Can we build better compost? Use of waste drywall to enhance plant growth on reclamation sites

Abstract

Compost is a readily available source of organic matter and nutrients and is produced large scale in many jurisdictions. Novel advancements in composting include addition of construction waste, such as drywall, to address its disposal while potentially improving compost quality for use in land reclamation. Varying compositions (15–30% by weight) of coarse and ground waste drywall were added to manure and biosolids during composting. Six composts were applied at four rates (0, 50, 100, 200 Mg ha−1) to three reclamation soils (agricultural, urban clean fill, oil sands tailings). Response to composts was assessed in the greenhouse with three plant species (Hordeum vulgare L. (barley), Agropyron trachycaulum (Link) Malte (slender wheat grass) and Festuca saximontana Rydb. (rocky mountain fescue). Drywall added to biosolids or manure during composting had no detrimental effects on vegetation; any negative effects of compost occurred with and without drywall. In agricultural soil and clean fill, biosolids composts with 15% coarse and 18% ground drywall improved native grass response, particularly biomass, relative to biosolids compost without drywall. Drywall manure composts reduced native grass response relative to manure compost without drywall. Only low quality tailings sand was improved by 30% coarse drywall. Compost rate significantly affected above and below ground biomass in agricultural soil and reduced performance of native species at highest rates, suggesting a threshold beyond which conditions will not be suitable for reclamation. Grinding drywall did not significantly improve plant performance and use of coarse drywall would eliminate the need for specialized equipment and resources. This initial research demonstrates that drywall composts are appropriate soil amendments for establishment of native and non native plant species on reclamation sites with consideration of substrate properties and plant species tolerances to dictate which additional feed stocks should be used.