Wood Heat Concerns
B. Sustainability
Summary:
The subject of sustainability is necessarily very complex, and all but the most in depth analysis of this issue is subject to some degree of overgeneralization since the definition of ‘sustainable harvest’ is highly dependent upon a number of factors. Furthermore, a report conducted by the USDA outlines seven different criteria for sustainability ranging from conservation of ecosystem health and productivity, to carbon cycle maintenance and socio-economic stability. 1 From this perspective, wood heating can be shown to be sustainable by actively addressing these latter criteria (see Chapter 3: Why Wood Heat Should Be Incentivized, for details about the low-carbon and economic potential of wood heating). The purpose of this section is to show that wood heating is sustainable for the following reasons: first; residential wood harvesting generally has a light ecological impact due to its scale and dispersed nature; second, both pellet and cordwood supply often comes from waste wood sources; and third, cordwood harvesting on a larger scale has not been linked by any study or report as being a significant threat to sustainability of forests.
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Disperse Harvest/Homeowner Collected Wood
On the residential scale, firewood harvesting is generally very distributed and tends to exert little ecological pressure on forests. Personal firewood harvesting across the nation is much more likely to have small scale impacts on forests than larger operations, so although individuals will not be well acquainted with forest management practices, they will likely never exert a very large effect in one area. In many areas of the country, there is an abundance of forest resources that small-scale firewood collection/harvesting can utilize.
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Figure 21: Historic Residential Wood Consumption and Homes with Wood as a Primary Heating Source (EIA & Census)
The Forest Service’s Forest Products Laboratory calculated that in the 1980-1981 heating season, the amount of firewood consumed was 42.1 million cords. Just as importantly, they also estimated the amount of wood that was self-cut as compared to wood that was purchased. It was found that about 30 million cords (more than 70% of all firewood) was self-cut by users, with 3.9 million households obtaining wood from their own land, and an additional 3.4 million cutting wood from private land that they did not own.2 The remainder, according to the report, was either purchased or obtained from mill residues. As for more recent statistics on firewood consumption, EIA data suggests that current consumption rates are around 20 million cords per year, or about half of the 1980 rate (Fig. 21). This suggests that, as there were no documented sustainability issues associated with the firewood harvesting twenty years ago, wood heat use today could theoretically double without having a significant negative impact on the forests.
The above figure includes wood pellets since the energy source is listed by the EIA as ‘wood and wood-derived fuels’. However, this only suggest how much wood is being used for home heating, but does not reveal how much individual homeowners typically use or where they source their firewood. Although nationwide data on firewood harvesting is lacking, many regional studies and surveys offer insight into how residents procure their firewood. In New Hampshire and Vermont, the majority of firewood is either harvested by individuals or small scale logging operators. 3 A detailed survey from Minnesota found that 80% of residential firewood was harvested by households, with the majority of the material being sourced from dead trees (Fig. 22). 4 This dispersed nature is further demonstrated in Minnesota (which serves as a fairly good proxy for other states since Minnesota has a mix of both rural and metropolitan areas, as well as a percent forest cover that is very close to median for all states) by the fact that no wood vendor in Minnesota has over 1% of the market share. 5 Many other surveys throughout the country reveal trends similar to these.6
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Figure 22: Volume of Fuelwood Harvested by Fuel Source (MN Dept. of Natural Resources)7
Perhaps the most interesting trend that the Minnesota survey reveals is that the majority of homeowners still typically harvest their own firewood to heat their homes. A 1994 report described a similar trend in the Southeastern U.S. with 55% of residential cordwood gathered by the homeowner, 27% purchased and a full 12% of cordwood consumed gathered from waste wood sources. 8
Dealers that sell firewood to the public typically operate on a rather small scale. Often a dealer might only deliver several cords per year out of the back of a pickup as an income supplement. Larger dealers might have a small fleet of delivery trucks, splitting equipment, and employees capable of producing 2-3,000 cords per year. 9 Larger dealers sometimes do not actually harvest trees themselves, but rather purchase whole length logs from logging companies and simply process those into firewood.
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Fuelwood is Often Derived from Waste
Many tree services also process and sell firewood derived from urban tree trimming/removals. In fact, much of the wood utilized for pellets and even in many wood stoves, is derived from waste wood. Waste wood is either sourced from urban wood waste (generally in the form of tree trimmings and storm-felled trees) and the residues from logging and the pulp and paper industry. Despite the wide variety of end-uses for wood waste, 29 million tons of waste wood is produced each year, with a significant portion needlessly ending up in landfills. 11 A similar trend is often evidenced in commercial lumber harvesting as well: A West Virginia University study found that 8.4 tons/acre of wood residue was left after commercial lumber harvest that could have been utilized for heat. 12 A thriving residential biomass heating culture could reduce wood going to landfills.
Large Scale Harvest Sustainability Regulations
Finally, cordwood harvesting can occur on a larger scale than individual homeowners in an environmentally friendly manner. While every forest in the country has different levels of sustainable harvest (i.e., sustained yield), there are still millions of tons of biomass that could be harvested yearly without exceeding the yearly growth rate of forests. 13 The USDA’s Forest Inventory and Analysis Program can be used to evaluate a forest’s health and to assess how current management strategies will affect the forest years down the line. There is a range of adverse effects that can occur if wood harvest is not done properly. 14 These effects include reducing biodiversity, exposing soil to drying and erosion, eliminating habitats, decreasing the food supply for beneficial insects and wood-boring species and limiting flower growth.15 To protect against these impacts of environmentally unfriendly harvest, there are currently over 276 state agencies across the country with oversight of forestry activities or forestry environmental impacts and every state has Best Management Practice Programs, 16 as well as other policies and regulatory levers. These guidelines focus on a range of important issues including the amount of biomass debris to be left on the forest floor, wildlife and biodiversity, water quality and riparian zones, silviculture and soil productivity. 17 In a study by California Agriculture, it was found that local level education in environmentally sound harvest practices increased canopy level retention over four years of the programs. 18 This suggests that education on these practices may be important to the sustainability of firewood harvest.
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These guidelines focus on a range of important issues including the amount of biomass debris to be left on the forest floor, wildlife and biodiversity, water quality and riparian zones, silviculture and soil productivity. 17 In a study by California Agriculture, it was found that local level education in environmentally sound harvest practices increased canopy level retention over four years of the programs. 18 This suggests that education on these practices may be important to the sustainability of firewood harvest.
Forest Inventory and Analysis
http://www.fia.fs.fed.us/
As explored in chapter 3, cordwood harvesting can actually increase ecosystem health and forest productivity with sustainable harvesting techniques. Many forests throughout the country are severely overloaded with biomass due to the culture of fire suppression that has existed during the last century. For example, ponderosa pine forests in Arizona have 5-50 times the trees per acre as they did in the 1800’s, while the amount of forest floor fuel loads has increased by a factor of 100. Local officials in that area encourage firewood removal as a critical thinning activity by giving it away to residents for free. 19
Wood heating also has the potential to form synergistic relationships with other wood processing industries like sawmills, that focus on higher grade trees. 20 Since the wood heating market only requires lower value wood, it can provide an additional market to these industries, and thus provide increased management options that allow managers to avoid high grading. 21 In this same manner, using urban waste wood for home heating can ease the financial burden that local municipalities face from tree trimming, removal, and landfill costs.
Further Resources: Firewood Harvesting Guidelines 22
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Missouri: Best Management Practices for Harvesting Woody Biomass
http://mdc4.mdc.mo.gov/applications/MDCLibrary/MDCLibrary2.aspx?NodeID=2055 -
How to Choose Firewood Trees- A guide for the small scale landowner
http://cce.cornell.edu/Environment/Documents/PDFs/Choosing%20Firewood%20FCFS.pdf -
Managing your Woodlot for Sustainable Yield
http://affluentpeasant.barkie.net/forest/susyield.htm -
Small scale firewood management
http://cce.cornell.edu/Environment/Documents/PDFs/Choosing%20Firewood%20FCFS.pdf
1 USDA National Report on Sustainable Forests. 2010
2 Wood Use: U.S. Competitiveness and Technology. (Washington, D.C: U.S. Congress, Office of Technology Assessment, OTA-ITE-210, August 1883).
3 White P. Future of Firewood. Farming Magazine. April 2011 <http://www.farmingmagazine.com/print-6687.aspx>
4 Minnesota Department of Natural Resources. Residential Fuelwood Assessment, 2007-2008 Heating Season.
5 Barber R. Certified Firewood Marketing Plan for Certified Wood from Central Minnesota. CAP Report 031. January 2001. Pg 8. < >
6Houck. J, Broderick D. Compilation of Residential Wood Combustion Surveys and Related Studies. Omni Test Laboratories. August 2003. < http://www.omni-test.com/publications/Comp2.pdf>
7 Minnesota Department of Natural Resources. Residential Fuelwood Assessment, 2007-2008 Heating Season.
8 Christiansen E. et al. Residential Fuelwood Consumption in the Southeastern U.S. Biomass and Bioenergy Vol. 5. No. 6. 1993. Pg. 491
9 Dolan, Thomas. Firewood Business Heed’s Market’s Call. Timberline, June 2006.
10 Heinze Bioenergy report, pg 11
11 Araman et al. 1997. Potential Material Sources for Board Products: Used Pallets and Wastewood at Landfills. Proceedings, 31st International Particleboard/Composite Materials Symposium. 189-195.
12 Grushecky, S. Wood Biomass in West Virigina. WVU Appalachian Hardwood Center. 1995
13 Perlack et al. A Bioenergy and Bioproducts Industry: The Technical Feasibility of a Billion Ton Annual Supply. Oak Ridge National Laboratory. April 2005. Pg. 16. * This study is now recognized to have been an overestimate and is currently being revised downward to perhaps half of that number. Much of this biomass will be diverted to the biofuel and power industries which are much less efficient than thermal uses of wood.
14 Some definitions of ‘sustainable harvest’ include measures to prevent these harms, while other definitions only address ‘sustainable yield’.
15 Gibson L., Balancing Act. Biomass Magazine. July 2009. <http://www.biomassmagazine.com/articles/2814/balancing-act/>
16 Evans et al. Revised Assessment of Biomass Harvesting and Retention Guidelines. Pg. 2 <http://www.forestguild.org/publications/research/2009/biomass_guidelines.pdf>
18 Standiford R. et al. Impact of Firewood Harvesting on Hardwood Rangelands Varies with Region. California Agriculture 50 (2):7-12. DOI: 10.3733/ca.v050n02p7. March-April 1996. <http://ucanr.org/repository/cao/landingpage.cfm?article=ca.v050n02p7&fulltext=yes>
19 Farnsworth, A. et. al. Flagstaff’s Wildfire Fuel Treatments: Prescriptions for Community Involvement and a Source of Bioenergy. Biomass and Bioenergy. 2003.
20 Lockhart & Nyland. Teaching professional codes of ethics to forestry and wildlife students. Natural Resources and Environmental Issues. Volume 12, Issue 1. Pg. 78. Jan. 2004
21 Taylor & Tankersley. Biomass Harvesting and Forest Stewardship: A Healthy Balance. University of Tennesse Agricultural Experiment Station. Dec. 2007 pg 1.
22 Evans et al. Revised Assessment of Biomass Harvesting and Retention Guidelines. Pg. 33 <http://www.forestguild.org/publications/research/2009/biomass_guidelines.pdf>