Forest restoration summit covers multiple topics
Panelists at the Rocky Mountain Forest Restoration & Bioenergy Summit on April 16 in Denver, Colo., discussed a broad array of topics ranging from forest management strategies to the integration of tourism and reforestation, to supply and economic considerations for forest biomass utilization. But common themes were evident with the close of the event: forest management is critical, stakeholder partnerships are crucial, and bioenergy applications can play a significant role in forest restoration.
During the panel, “The State of the Forests in the Rocky Mountains,” Joe Duda, Colorado State Forest Service deputy forester, gave a broad overview of Colorado’s forests and state land ownership, and discussed a state biomass availability mapping project conducted by the CSFS.
“Colorado has a great set of diverse forest types, everything from low elevation pinion juniper to high elevation spruce fir,” Duda said. “Some of those are fairly contiguous in terms of where they are; other areas have a great diversity of species within many areas. Pinion juniper is the largest [species], slightly more so than aspen.”
Colorado has a mix of state, local, private and tribal land, but the federal government owns the largest share at about 70 percent, according to Duda. Using that information, the USFS generated a mapping project on biomass potential in Colorado forestland. Duda and the CSFS used three layers of data sets relating to conserving forestlands, protecting forests from harm, and enhancing public benefits from trees and forests. “Then we looked at threats we’ll be facing in our forest landscapes—fragmentation, loss of forest products harvesting and infrastructure…the stream of government funds for land treatment getting smaller, insect and disease, threats of invasive species…and how we are setting up our forests under changing climatic conditions so they can be resilient enough to be able to adapt,” Duda said.
The goal of the project was to portray the lands with real potential to produce biomass, breaking down the state into counties. “We used a five-point scale, zero having no potential to the highest potential at five, and broke it down by slopes less than and greater than 40 percent,” he said.
Out of the 24 million acres of forestland in Colorado, 3 million acres fall into the high potential category, and 3 million are moderate. “A substantial portion of the state doesn’t have high potential for management,” Duda said. “…it’s dependent on forest type, ownership, management and accessibility, but part of it is that the land management decisions that we make now and the land use allocation decisions made over the last 30 years have a considerable impact not only on what we can manage in the future, but what we can do for potential outcomes of that landscape,” Duda said.
Kurt Mackes, senior research scientist at Colorado State University discussed some supply and economic considerations for utilizing forest biomass. “It’s very important, when looking at potentially available sources, to take it a step further and decide which ones are economically viable to extract and utilize,” he said.
During his presentation, Mackes broke down available sources of woody biomass into three categories: urban residues, energy crops/closed loop and forest biomass, and discussed yields than can be achieved using each. He said that when looking at the economics of a project, urban residues are typically the most inexpensive to utilize, so they garner a lot of interest. “But I try to interest people in forest sources as we get further into projects,” he said.
Closed loop or energy crops have considerable potential in the region, particularly purpose-grown trees such as hybrid poplars and willows, according to Mackes. While the production cycles of hybrid poplars can range anywhere from six to 12 years depending on region, the Colorado Front Range yield is typically four to 10 dry tons of woody biomass per acre per year from dedicated sites. “By comparison, our native forests typically grow less than one dry ton of biomass per acre per year,” Mackes said.
For open loop biomass or forest sources, Mackes said that there is a significant amount of small-diameter trees in the region, and finding ways to use small diameter wood is a real challenge. “We have a fairly large area of [ponderosa pine] thinnings here; the projects yield about 10 to 15 tons per acre in the Front Range,” he said. “If you look at the types of trees removed, 80 to 96 percent removed typically run less than 12 inches, and if you look at trees larger than that, they comprise of up to about 18 percent.”
About 60 to 80 tons of merchantable timber per acre can be removed at thinning projects, and when including unmerchantable timber, more than 100 tons per acre can be removed, according to Mackes.
While the mountain pine beetle tends to focus on trees more than eight inches in diameter, they do attack smaller trees as well. Regardless of size, the time the trees are left untouched can greatly affect how and if they can be used, according to Mackes. “They have a shelf life,” he said. “Utilization depends on wood quality, and wood quality can be impacted by a number of factors. The longer the timber stands dead, the more value it loses. We need to access, extract and utilize the timber as fast as possible.”
It is much better if the tree stands than falls because it rapidly begins to decay once it blows down. “So rate of fall becomes very important— within three to seven years, you’ll have decay in most of the trees killed, and within 12 to 14 years, 90 percent of the trees will blow down,” Mackes said. “Once that happens, the economics of removing the trees become very unfavorable.”
Most mills will be reluctant to take that wood after one to two years, but within five to seven years, there is better opportunity for wood pellets or oriented strand board. “The problem we have is that we don’t have an oriented strand board plant, so lack of infrastructure is a problem,” Mackes said. “For bioenergy purposes, as long as we can access the wood, we can probably utilize it.”
The wood supply from pine beetle-killed wood will be fairly short at five to 15 years, from Mackes’ perspective. “This disturbs some people, but it’s probably a reality—a large percentage of the mortality will go unutilized,” he said. “…there are many sources of wood biomass that can be utilized in Colorado and the region, and most being used is subsidized in some way. We need to get away from that if we’re going work on landscape scale, and of course to do that, we need to overcome all of the barriers and challenges that exist.”