Wood chips are used as landscape mulch, animal bedding, and a fuel source for biomass boilers. Proper storage is essential to maintain quality, ensuring they remain dry and usable. Failure to manage storage conditions can lead to rapid decomposition, mold growth, or dangerous internal heating. This guidance outlines practical methods for preserving the integrity and usability of your wood chip supply.
Selecting the Best Storage Environment
The storage location significantly impacts the wood chips’ condition, requiring good drainage and air circulation. For short-term storage, an outdoor pile is acceptable if situated on a surface that promotes water runoff. This surface should be paved, graveled, or an elevated patch of ground to prevent moisture from wicking up from the soil.
For long-term preservation, an indoor structure or covered area is preferable, especially to maintain low moisture content for fuel or smoking chips. When storing outdoors, maintain a separation distance from structures, particularly wooden buildings. Piles should be kept 15 to 50 feet away from adjacent structures to mitigate fire risk and prevent pest migration.
The site should minimize direct, intense sunlight, which can cause the outer layer to dry too quickly and become flammable. A partially shaded location with good natural airflow is best. The area must allow for natural drainage, ensuring water does not accumulate and create a sodden base layer.
Essential Steps for Moisture and Quality Control
The primary goal of storage is preventing microbial decomposition, which high moisture and lack of oxygen accelerate. For biomass fuel, the target moisture content should be less than 35% to prevent self-heating and preserve energy value; a general storage goal of 20% to 30% maintains quality for all uses. Fresh, “green” wood chips often exceed 50% moisture and should be spread in a thin layer to air-dry before long-term piling.
To manage the pile, form long, triangular piles (windrows) rather than large, conical heaps. This profile promotes better water shedding and natural ventilation. Covering the pile repels rain, but use breathable materials, such as permeable membranes or loosely secured tarps. Non-breathable plastic sheets trap moisture vapor, causing condensation and accelerating mold and rot within the pile.
Periodic aeration, similar to turning a compost pile, is effective for releasing trapped heat and moisture. Turning the pile introduces fresh air and prevents anaerobic pockets, which are breeding grounds for undesirable microbes. For smaller quantities stored in wire cages or wooden bins, ensure the sides and bottom have sufficient gaps for continuous air circulation.
Safety Measures for Preventing Hazards
A significant risk when storing large volumes of wood chips is spontaneous combustion. This occurs when heat generated by microbial decomposition (bacteria and fungi breaking down organic material) cannot escape. If the internal temperature rises unchecked, it can reach the wood’s ignition point.
To prevent this hazard, limit the height of wood chip piles. For general storage, a maximum height of 20 to 25 feet is recommended, though moist, fresh chips should be kept under four feet. If storing bulk quantities, monitor the internal temperature using a long probe thermometer. Immediate action, such as turning or spreading the pile, is necessary if the core temperature exceeds 150°F (65°C).
Pest management is also important, as stored wood chips attract insects and rodents. Chipping newly cut wood to one inch or less can eliminate a high percentage of wood-boring insects. Storing chips in containers or on elevated pallets deters rodents, and keeping the area clean and free of debris limits potential nesting sites.