Utilization of Municipal Solid Waste Compost in Horticulture

Abstract

Composting of municipal solid waste (MSW) has long been considered an attractive waste management tool for effective reduction of waste volume and beneficial utilization of MSW compost (MSWC) can eventually turn waste into a resource. Horticultural applications are regarded as a high-end market of MSWC because the industry is in frequent need for high quality organic materials and is able to pay premium prices for various compost products. The historical, current, and future bark availability for horticultural use was quantitatively evaluated. With expected horticulture industry growth, increased demand of bark for other uses, and only a minor increase in the long term bark output, the total amount and share of bark to the horticulture market will likely decrease. This analysis indicates strong incentives to develop alternative substrate components, such as various organic waste composts. Utilization of a mixed MSWC as a substrate component in greenhouse and container nursery production was evaluated using 19 ornamental crops. Plant growth responded differently to substrates containing MSWC. In outdoor container production, 4 of 10 crops in substrates with 100% MSWC (in volume) grew equally to plants in non-amended pine bark (PB)-based substrates. Most plants (9 of 12) had similar growth in substrates with 75% MSWC than in the non-amended PB control. No plant growth was negatively affected by amendment of PB with MSWC at lower ratios (25% and 50% MSWC) and several species had better growth in substrates with 25% MSWC than in 100% PB and/or 100% MSWC. In greenhouse production, three of five ornamental crops had similar growth in MSWC-amended substrates than in PB alone. Growth responses to different irrigation levels and fertilization rates were not significantly affected by substrate amendment with MSWC. Under recommended fertilization rates, any growth contribution from nutrients in MSWC was likely minimal and occurred in a short period after potting. The effect of amending soil with the mixed MSWC on yield and heavy metal concentrations in edible parts of okra (Abelmoschus esculentus) and watermelon (Citrullus lanatus) were investigated. Addition of MSWC increased okra yield and watermelon weights over non-amended plots. There were no differences among all treatments in heavy metal concentrations in okra pods, watermelon pulp, or watermelon juice. Overall, our studies indicate current use of MSWC by ongoing research to integrate MSWC into horticultural production systems is warranted.