Environmental Sustainability of Greenhouse Covering Materials

Abstract

The fundamental objective of the review article was to explore the ecological sustainability of greenhouse covering material based on the following themes; considerations for greenhouse materials, properties of polymers and glass, additives, fillers, stabilizers and reinforcements, performance, Ultraviolet (UV) transmittance, phase change materials (PCMs), and environmental sustainability. A comparison of various polymers (polyvinyl chloride (PVC), acrylic, D-polymer, Linear low-density polyethylene (LLDPE), polyolefins), and silica glasses illustrated that each type of greenhouse cladding material has its unique merits and limitations. The performance of silica glasses, PVC, polyolefins was influenced by weather, greenhouse design, plant under cultivation, percentage UV transmittance, incorporation of additives and stabilizers, reinforcements, and integration of photovoltaic panels into the greenhouse roof among other factors. Polymers can be customized to achieve 0%UV transmittance, slow-insecticide release, and anti-microbial properties. In contrast, glass materials are preferred based on suitable photosynthetically active radiation (PAR) transmittance and near-infrared (NIR) reflection and less risk of photo-oxidation. From an ecological perspective, polymers can be recycled via mechanical and chemical recycling, closed-loop cycling, and polymerization of bio-based feedstock. However, post-consumer plastic films do not possess the same optical and energy properties as virgin polymers. The combined benefits of different polymers suggest that these materials could be adopted on a large scale over the long-term.