The composition of Traeger pellets is determined by if they are manufactured from the West coast or East coast factories. Apparently pellets manufactured in the West coast are made with 100% Alder. Pellets manufactured in the East coast are made with 100% Oak.

Mesquite or Hickory pellets follow suite with their composition being determined by which coast they are manufactured in. No Mesquite or Hickory is actually used in the pellets. Instead the Mesquite and Hickory flavors come from oils that are added in the manufacturing process. West coast pellets are made with 100% Alder. East coast pellets are made with 100% Oak.

Apple, Pecan, and Cherry again are the same except this time only 70% of the pellet contains the base wood. The other 30% is actual Apple, Pecan, or Cherry wood.

Maple is composed of 100% Maple Wood.

Alder on the west coast is 100% Alder. On the east coast it’s 70% Oak and 30% Alder.

Oak on the east coast is 100% Oak. On the west coast it’s 70% Alder and 30 Oak.

Source: Team C - smokingmeatforums.com