2.2. Analytical methods
Proximate analysis was performed according to ASTM (D 3174,
1989; D 3302, 1989; D 338 , 1992). The samples were crushed
(Øb1 mm) and moisturewas determined at 105±5 °C. Ash yields were
determined using a muffle furnace at 550 °C for peat samples and
750 °C for lignite and subbituminous coal samples. Ultimate analysis
was conducted at the Instrumental Analysis Laboratory of the
University of Patras, using a CARLO ERBA EA1108 C–H–N–S analyzer,
standardized against the compost AgroMAT CP-1 (certified reference
material, SCP Science). Additionally, the pH values and the salt
contents dissolved in water solutions (as electrical conductivity, EC)
were determined.