MEMORANDUM
DATE:		February 20, 2013
SUBJECT:  	European Wood Heating Technology Survey Explanation of Data for Solid Wood Stoves and Boilers
FROM:	Alden West, EC/R Inc.
		Glenn Meganck, EC/R Inc.
TO: 		Gil Wood, EPA/OAQPS
      David Cole, EPA/OAQPS

The Excel(TM) spreadsheet (included as an attachment in this e-mail) provides data for solid wood stoves and boilers from the European Wood-Heating Technology Survey (EWHTS). Both the stoves and boilers tables are provided in the format presented in the EWHTS and as a "sortable" table.  A PM emission rate in grams per hour (g/hr) was calculated by multiplying the nominal load (MBtu/hr  -  converted to MMBtu/hr) by the TSP emissions (lb/MMBTU  -  converted to g/MMBTU).   
The data in the European Wood-Heating Technology Survey are useful for development of the Residential Wood Heaters NSPS although not all of the data are directly comparable to some of the data previously compiled for the NSPS. Some differences should be kept in mind:  (1) The EWHTS provides emissions data as "dust" or "total suspended particulate (TSP)," which is defined as particles with a diameter of 45 micrometers (um) or less, while the NSPS data is provided as particulate matter (PM), defined as particles with a diameter less than either 10 um (PM10) or 2.5 um (PM2.5). Both measures need clarification; the EWTHS test method does not use a dilution tunnel and thus the EWHTS "dust" does not include the condensibles [products of incomplete combustion] that would be measured by EPA Method 28. This difference is believed to be very small for the higher combustion efficiency heaters that have less products of incomplete combustion. Although neither the EWHTS test methods nor EPA Method 28 distinguishes between TSP and PM10 and PM2.5, studies have shown that over 85% of residential wood smoke emissions are PM2.5 or less. (2) The EWHTS provides data for European solid wood boilers, which often are low-pressurized systems whereas many current U.S. hydronic heaters are not pressurized.         (3) The EWHTS provides data on stoves that burn wood in Austria, Denmark, Germany, Norway and Sweden; some of the tree species in these countries are different than those in the United States and therefore may have somewhat different emission characteristics when burned.  (4) The EWHTS characterizes wood heaters based on "nominal load" (MBtu/hr).  Although nominal load is believed to be similar to the "maximum capacity" as defined by NSPS Burn Rate Category 4, both EPA Method 28 and EN303-05 currently allow the manufacturers to specify the rated output capacity goal for the tests. This may not be a significant difference since most manufacturers use the highest value the heater can achieve for the durations specified in the owner's manual.  
It should also be noted that the EWHTS ranked the top performing wood stoves based on the efficiency of the stove and CO emissions (as an indicator of combustion quality), whereas the top performers in the NSPS data are currently ranked solely based on PM emissions (grams per hour).  Therefore, if wood stoves in the EWHTS data have low PM emissions they may still be excluded from the EWHTS "top performers" if they are inefficient or generate high CO emissions from incomplete combustion. Also, it should be noted that forced-air furnaces are not included in the EWHTS because European manufacturers and consumers consider forced-air furnaces to be an inferior technology/system compared to the other systems that can perform better.
Also, note that the efficiencies in the EWHTS tables are for gross combustion values, i.e., using the high heating value of the wood burned rather than the net combustion values, i.e., using lower heating value of the wood as typically advertised in Europe. The NSPS is expected to require testing and reporting of the gross values.
