Knock on Wood* – Using Wood for Energy in New Hampshire

In my blog post Songs from the Wood, we took a first look at the business of generating electricity from wood. I am impressed at how much electricity we generate from our forests, and I believe there is more opportunity to use the natural resources of NH for energy purposes. In this post, I dig a little deeper to understand just how much energy we could sustainably harvest from New Hampshire's forests. This is an important issue as we have more and more homes and commercial enterprises changing over to wood for space heating applications and we also have the very large Berlin-based biomass plant that will be firing up sometime this year. We need to be sure that we do not overtax our forests and end up depleting them in a rush for biomass-based energy. 

To understand how much biomass we could harvest from our forests, we need to understand the extent of our forest reserves, their growth rate and the other products that are produced from this resource. In NH we have 5.7 million acres of land, of which 81% is considered to be viable timberland. This has not always been the case, and the history of New Hampshire's forest reserves is a fascinating one. The chart below, which is taken from "The Economic Importance of New Hampshire's Forest-Based Economy – 2011," produced by the Northeast State Forester Association (NEFA), shows the long-term forest coverage for NH all the way back to the 1600s.

 

 

 

In the 1600s, before the European settlers arrived, it is estimated that over 90% of NH was forested, but then as the settlers moved in and started aggressively harvesting the forests and converting them to farmland, the forest coverage decreased to just below 50% in the 1850s. In the latter half of the 19^th Century, we then had migration out to the West to develop the wide open western farmland. At the same time, we had the move from agrarian to industrial livelihoods prompted by the industrial revolution. These factors reduced our aggressive forest harvesting here in New Hampshire and over the next 100 years the forests naturally recovered to about 90% coverage in the 1950s. Since then, development for homes and businesses has nibbled away at forest acreage but we are still at an impressive 84% of coverage.

 

The USDA Forest Services estimates that the 4.6 million acres of viable timberland in New Hampshire translates into 304 million green tons of tree-based biomass - or what they refer to as "growing stock". The forest stock grows by about 2.2% per year, so the net annual growth is about 6.6 million tons. This is the amount of forest-based biomass we could sustainably harvest from our forest without depleting this natural resource.

 

We don't just harvest trees to produce wood chips for electricity generation. Trees are harvested to produce lumber, pulp for paper making, firewood for home heating and woodchips which are used to produce wood pellets as well as electricity. Based on 2009 and 2010 data, my estimate of wood usage for these various applications is shown in the table below.

 

 

My data and analyses suggest that we are using about 3.9 million green tons of wood based biomass per year or 59% of the sustainable harvest amount.

 

It should be noted that my forest utilization numbers are somewhat higher than the 2.8 million ton figure reported by NEFA in their 2011 report. Their figures suggest that we are only using 40% of the wood that we could sustainably harvest. The differences in the two sets of figures are, in part, due to some gross simplifications that I applied as I assumed that all wood harvesting and wood utilization happens in State. However, there is a considerable amount of wood that is exported out of State for further processing - such as that which is transported to the wood pulp operations in Maine. Also some wood-fired electricity plants will, depending on their geographic location and local woodchip prices, bring in woodchips from out of state. Regardless of the exact number, both utilization figures are relatively low, which means that our forests are growing and maturing and we also have substantial capacity for further sustainable utilization of our forests.

 

Let's now consider future usage of our forest resources. Presently the NH wood-fired power plants consume approximately 1.8 million tons of wood chips per year. The Berlin-based, Burgess Biopower operation, the State's largest biomass burning operation, will add another 750,000 tons to the wood chip usage when it starts up this year.

 

We also need to take into account that wood usage for home and commercial heating applications is increasing in NH. According to 2010 US Census data, there are approximately 515,000 occupied housing units in New Hampshire and 33,470 or 6.5% of the occupied residences are heated primarily with wood. Wood usage in these residences is captured in the wood pellet and cordwood data presented in the table above.

 

If we assume that, in an extreme case, 50% of the remaining homes in NH were converted to wood-fired heat, this would represent an additional 240,000 homes. Assuming the average NH home consumes 850 gallons of oil per year for heat, this would be equivalent to a consumption of ~6 tons of wood pellets per year per home. Overall, this would result in an increased wood pellet usage of approximately 1.45 million tons, which would require ~2.9 million of green tons of harvested wood. If we add these future applications to the existing wood usage for the State, we get the data shown in the table below. The totals indicate that usage could, in the extreme case I present, climb to 7.5 million tons - which would exceed the sustainable harvest limit by 15%. Naturally in an extreme situation like this, economics would kick in, wood prices would rise and wood would be drawn in from neighboring states and even from Canada

 

 

The scenario of 50% of the homes in the State using wood for heat is clearly an extreme one, but it does indicate that we need to be proactive and cautious about our wood- based resources. It appears that, if land development is well planned and we maintain our large acreages of woodland and we responsibly utilize our forests, we are, in the near term, far from overburdening the woods. There is available biomass capacity and, knock on wood, we should be OK for the near future for increased utilization of forest-based biomass.

 

Even though I am urging caution in the long-term utilization of our forests, there is another potential application for wood-based energy in NH that is worth consideration. With the growing aversion to renewable energy projects in the State, I have become intrigued with the possibility of using even more wood by using a combination of wood and coal, so called "co-firing", in some of the large coal-fired burners in the State. The Europeans do a fair amount of co-firing of wood and coal and this would be another way for us to use a home-grown fuel source as well as a way to meet some of our renewable energy portfolio requirements. It would also reduce the carbon footprint of NH's coal-fired operations. I will take the opportunity in a future blog to explore this possibility in more detail.

 

Until next time, remember to turn off the lights when you leave the room. You will be saving energy, water and trees.

Mike Mooiman
Franklin Pierce University
mooimanm@franklinpierce.edu
4/15/13
    

(*Knock on Wood is a song recorded by Eddie Floyd on the Stax label in 1966. It has been covered by a number of artists including Otis Redding and David Bowie. A disco version was also recorded by Amii Stewart which became a big hit during the late 1970s. Here is a great live version of the tune featuring Eddie Floyd with the Blues Brothers Band.)

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