Sustainable Valorisation of Biowaste for Soilless Cultivation of Salvia Officinalis in a Circular Bioeconomy

The aim of this work is to assess the usefulness of biowaste deriving from Circular Bioeconomy (CBE) processes (i.e., vermicompost, compost and digestate), as growing substrates for the partial or total replacement of peat, by measuring the vegetation biometric parameters of sage (<i>Salvia officinalis</i> L.)—leaf area; Soil Plant Analysis Development (SPAD) value (index of chlorophyll concentration); fresh and dry weight of leaves; stem weight; root length. The results showed that vermicompost positively influenced most of above parameters (+16.7% for leaf area, +7.3% for fresh leaf weight, +6.4% for dry leaf weight, +8.5% for fresh stem weight, +0.9% for dry stem weight, +16% for root length) and, therefore, can be used as a sustainable growing substrate, alternative to peat, for the sage soilless cultivation. Yet, the results of some biometric parameters are better with peat rather than with compost (−7.2% for SPAD value, −47.3% for fresh leaf weight, −46.8% for dry leaf weight, −32.9% for fresh stem weight, −39.1% for dry stem weight, −52.4% for fresh root weight, −56.6% for dry root weight) and digestate (−30.2% for fresh leaf weight, −33.6% for dry leaf weight, −23.9% for fresh stem weight, −27% for dry stem weight, −51.8% for fresh root weight, −34.4% for dry root weight, −16% for root length). Therefore, these results are interesting for potted plants in nursery activity, while the above differences must be verified also after the transplanting of the tested plants in open field. However, the use of all the above growing substrates alternative to peat allows the sustainable valorization of food industry by-products, plant biomass, animal manure and the Organic Fraction of Municipal Solid Waste (OFMSW).