CLEAR-Doc Program
Marie Skłodowska-Curie COFUND grant agreement No 101034248
Working between Université Gustave Eiffel (Nantes) and Instituto de Ciencias Agrarias (CSIC, Madrid)
Thesis topic: Recycled materials for urban gardens
Supervisors: Denis Courtier-Murias (UGE), Marco Panettieri (ICA), Liliane Jean-Soro (UGE), Johnny Gasperi (UGE)

Thesis Abstract

The global expansion of urban agriculture practices and the scarcity of green surfaces drive increased
demand for soil-less cultivation systems and substrates. Commercial substrates are primarily
composed of peat, which is sourced from peatland soils that, when depleted, can become primary
carbon emission sources. Phasing out peat will require alternative cultivation substrates, which, in
the context of an urban circular economy, could derive from locally available waste. Nevertheless,
the potential pollution of secondary raw materials should be carefully managed to ensure safe use
for the public. Within this context, this thesis aimed at studying the pollution from substrate, to
edible fruit and to leachates in experimental urban gardens, where locally sourced wastes were
employed for alternative substrates formulation. The pollutants of interests where trace elements
(TEs) and microplastics (MPs). Trace elements pathways were studied in two urban gardens based in
Madrid (Spain) and Nantes (France), where substrate composed of urban byproducts, being
respectively totally organic and a mixture of organic and inorganic residues, were tested for the
cultivation of tomato plants, which were then studied in both edible and non-edible parts. Regarding
MPs, an analytical method employing pyrolysis coupled to gas chromatography and mass
spectrometry (pyro-GC-MS) was developed and then applied to polymer spiked substrates. In this
way, polymer recovery in the organic-rich substrates and derived leachates could be tested in a
controlled system, allowing to validate on-site the analytical method.