41

Recycling Programs

Container Laws – Required deposit on all reusable beverage

containers.• National bottle bill would reduce litter, save energy and

money, create jobs, and help conserve natural resources.

Mandatory Recycling Laws– Provide statutory incentive to recycle.

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Recycling Concerns

Plastics are recyclable, but technology differs from plastic to plastic.– Milk Container

• High-Density Polyethylene (HDPE)– Egg Container

• Polystyrene (PS)– Soft-Drink Bottle

• Poly-Ethylene Terephthalate (PET)• http://lifecycle.plasticsresource.com/

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Increasing Amounts of Plastic in Trash

Recycling Advantages

– public acceptance– resource

conservation Disadvantages

– not always economical

– environmental impacts

– cannot recycle everything

RecyclingRecycling Paper

– US recycles 50%– Many developed

countries are higherRecycling Glass

– US recycles 25%– Costs less than new glass– Can be used to make

glassphalt (right)

Recycling Recycling Aluminum

– Making new can from recycled one costs far less than making a brand new one

RecyclingRecycling Metals other

than Aluminum– Lead, gold, iron, steel,

silver and zinc– Metallic composition is

often unknown• Makes recycling difficult

Recycling Plastic– Less than 20% is recycled– Less expensive to make

from raw materials

Recycling

Recycling Tires– Few products are made from old tires

• Playground equipment• Trashcans• Garden hose• Carpet• Roofing materials

– 36% of tires are currently recycled to make other products

Integrated Waste Management

Tire Recycling 240 million

disposed/yr 3 billion stockpiledMany ways to

recycle– retread– playgrounds– fuel

Special Wastes - Electronic 20 million units in 1998,

11% recycled 50-80% of recycled sent

overseas 500 million units iby 2007 PC contains 2-4 lbs lead, 27-

in TV – 8 lb Cleanup costs > $1 billion

over 5 years Recycling may soon become

mandatory

Waste to EnergyAdvantages

– volume reduction– energy recovery

Disadvantages– public distrust– cost– difficult to operate– air pollutants

IncinerationVolume of solid

waste reduced by 90%Produces heat that

can make steam to generate electricity– Produce less carbon

emissions than fossil fuel power plants (right)

Incineration Types of Incinerators

– Mass burn (below)– Modular– Refuse-derived

Incinerator

Problems Associated with Incineration– Yields air pollution– Produce large amounts of ash– Site selection often controversial

Fly Ash Treatment

Module 10 66

Potential environmental concerns of stack gases

Particulates

Carbon dioxide, carbon monoxide

Acid gases (HCl, HF, SO2, NOx)

Heavy metals (Hg, Cd, Zn, Cu, Ni, As, Mn)

Products of incomplete combustion (PICs)

Module 10 67

Refused derived fuel (RDF)

Coarse RDF

Fluff RDF

Pelletised RDF

Module 10 68

Coarse RDF

Feed subjected to pulverisation

Removal of ferrous metal

Result in smaller particle size

More uniform fuel

Module 10 69

Pyrolysis Combustion in the absence of oxygen

Produces gaseous, liquid and solid fuels

Endothermic process requiring external heat source

Limited to processing specialist waste

Composting

Includes:– Food scraps– Sewage sludge– Agricultural manure– Yard waste

Reduces yard waste in landfillsCan be sold or distributed to community

Module 10 71

Managing composting at 3 levels At source through household education

Organic material separated at source requiring a separate collection system

Centrally separated by mechanical processing, requires a sophisticated processing infrastructure at transfer station

Module 10 72

Important composting criteria Bulk density increases from 0.35 to 0.6 t/m3 as organic

matter is reduced

Maintain free air space of 30 - 35% for aerobic activity

Size to maximise surface area and to permit air flow

Initial moisture 65% to 40% towards the process end

Temperature for exothermic process 50 - 70o C• to reduce pathogens, pests, seeds• controlled by air flow and material turning

Module 10 73

Important composting criteria (cont)

Carbon:nutrient (C:N) ratio of 30:1 - 15:1 for rapid aerobic growth

• High ratio is detrimental to plants and low ratio releases odour• Tendency for ratio to fall from fresh to mature compost

Final product pH should be about 7 - 8

Contaminants of concern are heavy metals

Pathogens - maintain and control high temperatures to maximise destruction of pathogens and minimise health risks

Compost turned with a frontend loader

Compost windrow. processing equipment in background