1. Role of Waste-to-energy, WtE, in the circular economy, CE
Prof. Em. Carlo Vandecasteele
University of Leuven, Belgium

2. Waste hierarchy
In this conference: not only WtE discussed, but also other methods of waste treatment
Waste hierarchy gives degree of priority of these
Material recycling
Composting
Why not prevent, recycle,
reuse, all waste?
WTE
Combustion without E recovery Landfill

3. Circular Economy Does WtE still have role to play in CE?
In Europe more and more the concept of Circular Economy is promoted → Sustainable Development
CE is defined as economy that ‘maintains value of products, materials & resources for as long as possible in circulation in economy, minimising waste and resource use’
Prevention, preparing for reuse, recycling, all 3 perfectly fit in CE
Not obvious for WtE
WtE believed to compete with recycling (higher in Hierarchy)
Does WtE still have role to play in CE?

4. Does WtE still have role to play in CE?
EC (2017): (prudent) WtE can play role in transition to CE, provided waste hierarchy used as guiding principle, higher levels (prevention, reuse, recycling) not prevented My answer: unambiguous yes, and I mean that WtE has an essential role to play, for 6 reasons

5. 1. WtE combusts (should combust) only waste that to date cannot be recycled, for
Technical reasons
Insufficient separate collection; sorting, purification impossible
No methods to produce recycled material, at reasonable cost
Some waste (plastic/paper/textile) only recycled limited no. of times, because fibres shorten
Economic
Low market value for recycled product, material
High Capex, Opex for separate collection, sorting, purification
Energy consumption > production from virgin materials
Recycling cost > production from virgin materials
Environment, safety and health
Recycling may dissipate toxic substances over recycled products, source of human exposure, e.g. PBDEs from
WEEE plastics

6. 1.WtE combusts (should combust) only waste that to date cannot be recycled
In many countries fractions of household waste collected selectively →recycling/composting: vegetables-fruit-garden waste; paper and cardboard, metals, construction and demolition waste, hazardous waste, etc.
In Flanders (North of Belgium) 70.4 % (2014) collected selectively
Residual waste, i.e. waste currently not recycled, along with recycling residue (to date 33%), goes to WtE, because of landfill ban for MSW
In future, it is expected
residual waste will decrease ← increased prevention, increased selective collection
recycling will increase ← design for recycling, avoiding toxic compounds, better recycling technology …

7. 2. WtE does not compete with recycling, but with landfill (lower in hierarchy)
EU more recycling+ composting thanWTE, more WtE than landfill. GE, SW B DK AU, CH, NO < 3% landfill, landfill ban, MA, RO less advanced waste management, mainly rely on landfill. Countries with lot of recycling also lot of WTE, WtE and recycling complementary: No competition WtE ↔ recycling (higher in hierarchy), WtE ↔ landfill (lower in hierarchy)

8. 3. WtE is essential to keep hazardous materials out of CE
For waste containing toxic substances, WtE preferred over recycling, ex. PBDEs from WEEE plastics
Combustion (WtE) destroys toxic organic substances  recycling spreads it.
High conc’n → high T techniques, e.g. rotary kiln with secondary combustion
WtE retains HM in solid residues (FGC residues): S/S, stored in landfill
→ WtE keeps materials, environment free of toxic substances

9. 4. Allows material recycling from non-recyclable waste
Combustion of MSW: kg of bottom ash/ton of MSW
Heterogeneous: ash, stones, metals
Broad particle size distribution, 1-25 mm
4. Allows material recycling from non-recyclable waste

10. 4. Allows material recycling from non-recyclable waste
From BA can be recycled:
Metals: most valuable (recently interest for precious metals)
Mineral fraction: largest mass, volume
For recycling, e.g. as construction material, BA should comply with concentration and/or leaching limits. Often exceeded for e.g. Cu, Mo, Sb, Cl-,SO42-
In general treatment required before recycling

11. 4. Allows material recycling from non-recyclable waste.
State-of-the-art BA separation of 10 years ago:
Integrated Municipal Solid Waste Treatment Using a Grate Furnace Incinerator: The Indaver Case
C Vandecasteele et al. Waste Manag 27, 1366, 2006
More recently considerable progress in BA treatment: separation, sorting of metals, of mineral fractions
Wet, half dry (moist), dry treatment
Pneumatic sensor based sorting
Special treatments for reducing leaching of Cu, Sb
Recycling of MSWI Bottom Ash: A Review of Chemical Barriers, Engineering Applications and Treatment Technologies, B. Verbinnen, C. Vandecasteele et al., Waste biomass valor, 8, 1453, 2017
Ferrous (8.5%) and NF(1%) recycled. Purity often better than when directly separated from MSW (e.g. food can). Metal oxidation rather limited.
Sand and Granulates (< 2mm, 2-6 mm, 6-50 mm) aged, carbonated
to reduce metal leaching

12. 4. Allows material recycling from non-recyclable waste.
Bulk application
Artificial hills, e.g. ‘Green ship’
Subbase in road construction
Embankment, noise barrier
Raw material in cement production
Production of ceramics
Landfill cover
Structured construction material
BA fractions mixed in concrete as
(Partial) sand replacement,
(Partial) gravel replacement
(Partial) cement replacement after activation

13. 5. May generate energy with high efficiency
In WtE, HP, HT steam generated in boiler, applied in a Rankine (superheated) steam cycle to generate electricity using turbine, as in fossil fuel power plant
In WtE less advanced steam conditions (400°C, 40 bar) ← flue gas (more Cl, Na, K) corrosive,
and smaller installations
→ lower ηe (typically 20-25%)
Using other boiler materials to avoid HT corrosion → advanced steam cycle possible e.g. AEB, Amsterdam: complicated, very expensive ηe = η = 31%

14. 5. May generate energy with high efficiency
Low η occurs when only electricity generated, residual energy, heat lost
Other possibilities:
generate electricity, and also use residual thermal energy (LP, LT steam, hot water) for heating greenhouses, hospitals, offices, district heating, … CHP → higher overall η
use HT, HP steam (partly) directly→ higher overall η (up to 80-90%)

15. 5. May generate energy with high efficiency CHP
Gotenburg, Stockholm, Kopenhagen, Vienna, Paris… large district heating networks fed by WtE incinerators in, near the city
Additional advantage: short MSW transport

16. Location: Antwerp port– Waasland port
5. May generate energy with high efficiency Exampe of direct use of steam ECLUSE industrial steam network, in Antwerp port
Condensate
return duct
5 Nearby
Chemical companies,
large-scale companies
need steam for production processes
Steam duct (above/ below) ground
5 km
Superheated steam
400 °C; 40 bar
WtE plant +
Waste & sludge
Location: Antwerp port– Waasland port
In many countries WtE not in or near City, but in industrial area, park

17. 5. May generate energy with high efficiency
In Antwerp (left bank) Indaver & SLECO operate 3 grate furnace incinerators (household & commercial waste) and 3 fluidized bed incinerators (sludge & industrial waste)
Waste throughput: 1,000,000 ton/y; Heat production power: 250 MWth
Energy 50% renewable, 50% of CO2 climate neutral
Port of Antwerp is home to the largest chemical cluster in Europe
Chemical industry: energy intensive, consumption very stable
Steam used for: distillation, evaporation/drying, driving endothermic chemical reactions 17

18. 6. CE needs energy, WtE may partly feed it!

19. Conclusion I have shown that WtE
Combusts (should combust) only waste that to date cannot be recycled
Does not compete with recycling, but with landfill (lower in WH)
Is essential to keep hazardous materials out of CE
Allows material recycling from non-recyclable waste
May generate energy (50% renewable, climate neutral) with high efficiency
CE needs energy, WtE may partly feed it
Therefore WtE still has an essential role to play in CE