OCCUPATIONAL EXPOSURE TO AMMONIA DURING INDUSTRIAL-SCALE ANAEROBIC DIGESTION COMPOSTING OF HOUSEHOLD WASTE

Abstract

Biodegradable waste material can be exploited through anaerobic digestion, an oxygen-free multi-stage process often completed by a composting step, which harnesses the power of microorganisms to break down organic matter. This waste-treatment sector is growing rapidly in France as it allows the production of valuable digestates and biogas (biomethane). One of the main occupational health concerns in this sector is exposure to ammonia. The present work focused on ammonia emitted over the course of several stages in the anaerobic digestion and composting process, and assessed employee exposure to this pollutant. Exposure was measured for distinct worker activities and work areas, as well as during the various steps of the process. The results revealed non-negligible ammonia exposure for workers operating in the dehydration (until 55 ppmV in the workplace and 17 ppmV on the worker) and composting (until 45 ppmV in the workplace and 17 ppmV on the loader driver) areas on several sites. A classical monitoring approach was supplemented by the identification of explanatory parameters contributing to exposure: material emissivity, amounts stored or handled, and ventilation systems in use. Based on these elements, recommendations were made on prevention choices, including reducing emissions at source namely by process improvement and management of stored quantities, improving existing preventive systems such as capture at source or general ventilation, and employee education to raise awareness of waste management risks and improve practices.