1. Minnesota’s Residential Fuelwood Use Surveys
Lisa Herschberger
November 8, 2012
National Educational Forum on the Residential Wood Heater NSPS
Briefly describe Minnesota’s residential wood use survey design, share some examples of how the results can be useful for understanding air quality, and give an update on the ongoing 2012 survey.

2. Monitoring Long Term Trends in Minnesota Residential Fuelwood Use
Wood use and harvest data surveyed for five decades
Broader collaboration lead to expanded scope for 2003, 2008 and 2012 surveys
Minnesota Pollution Control Agency
United States Forest Service
Minnesota Department of Natural Resources
Hearth, Patio and Barbeque Association
Minnesota is fortunate in having a long record of residential wood use and harvest data from the work done by USFS and DNR for forest management purposes.
Over time the residential surveys have collected more detailed information about how the wood was burned.
Minnesota’s state air agency became more directly involved in the wood surveys about a decade ago, and since then there has been this broader collaboration among state agencies, the USFS and HPBA to collect this useful information.

3. MN Residential Wood Use Survey (Five Minnesota Survey Regions)
Aspen Birch
Northern Pine
Central Hardwoods
The map on the right shows the five regions of Minnesota regularly surveyed to learn how Minnesota residents burn and harvest wood. The four Greater Minnesota regions were established based on the types of forests and vegetation in those areas. The Metro is a small portion surveyed separately from the Central Hardwoods region.
The map on the left, which gives a basic look at Minnesota’s forests cover, help illustrate where wood is more readily available, and why the survey was broken up into these regions.
United States Forest Service Forest/Nonforest Map of Minnesota is from:
Metro
Prairie
USDA-Forest Service, Forest Inventory and Analysis survey units for Minnesota forests
USFS Forest / Nonforest Map of Minnesota

4. 2008 Residential Survey
6,600 questionnaires randomly sent to households within the 5 survey regions
April 2007 through - March 2008
1,434 households with complete responses
Minnesota Residential Fuelwood Assessment (2007/2008)
This provides a basic outline of the design of the 2008 survey, the latest completed survey.
The report is available online.

5. Survey Asked these Questions and More
Volume of wood harvested and burned
Equipment owned and used to burn
Fuel types (species, logs vs. pellets, shapes)
Geographic distribution of harvest and burning
Use for heat or pleasure
When the wood was burned
Primary residence vs. other burn locations
Sources of the wood and biomass
Minnesotans in each of those five regions are asked to fill out a survey to describe how they harvest and burn wood including: how much they burn, in which equipment, why they burn it, when they burn it, and where they burn it.
This slide lists some of the other information obtained from the survey. Over the years there have been some additional questions asked, though not all are included each time.
In recent years the fuel types have included wood, wood pellets, wax logs and other biomass (including corn kernels).
The next slides illustrate examples of the high level findings related to air quality.

6. Minnesota’s Residential Fuelwood Assessment (2007/2008)
Shows the amount of wood and biomass burned in different general types of equipment. The survey estimates that most of the wood in Minnesota is burned in wood stoves, hydronic heaters and backyard firepits.
Note that the recent surveys have also asked the respondents to distinguish EPA certified vs. the non certified models of wood stoves and fireplace inserts.
Minnesota’s Residential Fuelwood Assessment (2007/2008)

7. Minnesota’s Residential Fuelwood Assessment (2007/2008)
Although about half of the population lives in the Twin Cities Metro area, roughly similar amounts of wood (and biomass) are burned in each of the five survey regions. Note that the Metro region is a smaller area than the other regions.
This graph shows where the fuel was burned rather than where the respondent lives.
This includes wood, wood pellets, wax logs and the other biomass. Most of the corn kernels were burned in the Prairie region.
Minnesota’s Residential Fuelwood Assessment (2007/2008)

8. Minnesota’s Residential Fuelwood Assessment (2007/2008)
Statewide, about 30% of the households burn some wood. Of those who burn wood, about 70% of the wood burned is for heat (primary or secondary heat). Looking at the blue bars (which represent the total all 4 regions of Greater Minnesota (not the Metro area), this shows about ¾ of the wood burned in Greater Minnesota is burned for heat, with half of the total wood burned for primary heat.
Roughly a fifth of the wood is burned in the Metro area. But if you look at the red bars for the Metro area, unlike the pattern in Greater Minnesota (blue), about half of the wood used in the Metro is burned for pleasure and half for secondary heat. Little is used for primary heat. The Metro pleasure category reflects wood use in fireplaces and backyard “campfires” (e.g., fire rings, fire pits and chimeneas).
Note that the 2008 survey report identified an overall shift toward relatively more wood use for pleasure than had previously been the case. It was particularly pronounced in the Metro.
Minnesota’s Residential Fuelwood Assessment (2007/2008)

9. Estimated from Minnesota’s Residential Fuelwood Assessment (2007/2008)
This graph provides a simple illustration of how the amount of wood used in one year in each region would translate to the amount of wood smoke PM2.5 emissions across the area, if they were evenly dispersed across the whole region.
The five bars for the 5 Minnesota survey regions represent the total fine particle (PM2.5) emissions from the wood burned in all the residential wood burning equipment in the region, divided by the size (in acres) of that survey region. This is based on how much wood Minnesota residents reported burning in the different equipment, the equipment-specific emission factors, and the areas of the survey regions.
Based on this available information, the Metro region experienced higher average residential wood combustion PM2.5 emissions per area than the other regions.  
In the Metro, most of the wood was burned and emissions estimated from three categories of equipment: (1) recreational wood burning equipment (chimineas, firepits, fire rings, etc.), (2) wood stoves (and fireplace inserts), and (3) fireplaces.
In comparison, each of the Greater Minnesota regions, the overall emissions per area were lower. Wood stoves and hydronic heaters were the relatively more important sources of those PM2.5 emissions. Hydronic heaters are most used in the Northern Pine and Central Hardwoods region. Some of the wood burning in the Aspen-Pine region occurred when Metro residents traveled to and recreated in the Aspen-Pine area. Emissions from corn burning stoves primarily occurred in the Prairie region, but are not included on this graph.
Estimated from Minnesota’s Residential Fuelwood Assessment (2007/2008)

10. The blue line shows Minnesota’s historical record of the amount of wood burned by residents in Minnesota over time from the surveys conducted in Minnesota starting in 1960.
The red line is an indicator of the residential cost of onsite energy in Minnesota over the same time, using year 1970 = 1.
You can see the similarity in the curves, and that residential wood use has tracked with fuel costs.
After the earlier decline, we found a 50 % increase in residential wood use between the 2003 and 2008 surveys.

11. Minnesota’s 2012 Residential Fuelwood Use Survey
More engaging design and follow-up to increase the response rate
Minnesota’s Residential Fuelwood Use survey is ongoing for the 2011/2012 heating season. We are near completion of the data collection phase. Households were asked to report their wood use from July 2011 through June
This questionnaire was redesigned compared to previous survey forms. I want to thank those of you in the room who provided helpful suggestions, and we incorporated as many as we could.
One main goal of the new questionnaire design was to increase the response rate by having the survey look less daunting and more visually engaging. We hope the visuals will also increase the accuracy of the responses. We r ed the survey questionnaire to the households who hadn’t responded to the first mailing. We offered an online survey response option. North Central HPBA provided moisture meters that were offered in a drawing to increase participation.
We are still collecting responses to the second mailing,
Excerpts from survey by John Gulland

12. Conclusions Survey is valuable for air quality management
Improved emissions inventory
Develop reduction strategies – geographic basis
Minnesota survey found:
Regional differences in purpose
Larger average emissions per area in Metro
Collaboration has been positive and could be replicated in other regions