MODULE 4 – SYSTEM DESIGN –FROM A-Z

DR DARREN PERRINPRINCIPAL CONSULTANTEUNOMIA

The aim / learning outcome of this module is to “Provide an overview of the waste management ecosystem system and explain how it fits together and how to influence the performance of components within a part of that system”

• Generation, Collection, Treatment and Disposal

• The waste ecosystem system and interdependencies

• How to maximise the performance of your system

MODULE OUTLINE

KEY ELEMENTS OF AN EFFECTIVE WASTE MANAGEMENT SYSTEM

3 AREAS OF FOCUS

• Generation• Collection• Treatment & Disposal

GENERATION

GHG IMPACTS (NEGATIVE = GHG REDUCTIONS)

-23,000 -18,000 -13,000 -8,000 -3,000 2,000

Paper / cardPlasticGlassTextilesSteelAluminiumGarden (composting)Food waste (AD)WEEEOthersPaper / cardPlasticGlassTextilesSteelAluminiumGarden (composting)Food waste (AD)WEEEOthersLANDFILLINCINERATION CHPINCINERATION

Emissions, kg CO2 equivalent per tonne of waste managed

RESIDUAL WASTE TREATMENT

RECYCLING & COMPOSTING

AVOIDED PRODUCTION (WASTE

GLOBAL FLOWS OF PLASTIC PACKAGING MATERIALS 2013

Source: Ellen Macarthur Foundation

CIRCULAR ECONOMY PRIORITIES

EXAMPLE STRATEGIES TO MINIMISE GENERATION • User Pays

• Weight / Volume based charging• Container Deposit System • Plastic bag tax

• Multi use and Not Single Use Systems• Food Waste Prevention• Public Infrastructure• Litter Management

LITTER PREVENTION?

Image courtesy of Tim Smith (My Poor Brain)

COLLECTION

HH COLLECTION

Separate Collections

Kerbside Sorting

Twin / Multi Stream Collections

Comingled Collections

Complicated MRFSimple MRF

High Value MarketLower Value Market

OTHER HH MATERIAL ROUTES

Drop Off Centres

Container Deposit Systems

Transfer StationsLitter Collections / Street Scene Services

COLLECTION CONSIDERATIONS

• Where is Your Cost Point?• Influencing Material Value / Risk• Maximise Participation• Maximise the Amount of Material Collected • Minimise Contamination• Service Efficiency

THE AMOUNT OF MATERIAL CAPTURED IS A FUNCTION OF…….

• The number of materials targeted -Composition

• How many people have access to a service –Coverage

• How many people use that service –Participation

• How effectively they use the service –Recognition

• Set out Rate

• Participation Rate

• Capture Rate

• Recognition Rate

• Contamination Rate

RELATIONSHIP BETWEEN INDICATORS

ESTIMATING PLANNED MATERIAL RECOVERY

Coverage (90%)

Participation (70%)

Recognition (60%)

X

X

Material Available (Composition 10%)

X

Waste Generation X

100,000 tonnes

10,000 tonnes

9,000 tonnes

6,300 tonnes

3,780 tonnes

CHANGING VALUES AND HABITS

Knowledge

Motivation

Instruction

Reinforcement

People at different stages of thought depending on subject:

Pre-contemplation

Contemplation

Ready for action

Action

Maintenance

Different approaches may be required for each step

Values

Habit

Communication System

Convenient to use

Good Service

TREATMENT AND DISPOSAL

INFRASTRUCTURE

– Biological Technologies:– Composting (in-vessel)– Anaerobic digestion)

– Mechanical and Biological treatment (MBT)

– Sort first / bio-treat second– Bio-treat first / sort second (bio

drying) – Mechanical Heat Treatment (MHT) /

Autoclaving– Advanced Thermal Treatment (ATT)

– Gasification (1 or 2 staged)– Pyrolysis – Plasma gasification

– Mass burn incineration (energy from waste)

– Grate combustion– Fluidized bed combustion

– Transfer Station – Transfer only – Transfer / sorting

– Material Recovery Facility (MRF)– Clean – Dirty

– Landfill – Non- Engineered Landfill – Engineered Landfill (excl. gas

capture)– Engineered Landfill (incl. gas capture)

SYSTEM INTERFACE

THE MECHANICAL PART

• Separation of Material• Size e.g. Trommel screens, star screen, • Shape (2D/3D) e.g. Ballistic separator • Density e.g. Air drum separator, air knife • Properties e.g. Over-band magnetic• Transparency e.g. NIR Optical separation• Manual Visual

• Convey• Bulk, Transfer and Store

EXERCISE

• Objective: To Sort the recyclable materials into separate factions with the least equipment, and least contamination through a MRF

• Separate Groups • Timing: 20 mins

Screen

LightHeavy Magnetic

Ballistic Separator

Ferrous Magnetic

Wet Density Separation

Air Drum

Ferrous Magnetic

THE THERMAL PART

Source: Unknown

THE BIOLOGICAL PART

• Aerobic (air)• Windrow composting = Full bio stabilisation or

organic rich faction• In-vessel-composting = Full bio stabilisation or

organic rich faction • Bio-drying = partial stabilisation

• Anaerobic (no air)• Anaerobic Digestion = organic rich faction + biogas

THE WASTE MANAGEMENT SYSTEM

Source: Defra 2006

LANDFILL – WHAT IS IT?

• Engineered void (often following extraction)

• Membranes acting as barrier to groundwater

• Some methane collected for energy generation

• Leachate collected for management

LANDFILL – WHAT DOES IT DO?• Inputs

• Residual waste

• Outputs• Energy• Fugitive methane • VOCs / odours• Range of other gaseous emissions• Leachate

LANDFILL – PROS AND CONS

• Pros• Very flexible• Some energy

• Cons• Potential for odours etc.• Environmental impact • Poor image• Landtake

CONVENTIONAL INCINERATION – WHAT IS IT?• The combustion of waste• Different types

• Grate (rocking, moving, etc.) –‘mass burn’

• Oscillating kiln (Newlincs)• Fluidised bed (Allington, Dundee)

• Recovery of energy as…• Electricity (through driving of

steam turbine) or• Heat or• Some of both

Spitellau, Vienna - Design by Friedensreich Hundertwasser

CONVENTIONAL INCINERATION –WHAT DOES IT DO?• Main inputs

• Gas cleaning chemicals• Water• Energy

• Main Outputs• Power and/or heat (‘renewable’ and non-renewable)• Clear trade-off for steam turbines• CO2 (fossil and non-fossil)• NOx, PM, SOx, Dioxins etc.• ‘Bottom Ash’ (25%-ish input weight)• Metals from bottom ash (3-7%)• Air pollution control residues (3-4% input weight)

CONVENTIONAL INCINERATION –PROS

• Energy generated• Efficient generators of

heat (when configured in this mode)

• Some recyclables (metals)

• A tried and tested, reliable technology

Indaver Facility, Gent

CONVENTIONAL INCINERATION –CONS

• ‘Incineration’ – potential for negative public perception

• Where demonstrated, rarely with gas engine • Trade-off between power and heat• Heat outlets difficult to secure• Heat revenues rarely bankable• Generates hazardous waste• Ash handling costs rising (possibly significantly)• Lack of flexibility on throughput

ADVANCED THERMAL TREATMENT (ATT)• Advanced thermal treatment (ATT) is an umbrella

term that is used to categorise waste treatment technologies that utilise thermal processes to treat mixed general waste that are different to incineration.

• Primarily those that employ pyrolysis and/or gasification to process mixed general waste and also exclude full combustion thermal processes (i.e. incineration).

• Gasification • Thermal and chemical conversion of carbon based

material within mixed general waste into mainly gaseous outputs. Temperatures are in the range of 800-1100°C with air as the gasification agent and up to about 1500°C with oxygen. Overall gasification processes are exothermal, i.e. producing heat

• Pyrolysis • The thermal degradation of organic materials within

mixed general waste MSW in absence of oxygen. Temperatures are typically around 300-800°C. Overall the process is endothermic, i.e., energy is required for the pyrolysis process to proceed.

ADVANCED THERMAL TREATMENT (ATT)

STAGED INCINERATION – WHAT IS IT?

• Pyrolysis stage • Heats up waste (no

oxygen)• Liberates energy carriers

into gaseous phase

• Gasification phase • Further heating – oxygen,

steam, air• Further energy carriers

STAGED INCINERATION – PROS AND CONS

• Pros• Has potential to produce cleaner emissions• Some recyclables (metals)• May have high conversion efficiency

STAGED INCINERATION – PROS AND CONS

• Cons• Potential for negative public perception• Not widely demonstrated on mixed MSW• Requires pre-treated waste• Trade-off between power and heat• Heat outlets difficult to secure and heat revenues not bankable• Generates hazardous waste• Ash handling costs rising (possibly significantly)• Lack of flexibility on throughput

MECHANICAL HEAT TREATMENT / AUTOCLAVE – WHAT IS IT?

• Heating of material, sometimes under pressure, sometimes with added steam

• Usually followed by sorting of metals / plastics / ‘inerts’ (for recycling)

• Leaving a residue with raised biomass content (fibre)

MECHANICAL HEAT TREATMENT -WHAT IS IT?• Mechanical heat treatment is use of steam-based

thermal treatment, with or without pressure, in conjunction with mechanical processing for clinical and mixed general waste.

• There are two main types of facility that use mechanical heat treatment:• Autoclaving – a batch steam processing in a metal

vessel under the action of pressure• Rotary kiln - continuous heat treatment in a rotating

vessel, not under pressure

MECHANICAL HEAT TREATMENT / AUTOCLAVE – WHAT DOES IT DO?• Inputs

• Energy• Water (as steam)

• Outputs• Metals (good quality)• Plastics (not clear how marketable)• Inert material (possibly for

engineering)• VOCs, ammonia and CO2• Sterile fibrous material

• Some processes refining for use as fuel Waste Treatment Autoclave

MECHANICAL HEAT TREATMENT / AUTOCLAVE – PROS AND CONS

• Pros• Not widely demonstrated on system basis• Needs other forms of treatment to deal with

material outputs

• Cons• Likely low planning risk• Can capture some unrecycled materials• May enable some bespoke fuel development

MBT (MECHANICAL AND BIOLOGICAL TREATMENT

A generic term for an integration of several processes and technologies commonly found in different waste management facilities such as MRFs and biological treatment facilities.

Eco Deco, Italy

WHAT IS THE ‘M’ ‘B’ ‘T’ ?• Mechanical - Use of common mechanical

processes used in MRFs • Biological - Uses the natural biological process

and common aerobic and anaerobic treatment methods

• Treatment - Treating the waste as the process renders waste more stable for deposit to landfill

• But… the waste feedstock is different.

HISTORY OF MBT• Developed in the early 90s in

Austria/Germany• Germany in response to landfill ban of residual

waste• Seen as a cheaper alternative to incineration

for reducing the quantity of biological waste going to landfill

• Widespread use, mainly across Europe• Mixed level of success

PURPOSE OF AN MBT • Divert BMW from landfill• Reduce weight and volume of waste• Stabilise organic material prior to disposal at landfill• “last chance” at collecting recyclable materials not

collected at the kerbside• Manage the organic waste stream in the waste in more

effective environmental manner • Additional approach to generate electricity (where AD

in place)• Increase value of the residual waste

MBT – PROS AND CONS• Pros

• Likely low planning risk• Some configurations well proven• Can capture some unrecycled materials• May enable some bespoke fuel development• Flexible in some configurations

• Cons• Land use• Some configurations still problematic• VOC emissions / odours• Marketability of some recyclates unclear• Conditions for fuel offtake will vary

BROAD TYPES OF MBT

• 1. Dry MBT – Maximum separation of dry recyclables for material value and then process Organic

• 2. Wet MBT – Separate out recyclables through density separation and magnets and partially dissolves organic material in preparation for AD

• 3. BMT – Biological process first and then remove limited recyclables to increase CV for fuel

DIFFERENT MBT CONFIGURATIONS

• What are you trying to achieve?• Mass / volume reduction • Energy• Stabilisation• Material recovery• Fuel production

• What is the priority?

TYPICAL MATERIALS RECOVERED FROM AN MBT • Paper / Card• Textiles• Plastics• Glass / Aggregate • Compost-like Output• Refuse Derived Fuel / Solid Recovered Fuel• Metals (Ferrous/Non-Ferrous)

TYPICAL MBT MASS BALANCE

MEETING EXPECTATIONS AND RISK TRANSFER

What goes in .... must come out! – poor quality input leads to poor quality output