(1) seasoned clean wood;

(2) wood pellets made from clean wood;

(3) heating oil in compliance with Subpart 225-1 of this Title, L.P. gas or natural gas may be used as starter fuels for dual fuel-fired outdoor wood boilers;

(4) non-glossy, non-colored papers, including newspaper, may be used only to start an outdoor wood boiler; and

(5) other fuels approved by the department per the certification requirements of section 247.8 of this Part.