Biomethane Potential of Various Wastes from Ontario Vegetable Greenhouses

The Leamington–Kingsville (L-K) area has one of the highest densities of vegetable greenhouses in North America that produce tomatoes, cucumber, and bell peppers. Over time and with the variability of the crop cycle greenhouse production leads to large quantities of organic waste (produce, leaves, stalks, and vines and other components), which accounts for an estimated ~ 98000 tonnes of waste produced annually in the region. In Canada, approximately 90% of organic waste ends up in the landfills, which include greenhouse waste, leading to greenhouse gas emissions through decomposition. This can substantially impact the environment, the economy, and society. Anaerobic digestion has become a method of interest in treating this organic waste and converting it to energy, while saving landfill space. This process produces biogas which is a renewable resource that can be used for electricity generation or as a transportation fuel. In this study, biomethane potential (BMP) of organic wastes for three greenhouse vegetable (tomato, cucumber, and bell pepper) operations in L-K area was determined using a batch test under mesophilic conditions (37°C). The wastes tested included crop wastes (tomato, cucumber, and bell pepper) and leaf wastes (cucumber and bell pepper) from crop grow/harvest cycle, and end-of-crop-cycle waste (cucumber). All crop waste types produced more methane than their respective leaf wastes, with tomato producing the highest overall biomethane yield of 351 NmL CH4/ g COD added. The end-of-crop-cycle (cucumber) waste produced the least biomethane yield of 135 NmL CH4/ g COD added.