Optimized Substrate Formulation Using Industrial Instant Coffee Residue for Growing Amaranth and Chia Microgreens

The objective of the study was to determine the potential of instant coffee residue as material for substrates in the production of amaranth and chia microgreens using the mixture experimental design methodology. The residue was mixed with sand and sawdust following a simplex centroid design. Sawdust was favorable for substrate aeration. Sand, sawdust, and coffee residue mixture improved the water-holding capacity of the mixture (74 %), whereas a mixture of coffee residue and sand resulted in an adequate pH substrate (6.7). Both, substrate bulk density and particle size were observed to influence plant development. The formulation composed entirely of sand (100%) demonstrated remarkable improvements in mean stem diameter, root length, and hypocotyl height compared to other mixtures, establishing it as the best substrate for amaranth and chia growth. This finding underscores the potential of this substrate to develop an efficient and environmentally friendly growing medium for microgreens, thus contributing to urban agriculture and sustainable organic waste management.