Table 5.

Average values of higher and lower heating values and energy density of the reference and torrefied sludges.

Sludges	Temperature	Higher heating values (MJ kg−1)						Lower heating values (MJ kg−1)						Energy density (MJ kg−1)
		Time						Time						Time
		20′		40′		20′		40′		20′		40′		20′		40′		20′
PS	260 °C	17.5	Bc	17.6	Bc	17.9	Ac	15.3	Cc	15.8	Bc	16.4	Ac	2.53	Aa*	2.37	Bb	2.24	Cc
	290 °C	17.7	Cb	18.1	Bb	19.7	Ab	16.0	Cb	16.4	Bb	18.1	Ab	2.55	Aa*	2.41	Bb	2.55	Aa*
	320 °C	18.1	Ca	19.5	Ba	25.5	Aa	16.4	Ca	17.8	Ba	24.0	Aa	2.44	Bb	2.58	Aa*	2.48	Bb
	Reference	17.2						13.7						2.55
SS	260 °C	17.6	Ba	17.5	Bb	17.7	Ac	15.8	Cab	16.0	Bb	16.5	Ac	9.52	Ba	9.51	Bb	9.84	Ac
	290 °C	17.4	Cb	17.7	Ba	18.0	Ab	15.7	Cb	16.4	Ba	16.8	Ab	9.34	Ca	9.62	Ba	9.95	Ab
	320 °C	17.4	Cab	17.8	Ba	18.6	Aa	15.8	Ca	16.4	Ba	17.5	Aa	9.32	Ca	9.61	Ba	10.27	Aa
	Reference	17.2						13.8						8.15
MIX	260 °C	17.1	Cb	17.3	Bc	17.6	Ac	15.3	Cc	16.0	Bc	16.2	Ac	2.96	Bb*	3.09	Ac	2.95	Bc*
	290 °C	17.1	Cbc*	17.7	Bb	18.2	Ab	15.5	Cb	16.1	Bb	16.8	Ab	2.97	Cb	3.16	Bb	3.30	Aa
	320 °C	17.4	Ca	18.2	Ba	20.1	Aa	15.8	Ca	16.6	Ba	18.8	Aa	3.06	Ba	3.29	Aa	3.22	Ab
	Reference	17.0						13.4						2.93

Averages followed by the same capital letter between lines (time and properties) and lowercase between columns (temperature and sludge) do not differ, at 5% significance, by the Tukey test, for each type of sludge. *Do not differ from the reference, at 5% significance, by the Dunnet test, for each type of sludge.

PS—primary sludge, SS—secondary sludge, MIX—primary and secondary sludge.