Plug-flow hydrolysis with lignocellulosic residues: effect of hydraulic retention time and thin-sludge recirculation

Table 2 Dynamic operation conditions of the PFRs with 3 types of feedstock composition, variations of the HRT and thin-sludge recirculation

Substrate	HRT [d]	Recirculation	Total solids [%]	Period of operation^a [w]	Reference period [w]	Loss factor A
PFR1
Maize silage	Start-up	/	n.d	1–3	/	0.85
	7	/ 20%	8.2 (0.4)	9–11 12–14	11 14
	14	/ / 20%	10.6 (0.8)	4–8 15–16 27–30 16–26^b	6–8 16 28–30 /
			12.5 (0.3) /
30% straw, MS	14	20%	12.3 (0.2) /	31–35.5 36–46^b	33–35 /	0.75
66% straw, MS	14	20%	14.1 (0.2) /	47–54 55–69^b	53/54 /
66% straw, MS		10% 0%	13.5 (0.4)	70–74 75–78	73/74 77/78
PFR2
Maize silage	Start-up	/	n.d	1–4	/	0.85
Maize silage	14	/ 20%	12.7 (1.0) 14.4 (0.2)	5–8 9–13	7/8 12/13
Process in PFR2 stopped. Restart after repair
30% straw, MS	Fed-Batch	/	n.d	20	/	0.82
30% straw, MS	14 21	20%	10.7 (0.3) 11.1 (0.3)	21–26 27–32	25/26 31/32
66% straw, MS	21 14	20%	12.0 (0.8) 13.6 (0.5)	34–45 46–51	41–45 50/51	0.96

The data of the reference period are used to compare process efficiency between conditions
^aNot in chronological order, ^bBioaugmentation period, described in [38]

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