Siberian elm (Ulmus pumila) is a fast-growing, non-native species widespread across North America, making it a common source of available wood. While it is not ranked among the best hardwoods, Siberian elm is generally considered an acceptable firewood choice. Its suitability balances a respectable heat output with the considerable labor involved in its preparation.
Defining the Quality: Heat Output and Density
Siberian elm is classified as a medium-density hardwood, placing it above most softwoods but below premium woods like oak or hickory. The heat energy it provides, measured in British Thermal Units (BTU) per cord, is respectable. A cord of seasoned Siberian elm is estimated to yield approximately 20.9 million BTUs.
This heat output is comparable to mid-tier hardwoods, such as red elm or black walnut. This is noticeably higher than softwoods like pine, which often fall below 17 million BTUs per cord. However, it does not reach the output of woods like white oak, which can exceed 24 million BTUs per cord.
The density of Siberian elm determines its moderate energy content. While dense enough to offer a sustained burn, it is slightly less dense than American elm. This means it will not provide the same prolonged, intense heat as the densest hardwoods.
Preparation Logistics: Splitting and Seasoning
The most significant challenge associated with Siberian elm is the effort required to process the logs into usable firewood. This difficulty stems from its highly interlocked grain structure, which resists the clean splitting action of a wedge or maul. Instead of cleanly separating, the wood fibers tend to tear and string, making the process frustrating, especially with knotty or wet pieces.
Splitting Siberian elm when green or freshly cut is notoriously difficult and labor-intensive. The wood splits more easily after being allowed to dry slightly in the round or when frozen solid during winter. Hydraulic splitters often struggle with elm, requiring significant force to tear through the stringy wood rather than cleanly splitting it.
A notable advantage of Siberian elm is its relatively fast seasoning time compared to denser hardwoods. Although it holds a large amount of water when first cut, its moderate density allows it to dry out quicker than oak or sugar maple. Siberian elm can be adequately seasoned and ready to burn in about one year. Proper seasoning, which involves stacking the split wood off the ground in a well-ventilated area, is essential for optimal performance.
Behavior During Combustion
Once properly seasoned, Siberian elm performs acceptably in a fireplace or wood stove, offering moderate and steady heat. Well-dried elm produces less smoke compared to unseasoned wood, which benefits indoor air quality and chimney maintenance. The wood tends to burn for a moderate duration, providing sustained heat without requiring constant tending.
Siberian elm produces coals that are moderate in quality and lifespan. They will not hold heat as long as the dense, long-lasting coals from premium woods like oak or hickory. The coals are sufficient for banking a fire overnight but may not remain hot for extended periods.
The wood typically burns with a pleasant or neutral odor, though some report a less desirable smell when splitting it green. Siberian elm can have a tendency to spark or pop, particularly if the bark is left on, making a fire screen advisable in open fireplaces. The overall burning experience is satisfactory, provided the user has overcome the initial hurdle of processing the logs.