Minimizing Hay Storage Loss from Heating or Fires

courtesy of iGrow

Successful hay storage is essential to preserving high quality forage, while ensuring desired performance from livestock and deterring economic losses from unwanted hay storage fires. The predominant reason that fires occur in hay is because of excessive moisture in the plant residue that results in heating when it is baled or stacked for long term storage.

Plant cell respiration burns plant sugars to produce energy. This is a normal process as the hay plant tissue dries down and is often referred to as “sweating” or “heating” and occurs until the plant material is less than 15% moisture. When the plant material has more than 20% moisture it can cause the mesophilic bacteria present to grow rapidly, which is encouraged by the excessive moisture present. This produces heat in the bale. The higher the moisture content the longer it takes for the bale to dry down. Correspondingly, the higher the temperature in the bale’s core will be as it works through the cycle of heating and drying. It is important to note that spontaneous combustion of hay bales can occur at interior bale temperatures of 170° F.

Minimizing heat damage and fire during storage

Once the hay has been baled it is best to minimize losses or the potential of enhanced heating especially if the hay has been put up at marginal moisture levels (close to 20% moisture).
• Storing inside is best to minimize losses from weather. In doing so, make sure it is weather tight and has adequate drainage to inhibit water from entering the building.
• If storing outside is your option, cover the hay with a waterproof type material. To help moisture absorption from the ground, hay should be stored on a bed of gravel or by lifting them above the ground via tires, poles or pallets. If you are unable to cover them, provide enough room between bales to allow for adequate air flow for drying to continue.

Hazards that exit with “hot” stored hay

It is important to be aware of the hazards that can exist when hay becomes “hot” or “heated”.
• Flare-ups can occur at any time once the hay has reached a temperature that is above the danger zone of 150° F. It should be disassembled and allowed to cool. If the hay bale internal temperature has reached 175° F spontaneous combustion can occur once it is exposed to oxygen, thus it is recommended that fire department personnel be present to help with disassembling the hay pile for cooling and that a charged water source / hose be available to help put out fires if they occur.
• Burned-out cavities can be extremely dangerous and may be present in hay if it reaches a temperature that is conducive to fire. A person may become trapped in a cavity as they are walking over the pile thus, it is recommended to wear a life line with a second person present and to also use boards for weight distribution on the top of a pile.
• Toxic gases such as carbon monoxide can be present if there is smoldering or burning hay. Hay that has been chemically treated may also emit toxic gas vapors as it burns. This should be communicated to all fire-rescue workers so that appropriate breathing apparatus gear can be worn.

Hay that has heated during storage will often appear brown or caramelized in color. Livestock will often like the caramelized flavor however, nutrients have been lost due to the excessive heating during storage. It is recommended to obtain a feed nutrient analysis prior to diet formulation to determine the quality of the forage.

We are often at the mercy of the weather when putting up hay under ideal moisture conditions. Therefore constant monitoring of hay moisture during baling and the temperature at storage time is essential to having high quality forages available for feeding livestock and for minimization of storage losses.