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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Songs from the Wood* - Wood Fired Electricity in New Hampshire – Part 1

In my last post we took a look at energy sources and costs for home heating, and we saw how relatively inexpensive wood is compared to most other fuel sources in New Hampshire at the moment. Only natural gas is cheaper on a dollar per heat content basis. Wood as a fuel is particularly intriguing in the New Hampshire context. A great deal of NH is forested. In fact, 84% of the State is forested and, of the 5.7 million acres of land in New Hampshire, 81% is viable timberland. Therefore, tree harvesting for electricity or home heating applications is a way we can use a local in-state resource to reduce imports of fossil fuels like coal, oil or natural gas. Utilization of NH forests also provides a lot of local jobs and, over the 20 to 30 year life of a tree, wood combustion does have a lower carbon footprint when compared to fossil fuels. 

Many folks believe that, over the long term, the use of wood for energy purposes can be viewed as being carbon neutral. In other words, the carbon dioxide that is released in the combustion of wood is offset by the carbon that was absorbed by the tree during the process of photosynthesis which converted the carbon dioxide into the organic matrix of the tree. This is not entirely correct as there is not a one-to-one correspondence of carbon dioxide in = carbon dioxide out. We have to take into account that a great deal of fossil fuel energy is used to manage the forest, harvest the wood, transport it and convert it into a form, such as firewood, woodchips or wood pellets, which can then be combusted. As a result, the total amount of carbon emitted in utilizing wood as a fuel source is greater than that absorbed during photosynthesis.
 

We generate a good amount of electricity in New Hampshire from the combustion of wood. In 2011 we produced 1.03 million megawatt hours (MWh) of electricity from wood-fired operations, which is equivalent to 5.1% of the total electricity produced in the State. There are presently seven wood-burning plants that generate electricity from wood chips in New Hampshire and this year we should see the commissioning of the State's largest wood-fired power plant, the Burgess Biopower plant, which is located in Berlin on the site of the old Frasier Paper Mill. This new power plant will increase the overall percentage of electricity generated from wood from 5.1 to 7.5%.

 

The map below shows the location of the various wood-fired electricity plants in NH and the table that follows provides the key for the locations shown on the map as well as information about the various operations.

The data in the table show that most of the wood-fired power plants are smaller operations with capacities of the order of 15 to 20 MW. At this time, the largest operating plant in the state is the 50 MW Northern Wood Power plant. This facility is owned by our largest utility company, Public Service of New Hampshire, PSNH, and is located in Portsmouth on the Schiller power plant site. This plant was started up in 2006, when PSNH converted one of the three large boilers at the Schiller station from coal to a wood chip fuel source. Most of the other wood-fired operations were built in the late 1980s when New Hampshire was encouraging home grown energy and PSNH was required to sign 20-year power purchase agreements with these new wood-fired operations. Over time, there has been a fair amount of change in the ownership of some of these plants as the attractions and economics of renewable energy have waxed and waned.

 

The generation of electricity from wood is an intriguing business and one that is full of opportunities and challenges – some of which I will discuss my next post. In the figure below I have sketched the value chain for the wood-fired electricity business, along with some of the important inputs and outputs.

 

In the first step, we have the lengthy process of tree growing and the incorporation of carbon into the organic matrix of the tree and sunlight into stored chemical energy – both of which will eventually be released during combustion. Active and scientific forest management is required to allow trees to grow to their full potential. This has to be done while countering insect infestations, drought, fire and a host of other problems. The average life of a tree is typically 20 years before it is harvested.

 

In step 2, we have the harvesting of trees from public and private lands. This process is now highly mechanized and involves large machines to take down the trees, remove the brush and load them for transportation. Because it is highly mechanized, a lot of fossil fuel, in the form of diesel and gasoline, is used, so there is a net energy input into this step.

 

In step 3, the logs are transported to the saw mills where they are converted into lumber, wood chips for paper pulp, wood chips for combustion and waste sawdust. A great deal of the waste sawdust is converted into wood pellets which many folks use as fuel in their wood-fired home furnaces. The sawmill conversion process is also highly mechanized and automated, and it too requires a large energy input. I will note that it is possible to combine the harvesting and chipping operations right on site where the trees are harvested. In these operations, the trees are taken down and are immediately run through a large wood chipper. The wood chips are then directly loaded onto trucks for transportation to the wood-fired power plants, thus bypassing the saw mills.

 

Finally in step 4, wood chips from the saw mills or chipping operations are then transported to the wood-burning plant, where they are stored in enormous storage piles. The wood chips then become the fuel for the power plant, and they are burned in large furnaces where the heat is used to boil water. The steam is then used to drive a turbine which drives an electrical generator that produces electricity. Other than wood chips, there are inputs of water and skilled labor as well as fossil fuels used to transport the wood chips into the feeders.

 

These wood-burning operations produce electricity that is fed into the electrical grid but an enormous amount of waste heat is produced as well. In a previous post, I provided data that showed that only a small fraction, 23%, of the chemical energy in wood is converted into electricity. In contrast, coal-fired power plants have conversion efficiencies of 31% and natural gas plants, on average, have efficiencies of 45%. The 77% of waste heat from these wood-fired operations is dissipated by the evaporation of water and by the hot gases exiting the tall emissions stacks from these operations.

 

A fact that is not often appreciated is that a lot of water is utilized in the production of electricity. The water is used to produce steam and to cool the off-gases and, as such, a lot of water is lost to the atmosphere via evaporation. It has been estimated that water consumption for electricity generation is of the order of 4000 to 8000 gallons per MWh of electricity produced. One megawatt hour represents the approximate monthly electricity consumption for a US home so every month your electricity usage results in the consumption of 4000 to 8000 gallons of water. However, it should be noted that the water consumption numbers for wood-fired power plants are substantially lower. Saving on water consumption is just another reason to turn off the lights and save electricity. A point I often make to students in the Franklin Pierce University MBA in Energy and Sustainability Studies program is that if you are in the energy business, you are in the water business as well.

 

A small amount of wood ash is produced from these operations and this is a valuable soil additive that is used by local farmers.

 

So if we step back and look at the energy and carbon dioxide flow aspects of the wood-fired electricity business, it is clear that it is a lengthy and involved pipeline from photosynthesis to electricity. It takes time, money, energy, labor, and fossil fuels to get forests to incorporate sunlight and carbon dioxide into the body of tree and for us to release that energy (and carbon dioxide). As a result of all the various fossil fuel-based energy inputs all along the way, it is clear that wood burning cannot be viewed as entirely carbon neutral. However for us, here in forested NH, wood does represent a better fuel source than imported fossil fuels which have no offsetting carbon absorption and the wood-fired electricity does provide a lot of jobs and livelihoods as we move along the chain from photosynthesis to electricity. Now if we could only do something about that 77% of wasted energy…..

 

In my next post I will take a brief look at the economics of producing electricity from wood, and I will wrestle with the issue of just how much wood could we burn in New Hampshire before we overtax our forests. In the meantime, remember that it takes a lot of fossil fuel, labor and water to convert the chemical energy in wood into electricity we use in our homes. Many times the songs we play in our homes on our CD players are powered by our forests. These, indeed, might be Songs from the Wood.

 

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

Mike Mooiman
Franklin Pierce University
mooimanm@franklinpierce.edu
4/8/13
 

(*Songs from the Wood was the title of and a song from Jethro Tull's tenth album. This album, with its distinct British folk rock sound, was quite a departure from Tull's earlier heavy rock and blues influenced recordings. This recording cemented Jethro Tull's reputation as a bunch of odd ducks making interesting and influential music. The cover art on the album also features the results of some wood harvesting. An old tune but worth a listen).

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Closer to Home* – Energy Conversion Efficiencies and Home Heating Fuels

This week I am not going to look at NH energy issues from my usual 30,000 ft viewpoint. Instead I want to focus right in on our homes and how we heat them. I was reviewing some publications from the Energy Information Agency and I was struck by the information on this map.

 

The map shows the predominant home heating fuel used in different parts of the country. In the bulk of the country, as shown by the states in blue, the key home heating fuel is natural gas. In much of the southern part of the country as well as the Pacific Northwest, most homes are heated by electricity (shown in red) and here in New England, New Hampshire is one of the handful of green states that rely on oil or kerosene for the bulk of home heating applications.

 

We in New England should be concerned about our dependence on oil for a number of reasons;

• We are reliant on a fuel source which is largely imported.
• We are reliant on a fuel source that has shown increasing price volatility over the past 10 years.
• Unlike much of the US, we are not reaping the financial and reduced carbon emissions benefits of the natural gas bonanza.

There is not much we can do in the short term to change the situation but it is important to understand the consequences of our overt dependence on oil heat. Let's look at some specifics.

 

In the table below I have listed the various home heating sources we use in New Hampshire along with their recent retail prices, their energy content in BTU/unit, their cost in $ per million BTU ($/MMBTU) and then, using the energy conversion efficiency concepts for each fuel I introduced last week, I have calculated the cost of the useful heating energy produced from each type of fuel.

 

 

I have used some of these data points to generate the chart below which allows us to directly compare the costs of the input and useful heating output values for each of these fuel sources on a common basis, $ per million BTU: the information is quite revealing.

 

 

Natural gas is by far the cheapest fuel source. In fact, electrical heating is 3.4 times as expensive and oil heating is 2.6 times more costly on a thermal energy output basis. Wood heating, either with regular firewood or wood pellets, is far better cost-wise, than oil or electrical heating. In fact, the costs for wood heating are presently only 30% higher than those for natural gas.
 

Even though natural gas is such a low cost heating fuel at the moment, most NH residents cannot avail themselves of this choice as in most parts of New Hampshire natural gas is simply not available. Without the low cost choice, we have to select between wood, fuel oil, electricity or propane.
 

Part of our choice will be influenced by the relative volatility of fuel prices. In the figure below I have plotted the historical costs of the various home heating fuels on a cost per energy content, $ per million BTU, basis. (These prices are uncorrected for efficiency factors.) The green data points show that, for a long time, wood has been the low cost fuel in NH and sometimes by a considerable margin. Oil and natural gas prices (red and blue, respectively) closely paralleled one another but, just after 2007 the prices diverged, with big increases in oil costs due to world market prices and decreases in natural gas costs due to the US natural gas supply bonanza created by fracking technology.

 

Even more recently natural gas prices have dipped below those of wood. It turns out that wood prices have a high sensitivity to the price of oil-based fuels, like kerosene, which are used extensively in the harvesting, preparation and transportation of wood-based fuels. As a result, high oil prices have lead to recent price increases in wood-based fuel sources. Electricity costs per unit of energy are substantially higher than any of the other fuels, with propane prices falling between those of electricity and oil.
 

When looking at relative fuel prices we have to take into account a number of other factors. Oil prices are generally more volatile and my guess is that they are likely to increase in the future but, on the other hand, I wonder how long the natural gas bonanza will last and whether prices will skyrocket higher sometime in the future. The relatively low cost and low volatility of wood-based heat make it an option well worth considering for home heating applications, especially if you don't have access to natural gas. 
 

I wrestle with these issues myself and I can get quite worked up about them. Like most New Englanders, I heat with oil and that drives me to distraction. I take some small comfort that oil heat is presently less expensive than electric heat and that I am able to store about a month's worth of oil on my property in the big ugly black oil tank I have in my basement. The folks reliant on natural gas have no storage capacity and a gas supply pipeline problem can result in the immediate inability to heat a home. However, that is small consolation when I consider the extra cost of heating my home. I have an average New England home and I burn about 850 gallons of oil per year for heat and hot water. This past year my costs for oil were about $3200. If I could convert to natural gas I would save almost $2000 per year. I would far rather be spending that money elsewhere than on a carbon-intensive, volatile, imported energy source.
 

Going with wood pellet heating would allow me to save about $1700 per year and, because natural gas is not even an option, maybe it is time to think seriously about the wood pellet burner for my home heating needs. I am, however, left with one nagging concern: if everyone in NH changed from oil heat to wood heat, would the New Hampshire forests be able to support that amount of tree harvesting or would we end up importing wood from Canada and the other parts of the US and therefore undo some of the cost and carbon savings associated with wood heating?
 

I trust I have left you thinking about your home heating options and their associated costs. If you have natural gas, you are indeed in a fortunate position because the rest of us are faced with heating fuel decisions that are quite complex. If you have changed over recently to wood pellet heating, let us know what your experience was.
 

Until next time, remember to turn off the lights when you leave the room.
 

Mike Mooiman
Franklin Pierce University
mooimanm@franklinpierce.edu
3/31/13
    

(*Closer to Home was the third album from the 70's power trio, Grand Funk Railroad, and the song I'm Your Captain (Closer to Home) is, I think, one of their finer tunes. In fact, this was the very first American rock and roll record I was exposed to so I have a rather special connection with this album. For a bunch of guys from Flint, Michigan, they made some good music, wrote some great tunes and left a lot of good memories. This is one of those albums (along with Led Zep II and Dark Side of the Moon) that I have had on LP, 8 track, 4 track, CD and MP3 formats! I believe I am showing my age.)

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