We like to think about killing two birds with one stone. Seems efficient. Burning forest biomass to create electricity is one of the potential solutions to reducing CO2 emissions and fossil fuel consumption. If forest biomass is grown sustainably, it can be produced indefinitely. Burning forest biomass also potentially creates the opportunity to improve forest health and keep jobs in timber-dependent communities. It seems like killing two birds with one stone if ever there was an example of it. That is a big part of the attraction of Second Substitute House Bill 2481 (2SHB 2481), which was passed by the Washington Legislature and signed by Governor Gregoire earlier this month. 2SHB 2481 authorizes Washington’s Department of Natural Resources to enter into forest biomass supply agreements to supply biomass from state trust lands.
Using forest biomass to create energy is in one sense very much old technology. From the first sawmills in Washington, mills have burned the sawdust and trimmings left over when a round log is turned into rectangular lumber (the classic square peg and round hole geometry leaves lots of waste) to power the sawmill itself. For at least the last decade, mills have had co-generation plants to generate electricity with the excess wood waste, that they then sell back onto the grid. But that forest biomass had already been delivered to a mill, where it could either be burned or would become a massive waste pile. Energy created from that wood was essentially free.
The forest biomass that is creating the attention now is very different from that wood waste that naturally made its way to sawmills. It results from at least two aspects of how we have managed our forests over the Twentieth Century. It is very often not associated with trees that it makes any sense to take to a mill to turn into lumber.
In the dry part of the Intermountain west, fire was a natural part of the ecosystem prior to European settlement. Relatively cool, low fires swept through the forest every few years. The forest naturally was dominated by trees that had bark that insulated the trees, so that they were not damaged by fire once the tree got tall enough so that their crowns got up above the flames. The forests were naturally quite sparse, because young trees that hadn’t grown that tall when a fire came along would be destroyed. An “old growth” forest before European settlement may only have had 25 or 30 trees per acre. And species that were easily damaged by fire tended to be rare, because their survival depended on the happenstance of being out of the way of fires over their lifetime.
Beginning in the early Twentieth Century, that all changed. With the creation of the U.S. Forest Service and Smokey Bear, the objective became to keep fire out of forests. At first, that seemed like the right thing to do. But as decade followed decade with no fires in areas that had evolved with fire, two things happened. First, the number of the trees in the forest increased greatly. Particularly on public lands, where thinning the forest was rare, all the trees that sprouted, including species that weren’t naturally prevalaent in the forest, had a chance to live and grow. And they did, at least for a while. But with far more trees competing for water in fairly arid lands, the trees tend to be stressed in the summers. The newly abundant species were often particularly susceptible to stress. And when the trees are stressed, that becomes an open invitation to what were endemic pests back when the trees were healthy, especially the mountain pine beetle. The upshot is that mountain pine beetle epidemics have exploded across the Intermountain west, killing hundreds of thousands of acres of stressed forests every year. Second, forests naturally create fuel for fires, in down limbs, natural tree mortality, and the growth of underbrush. In the fire regimes of pre-settlement times, that fuel was burned up by the periodic fires before there was too much of it. That allowed the fires to stay cool, so that the fires never reached the crowns of the fire-resistant trees. But with decades of no fires, the fuel in the forests has built up so that when a fire starts now, it tends to be a “hot” fire. The flames of a hot fire can reach the crowns of the fire resistant trees, where it can kill them just like any other tree.
The only solution to getting those forests back to where fire can be reintroduced as a normal part of management is to remove a significant part of the small trees and down fuel from the forest. Unless that can happen, the live trees remain stressed, their risk of being killed by beetles keeps going up, and the fuel from both the dead trees killed by the beetles and the fuel that has naturally built up over the decades makes the forest at risk of total destruction. And – forest fires also release a lot of CO2 into the atmosphere. But often the trees that need to be removed are too small to make into lumber. As a result there is no economic reason why a mill would harvest.
So the idea behind sales of biomass is to haul that potentially dangerous biomass out of the forest for the explicit purpose of creating electricity. If it is going to be CO2 anyway, let’s use it to create electricity rather than just burning it up in the woods.
The difficulty, at least so far, has been that this source of potential energy is diffuse. It is spread out over millions of acres. To be turned into energy someone has to gather it up and haul it to the generating plant where it can be burned. The generating plant will need to pass all modern Clean Air permitting, and all other environmental regulations. There will be exceptions to this rule, but in general the cost of hauling the forest biomass to where it can be burned, when the economics are not subsidized by the value of the lumber cut from the trees, has made the resulting electricity cost too much for the market to bear.
That may change over time, as legislatures impose renewable energy requirements on electric utilities. It will change if Congress passes a cap-and-trade bill. But the biggest thing that would help forest biomass become a significant part of our energy future is if someone would develop a way to make generation from forest biomass feasible on a smaller, more diffuse scale. In the early days of the forest industry, sawmills tended to be much simpler things. You could set one up close to where the harvest was occurring. They didn’t need to last forever. If electricity generation from the forests could be similarly mobile, if it were feasible to treat forest biomass as a source of distributive energy, then there is a lot of fuel out there waiting to be consumed. Until that happens, forest biomass, like so many other potential “solutions” to the need to develop “green” energy, is likely to be more promise than delivery. Killing two birds with one stone may result in not much more than two dead birds.