Polyvinyl-Alcohol Cellulose Fiber Foam as a Sustainable Greenhouse Growth Medium

Purpose: Mineral wool and peat are effective yet unsustainable growth media. We tested foam-formed paper with polyvinyl-alcohol (PVA) may be an inexpensive and sustainable replacement. Methods: We characterized the physical properties of 0%, 0.1% 0.25%, 0.5%, 1%, and 1.5% foam PVA by measuring compressive strain, tensile strength, water-holding capacity, and durability. We also grew Beefsteak tomatoes in greenhouse conditions for 2 months in PVA foam paper, measuring seed germination, height, and biomass. Results: Strain hardening occurred between 60 and 80% strain, with greater compressive force needed with increased PVA concentration. Tensile strength increased with PVA, measuring ~ 3000 and ~ 35,000 N/m² for 0% (control) and 1.5% PVA foam samples, respectively. Water-holding capacity increased from 363 mL in control samples to 403 mL in 1% PVA samples, with bulk ranging between 0.024 and 0.026 g/cm³. Foam paper durability increased with PVA and retained its form after two months of regular watering. PVA foam paper does not significantly contribute ions to irrigation solution and does not need a washing step prior to sowing. Height and biomass of tomatoes increased with PVA, and 1% and 1.5% PVA foam paper resulted in 100% seed germination. Conclusions: Tomatoes were able to be sown and grown in PVA foam paper substrate, and physical characteristics were enhanced with increasing PVA concentration. PVA foam paper has potential for mineral wool and peat replacement, and future work may further enhance desirable properties.