3.2 Biochemical Conversion Technologies
81
as organic fertilizer [89]. Similarly, in San Martin, Peru, an AD project was executed
in a small, isolated community using two Trapezoidal lake type digesters to produce
between 8.74 and 11.65 m
3 of biogas per day.
Table 3.7 presents a selection of industrial applications of AD around the world.
3.2.2 Mechanical Biological Treatment
Mechanical biological treatment (MBT) is a type of waste processing in which the
waste is first mechanically separated to recover recyclables and then the organic
fraction of the waste is composted or digested through biological treatment. In fact,
the MBT plants are the integration of waste management facilities such as materials
recovery facilities (MRFs) and composting and anaerobic digestion plants. MBT
plants can process mixed household wastes as well as commercial and industrial
wastes. The main products of an MBT plant are recyclables such as polyethylene
terephthalate (PET) plastic that can be sent for recycling, the biologically stabilized
part as a low-quality soil that can be used for land reclamation, and RDF (Refused
Derived Fuel) that is used for incineration or cement kilns [90]. Figure 3.6 shows a
schematic diagram of an MBT process.
The waste usually needs some preparation before the mechanical or biological
treatments. Initial preparation may include removal of large and bulky wastes, size
reduction, homogenization, and breaking up or pulverization of the wastes. Mechanical separation includes a variety of techniques as a series or in combination. Some
of these techniques are as follows [91]:
– Trommels and screens for size reduction of papers, plastics, organics, glass and
fines.
– Manual separation and visual examination of plastics, contaminants and oversized
items.
– Magnetic separation of ferrous metals.
– Eddy current separation by electrical conductivity for non-ferrous metals.
– Wet separation technology by using differential densities for separation of plastics
and organics from stones and glass.
– Air classification for separation of light and heavy materials by weight.
– Ballistic separation for separation of light and heavy materials by density and
elasticity.
– Optical separation for specific plastic polymers.
The biological process may take place prior to or after the mechanical treatment,
and includes the following options [91]:
– Aerobic treatment or bio-drying/bio-stabilization for partial composting of the
whole waste.
– Aerobic treatment or in-vessel composting for bio-stabilization of the waste or
processing a segregate organic-rich fraction.
81
as organic fertilizer [89]. Similarly, in San Martin, Peru, an AD project was executed
in a small, isolated community using two Trapezoidal lake type digesters to produce
between 8.74 and 11.65 m
3 of biogas per day.
Table 3.7 presents a selection of industrial applications of AD around the world.
3.2.2 Mechanical Biological Treatment
Mechanical biological treatment (MBT) is a type of waste processing in which the
waste is first mechanically separated to recover recyclables and then the organic
fraction of the waste is composted or digested through biological treatment. In fact,
the MBT plants are the integration of waste management facilities such as materials
recovery facilities (MRFs) and composting and anaerobic digestion plants. MBT
plants can process mixed household wastes as well as commercial and industrial
wastes. The main products of an MBT plant are recyclables such as polyethylene
terephthalate (PET) plastic that can be sent for recycling, the biologically stabilized
part as a low-quality soil that can be used for land reclamation, and RDF (Refused
Derived Fuel) that is used for incineration or cement kilns [90]. Figure 3.6 shows a
schematic diagram of an MBT process.
The waste usually needs some preparation before the mechanical or biological
treatments. Initial preparation may include removal of large and bulky wastes, size
reduction, homogenization, and breaking up or pulverization of the wastes. Mechanical separation includes a variety of techniques as a series or in combination. Some
of these techniques are as follows [91]:
– Trommels and screens for size reduction of papers, plastics, organics, glass and
fines.
– Manual separation and visual examination of plastics, contaminants and oversized
items.
– Magnetic separation of ferrous metals.
– Eddy current separation by electrical conductivity for non-ferrous metals.
– Wet separation technology by using differential densities for separation of plastics
and organics from stones and glass.
– Air classification for separation of light and heavy materials by weight.
– Ballistic separation for separation of light and heavy materials by density and
elasticity.
– Optical separation for specific plastic polymers.
The biological process may take place prior to or after the mechanical treatment,
and includes the following options [91]:
– Aerobic treatment or bio-drying/bio-stabilization for partial composting of the
whole waste.
– Aerobic treatment or in-vessel composting for bio-stabilization of the waste or
processing a segregate organic-rich fraction.