Hydroponic technique using waste concrete and ferronickel slag instead of fertilizer.

This paper presents whether some minerals in waste concrete and ferronickel slag are available for hydroponics instead of commercial fertilizer. Waste concrete and ferronickel slag contain rich calcium, silica, and magnesium, which are well-known nutrients for plants. In this study, small-scaled hydroponic plant growth tests targeting romaine lettuce and spinach were conducted to verify this idea. The experimental conditions were designed to satisfy that the total amounts of minerals released from the wastes were more than the required amounts for growth of the vegetable plants. The released amounts of minerals were evaluated from the serial batch leaching test using the wastes, then the required amounts for growth were estimated by measuring mineral contents of plants sold in supermarkets. According to the experimental results, the calcium in waste concrete was effective for growth of the romaine lettuces. The magnesium in ferronickel slag improved not only the growth of the spinaches due to photosynthesis but also the uptake amount of the phosphorous, resulting in the reduction of operating costs, such as lighting electric power and nutritional resources for plant factories. Finally, the romaine lettuces and spinaches obtained from the experiments had little contents of toxic heavy metals. [ABSTRACT FROM AUTHOR]