Effects of multi-component passivator on heavy metal passivation, compost quality and plant growth

Direct land application of conventional compost may cause ecological risks due to the presence of heavy metals. To effectively reduce heavy metal bioavailability in compost, a multi-component passivator comprising Candida utilis, sodium humate, zeolite and attapulgite was developed, which showed passivation rates of 59.28%, 86.93% and 38.95% for zinc (Zn), copper (Cu), and ferrum (Fe), respectively, in compost. The addition of customized multi-component passivator in compost not only reduced the mobility of heavy metals, but also improved the quality of the compost and further increased the abundance of lignocellulose-degrading beneficial microorganisms in compost. Subsequent fertilization results showed that the compost product fermented with customized multi-component passivator greatly improved the growth of Chinese cabbage, with significant increases in height, weight, root length, and total chlorophyll contents of 97.63%, 210.13%, 20.42%, and 40.38%, respectively. It can be concluded that the custom-made multi-component passivator is expected to be a good additive for heavy metal passivation, high-quality compost, and plant growth.