Background

The greenhouse vegetable industry is one of the fastest growing sectors of agriculture in British Columbia. The crops produced by greenhouses include tomato, cucumber, sweet pepper and lettuce. Between 1986 and 1996, the greenhouse area increased from 36 to 78 hectares, and it is expected to double in size by Year 2000.

The industry currently produces over 10,000 tonnes of wastes per year. Organic wastes come from the residues of plants that are uprooted in November at the end of the growing season, as well as shoots, leaves and prunings during the growing season, and spent growing medium. Most of the solid waste from greenhouses is trucked to landfills, and some is land applied. Disposal costs the greenhouse operators over one million dollars in expenses for trucking and tipping fees each year; moreover, tipping fees are increasing and it is possible that most of the landfills will be closed by year 2000.

According to the Ministry of Agriculture and Food guidelines, composting of greenhouse wastes is considered the preferred organic waste management method. While avoiding trucking to landfills or land application sites, composting also converts the biodegradable wastes into a stable and useful product, which can generate revenues for the greenhouse operators. For these reasons, a project to investigate on-site composting of greenhouse wastes has been undertaken by the B.C. Hot House Growers Association in conjunction with The University of British Columbia (UBC).

Crop health and yield are critical to the success of greenhouse operators and the industry; accordingly, crop management techniques are constantly being refined to optimize production. Disease is an ongoing problem that continues to impact productivity and product quality. To counter the effects of disease, new cultivars as well as many chemical and biological control agents have been developed. Utilization of specific organic amendments can provide another tool against disease, by providing a general suppression of pathogens.

Utilization of greenhouse compost on site would complete the cycle of organic material. This would reduce energy costs of transporting waste off-site. Valuable nutrients that have been incorporated into the plant biomass during the season can be recovered and re-used in the greenhouse. This solid waste process is analogous to the irrigation wastewater recirculation now being adopted to conserve fertilizer nutrients.
 
 

The overall goal of the project is to develop a sustainable growing practice in the vegetable greenhouse industry. It can be achieved in two steps (objectives). First, we design and develop an appropriate bio-conversion technology for the composting of biodegradable wastes generated by the vegetable greenhouse. Second, we evaluate the quality of the finished compost, and the benefits of utilizing the products from the process back into the vegetable greenhouses as high-quality organic growing medium amendment. These applications are expected to provide benefits such as disease suppression, enhanced crop health and growth, and improved crop yield. By doing so, the greenhouse industry not only can achieve a sustainable growing practice with minimal waste output but also can benefit from the saving in waste trucking, fertilizers and growing medium and increase in crop yield as well.

Collaborators

This two-year project is conducted by researchers at UBC, under the supervision and review of the B.C. vegetable greenhouse industry. It is funded by the B.C. Greenhouse Vegetable Research Council, National Research Council of Canada and B.C. Ministry of Agriculture and Food. Results are evaluated in terms of the technical and economic aspects. For the technical aspects, the scientific and engineering merits are investigated by both the plant scientists and the engineers. For the economic aspects, a cost analysis, and the most feasible solutions are jointly developed with the growers.
 
 

Benefits

Based on the results to date, utilization of organic medium amendment is able to provide significant plant benefits. Disease suppression, combined with increased nutrients in the medium, results in increased overall plant growth, and improved crop health and yield, and would have direct impact to the greenhouse grower’s revenue. For example, a 5% yield improvement could lead to an annual revenue increase of over $180,000 for a 4- hectare (10-acre) tomato greenhouse. Accordingly, the requirement for chemical and/or biological pathogen controls and fertilizers may be decreased.

The world greenhouse industry, with Holland as the industry leader, often emphasizes production as natural and environmentally friendly. In this project, our ultimate aim is to make the B.C. greenhouses the leaders in the new era of plant disease control, via suppression of the pathogens without any other additives or manipulations to the crop. It is a good selling point for us to claim our products as more environmentally acceptable, and thus can enhance the international image of B.C. greenhouse products and increase the international sales and market. Moreover, this technology can easily be extended for usage in floriculture and nurseries, and provide them a more economic and effective ways of disease control.

Anticipated benefits of the project include the followings:

• Increased revenue and earnings potential for greenhouse growers with associated benefits to the government, resulting in improved economic sustainability.
• Improved product quality.
• Reduced environmental impacts, including waste handling and disposal and chemical usage.
• Improved productivity of vegetable greenhouses and therefore the occupied agricultural land.