Organic Waste Recycling

102 Organic waste recycling: technology and management

Assuming organic amendments or bulking materials have been added to the
compost feed already, a mass balance on total wet solids is written as:

Xc + Xr = Xm (3.7)

For dry solids:

ScXc + SrXr= Sm Xm (3.8)

ScXc + Sr Xr = Sm(Xc+ Xr) (3.9)

Where:

Xc = total wet weight of compost feed produced per day

Xp = total wet weight of compost product produced per day

Xr = total wet weight of compost product recycled per day

Xm = total wet weight of mixed material entering the compost per

day

Figure 3.4 Schematic mass balance diagram for sludge composting showing inputs of
compost feed and compost recycle, and compost product (adapted from Haung 1979;
reproduced by permission of the Water Pollution Control Federation USA)

Sc = fractional solids content of compost feed

Sr = fractional solids content of compost product and compost

recycles

Sm = fraction solids content of mixture before composting

Vc = volatile solids content of compost feed, fraction of dry solids

Composting

process

Exhaust gases

Mixture

Xm, Sm

Compost

product

Xp, Sr

Air

Compost recycle Xr, Sc

Wet organic

substrate

Xc, Sc