Timber is generally divided into three categories, sawtimber, veneer, and pulpwood. Pulpwood is the lowest-grade product among the three, and in most cases it is the most abundant product in the forest, but what exactly is pulpwood, and what is it used for? Pulpwood traditionally refers to wood that is ground and processed into a fibrous pulp and used for papermaking, but it also refers to low-grade wood used for chips, energy, pellets, and engineered products. This can include wood used for firewood and wood converted into bio-diesel. In this article, we will dive into pulpwood, its characteristics, and all the products it is used for as well as its importance to the industry.
What Kind of Trees Are Used as Pulpwood?
Pulpwood can come from virtually any species of tree, either hardwood or softwood. However, The specifics for what is defined as pulpwood differ depending on species. In some cases, all trees of a given species is pulp, as there is no other use for these trees. In other cases, pulp comes only from a tree with certain characteristics. It is best explained by separating trees into categories of hardwood and softwood.
Hardwood pulp comes primarily from low value species and poor quality trees of any size. White birch, beech, and hop hornbeam, for example, are species that are usually regarded as low value and sold as pulpwood. However, even high-value trees like oak, hickory, and sugar maple are sold as pulp if their quality is too undesirable. In the photo below, this sugar maple is extremely low quality, and so it qualifies as pulpwood.
The holes, rot, knots, and limbs make this maple unusable for saw timber. However, its quality is irrelevant for the production of goods like paper, firewood, and more. Thus, it will be harvested and sold off as pulpwood.
In hardwood species, the size of pulpwood can be anything from 4″ up to 30.” Wood under 10″ in diameter is generally too small for sawtimber, so it gets classified as pulp automatically. However, when trees grow to sufficient size, they may become too difficult or even impossible for mills to effectively handle, rendering them unusable for sawtimber. Wood that falls in between these two ranges is judged on quality, not size.
The characteristics of softwood pulpwood are slightly different. Softwood has a much more regular growth pattern than hardwoods, and volume is much more important for softwood value, whereas quality is more important for hardwoods. Accordingly, the softwood trees that are used for pulpwood are too small or too rotten to be used for lumber. For example, the pole-sized timber in the photo below are likely too narrow to be used for dimensional lumber. Instead, It is likely they will be sold as pulp and chipped and ground for paper or pellet production.
However, larger trees can still be used as pulp. In most cases, however, this only happens when the tree is rotten or has too much defect or comes from a species not used for lumber, such as eastern hemlock or red pine. In the case of the latter two species, there is little commercial use other than pulpwood unless one lives in proximity to a specialized mill or processing facility.
In certain situations, local pulpwood markets can be particularly lucrative, and trees are planted (both hardwood and softwood) explicitly for use as pulpwood, so the size or quality is largely irrelevant. Such is often the case in the American south where pellet markets are crucial, as well as in South America, where eucalyptus is often planted for paper and engineered forest products.
What Percent of Standing Timber is Pulpwood?
While the percent of pulpwood in a given forest is of course variable and dependent on a whole host of factors, it is common for half of all products in a forest to go toward pulpwood uses. In Maine, for example, the Maine Forest Product Council estimates that half of all harvested timber is sold as pulp. That’s no small amount! With so much pulp in the market, it is a crucial to understand this piece of the forest economy, its uses, and how it relates to forest management.
Uses of Pulpwood
Pulpwood is an incredibly versatile forest product with a large diversity of uses. The main products it is used for, however, include, paper, pellets, chips, OSB and particle board, bio-fuels, and firewood.
Paper production is perhaps the most common and recognizable use for pulpwood, and this is where it gets the name “pulp,” which refers to the fibrous material of broken-down wood used to make paper and tissue. Both hardwood and softwood species can be used for paper, but each have unique properties that are best suited for certain products. Hardwood, for example, has short fibers that are suited for smoother and more uniform products, such as printing paper. Softwood fibers are longer and good for industrial papers like newsprint.
Wood pellets, used for heating homes and even electricity production is another popular use of pulpwood. Biomass in the form of unused tree tops, sawdust from mills, or whole trees that are pulverized is compressed into small pellets that can be stored, transported, and fed into boilers and furnaces easily. The species used to make pellets varies, and it is usually a mix. However, some resin content is necessary to bind particles together, so softwood is almost always a component.
Wood chips themselves can be a product made from pulpwood. Whether for mulch, energy production, or even playgrounds, wood chips are a versatile use for pulpwood. In some cases, roundwood is sent to a production facility that can specializes in manufacturing chips for consumer or industrial uses. In other cases, chips are made with woodchippers on the site of a logging operation and then trucked to a facility for further processing.
Oriented Strand Board and Particle Board
Just because wood is poor quality doesn’t mean it can’t be used to build houses and furniture. Oriented strand board (or OSB) and particle board are two incredibly common construction materials made from pulpwood. OSB is usually made from poplar and aspen species compressed together. It is used for sheathing on houses and as a subfloor. Particle board is common on economy furniture, such as IKEA furniture, and made from a mix of saw dust fibers and adhesives or polymers.
Bio-Diesel and Bio-Fuel
Though it is still a new process and technology, bio-diesel and other biofuels are another product that can be made from pulpwood. Much progress in marketing and production is yet to be made before bio-fuels from wood products hit the big time, but recent developments are promising. Additionally, with major companies like Maersk making plans to convert their fleets to run on bio-fuels, it is only a matter of time before such products become a mainstay in the forest economy and an important market for pulpwood.
By far the oldest use of pulpwood is firewood. Poor quality trees have been burned for millennia as a crude energy source as heat, light and cooking fuels. In the dark ages, coppicing was an early way to manage forests for the production of firewood fuels, so one could say that firewood was the original product of forest management.
These days, firewood is a relatively small market compared to other products, as most heat their homes with oil or electricity. That said, firewood is still an incredibly important and indispensable market to smaller landowners and loggers, especially to those who grow their own firewood on their forest land.
The Importance of Pulpwood For Forest Management
Despite being the lowest-quality and often lowest-value product in the forest, pulpwood markets are the backbone of the forest industry. Without ways to sell and discard low-value wood, high-grading, whereby only the highest-value trees are removed, becomes common practice. When this happens, producing superior outcomes from forest management becomes considerably more difficult, and forests are degraded over time.
While every forest, landowner, and timberland investor wants to see as much high-grade and saw logs as possible in the log piles, the truth is that pulpwood will always be a substantial amount of volume, and there must be a market for that volume. The forest industry lives and dies on pulpwood. Luckily, there are plenty of uses and markets for it, and there are likely many more to be developed in the years ahead, especially as we search for greener alternatives to wasteful materials. We will just have to see what the future brings.