge, highlighting the current state-of-the-art and offering insights into future research directions and implementations.