From manure to high-value fertilizer: The employment of microalgae as a nutrient carrier for sustainable agriculture

Abstract

The use of livestock and poultry manures as fertilizers is regarded as an important action in the development of circular agriculture. However, long-term fertilization with manure is accompanied with heavy metals accumulation, pathogens contamination, and ammonia toxicity, which may cause the decline of soil quality and crop productivity. To address the aforementioned problems, in this work, we proposed a “manure-algae-crop” technical route, in which microalgae are employed as a carrier transporting nutrients in manures to soil and crops. This paper presented the advanced techniques which can tackle with the hazardous factors in manures and promote the nutrients assimilation by microalgae. Additionally, the utilization of microalgae in the forms of living cyanobacteria , liquid fertilizer , and slow-release fertilizer was discussed in detail. Particularly, we also focused on the disadvantages of algae fertilizers in different forms. By the end of this work, based on the analysis of current challenges and problems, we discussed the potential solutions and prospects of “manure-algae-crop” technical route. In fact, previous studies have achieved many progresses in algae-based manure remediation and utilization of algae fertilizers. Hence, based on current knowledge, “manure-algae-crop” technical route has greater advantages over traditional models of manures utilization in agriculture. In the foreseeable future, with the development of new technologies, reduction of operational cost, and upgrading of agricultural model, “manure-algae-crop” technical route will be applied more frequently in agriculture. It is expected that this technical route can truly promote the high-value utilization of manures and the development of eco-friendly agriculture. • Manure contains hazardous factors threatening soil quality and crop cultivation. • The “manure-algae-crop” technical route is proposed to utilize manure resource. • Algae serve as a carrier transporting nutrients in manure to soil and crop. • Algae in different forms can be employed for soil quality improvement. • Some challenges must be addressed for the practical application of algae fertilizer.