From humankind’s earliest efforts at mass agriculture over 10,000 years ago, little has changed in the challenges associated with grain storage. Efforts to seal and protect grain stores against losses to spoilage and pests have led to countless approaches to grain storage systems. In Spring Grove, Illinois in the Spring of 1873 the construction of what may have been the first above ground silo, was seen as a large departure from the bunker and pit storage techniques that continued to prove impossible to seal against the elements and biological processes that lead to spoilage. In the 1970’s and 80’s technologically advanced polymers were becoming commercially viable. These materials were resistant to ultraviolet degradation from sunlight, had a very high tensile strength and blocked the transmission of both light and gasses. These durable and lightweight materials facilitated the development of grain bagging as the most dramatic technological change in the approach to grain storage systems.
Prehistoric subsistence farming and grain storage has given way to globalization, warehousing and the agricultural apparatus required to feed a burgeoning global population. The trends toward farm amalgamation and the sprawling growth of high-efficiency farming operations polarizes the grain storage needs of the newly settled villages of 4000 - 2000 BC. Despite many advances in grain storage construction techniques, the challenges have remained the same while the need for flexible on-site grain storage continues to increase.
Regardless of the duration of storage, be it weeks, months or years, grain stores are continually in flux and subject to continual degradation and spoilage. From the natural metabolic processes within the grain itself, the elements of wind, rain and heat, birds, rodents, insects and micro-organisms continue to inflict spoilage losses estimated in the billions of dollars each year.
In the past century, advances in new construction materials and methodology have reduced spoilage. Average losses of 40% or higher in some cases have been reduced to 15-25% with the use of improved permanent storage structures. Grain silos of reinforced concrete for example, provide superior protection from the elements and outlast their wooden counterparts. Although they are not hermetically sealed, they are also not breathable structures and therefore do not allow for the exchange of gasses or release of moisture. For these reasons they generally require forced aeration or carbon dioxide infusion techniques to control heat, moisture and pests. They are also cost prohibitive in most farming operations.
Wooden grain bins and silos are a much more affordable grain storage structure and allow for breathability, but offer less protection from the infiltration of external moisture and pests. They also require a high level of maintenance and deteriorate over time.
Steel bins are the most common permanent grain storage structure, but also require a very significant capital investment of as much as $4 per bushel of storage capacity. Like their reinforced concrete counterparts, these structures are not hermetically sealed and can often require costly aeration techniques to mitigate their biggest downfall—convective heating due to the very high thermal conductivity of metal. This often leads to moisture migration and areas of high microbial activity and grain deterioration.
The one commonality between all of these permanent structures is that they are not hermetically sealed and require augmentation techniques to mitigate spoilage. Attempts to create controlled-atmosphere environments within these structures using flexible polyurethane, acrylic and elastic sealants have been met with limited or temporary success and longevity.