Innovative electrode technique extracts fertilizer from manure

A group of curious cows in summer evening light. A typical Dutch rural scene.

Scientists at the University of Wisconsin–Madison have developed an innovative technique aimed at helping farmers reclaim valuable nutrients such as ammonia and potassium from livestock manure. This approach is expected to facilitate the efficient production of fertilizers and other chemicals, potentially revolutionizing agricultural practices.

The interdisciplinary team’s research, still in its experimental stages, presents a promising solution to curb water and air pollution. Preliminary findings suggest that this method could mitigate the environmental impact of manure, notorious for its ammonia content and contribution to greenhouse gases.

Ammonia, a key ingredient in nitrogen fertilizers, is currently produced via the energy-intensive Haber-Bosch process, which significantly contributes to global greenhouse gas emissions. Given these environmental concerns, along with the logistical and cost challenges of using manure as a direct fertilizer, the search for efficient ammonia recovery methods has intensified.

This new electrochemical technique, detailed in a recent Nature Sustainability journal article, introduces a nickel-based electrode resembling those used in batteries. This electrode, when immersed in manure wastewater, selectively attracts ammonium and potassium ions. This process not only extracts nutrients but also produces additional chemicals like hydrogen fuel or hydrogen peroxide.

Song Jin, a chemistry professor at UW–Madison, alongside doctoral candidate Rui Wang and Professor Mohan Qin, spearheads this research. According to Jin, the simplicity of the process is a key advantage, where “the battery material goes in, and ammonia gets sucked out.”

Early experiments have shown promising results, with over half of the ammonia in manure recovered in a single attempt and approximately 85% after two cycles. Furthermore, an environmental study by Professor Rebecca Larson of the Nelson Institute for Environmental Studies suggests significant reductions in ammonia emissions and nitrate contamination in water bodies from a 1,000-head dairy farm using this system.

Economic assessments, led by MIT’s Professor Fikile Brushett, indicate that the operational revenues for a model dairy farm employing this system could surpass its costs, contingent on reasonable electricity pricing.

The team’s next steps focus on refining the materials and processes, scaling up the system, and evaluating its effectiveness in larger, real-world farm settings. The initial analysis points to a promising future, with Jin and Qin optimistic about the system’s potential benefits at a larger scale.

Source: Nature Sustainability

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