Life Cycle Impacts of Greenhouse Tomatoes – Cradle-to-Gate Benchmarking of Ontario Production
Leamington, Ontario has the highest concentration of vegetable producing greenhouses in North America, producing 64% of the total production volume in Canada (AAFC, 2012). Over the past decade, the Ontario tomato greenhouse sector has optimized its energy and water consumption and is now working to quantify its environmental impacts in order to benchmark its environmental performance to European growers, and communicate its carbon footprint to consumers.
Life cycle assessment (LCA) methods have been used extensively in Europe to assess field and greenhouse tomato production (Martinez-Blanco et al., 2011; Page et al., 2012), and to compare the environmental profiles of greenhouse products under various climates and management practices (Cellura et al., 2012; Torrellas et al., 2012). A cradle-to-gate LCA study was developed to assess the environmental impacts of the Ontario tomato greenhouse sector using primary data from 8 producers. The system boundaries included greenhouse structure, tomato production, and transportation of plastic and organic waste off-site. Application of fertilizers and pesticides, heating, electricity, growth media, packaging, and waste production were included in the model.
Heating with natural gas and fuel oil contributed 70 and 95% of global warming potential (GWP), cumulative energy demand, smog potential, and ozone depletion potential. Fertilizer and electricity consumption were other major contributors to the overall impact. A scenario utilizing wood chips for heating indicated a decrease in the GWP and ozone depletion potential by about 80 and 90%, respectively, relative to natural gas and fuel oil, and an increase in other impact categories.
Ontario greenhouse tomato production generates about 3.2 kg CO2e /kg tomato produced. Comparing this research to similar LCA studies, adjusting to provide comparable system boundaries (greenhouse structure, fertilizers, electricity, heat, and waste), carbon emissions were calculated at 2.8 kg CO2e/ kg tomato produced. Although this estimate was lower than reported in the UK (9.4 kg CO2e /kg tomato; Williams et al, 2006) and Hungary (5.1 kg CO2e/kg tomato; Torrellas et al. 2012) with similar technologies and climates, it was higher than in the Netherlands (2.0 kg CO2e /kg tomato; Torrellas et al. 2012), where combined heat and power (CHP) technology is employed.
The Ontario greenhouse sector is exploring alternative technologies including biomass heating and CHP systems. In December 2013, the provincial government announced a new CHP program for the greenhouse industry that will enable recovery of carbon dioxide and heat for greenhouse operations (Ontario Ministry of Energy [OME], 2013). Research findings provide a benchmark for understanding how these alternative technologies change the environmental profile of greenhouse tomato production and identify scope for improvements in operations.
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