Addressing Biomass Energy 'Alternative Facts'

Providing misleading, inaccurate, and sometimes outright fiction as facts could be called propaganda.  With overtones of Orwell’s novel Nineteen Eighty-Four, the term “alternative facts” has recently been coined.  Either way, it is biased and misleading information that is used to promote a point of view.   

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. 

Throughout the study, there is frequent reference to what it claims is an important distinction regarding how trees are used after harvest. From that point of view, making lumber is okay, but using the wood to produce wood pellets for energy is not. The study also frequently states that the harvest of trees cuts short their ability to continue sequestering carbon. 

The following quote from page 24 of the Chatham House paper embodies both of those concepts. “This argument implies that, once they have grown, what happens to trees later—whether they are left to grow further, or harvested and made into wood products, or harvested and burnt for energy—somehow makes no difference to carbon concentrations in the atmosphere. This is obviously not the case.”

That quote, which captures a logic presented in many other places in the Chatham House paper, presents a premise that is false and an “obvious” conclusion that is wrong, setting up a dichotomy that does not represent reality in order to justify inaccurate conclusions about the carbon impacts of using wood for energy.

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. 

Figure 1 shows the annual carbon sequestered in U.S. forests. The larger the negative number, the more carbon that is being captured in U.S. forests, whose carbon sequestration has increased by 13.6 percent over the past 25 years. Figure 2 shows the total carbon held in privately owned U.S. forests by state, and the percentage of U.S. forests that are privately owned. Most privately owned forests are working forests growing trees for the forest products industries.

Contrary to the either-or implications by the Chatham House study regarding harvesting trees versus carbon sequestration, a steady supply of raw materials for the forest products industries, including pellet production, does not mean reducing carbon stocks. But if the landowners stopped tree harvesting altogether? Would the Chatham House counterfactual be true?  Would carbon stocks grow?
 
Private owners of working forests are farmers who depend on the forest products industries for income. As long as there is demand for lumber, paper, chemicals derived from wood fiber, and other end products made from wood, forests will be grown to be harvested. Sustainable tree farming, i.e., continuously renewing forests, does not degrade the carbon sink function of working forests. 

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. 

There is very little added carbon benefit after a plot in the Figure 3 model reaches about 35 years old. The model also illustrates why there is no net new carbon added to the atmosphere if the stock of new growth on the landscape equals the stock of the harvested plot (i.e., the harvest rate does not exceed the growth rate). Suppose the tree farmer has 35 plots across the landscape of her forest in different stages of growth. In Figure 3, the carbon sequestered by each of the younger plots equals the carbon held by plot 35. If all of plot 35 were made into pellets, which is highly unlikely, and the carbon was released from the combustion of the pellets made from that harvest, that carbon would be sequestered by plots 1 through 34 over the next year. 

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. 

The highest value for tree farmers from a harvested tree is the sawlog. This is the lower portion of the tree that is large in diameter, and free from defects that would preclude producing lumber. The upper portion of the harvested tree is either too low in diameter, or is not straight and defect free, and therefore cannot be sawn into boards. That portion of the tree typically has been debarked and chipped for use in pulp and paper mills. 

Thinnings occur once or twice over the growth period of the mature trees.  Imagine trying to grow food crops without managing how many stems per acre are planted. If the plants are too crowded, productivity would be very low. That same logic applies to working forests. Selective thinning improves the growth rate and health of the remaining trees. The stands are thinned to allow the remaining trees to grow straight and tall, in order to maximize the production of sawlog quality timber. The thinnings typically have stems that are too small in diameter or are not straight enough for sawlogs, but they are suitable for producing wood chips for the pulp and paper industry or for wood pellets.

There is no black or white, mutually exclusive decision making to either use the wood for lumber or for pellets.  The same tree provides both. 

The Chatham House study’s thesis that there are two distinct alternatives for the use of harvested trees is wrong. Recognizing that error in their logic leads us to conclude that 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.

Some pellet plants, under specific circumstances during which there are no higher and better use for the wood, use whole logs from mature trees to make pellets. The Chatham House study mentions the Vyborgskaya pellet mill in Russia, and implies that there is a false labeling of the wood as “waste.”  The study lumps Enviva, the largest wood pellet producer in the U.S., into the same accusation. If the reader only depends on the information in the report, he or she would have the impression that these pellet mills are sourcing wood that could have been used for lumber production, or worse, are using wood that was harvested with no regard for the health of the forests. The study presents incomplete information that allows the reader to make incorrect conclusions.

The procurement of wood must be put into the context of the forest products industry in the region, and on the suitability of the logs used in that pellet mill for other purposes. About 80 percent of the whole logs going into the Vyborgskaya plant are aspen. Aspen is a relatively soft, nonconiferous tree that is not suitable for structural lumber, and thus has very limited demand for sawmilling. Using aspen for pellet production is helping to improve the health and future productivity of the forest, and is providing a paying market for an otherwise unwanted species.

Regarding Enviva, several peer-reviewed studies examining areas from which Enviva pellet plants procure wood have shown that the wood procurement practices used by Enviva provide a valued end use to otherwise nonmerchantable trees. The studies show that providing a market for otherwise nonmerchantable wood allows private forests that have deteriorated into nonmerchantable states to be managed into plots that will sustainably yield valued timber in the future for their owners and provide better habitat for wildlife. The Chatham House study does not tell that side of the story.

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.

That is an alternative future that does not depend on alternative facts.


Author: William Strauss
President, FutureMetrics
[email protected]
207 824-6702