vol2mass {biogas}

Calculate Mass of Biogas

Description

vol2mass calculates the mass of biogas removed from a reactor, based on its composition, temperature, and pressure. This function is the inverse of mass2vol.

Usage

vol2mass(volBg, xCH4, temp.hs, temp.vol, pres.hs, pres.vol, 
  unit.temp = getOption('unit.temp', 'C'), 
  unit.pres = getOption('unit.pres', 'atm'), 
  rh.hs = 1, rh.vol = 1)

Arguments

volBg

measured (not standardised) biogas volume in mL. Numeric vector.

xCH4

mole fraction of methane within biogas (dry, methane and carbon dioxide only). Numeric vector.

temp.hs

temperature of biogas just prior to removal, in the units specified in unit.temp (default of degrees C). Numeric vector.

temp.vol

temperature of biogas at the time of volume measurement, in the units specified in unit.temp (default of degrees C). Numeric vector.

pres.hs

pressure of biogas just prior to removal, in the units specified in unit.pres (default of atm). Identical to pres argument in mass2vol. Numeric vector.

pres.vol

pressure of gas at the time of measurement in atm by default (see unit.pres). Identical to pres argument of stdVol. Numeric vector.

unit.pres

pressure units. Options are "atm" (the default), "Pa", "kPa", "hPa", and "bar". Length-one character vector.

unit.temp

temperature units. Options are "C" (degrees Celcius, the default), "F", and "K". Length-one character vector.

rh.hs

relative humidity of the reactor headspace just prior to biogas removal. Length one numeric vector between zero and 1.0.

rh.vol

relative humidity of the biogas at the time of volume measurement. Length one numeric vector between zero and 1.0.

Details

This function is vectorized. Argument elements will be recycled as needed. Note that this function is conceptually but not numerically the inverse of mass2vol, because the volBg argument here is not standardised, and is assumed to be saturated with water vapor just prior to removal. The mass that is calculated may not be equal to the mass of the biogas at the time of volume measurement–as long as temp.vol is less than temp.hs, some of the water lost from the reactor condenses and is not present in the biogas at the time of volume measurement.

Standard values and units of temperature and pressure can be globally set using the function options.

Value

biogas mass in g as a numeric vector.

Author(s)

Sasha D. Hafner and Charlotte Rennuit

References

Hafner, S.D., Rennuit, C., Triolo, J.M., Richards, B.K. In review. A gravimetric method for measuring biogas production. Biomass and Bioenergy.

See Also

mass2vol, options

Examples

# Mass loss from reactor for 100 mL biogas measured at 20 degrees C 
# and 1.0 atm, with headspace at 1.5 atm and 35 degrees C at the 
# time of biogas exit
vol2mass(100, xCH4 = 0.65, temp.hs = 35, temp.vol = 20, 
         pres.hs = 1.5, pres.vol = 1)

# If the measured volume has already been standardised to dry 
# conditions at 0 C and 1 atm
vol2mass(100, xCH4 = 0.65, temp.hs = 35, temp.vol = 0, 
         pres.hs = 1.5, pres.vol = 1, rh.vol = 0)

# Here vol2mass *is* numerically the inverse of mass2vol
vol2mass(mass2vol(1.234, xCH4 = 0.65, temp = 35, pres = 1.5, 
                  value = "Bg"), 
         xCH4 = 0.65, temp.hs = 35, temp.vol = 0, pres.hs = 1.5, 
         pres.vol = 1, rh.vol = 0)