Combined sodium hydroxide and ammonium hydroxide pretreatment of post-biogas digestion dairy manure fiber for cost effective cellulosic bioethanol production

Sustainable Chemical Processes

Table 3 Central composite experimental design and the corresponding pretreatment responses with subsequent enzyme saccharification of post-biogas digestion manure fibers

Independent variables			Dependent variables, Y
^a% NaOH and NH₃loading, gm/gm dry fiber, x₁	Temperature (°C), x₂	Residence time (min), x₃	Total sugar recovery%	Delignification% dry basis	Enzyme saccharification%
8.0	100	30	87.3 ± 0.0	22.9 ± 0.3	24.5 ± 0.8
12.0	80	5	87.4 ± 0.0	25.7 ± 1.3	19.9 ± 4.3
8.0	100	30	87.3 ± 0.0	22.9 ± 0.3	24.5 ± 0.8
12.0	121	5	87.5 ± 0.4	21.6 ± 1.1	23.9 ± 1.2
8.0	100	60	86.0 ± 0.4	26.3 ± 0.8	34.0 ± 1.2
4.0	121	5	94.6 ± 0.1	5.9 ± 0.9	2.5 ± 0.4
12.0	80	60	82.7 ± 0.6	32.8 ± 0.5	44.5 ± 1.0
8.0	100	5	91.5 ± 0.1	17.1 ± 0.2	16.2 ± 0.1
8.0	100	30	87.3 ± 0.0	22.9 ± 0.3	24.5 ± 0.8
12.0	100	30	79.4 ± 0.1	37.1 ± 0.3	36.5 ± 3.8
4.0	80	60	93.4 ± 0.1	12.2 ± 0.1	10.9 ± 0.1
8.0	121	30	80.2 ± 0.8	30.3 ± 1.0	49.0 ± 2.8
12.0	121	60	73.3 ± 0.4	44.3 ± 0.8	59.0 ± 0.5
8.0	100	30	87.3 ± 0.0	22.9 ± 0.3	24.5 ± 0.8
4.0	100	30	93.1 ± 0.1	10.0 ± 1.3	13.7 ± 0.4
4.0	121	60	88.3 ± 0.1	17.5 ± 1.3	27.5 ± 0.2
4.0	80	5	95.2 ± 0.1	11.1 ± 1.1	3.1 ± 0.2
8.0	80	30	89.5 ± 0.1	21.1 ± 0.0	24.8 ± 0.5
8.0	100	30	87.3 ± 0.0	22.9 ± 0.3	24.5 ± 0.8

^a Percentage of each NaOH and NH₃ added to the dry manure solids. Data are average of two replicates. Numbers with ± values represent standard errors.