ENGG1006 - Engineering for Sustainable Development
RESOURCE AND WASTE MANAGEMENTDr. Kaimin ShihDEPARTMENT OF CIVIL
ENGINEERING THE UNIVERSITY OF HONG KONG
Office: Rm. 5-26, Haking Wong Building Phone: 2859-1973 E-mail:
[email protected]
PROGRESS & OUTCOMES
1
Resource Consumption and Prediction
Sustainable Development is: A pattern of resource use that aims
to meet human needs without compromising the ability of future
generations to meet their own needs. Resource: A source of supply
or support
.
Natural Resources
Renewable ResourcesCan be reproduced easily, such as sunlight,
wind, crops, fish,
Non-Renewable Resources NonFormed over very long geological
time, such as oil, coal, minerals,
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Accumulative Discovery and Extraction of Copper
Growth of Global Metal Extraction Rates
E = E0e-ktCurrent extraction rate Initial extraction rate
Current time
Growth of extraction rate
td is the doubling time, when E = 2E0.
3
4.2 billion tons/year !
World Reserve: 900 billion tons Constant consumption rate (7
billion tons/year) 132 years Current k = 2.5% 56 yearsCountry China
USA India Australia Russia S. Africa Germany Reserve (Billion tons)
114 247 92 79 157 49 6.7 5.0 14 Production (Billion tons/year) 2.38
1.05 0.45 0.37 0.30 0.26 0.20 0.20 0.16 Reserve Life* (Years) 48
235 204 214 523 188 34 25 88
Global Coal Use
Indonesia Poland
* Not considering the growth of production rate.
World Oil ConsumptionIn 1000 barrels per dayTransportation is
the largest sector (55% worldwide and 69% in US) and is also the
sector with largest growth in recent decades Growth in demand:
average 1.76% from 1994-2006
4
World Energy Consumption
Energy Crossroads: A Burning Need to Change Course
(2007)[2:35]
As fossil fuels power every facet of our economy, how can we
avoid an energy crisis and a possible collapse of our economy? This
documentary exposes the problems associated with our energy
consumption, and features experts and scientists at the forefront
of their field bringing legitimacy and expertise to the core
message of the piece.
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Reserves vs. Resources
Not recoverable under present technology & economic
conditions
Oil Depletion Prediction In 1970, reserves = 550 billion barrels
& production = 17 billion barrels per year, should be depleted
in 32 years. Well, we are surely still producing oil TODAY ! In
2005, reserves = 1300 billion barrels & production = 30.7
billion barrels per year, depletion in another 42 years !
A do they have is common? What sense of the futurein essentialin
influencing many decisions we make today
Johann Adam Schall von Bell
6
A local power generation facility: Predict the local population
growth rate over next decays A local ecosystem: Predict the growth
rate of an endangered species Scientist and policy maker: Estimate
deforestation & reforestation rates due to global warming
We cannot expect to make accurate predictions of the future.
But, we can use simple mathematic models to develop very useful
what if scenarios.
Symmetrical Curve for Resource PredictionAssume resource cycle
by M. King Hubbert (1969): Begin with exponential growth of
production when the resource is relative abundant and cheap
Eventually the high price, due to depletion and likely substitutes,
will decline the production precipitously back to close to zero.
This production rate cycle resembles a symmetrical and bell-shaped
curve, same as the normal (or Gaussian) function used in
probability theory.
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Normal (or Gaussian) Distribution
P Pm tm Will be 95% if within 2
= production rate = maximum production rate = time when Pm
occurs = standard deviation
exp {} = exponential function
* This part is not within our course learning outcomes.
P = Pm exp { (-1/2) [(t tm) / ]2 }
Management of World Oil ProductionTwo possible scenarios (based
on 2000 billion barrels in total): Gaussian curve by historical
production record: Oil production will peak just before year 2000
Enforce conservation policy: Supplies will last until year 2040
before the decline
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Generation of Waste
All creatures, humans included, constantly make decisions about
what to use and what to throw away
Extract energy from C-C & C-H bonds
Chimpanzee & banana
Paramecium & organic molecules You and your soft drink
Waste is a consequence of material consumption.
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Material ConsumptionFunction of solid materials in society Food
Energy (fossil fuels) Buildings and construction Consumer goods,
capital goods (machinery, transport equipment)
Life time (retention) of goods Long life: years, e.g.
appliances, structures (durables, capital goods) Medium life:
weeks, months, e.g. newspaper, shoes, clothes Short life: days,
e.g. food, packaging (non-durables, consumer goods)(now - ?)
(1937- )
Definition of Solid WasteSolid waste is any solid material
rejected by society because it is unwanted or useless.
It has a significant angle of repose.
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Solid Waste in HistoryWhen humans abandoned nomadic life ~10,000
BC, they began to live in communities, resulting in the production
of solid waste. The Indus Valley civilization (started ~6000BC):The
city of Harappa (3300-2000BC): had toilets and drains. The city of
Mohenjo-daro (2600 -1900BC) had houses with rubbish chutes and
probably collection systems.
By 2100BC, cities on the Island of Crete had trunk sewers
connecting homes. Sanitary Laws written by Moses in 1600BC By
800BC, Old Jerusalem had sewers and a primitive water supply. By
200BC (Han Dynasty), cities in China had Sanitary Police to enforce
waste disposal laws.
In Athens in 500BC, a law was passed to require all waste to be
deposited more than 1 mile away from the town
1 mile
away
A T H E N S
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A T H E N S
A T H E N S
But for the most part people in cities lived among waste and
squalor. Only when the social discards became dangerous for defense
was action taken
In Athens in 500BC, a law was passed to require all waste to be
deposited more than 1 mile away from the town. Because the piled
rubbish next to city walls helped invaders to scale up and over the
walls Rome had similar problem and eventually developed a waste
collection program in 1400AD. Cities in the Middle Ages in Europe
unimaginable filth (animals roamed the streets; wastewater dumped
out windows,..). As a result, the Black Death in 1300AD reduced
cities population and alleviate waste problem until mid-1800s.
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England during Industrial Revolution:Working poor (on average
one toilet per 200 people in Manchester). Great Sanitary Awakening
(1840s) spearheaded by a lawyer Edwin Chadwick, who argued
connection between disease and filth. Physician John Snow stop
cholera epidemic (1854) by removing pump handle on Board Street in
London.
Charles Dickens (1812-70)
Sir Edwin Chadwick (1800-90)
Dr. John Snow (1813-58)
In 1676, Antonie van Leeuwenhoek, a Dutch Microscopist who was
the first person to observe bacteria using a microscope, and
published his findings in letters to Royal Society of London after
1684. (later commonly known as the Father ofMicrobiology)Antonie
van Leeuwenhoek (16321723), the first microbiologist
Identification of disease-causing bacteria of Bacillus anthracis
(1877), Tuberculosis bacillus (1882) and Vibrio cholera (1883). In
1881, he urged the sterilization of surgical instruments using
heat. (Nobel Prize in Medicine in 1905 due tothe finding of
tuberculosis bacillus )Robert Koch (1843-1910), a German
physician
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Solid Waste Engineering and Management
Main Engineering ProcessesCollection Volume Reduction Separation
(Sorting) Recycling Composting & Digestion Thermal Treatment
Final Disposal (Landfill)
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CollectionWaste Management, Inc. A waste management and
environmental services company in North America - The largest
trucking fleet in the waste industry (22,000 collection/transfer
vehicles) - 413 collection operations (network systems), 370
transfer stations, 283 active landfill disposal sites, 17
waste-to-energy plants, 131 recycling plants, 95 beneficial-use
landfill gas projects and 6 independent power production plants. -
Serving nearly 21 million residential, industrial, municipal and
commercial customers
Employees: ~50,000 Revenue (2006): $13.36 billion USD
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Simple Routing Cost AnalysisSolid waste generation,
transportation and disposal costs are:
A 1 2
Source Generation (tons/wk) 1 100 2 150 Disposal Site A B
Transportation Cost ($/ton) Site A Site B 5 12 7 5 Cost($/ton) 4
5
Capacity (tons/wk) 50 200
Assume depose X tons of from source 1 to A per week. Assume
depose Y tons of from source 2 to A per week.What is the objective
function for minimizing disposal cost?
B
[5X+12(100-X)+4X+5(100-X)]+[7Y+5(150-Y)+4Y+5(150-Y)]min =
(3200-8X+Y) min ------ cost of source 1 --------- cost of source 2
---Constraints: X+Y =50 Solved Results: X=50, Y=0. Objective
function minimized to $2800/wk Decision: Source 1 - Dispose 50
tons/wk to Site A; 50 tons/wk to Site B Source 2 - Dispose 150
tons/wk to Site B Minimized Total Disposal Cost will be
$2800/wk
Routing Cost Analysis8 transportation costs (xijcij), 2 disposal
rates (Fi). Minimize objective function:[x11c11+ x21c21+ x31c31+
x41c41+ x12c12+ x22c22+ x32c32+ x42c42+ F1(x11+ x21+ x31+ x41)+
F2(x12+ x22+ x32+ x42)] Subject to the following constraints (site
capacity, Bi, and source amount, Wi): x11+ x21+ x31+ x41 B1 x12+
x22+ x32+ x42 B2 x11+ x21+ x31+ x41 = W1 x12+ x22+ x32+ x42 =
W2
A 1 2
3
4
xij 0* This part is not within our course learning outcomes.
B
The equations can be solved using any linear programming
algorithm. The transportation algorithm is particularly useful for
such applications.
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Volume Reduction (at Refuse Transfer Station)Into compactor and
compacted
Refuse conveyed by live floor system
Compacted refuse
Container with compacted refuse
(HKEPD, 2005)
Terminology Bulk density: Solids + Water + Porosity (air)
Compactible, noncompactible waste fraction Density before and after
compaction Compaction decreases: - Vp - some Ww, VwWaterVw, Ww Dw=
Ww / Vw 1000kg/m3
Solids
V s, Ws D s= Ws / V s
Porosity
V p , Wp ( 0 ) D p = Wp / V p ( 0 )
Bulk volume (Vbulk) = Vw + Vs + Vp Bulk weight (Wbulk) = Ww + Ws
+ Wp Ww + Ws Bulk density (Dbulk) = Wbulk / Vbulk = (Ww + Ws) / (Vw
+ Vs + Vp )
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Separation (Sorting)
Recyclable paper separation
Recyclable electronics separation (from plastic waste)
Recyclables separation at landfill
Trommel screens can sort multiple sizes, and are excellent
primary screens for commingled waste. Robust, no wear parts, but
requiring more floor space.
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Horizontal Air Knife
FEEDConveyor
r Ai
Light(e.g. plastic, paper)
Medium(e.g. aluminum)
Heavy(e.g. glass, stone)
Fan
Recycling Waste Hierarchy The waste hierarchy refers to the 4
Rs" waste management strategies in order of importance : -
Reduction - Reuse - Recycling - Recovery
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Reduction Example: Pay As You Throw (PAYT)USEPA (1920~,
1993~)
A usage pricing model for disposing of waste, sometimes referred
to as unit pricing or variable rate pricing. Users pay a variable
rate based on how much waste for collection Recyclable waste is
usually collected free of charge Implementation models: containers,
binbags, waste stickers, prepaid packaging (refunded &
non-refunded)
Pros: Incentive for waste reduction / recycling
Cons: Encourage illegal disposal
Example: Process of Paper recycling
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Metal (aluminium, steel) cans recycling Steel (iron, tin)-
Recycling by magnetic separation and melting - Can accept both
steel or aluminium cans (due to magnetic separation process) - Save
energy (m.p. of metal: 1538oC; of oxide ore: 1565-1600oC)
Aluminium- Recycling by shredded into pieces and melted - Accept
only aluminium can - Save significant energy (m.p. of metal: 660oC;
of oxide ore: ~900oC)
~~ Both Without "Downgrading" Quality ~~
Composting & DigestionPurposes: Reduction and stabilisation
of (biodegradable) organic matter by biochemical processes to
soil-like matters or gases.
Aerobic process (composting):[Complex Organics] + O2 CO2 + H2O +
NO3- + SO4-2 + stabilized products* + heat
Anaerobic process (digestion):[Complex Organics] + heat CO2 +
CH4 + H2S + NH4+
* Can be used for fertilizer.
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Sha Ling Livestock Waste Composting Plant (SLCP)
1
Collect livestock waste from leak proof bins (provided)
Shredded wooden pallets as bulking agents
Mixing of wooden pallets and waste (Height: ~2.5m)
2
Compost at fermentation boxes (blowing air, ~ 6-8 weeks) (HKEPD,
2005)
Compost at Maturation Shed
The DRANCO (Anaerobic Digestion) Process Owner: Organic Waste
Systems (Belgium) Digester loading: 10 to 20 kg carbon/m-reactor
per day Temperature range: - Thermophilic: 48 - 57C - Mesophilic:
35 - 40C Retention time in the digester: 15 to 30 days Biogas
production: 100 to 200 Nm of biogas per ton of waste* Electricity
production: 220 to 440 kWh per ton of waste* N means normal
temperature (20oC) and pressure (1 atm) condition.
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Sewage sludge decomposed in 35oC anaerobic digester at Glenwood
Springs, Colorado (USA) . The digester is heated by methane, one of
the bi-products of anaerobic digester. UC Davis (California, USA)
experimental anaerobic digester processes 8 tons of food scraps
weekly for energy
Thermal Treatment
(HKEPD, A policy framework for the management of municipal solid
waste (2005-2014), 2005)
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Moving Grate Incinerator
Moving Grate System
Stoichiometry (simplified for combustibles)Ca(H2O)mHbClcFdSeNf +
[ a + b/4 - (c+d)/2 + e + f/2 ] O2
a CO2 + [ (b-c-d)/2 + m ] H2O + c HCl + d HF + e SO2 + f NO
Note:- HCl, HF, SO2, and NO are air pollutants - Combustion may
be incomplete - Additional reactions may take place,
volatilization, dust formation, etc.
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Dioxin A combination of many members of an organic compound
family Polychlorinated Dibezodioxins (PCDDs). Dioxin occurs as an
contaminant in organic (chlorinated) chemicals or a byproduct of
combustion. Major emission source in US (1994): Hospital waste
combustion (55.4%) and Municipal waste combustion (32.6%). The
formation mechanism from combustion is uncertain so far. Used to be
assumed by burning chlorinated plastics, recombination formation in
cooled flue gas etc., but also with many negative evidences.
Extremely toxic to animals, but questionable as expected to humans.
Direct measurement in operation is difficult. Hasselriis (1987)
proposed: PCDDs = (CO / A)2 , where CO is carbon monoxide and A is
a constant subject to operation system.(particularly toxic)
Parent compound of dibenzo-p(or 1,4)-dioxin
2,3,7,8- tetrachlorodibenzo-p-dioxin * Now mostly removed by
flue gas filter bag (adsorption) or adsorber columns
Final Disposal (Landfill)
Final disposal at..... Where?[Result]: Not economical
In 1970s, USEPA did feasibility studies of sending wastes
to:[Result]: Eventually will come back to earth surface
Two reminding locations: Large bodies of water, such as oceans
On or in land
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Landfill in operation
(1) Collection vehicle is weighed at weighbridge on arrival
(2) On the way to the tipping face (3) Waste truck unloads at
the tipping face
(5) Vehicle is weighed at weighbridge on departure
(4) Vehicle passes the vehiclewash system after unloading
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Reactor Landfill Feathers Biological and chemical reactions -
Anaerobic reactions with gas production - Leachate production
causing possible contamination of atmosphere, soil, and groundwater
Mass and water balances for prediction of mass/volume changes and
leachate generation Velocity and duration of reactions difficult to
predict over long-term
Gas generated in landfillTypical constituents of MSW landfill
gas Component Methane Carbon dioxide Nitrogen Oxygen Ammonia
Hydrogen % by volume 45 - 60 40 - 60 2-5 0.1 - 1.0 0.1 - 1.0 0 -
0.2G a s p ro d u c e d (1 0 6 m 3 )
North East New Territories (NENT) Landfill, Hong Kong4.5 4.0 3.5
3.0 2.5 2.0 1.5 1.0 0.5 0.0 1 3 5 7 9 11 13 15 17 19 21 Year since
opened
Landfill gas production vs. time
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Ranges of parameters in leachateParameterBOD (mg/L) COD (mg/L)
Iron (mg/L) Ammonia (mg/L) Chloride (mg/L) Zinc (mg/L) Total P
(mg/L) pH Lead (mg/L) Cadmium (mg/L)
Ehrig 198920-40000 500-60000 3-2100 30-3000 100-5000 0.03-120
0.1-30 4.5-9 0.008-1.020