Cutting small trees and brush for energy can be done without harming Minnesota's northern forests, but the cost to do the work may be more than the profit.
That's the finding of the first comprehensive study of the environmental effects and economics of cutting so-called woody biomass.
Researchers looked at nine plots on the Superior National Forest before and after loggers cut the wood -- brush and small trees ignored by paper or boards. They tracked the actual cost of harvest and prices paid for the end product.
The study was conducted by the Twin Cities-based Institute for Agriculture and Trade Policy, the U.S. Forest Service and researchers from the University of Wisconsin-Stevens Point and the University of Minnesota.
Don Arnosti, who headed the project for the Institute for Agriculture and Trade Policy, said even when the study called for taking all the biomass off a site that was possible, loggers only managed to retrieve about two-thirds of the total, leaving plenty of cover behind.
When the project started in 2005, "I was concerned that, with the coming push for biomass energy, this wasn't going to work for the ecosystem,'' Arnosti said. "But what we found is that we ended up leaving about one-third of the biomass on the site even when we were trying to get it all.''
That's the average amount of trees and brush that foresters and scientists recommend to leave on logging sites, and the amount recommended in the state's voluntary biomass harvesting guidelines.
The study was less encouraging on economics. It found the cost for equipment, fuel and labor more than the price paid for the wood chips sold for energy.
Loggers already know that, after they cut large trees for paper mills, they can collect the tops and limbs of those trees and sell the tops for biomass to be burned for electric generation. Most biomass now being burned for energy, such as Laurentian Energy in Virginia and Hibbing, use that type of leftovers from traditional logging.
With soaring costs for fossil fuels, interest in homegrown, renewable and carbon-neutral biomass in Minnesota is peaking.
Researchers and others wanted to know if it was possible and profitable to target forest sites specifically for biomass -- sites that usually wouldn't be cut for paper mills.
The test results were poor.
At only one of nine sites did the value of the woodchips sold for energy exceed the cost to get it to market, and only then by $24 per acre. At eight of the nine sites, the harvest had to be subsidized. Since the tests were conducted in 2006, diesel prices have nearly doubled, rendering the economics even worse.
"The value of biomass for energy alone doesn't pay to get it out of the woods,'' Arnosti said. "I think that's why you aren't seeing a lot of these big plans move forward just yet.''
But that doesn't necessarily mean the effort doesn't make some economic sense.
If the Forest Service or other landowner already had plans to cut or clear the wood for fire prevention or wildlife management, harvesting for biomass energy can reduce costs. At six of the nine sites, using the wood for biomass energy reduced the cost the Forest Service otherwise would have paid for forest thinning for fire protection alone, the study found.
With high diesel fuel prices, the distance from the forest site to the market is critical, the study found.
"Just selling the biomass, it didn't even pay for my time and the fuel... It takes a lot of little broomstick-size pieces to get to a ton,'' said Lonnie Popejoy, an equipment operator for Birchem Logging. "But if the Forest Service can put up some money to help clear this stuff and prevent fires, rather than pay to fight fires, it might work.''
Arnosti said the idea of combining forest thinning for fire prevention efforts and wildlife management projects with biomass harvesting could help cut to taxpayers, create some logging jobs and provide an energy source.
"There are promoters out there who say the supply (of biomass) is limitless, cheap, profitable... the same things the timber barons said 100 years ago when they were cutting all the big pines,'' Arnosti said. "But I do think this (study) shows we have room for some biomass energy in Minnesota on a sustainable basis. If it's done right.''