Sustainable Management of Fly Ashes from Waste Incineration
Florian HuberResearch Center of Waste and Resource ManagementCD Laboratory for Anthropogenic Resources
Symposium: Science to support Circular Economy19.09.2018, Vienna
Sustainable Management of Fly Ashes from Waste Incineration 2
Introduction
Status quo
• About 3% of the waste input in waste incineration plants arise as flyash, which constitutes a hazardous waste
• Mass of fly ash generated in Europe: 900,000 t/a
• Fly ash mass from grate furnaces in Vienna: 18,000 t/a
→Exceeds limits for Hg total content, Pb and TDS leachate content
Morf, L.S., Brunner, P.H., Spaun, S., 2000. Effect of operating conditions and input variations on the partitioning of metals in a municipal solid waste incinerator. Waste Management and Research 18, 4–15.
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Introduction
• Stabilisation with cement• Underground deposits• Extraction procedures• Thermal treatment• Neutralisation with waste acid• Utilisation in cement production
Assess the performance of management options with regard to thegoals of waste management
MSWI fly ash management options
Aim of the study
Sustainable Management of Fly Ashes from Waste Incineration 4
Environmental assessment
Sustainable Management of Fly Ashes from Waste Incineration 5
Environmental assessment
Scenarios
• Establishment of different MSWI fly ash management scenariosScenario 1 Underground depositScenario 2a Stabilisation with 1 Mg cement/Mg fly ashScenario 2b Stabilisation with 0.3 Mg cement/Mg fly ashScenario 3a Metal recoveryScenario 3b Metal and salt recoveryScenario 4a Thermal treatment in coal-fired furnaceScenario 4b Thermal treatment in natural gas-fired furnaceScenario 5a Thermal co-treatment with combustible waste in a rotary kiln incineratorScenario 5b Thermal co-treatment with combustible waste in a grate furnace incineratorScenario 6a Utilisation of fly ash in cement productionScenario 6b Utilisation of fly ash in cement production with salt recovery
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Environmental assessment
Methodology
• Life Cycle Assessment to estimate environmental impact• Functional unit: treatment and disposal of 1 t of MSWI fly ash• Material flow analysis conducted to determine input and output flows• Average transfer coefficients for heavy metals from fly ash to
products and residues calculated from experimental and literature data
• Life cycle inventory data from the ecoinvent database for all processes
• Life cycle impact assessment according to ReCiPe method• System expansion to account for co-products
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Environmental assessment
Uncertainty analysis
• Determination of the uncertainty of every parameter (literature data, experiments, expert judgement)
• Propagation of uncertainty by Monte Carlo simulation (100.000 runs)
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Environmental assessment
Consideration of long-term emissions
• Heavy metals can leave above ground landfills via the leachate• Assumptions:
Year 0 – 100: leachate collection and treatment Year >100: no leachate collection
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Environmental assessment
Results
-0,001
0
0,001
0,002
0,003
0,004
1 2a 2b 3a 3b 4a 4b 5a 5b 6a 6bHum
an h
ealth
[DAL
Y]
-0,000005
0
0,000005
0,00001
0,000015
1 2a 2b 3a 3b 4a 4b 5a 5b 6a 6b
Ecos
yste
m q
ualit
y [s
peci
es y
ears
]
0
20
40
60
80
100
1 2a 2b 3a 3b 4a 4b 5a 5b 6a 6b
Reso
urce
s [U
SD]
-50
0
50
100
150
1 2a 2b 3a 3b 4a 4b 5a 5b 6a 6b
Tota
l sco
re [-
]• Metal recovery has the lowest environmental impact in all endpoint
categories• Utilisation of fly ash in cement production has low impact in same
impact categories but high impact in others• Salt recovery increases environmental impact
Sustainable Management of Fly Ashes from Waste Incineration 10
Economic assessment
Sustainable Management of Fly Ashes from Waste Incineration 11
Economic assessment
Scenarios
• Same scenarios and system boundaries like environmental assessment
Scenario 1 Underground depositScenario 2a Stabilisation with 1 Mg cement/Mg fly ashScenario 2b Stabilisation with 0.3 Mg cement/Mg fly ashScenario 3a Metal recoveryScenario 3b Metal and salt recoveryScenario 4a Thermal treatment in coal-fired furnaceScenario 4b Thermal treatment in natural gas-fired furnaceScenario 5a Thermal co-treatment with combustible waste in a rotary kiln incineratorScenario 5b Thermal co-treatment with combustible waste in a grate furnace incineratorScenario 6a Utilisation of fly ash in cement productionScenario 6b Utilisation of fly ash in cement production with salt recovery
Sustainable Management of Fly Ashes from Waste Incineration 12
Economic assessment
Methodology
• Functional unit and uncertainty analysis identical to environmental assessment
• Discounted cash flow analysis
c0 investment cost [EUR]c1-cT discounted cash flow for year 1 to T [EUR]T time [a]r discount rate [-]
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Economic assessment
Results
0
200
400
600
800
1000
1200
1400
1 2a 2b 3a 3b 4a 4b 5a 5b 6a 6b
Cost
for t
reat
men
t and
dis
posa
l [EU
R]
Sustainable Management of Fly Ashes from Waste Incineration 14
Conclusions
Sustainable Management of Fly Ashes from Waste Incineration 15
Conclusions
• In-depth environmental and economic assessment of 13 different MSWI fly ash management scenarios conducted
• Recovery of metals, minerals for cement production and soluble chloride salts from MSWI fly ash possible
• Very low environmental impact of metal recovery, but impact of utilisation in cement production higher compared to disposal scenarios
• Economic costs for metals and minerals recovery higher compared to disposal scenarios
• Recovery of soluble chloride salts increases environmental impact and economic costs
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Conclusions
• Results of environmental and economic assessment not necessarily in line with waste hierarchy
• Trade-offs required to solve conflict of objectives
• Hazardous substances require final sinks
• No utilisation at any cost
• Decisions about utilisation or disposal should be made on a case by case basis after well-founded analysis
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ContactFlorian Huber Project Assistent
Phone: +43 1 58801 [email protected]
Questions and Discussion