Context :This master project focuses on the gaseous emissions and associated microparticles (microaerosols) during composting of food biowaste to help disentangling between the pros and cons of the local composting in the heart of cities. Food biowaste represents a third of household waste and are estimated to be of 170 kg per habitant/year. Local composting is currently booming as part of the city policies to achieve Carbon Neutrality in 2050. However, it raises environmental and health concerns related to gaseous and aerosols, some of which being allergenics, emitted with microbial decomposing organic matter during composting The diversity and abundance of volatile organic compounds (alcohols, ketone, terpenes, aromatics,…) emitted during biowaste degradation remain largely unknow and their environmental and health impacts totally overlooked while some VOCs, although emitted in vey small quantities, may be considered as smelly even irritant or allergenic.
Workprogram: This project aims to quantify and characterize the dynamics of VOCs and associated microaerosols (allergens) produced during food biowaste composting and identify the ecological factors regulating them down. We will test the work hypothesis that different biowastes (as measured though chemical quality, temporal aging, citizen habits) generate distinct VOCs emissions in terms of composition and abundance also with distinct microaerosols. At first step, in situ composting sites pertaining to Rennes metropole and experimentally manipulated composting will served to collect VOCs from distinct foodwaste composting situations. VOCs will be then identified and quantified using PTR-MS and µ-GC-MS equipments of the OSERen – EXPAIR platform. Aside, microaerosols will be measured with a particle counter (AQ Guard) and collected using a Coriolis biosampler.
Data analysis: In terms of data analysis, we seek to relate the VOCs emitted to the abiotic and biotic characteristics of source composts; gaseous VOCs emissions and associated microaerosols will be interpretated with the data on compost microbiomes (part of the PhD work) and intrinsic physico-chemical properties of composts. VOCs analyzes will be done with IONICON software and statistical modeling and multivariate analyses will be carried out with R. To quantify the environmental and health impact of each VOC and microaerosols generated during biowaste composting, a modeling through the Life Cycle Assessment (LCA) method will be tested.
As a whole, the internship will make it possible to know whether local biowaste composting are important sources of volatile compounds hitherto underestimated in urban ecology and if VOCs can have environmental and health implications, needing regulation adjustments.
Contact (name and email): mathieu.toutain@univ-rennes.fr, francoise.binet@univ-rennes.fr
Insertion within an ongoing research project:
This master project is part of the funded « AEROMIC” research project (ADEME, 2024-2027) that already holds the on-going doctoral work of Mathieu Toutain. This interdisciplinary project involves three teams from the fields of ecology and environmental sciences (CNRS, UMR 6553 CNRS ECOBIO, Rennes, UPEC University, LEESU – Paris-Est-Créteil and INRAE, UR OPAALE, Rennes).
Other information: The internship combines skills at the interface of environmental microbiology and functional ecology. A complementary interest in flux modeling or risks assessment would be an asset. The six-month internship, starting in January 2026, will take place in Rennes. A monthly allowance will be paid for the duration of the internship in accordance with current regulations.
The research subject is also eligible for a 6-month gap year internship, provided that the candidate is registered in a French university for the year 2025-2026.
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