advanced biological treatment of municipal solid waste · municipal solid waste (msw) is waste...

Advanced Biological Treatment ofMunicipal Solid Waste

www.defra.gov.uk

Contents

Preamble 1

1. Introduction 2

2. How It Works 3

3. Markets And Outlets For The Outputs 11

4. Track Record 14

5. Contractual And Financing Issues 17

6. Planning And Permitting Issues 19

7. Social And Perception Issues 26

8. Costs 27

9. Contribution To National Targets 28

10. Further Sources Of Information 30

11. Glossary 32

Prepared by Enviros Consulting Limited on behalf of Defra as part of the New Technologies Supporter Programme.

We acknowledge support from the Department for Environment, Food & Rural Affairs (Defra), the Department ofCommunities & Local Government (DCLG), the Environment Agency (EA) and BeEnvironmental Ltd.

This Document has been produced by Enviros Consulting Limited (Technical Advisors) on behalf of Defra to provideassistance to Local Authorities and the waste management market generally through awareness raising of the keymunicipal waste management options for thediversion of BMW from landfill. The Document has been developed ingood faith by the Advisors on behalf of Defra, and neither Defra not its Advisers shall incur any liability for any actionor omission arising out of any reliance being placed on the Document by any Local Authority or organisation or otherperson. Any Local Authority or organisation or other person in receipt of this Document should take their own legal,financial and other relevant professional advice when considering what action (if any) to take in respect of any wastestrategy, initiative, proposal, or other involvement with any waste management option or technology, or beforeplacing any reliance on anything contained therein.

Any interpretation of policy in this document is that of Enviros and not of Defra or DCLG.

Crown copyright, 2007

Cover image courtesy of Greenfinch Ltd

Preamble

This Waste Management Technology Brief,updated in 2007, is one of a series ofdocuments prepared under the NewTechnologies work stream of the Defra WasteImplementation Programme. The Briefsaddress technologies that may have anincreasing role in diverting Municipal SolidWaste (MSW) from landfill. They provide analternative technical option as part of anintegrated waste strategy, having thepotential to recover materials & energy andreduce the quantity of MSW requiring finaldisposal to landfill. Other titles in this seriesinclude: An Introductory Guide to WasteManagement Options, Mechanical BiologicalTreatment, Mechanical Heat Treatment;Advanced Thermal Treatment; Incineration,Renewable Energy and Waste Technologies,and Managing Outputs from WasteTechnologies.

These waste technologies can assist in thedelivery of the Government’s key objectives,as outlined in The Waste Strategy for England2007, for meeting and exceeding the LandfillDirective diversion targets, and increasingrecycling of resources and recovery of energy.

The prime audience for these Briefs are localauthorities, in particular waste managementofficers, members and other key decisionmakers for MSW management in England. Itshould be noted that these documents areintended as guides to each generictechnology area. Further information can befound at the Waste Technology Data Centre,funded by the Defra New TechnologiesProgramme and delivered by theEnvironment Agency (www.environment-agency.gov.uk/wtd). This brief deals withbiological treatment technologies, which canbe used to treat source segregated organicwaste or mechanically separated organicwaste. In the latter, ABT is a component of a

Mechanical Biological Treatment (MBT)process, on which there is a separateTechnology Brief. Information on thecollection and markets for source segregatedmaterials is available from Defra and fromROTATE (Recycling and Organics TechnicalAdvisory Team) at the Waste & ResourcesAction Programme (WRAP).

The Defra New Technologies DemonstratorProgramme has provided nine projects aimedat proving the economic, social andenvironmental viability (or not) of a selectionof waste management technologies. Forinformation on the demonstrator projects seethe Defra website or [email protected].

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1. Introduction

Municipal Solid Waste (MSW) is wastecollected by or on behalf of a local authority.It comprises mostly household waste and itmay include some commercial and industrialwastes. Historically, the quantity of MSW hasrisen year on year1, presenting a growingproblem for local authorities particularly aslegislation, now limits (by implication2) theamount of mixed MSW that can be sent tolandfill, becomes more stringent over time.

One of the guiding principles for Europeanand UK waste management has been theconcept of a hierarchy of waste managementoptions, where the most desirable option isnot to produce the waste in the first place(waste prevention) and the least desirableoption is to dispose of the waste to landfillwith no recovery of either materials and/orenergy. Between these two extremes thereare a wide variety of waste treatment optionsthat may be used as part of a wastemanagement strategy to recover materials(for example furniture reuse, glass recyclingor organic waste composting) or generateenergy from the wastes (for example throughincineration, or digesting biodegradablewastes to produce usable gases).

At present more than 62% of all MSWgenerated in England is disposed of inlandfills3. However, European and UKlegislation has been put in place to limit theamount of biodegradable municipal waste(BMW) sent for disposal in landfills4. TheLandfill Directive also requires waste to bepre-treated prior to disposal. The diversion ofthis material is one of the most significantchallenges facing the management ofMunicipal Solid Waste in the UK.

There are a wide variety of alternative waste

management options for dealing with MSWto limit the residual amount left for disposalto landfill. The aim of this guide is to provideimpartial information about the range oftechnologies available referred to asAdvanced Biological Treatment (ABT). Thesetechnologies include in-vessel composting andanaerobic digestion and are part of a rangeof processes currently being assessed andinvestigated through the New Technologieswork stream of Defra’s Waste ImplementationProgramme (WIP). Further information can befound on the Waste Technology Data Centre,funded by the Defra New TechnologiesProgramme and delivered by theEnvironment Agency (www.environment-agency.gov.uk/wtd).

The role of ABT technologies, particularyanaerobic digestion (AD) was emphasised inthe Waste Strategy for England 2007. ABTcan be used to process source segregatedwaste to produce quality compost/digestateor it can be the biological component ofMechanical Biological Treatment (on whichthere is a separate Technology Brief). ABTstill has a limited track record in the UK fortreating the organic fraction of mixed,residual MSW. UK case studies are providedwithin this brief, including those from theDefra New Technologies DemonstratorProgramme. The aim of this document is toraise awareness of these types of technologiesand present the most current informationregarding their implementation.

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1 This is now showing signs of slowing down and in some areas waste arisings are falling, and indeed in 2005/6 there was a 3% fall nationally.However, this may be partly explained by other factors occurring in that particular financial year

2 Targets pertain to the biodegradable fraction3 Results from WasteDataFlow http://www.defra.gov.uk/environment/statistics/wastats/bulletin.htm4 The Landfill Directive, Waste and Emissions Trading Act 2003 and Landfill Allowances Trading Scheme Regulations

Main Heading

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2. How it works

2.1 Introduction

This Brief describes the biological treatmentof biodegradable municipal waste. Some ABTtechnologies have already been used in theUK for source segregated waste, for greengarden waste and food waste; and in otherindustries such as for sewage sludgetreatment and in agriculture. ABT processescan also be used to treat the biodegradablefraction mechanically separated from mixed,residual MSW at a Mechanical BiologicalTreatment (MBT) facility, although it still has alimited track record in the UK.

This guide is designed to be read inconjunction with the other WasteManagement Technology Briefs in this seriesand with the case studies provided on theWaste Technology Data Centre. Otherrelevant sources of information are identifiedthroughout the document.

2.2 The Process

ABT technologies are designed andengineered to control and enhance naturalbiological processes, and as such can only acton biodegradable organic materials. ABTprocesses can treat either source segregatedmaterials or those mechanically separatedfrom a mixed waste stream into abiodegradable, organic rich fraction.

Source segregated collections will provide acleaner organic stream, but on their own areunlikely to capture sufficient organic materialto achieve the required level ofBiodegradable Municipal Waste (BMW)diversion from landfill. Therefore, additionaldiversion of BMW will be required throughprocesses such as MBT or thermal treatmenttechnologies in the longterm.

In line with the EU Landfill Directive andnational recycling targets, the function ofABT facilities includes the:

• Diversion from landfill through theproduction of compost (or a digestate) thatcan be safely applied to agricultural landfor ecological benefit5;

• Pre-treatment of waste going to landfill, toreduce its biodegradability, if unsuitablefor application to land;

• Diversion of biodegradable MSW going tolandfill if using ABT within an MBT by:

- Reducing the dry mass of BMW prior tolandfill;

- Reducing the biodegradability of BMWprior to landfill;

- Stabilisation into a compost-like output(CLO)6 for potential use on land(although markets likely to be limitedwhere mixed waste is the source);

- Deriving a combustible biogas from theorganic waste for energy recovery;and/or

- Drying materials to produce a highcalorific organic fraction for use as a fuel(Refuse derived fuel RDF).

2.3 Advanced biological treatment (ABT)Options

Advanced biological treatment is concernedwith the use of relatively new technologies totreat biodegradable wastes using tightlycontrolled biological processes. Food andgreen wastes are suitable input materials forthese technologies. Other biodegradablematerial, such as card, paper and wood canbe treated, however they take a longer timeto degrade and input levels are limited tooptimise the processing.

2. How it works

5 Compost that has been produced from source segregated waste is currently only allowed to be applied to agricultural land6 Compost-like Output (CLO) is also sometimes referred to as ‘stabilised biowaste’ or a soil conditioner; it is not the same as a source-

segregated waste derived ‘compost’ or ‘soil improver’ that will contain much less contamination and has a wider range of end uses

2. How it works

4

All biological waste treatment processesinvolve the decomposition of biodegradablewastes by living microbes (bacteria andfungi), which use biodegradable wastematerials as a food source for growth andproliferation.

Microbes excrete specialised enzymes thatdigest biodegradable waste constituents (e.g.cellulose and other complex polysaccharides,proteins and fats) into simple nutrients (e.g.sugars, amino acids, fatty acids), which theyabsorb. As the microbes grow and proliferatea significant proportion of this is convertedinto heat, carbon gases and water, which canresult in large losses in mass during biologicaltreatment.

There are two main types of conditions inwhich such microbes live, and therefore twomain classes of biological processes used totreat biodegradable waste:

• Aerobic – in the presence of oxygen; and

• Anaerobic – in the absence of oxygen.

Aerobic composting processes

During aerobic decomposition, biodegradablematerial is decomposed into carbon dioxide(CO2), water (H20), and heat throughmicrobial respiration in the presence ofoxygen (Figure 1) leaving a stabilised residualsolid material, compost7. If source segregatedbiodegradable material is treated, oxygen isoften supplied passively through the presenceof air or through mechanical turning. In MBTsystems, air is usually blown or drawnthrough material, to speed up the dryingand/or decomposition of the material.

Figure 1: Aerobic Decomposition

Aerobic processes are relatively dry and usedfor materials with high solids content (amoisture content of around 60% isconsidered optimal). These materials musthave a good porous physical structure toallow the air to pass through the material.The right balance of carbon to nitrogen (andother mineral nutrients) is also required.

Accelerated aerobic processes require a netinput of energy to supply the oxygenrequired. A large amount of biologicallyproduced heat is created as microbes respire,and are associated with high processingtemperatures of 60 – 70°C. High temperatureshave the advantage of killing potentiallypathogenic organisms in the waste(sanitisation), and can also be used to drymaterial.

As the process progresses biodegradablematerial is converted into carbon dioxide,water, and heat, which are lost to theatmosphere. The material remaining consists

7 Stabilised is the degree of processing and biodegradation at which a) the rate of biological activity under favourable aerobic biodegradationhas slowed ; b) microbial respiration will not revive significantly until environmental conditions are altered

HeatCarbonDioxide

Water

Biodegradablefraction

Compost

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2. How it works

of a mixture of non-biodegradable materials;recalcitrant organics; microbes and microbialremains; and a complex of decomposition by-products called humus. This stabilised anddried mixture is known as compost.

Anaerobic digestion (biogas) processes

During anaerobic digestion (AD)biodegradable material is converted intomethane (CH4) and carbon dioxide (togetherknown as biogas), and water, throughmicrobial fermentation in the absence ofoxygen (Figure 2), leaving a partiallystabilised wet organic mixture.

AD is ether a ‘wet’ process used for materialswith moisture contents more than ?85% or a‘dry’ process used for materials with moisturecontents ?80%. Anaerobic processes requireless energy input than aerobic compostingand create much lower amounts ofbiologically produced heat. Additional heatmay be required to maintain optimaltemperatures but the biogas producedcontains more energy than is required i.e. theprocess is a net producer of energy.

As the process progresses biodegradablematerial is converted into a combustible gasknown as ‘biogas’ primarily consisting of amixture of methane and carbon dioxide.Biogas can be burned for heat and/orelectricity production. The material remainingconsists of a wet solid or liquid suspension ofnon-biodegradable materials; recalcitrantorganics; microbes (biomass) and microbialremains; and decomposition by-products. Thispartially stabilised wet mixture is known as‘digestate’.

This wet mixture can be dewatered into itssolid and liquid fractions. Sometimes these 2fractions may both be referred to as‘digestate’, but for clarity they will be

referred to as digestate and liquor in thispublication.

Figure 2: Anaerobic Digestion

2.4 Aerobic (composting) technologies

Aerobic treatment (composting) technologiescome in a range of designs. All systems aredesigned and engineered to control andoptimise the biological stabilisation,sanitisation, and/or, in some cases, drying ofbiodegradable materials.

These processes can last anywhere from a fewdays to 8 or more weeks depending on thedegree to which the material is to bestabilised. For example, when the purpose ofthe process is to dry material prior tomechanical separation in an MBT facility, theprocess can be very short. If material is beingstabilised prior to its use as compost,compost-like-output or disposal to landfill, anumber of weeks processing will be required.

The technologies described here are allenclosed, either in buildings and/orspecifically designed vessels (e.g. tunnels,drums, or towers) and are typically known asin-vessel composting (IVC). The techniquesused to control the supply of oxygen requiredby the process are the mechanical agitation

Biogas

Heat fromprocess

Water

Biodegradablefraction

Digestateand liquor

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of waste (turning) and/or blowing or suckingair through the waste (forced aeration)offering differing levels of process controland automation. Two methods of materialflow are offered: batch or continuous input(see Table 1).

Table 1: Technology Options

Tunnels

Tunnel composting units are large-scalerectangular vessels employing forced aerationsystems. They can be built as permanentstructures constructed from concrete andsteel, or more temporary using mobileconcrete push walls and/or special fabricsstretched over steel frames. Tunnels may besingle or double ended for loading andunloading, and may be fitted with retractableor opening roofs to help load or unload.

Typically, composting tunnels are used toprocess materials in single batches (all-in/all-out), although some systems operate on acontinuous flow using specially designedmechanical systems such as moving floors,rotating shafts, and augers, to move thematerial through the tunnel. Tunnels can befilled manually using wheeled loading shovelsor using specialised filling equipment, such asconveyors.

Aeration is achieved by blowing and/orsucking air through a slatted floor, perforatedpipe-work cast into the tunnel floor, orspecial aeration channels on the tunnel floor.Oxygen and temperature are controlled byadjusting the amount of cool fresh airentering the tunnel, and the rate of air flow.Odorous gases are controlled by passingexhaust air through water and/or chemical airscrubbers, bio-filters, and thermal or ozonebased oxidising units.

Moisture may be controlled by pumpingprocess water or fresh water through a spray-bar positioned in the roof of the tunnel ontomaterial being processed.

Vertical composting towers and silos

Material is fed on a continuous basis into thetop of a sealed tower or silo, and is processedas it moves vertically through the vessel. Thesesystems may consist of a number of vesselswith a single compartment, or a single largervessel with several compartments (or levels).

The rate at which material moves through thesystem is controlled by the rate at whichfinished processed material is removed fromthe bottom of the vessel. In singlecompartment systems, once the material hasundergone the required processing time, it isremoved from the bottom on the vessel (orcompartment) using augers or scraping arms.

2. How it works

System MaterialFlow

Aeration Method

Tunnels Batch Forced aeration

Forced aeration andmechanical agitation

Continuous Forced aeration


Verticaltowers/silos

Continuous Passive aeration

Forced aeration


Rotatingdrums

Continuous Mechanical agitation


Housed bays,piles orextended-beds

Batch Mechanical agitation

Forced aeration,mechanical agitation

Continuous Mechanical agitation

Forced aeration,mechanical agitation

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2. How it works

Many tower/silo systems rely on passiveaeration, but some systems also use forcedaeration.

Agitated bays, piles and extended-beds

Organic material is fed into a large enclosedbuilding for processing. The material is eitherplaced in long concrete-walled bays, piles(windrows), or extended-beds (‘mattresses’).

Material is turned with specialist turningmachines comprising rotating drums withtines, augers, or elevated-face conveyors.Turners can be mounted on top of bay walls,or driven through the bay or on the floor ofthe processing building. Unmanned remotecontrolled turners can also be used,consisting of large bucket-wheels or augerssuspended from mobile gantries in the roofof the processing building.

During the turning process material can bemoved along the length of a bay orprocessing building in a continuous flowfashion. In some cases, these systems areoperated as a batch process.

In many cases, the floor of the processingbuilding is also fitted with a forced aerationsystem, often using negative pressure

(suction) to prevent odours escaping as wellas improving working conditions inside thebuilding.

Rotating drums

This is usually a continuous process, wherematerial is fed into a large, rotating drum.The material is mixed and aerated as it passesalong the drum. Material is agitated andmoved along the length of the drum bymeans of specially designed baffles and tinessituated in its walls. Some systems alsoemploy forced aeration rather than relyingon passive air flow alone.

The mechanical action of rotating drums isoften used to split refuse bags, reduce wasteparticle sizes, and dry waste materials. Theycan be used in this way as a pre-treatmentalternative to waste shredding, to aidmechanical sorting. They can also be used tostabilise and sanitise pre-sorted waste.

Bio-drying

When the composting technologies describedabove are used to dry waste, this is usually aspart of a pre-treatment process, e.g. in anMBT plant, and is often referred to as ‘bio-drying’. The concept of bio-drying is to forceair through the hot biologically active wasteto dry it quickly. Drying makes the wastemore amenable to mechanical separationand increases its calorific value if used as afuel. This also reduces the mass of waste andpartially reduces its biodegradable content.Some energy is consumed in drying thematerial and negates to some extent theenergy gained through drying the waste.

2.5 Anaerobic digestion (biogas)technologies

Anaerobic digestion (AD), also known asbiogas technologies, are designed andengineered to control and optimise the

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2. How it works

biological digestion of biodegradablematerials to produce methane gas for energyproduction. The technologies are, by theirnature, enclosed, using specifically designedvertical and/or horizontal vessels,interconnecting pipe-work, mixers,macerators and pumps.

AD processes last around two to three weeksdepending on the ease and degree to whichmaterials are converted into biogas and thetechnology used. For example, for wastecontaining a larger amount of woody (highlignin content) material, longer residencetimes will be required to achieve the desiredbiogas production.

There are two main classifications of ADtechniques: ‘wet’ and ‘dry’ (Table 2). Inessence, ‘wet’ AD systems process more liquidmaterials (?85% moisture), whereas ‘dry’ ADprocesses are used to treat drier materials(?80% moisture) ranging from thick slurry toa wet solid. Waste feedstock is mixed andmacerated with a large proportion of processeffluent and/or fresh water to prepare thewaste; giving it the moisture and flowproperties required.

Table 2: AD (biogas) Technology options

‘Wet’ AD technology

‘Wet’ AD systems used to treat municipal solidwaste have been adapted from wellestablished systems used to treat wastewatertreatment plant biosolids. The digestionprocess takes place in sealed vertical tanks(digesters) that are usually continuouslymixed to maximise contact between microbesand waste. Mixing can be achieved usingmechanical stirring devices, or by recirculatingbiogas or waste through the digestion tank.Transfer of material between several tanks isachieved through pumps. This type of wetsystem is better suited to feedstocks that arereadily converted to liquid e.g. food wastes.

In some ‘wet’ AD systems the wastepreparation stage can be used todecontaminate mixed residual MSW byremoving heavy and light contaminantsthrough wet gravimetric separation.

‘Dry’ AD technology

‘Dry’ systems use plug flow reactor designs.This approach involves adding fresh wasteand/or partially fermented waste into oneend of the reactor while fully digestedresidue is extracted from the other. Drytechnologies can comprise vertical orhorizontal tanks. Vertical tanks rely on gravityto move material through the system,whereas horizontal systems use specialisedaugers or baffles. A potential advantage ofthe dry system is that it can tolerate higherlevels of physical contaminants.

Operating temperatures

AD technologies can be operated atmoderate (mesophilic: 30 – 40°C)temperatures or high (thermophilic: 50 –60°C) temperatures. ‘Dry’ AD processes lendthemselves to thermophilic operation due tohigher solids content and greater biological

Wet or Dry Operating Temperature Process Stages

Wet (lowsolids)

Mesophilic Single

Multiple

Thermophilic Single

Multiple

Dry (highsolids)

Mesophilic Single

Multiple

Thermophilic Single

Multiple

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2. How it works

heat production. ‘Wet’ AD processes can beoperated at either temperature, but are mostcommonly mesophilic. In mesophilic systems,a pasteurisation unit is used to heat thematerial before or after digestion to achievesanitization.

Single step and multiple step processes

AD processes can be single step processeswhere all the waste is placed into a singledigestion stage/vessel, or a multiple stepprocess using vessels to optimise differentstages of the process. Multiple step processesoften involve a separate hydrolysis stage,which can be aerobic or anaerobic, tobreakdown complex organic material intosoluble compounds. This is followed by ahigh-rate biogas production stage.

Some case study examples are described inSection 4, and further information on theseand additional specific examples can beobtained from the Waste Technology DataCentre.

Biogas

Biogas produced during anaerobic digestionis primarily composed of methane (typicallyranging between 50 – 75%) and carbondioxide, as well as smaller quantities of othergases including hydrogen sulphide. Biogas isalso water saturated (100% humidity).

The amount of biogas produced using AD willvary depending on the process design, such asretention times and operation temperature,and the volatile solids (organic matter)content of the feedstock, i.e. the compositionof the waste inputs.

Biogas is stored in large vessels prior to its useon or off site. Biogas can be used in a numberof ways (see Section 3.3), but is usuallyburned to produce heat and electricity using

some form of generator. Some electricity isused by the plant, but any excess electricityproduced can be sold and exported via thelocal electricity distribution network. Excessheat can also be used locally, in a districtheating scheme or by a neighbouringcommercial or industrial facility.

Digestate and liquor

Due to the high moisture content of thewaste material entering the process, and thebreakdown of solids during digestion,digestate can have a high moisture contentupon leaving the process. The materialproduced is kept in a storage tank and can bemechanically pressed into its solids (digestate)and liquid (liquor) fractions.

The dewatered digestate may be used directlyon land as a soil amendment provided itmeets appropriate regulatory standards (seeSection 3), or aerobically treated to produce acompost (if from source segregated material)or a compost-like output (if frommechanically separated material). Someliquor may be recycled in the AD process towet incoming waste; used directly on land asa liquid fertilizer due to its valuable nitrogencontent (provided it meets appropriate

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2. How it works

regulatory criteria); or used to maintainmoisture during the aerobic treatment of thedigestate. Alternatively, if no other route isavailable, the liquor may be treated anddischarged in accordance with permitrequirements.

2.8 Energy balance benefits andfeedstock issues

Although IVC and AD treat similar wastes,they are in fact complimentary and notcompeting technologies. From an energyconsumption and greenhouse gas emissionreduction point of view, there is merit inhaving an AD stage first following bycomposting. The benefit of an AD process isthat it produces energy in the form of biogas,whereas IVC will generally use energy in theprocessing stages, in aerating the waste andtreating any leachate arising from the

process. Although AD liquor often needstreating, the energy required is availablefrom the biogas. The digestate from ADoften needs to be matured by compostingbefore it can be applied to land. Since theAD process has reduced the total amount ofmaterial, less energy should be required thanif the whole amount of waste was treatedthrough IVC. Notwithstanding these issues,some proportions of materials are inherentlybetter suited to either composting ofanaerobic digestion. For example, highproportions of green waste with much bulkywood material is better suited to compostingprocesses as it is easier to handle and has lessgas production. Conversely, high proportionsof kitchen waste are better suited to ADprocesses as the gas production potential ishigher and odour control is easier to achieve.

3.1 Introduction

The markets and outlets discussed in thissection relate primarily to those producedfrom the biological treatment of sourcesegregated municipal waste. ABT has thepotential to produce a number of usefuloutputs including compost from aerobiccomposting and digestate, liquor and biogasfrom anaerobic digestion. Outlets for theoutputs from ABT treating mixed, residualMSW are discussed in more detail in the MBTBrief.

3.2 Use of compost on land

ABT processing of source segregated organicmunicipal waste can produce stabilised andsanitised compost or partially stabiliseddigestate material. The potential applicationsof these outputs are dependent upon theirquality and legislative and market conditions.

The quality of compost produced will varywith different ABT technologies, the qualityof raw waste inputs (including seasonalvariations), and the method and intensity ofwaste preparation and separation prior toABT, as well as the methods used to screenthe outputs. Compost is suitable for use in anumber of sectors, including:

• Land restoration and soft landscaping

• Domestic use in gardens

• Agriculture and horticulture

The activities of the Waste & Resources ActionProgramme (WRAP) have resulted in thedevelopment by the British StandardsInstitute of a Publicly Available Specificationfor composted materials (BSI PAS 100). Thepurpose of the specification is to increaseconsumer confidence in buying compost.Compost producers who are PAS 100 certified

produce a ‘quality compost’, by processingsource segregated biodegradable wastewhich does not exceed the limits illustrated inTable 3. For more information see the WRAPwebsite http://www.wrap.org.uk/composting/compost_specifications/index.html

Table 3: BSI PAS 100 criteria*

* BSI PAS 100 is only valid for composts derived from source-segregated waste, by definition

Compost derived from waste will only ceaseto be a waste when it is applied to landunder an exemption from the EnvironmentAgency. This is considered to be a barrier toincreasing compost use. In order to formalisea quality control procedure for using compostproduced from source segregated waste, aQuality Protocol has been developed8.

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3. Markets and outlets for the outputs

8 The Quality Protocol for the production and use of quality compost from source-segregated biowaste, developed by the Business ResourceEfficiency and Waste (BREW) programme, WRAP and the Environment Agency, published March 2007

Parameter BSI PAS 100 limit

Cadmium, ppm 1.5

Chromium, ppm 100

Copper, ppm 200

Mercury, ppm 1

Nickel, ppm 50

Lead, ppm 200

Zinc, ppm 400

Impurities >2mm 0.5%; of which 0.25%maximum can be plastic

Gravel & stones >4mm <8% in grades otherthan coarse mulch; >4mm in

coarse mulch grade <16%

Pathogens E.coli 1000 cfu/g; NoSalmonella in 25g

Microbial respirationrate

16 mg CO2/g organicmatter/day

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The Quality Protocol for Compost developedby WRAP, the Environment Agency and otherkey players in the industry sector, sets out thecriteria for the production of quality compostfrom source segregated biowaste like foodand garden waste. If compost is producedaccording to these criteria the compostproduced is no longer regarded as a wasteand can be spread to land without the needto register with the Environment Agency fora waste exemption. Compost not producedaccording to the protocol is still considered tobe waste, including any output from non-certified composting sites (e.g. sites which arenot PAS 100 certified or sites covered by otheracceptable certification schemes).

Digestate and liquor are both sources ofnutrients, particularly nitrogen, which offergreat potential for energy and emissionssavings compared with artificiallymanufactured fertiliser. WRAP and partnerorganisations are producing a Protocol fordigestate from AD that will function in asimilar way to the Composting Protocol toease the regulatory barriers to using theoutputs from AD. It is expected to befinalised in mid 2008.

Due to its low quality, opportunities to applycompost-like outputs (CLO) and digestateproduced from mixed MSW to land will belimited (see MBT technology brief).

Waste Management Licensing Regulations

Changes to the Waste Management LicensingRegulations came into force on 1st July 20059.Unless the Quality Protocol applies, a wastemanagement licence (WML) exemption,under Paragraph 7A of the regulations, isrequired by land owners/managers before anycompost, digestate or liquor derived fromsource-segregated waste materials can be

applied to agricultural land. A compost-likeoutput, derived from mixed residual waste, isnot allowed to be applied to agriculturalland. These outputs may be applied tobrownfield and restoration land under aWML exemption, under Paragraph 9A,provided that ecological benefit isdemonstrated.

The Government and the National Assemblyfor Wales consulted in May 2006 on therequirement for compost or digestate to bederived from source-segregated materials if itis to be permitted to be spread to agriculturalland, under a Paragraph 7A WML Exemption.In the light of consultation, the Governmenthas concluded that, for now, the source-segregation requirement should remain.However, the Government views this as aninterim measure, and will carry out work tofind a longer term, more sustainable solutionthat will encourage the development of[mixed MSW ABT] technologies that willproduce high standard outputs which couldbe safely spread to land.

For the latest position contact or visit theEnvironment Agency and Defra websites.

Animal By-Products Regulations (ABPR)

ABT plants that process food waste andintend to use the stabilised organic materialon land (including landfill cover) will beconsidered to be a composting or biogasplant, and will fall within the scope of theABPR. These sites must therefore meet alltreatment and hygiene standards required bysource-segregated waste composting/biogasplants (see Section 6).

Mixed MSW will contain household kitchen(‘catering’) waste including meat, and as suchwill, at least, fall under UK national ABPR10

9 The Waste Management Licensing (England and Wales) (Amendment and Related Provisions) (No. 3) Regulations 2005 (S.I. No. 1728)10Animal By-products Regulations 2003 (SI 2003/1482); Wales (SI 2003/2756 W.267); Scotland (SSI 2003/411)


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standards for catering waste containing meat.In some cases it may also contain certaincommercial/industrial waste containing rawmeat or fish; classified as ‘Category 3’ animalby-products. Category 3 animal by-productsmust be treated in accordance with the EUregulation11 standards.

3.3 Biogas from anaerobic digestion

Biogas can be used in a number of ways. Itcan be used as a natural gas substitute(distributed into the natural gas supply) orconverted into fuel for use in vehicles. Morecommonly it is used to fuel boilers to produceheat (hot water and steam), or to fuelgenerators in combined heat and power(CHP) applications to generate electricity, aswell as heat.

Biogas electricity production per tonne ofwaste can range from 75 to 225 kWh, varyingaccording to the feedstock composition,biogas production rates and electricalgeneration equipment. Generating electricityfrom biogas is considered ‘renewable energy’and benefits from support under theRenewables Obligation, see Section 9.3.

In most simple energy productionapplications, only a little biogas pre-treatment is required. Biogas used in a boilerrequires minimal treatment and compression,as boilers are much less sensitive to hydrogensulphide and moisture levels, and can operateat a much lower input gas pressure.

Where biogas is used for onsite electricitygeneration, a generator similar to that usedin landfill gas applications can be used, asthese generators are designed to combustmoist gas containing some hydrogensulphide. Gas compression equipment may berequired to boost the gas pressure to thelevel required by the generator.

Some electricity is used by the AD plant, butexcess electricity produced (typically ~75%)can be sold and exported via the localelectricity distribution network. Excess heatcan also be used locally in a district heatingscheme, if there is an available user.

For high specification applications (e.g.vehicle fuel, natural gas substitute), or whenusing more sophisticated electricitygeneration equipment (e.g. turbines), biogaswill require more pre-treatment to upgradeits quality. This includes the removal ofhydrogen sulphide (a corrosive gas); moistureremoval; pressurization to boost gas pressure;and removing carbon dioxide to increase thecalorific value of the biogas. However, thecost of the equipment required to upgradebiogas can be prohibitive.

3.4 Refuse Derived Fuel (RDF)

RDF is not usually an output from ABTaccepting source segregated waste only. Forinformation on RDF outlets please refer tothe MBT Technology Brief.

11 Regulation EC 1774/2002 laying down health rules concerning animal by-products not intended for human consumption

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4. Track record

ABT technologies such as in-vesselcomposting (IVC) and anaerobic digestionhave been proven for source segregatedmaterials overseas and increasingly in the UK,but operations processing organics from MBTare much fewer. The examples illustratedhere are for UK facilities, including two fromthe Defra New Technologies DemonstratorProgramme. For examples of facilities usingABT within MBT processing mixed residualMSW, please see the separate MBT Briefwithin this series.

4.1 Aerobic (composting) technology

This form of technology has beencommercially developed in the UK for source-segregated materials. Most UK experience todate is still dominated by open-airmechanically turned pile (windrow)composting accepting green garden waste,although in-vessel facilities have increaseddue to the Animal By-Product Regulations.In-vessel systems allow animal by-products,such as meat and dairy products, to becomposted.

Case studies

Bioganix rotating drum in-vessel compostfacility, Parham near Ipswich

This £2.4 million rotating drum compostingsystem is designed to take 15,000 tonnes peryear, including source-segregated garden andkitchen waste from Suffolk Coastal DistrictCouncil. The waste is shredded before it isplaced inside the rotating drum. It is a batchprocess, so once a drum has been filled theprocess begins. The material is composted inone drum for 4 days. The material is thenremoved from the drum, screened to a 12mmparticle size and placed into a second drumsupplemented with steam to achievesanitisation under EU animal by-productslegislation. This material is then distributedoff-site for use on farmland.

A new Bioganix facility has recently beenconstructed under the Defra NewTechnologies Demonstrator Programme inLeominster. The facility accepts sourcesegregated organic waste from Shropshireand Herefordshire. A visitor centre will beavailable for local authorities to learn moreabout the Bioganix process.

Terra Eco Systems in-vessel compostingsystem, High Heavens, High Wycombe,Buckinghamshire

High Heavens IVC composting bays. Source: CRSwww.crservices.co.uk

The High Heavens facility was built to a CRSLtd design and is operated by Terra EcoSystems for Buckinghamshire County Council.Partial funding was received from the DefraChallenge fund. The facility has beenoperating under full ABPR approval sinceFebruary 2005 and receives kerbside collectedgarden and kitchen waste, also garden wastefrom civic amenity facilities. Current processcapacity is for 15,000 tonnes per year; aplanned expansion to 40,000 tonnes per yearwill accommodate increased kerbsidecollections.

Input material is shredded, has water addedand is then screened (200 mm) before beingloaded into a first barrier composting bay.The composting process takes place in singledoor bays, each having a capacity of around140 tonnes. Aerobic conditions are sustainedthrough use of an air handling system, withair being drawn into the compost from pipeswithin the floor and then either recirculatedor vented through an odour control system.

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4. Track record

Continuous temperature monitoringidentifies the stage at which the first ABPRbarrier has been passed, following which thematerial is moved to another composting bayand monitored until the second barrier ispassed. The processed material can then bemoved to an open maturation area. Thecomposted material is distributed off site foruse on farmland and in landscaping.

4.2 Anaerobic Digestion (biogas)technology

This technology has been proven on sewagesludge across the UK water industry, withsome success on source segregated municipalwaste.

South Shropshire Biowaste Digester(Greenfinch Ltd & South Shropshire DistrictCouncil)

Greenfinch AD plant Ludlow. Photo: Greenfinch

This facility in Ludlow, Shropshire is a DefraNew Technologies Demonstrator plant. It isdesigned to treat 5,000 tonnes per year ofsource separated garden and kitchen waste.The input waste undergoes twoshredding/wetting stages before beingplaced into a feedstock buffer tank. Thisfeeds the AD tank, which uses a uses wetmesophilic (37ºC) AD process in a fully-mixedtank. The AD process is continuous with abatch pasteurisation process (70ºC for onehour) at the end to meet ABPR requirements.The digested material is then separated intodigestate (>0.5mm) for use as a soil

conditioner, and liquor to be used as abiofertiliser. The biogas produced fuels acombined heat and power (CHP) unit, toproduce renewable electricity for the gridand process heat available for district / localheat needs. When operating at full capacity,the net electricity production is estimated tobe 1.5 million kWh and a net heat output of2.2 million kWh.

Stornaway AD facility, Western Isles Scotland

Stornoway digestor under construction. Source: Earth Tech UK

This facility is a ‘dry’ AD system bytechnology supplier Linde, constructed byEarth Tech. The source segregated organicstream is offloaded to a dedicated receptionbay and then crushed to reduce particle size.Crushed waste is conveyed via an over bandmagnet to remove metal contaminationbefore being screened through a trommel;the screened under size (<60 mm) istransferred to the anaerobic digestion plantand the over size is recycled back to thecrusher. The screened material passes toaerated buffer tanks for 1.5 days to increasefeedstock temperature prior to digestion andis further refined in particle size to complywith ABPR requirements (<50mm). The feedstock is then fed into the digester where it isanaerobically treated over a 26 day period.

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4. Track record

The AD plant inputs are dry solids ofapproximately 32%, output dry solids ofapproximately 25%. The digester complieswith ABPR requirements of 57°C for 5 hours.

Digestate is dewatered in a two stage systemand the digestate cakes are taken off site foropen windrow composting and maturation.Collected biogas is used to generateelectricity and heat in a combined heat andpower engine. All electricity producedqualifies for ROCs and is used to run thefacility, with excess being exported to thegrid.

4.3 MBT technology

Several MBT technologies have been provenin mainland Europe (see MBT WasteManagement Technology Brief, in this series)and so the current issue is one of appropriatetechnology transfer. The UK test-bed forthese technologies is now in progress, with

the construction of 2 plants operated byShanks in East London Waste Authority(ELWA), the Biffa plant in operation inLeicester, the SITA plant in operation at Bykerand the smaller scale Premier plant in CountyDurham.

The least proven aspect of MBT technologiesis probably the final quality andcontamination levels of any stabilised organicresidues produced. There are expected to beonly limited outlets for these compost-likeoutputs (CLOs), even when distributed free ofcharge, with costs involved to dispose of suchmaterials through other routes. Furtherinformation is available in the MBTTechnology Brief and other referencedocuments such as the SITA EnvironmentalTrust report on MBT (see further reading).

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5. Contractual and financing issues

5.1 Financing

Development of ABT plant will involve capitalexpenditure of several million pounds. Thereare a number of potential funding sources forLocal Authorities planning to develop suchfacilities, including:

Capital Grants: general grants may beavailable from national economic initiativesand EU structural funds;

Prudential Borrowing: the LocalGovernment Act 2003 provides for a'prudential' system of capital finance controls;

PFI Credits and Private Sector Financing:under the Private Finance Initiative a wasteauthority can obtain grant funding fromcentral Government to support the capitalexpenditure required to deliver new facilities.This grant has the effect of reducing thefinancing costs for the Private Sector, therebyreducing the charge for the treatment service;

Other Private-Sector Financing: Acontractor may be willing to enter a contractto provide a new facility and operate it. Thecontractor’s charges for this may be expressedas gate fees; and

Existing sources of local authorityfunding: for example National Non-DomesticRate payments (distributed by centralgovernment), credit (borrowing) approvals,local tax raising powers (council tax), incomefrom rents, fees, charges and asset sales(capital receipts). In practice capacity for thiswill be limited but generally it is throughraising taxes.

The Government is encouraging the use ofdifferent funding streams, otherwise knownas a ‘mixed economy’ for the financing andprocurement of new waste infrastructure toreflect the varying needs of local authorities.

Contractual Arrangements

Medium and large scale municipal wastemanagement contracts are usually procuredthrough the Competitive Dialogue procedureunder the Public Contract Regulations (2006).

The available contractual arrangementbetween the private sector provider (PSP) andthe waste disposal authority (or partnership)may be one of the following:

Separate Design; Build; Operate; andFinance: The waste authority contractsseparately for the works and services needed,and provides funding by raising capital foreach of the main contracts. The contract tobuild the facility would be based on thecouncil’s design and specification and thecouncil would own the facility onceconstructed;

Design & Build; Operate; Finance: Acontract is let for the private sector to provideboth the design and construction of a facilityto specified performance requirements. Thewaste authority owns the facility that isconstructed and makes separatearrangements to raise capital. Operationwould be arranged through a separateOperation and Maintenance contract;

Design, Build and Operate; Finance: TheDesign and Build and Operation andMaintenance contracts are combined. Thewaste authority owns the facility onceconstructed and makes separatearrangements to raise capital;

Design, Build, Finance and Operate(DBFO): This contract is a Design and Buildand Operate but the contractor also providesthe financing of the project. The contractordesigns, constructs and operates the plant toagreed performance requirements. Regularperformance payments are made over a fixed

term to recover capital and financing costs,operating and maintenance expenses, plus areasonable return. At the end of the contract,the facility is usually transferred back to theclient in a specified condition; and

DBFO with PFI: This is a Design, Build,Finance and Operate contract, but it isprocured under the Private Finance Initiative.In this case the waste authority obtains grantfunding from Government as a supplement tofinance from its own and private sectorsources. The PFI grant is only eligible forfacilities treating residual waste and ispayable once capital expenditure is incurred.

The majority of large scale wastemanagement contracts currently beingprocured in England are Design, Build,Finance and Operate contracts and manywaste disposal authorities in two tier Englisharrangements (County Councils) are currentlyseeking to partner with their WasteCollection Authorities (usually District orBorough Councils). Sometimes partnershipsare also formed with neighbouring UnitaryAuthorities to maximise the efficiency of thewaste management service and make thecontract more attractive to the Private SectorProvider.

Before initiating any procurement or fundingprocess for a new waste managementtreatment facility, the following issues shouldbe considered: performance requirements;waste inputs; project duration; project cost;available budgets; availability of sites;planning status; interface with existingcontracts; timescales; governance and decisionmaking arrangements; market appetite andrisk allocation.

Further guidance on these issues can beobtained from the following sources:

• Local Authority fundinghttp://www.defra.gov.uk/environment/waste/localauth/funding/pfi/index.htm

• The Local Government PFI project supportguidewww.local.odpm.gov.uk/pfi/grantcond.pdf

• For Works Contracts: the Institution of CivilEngineers ‘New Engineering Contract’(available at www.ice.org.uk)

• For large scale Waste Services Contractsthrough PFI and guidance on waste sectorprojects see the 4ps, local government'sproject delivery organisationhttp://www.4ps.gov.uk/PageContent.aspx?id=90&tp=Y

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5. Contractual and financing issues

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6. Planning and permitting issues

6.1 Planning

This section contains information on theplanning and regulatory issues associatedwith ABT facilities based on legislativerequirements, formal guidance, good practiceand in particular drawing on informationcontained in the Office of the Deputy PrimeMinister’s research report on waste planningpublished in August 200412.

6.2 Planning

All development activities are covered byPlanning laws and regulations. Minordevelopment may be allowed underPermitted Development rights but in almostall cases new development proposals forwaste facilities will require planningpermission.

Under certain circumstances new wastefacilities can be developed on sites previouslyused for General Industrial (B2) or Storageand Distribution (B8) activities. In practiceeven where existing buildings are to be usedto accommodate new waste processes,variations to existing permissions are likely tobe required to reflect changes in trafficmovements, emissions etc.

Under changes to the planning systemintroduced in 2006 all waste development isnow classed as ‘Major Development’. This hasimplications with respect to the level ofinformation that the planning authority willexpect to accompany the application and alsowith respect to the likely planningdetermination period. The targetdetermination periods for differentapplications are:

• Standard Application – 8 weeks

• Major Development - 13 weeks

• EIA Development - 16 weeks

The principal national planning policyobjectives associated with waste managementactivities are set out in Planning PolicyStatement (PPS) 10 ‘Planning for SustainableWaste Management’ published in July 2005.Supplementary guidance is also containedwithin the Companion Guide to PPS 10. Bothof these documents can be accessed via theDepartment of Communities and LocalGovernment (DCLG) website13.

PPS 10 places the emphasis on the plan ledsystem which should facilitate thedevelopment of new waste facilities throughthe identification of sites and policies in therelevant local development plan. Separateguidance on the content and validation ofplanning applications is also available fromDCLG through their website14. IndividualPlanning Authorities can set out their ownrequirements with respect to supportinginformation and design criteria throughSupplementary Planning Documents linked tothe Local Development Framework. It isimportant that prospective developers liaiseclosely with their Local Planning Authoritiesover the content and scope of planningapplications.

The process of gaining planning permissionfor a new ABT facility should not beunderestimated. Although potentially lesscontentious compared with other wasteprocessing operations such as thermaltreatment the majority of all new wasteproposals attract considerable local interest.

12 http://www.communities.gov.uk/embeddedindex.asp?id=114571113http://www.communities.gov.uk/index.asp?id=114383414http://www.communities.gov.uk/pub/494/BestPracticeGuidanceontheValidationofPlanningApplicationsPDF326Kb_id1144494.pdf

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6.3 Key Issues

The primary emissions from these plants areemissions to air and the limited potential fordischarges to water by leachate and landimpacts from the application of soilconditioners.

When considering the planning implicationsof an ABT facility the other issues that willneed to be considered are common to mostwaste management facilities. The key issuesare therefore:

• Plant/Facility Siting;

• Traffic;

• Air Emissions / Health Effects;

• Odour;

• Bio-aerosols (and Dust)

• Flies, Vermin and Birds;

• Noise;

• Litter;

• Water Resources;

• Nutrient Retention; and

• Visual Intrusion.

A brief overview of the planning context foreach of these issues is provided below.

6.4 Plant Siting

ABT technologies are often housed inpurpose designed and configured buildingsbut may also, (particularly in-vesselcomposting) be developed within existingbuildings. AD reactors are invariablyexternally sited tank structures.

PPS 10 and its Companion Guide containgeneral guidance on the selection of sitessuitable for waste facilities. This guidance

does not differentiate between facility typesbut states that:

“Most waste management activities are nowsuitable for industrial locations, many fallwithin the general industrial class in the UseClasses Order.15

The move towards facilities and processesbeing enclosed within purpose designedbuildings, rather than in the open air, hasaccentuated this trend. The guidance goeson to state:

“With advancement in mitigation techniques,some waste facilities may also be consideredas light industrial in nature and thereforecompatible with residential development. Inmore rural areas, redundant agricultural andforestry buildings may also provide suitableopportunities, particularly for themanagement of agricultural wastes”

The following general criteria would alsoapply to the siting of new ABT plants:

• Buildings which might house ABT can besimilar in appearance and characteristics tovarious process industries. It would oftenbe suitable to locate facilities on landpreviously used for general industrialactivities or land allocated in developmentplans for such (B2) uses;

• Facilities are likely to require goodtransport infrastructure. Such sites shouldeither be located close to the primary roadnetwork or alternatively have the potentialto be accessed by rail or barge;

• The location of such plants together withother waste operations such as MBT/MHTand ATTs can be advantageous. Thepotential for co-location of such facilitieson resource recovery parks or similar is also

15 The Town and Country Planning (Use Classes) Order 1987. SI 1987 No. 764

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highlighted in the PPS 10 and theCompanion Guide; and

• The potential for export of energy to hostusers or the national grid should also be akey consideration in the siting of AD typeABT plants.

6.5 Traffic

ABT facilities may be served by significantnumbers of HGVs (depending on the scale ofthe facility) with a potential impact on localroads and the amenity of local residents. It islikely that the site layout/road configurationwill need to be suitable to accept a range oflight and heavy vehicles. For a 50,000tpacapacity plant, up to 20 Refuse CollectionVehicles per day would be anticipated.

6.6 Air Emissions / Health Effects

Potential health effects of compostingfacilities are likely to be strongly dependenton the type of facility (open windrow or in-vessel system). Studies have found noincrease in cancer or asthma in populationsclose to composting facilities. However, evena well-run open windrow facility can give riseto emissions of micro-organisms and dusts,which can lead to public concern abouthealth impacts on people living in closeproximity to the facility. The EnvironmentAgency suggests that risk assessments may beundertaken on sites where there are sensitivereceptors nearby. Emissions and potentialrisks to health can be more readily controlledin an IVC and AD facility than an open site.

One published study has indicated a possiblelink between commercial scale opencomposting and respiratory symptoms inpeople living nearby. This study related to asingle facility and is currently being re-evaluated by the German EnvironmentMinistry.

No studies suggesting adverse health effects

of AD facilities processing municipal wastehave been published. Depending on thenature of an individual facility, potentialhealth effects of AD facilities might beexpected to be comparable to those ofcomposting facilities, and may potentiallyhave fewer emissions of volatile odorouscompounds. AD processes also involve theproduction and combustion of biogas. This isbeneficial for the production of heat and/orelectricity, the combustion of biogas willresult in mainly carbon dioxide and watervapour.

6.7 Odour

The control of odour at ABT facilities needsextremely careful consideration. As most ABTtechnologies are almost entirely enclosed,potential odour emissions can normally becontrolled through the building ventilationsystem. If there is a combustion element tothe facility, odorous air extracted fromprocess areas can be used in the combustionstage. Particular attention may need to bepaid to headspace air in enclosed storagefacilities such as digestate tanks.

If there is no combustion element, theprocess of air extraction and ventilation willnevertheless dilute odorous air. It may benecessary to disperse extracted air from anelevated point, and/or treat the air.Biofiltration systems can be used for controlof odours in air extracted from working areasif required. The need for, and design ofodour control systems would need to beassessed on a site-by-site basis.

Control of odours from open compostingsystems relies on good control andmanagement of the composting process.Some odour is unavoidable, and opencomposting facilities can be problematic fromthe perspective of odour if not properly sitedand operated.

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6.8 Flies, Vermin and Birds

The enclosed nature of ABT operations willlimit the potential to attract vermin andbirds. However, during hot weather it ispossible that flies could accumulate, especiallyif they have been brought in during deliveryof the waste. Effective housekeeping and onsite management of tipping and storageareas is essential to minimise the risk fromvermin and other pests. In some operationswaste heat from the process may be used tobring temperatures in fresh input waste tolevels above which flies can live.

6.9 Noise

Noise is an issue that will be controlled underthe waste licensing regulations and noiselevels received at nearby receptors can belimited by a condition of a planningpermission. The main contributors to noiseassociated with ABT are likely to be:

• vehicle movements / manoeuvring;

• traffic noise on the local road networks;

• mechanical processing such as wastepreparation;

• air extraction fans and ventilation systems;and

• operations associated with turning andaeration of the biomass.

6.10 Litter

Any waste which contains plastics and paperis more likely to lead to litter problems. Litterproblems can be minimised as long as goodworking practices are adhered to and vehiclesuse covers and reception and processing areundertaken indoors.

6.11 Water Resources

The release of potentially harmful chemicalsinto surface and/or ground water is only likelywhere there is uncontrolled leachate and/orrun off from the working areas contaminatedwith waste materials. Most ABT will have tightcontrol of such emissions through extensiveimpermeable surfaces, drainage, and hygieneprocedures as required under ABPR.

6.12 Nutrient Retention

Biological processes (both aerobic andanaerobic) offer the opportunity for keynutrients including Nitrogen, Phosphorus andPotassium and other trace metals to beretained in the agricultural/horticultural cycle.This is in contrast to the thermal processes,where bulk of the nutrients are either lost toa different medium or removed completelyfrom the natural cycles.

6.13 Design Principles and VisualIntrusion

Planning guidance in PPS 10 emphasises theimportance of good design in new wastefacilities. Good design principles andarchitect input to the design and physicalappearance of waste facilitates is essential.Buildings should be of an intrinsically highstandard and should not need to be screenedin most cases.

Good design principles also extend to otheraspects of the facility including having regardto issues such as:

• Site access and layout;

• Energy efficiency;

• Water efficiency; and

• The general sustainability profile of thefacility.

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Construction of any building will have aneffect on the visual landscape of an area.Visual intrusion issues should be dealt with ona site specific basis and the following itemsshould be considered:

• Direct effect on landscape by removal ofitems such as trees or undertaking majorearthworks;

• Site setting; is the site close to listedbuildings, conservation areas or sensitiveviewpoints;

• Existing large buildings and structures inthe area;

• The potential of a stack associated withsome air clean up systems for mixed wasteprocessing operations may impact on visualintrusion;

• Use of screening features (trees, hedges,banks etc);

• The number of vehicles accessing the siteand their frequency, and;

• Many of these facilities are housed in‘warehouse’ type clad steel buildings,however use of good design techniquescan help minimise visual intrusion.

6.14 Size and Landtake

ABT plants can be built for a wide range ofcapacities. The chosen scale will reflect thetonnage necessary to meet local wastestrategy targets and make the facilityprofitable within the conditions of thecontract, within the limitations of localplanning and permitting restrictions. MostABT facilities for source segregated waste willhave capacities in the range of 10,000 and60,000 tpa.

The capacity of ABT facilities within MBTfacilities is usually over 50,000 tpa but under200,000 tpa.

The scale of the biological process dependson the total material throughput, and theresidence time of the material in thebiological process. In general AD processesrequire shorter residence times and so aresmaller in scale than IVC facilities. However,often AD facilities will need to be followed byan aerobic (composting) process to completestabilisation, and dry the digestate.

Different residence times will relate toregulatory requirements (e.g. ABPR), theefficiency of the process, and parametersrequired for the final output (e.g. moisturecontent, stability/respiration rates), andoutput end use.

Landtake is highly variable, a general rule ofthumb is between 0.5 and 1m2 per tonne ofinput material will be required. Tallerbuildings are required for vertical compostingunits compared to tunnel units.

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6.15 Environmental Impact Assessment(EIA)

Some small ABT facilities may not require EIA.However, those which are located withinsensitive areas or close to sensitive receptorswill require EIA under Schedule II – Part 11‘Other Projects’ (b) installations for thedisposal of waste – of the EIA Regulations.

6.16 Licensing/permitting

If processing over 50 tonnes a day, a PollutionPrevention & Control (PPC) permit would berequired to operate an IVC and AD facility.Most facilities are smaller in size and willrequire a Waste Management Licence to

operate. The Environmental PermittingProgramme (EPP) is due to be implemented inApril 2008 which will combine waste licensingand permitting systems.

For more information on licensing &permitting see the Environment Agency site.

For more information on licensing &permitting see http://www.environment-agency.gov.uk/subjects/waste/?lang=_e

Box 1 illustrates some of the key planningfeatures of the Wanlip AD facility operatedby Biffa Ltd in the planning authority ofLeicestershire County Council.

Box 1: Wanlip AD facility

• The 40,000 tpa facility is located on 0.7haof Severn Trent Water’s sewage treatmentworks

• It is designed to receive the fine organicfraction from the ball mill facility (amechanical treatment facility receivingresidual MSW)

• Application submitted in December 2002and approved in March 2003 with 14conditions

• An EIA was not required; site issurrounding by existing industrial land tothe north and west with the A46immediately to the south and east

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6.17 Animal By-products Regulations(ABPR)

Any ABT type facility producing a stabilisedorganic output to land will be required tomeet EU ABPR standards for processingCategory 3 animal by-products or, at least,national ABPR standards for ‘catering’ wastecontaining meat (see table below). The EUABPR standard requires that all material beeither anaerobically digested or composted at70°C for at least 1 hour with a maximumfeedstock particle size of 12 mm.

Table 4: National ABPR minimum standards

* Two processing stages can be achieved in one reactorwhere an internal mixing process is used.

Premises must be enclosed from wastereception until at least the completion of thefirst processing stage. The processing sitemust also prevent access to animals and birds,which could act as potential pathogenvectors. Partially or fully treated materialmust not be contaminated with any materialthat has been treated to a lesser extent.There must be no way that any untreated orpartially treated materials can by-pass thepasteurisation and storage stages within thesystem.

To ensure all these process and hygienestandards are met, strict operating,monitoring, and hygiene procedures must befollowed according to a Hazard Analysis andCritical Control Point (HACCP) plan. TheHACCP plans must be developed and verified(through site checks and microbial analysis ofsamples) as part of the ABPR approvalprocess.

AD(one process stagebelow, plus storage)

Composting*(any 2 process stages listed below)

70°C; 1 hour; maxparticle size 60mm

Enclosed reactor 70°C for atleast 1 hour with a maximumparticle size of 60mm

57°C; 5 hours; maxparticle size 50mm

Enclosed reactor at 60°C for atleast 2 days with a maximumparticle size of 400mm

At least 18 daysstorage (may be inthe open)

Housed (if first stage) or openair (if second stage) turned piles

60°C; 2 days achieved 4 timesconsecutively, with a turningbetween each; max particle sizeof 400mm

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7. Social and perception issues

This section contains a discussion of the socialand environmental considerations of ABTfacilities.

7.1 Social Considerations

Any new facility is likely to impact on localresidents and may result in both positive andnegative impacts. Potential impacts on localamenity (odour, noise, dust, landscape) areimportant considerations when siting anywaste management facility. These issues areexamined in more detail in the Planning &Permitting chapter of this Brief. Transportimpacts associated with the delivery of wasteand onward transport of process outputs maylead to impacts on the local road network.The Planning and Permitting chapter of thisBrief provides an estimate of potential vehiclemovements.

Potential environmental and local amenityimpacts, whether real or perceived, can cause agreat deal of concern. ABT plants can be largefacilities that should be sited carefully, tominimise these impacts (see section 6). ABTfacilities may also provide positive socialimpacts in the form of employment andeducational opportunities, as well as a low-costsource of heat (in the case of biogas plants).Table 4 provides an estimate of the jobscreated by a new plant. These facilities are alsolikely to provide vocational training for staff.Many new facilities are built with a visitorscentre to enable local groups to view thefacility and learn more about how it operates.

7.2 Public Perception

Changes in waste management arrangementsin local areas is creating a higher profile forthe service through the media. Many peopleas a result of greater publicity and targetededucation are now embracing the need forwaste reduction, recycling and to a lesserextent the need for new waste facilities. Thewider perception of waste facilities as a badneighbour will take longer to overcome.

New waste facilities of whatever type arerarely welcomed by residents close to wherethe facility is to be located.

Public opinion on waste management issues iswide ranging, and can often be at extremeends of the scale. Typically, the mostpositively viewed waste management optionsfor MSW are recycling and composting.However, this is not necessarily reflected inlocal attitudes towards the infrastructurecommonly required to process waste tocompost, or sort mixed recyclables, or indeedto have an extra wheeled bin or box. Itshould be recognised that there is alwayslikely to be some resistance to any wastemanagement facility within a locality, despitethe necessity to have the capacity to dealwith societies waste.

Overall, experience in developing wastemanagement strategies has highlighted theimportance of proactive communication withthe public over waste management options.The use of realistic and appropriate models,virtual ‘walk – throughs’ / artists impressionsshould be used to accurately inform thepublic. Good practice in terms of publicconsultation and engagement is an importantaspect in gaining acceptance for planningand developing waste managementinfrastructure. Defra are funding thedevelopment of small to medium scaledemonstration plant in England for localauthorities to visit and for Defra to publishdata on performance.

At present there is a relatively low level ofpublic understanding on the concept of ABT.However it would be anticipated thatbiological processing of waste, in line withthe concept of composting, may receive amore positive reaction than other alternativewaste management options.

Defra is funding the development of small tomedium scale demonstration plant in Englandfor local authorities to visit and for Defra topublish data on performance. For moreinformation contact [email protected].

In this section, the cost of ABT facilities withanaerobic and aerobic processes is discussed.

The costs below in Table 5 illustrate theestimated gate fee for different biologicaltreatment technologies recently published byWRAP16. The gate fee for in-vesselcomposting is suggested for a typical capacityof between 10-20,000 tpa. A recentlypublished study by Defra however suggeststhat the practical, optimum capacity for IVC is50,000 tpa, using a transport and process costmodel17. ABT facilities require considerablymore capital expenditure compared withwindrow composting. Costs are associatedwith buildings, concrete slabs, monitoringequipment and other costs associated withensuring facilities are ABPR compliant.

Table 5: Typical gate fees for biological treatment processes

The variation in magnitude and ranges ofcosts are due to the wide variety of systemsavailable on the market, plant capacities, andthe level of mechanical automation used.Capital expenditure for IVC is estimated to bebetween £30 and £60 per tonne per annum.

The cost of an AD system will depend on thesize of the facility and will vary betweentechnology providers. As an indication ofpossible costs, a large 1 MWe capacity facilitywill cost:

• £3 to 4 Million capital expenditure

• Up to £100,000 per annum running costs

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8. Cost

Biological Process Gate Fee (£/t)

Windrow composting £19

In-vessel Composting £35-40

Anaerobic Digestion £55-65

16Managing biowastes from households in the UK: Applying life-cycle thinking in the framework of cost-benefit analysis. Eunomia Researchand Consulting for Waste & Resources Action Programme, May 2007

17Economies of Scale - Waste Management Optimisation Study by AEA Technology for Defra, April 2007

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9. Contribution to national targets

9.1 Best Value Performance Indicators(BVPI)

BVPI 82b: Composting and AnaerobicDigestion

Compost generated through the processingof source segregated organic material by in-vessel composting will contribute to BVPI 82b,the indicator for the amount of composting alocal authority has achieved. The definition ofBVPI 82b now also includes waste which hasbeen treated through a process of anaerobicdigestion.

Where MBT processes are configured toproduce an organic rich stream known as acompost-like output (CLO) from mixedresidual MSW to be utilised as a low gradesoil conditioner for example, this materialmay (but is ‘unlikely to’ see below) qualify ascomposting under BVPI 82b. The CLO couldbe utilised in applications such as brownfieldrestoration, landfill restoration or some bulkfill uses (provided that the appropriateengineering and quality standards are met).

These materials will only qualify as‘composted’ under the Best ValuePerformance Indicator (BVPI 82b) if theoutput meets the appropriate criteria for usein the intended application. Some wastemanagement contractors have demonstratedthat there is a market for these materials,however the current Best Value PerformanceIndicator Guidance (as of November 2004)states the criteria for composting should be ‘aproduct that has been sanitised andstabilised, is high in humic substances, andcan be used as a soil improver, as aningredient in growing media or blended toproduce a top soil that will meet BritishStandard BS2882 incorporating amendmentno.1…’ It also states that it is ‘unlikely thatproducts of a Mechanical Biological

Treatment process will meet this definition.’However if the definition could be achievedthen the product would qualify as BVPI 82b.

The Government has recently increasednational recycling and composting targets forhousehold waste through the Waste Strategyfor England 2007. Targets are at least 40% by2010, 45% by 2015 and 50% by 2020. Formore information on the contribution of ABTto Best Value Performance Indicators andrecycling see the local authority performancepages on the Defra website

http://www.defra.gov.uk/environment/waste/localauth/perform-manage/index.htm andhttp://www.wastedataflow.org/Documents/BVPI%20FAQs.pdf

9.2 Landfill Allowance Trading Scheme(LATS)

The European Landfill Directive and the UK’senabling act, the Waste & Emissions TradingAct 2003, require the diversion ofbiodegradable municipal waste (BMW) fromlandfill. LATS (known as the LandfillAllowances Scheme, LAS, in Wales) began in2005, and places increasing restrictions on theamount of biodegradable municipal waste(BMW) going to landfill, in line with the EULandfill Directive targets. Local authorityallowances for the amount of BMW they cansend to landfill have been set in relation totheir total MSW arisings in 2001/2.

The ability for ABT processes to divert BMWdepends on the input material, the type &quality of outputs produced and the marketsor outlets found for the outputs. Thetreatment of source segregatedbiodegradable waste will produce compost ordigestate and liquor, all of which canpotentially find a market and result in the fulldiversion of BMW from landfill.

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The biological processing stage of an MBTfacility will be able to contribute to thesetargets in two ways: 1) by turning BMW intoa compost-like output for use on land; or 2)by reducing the mass and biodegradability ofBMW prior to landfill.

A compost-like output has more limitedapplications to land than compost producedfrom source segregated waste because of itslower quality. If a WML exemption can beobtained for the application of the CLO toland then BMW is diverted from landfill.

However, MBT plant can also be used to bio-stabilise waste prior to landfilling. In this casebiological treatment is used to reduce thewaste’s potential to degrade and producemethane once landfilled. The EnvironmentAgency (EA) has developed a methodology todetermine the ‘stability’ or ‘biodegradability’of any outputs from an MBT plant which aresent to landfill. This methodology can beused to determine the actual amount ofbiodegradable material being landfilled. Thisinformation could help an authority achieveallowance allocations under the LandfillAllowance Trading Scheme (LATS). Thetesting is not a statutory requirementcurrently. Detailed guidance on how thediversion of biodegradable waste is measuredin MBT processes can be found on theEnvironment Agency website:

http://www.environment-agency.gov.uk/commondata/acrobat/mbt_1154981.pdf

Up to date information can be obtained fromDefra’s LATS information webpage:

http://www.defra.gov.uk/environment/waste/localauth/lats/index.htm

9.3 Renewable Obligation Certificates(ROCs)

The Renewables Obligation (RO) wasintroduced in 2002 to promote thedevelopment of electricity generated fromrenewable sources of energy. The Obligationrequires licensed electricity suppliers to sourcea specific and annually increasing percentageof the electricity they supply from renewablesources, demonstrated by RenewablesObligation Certificates (ROCs). The targetcurrently rises to 15.4% by 2015/16. Inessence, the RO provides a significant boostto the market price of renewable electricitygenerated in eligible technologies.

Electricity generated from the biomass(renewable) fraction of waste by anaerobicdigestion is eligible for support under the RO.In the case of ABT, this applies to theelectricity generated from the biogas. Thiscan provide an important additional revenuestream for a proposed plant, as long as itmeets the qualifying requirements. As thevalue of a ROC is not fixed, the long termvalue would need to be assessed in detail todetermine its overall financial value to theproject.

The Department for Industry (DTI) isconsidering providing greater support totechnologies producing renewable energyand assessing methods for removing barriersto renewable energy generation.

Up-to-date information regarding RDF andROCs can be obtained from the DTI website

www.dti.gov.uk/energy/sources/renewables/index.html.

9. Contribution to national targets

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10. Further reading and sources ofinformation

WRATE (Waste and Resources Assessment Tool for the Environment) http://www.environment-agency.gov.uk/wtd/1396237/?version=1&lang=_e

The Waste Technology Data Centre www.environment-agency.gov.uk/wtd

New Technologies Demonstrator Programme [email protected]

Integrated Pollution Prevention and Control, Draft Reference Document on Best AvailableTechniques for the Waste Treatments Industries, European Commission – Directorate GeneralJoint Research Centre, January 2004

WRAP Organics website http://www.wrap.org.uk/materials/organics/

The Composting Association, including reports on Anaerobic Digestion and Directory of In-Vessel Composting http://www.compost.org.uk/dsp_home.cfm

Chartered Institution of Wastes Management. http://www.ciwm.co.uk

Mechanical Biological Treatment: A Guide for Decision Makers, Processes, Policies and Markets(2005), by Juniper consultancy Ltd for Sita Environmental Trusthttp://www.sitaenvtrust.org.uk/research/overview

Defra (2004) Review of Environmental and Health Effects of Waste Management: MunicipalSolid Waste and Similar Wastes.

European Commission – Directorate General Joint Research Centre (January 2004) IntegratedPollution Prevention and Control, Draft Reference Document on Best Available Techniques forthe Waste Treatments Industries.

Greenpeace Environmental Trust (2003) Cool Waste Management: A State-of-the-ArtAlternative to Incineration for Residual Municipal Waste: MBT

Friends of the Earth, Residuals Report

Defra (2001) Guidance on Municipal Waste Management Strategies; and Best ValuePerformance Indicators for Frequently Asked Questions for 2004/05 at:http://www.defra.gov.uk/environment/waste/localauth/bvpi_faq.pdf

Office of the Deputy Prime Minister’s guidance:http://www.odpm.gov.uk/stellent/groups/odpm_localgov/documents/page/odpm_locgov_609123-10.hcsp

GLA / S. McLanaghan (2003) City Solutions: New and Emerging Technologies for SustainableWaste Management ISBN: 1-85261-491-2

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10. Further reading and sources ofinformation

GLA (2003) Supporting documentation for City Solutions Conference:http://www.london.gov.uk/mayor/strategies/waste/wasteconfce.jsp#docs

Associates in Industrial Ecology (AiIE) (2002) Delivering the Landfill Directive: The Role of Newand Emerging Technologies. Report for the Strategy Unit 0008/2002

Associates in Industrial Ecology (AiIE) (2003) Review of residual waste treatment technologiesReport prepared on behalf of Kingston upon Hull City Council and East Riding of YorkshireCouncil http://www.hullcc.gov.uk/wastemanagement/download/aiie_report.pdf

Cal Recovery Europe Ltd, Edited by Papadimitriou, E. K. and Stentiford, E. I. (2004) Proceedingsof the 1st UK Conference and Exhibition on: Biodegradable and Residual Waste ManagementISBN: 0-9544708-1-8

CIWM (2002) Biological Techniques in Solid Waste Management and Land Remediation. IWMBusiness Services Ltd.

DEFRA (2004) Introductory Guide: Options for the Diversion of Biodegradable Municipal WasteFrom Landfill: http://www.defra.gov.uk/environment/waste/wip/newtech/index.htm

Enviros & Deloitte (2004) Report for the Mayor of London. Capital Solutions: Guidance forfunding and procuring new and emerging waste recovery technology. ISBN 1 85261 644 X.

Strategy Unit (2002) Waste Not, Want Not. The Stationary Office.

European Environment Agency (EAA) (2002) Biodegradable Municipal Waste Management inEurope. EEA Part 3 Technology & Market Issues. Available from the European EnvironmentAgency website at: http://reports.eea.eu.int/topic_report_2001_15/en.

Eunomia Research & Consulting (2003) Economic Analysis of Options for ManagingBiodegradable Municipal Waste. Available from the European Commission website: LocalAuthority funding http://www.defra.gov.uk/environment/waste/localauth/funding/pfi/index.htm

The Local Government PFI project support guide www.local.odpm.gov.uk/pfi/grantcond.pdf

For Works Contracts: the Institution of Civil Engineers ‘New Engineering Contract’ (available atwww.ice.org.uk).

For large scale Waste Services Contracts through PFI and guidance on waste sector projects seethe 4ps, local government's project delivery organisationhttp://www.4ps.gov.uk/PageContent.aspx?id=90&tp=Y

Planning for Waste Management Facilities – A Research Study. ODPM, 2004.http://www.odpm.gov.uk/stellent/groups/odpm_planning/documents/page/odpm_plan_030747.pdf

http://europa.eu.int/comm/environment/waste/compost/econanalysis_finalreport.pdf.

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11. Glossary11. Glossary

Aerobic In the presence of oxygen.

Anaerobic In the absence of oxygen.

Anaerobic Digestion A process where biodegradable material is encouraged to break down in theabsence of oxygen. Material is placed in to an enclosed vessel and in controlledconditions the waste breaks down typically into a digestate, liquor and biogas.

Animal By-ProductsRegulation

Legislation governing the processing of wastes containing, or having come incontact with, materials derived from animal sources.

Auger Helical shaft, or shaft fitted with a screw-thread, designed to bore into and/ormove material along its length.

Baffle Rigid plate used to direct the flow of material.

Biodegradable The component of Municipal Solid Waste capable of being degraded by plants andanimals. Biodegradable Municipal Waste includes paper and card, food and gardenwaste, wood and a proportion of other wastes, such as textiles.

Biogas Gas resulting from the fermentation of waste in the absence of air(methane/carbon dioxide).

Biodegradable MunicipalWaste (BMW)

The component of Municipal Solid Waste capable of being degraded by plants andanimals. Biodegradable Municipal Waste includes paper and card, food and gardenwaste, and a proportion of other wastes, such as textiles.

Composting Biological decomposition of organic materials by micro-organisms under controlled,aerobic, conditions to a relatively stable humus-like material called compost.

Digestate Solid and / or liquid product resulting from Anaerobic Digestion.

EPA 1990 Environmental Protection Act.

Feedstock Raw material required for a process.

Greenhouse Gas A term given to those gas compounds in the atmosphere that reflect heat backtoward earth rather than letting it escape freely into space. Several gases areinvolved, including carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O),ozone, water vapour and some of the chlorofluorocarbons.

Green Waste Vegetation and plant matter from household gardens, local authority parks andgardens and commercial landscaped gardens.

In-vessel Composting The aerobic decomposition of shredded and mixed organic waste within andenclosed container, where the control systems for material degradation are fullyautomated. Moisture, temperature, and odour can be regulated, and stablecompost can be produced much more quickly than outdoor windrow composting.

Main Heading

Mechanical BiologicalTreatment (MBT)

A generic term for mechanical sorting / separation technologies used in conjunctionwith biological treatment processes, such as composting.

Municipal Solid Waste(MSW)

Household waste and any other wastes collected by the Waste Collection Authority,or its agents, such as municipal parks and gardens waste, beach cleansing waste,commercial or industrial waste, and waste resulting from the clearance of fly-tipped materials.

Recyclate/RecyclableMaterials

Post-use materials that can be recycled for the original purpose, or for differentpurposes.

Recycling Involves the processing of wastes, into either the same product or a different one.Many non-hazardous wastes such as paper, glass, cardboard, plastics and scrapmetals can be recycled. Hazardous wastes such as solvents can also be recycled byspecialist companies.

Refuse Derived Fuel (RDF) A fuel produced from combustible waste that can be stored and transported, orused directly on site to produce heat and/or power.

Renewables Obligation Introduced in 2002 by the Department of Trade and Industry, this system creates amarket in tradable renewable energy certificates, for which each supplier ofelectricity must demonstrate compliance with increasing Government targets forrenewable energy generation.

Source-segregated/ Source-separated

Usually applies to household waste collection systems where recyclable and/ororganic fractions of the waste stream are separated by the householder and areoften collected separately.

Statutory Best ValuePerformance Indicators(BVPI)

Local Authorities submit performance data to Government in the form of annualperformance indicators (PIs). The Recycling and Composting PIs have statutorytargets attached to them which Authorities are required to meet.

Tine Point, or spike protruding from a central shaft to agitate and break-up materialduring turning.

11. Glossary