Exploring sustainable solutions for high-wire vegetable production
Authors: Jason Henry and Alexandra Grygorczyk
Canada’s greenhouse vegetable sector is one of the country’s most productive and technologically advanced agricultural industries, supplying high quality, locally grown produce year-round. Yet alongside this success, the sector generates substantial waste streams including vines, graded-out fruit, and used substrates, making landfill diversion both a critical objective and a persistent operational challenge. As part of an AAFC Clean Technologies funded project, Vineland Research and Innovation Centre (Vineland) is undertaking research with industry partners to develop valuable repurposing pathways for greenhouse waste streams, including stone wool.
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Greenhouse vegetable production has long relied on engineered substrates such as stone wool, coco coir, and peat-based blends. Modern growing media provide a uniform, controllable root-zone environment with optimal air space, water retention, and nutrient availability, conditions essential for high-wire crops such as cucumbers, peppers, and tomatoes. Their physical stability and compatibility with precision fertigation systems support intensive, long-season greenhouse production nationwide.
However, these agronomic benefits come with an environmental trade-off. At the end of each crop cycle much of this substrate material is landfilled along with the crop vines, a practice that is costly and environmentally problematic due to both volume and limited biodegradability.
Of the 150,000 tonnes of greenhouse waste landfilled annually in the Leamington region, an estimated 10-15% consists of stone wool. Other greenhouse-intensive regions, including Chatham, London, and Niagara, each contribute roughly 10% of Essex county’s total, further increasing the provincial burden. These figures reflect stone wool from vegetable production only and exclude other substrates and sectors such as ornamentals, leafy greens, and cannabis. Consequently, the true volume of substrate waste across all medias is considerably higher, underscoring the urgent need for alternative, scalable solutions.
Sustainable Pathways: Recycling and Repurposing
While landfilling remains common, several initiatives are demonstrating that more circular approaches are possible. Grodan’s recycling and repurposing programs and Walker Industries’ composting efforts offer models for diverting used growing media from landfill. These early successes signal a shift toward more environmentally responsible and economically viable waste management options. However, there is broad recognition that scalable, grower-friendly solutions are still needed. As project partner Grodan explains:
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“At Grodan, we work with commercial partners such as Walker Industries in Ontario and others globally to provide practical, cost-effective end-of-life management options for used stone wool from greenhouse operations. While progress has been made, challenges related to logistics, material handling, processing capacity, and cost remain.
The work being conducted by Vineland will play a critical role in addressing these barriers by identifying new end-use applications and establishing scalable pathways that make end-of-life management more accessible, operationally simple, and cost-effective for greenhouse growers.”
Land Application: From Waste to Soil Amendment
Repurposing spent substrates as soil amendments is emerging as a promising alternative to landfilling. Research underway at Vineland is examining how materials such as stone wool, coco coir, and peat-based mixes can improve field soils. Originally engineered to retain moisture and nutrients in greenhouse systems, these substrates have shown potential to enhance soil structure, increase water-holding capacity, and support nutrient cycling when incorporated into agricultural lands at carefully managed rates. Early studies indicate improvements in aggregate stability, reduced soil erosion, and enhanced water infiltration; benefits particularly relevant for sandy loam soils common in Essex County, where moisture retention is often a challenge. With large volumes of spent stone wool generated locally, there is strong potential for a circular solution that supports both agricultural soil health and landfill diversion goals of the greenhouse sector.
Laboratory findings are encouraging. Vineland’s research has demonstrated that adding spent substrates can double or even triple the available water holding capacity of agricultural soils. Current work is identifying which soil textures benefit most while assessing impacts on erosion control and hydrology.
Vineland aims to continue this work through field evaluations in their specialized facility the ‘TreeCulture Park’ which is designed to safely test innovative products in a semi-controlled outdoor environment. This facility enables close monitoring of crop growth, soil hydrology, and leachate, helping ensure that new practices are both agronomically sound and environmentally responsible. Planned trials with crops such as corn, soybeans, and brassicas will help determine optimal application methods, impacts on yield and soil health, and potential challenges related to nutrient cycling or material behavior in the field.
Ultimately, such real‑world assessments are essential for developing best practices that enable growers to confidently adopt substrate reuse as part of sustainable production systems.
Agricultural Soil Health and Substrate-based Amendments
Healthy soils depend on a balanced pore structure, with air‑ and water‑filled spaces supporting root respiration, microbial activity, and water movement. In agricultural fields, compaction from equipment traffic, rainfall, and natural settling, reduces porosity and disrupts this balance, leading to poorer drainage, lower aeration, and increased crop stress.
Incorporating amendments such as spent substrates can help counteract compaction by increasing aggregation and creating more stable pore networks. By introducing additional macro‑ and mesopores, these materials improve aeration, infiltration, and moisture storage. The result is deeper root growth, improved access to oxygen, water and nutrients, greater drought resilience, and more consistent yields under variable conditions.
Regulatory and Practical Challenges
Despite their potential, using greenhouse substrates as soil amendments presents several practical challenges. Ontario’s land application regulations restrict where and how these materials can be used, especially when they contain elevated nutrients like nitrogen, phosphorus, or salts. Some substrates may require pre-processing or restricted application rates to meet environmental standards. Biosecurity is also a concern, as pests or pathogens may survive in spent substrates, potentially requiring treatment and verification before use. In addition, mineral-based substrates like stone wool, perlite and vermiculite do not decompose but rather break down slowly into fragments similar to soil minerals, which can be a benefit, but also raise questions about long-term soil compatibility and behavior.
Scaling substrate reuse across Canada will require further research to determine optimal application rates, storage practices, and quality control measures. A deeper understanding of these factors will support responsible implementation and help growers navigate regulatory requirements and practical considerations.
Learning From Other Sectors
Agriculture offers numerous examples of waste materials successfully repurposed as soil amendments. Mushroom compost, food-processing residues, and livestock manures now play crucial roles in building soil organic matter and fertility. More recently, paper mill biosolids, wood-fiber residuals, and anaerobic digestate have become accepted soil improvers following appropriate treatment and regulatory oversight. Even industrial by-products such as construction-derived gypsum and elemental sulphur have found agronomic applications. These examples demonstrate that, with research, regulation, and industry collaboration, waste materials can become beneficial inputs that advance sustainable soil management, and offer a roadmap for greenhouse substrate reuse.
Looking Ahead: Toward Circular Agriculture
For Canada’s greenhouse and field crop sectors, substrate reuse represents an important opportunity to advance circular agriculture. Research into how spent substrates interact with field soils is generating new insights into soil health, sustainability, and integrated waste management. As substrate volumes continue to rise, innovation and collaboration across industries will be essential. By turning waste into value, the greenhouse industry can reduce its environmental footprint while contributing to healthier, more resilient agricultural soils.
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The research was generously funded by Agriculture and Agri-Food Canada and the Sustainable Canadian Agricultural Partnership through the Clean Technologies program.