The Use of New Parameters to Optimize the Composting Process of Different Organic Wastes

Daniela Pezzolla,Mirko Cucina,Giovanni Gigliotti,Primo Proietti,Roberto Calisti,Luca Regni

doi:10.3390/agronomy11102090

Daniela Pezzolla, Mirko Cucina + Show 4 more

Open Access

https://doi.org/10.3390/agronomy11102090

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Abstract

The correct development of the composting process is essential to obtain a product of high value from organic wastes. Nowadays, some composting mixture parameters (i.e., air-filled porosity, moisture and the C/N ratio) are used to optimize the composting process, but their suitability is still debated because the literature reports contrasting results. This paper aimed to find other parameters that control the correct development of composting. The relationship between these and the compost quality was then verified. Twelve different composting mixtures were prepared using different organic wastes and bulking agents and were aerobically treated in a 300 L composter. The physico-chemical and chemical parameters of initial mixtures were analyzed, with particular regard to the total and water-extractable forms of organic C and N and their ratios and correlated with the temperature measured during composting. A positive correlation between temperature parameters during the active phase and soluble forms of N in the initial mixtures was found. A high total organic C to soluble N ratio in the composting mixtures was correlated with the low quality of the compost produced. Based on the results, a minimum content of WEN (water-extractable N) (0.4% w/w) or a TOC/WEN (total organic C/WEN) ratio in the range of 40–80 was recommended to ensure the correct development of the process and to produce compost of high quality.

Highlights

Municipal, agro-industrial and livestock activities generate large volumes of organic wastes, whose management can produce adverse effects on the environment
In a study carried out by Barrena et al [12], it was observed that the raw pruning wastes are characterized by a high C/N ratio (42 and 52), and the semi-composted pruning resulted in a similar C/N ratio
Physico-chemical and chemical (i.e., Total organic carbon (TOC)/total Kjeldahl-N (TKN)) parameters were commonly used to optimize composting mixtures, they did not ensure the correct development of the aerobic process

Summary

Introduction

Agro-industrial and livestock activities generate large volumes of organic wastes, whose management can produce adverse effects on the environment (soil, water and atmosphere pollution). Composting represents a suitable and environmentally friendly disposal strategy for organic waste management. Composting aerobically degrades organic wastes to compost and two main by-products, heat and carbon dioxide [1,2]. Composting is a self-heating process that proceeds through three main steps: (1) The mesophilic phase (25–40 ◦C), (2) the thermophilic phase (55–65 ◦C) and (3) the curing phase. Labile organic matter is mineralized and complex recalcitrant materials tend to concentrate, increasing the organic matter stabilization in the compost [3]. Compost is a nutrient-rich organic amendment able to provide N, P, K and organic matter to the soil, contributing to soil C sequestration [2,4]

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