PHOSPHORUS AND HEAVY METAL CONTENTS IN SMALL-SCALE COMPOSTING AREAS

Cleiton Junior Ribeiro Lazzari,Lucas Benedet,Paul Richard Momsen Miller,Gustavo Brunetto,Jucinei José Comin,Vilmar Müller Junior,Arcângelo Loss,Cledimar Rogério Lourenzi,Rafael Da Rosa Couto

doi:10.29121/granthaalayah.v8.i8.2020.730

Abstract

Composting is an important tool for recycling and proper disposal of organic waste. However, in small-scale composting, where total soil sealing and leachate collection is not carried out, elements such as P, Cu, Zn, Cd, Cr, Ni and Pb may accumulate in soil. This study aimed to assess phosphorus and heavy metal contents in soils of areas used for small-scale food waste composting. In order to do this, we sampled soil depths of 0-5, 5-10, 10-20, 20-30 and 30-40 cm of four areas with composting times of 16, 12, 7 and 1 year, in addition to four reference areas. All the study areas are located in the city of Florianópolis, Santa Catarina state, Brazil. We determined available P, Cu and Zn contents and total Cu, Zn, Cd, Cr, Ni and Pb contents in the soil samples. We found that the production of organic compost directly on the soil generally promoted increases in available P contents, which were above acceptable environmental limits, especially at the uppermost soil layers. Still, the presence of Cu, Zn, Cd, Cr, Ni and Pb was not an environmental liability in the composting areas, as the contents found were below those recommended by legislation.

Highlights

Waste production in urban areas has increased significantly in recent decades, with emphasis on food waste, either due to improper handling during processing or wastage in restaurants and households
We found that the production of organic compost directly on the soil generally promoted increases in available P contents, which were above acceptable environmental limits, especially at the uppermost soil layers
Contents found at this layer were 1200, 8900, 250 and 3400% higher in 1C, 2C, 3C and 4C compared to their reference areas, respectively. These results were expected as the literature supports that compost application to soil increases available P contents

Summary

Introduction

Waste production in urban areas has increased significantly in recent decades, with emphasis on food waste, either due to improper handling during processing or wastage in restaurants and households. A suitable alternative for these wastes is composting, which is a biological process of decomposition and stabilization of organic substrates under controlled thermophilic and aerobic conditions (Bernal, 2009; Cadis & Henkes, 2014). Composting promotes oxidation and, mineralization and partial humification of waste organic matter. This results in a stabilized, pathogen-free, non-toxic product to plants with important chemical properties such as high pH and significant nutrient contents, which can be used for soil conditioning and plant nutrition (Chowdhury et al, 2013; Martínez-Blanco et al, 2013). The leachate from the pile transports chemical elements from the composting material. P, Cu and Zn contents of 1.2 to 32.7, 0.3 to 3.0 and 1.0 to 5.0 mg L-1 have been found in 100 to 800 L of leachate per m2, obtained from piles with 460 kg of dry matter per m3, respectively (Christensen, 1984; Christensen & Tjell, 1984; Chatterjee et al, 2013)

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Conclusion