Solid waste are non-liquid, non-soluble materials
ranging from municipal garbage to industrial waste
which contain complex and hazardous substances.
Population growth, Increasing urbanization,
Industrialization, and standard of living have
contributed to rise in both the amount and variety of
waste generated in most countries.
The technology of recovering energy from solid waste
will play a significant role in mitigating issues relating
to waste and will also result in reduction of overall
quantity of waste.
9. WASTE AS A RENEWABLE
SOURCE OF ENERGY
The enormous increase in the quantity of
waste materials generated by human activity and
their potential harmful effects on the general
environment and public health, have led to an
increasing awareness about an urgent need to
adopt scientific methods for safe disposal of
11. WASTE-TO-ENERGY CONVERSION PATHWAYS
Various technologies are available for realizing the
potential of waste as an energy source, ranging from
very simple systems for disposing of dry waste to more
complex technologies capable of dealing with large
amounts of industrial waste.
There are three main pathways for conversion of
organic waste material to energy – thermo chemical,
biochemical and physicochemical.
13. Thermochemical conversion
It is characterized by higher temperatures
and faster conversion rates.
Best suited for lower moisture feedstock.
Thermochemical routes can convert the
entire organic (carbon) portion of suitable
feedstock to energy.
Inorganic fraction (ash) of a feedstock does
not contribute to the energy products but
may increase nutrient loading in wastewater
treatment and disposal facilities.
15. Waste Incineration
• The incineration technology is the controlled
combustion of waste with the recovery of heat to
produce steam which in turn produces power
through steam turbines.
• Volume and weight reduced.
• Incineration can be done at generation site .
• Air discharges can be controlled and small disposal
Partial oxidation process, pure oxygen,
oxygen enriched air, hydrogen, or steam.
Produces electricity, fuels (methane,
hydrogen, ethanol, synthetic diesel), and
Temperature > 700oC.
More flexible than incineration, more
technologically complex than incineration or
pyrolysis, more public acceptance.
Thermal degradation of carbonaceous materials.
Lower temperature than gasification (400 – 700oC)
Absence or limited amount of oxygen.
Products are pyrolitic oils and gas, solid char.
Distribution of products depends on temperature
Pyrolysis oil is used for (after appropriate post-
treatment) liquid fuels, chemicals, adhesives, and
A number of processes directly combust pyrolysis
gases, oils, and char.
18. Biochemical conversion
It include …
Anaerobic digestion (occurs in controlled reactors
or digesters and also in a less controlled
environment in landfills)
Anaerobic fermentation (for example, the
conversion of sugars from cellulose to ethanol)
Biochemical conversion proceeds at lower
temperatures and lower reaction rates than other
19. Physicochemical conversion
It include …
Transesterification (biodiesel production)
Physical and chemical synthesis of products from
The combustible fraction of the waste is converted
into high-energy fuel pellets which may be used in
Fuel pellets have several distinct advantages over
coal and wood because it is cleaner, free from
incombustibles, has lower ash and moisture
contents, is of uniform size, cost-effective, and eco-
20. Majority of waste that goes into landfills can be reused.
Always a reliable source of fuel as people will always have waste.
The fuel is obtained cheaply.
21. Public is not convinced that Waste to Energy facilities are clean
and free of harmful chemicals.
Waste to Energy facilities are expensive to construct.
Air Pollution from combustion process.
Possibility of toxic ash as a byproduct and it may leach into
groundwater and make it impure.
22. Waste-to-energy plants offer benefits of
environmentally safe waste management
and disposal, as well as the generation of
clean electric power.
Waste-to-energy facilities produce clean,
renewable energy through thermo chemical,
biochemical and physicochemical methods.