4.4.3 Sizing of gasholder

The purpose of this chapter is to offer guidance on how to size the gas holder and what information is required.

Parameter	Value	Unit	Source
Biogas consumption of the lamp	100	L/h	Manufacturer
Operation of biogas lamp	8	hours	Defined by the project
Number of biogas lamps	9	pieces	Calculated in the previous exercise
Inflow quantity per person	6.2	L/user/day	Water usage survey: 5L/cap/day for cleansing and flushing. Estimated excreta generation rate: 1.2L/cap/day (Urine 0.9L/cap/day, Faeces: 0.3L/cap/day)
TS	13,000	mg/L	Characterisation study
VS	9,200	mg/L	Characterisation study
COD	21,200	mg/L	Characterisation study
C:N	5:1		Literature values
Specific biogas production (Median)	0.23	m3/kgVS	Characterisation study
Organic Loading rate	0.75	kgVS/m3/day	Literature values

The size of the gasholder is determined by the biogas generation and consumption rates. It must be designed to ensure adequate coverage during peak consumption and to retain the gas generated during long periods of no consumption.

The required volume of the gasholder to cover the peak biogas consumption over the day is calculated by multiplying the maximum biogas consumption rate by the duration of the longest zero-consumption period.

Where,

Parameter	Description	Unit
VP	Biogas Volume to cover during the peak consumption	m3
C MAX	Maximum biogas consumption rate per hour	m3/h
tMAX	Duration of the longest zero-consumption period	h

Where,

Parameter	Description	Unit
C MAX	Maximum biogas consumption rate per hour	m3/h
NED	Number of end devices	–
CED	Biogas consumption rate for end device	m3/h

In addition, it is necessary to determine the amount of biogas that needs to be stored for the longest period of zero usage. To achieve this, we must first calculate the production rate per hour. This can be done by dividing the daily production rate by 24 hours. We then multiply the hourly production rate by the duration of the unused period.

Where,

Parameter	Description	Unit
VZERO	Biogas Volume generated during the longest period of zero consumption	m3
QGAS	Biogas Production Rate	m3/d
tZERO	Maximum zero consumption time	h/d

The larger volume determines the size of the gasholder. In our case, 7.2m³.

Some guidelines suggest a safety margin of 10- 20%, resulting in 7.9 – 8.6m³.