First, here’s some brief background on electricity generation from wood for those wondering:

Power generation comes in two forms in respect to woody biomass: 1) stand-alone power facilities, and 2) CHP – combined heat and power – where a heat use(r) is co-located with the power generating facility.  Small CHP facilities are very typical in the wood products industry where the heat (steam) is used on-site to dry green lumber. 

Stand-alone facilities are nowhere close to economical compared to other renewables (especially if you consider hydro) in the Pacific Northwest.  Hydro power can be produced for around $0.04- $0.05 per kWh on the Columbia River; wind power rates vary but typically are in the $0.06 - $0.08 per kWh; biomass plants vary greatly but, in general, can be in the $0.010 per kWh area (confirming these rates).  Additionally, the federal Production Tax Credit (recently extended) meant to spur renewable power generation gives a tax credit equal to $0.019 per kWh for wind, solar and geothermal, but only a credit of $0.009 per kWh for that derived from woody biomass.

State-level legislation is helping though; the recently passed RPS Oregon ensures that small-scale facilities (generating less than 10 MW) will have a buyer – large electrics are required by law to buy from these smaller facilities.  Often, these small-scale producers will sale their power to the grid at the higher rate and buy back the energy needed at the standard rate to make the economics more attractive.

The capital costs needed for woody biomass facilities are roughly $1 million per MW for facilities larger than 10 MW.  Small-scale facilities often have build-outs at a much larger cost per MW.  Economies of scale work against small-scale facilities driving production costs higher.   

CHP facilities fair better economically because of capturing the by-product of thermal energy (heat).  However, no federal legislation (including the PTC) recognizes thermal energy generated from CHP facilities as a renewable energy source. 

Here’s a primer on woody biomass generated by our Rural Voices for Conservation Coalition (RVCC) if you want to go deeper.   

And now specifically relating to forest slash and woody biomass:

To my knowledge, no woody biomass power facility in the Pacific Northwest currently uses forest slash as its sole-source of feedstock.  Often, this source is a relatively low percentage of the mix because of the cost to harvest, gather, and transport it.  Urban wood waste, wood chips (residuals) from wood products plants, and tree bark generated on-site (at a lumber mill or paper mill) often constitute the largest percentage of the supply.  For example, at the proposed 15 MW facility on the Confederation Tribes of Warm Springs Reservation (central Oregon), around 50% of the supply (confirming this number) will be forest slash from management activities.

The recent interest in using forest slash to generate power is also related to the need for forest restoration and fuel reduction treatments in fire-adapted forests (primarily east of the Cascades and throughout the inter-mountain West).  Fire preclusion and past management strategies (along with global lumber markets and a host of other factors) have resulted in overstocked forests that are more susceptible to natural fires.  We have experienced a recent upturn in the amount and intensity of stand-replacing wildfires, historically uncharacteristic in fire-adapted forests.

Across Oregon and Washington, there are many acres of forests considered to be at an elevated risk to uncharacteristic fire.  Using Forest Service data, a 2006 study estimated that 2.9 million acres across eastern and southwestern Oregon were at an elevated risk to uncharacteristic wildfire (excluding roadless areas and forests on steep slopes).  Because of reduced forest area on the east side of the Cascades, Washington State undoubtedly has fewer acres in this category, but at-risk forests exist across the state. 

Many of the small-diameter trees removed during forest restoration and fuel reduction treatments are too small to be utilized for solid wood products.  Removal costs increase dramatically for these stems since manual labor is expensive and forest harvesting machines were designed to handle much larger trees.  Capturing some value for the material (as in an energy feedstock) can subsidize forest restoration treatments – due to the cost of removals, costs are hardly ever covered. 

Removal volumes for typical restoration treatments can vary depending upon forest type and condition.  For a typical Ponderosa pine forest in central Oregon, the amount of woody biomass removed during restoration thinning that would be utilized as an energy feedstock can be between 10 – 20 green tons per acre.  Assuming 50% moisture content, this is 5 – 10 dry tons per acre (water must be driven off before conversion to energy).  What does this mean in terms of consumption – on to more stats and math:

• One dry ton of wood can yield 1 MWh of electricity
• Average electric consumption for homes in the US in 10.8 MWh per year. 
• Thus, one acre can produce the annual electric usage for one home
  

Over a 40 year period, restoration on the acreage in Oregon could power roughly 70,000 homes if forest slash was the only feedstock.  That would double if another feedstock (urban waste, for example) was used for 50% of the feedstock.   This is only accounting for woody biomass from forest restoration activities.  The logging slash of more typical regeneration harvests on the west side of the Cascades can yield similar or slightly more available woody biomass per acre (although this will mostly be consumed by and for use within the forest products industry).  

The bigger picture:

The wide-scale applicability of using woody biomass (in particular, forest slash) is somewhat problematic in the Northwest due to more affordable alternatives.  Again, hydro may not be the most favored “alternative energy”, but removal of dams along the Columbia isn’t a reality in the short run.  In general, power in the Northwest is much cleaner (from a GHG emissions standpoint) than the national pool, equating to 34% less GHG emissions per kWh than the national average. 

The potential of electricity generated from woody biomass from restoration treatments is not a huge source of energy when compared to current demand. Even reducing the timeframe above to 20 years and using other feedstocks for 50% of the supply, yields an estimate of 280,000 homes per year.  Another way to look at this though is to forecast future demand, in terms of projected growth for the Pacific Northwest.  In terms of affordable and efficient electric generation, other renewable are perhaps more worthwhile.  Woody biomass can be part of a cadre of renewables to meet future demand here in the PNW.

Displacing fossil fuel - from both a cost and GHG emissions perspective – should be a regional goal for the Northwest.  The most effective way to do that is with thermal energy projects – using heat in a process (drying lumber, greenhouses, etc.) or in a space (schools, large public buildings, district heating).  In rural communities, the heat source is often heating oil or propane, both with huge negatives in terms or cost and GHG emissions.  A dispersed network of thermal heat users could produce a rather large offset of fossil fuel usage.  Due to the current costs of heating oil, retro-fit projects are increasingly cost effective (with paybacks less than 10 years).  Newer technology boilers are quite efficient at utilizing heat (much more so than power generation) and can have clean emissions. 

We recently helped organize a workshop for community-based wood heat.  There is some information there regarding supply, project economics, etc. that may be of interest.