by William Strauss (FutureMetrics/Biomass Magazine) ... The recently released paper by the Chatham House is a study that contains many inaccurate statements about the use of wood for energy. Those statements are presented as facts, or as uncontested conclusions. This article will focus on the study’s discussions that pertain to the sourcing of raw materials for industrial wood pellets.
At the heart of the matter, it appears that the study does not understand how the forest products industry operates. In the U.S. and Canada, and many other countries, there are vast working forests whose purpose is to produce the raw materials for many industries. Those forests are valued assets to the landowners, tree farmers and the buyers. Sawmills, pulp mills, and many other wood products mills, including pellet mills, depend on a continuous daily input of wood to produce products that are used in one way or another by just about everyone, every day.
To enable and ensure a continuous supply of raw material, the quantity of the logs and chips coming into the mills cannot exceed the growth rate of the surrounding managed forest. Otherwise, the mills, worth hundreds of millions of dollars, would have to close once they depleted the resource they depend on to operate. Sawmills, pulp mills, and pellet mills are sized to match the ability of the surrounding working forest to supply affordable wood, every day, for decades. Sawmill, pulp mill, and pellet mill business models require good forestry practices that yield a sustainable outcome. But beyond that, particularly for industrial wood pellets being exported from the U.S. and Canada into the U.K. and other nations, there are rigorous certification schemes that demand auditing to prove that the forests are not being depleted, and that the stock of carbon held in the forests is not being reduced.
The millions of hectares of working forests in North America that supply the forest products industries are like the millions of hectares of cropland in North America. The trees, whether grown on large plantations in the southeast U.S. or in the immense managed hardwood and softwood stands in the northern states and Canada, are being grown to be harvested. These forests are dynamic systems that are in many stages of growth. There are mature trees that are ready to harvest, areas of new growth, and many plots that are in stages of growth between seedlings and mature trees. The purpose of tree farming is to supply wood fiber and its many byproducts to industry.
Privately-owned forests in the U.S., which make up about 60 percent of all U.S. forestland, are managed to continuously produce the raw materials for making lumber, paper, pellets, and other products derived from wood, and hold billions of tons of carbon. The landowners of those private forests and the workers who manage and harvest trees get paid for growing and producing wood fiber, not for sequestering carbon. However, the inherent sustainability of the resource that accrues from good forest management practices means that the aggregate carbon stock held in private forests are not being depleted. In fact, quite the contrary.
For any forest, there are diminishing returns to carbon sequestration as trees in the forest age. For many years, the growth rates and carbon sequestration rates increase as the trees in each plot age. But all forests reach an inflection point, and then an equilibrium at which the growth rate and the mortality rate equalize and the stock of carbon held in the forest stabilizes.
In the real world, the harvest, conversion to pellets, and combustion of those pellets is continuous throughout the year, across many landscapes. The CO2 released in combustion is absorbed contemporaneously by the new growth in the many younger plots that match or exceed the removals from mature plots.
Sustainable forestry practices, mandated by the sustainability criteria that qualifies wood pellets for use in U.K. power stations, assure that the biogenic carbon cycle continuously sequesters at least as much carbon as is released by the combustion of pellets. There is no such thing as a carbon debt if the stock of carbon held in the forest is not reduced.
Further undermining the Chatham House study is another false premise. The study’s author does not seem to understand that harvested trees have more than one purpose. For the most part, mature trees are not harvested just to make lumber or just to make wood pellets. The landowners, foresters, and loggers work together to maximize the value and productivity of the working forests.
The study is correct in stating that the preferred raw material for wood pellet production is sawmill residuals (sawdust, chips and shavings). What was sawmill waste becomes a valued feedstock for pellet production. In many locations, sawmill residuals from structural lumber production are abundant, and they supply much of the raw material needed to produce wood pellets. In other locations, there are insufficient sawmill residuals. In those locations, the pellet mills, just like the pulp mills, use of the nonsawlog portions of the tree. Just as sawdust is a byproduct of sawmilling, pulp or pellet grade wood chips are a byproduct of growing and harvesting trees for lumber production.
... if they are okay with harvesting wood to make lumber, they should be okay with using the upper portion of the tree and the thinnings for making pellets.
There is certainly a place for independent and critical oversight of the industrial wood pellet sector. There are some areas of the world where industrial wood pellets are produced from questionable feedstocks. There are some end users of industrial wood pellets who are less than rigorous in certifying the credentials of the producers. But the U.S. and Canada are not one of those places in the world, and the U.K.’s end users do engage in rigorous certification (as do those in most other jurisdictions). The Chatham House study is misguided in its focus.
Finally, the forest products industry in evolving. As the demand for paper declines, the opportunity for pellet mills to use the raw materials that would have otherwise gone to pulp and paper mills increases. In just one U.S. state, Maine, there have been six pulp mill closures in the past two and a half years. Those pulp mills used more than 2 million tons per year of biomass that could be made into pellets. The pellet industry will replace much of what is being lost. READ MORE