Composting with Industrial and Domiciliary Ashes in Temuco, Chile

Abstract

Chilean urban areas generate around 3.12 Mton year-1 of organic residues. Besides, power plants near to these urban areas produce mainly about 0.42 Mton year-1 associated to ashes. Both residues contribute to the introduction of pollutants in a liquid and solid phase into the natural environment. This study proposes the composting process of organic/inorganic domiciliary residues and industrial ashes which involves minimizing the volume of residues to be disposed, incorporating the circular economy concept. Composting is a biological decomposition process of organic waste by bacteria, fungi, worms and other organisms under controlled aerobic conditions and its use is considering a good strategy for his simplicity, low cost, and environment-friendly process. Their final product is considered a natural alternative to chemical fertilizers for use in agriculture, gardening and plant nurseries. In this context, the main goal of this research was to study the incorporation of industrial and domiciliary ashes to domiciliary organic residues. The experimental procedure consisted of bioreactors of 22.5 L with the addition of mass fractions of 0, 5 and 10% of ashes. During the experiment, pH, temperature, humidity, and weight were controlled. After composting, the physic-chemical parameters and maturity degree (NCh2880) of the final product were evaluated. The results showed that all reactors loss weight between 30.0% and 70.4%, which agrees with data reported in the scientific literature. The reactors reached a temperature higher than 55 C evidencing the thermophile phase. During composting, values of pH oscillated between 5 and 7. However, humidity values showed high variability, increasing with the higher dose of ashes assayed. Compost with the addition of domiciliary ashes could not meet physic-chemical parameters fixed in NCh2880. Only the treatment which a 5% of industrial ashes was added to the composting process evidenced acceptable physic-chemical parameters and maturity degree, corresponding to a class B compost.