The presence of impurities in selectively collected biowaste is one important factor affecting the quality of compost. Other factors include the type of treatment process, and the characteristics of the composting plants.
The analysis was based on a large database from the Catalan Waste Agency (ARC), which characterizes the selectively collected biowaste treated and the compost produced in 21 composting and anaerobic digestion plants from Catalonia between 2010 and 2014. Accordingly, a statistical analysis was carried out with the main objective of quantifying the effect of impurities, as well as other variables, in several parameters of compost quality. The latter included the presence of heavy metals, electrical conductivity, and compost maturity level. The study included the development of univariate and bivariate analysis and multiple regression models.
Based on the estimated regression models, several scenarios were developed with the main purpose of assessing the effect of potential variations of impurity levels on the selected parameters of compost quality.
One of the most significant results was the verification that the higher presence of impurities in selectively collected biowaste affects negatively all the parameters of compost quality assessed. This result is very relevant as it highlights the multiple effects of impurities in the quality of final product. This finding helps motivating the necessary reduction of impurities found in the biowaste fraction.