22. Hazardous wastes must be deposited in secure industrial landfills, which
provide at least 3 metres (10 feet) of separation between the bottom of the
landfill and the underlying bedrock or groundwater table. A secure hazardous-
waste landfill must have two impermeable liners and leachate collection
30. Things to be practiced
• Source reduction: decreasing the amount and/or
toxicity of waste that must be disposed of by
producing less waste to begin with.
• Recycling & Reuse: Increasing recycling of
materials such as paper, glass, steel, plastic and
aluminum, thus recovering these materials rather
than discarding them.
• Providing safer disposal means by improving the
design and management of incinerators and
33. What are the main components of an engineered
An engineered landfill essentially consists of a barrier layer or
liner which is a low permeable zone to prevent the migration of
leachate from the landfill to the subsurface soil and water.
Above the liner, a drainage layer is placed which collects the
leachate from the waste for treatment. Such a layer also
minimizes the head causing flow in liner due to the timely
removal of leachate from the landfill.
The third important layer is the cover to the landfill, which is a
multi-layered system to cut off the release of landfill gases into
the atmosphere and at the same time to prevent the infiltration of
surface runoff into the waste. It also keeps away the scavengers
and rag pickers from entering the landfill.
• Pyrolysis is the thermochemical decomposition at high temperature (4500C to
8000C) and in the absence of oxygen or in an atmosphere of inert gases.
• Nowadays, pyrolysis is getting attention for its flexibility to generate a
combination of solid (char), liquid (bio oil) and gaseous (synthetic gas) products
in different proportions just by the variation of operating parameters such as
temperature or heating rate.
• It also provides an opportunity of transforming materials of low energy
density into bio-fuels of high-energy density, at the same time recovering high
• Diesel engines, gas turbines, steam turbines and boilers can be used directly to
generate electricity and heat in using syngas and pyrolysis oil. Syngas may also
be used as a basic chemical in petrochemical and refining industries. Char is
almost pure carbon and can be used in the manufacture of activated carbon for
water treatment applications or as an agricultural soil amendment.
• The fractions of MSW subjected to pyrolysis mainly consist of paper, cloth,
plastics, food waste and yard waste. The glass, metal and other inert fractions
• Types of reactors include bed reactors, rotary kilns, fluidized bed reactors,
plasma or solar reactors. Catalysts are also employed at times to make the
• Gasification of municipal wastes involves the reaction of
carbonaceous feedstock with an oxygen-containing reagent, usually
oxygen, air, steam or carbon dioxide, generally at temperatures
• The process is largely exothermic but some heat may be required to
initialise and sustain the gasification process.
• Produces syn-gas (synthetic gas/producer gas) consisting of CO2,
CO, H2 and CH4
• It is utilized as a gas fuel being combusted in conventional burner or
in a gas engine and then connected to a boiler and a steam turbine
or gas turbine to utilize the heat or produce electricity. Also, it can be
used as a building block for producing valuable products such as
chemicals and other forms of fuel energy
38. Other methods adopted for organic fractions in MSW
• Transformation of organic
matter into soil like
• Uses bacteria and fungi
• Entire process in the
presence of oxygen
• End product is compost,
by product is CO2, H2O
and little NH3
• Entire process in the absence
of oxygen in a closed chamber
• Uses anaerobic and facultative
• End product is biogas
(methane, CO2) and stabilized
nutrient rich organic matter
• Require sprinkling water,
nutrients to maintain
temperature, pH, nutrients,
moisture level required for
decomposition of organic
39. Refuse Derived Fuel
• RDF consists largely of combustible components of MSW,
such as non recyclable plastics, paper, cardboard and
materials recoverable calorific value.
• These fractions are separated from the rest of the MSW by
different processing steps, such as screening, separation of
ferrous and non ferrous materials, glass, stones and other
• These fractions are then air dried, shredded into a uniform
grain size, and pelletized by applying mechanical pressure in
order to produce a homogeneous material which can be used
as substitute for fossil fuels in e.g. cement plants, lime plants,
coal fired power plants.