2. What is Municipal solid waste
3. Waste to waste technologies
4. Physical WTE systems
5. Thermal WTE systems
i) Incineration/WTE combustion
ii) Pyrolisis and Thermal gasification
iii) Plasma Arc Gasification
6. Biological WTE systems
In early days disposal of human and other wastes did not
pose any serious problems, since the population was small
and the amount of land available for accumulation of
waste was large.
Now the scenario has changed, due to rapid urbanization
and industrialization, which has resulted in tremendous
increase in the migration of public towards urbanized
As a result the waste management has now become a
major issue of concern today. 3
In the modern era, with the advancement of
technology, attempts are being made to
explore the potential recovery of energy from
the city’s Municipal Solid Waste.
Today a new generation of Waste-to-energy
technologies is emerging, which hold a
potential to create renewable energy from
waste matter including Municipal solid wastes,
industrial wastes and agricultural wastes.
What is Municipal Solid Waste(MSW)
MSW is an unavoidable by product of human activities.
It includes durable goods, non durable goods, containers and
packing, food wastes, cardboard, rubber, leather, textiles
wood, paper, glass, plastics etc.
It includes waste from residential ,commercial, and
institutional sources , e.g. schools, government offices etc
However they do not include all forms of solid wastes such as
construction and demolition debris, industrial process wastes
and sewage sludge.
Physical WTE technology mechanically process waste to
produce forms more suitable for use as fuel producing
refuse-derived fuel(RDF) or solid recovered
Thermal WTE technology use heat or combustion to treat
Biological WTE technologies use microbes and other
organisms to produce fuel from waste.
PHYSICAL WTE TECHNOLOGIES.
Waste is processed to produce RDF or SRF.
RDF is a fuel produced by treating it with
steam pressure in an autoclave. It consists of
inorganic materials such as plastics and
The MSW is first processed to remove glass, metals and other
materials that are not combustible (many of which can be
Autoclaving (treating with high pressure steam), kills viruses
and other pathogens, softens and flattens plastics, and
disintegrates paper and other fibrous materials.
The volume of wastes is reduced up to 60% and residual
material can then be compressed into pellets or bricks and
sold as solid fuel.
Burning RDF is more clean and efficient but expensive.
THERMAL WTE TECHNOLOGY
and Thermal Plasma Arc
Municipal Solid waste can be directly combusted
in WTE incinerators as fuel in a process known as
mass burn to produce electricity.
Heat from combustion process is used to turn water to
steam which powers a steam turbine generator
HOW IT WORKS
Incineration involves combustion of typically
unprepared (raw or residual) MSW
Sufficient quantity of oxygen is required for full
oxidation to take place.
Combustion temperature is around 8500C and the waste is
converted to CO2 and H2O
Any non combustible materials(metals, glass, stones)
remain as solid called Incinerator Bottom Ash(IBA),it
contains small amount of residual carbon.
It can however give rise to pollutants emissions in air. Air
emissions include acid gas particulate matter heavy
metals, highly toxic organic compounds and dioxins.
PYROLYSIS AND THERMAL GASIFICATION
Pyrolysis uses heat to break down organic materials
in the absence of oxygen,(the molecules break
down) producing a mixture of combustible gases.
Thermal gasification of waste, in contrast to
pyrolysis, takes place in the presence of limited
amounts of oxygen.
• The syngas
Products produced can be
• Thermal electricity heat
• Gaseous mixture
degradation of and fuel
MSW in the called
syngas(H2+CO) is production
oxygen • Low net green
• Biochar is a house
ranges from useful emissions & high
byproduct(used as conversion
fertilizer and for
Heating generation 18
Gasification is a process that chemically and physically
changes biomass through the addition of heat in
an oxygen-starved environment (partial
The end products of gasification include solids, ash and
slag, liquids and synthesis gas, or syngas.
HOW IT WORKS
into primary Secondary
chamber Syngas chamber has a
Has a primary
chamber produced burner(maintai
semi ns operating
and secondary Used as
chamber(exce feed stock
ss air for The combined
moisture and secondary
condition) volatile gases are
PLASMA ARC GASIFICATION
WHAT IS PLASMA
Fourth state of matter
Ionized gas at high temperature capable of
conducting electrical current.
Gasification is a waste This arc breaks down waste
trearment technology that
primarily into elemental
uses electrical energy
gas and solid waste
(slag) in a device called
by an electrical arc
Plasma-Arc Waste-to-Energy Gasification uses Plasma-
Arc-Torch to produce temperatures as high as 13000F.
This extreme heat breaks down wastes forming Syngas
(mixture of H2 & CO) and a rock like solid byproduct
called Slag (used in construction etc.)
Syngas can be converted into a variety of marketable fuels
including ethanol, natural gas(methane) and
Plasma converters could consume nearly any type
of waste including concrete steel and toxic chemicals but
the technology requires large energy inputs.
COMMERCIAL PLASMA TORCH
PLASMA TORCH IN OPERATION
BIOLOGICAL WTE TECHNOLOGY
Use microbes and other organisms to
produce fuel from waste.
Techniques used: a) Methane capture/Land fill
b) Biogas plants
METHANE CAPTURE/LAND FILL
Primary method of disposal of municipal solid
When left undisturbed the waste produces gaseous
by products containing CO2 and CH4 called
Landfill gas or Biogas
This happens due to Anaerobic (O2 free)
digestion of Organic matter
Landfill gas can be captured It consists of series of wells
drilled into the land fills and
via a Collection system
connected by Plastic
they are used directly in
The gas can be burnt directly
in a boiler as a heat Energy
source. If biogas is cleaned
engines or fuel cells or
by removing water vapor electricity generation
via gas turbines.
and SO2 then, 32
Wastes and various types of bacteria are placed in an air
tight container called digester
The biogas produced is either burnt directly in
boilers or cleaned and supplied as natural gas.
Fermentation uses yeast to generate liquid ethanol
from biomass wastes.
Waste to energy technologies can address two sets of
environmental issues :
a) Land use and pollution from landfills
b) problem of fossil fuels
How ever they can they an be expensive.
One of the primary objections against waste incineration is
that burning releases particulate matter and pollutants like
nitrogen oxides (NOx)
New technologies like Pyrolysis, Thermal incineration,
plasma arc gasification avoid the pollution concerns
around thermal incineration
However these technologies are expensive to install and
only some can be applied economically today.
1. Bryan . F. Staley and Morton . A . Barlaz, Composition of Municipal solid
Waste in US and the implications for carbon sequestration and methane
yield, Journal of environmental engineering, Vol:135 ,No:10 October 1,
2. By Lester B. Lave,1 Chris T. Hendrickson,2 Member, ASCE, Noellette M.
Conway-Schempf,3 and Francis C. Mc Michael, Municipal Solid Waste
recycling issues, Journal of Environmental Engineering, Vol . 125, No. 10,
October, 1999. ASCE,
1. 1) www.luxresearchinc.com
2. 2) www.altenergymag.com