Evaluation of the Effectiveness of near Infrared Reflectance Spectroscopy (NIRS) on Fe, Cu, Mn and Zn Estimation in Compost

摘要

Composting is a treatment whose use for organic waste management is increasing. This process always increases the concentration of non-labile elements and, especially, metals, due to the loss of mass, in terms of water and gaseous emissions. This could constitute a hazard in terms of compost quality and hence, agricultural and environmental issues must be implemented taking into account the increasing presence of metals. Fe, Cu, Mn and Zn are metals usually present in organic wastes in heterogeneous concentration depending on the source and nature of the waste. These metals could be considered simultaneously valuable elements, due to its condition of essential microelements for plants, and pollutants, depending on the dose. The analysis of these elements on each composting batch at commercial level is time-consuming and expensive. So, the estimation of metals in composting facilities based on the use of near infrared reflectance spectroscopy (NIRS) could be an interesting approach in order to monitor the compost quality. In this study, more than 250 samples from 15 different composting procedures using different organic wastes (GS: grape stalk; EGM: exhausted grape marc; GM: grape marc; CM: cow manure; PM: poultry manure; SS: sewage sludge; V: vinasse; CJW: citrus juice waste; Alpeorujo: olive oil waste; AS: almond skin; EP: exhausted peat; TSW: tomato soup waste; SMS: spent mushroom substrate) were used to calibrate and validate the estimation of Fe, Cu, Mn and Zn content in these composts. The results showed that this technique needs to be fitted to each element, using specific spectrum transformations, in order to achieve an acceptable accuracy in the prediction.