Scientists at King Abdullah University of Science and Technology (KAUST) have developed and combined a new nanoplastic and biodegradable mulch to passively cool greenhouses in hot, arid climates like those in the Middle East. Applying their technology, they lowered temperatures of miniature greenhouses by 25 degrees Celsius and increased crop yields of Chinese cabbage by nearly 200%. The study can be read in Nexus.
The nanoplastic consists of polyethylene, the most widely produced plastic in the world, infused with nanoparticles consisting of the molecule cesium tungsten oxide. These nanoparticles absorb infrared light, which greatly contributes to heating the greenhouse, preventing this light from entering with minimal effects on visible light, which is the light that drives photosynthesis and plant growth.
"Most greenhouse covers, whether they are made of glass, polycarbonate or polyethylene, transmit more than 90% of light, including infrared light, which has no benefit to crop yield but generates heat. Our goal was to create a cover that lets good light in and keeps bad light out," said KAUST Professor Qiaoqiang Gan, who developed the nanoplastic and is an expert in passive cooling systems.
Even with the infrared light reduced, solar radiance caused by any light still heats the soil. Mulch is commonly used to reflect sunlight, keeping the soil cooler than otherwise. Cooler soil promotes more photosynthesis and thus more growth and better crop yields. The new mulch designed by Gan's postdoctoral researcher, Yanpei Tian, is made of biodegradable cellulose paper. As the plants grow leaves that offer shade to the soil, this mulch vanishes from the soil, providing a more sustainable solution to greenhouse cooling and better human health.