Nebraska Tree Stands + Co-firing = Electricity

Last year, the Nebraska State Forest Service approached the Nebraska Public Power District (NPPD) with the idea of utilizing dead standing trees for electricity production. A series of different invasive insects and diseases such as emerald ash borer and thousands of cankers disease are threatening ash and black walnut trees in Nebraska. Those tree stands could produce a significant woody fuel source considering that Nebraska has 1.2 million acres of forestland producing a net 1.47 million air-dry tons of biomass every year; non-forest land with trees produce an estimated 597,000 dry tons, and an additional 270,000 green tons of wood waste are generated through smaller woody biomass processes in the state. Dead and diseased trees left standing pose an increased fire hazard, and it’s pretty clear we’ve got biomass to burn.

The Forest Service's question was whether Nebraska could burn woody biomass in a co-firing configuration at electrical generating stations designed to run solely on coal. While co-firing is less flashy in the renewable circles than research and testing of biomass electrical generating plants, the benefits associated with co-firing could include lower operating costs, reductions of harmful emissions like sulfur and mercury, greater energy security and, with the use of beneficial biomass, lower carbon emissions. Co-firing is also one of the more economically viable ways to increase biomass power generation today, since it can be done with modifications to existing facilities.

So, the State Forest Service worked with NPPD to send samples of different infected tree species to the Energy and Environmental Research Center (EERC ) in Grand Forks, N.D for a month-long test to see how woody biomass  would affect heat rate, boiler fouling and slagging when blended at different ratios with coal. The EERC tested different wood types and co-firing ratios with 5, 10, 15, 20 and 25 percent biomass.

Several of the tree species appeared generally favorable for blending, especially at co-firing levels below 20%. From an operational perspective, the co-firing scenario looks possible. The trick is the logistics. The diseased trees are available, but unfortunately they’re not located right next to the power plant, or in concentrated areas generally. The dead trees spot the landscape, so harvesting, gathering, storing, and transporting the material will cost money.

With energy demands increasing, fossil fuel prices rising, and regulatory restrictions tightening, the economics might sort themselves out.  Cost-sharing could also take the biomass co-firing concept off Nebraska's drawing board and closer to reality