Antioxidant activity and bioactive compounds of lettuce improved by espresso coffee residues

•First report on espresso spent coffee effect in antioxidant and bioactive compounds of Lactuca sativa L.•Fresh coffee by-products potentiated antioxidant activity and phenolic fraction of lettuce extracts.•Fresh coffee by-products at least doubled major and minor carotenoids in lettuce.•Composted coffee by-products greatly improved lettuce’s photosynthetic capacity.•Espresso spent coffee is a renewable feedstock for horticulture nutritional quality improvement.