New Emerging Technologies

							Overview of New and Emerging Technologies for Solid Waste
Management
This section presents an overview of new and emerging technologies for solid
waste management. The development of new and emerging technologies has
been driven by the need to find alternatives to landfilling and mass-burn
incineration. The City of Toronto is evaluating the potential to apply new and
emerging technologies to manage up to 40% of the City’s solid waste stream that
cannot be diverted through other means (see Figure 1). This remaining 40% of
the solid waste stream is referred to as residual waste.
The objective of this section is to describe the fundamental processes upon
which most current technologies are based and not to provide a comprehensive
listing of technologies. This section also introduces the concept of a waste
management system and describes the components of a system that includes a
new and emerging technology for residual waste processing.

New and emerging technologies includes a group of processes collectively
referred to as advanced thermal treatment technologies (ATT). These
technologies are of particular interest because of their relatively advanced stage
of development, their ability to derive energy from residual waste and their
generally low levels of emissions. ATT technologies are based on the following
thermal processes:

·   gasification;
·   pyrolysis;
·   plasma gasification; and,
·   depolymerization.
A brief description of each process is provided in the following paragraphs.
       Gasification
       The process of gasification is the thermal degradation of organic
       compounds, or otherwise referred to as carbonaceous materials, at high
       temperatures (900 - 1400 °C) in a low oxygen atmosphere, to produce a
       combustible gas, referred to as syngas, and an inert, possibly vitrified,
       solid residue.

       As defined by the Gasification Technologies Council (GTC)
       (www.gasification.org):

       ·   A process technology that is designed and operated for the purpose of
           producing synthesis gas (a commodity which can be used to produce
           fuels, chemicals, intermediate products or power) through the chemical
           conversion of carbonaceous materials.
·   A process that converts carbonaceous materials through a process
    involving partial oxidation of the feedstock in a reducing atmosphere in
    the presence of steam at temperatures sufficient to convert the
    feedstock to synthesis gas; to convert inorganic matter in the feedstock
    (when the feedstock is a solid or semi-solid) to a glassy solid material
    known as vitreous frit or slag; and to convert halogens into the
    corresponding acid halides.

·   A process that incorporates a modern, high temperature pressurized
    gasifier (which produces a raw synthesis gas) with auxiliary gas and
    water treatment systems to produce a refined product synthesis gas.


Pyrolysis
Pyrolysis is the thermal decomposition of organic materials at
temperatures in excess of 200oC in the complete absence of air. The
end product of pyrolysis is a mixture of solids (char), liquids (oxygenated
oils), and a combustible gas, or syngas, comprised of methane, carbon
monoxide, and carbon dioxide, with proportions determined by operating
temperature, pressure, oxygen content, and other conditions. Metals,
ceramics and other inert materials are not affected by the process.

Plasma Discharge Technology/Plasma Gasification
Plasma discharge uses extremely high temperatures in an oxygen-starved
environment to completely decompose input waste material into very
simple molecules in a process similar to pyrolysis. Products include
combustible gas and a vitrified solid residue.

The heat source is a plasma discharge torch, a device that produces a
very high temperature plasma gas. Plasma is an electrically neutral, highly
ionized gas composed of ions, electrons, and neutral particles. It is a
phase of matter distinct from solids, liquids, and normal gases. Plasma is
very common and is found in the sun, fire, fluorescent and neon lights. A
plasma gas is the hottest, sustainable heat source available and results in
a temperature profile of between 3,000 and 8,000 degrees Celsius.
Depolymerization
Depolymerization processes use high-energy microwaves in a nitrogen
atmosphere to decompose organic material. The waste absorbs
microwave energy increasing the internal energy of the organic material to
a level where chemical decomposition occurs on a molecular level. The
nitrogen blanket forms an inert, oxygen free environment to prevent
combustion. Temperatures in the chamber range between 150 to 350
degrees Celsius. At these temperatures, metal, ceramics and glass are
not chemically affected.
An ATT or other new and emerging technology for residual waste processing
would be a component of a waste management system designed to collect,
handle and process residual wastes and to manage all resulting products and
residues. The components of a simple residual waste management system are
presented in Figure 2.

Of particular interest when evaluating ATT or other new and emerging
technologies is the degree of pre-processing required to convert the residual
waste into a suitable feed material. Residual waste, as collected, is not suitable
for most ATT technologies because of its varying composition and size of some
of its constituent materials. Residual waste may also contain materials that are
undesirable because they either contribute to the quantity of solid residue,
jeopardize the process or cannot be captured by the emission control systems.

Typically pre-processing involves the physical operations of separation or sorting,
shredding or grinding, blending with other materials, drying and possibly
pelletization or a similar reformation process. The purpose of pre-processing is to
produce a feed material with consistent physical characteristics (size, shape,
moisture content) and chemical properties (energy content). A consistent input
material will minimize process upset conditions and will improve overall
performance. Pre-processing operations are also designed to produce a material
that can be safely handled, transported and stored, thereby allowing for
separation of pre-processing and processing operations.

Environmental control technologies must also be considered in this process. Any
new and emerging technology that is considered will need auxiliary equipment for
the control of any emissions or effluent resulting from the process. These
technologies will be put in place to comply with existing environmental
regulations. These systems could include bag filters for the removal of
particulate matter removal, scrubbers for the removal of impurities from air
stacks, odour control system, and effluent pre-processing.
                                                                  Figure 1
                                                Application of New & Emerging Technologies
                                                   for Solid Waste Management Services


                                                                    Municipal Solid Waste
                                                   60%                                                             40%


           New Policies & Practices                         Existing & Expected Diversion Programs                        New & Emerging Technologies
                     17%                                                 43% by 2006                                                40%


                                                                                 Recycling                                   Advanced Thermal Technologies



                                                                                     Fibres                                            Gasification

                                                                                  Containers                                             Pyrolysis

                                                                        Source Separated Organics                                   Plasma Gasification

                                                                                                                                     Depolymerization
                                                                                   Green Bin
                                                                                                                                  Physical Processing
                                                                               Commercial SSO

                                                                            Leaf & Yard Waste                                          Pelletization

                                                                            Envrionment Days                                      Mechanical Separation

                                                                              HSW Programs                                              Other?




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