Spent coffee grounds (SCG) represent a high-volume food waste worldwide, and several reuse approaches have
been attempted. Herein, a greenhouse field experiment was carried out by cultivating Batavia lettuce with 5%,
10%, 15%, 20% and 30% (v/v) espresso SCG directly composted in the soil. Healthy vegetables were obtained for
all treatments, without yield loss for up to 10% SCG. A progressive increment of green color intensitywith increasing
SCG content was observed, corroborated by the increase of their photosynthetic pigments (chlorophylls and
carotenoids). Furthermore, total ascorbic acid and tocopherols showed statistical significant increases (p b 0.001)
between control and all tested groups.Marked variations of nutritionally relevant minerals, particularly potassium,
phosphorous and sodiumwere also revealed at higher percentage treatments (20% and 30%). This approach
constitutes a clean, direct, simple and cost-effective measure to produce value-added vegetables, while reducing
food waste disposal.
