industry guidance: dealing with household food waste at ad ... guidance management of … · food...

Final Report

Industry Guidance: Dealing with Household

Food Waste at AD Facilities – Management

of Liners

A guide to assist AD operators in relation to food waste in liners

Project code: OIN027-002

Research date: January to June 2016 Date: Updated September 2017

WRAP’s vision is a world in which

resources are used sustainably.

Our mission is to accelerate the move to a

sustainable resource-efficient economy

through re-inventing how we design,

produce and sell products; re-thinking

how we use and consume products; and

re-defining what is possible through re-

use and recycling.

Find out more at www.wrap.org.uk

Document reference: [e.g. WRAP, 2006, Report Name (WRAP Project TYR009-19. Report prepared by…..Banbury, WRAP]

Written by: Dr Jill Doherty (Senior Associate) & Ms Debbie Nesbitt (Senior Scientist)

Front cover photography: Food waste collected for AD treatment.

While we have tried to make sure this report is accurate, WRAP does not accept liability for any loss, damage, cost or expense incurred or arising from reliance on this

report. Readers are responsible for assessing the accuracy and conclusions of the content of this report. Quotations and case studies have been drawn from the public

domain, with permissions sought where practicable. This report does not represent endorsement of the examples used and has not been endorsed by the

organisations and individuals featured within it. This material is subject to copyright. You can copy it free of charge and may use excerpts from it provided they are not

used in a misleading context and you must identify the source of the material and acknowledge WRAP’s copyright. You must not use this report or material from it to

endorse or suggest WRAP has endorsed a commercial product or service. For more details please see WRAP’s terms and conditions on our website at

www.wrap.org.uk

http://www.wrap.org.uk/

WRAP – Industry Guidance: Dealing with Household Food Waste at AD

Facilities – Management of Liners 1

Executive summary

This guidance document has been prepared by WRAP as part of the industry led Food

Waste Recycling Action Plan (FWRAP). It aims to assist wet Anaerobic Digestion (AD)

operators accepting and treating household food waste from local authorities and the

food supply chain including food manufacturers and retailers.

The guidance has been undertaken in consultation with a number of stakeholder

groups. It deals with the management of liners, in particular polyethylene liners and

aims to summarise the key issues that operators are faced with as well as setting out

standard operating procedures for complying with PAS 110.

In order to increase recycling rates, local authorities are increasingly looking at

developing food waste collection schemes that not only provide a high level of service to

the customer but also enable high participation and capture rates. It is therefore

imperative that effective intervention and collaboration between the AD operators and

local authorities takes place in order to drive this forward.

Liners are often seen by residents as part of the system for collecting food waste and

the results from WRAP’s pilot trials1 demonstrated that the use of liners, especially when

combined with other interventions does increase public participation. Taking this into

consideration, increasing numbers of local authorities allow the use of plastic (PE) liners

in food waste collections as opposed to compostable liners.

Plastics are however one of the main contamination or quality related concern for all AD

systems, and in particular for wet AD systems. If the digestate product visually contains

significant amounts of plastics it will fail to comply with PAS 110.

Therefore, there is a need to ensure that food collection and treatment systems are

closely aligned in order to minimise plastic contamination in the end product. In this

regard, Standard Operating Procedures (SOPS) have been developed to provide a

holistic procedure of the approach to the acceptance and management of food waste in

liners. These are designed to assist AD operators and result in limiting the physical

contamination ending up in digestate. They include:

▪ Contractual specifications;

▪ Pre-waste acceptance procedures;

▪ On site waste acceptance procedures;

▪ Identification of contamination prior to treatment; and

▪ Removal and management of contamination.

A desk based investigation was undertaken into potential innovative approaches that

could be used to increase collaboration between those producing the waste, those

responsible for its collection and the AD operators. This study included input from both

1 http://www.wrap.org.uk/content/food-waste-collections-guide-section-11-increasing-food-waste-capture-existing-separate-week

http://www.wrap.org.uk/content/food-waste-collections-guide-section-11-increasing-food-waste-capture-existing-separate-week



AD operators and local authorities as well as a review of best practice in other European

countries. The most popular approaches were as follows:

▪ Collaboration between AD operators and local authorities: This included: the use of

incentives such as production of joint literature, contribution towards the cost of

liners and towards communication campaigns, sponsorship of local events,

provision of grants for local activities and sponsorship of household awards;

▪ Innovation in future contracts. This included quantification of contaminants,

introduction of financial penalties, profit share agreements and variable gate fees;

▪ Visual scoring system. The system could take the form of a series of photographs

used to ascertain the acceptable waste streams and could be included in the input

specification and linked to the payment mechanism; and

▪ Standardised measurement system. There are a number of standardised

measurement systems in use across Europe for determining physical contaminants

in the biowaste industry which could be adapted for use in the UK.

Central to the successful operation of any waste management operation is effective

communication and consultation between stakeholders, especially when waste

producers and collectors are distinct from the operators of the facility. The report

considered a number of mechanisms by which communication and consultation could

be improved. These included:

▪ The development of strategic partnerships in order to facilitate a good working

relationship between all parties;

▪ Regular meetings between all parties. These are considered to be an effective

mechanism for the identification and remediation of any issues as well as ensuring

that all parties are adhering to the contract and the input specifications;

▪ Community events. The hosting of community events is considered effective in

engaging consumers in the AD process from the point of collection through to

demonstration of the end product;

▪ Production of literature including the setting of clear parameters of the feedstock

the facilities can accept and the type of liners that can be processed; and

▪ Increased collaboration with local shops and supermarkets in order to ensure that

the correct liners are being stocked locally.

Finally, the training of staff and development of a programme to entice and sustain

behavioural change will ensure that any measures implemented to improve the quality

of food waste are adhered to.

Staff training and development can take a number of different forms including "on the

job" "off the job" training and E-learning. What is important however is to ensure that it

is all encompassing and that it has participation and buy in from senior management as

well as those "on the ground". During the training staff need to be made aware of why

they are there and therefore focus needs to be provided on the importance of reaching

standards and business continuity.



Contents

1.0 Aim of this Guidance .............................................................................................. 4

1.1 Food Waste Recycling Action Plan ....................................................................... 4

2.0 Contamination ........................................................................................................ 5

3.0 Legislative Context.................................................................................................. 6

3.1 EU Circular Economy Package .............................................................................. 6

3.2 PAS 110:2014 Producing Quality Anaerobic Digestate ..................................... 6

4.0 Facilities in Scope .................................................................................................... 7

5.0 Liner Use .................................................................................................................. 8

5.1 Polyethylene Liner .................................................................................................. 8

5.2 Biodegradable Liners............................................................................................. 9

5.2.1 Bioplastics.................................................................................................... 9

5.2.2 Bioplastics in the wet Anaerobic Digestion Process ............................ 10

6.0 Standard Operating Procedures .......................................................................... 11

6.1 Contractual Specification .................................................................................... 11

6.2 Pre-Waste Acceptance Procedures ................................................................... 11

6.3 On Site Waste Acceptance Procedures ............................................................. 12

6.4 Standardised Inspection Process ...................................................................... 12

6.5 Identification of Contamination Prior to Treatment ....................................... 12

6.6 Pre-Treatment - Removal and Management of Contamination ...................... 13

6.7 Contamination Management Approaches ....................................................... 13

6.8 Front End Removal - Depackaging..................................................................... 13

6.9 Back End Removal ................................................................................................ 16

6.10 External Verification ............................................................................................. 16

7.0 Contractual Arrangements .................................................................................. 17

7.1 Input Specification ............................................................................................... 17

8.0 Innovative Approaches ........................................................................................ 19

8.1 Collaboration between Operators and Local Authorities .............................. 19

8.2 Innovation in Future Contracts .......................................................................... 20

8.2.1 Visual Scoring System .............................................................................. 20

8.2.2 Standardised Measurement System ..................................................... 21

9.0 Improved Communication & Consultation ........................................................ 23

9.1 Development of Strategic Partnerships............................................................ 23

9.2 Regular Meetings ................................................................................................. 23

9.3 Community Events ............................................................................................... 24

9.4 Production of Literature ...................................................................................... 24

9.5 Local Shops/Supermarkets ................................................................................. 25

10.0 Staff Involvement & Training .............................................................................. 26

11.0 Definitions.............................................................................................................. 27

Figures

Figure 1: Potential Types of Feedstocks .................................................................................... 7

Figure 2: Advantages and Disadvantages of Liner Use ........................................................... 8

Figure 3: Depackaging Machinery ............................................................................................ 15

Figure 4: Definitions ................................................................................................................... 27



1.0 Aim of this Guidance

This guidance document has been prepared by WRAP as part of an industry led Food

Waste Recycling Action Plan (FWRAP). It aims to assist wet Anaerobic Digestion (AD)

operators accepting and treating household food waste from local authorities and the

food supply chain, which includes food manufacturers and retailers.

The guidance has been undertaken in consultation with a number of stakeholder groups

including: local authorities, strategic waste partnerships, industrial groups and AD

operators.

The guidance deals with the management of liners, in particular, polyethylene liners.

The aim of the guidance is to summarise key issues operators are faced with when

accepting food waste in liners. In addition, the guidance sets out standard operating

procedures that are required to be in place to ensure that the outputs comply with the

PAS 110.

1.1 Food Waste Recycling Action Plan

Through the FWRAP, WRAP is working with industry stakeholders to help food waste

collectors maximise and sustain the amount of food waste they collect. This is integral to

securing the supply of food waste as a key feedstock to the Anaerobic Digestion (AD)

and In-Vessel Composting (IVC) sector.

Despite the UK’s best efforts to minimise food waste, there are still 7 million tonnes

wasted every year by households alone, albeit that there will always be a significant

proportion of unavoidable food waste. Increasing the volume of food waste recycled

could provide a huge boost to England’s plateauing recycling rates and help the UK

deliver on the target of 50% recycling by 2020.

Increasingly local authorities are looking at developing food waste collection schemes

that not only provide a high standard of service to the householder but also enable high

participation and capture rates.

Interventions and more collaborative working between the AD operators and local

authorities will play an increasingly important role over time.



2.0 Contamination

Unfortunately, plastic is one of the main contamination or quality related concerns for

all AD but particularly for wet AD systems, where the plastic materials can form a

‘floating layer’ on the surface of the wet digestate. This causes processing and safety

issues associated with trapped gases and flow blockages, potentially resulting in

catastrophic plant explosions.

Shredded plastic particles tend to go through the digestion process with plastic residues

contaminating the visual appearance of the digestate. If the digestate product visually

contains a significant amount of plastics, it will fail to comply with Publicly Available

Specification (PAS 110) and will have to be fine-screened to remove the plastics,

resulting in the requirement for an additional process step. Plastic particles in digestate

do not break down or degrade, are unsightly and lowers the quality of the final product.

It should be noted though; whilst compliance with PAS 110 greatly reduces the amount

of plastics in the digestate, it does not eliminate it completely. Meeting this standard

therefore can result in potentially large amounts of plastic being present. This not only

has the potential to damage soils but also, as a public perception issue, does not always

result in a “clean” product being produced. This can lead to a potential lack in confidence

of the system as well as visual detriment to the receiving area.

The issue therefore is not simply about meeting PAS standard but moving beyond this to

produce the most sustainable and environmentally friendly product as possible.



3.0 Legislative Context

3.1 EU Circular Economy Package

The European Union published a Circular Economy Package in December 2015,2 with the

aim being to stimulate Europe’s transition towards a circular economy which will boost

global competitiveness, foster sustainable economic growth and generate new jobs. The

management and treatment of food waste features high on the agenda of this package

with actions suggested to halve the amount of food waste produced by 2030.

If UK government adopts the EU Circular Economy package this will have the effect of

providing further focus for local authorities and businesses to change their practices in

terms of the future management of this waste stream.

3.2 PAS 110:2014 Producing Quality Anaerobic Digestate

PAS 110:2014 came into effect on 31 July 2014. The PAS is a publicly available

specification and not a full British Standard. It was developed to set out clear guidelines

for operators wishing to deliver a consistent product that complies with industry

specifications. PAS 110:2014 is a non-statutory document3 and does not set regulatory

limit values for the quality and use of digestates. PAS 110 specifies ‘that the AD system is

allowed to accept packaged biowastes/biodegradable non-waste materials that are

depackaged prior to AD’, subject to conditions. For example, reasonable care is required

to be taken to avoid any contaminated wastes, products or materials from becoming

included with the input materials.

PAS110 states that where packaged wastes are accepted there will be a pre-treatment

process that uses reasonable endeavours to remove non-biodegradable packaging prior

to loading those biowastes/ biodegradable materials into the digestion system. Typically,

facilities have depackaging machinery or equipment in place that are capable of

removing all types of packaging.

PAS110:2014 sets clear limits for permitted levels of contamination in digestate. These

limits vary according to the nitrogen content of the digestate, cover all contaminants

materials at a particle size of 2mm or more and include all visible contaminants.

2 http://ec.europa.eu/environment/circular-economy/index_en.htm

3 For food waste to be classified as recycled in Scotland and Wales, local authorities have to send their food waste to PAS110

accredited operations.

http://ec.europa.eu/environment/circular-economy/index_en.htm



4.0 Facilities in Scope

There are three potential types of feedstocks that can go into a wet AD system either

singly or combined:

Figure 1: Potential Types of Feedstocks

Feedstock Feedstock Details In Scope

Food Waste

Domestic food waste.

Commercial and industrial

food.

Energy/Arable Crops

Purpose grown crops

cultivated for their high

calorific value. The key

crops used in the UK are

maize silage, grass silage

and whole crop cereals.

Agricultural Residues

These include animal wastes such as cattle and pig slurry, manures, feed waste and bedding.

This guidance document is primarily relevant to wet AD Operators accepting food waste

feedstock from local authorities. It will also be of interest to AD Operators accepting

commercial and industrial food waste with liner contamination issues.



5.0 Liner Use

Liners are often seen by residents as part of the system for collecting food waste.

Previous trials suggest that residents prefer to use liners so that food waste storage

containers used to securely transfer food from the internal kitchen caddy to the external

bin can be kept clean and hygienic.

Advantages and disadvantages of liner use are as follows:

Figure 2: Advantages and Disadvantages of Liner Use

Advantages and Disadvantages of Liner Use

Advantages Disadvantages

▪ Makes process cleaner for users;

▪ Many users prefer to use liners;

▪ Potentially higher participation rates & yields

achieved;

▪ Potentially higher participation rates;

▪ Collections easier for crews; and

▪ Collection chambers in vehicles are cleaner

and chances of spillages/leakages reduced.

▪ Adds operational costs to the service, if they

are supplied free of charge;

▪ Can be time consuming to set up distribution;

▪ Wastage of liners if distributed inefficiently;

and

▪ Requirement for depackaging equipment.

The type of liner selected for use depends on:

▪ The requirements of the treatment facility;

▪ The cost to the local authority, for example, if liners are provided free of charge to the

users; and

▪ The cost to the users/waste producers, if they must purchase the liners.

To encourage householder participation, some local authorities allow the use of plastic

(polyethylene, PE) liners or standard plastic carrier bags in food waste caddies as

opposed to compostable liners or carrier bags. Current figures from WRAP show that one

fifth of local authorities provide liners to households for food waste collections. However,

a number of local authorities are also considering a switch from compostable to

polyethylene liners. Research carried out by WRAP has shown that there is up to a 32%

increase in food yields (kg/hh/yr) where an intervention package comprising caddy

liners, communications and residual bin stickers are introduced.

Different types of liners, currently used within the waste management industry are

discussed below:

5.1 Polyethylene Liner

Polyethylene (PE) is the most commonly used plastic polymer in the world. Often known

as polyethylene and polythene, its uses include film, packaging and containers, from

bottles to buckets. PE is produced in three main forms:

▪ Low density (LDPE) (< 0.930 g cm-3);

▪ Linear low density (LLDPE) (ca 0.915-0.940 g cm-3); and

▪ High density (HDPE) (ca 0.940-0.965 g cm-3).



PE is considered a strong, lightweight thermoplastic with very good chemical resistance.

In terms of using PE as a liner, this is primarily referring to film such as:

▪ HDPE – food packaging and shopping bags;

▪ LDPE – cling film and milk carton lining; and

▪ LLDPE – stretch film.

Research undertaken with AD operators has suggested that PE liners are the most

favoured option at the current time, primarily due to the fact that they are easily

removed at both the front end, and where required, from the back end of the processing

system.

5.2 Biodegradable Liners

Two widely available types of biodegradable liners are used for food waste collections:

▪ Compostable liners and compostable carrier bags, for example made from starch

based polymers or biopolymers. They are available in a number of different

specifications based on their size and thickness; and

▪ Paper liners, made from a high moisture resistant paper.

5.2.1 Bioplastics

The term ‘bioplastics’ describes a range of materials with differing properties and

applications, so the term can be ambiguous. Generally, bioplastics are categorised into

three major groups – based on whether a bioplastic is biodegradable, bio-based or is

both biodegradable and bio-based.

The terms ‘bio-based’ and ‘biodegradable’ are not interchangeable, as biodegradable

bioplastics can be made from petroleum and not all bio-based bioplastics will

biodegrade.

The production of all bioplastic materials is forecast to grow in coming years.



Compared to standard polyethylene, most bio-degradable bioplastics have a higher

density typically around 1.25 – 1.3 g cm3.

5.2.2 Bioplastics in the wet Anaerobic Digestion Process

The Anaerobic Digestion Quality Protocol (ADQP) states that biodegradable plastic

packaging that is independently certified to BS EN 13432 or either of the similar

standards DIN V 54900 or ASTM D6400 that is used to collect food waste shall be

permitted.

Several kinds of commercial biodegradable plastics are marketed as being able to

degrade under anaerobic conditions, although in reality most do not degrade quickly

under these conditions.

Products are being developed specifically for anaerobic digestion applications, some

based on PHA (polyhydroxyalkanoate) and quoting results from testing in accordance

with ASTM D5511. Factors affecting the anaerobic digestibility of polymers include pH,

bacteria type, temperature, molecular weight, chemical linkages, and enzymatic access

to the material.

Unless bioplastics are rapidly soluble or dispersible, a form of pre- treatment such as

shredding is required to make them suitable for processing by wet anaerobic digestion.

Otherwise, they may self-segregate by flotation or sedimentation then require removal

and will not actually be digested, even if anaerobically digestible.



6.0 Standard Operating Procedures

These Standard Operating Procedures (SOP) below have been developed for wet AD

operators to give a holistic picture of the approach to accepting and managing food

waste in liners. If these procedures are followed it is thought that they will assist AD

operators and reduce the physical contamination ending up in the digestate.

6.1 Contractual Specification

Key to the success of any contractual arrangement is the effective communication and

improving understanding between the local authority and the AD operators. In this

regard, the implementation of a contractual specification will be key and should:

▪ Identify (or preferably specify) the type(s) of suitable liners. This will require careful

collaboration between the local authority and the operator to ensure that the liners

being proposed are suitable for acceptance at the facility and are in line with the

current (or future proposed) practices within the household collection systems;

▪ Specify the types of feedstock materials that are acceptable;

▪ Agree a methodology to quantify and qualify contamination in waste delivered

(including pricing the contamination where this is considered necessary), how

rejected material, the quality issues and end destinations are reported;

▪ Agree acceptable contamination banded limits; and

▪ Agree a management option for contaminated loads, including processing fees on a

scale, return fees or disposal fees etc.

These actions are described in more detail in Section 8, Contractual Arrangements.

6.2 Pre-Waste Acceptance Procedures

If not dealing directly with the waste producer, the AD Operator could carefully verify the

information received at the pre-acceptance stage. This should include the Duty of Care

information, the contact details of the waste producer and a full description of the waste

with the correct EWC code in order to comply with site permitting.

Consideration should be given to the following:

▪ For each new waste enquiry, a typical compositional analysis should be undertaken;

▪ A representative sample(s) of the waste should be taken from the production

process and analysed;

▪ Screen out unsuitable wastes and confirm any details relating to composition;

▪ Identify verification parameters that can be used to test waste arriving at the site;

▪ Identify any substances within the waste (for example, by-products) that may affect

the treatment process;

▪ Identify any substances within the waste that may react with other reagents;

▪ Accurately define the range of hazards exhibited by the waste;

▪ Identify any substances within the waste that may be unaffected by the treatment

process and transfer in an unaltered state as a residue in the effluent; and

▪ Ensure regulatory compliance with the permit.

It should be noted that the waste producer has obligations under Duty of Care

requirements to provide information on the following:



▪ Composition of the waste;

▪ Its handling requirements;

▪ Its hazards; and

▪ EWC codes.

This information is required on transfer of the waste from the producer to a third party.

In situations where the waste producer and AD operator are separated by a number of

stages (for example haulage contractors, brokers and waste transfer operators) the

operator should carefully verify the information received at the pre-acceptance stage.

This should include the Duty of Care Obligations, contact details for the waste producer

and a full description of the waste. Within this situation, it is also pertinent to obtain a

representative sample of the waste from the production process in order to ensure that

there are no deviations in composition.

6.3 On Site Waste Acceptance Procedures

The control of feedstock quality at an AD facility is a critical part of the successful

operation of the facility. It is vital both in ensuring that the digestion process operates

efficiently and effectively, and maintaining consistent quality of the outputs. Once the

waste material is onsite, and has been emptied onto the reception area, it should

undergo a standardised inspection process, as agreed between both parties.

Operators should develop procedures to deal with the identification, removal and

management of any contamination. A Hazard Analysis and Critical Control Points

(HACCP) required under PAS 110 will include this.

6.4 Standardised Inspection Process

Inspection should occur immediately if reloading and return are an option and as soon

as possible. Otherwise on arrival, the loads should be visually checked and where

possible, confirmation checks should be undertaken (provided it is safe to do so).

A more detailed inspection should take place immediately after off- loading at the AD

facility. During the inspection, every container should be checked to confirm quantities

against accompanying paperwork.

Please note the inspection, unloading and sampling areas should have suitably sealed

drainage systems.

6.5 Identification of Contamination Prior to Treatment

Should the inspection or analysis indicate that the wastes fail to meet documented

acceptance criteria, then these loads should be stored in a dedicated quarantine area

and dealt with in accordance with the contractual specification and site permit

conditions.

Best Available Techniques (BAT) requires operators to have a clear and unambiguous

written procedure in place for the rejection of wastes. This should include tracking and

reporting procedures.



It is however appreciated that issues do exist where it is considered detrimental to

relations between individual stakeholders to reject loads of material and there is a fear

within the industry that this could lead to the suspension or loss of contracts.

6.6 Pre-Treatment - Removal and Management of Contamination

The removal of contamination is an essential requirement for the production of

digestate if it is to meet the PAS 110 specification.

For waste treatment or transfer, the bulk of the characterisation work should have taken

place at the pre-acceptance stage. This means that acceptance procedures when the

waste arrives at the site should serve to confirm the characteristics of the waste. This

should minimise the waiting time for the delivery vehicle.

Measures to deal with acceptable wastes arriving on-site, such as a pre- booking system,

must be in place to ensure that capacity is available.

The typical objectives of feedstock pre-treatment are:

▪ Removing packaging material from food waste (depackaging);

▪ Removing other non-biodegradable materials, which are not of benefit to the

digestion process;

▪ Providing a uniform and correctly sized feedstock;

▪ Ensuring that the material is particle sized correctly in line with the Animal By-

products (ABP) requirements;

▪ Protecting the downstream plant equipment from materials or contaminants that

may cause physical damage; and

▪ Removing materials which may decrease the quality of the digestate.

6.7 Contamination Management Approaches

The increase in food waste collections has led to an increase in the amount of liners,

both bioliners and polyethylene liners, in the feedstock received at AD facilities.

Operators therefore need to employ reliable front end and/or back end contamination

management approaches to ensure (as far as practically possible) that the output

material will comfortably meet or preferably, exceed the thresholds in PAS 110.

6.8 Front End Removal - Depackaging

The use of liners provides a cleaner and more convenient food waste collection method

for householders and encourages the separation of food waste from mixed household

wastes. AD facilities however have encountered difficulties in processing feedstock

containing liners and in many instances have invested in comprehensive separation

technology to remove the bags from the waste stream prior to treatment.

Depackaging technologies operate using basic physical processes such as compression,

shredding, agitation and screening to separate packaging from its contents.

Compression approaches form the majority of those available. Crushing, shredding and

vigorous agitation of the packaged waste provides the initial stage of opening and

removing food waste from its packaging.



This stage is subsequently followed by a series of separation, screening, washing and

bulking operations designed to maximise the quality of the output and separate

packaging material from the organic matter. These technological approaches are

suitable for separating food wastes from paper/card, rigid and film plastics and metal

cans. Belt press technology is designed for the separation of soft products from

packaging such as paper, card, plastic film, lightweight plastic containers or foil as well as

for other industrial uses such as fruit pulping and meat reclamation. Technologies

incorporating screw presses, hydraulic rams and rotating drums are suitable for the

crushing of heavier packaging including steel and aluminium cans and plastic bottles, in

addition to being able to separate the softer materials.

Investment in effective depackaging equipment will reduce the consequences of the

“drag effect” whereby extra organics may be lost throughout the system as a result of

being separated out with plastic contaminants.



Common depackaging machinery is summarised in the following table:

Figure 3: Depackaging Machinery

Details

Turbo

Separator

▪ Flanged inlet, variable speed, beater blades and breakers bars. Various screens

depending upon product size and consistency.

Belt / Drum

Separator ▪ Flexible squeezing belt and rotating perforated drum

Separator

▪ Screw elevator feed. Batch process rotary action, substrate passed through sieves and

the plastic fraction is washed before passing through an eject hatch aided by a

pulsating compressed air blast.

▪ Washed packaging material contains <1% organic fraction.

Shredder and

Pulper

▪ Slow-running shredders. Dissolution of the organic materials in a pulper and

separation of contaminants.

Shredder and

Screen

▪ Feed hopper, 2 screw conveyors, 2 shredders and a separating screen. Material

sprayed with water.

▪ Liquidised food waste runs back down into a hopper, solid waste is discharged at the

top into a container.

Screw Press

▪ Material fed to screw press via filter chute. Conical outlet remains closed until the

internal pressure exceeds the working pressure. Internal pressure drives free

liquids/pastes through perforated screen discharging separated foodstuff into a

hopper.

▪ Packaging is retained and discharged.

Screw Press ▪ Packaging presses operate electro-hydraulically. Material fed manually into supply

funnel or fully automated conveyors. Separated liquid is collected in a large volume

collection trough and discharged by a separate level-controlled pump.

Pulveriser ▪ Materials fed into pulveriser via an infeed hopper. Twin ‘breaker’ shafts comprising

multi-blade breaker knives which contra-rotate, pulverising the packaging and

releasing the contents against an interchangeable breaker bar grille.

Accelerator

▪ Material accelerated within a chamber results in one material hitting another,

releasing contents from the packaging. Process involves no cutting just acceleration

resulting in low operating costs.

▪ Packaging and contraries are then removed. Organic fraction is broken down with

maximum surface area.

Belt Press ▪ Two stages. Packaging opened and pressed flat in a continuous operation then

cleaned in the second stage. Solids in rinsing water circuit removed, packaging ejected

at the end of the sieve drum.



6.9 Back End Removal

It should be noted however that a study undertaken by WRAP4 has suggested that

although a large proportion of contaminants are removed, depackaging alone may not

be enough to remove 100% of the contaminants. Microfibers and larger fragments may

still end up in the digestate.

Depending on the technology, there may be a requirement for floating material such as

plastics to be removed downstream. This is achieved through a number of mechanisms

including through a rotating skimmer. Here, material is forced to the edge of the

digester where it is removed and separated from any entrained digestate. The

separated digestate is returned to the digestion process and the separated solids

disposed of as residual waste.

6.10 External Verification

PAS is a non-statutory document5 and does not set regulatory limit values for the quality

and use of digestates. External verification and quality standards may improve the

management of contamination.

Other European Countries have adopted more pro-active approaches in terms of

managing contamination. In Germany for example, BGK (the Bundesgutegemeinschaft

Kompost (BGK)) has defined general quality standards (the RAL quality label for

compost, digestion products and sewage sludge compost) and established a nationwide

system for external monitoring of composting and digestion plants and products. The

impact of this is the production of a high quality product with low contamination, with

continual monitoring of standards.

The potential use of these standards is discussed further in Section 8.

4 Enhancement and treatment of digestates from anaerobic digestion

5 If the PAS is used in conjunction with the relevant Quality protocol (QP) the regulator recognised the change of status from a

waste to a product.

http://www.wrap.org.uk/sites/files/wrap/Digestates%20from%20Anaerobic%20Digestion%20A%20review%20of%20enhancement%20techniques%20and%20novel%20digestate%20products_0.pdf



7.0 Contractual Arrangements

The operator should ensure that their contractual arrangement with the waste suppliers

clearly sets out how contamination and liner issues will be dealt with. This can be done

using a specification to provide a standard for the quality and types of input materials

that can be delivered for treatment.

This specification should be defined so that it enables the facility operator to produce

marketable digestate compliant with the requirements upon the product.

These might be generated by inter alia:

▪ Licence, environmental permit or other regulatory means;

▪ Quality assurance schemes operated at the facility;

▪ Specifications required of the product; and

▪ Operator desired parameters.

The operator must consider liner types and facility configuration before making

contractual arrangements, creating and agreeing a contractual specification for the

contract duration with the feedstock supplier.

7.1 Input Specification

An input specification will provide guidance on how the input materials delivered

are to be compared to any of the specified quality standards and it defines the

actions to be taken if it is established that the material does not meet the required

standard. Some requirements may also be a requirement of the site’s

Environmental Agency permit.

This specification should:

▪ Have a ‘positive’ list of feedstocks that are acceptable, with descriptions and

definitions. The specification may include a ‘negative’ list of materials that are not

acceptable; Require immediate inspection, if reloading and return are possible, and

as soon as possible;

▪ Agree a methodology to quantify and qualify contamination in waste delivered,

including options to options for a joint inspection if requested. Suggestions for this,

using examples from other technologies and other European Countries, are

presented in Section 8; and

▪ Define the quantity and quality of contaminants that are acceptable, by type. This

should include identification / specification of type(s) of liners, PE or otherwise, in

use. This will depend on the capabilities of the individual facilities depackaging

equipment but should set, at least, maximum permissible amounts of the following:

Total physical contaminants;

Total plastics (including high and low density plastics);

Light plastics (low density plastics e.g. plastic carrier bags); and

Glass (including sharp and rounded pieces).

▪ The setting of these standards will require a great deal of collaboration between the

industry and local authorities but would provide a level playing field of maximum

acceptance levels. Such levels have already been provided for the Composting



Industry. Consideration should be afforded to consultation with such organisations

such as BGK (as defined in Section 7 and Section 8). This is something which could

be achieved and agreed by the industry without the need to request a change the

statutory status of the PAS system.

▪ Outcomes should be recorded electronically on paper and verified with

photographs to allow later review, if required.

▪ Outcomes of inspections should be communicated to the waste supplier as soon as

possible, particularly where there are adverse findings to allow for joint inspections

and possible load retrieval.

In summary, with regard to contamination, the input specification needs to be

designed to achieve the following:

▪ Agree options for contaminated loads, including scaled processing fees, return or

disposal fees etc.;

▪ Agree options (e.g. processing, return or direct disposal) on how to manage

contaminated loads and their associated fees etc; and

▪ Be reviewed at a frequency, that ensures the maximum acceptance criteria specified

continue to be adequate.



8.0 Innovative Approaches

There are a number of innovative approaches that could be used to increase

collaboration between those producing the waste, those responsible for its collection

and the AD operators. The aim of these should be:

▪ Encourage positive behaviour at the household level to ensure the correct liners are

used (and in general decrease contamination in the source segregated food waste);

▪ Encourage waste collection staff to recognise and intercept contaminated food

waste at the kerbside in order to cut down on contaminated loads; and

▪ By implementing the above, reduce the contamination at source, increase the

quality of the output and hence the profitability of the business.

The type of innovative approach will vary according to a number of factors including the

size of the business and their financial ability and appetite to contribute.

In order to provide some ideas of innovative approaches that could be implemented, AD

operators and local authorities have been contacted and in addition a desk study has

been undertaken in order to ascertain examples that are currently being undertaken

across Europe.

8.1 Collaboration between Operators and Local Authorities

The incentives vary in both cost and complexity but include the following:

▪ Production of literature for issue to householders outlining what can be accepted

and highlighting the types and consequences of contamination;

▪ Issue of newsletters to local residents, highlighting improvements and the

environmental benefits associated with this;

▪ Contribution towards the cost of liners: This will only be considered beneficial to

those householders who currently are required to pay for their liners or where the

Local Authority is considering ceasing the free supply of liners as part of its wider

cost saving;

▪ Contribution towards communications campaigns (for example the circulation of bin

stickers and any promotional leaflets);

▪ Sponsorship for local community events;

▪ Provision of grants for local authority environmental improvement schemes;

▪ Provision of grants for local community education or leisure activities;

▪ Sponsorship of awards for individual households (these would be required to be

nominated by the Local Authority). This could take various forms with examples in

other areas including vouchers for education or leisure facilities, vouchers for local

retailers or restaurants, supermarket voucher, loyalty cards which will lead to

voucher or gifts over time; and

▪ Input of all parties in communication campaigns.

The use of any, or indeed a combination of these incentives will help raise the profile of

the industry as well as acting as a “carrot” for local authority and householder

participation in behavioural change. This will ultimately lead to less contamination at the

outset, the use of the correct liners and ultimately a higher quality output, whilst also

fulfilling corporate responsibility roles.



There will however be a need to ensure that the bureaucracy associated with any of the

schemes can be kept to a minimum in order to ensure that any gains are maximised.

8.2 Innovation in Future Contracts

In addition to innovative approaches from AD operators, there is also the potential for

innovation to be introduced into future contracts to deal with contamination. This would

need to have buy-in from the Contracting Authorities but would, if introduced as a

condition of contract, lead to a level playing field for the industry. These include the

following:

▪ Quantification of permissible contaminants;

▪ Introduction of the ability to include financial penalties for repeated contamination

events (the compensation for this could be negotiated between the two parties);

▪ Introduction of profit share agreements associated with decreased contamination;

and

▪ The introduction of variable gate fees (albeit that there must be a recognisable way

of measurement which will not be financially restrictive to any party).

In terms of quantification of contaminants, a number of mechanisms have been

suggested by current operators and collated through a desk study of what happens in

other European Countries. What is important to remember however is that, at the

current time, there is no definitive figure for measuring contamination and therefore

one system will not “fit all”. The following are therefore to be treated as guidance

purposes only.

8.2.1 Visual Scoring System

This has been suggested as a relatively easy system to implement and control and

would act as a good potential mechanism between waste producers and AD operators.

The system would consist of a number of standard photographs of input waste, each

with differing levels of contamination present. For ease of this report, these could be

titled A to D with photograph A having little or no contamination graded down through

photographs B and C with photograph D having heavy contamination, which would be

therefore unacceptable to the facility. The Organics Recycling Group (ORG) have

produced guidance on visual scoring which includes example photographs.

This scoring could be used to ascertain acceptable waste streams during the input

specification and the payment mechanism between the parties adjusted according to

the wastes received. This system however would require careful control over input

wastes and would require careful inspection and testing of input loads.

It would be extremely beneficial if the permissible contaminants could be quantified in

order to be more understandable outside the immediate operator environment. For

example, calculations of 3% of plastic material within a sample would appear to be a

very small load however, when this equates to approximately 3,500 bags/tonne, it

provides a much more realistic and visual explanation of the issues.



8.2.2 Standardised Measurement System

There are a number of standardised measurement systems in use across Europe for

determining physical contaminants for the biowaste industry. Although these are not

completely transferrable in all cases, they have the potential to act as a starting point for

AD operators as the UK moves towards minimising contamination.

One such system is the Renewable Energy Association’s Biofertiliser Certification

Scheme (BCS) which is part of the overall Renewable Energy Assurance Limited (REAL)

Scheme. This has been created for the purpose of certifying biogas plants against the

PAS110 standard and Quality Protocol (QP) for the production and use of Quality

Outputs from the anaerobic digestion of source-separated biodegradable waste.

The broad approach followed by the Certification Scheme is as follows:

▪ A scheme administrator Renewable Energy Assurance Limited (REAL) develops and

implements the scheme rules and maintains the register of certified participants;

and

▪ One or more independent Certification Body(ies) who certify plants to confirm that

they are operating in accordance with the scheme rules and appropriate standards.

Further information on this scheme, including how to join and details of the training and

guidance available to prepare AD operators for certification is available at: Email:

[email protected] or Telephone: 0207 981 0875

There is a need within the UK however for additional criteria to be included which

provides further consideration of the quality factors associated with the materials. As

previously stated, Germany introduced a RAL Quality label for digestion residuals in

2000 (RAL GZ 246). Within Germany at the current time, there are over 67 digestion

plants taking part in the quality assurance system and have applied for the RAL quality

label.

The quality requirements for this scheme, which could be considered within the UK, are

summarised as follows:

Process Requirements and Suitable Input Materials

▪ Positive list in accordance with ABP Regulation, biowaste ordinance and fertiliser

regulation for digestate products from biowaste;

▪ Operation control by plant visits of independent quality managers; and

▪ Control by independent sample takers and by declaration in analysis report.

Independent Analysis and Declaration of Product Quality

▪ (2) 4- (10) 12 times a year according to the quality guidelines and the amount of

input material;

▪ Control and sanctions by an independent quality committee; and

▪ Certification with product declaration according to the fertilizer and regulation.

Application Requirements

▪ Application requirements based on the biowaste ordinance and fertiliser regulation

mailto:[email protected]



for digestate products from biowaste; and

▪ Application requirements due to good practical use.

Using a similar stance, the Organics Recycling Group (ORG) has provided operators with

a protocol and methodology to measure the levels and types of physical contaminants

delivered in loads of biowaste (protocol to measure physical contaminants in biowastes).

Although developed for the composting industry, there is a great deal of good practice

which could be interpreted for the AD industry and therefore it is considered beneficial

to include within this guidance. The ORG protocol to measure physical contaminants in

biowastes’ provides guidance on how the input materials delivered to a composting

facility shall be compared to the input quality standard and defines the actions to be

taken if it is established that the material does not meet the required standard. The

document provides operators with a methodology to measure the levels and the types

of physical contaminants in delivered loads of biowastes. This enables operators to:

▪ Ascertain and monitor contamination levels in loads of biowaste delivered to

organics recycling facilities;

▪ Obtain evidence to support the specification or revision of maximum acceptance

criteria in contractual arrangements with suppliers;

▪ Check compliance with the acceptance criteria specified within existing contractual

arrangements;

▪ Provide biowaste suppliers with feedback on specific collection rounds that are

routinely causing issues with respect to contamination; and

▪ Justify the implementation of a differential pricing mechanism based on the results

of the assessment carried out.

The methodology for achieving assessment of levels of contamination is based on a

methodology implemented by the Italian Composting Association (CIC) and describes:

▪ How a representative sample should be obtained from a load of biowaste delivered

to the facility;

▪ How the sample should be sorted to differentiate between bio treatable and non-

bio treatable fractions; and

▪ How the results of the assessment should be provided.

ORG recognise within the protocol that this methodology can be used to assess

contaminants in AD facilities through the identification and use of difference categories

of physical contaminants. Further information on the ORG system can be found here

http://organics-recycling.org.uk/page.php?article=2334&name=AfOR+releases+its+protocol+to+measure+physical+contaminants+in+biowastes



9.0 Improved Communication & Consultation

Effective communication and consultation is considered key to the successful operation

of a waste management facility, especially when the waste producers and collectors are

distinct from the operators of the facility.

The aim of this section is to provide some guidance on improving communication and

consultation, with the overall objective of ensuring that a high quality product can be

produced in the most cost effective and sustainable manner.

9.1 Development of Strategic Partnerships

Consultation with a number of AD operators, groups and Local Authorities has

suggested that the formation of Strategic Partnerships facilitate a good working

relationship between all parties.

A Strategic Partnership has been described as a formal alliance between 2 or more

enterprises, usually formalised by 1 or more business contracts. Within this Partnership,

parties agree to share finance, skills, information and other resources in pursuit of

common goals.

This is considered particularly useful in the AD industry, as often AD operators do not

have the opportunity to interact directly with the waste producers. Within the UK, for

example, our consultation has alerted us to the fact that there may be waste collection

representatives, transport companies, waste transfer stations in the chain before the

waste reaches the AD operator. Within this chain, there can understandably be a

challenge in the dissemination of information between all parties. The formation of a

partnership approach would aid in this manner and ensure that all stakeholders are

aware of their responsibilities and obligations.

This would also help to alleviate any potential issues where it is considered as purely

one party’s responsibility to deal with quality of the materials or contamination, often

with no financial detriment to others.

9.2 Regular Meetings

Regular meetings between each of the interested stakeholders is considered to be a

useful mechanism of continuing communications. The timeframes for these will be

project dependant but it has been suggested that quarterly meetings may be useful.

This meeting could be used for the identification and remediation of any issues,

including contamination issues and will be a good forum for ensuring that all parties are

adhering to their aspects of the contract and any associated input specification. Regular

meetings would be useful for those operators who are in a chain of treatment, and are

therefore not in direct contact with the waste producers. In this instance, it would be

beneficial for a representative from each of the interested stakeholders to be present as

all will have different agendas.

These meetings should be properly minuted and associated actions disseminated to all

parties. The meetings could include the following:

▪ The types of liners which cause problems in the anaerobic digestion process for the



AD plant and how the local authority can help prevent these entering the food waste

stream;

▪ The percentage of liners received from a particular local authority and percentage of

liner types causing problems (or not, as the case may be);

▪ New innovations in bag liners, which may be more suitable for the AD process, and

associated costs of such liners for the local authority;

▪ What types of liners other local authorities/AD plants are using and where they

sourced those liners from;

▪ Technology innovations within the AD plant which may mean that certain types of

liners can be accommodated more easily in future;

▪ Possible ways for a number of local authorities who supply a particular AD plant to

obtain economies of scale in the purchase of suitable liners; and

▪ Forthcoming local authority food waste communications campaigns and the

possibility for the AD plant to comment on any proposed communication before the

campaign is launched.

9.3 Community Events

The hosting of community events is considered an effective way of raising the profile of

the industry and showing consumers, not only the end products of their waste, but also

highlighting the importance of minimising contamination at source. Operators have

reported benefits of engaging with a number of community groups in this manner and

would suggest that this is an effective way of disseminating information to the wider

community. Events could take a number of different forms from illustrated talks outside

of the site to on-site tours and events. Hosting events with Local Authorities and their

collection service crews is another effective to way to promote the importance of input

quality.

9.4 Production of Literature

For the AD Operator, generating enough biogas to make the operation financial viable and

producing digestate of the highest quality, as a result of good process management is

key to the success of their operation. In order to achieve this, it is vital that they set clear

parameters of the feedstock they can accept, including which type of liners their AD

plant can process. To help clarify their position on liners, AD operators should consider

producing an A5 size leaflet outlining the specification of the liners their plant can deal

with. This should be circulated to all local authorities who supply feedstock to that AD

plant and should be available on the AD Operator’s website. The information on this

leaflet should be discussed at any pre-contractual meeting with a local authority who is

planning to introduce a food waste collection scheme.

This would help local authorities ensure they are purchasing the correct liners to supply

residents with and which will comply with the AD plant.

If the AD Operator is in a position to suggest suppliers of liners, this could be helpful to

the local authority to ensure they are purchasing the correct liners from the outset. In

addition, it would benefit AD Operators to have some input, or at least comment on, any

food waste communication leaflet provided by the local authority to their residents. It

may be the case that the AD operator can assist with the wording in this section to

better improve overall uptake of the scheme.



9.5 Local Shops/Supermarkets

It is quite often the case that householders have to buy liners for their food caddy in

local shops/supermarkets. In this case, AD operators would be advised to ask to speak

to the general manager of these stores and explain their position on the preferred type

of liner their plant can process. If the AD operator can ensure that the local shops/

supermarkets are supplying the correct bag for their system then this can only be of

benefit to both the AD operator, the householder, the supermarket and the local

authority.



10.0 Staff Involvement & Training

Staff training and involvement can take a number of different forms. What is important

though is that it is all encompassing and has participation and buy in from senior

management as well as those operating “on the ground”.

Due to the importance of buy in from all sectors, whenever possible training should

include both the AD operators and those supplying the waste, i.e. for household food

waste- local authorities and where necessary waste collection authorities. It would also

be an effective mechanism to ensure that all parties were aware of their responsibilities

in collecting and treating a waste which produces a high quality end product, with

minimal contamination. A reduction in contamination from the outset, combined with

the systems within the AD facility will undoubtedly result in a higher quality product.

Signage should be clearly displayed within both the waste acceptance areas and within

the operational areas in order to remind staff (and highlight to customers where

relevant) of their roles and responsibilities in terms of minimising contamination.

Staff training can take various forms, and should be adapted according to the desired

audience. Employers can choose from “on the job training” and “off the job training”

depending on their specific objectives.

Health and Safety needs to be given priority during these training sessions. Employees

need to be sure of how to remove contaminants during the AD process without

compromising the health and safety of themselves or anyone around them.

One further important issue to take into consideration is to ensure that employees are

aware of why they are undertaking this training. The training sessions do therefore need

to provide some focus on the importance of reaching standards for reaching standards

and business continuity. It may be useful to use feedback from customers on the quality

of the organic output produced (i.e. include details of any contaminants/types of

contaminants still present).

Finally, it will be extremely beneficial for employers to follow up training sessions. Not

only will this act as a timely reminder on requirements and expectations, but can also be

used to highlight improvements in the quality of output produced.



11.0 Definitions

The following definitions are used in this guidance:

Figure 4: Definitions

Anaerobic

Digestion (AD)

Process of controlled decomposition of biodegradable materials under

managed conditions where free oxygen is absent, at temperatures suitable

for naturally occurring mesophilic or thermophilic anaerobic and facultative

bacteria species that convert the inputs to biogas and whole digestate.

Aerobic Oxygen source available

Anaerobic No oxygen source available

Anaerobic Digestion

Quality Protocol

(ADQP)

End of waste criteria for the production and use of quality outputs from

anaerobic digestion of source segregated biodegradable wastes.

Biodegradable

(liner)

Those liners which can be broken down into its constituent monomers and

metabolised through the action of naturally occurring micro-organisms, such

as bacteria and fungi, over a period of time.

Biogas Gas generated by an anaerobic digestion process. Typically composed of 60%

methane and 40% carbon dioxide.

Compostable

(liner)

Those liners which are capable of undergoing biological decomposition

breaking down into carbon dioxide, water, inorganic compounds, and

biomass, at a rate consistent with known compostable materials

Digestate, Fibre Fibrous fraction of material derived by separating the coarse fibres from the

whole digestate.

Digestate, Liquor Liquid fraction of material remaining after separating coarse fibres from whole

digestate.

Digestate, Whole

The residue resulting from the anaerobic digestion of biodegradable materials.

Whole digestate may be separated into liquor and fibre fractions, referred to as

liquid and solid digestate respectively.

Dry solids (ds) Measure of solids content within the digestate. Defined as the % of mass

remaining after drying at 105°C.

Moisture content Measure of water content within the digestate. Defined as the % of mass lost

after drying at 105°C.

Separated fibre Fibrous fraction of material derived by separating the coarse fibres from the

whole digestate.

Separated liquor Liquid fraction of material remaining after separating coarse fibres from whole

digestate.

PAS 110

Publicly Available Specification 110, which is the British Standards Institution’s

specification for whole digestate, separated liquor and separated fibre derived

from the AD of source-segregated biodegradable materials, published in

February 2010 and revised in 2014.

www.wrap.org.uk/organics

industry guidance: dealing with household food waste at ad ... guidance management of … · food...

Documents