Sinograin installed nine inflatable silos in two Chinese provinces, with capacity of up to 10,000 tonnes per unit. They offer better airtightness and thermal insulation than concrete, at a comparable construction cost.
At the beginning of the 20th century, concrete silos became established as the standard for grain storage thanks to their service life, durability, low maintenance, impermeable walls and resistance to weather. In the middle of that century, galvanized steel silos gained ground as a more economical alternative: they were easier to assemble, required simpler foundations and offered more space with lighter walls.
In the 21st century, while steel remains the most common material, Chinese state-owned company Grain Reserves Group Ltd. (Sinograin) began in 2018 to develop "inflatable" grain storage units. Sinograin described these units as "a composite wall structure of three layers that includes a high-strength inflatable polymer membrane waterproof layer, a polyurethane thermal insulation layer and a reinforced concrete layer, which together form, from the outside in, an integral protective wall system."
The first unit was installed in June 2022 and eight more have been added over the past four years in two Chinese provinces. In an interview with World Grain, Yue Li, deputy general manager of Sinograin Chengdu Storage Research Institute Co., Ltd., identified five key advantages of these structures.
The outer layer of the silo is fully lined with a high-strength inflatable polymer membrane, which guarantees excellent airtightness. In January 2023, a professional testing body carried out three airtightness tests and obtained half-life values of 2,987, 4,312 and 3,485 seconds, respectively, higher than those of a traditional concrete silo. In controlled-atmosphere CO₂ operations, carbon dioxide consumption per tonne of grain fell by 0.432 kg.
As for thermal insulation, a comparison carried out in July 2023 showed that the heat transfer coefficient of the inflatable silo wall was 0.44 W/(m²·K), versus 1.48 W/(m²·K) for the traditional concrete silo, equivalent to three times better performance. Between mid-March and mid-June, the rise in internal temperature in the inflatable silos was approximately 4 °C lower than in conventional concrete silos.
The inflatable body is lined with the waterproof layer and the roof features a dome design, which ensures reliable long-term impermeability. The thin-shell dome structure keeps the roof under compressive stress during loads and makes the most of concrete's compressive properties; under identical conditions, it offers greater load-bearing capacity than a truncated cone roof, with lower stress under seismic and wind loads.
On costs, Yue Li said: "The construction cost of an inflatable grain silo is comparable to that of a traditional concrete silo." He added: "The cost of an inflatable grain silo is seven times higher than that of a traditional steel silo. However, in China, steel silos are normally used for grain transfer, which makes the cost comparison with storage silos practically meaningless."
As Yue Li explained, inflatable silos are not regarded as substitutes for steel or concrete silos, but rather a high-tech complement. While they offer advantages in airtightness and energy savings for long-term strategic reserves, they require a concrete base and specialized air pressure control systems, which makes them less practical for the rapid, decentralized daily turnover handled by steel silos.
"Like other types of storage units, inflatable silos use the same grain storage methodology as traditional concrete silos, including all processes such as grain handling, cleaning and dust removal, aeration cooling and grain condition control," he said.
Inflatable silos can be customized in size and capacity. "Currently, the largest single silo can store up to 10,000 tonnes of grain," Yue Li said. The inner reinforced concrete layer is designed for a 50-year service life, while the outer polymer membrane layer has a projected service life of 30 years. The dome is monolithic, with no structural joints, and withstands strong winds, torrential rain and snowfall.
"Inflatable silos demonstrate great adaptability to diverse geological and climatic conditions," he said. The company is working to optimize construction techniques, promote standardization and serial development, and accelerate mature, replicable and scalable technical models. "In the future, in response to the demands of green, low-carbon development, the installation of grain storage facilities will continue to be expanded and promoted," he concluded.
