Replacing process water and nitrogen sources with biogas slurry during cellulosic ethanol production

Table 7 Analysis of the main costs and energy balance of corn-to-ethanol in this study

	Fresh water			Biogas slurry
	Amount	Costs (RMB)	Energy (kJ/kg)	Amount	Costs (RMB)	Energy (kJ/kg)
Main process inputs
Corn straw	1000 kg	300^a	16,350	1000 kg	300^a	16,350
NaOH	134 kg	335^b	148.91	134 kg	335^b	148.91
Process water	10 m³	30^c	42.0	0 m³	0	0
Biogas slurry	0 m³	0	0	10 m³	0	0
Nitrogen source	18 kg	180^d	753.48	0 kg	0	0
Total costs (RMB)	− 845			− 635
Total energy input (MJ/kg corn straw)			− 17.29			− 16.5
Main process outputs
Ethanol	95.2 kg	761.6^e		86.8 kg	694.4^e
Ethanol (Yuan/kg)		8.88			7.32
Net profit (Yuan)		− 83.4			59.4
Total energy output (MJ/kg corn straw)			2.83^f			2.58^f
Net energy value (MJ/kg corn straw)			− 14.46			− 13.92

^{a, b, c, d}The costs of corn straw, NaOH, process water, biogas slurry, and nitrogen source are calculated based on the fact of China
^eThe output of ethanol is calculated as 8.0 Yuan/kg
^fEnergy value based on lower heating value

ISSN: 2731-3654