3. Litter is an emission!
“managed”
residue
(landfill)
Ecological impacts:
Exhaustion of resources and
Emissions (gasses, liquids and solids)
needed
goods
recovered/
recycled
waste
collected
waste
consumption/
use
added
product
post-use
waste
fulfilled
needs
unfulfilled
needs
resources
Circular economy: cost/profit driven
4. Litter is an emission of inert solids
• Litter-emissions are different from “known/familiar” chemical
or gaseous emissions.
• Litter is an emerging global ecological problem and there is no
adequate legal framework to deal with it.
• Detection/sampling requires a different scale
– Detection of chemicals in water: microgrammes per liter
– Detection of solids in water: grammes per 1000 m3
• Hardly any methods for detection and no standards for
emissions of (non-toxic or inert) solids in water.
• Plastics dominate litter emissions
• Plastics behave different in water compared to minerals
5. Litter can be emitted from every stage of
the present and future (circular) economy
• Pre-production materials (pellets)
• Lost products/parts (broken car parts)
• Post-use products (littered beverage pack)
• Collected products (hygiene products from
wwt-plants)
• Recycled products (scrap)
• Landfilled products (picked by birds)
• The (circular) economic system leaks!
6. Lighter solids will be transported by water
• Results Meuse sampling (Mosa Pura):
– Plastics are dominant
– Large and small fragments
– Floating, suspended and sinking
– Hydraulic/meteorological conditions are relevant
– Multiple sources
– Broad range of materials
– Contaminated and mixed
– Mixed with organic/natural materials
7. Found concentration of items/km2
in upper part of the water column (0 – 70 cm)
Items per km2 (surface and suspension together)
0
10.000
20.000
30.000
40.000
50.000
60.000
70.000
80.000
1 2 3 4 5
totaal
flex
rigid
Suggests a relationship with throughput (298, 125, 0, 113, 113 m3/s)
total
flexible
rigid
80.000
70.000
60.000
50.000
40.000
30.000
20.000
10.000
0
8. Items larger and smaller than 25 mm
Number of items caught
0
100
200
300
400
500
600
surface suspension
Large and small
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
surface suspension
Majority of items (± 75%) are “small” macroplastics
(between 3,2 mm and 25 mm)
> 25 mm (large)
< 25 mm rigid
< 25 mm flex
surface suspension surface suspension
600
500
400
300
200
100
0
100%
0%
90%
80%
70%
60%
50%
40%
30%
20%
10%
10. Items surface vs. suspension
per km2
0
10.000
20.000
30.000
40.000
50.000
60.000
70.000
Surface per km2 Suspension per km2/m3
totaal
flex
rigid
More items on surface,
most rigids
Less items in suspension,
most flexibles
total
flexible
rigid
70.000
60.000
50.000
40.000
30.000
20.000
10.000
0
surface suspension
11. Number of items transported
towards the sea
Number of items per hour
0
5.000
10.000
15.000
20.000
25.000
30.000
35.000
1 2 3 4 5
• Average: 15.127 items/hr
– Flexible: 6.079 items
– Rigid: 9.049 items
• Maximum: 30.387 items/hr
– Flexible: 8.417 items
– Rigid: 21.970 items
• Conditions:
– Water velocity: ± 3 km/hr
– Width river: 150 m
– Only top 70 cm
total
flexible
rigid
10.000
35.000
30.000
25.000
20.000
15.000
5.000
0
13. The most promising approach for river
litter is aimed at it’s sources
River litter sources:
1. Fly-tipping and illegal dumping in the flood
plain
2. Run-off from streets and roadsides in the
catchment area
3. Sewage overflows to rivers and tributaries
4. Industrial spills (pellets and scrap)
14. Ultimate destinations
• Sinks:
– Land (waste in remote places on land)
– River bottom and sediment (empty Meuse
bottom)
– Beaches (remote beaches)
– Sea bottom (deep sea pictures)
15. In the meantime:
• Physical effects (e.g. on biota)
– Microplastics (< 1 mm): plankton and mussels
– Mesoplastics (< 5 mm): smaller fish and birds (Fulmars)
– Small macroplastics (< 25 mm): larger fish and birds
(Albatrosses)
– Large macroplastics (>25 mm): bigger fish and marine
mammals (whales)
• Toxicological effects (delivering POP’s into food chain)
• Impacting ecosystems on seafloor
• Impacting recreational, agricultural, economic value of
floodplains and beaches
• Endangering use of waters (entangled boat screws and
blocked cooling systems)
16. Catch litter before it’s gone.
• At sea litter is too dispersed to catch!
• The river is the last interception place
• Catch closer to the source is better
• Catch emissions at emission points is best
• Catch diffuse emissions (fly-litter) in tributaries
• Prevent emission is ultimate
• Refrain from using “uncatchables” (< 1 mm)
(microbeads in cosmetics)
18. Characteristics of river litter
To catch river litter, these
characteristics are relevant:
• Size
• Material
• Surface to Volume ratio (s/v ratio)
• Buoyancy
19. Characteristics of river litter
• Size:
– Micro < 1 mm
• Not visible with naked eye
– Meso from 1- 5 mm (“new” category)
• Cannot be “picked”
– Macro-small from 5 - 25 mm
• Difficult to pick,
• small products or fragments from original products
– Macro-large > 25 mm
• Very visible, can be picked
20. Characteristics of river litter
• Material:
– Non-plastics:
• Metal
• Glass
• Paper/board
• Ceramic
• Natural materials and textile fibers
– Plastics:
• PE (LD, LLD, HD), PP, EVA (sw < 1)
• PET, PC, PA, ABS, PUR, PS, PVC, rubbers (sw > 1)
– Combinations
• PE insulated electrical wire
21. Characteristics of river litter
• Shape: surface to volume ratio (s/v-ratio)
– High:
• Extruded film and foil; thin walled, flexible plastics
– Plastic bags and wrappers
– Average:
• Thicker extruded/thermoformed products and films
– PS coffeecups, foodtrays
• Thin walled injection moulded products
– buttercups
– Low:
• Most rigid injection moulded or thick extruded products
– Plastic pellets, bottle caps
– PP or PVC pipes or fragments
– Cotton butt sticks
22. Characteristics of river litter
• Buoyancy
– High:
• Closed hollow products (PET bottle)
• Closed-cell foams (EPS, PUR-foam, PE-foam)
• Most lighter plastics (sw < 1) with low s/v ratio
– PE, PP
– Neutral:
• Contaminated products (sand filled PE bag)
• Most plastics with high s/v ratio
– Low:
• Most heavier plastics (sw > 1) with low s/v ratio
– PET, PS, PA, PUR, PVC, PC
23. Some consequences:
• Size determines collection tools and
equipment
• Material determines the actual or potential
toxicity of littered products and
revalorisation options
• Shape determines the behaviour of litter in
moving water and whether litter is deposited
on banks or in vegetation
• Buoyancy determines the place of litter in
calm waters
25. Before litter gets in the water:
• Stop using products, e.g …
– microplastics in cosmetics (Beat the Microbeads)
– Shopping bags (Ban the Bag)
– EPS foam in packaging
• Prevent emissions, e.g …
– Leak-proof waste management systems
– Anti-littering programs (education at schools)
– Technical solutions at water treatment plants (membrane
filtration)
– Emission controlled landfill sites (birds, wind)
• Clean-up campaigns, e.g …
– Nederland Schoon
– Schone Maas Limburg
– My Beach
26. When litter is in the water:
• On surface:
– Deflection booms
– Floating litter traps
But: obstructing river navigation
• In water column:
– Fences and screens
– Nets
But: problematic for fish migration and water passage
• On bottom:
– Dredging in calm waters
But: Different “business”
27. Catch what, where and how.
SW: specific weight
S/V ratio: surface/volume ratio
Floating:
High buoyancy
or
SW < 1 g/m2 and
small s/v ratio
< 1 mm
microplastics
1 - 5 mm
mesoplastics
5 - 25 mm
macroplastics
> 25 mm
macroplastics
Sinking:
Low buoyancy
or
SW > 1 g/m2 and
small s/v ratio
Suspended:
Neutral buoyancy
or
SW ≈ 1 g/m2 and
high s/v ratio
Prevent use or
catch at
treatment
plant
Prevent use or
catch at
treatment
plant
Catch at
emission
point
Catch at surface
in tributaries
or non-navigated
rivers
Catch at surface
in tributaries
or non-navigated
rivers
Prevent use or
catch at
treatment
plant
Catch at surface
(sw < 1) in
shallow water or
clean up
before entering
water
Catch at surface
(sw < 1) in
shallow water or
clean up
before entering
water
Catch at
emission
point
Catch at
emission
point
Recover
from dredged
sediment
Clean up before
fragmentation
and entering
water and recover
from dredged
sediment
29. Prevent emissions is ultimate
• Circular economy should be leak-proof
• Develop “anti-littering” campaigns and attitude
• Facilitate any waste management system that
prevents emissions, also financially
30. Catch microplastics
(< 1 mm)
• Stop using microplastics when possible
• Filter at source (e.g. washing machines)
• Filtration at waste water treatment plant
• It is practically impossible to catch microplastics in
surface water
31. Catch mesoplastics
(1-5 mm)
• Catch at emission point
• Focus on waste water treatment plants
• Stop using products that fall apart easily (e.g. EPS)
• Support Clean Sweep initiatives (pre-production
pellets)
32. Catch small macroplastics
(5-25 mm)
• Catch rigid floating fraction in tributaries
(sw < 1, s/v low)
• Catch flexible floating fraction (sw < 1, s/v high) in
tributaries with little turbulence and limited depth
• Catch flexible sinking fraction (sw > 1, s/v is high) in
tributaries with some turbulence and limited depth
• Clean up large sinking fraction before it get
fragmented and small fragments can reach the
waters
33. Catch large macroplastics
(> 25 mm)
• Catch rigid floating fraction (sw < 1, s/v small) on
surface in rivers or tributaries
• Collect flexible suspended fraction (s/v high) in
tributaries with little turbulence and limited depth,
but preferably before entering the water
• Collect sinking flexibles and rigids before entering
the water and before they get fragmented
35. Measures which can be taken
immediately:
1. Increase public awareness on litter problem
2. Strengthen anti-litter behavior
3. Develop/expand clean up programs
4. Improve performance of water treatment plants:
Focus on micro and meso plastics
5. Install floating litter traps preferably in (shallow) tributaries
6. Install multiple floating litter traps in rivers (in outside bend)
7. Remove sinking litter from sediment by dredging in slow
streaming water
8. Install monitoring program to determine
effectiveness of all measures
38. Recovery options
• Litter is dominated by plastics
• Plastics are manufactured from oil
• Litter can replace “virgin” materials, through
– Material recycling
– Chemical recycling (Pyrolysis)
– Energy recycling
• Necessary technologies are available
39. But, limitations for recovery are :
• Many different polymer types in the collected litter
• Probably degraded by UV-light
• Contaminated with organic matter
But:
• Prevention of river litter flowing to the
oceans should be the first objective!
Therefore:
• Catching litter should have higher priority
than high value recovery!
