Miller Victor V, Clark Douglas S, Mesbah Ali
Department of Chemical and Biomolecular Engineering, University of California, Berkeley, California 94720, United States.
ACS Sustain Chem Eng. 2024 Feb 5;12(7):2621-2631. doi: 10.1021/acssuschemeng.3c06423. eCollection 2024 Feb 19.
Sustainable fertilizer production is a pressing challenge due to a growing human population. The manufacture of synthetic nitrogen fertilizer involves intensive emissions of greenhouse gases. The synthetic nitrogen that ends up in biowaste such as animal waste perturbs the nitrogen cycle through significant nitrogen losses in the form of ammonia volatilization, a major human health and environmental hazard. Low-temperature air-plasma treatment of animal waste holds promise for sustainable fertilizer production on farmlands by enabling nitrogen fixation via ionization, forming nitrogen oxyacids. Although the formation of nitrogen oxyacids in plasma treatment of water is well-established, the extent of nitrogen oxyanion enrichment in animal waste and its downstream effects on acidifying the waste remain elusive because many compounds found in complex biowaste media may interfere with absorbed NO species. This work aims to establish that plasma treatment of dairy manure can suppress ammonia loss by volatilization via acidification of animal waste while enriching the waste in total nitrogen due to nitrogen retained in ammonia as well as adding nitrogen oxyacids by reacting NO with the aqueous slurry. To this end, air-plasma effluent containing NO is bubbled through dairy manure, which is then analyzed for changes in the nitrogen oxyanion content and pH. Increasing the plasma treatment time results in more acidic manure, reduced ammonium content in the downstream acid trap, and increased nitrogen oxyanion content, where the yield of nitrogen oxyanion from absorbed NO species is approximately 100%. Increased plasma treatment also led to an increase in the total Kjeldahl nitrogen and the total nitrogen. These results indicate that plasma treatment of animal waste can significantly suppress ammonia pollution from animal husbandry facilities such as dairy farms while upcycling animal waste as a rich organic source of nitrogen.
由于人口不断增长，可持续肥料生产成为一项紧迫的挑战。合成氮肥的生产涉及大量温室气体排放。最终进入动物粪便等生物废弃物中的合成氮，会以氨挥发的形式造成大量氮损失，从而扰乱氮循环，氨挥发是一种主要的人类健康和环境危害。对动物粪便进行低温空气等离子体处理，有望通过电离实现固氮，形成氮含氧酸，从而在农田实现可持续肥料生产。虽然在水的等离子体处理中氮含氧酸的形成已得到充分证实，但在动物粪便中氮含氧阴离子的富集程度及其对粪便酸化的下游影响仍不明确，因为在复杂的生物废弃物介质中发现的许多化合物可能会干扰吸收的NO物种。这项工作旨在证明，通过酸化动物粪便，等离子体处理奶牛粪便可以抑制氨挥发损失，同时由于氨中保留的氮使粪便中的总氮增加，并通过使NO与含水浆液反应添加氮含氧酸。为此，将含有NO的空气等离子体流出物鼓泡通过奶牛粪便，然后分析粪便中氮含氧阴离子含量和pH值的变化。增加等离子体处理时间会使粪便酸性增强，下游酸阱中的铵含量降低，氮含氧阴离子含量增加，其中吸收的NO物种产生氮含氧阴离子的产率约为100%。增加等离子体处理还导致凯氏定氮法测定的总氮和总氮含量增加。这些结果表明，等离子体处理动物粪便可以显著抑制奶牛场等畜牧设施的氨污染，同时将动物粪便升级为富含氮的有机源。
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