3.0 TASK 2: CASE STUDIESOF IMPLEMENTED TECHNOLOGIES 3.1 MCA Scenario2: MRF … Waste... · 2017. 8. 24. · 3.2 MCA Scenario 3MBT C: omprising MRF Producing Recyclables and Organics

Oxford County SLR Project No.: 209.40447.00000 WRRT Assessment: Final Study Report August 2017

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3.0 TASK 2: CASE STUDIES OF IMPLEMENTED TECHNOLOGIES

3.1 MCA Scenario 2: MRF Producing Recyclables and RDF for Thermal Treatment Outside OC

3.1.1 Case Study: FCC Environment, Wrexham, UK

The Wrexham MRF plant has been operating since 2012, treating a single waste stream of 30ktpa MSW, operating 1 x 7h shift, three days/week and 20ktpa IC&I wastes, operating 1 x 7h shift, two days/week, i.e. a total of 50ktpa. The plant design throughput is 28.6tph, based on waste with a 350kg/m3 bulk density and maximum lump size <1,000mm.

The plant also includes bio-drying tunnels to produce two grades of stabilised, high grade solid recovered fuel (SRF), able to be stored for up to a year.

3.1.1.1 Process Description

The MRF process initially sorts according to size and physical properties, and subsequently uses numerous mechanical stages to further refine the waste streams. The mechanical process stages are described in detail as follows:

• Input MSW waste material is first sized down to 300mm by a slow speed sizer, to

provide a homogeneous waste stream.

• A high speed rotating trommel separates the material into three streams: 0 to 80mm, 80 to 300mm & plus 300mm. The plus 300mm is conveyed back to the reception hall for processing in the slow speed sizer.

80 to 300mm stream • 80 to 300mm material first conveyed to a permanent overband magnet to remove the

ferrous metals in the waste stream. The ferrous is collected on a conveyor which passes through a single bay manual picking station to ensure clean marketable ferrous is recovered and then conveyed to the ferrous storage bay.

• 80 to 300mm material is then conveyed to an eddy current separator to remove the non-ferrous metals in the waste stream. The non-ferrous metals fraction is collected on a conveyor that passes through a single position sorting station, to ensure clean marketable non-ferrous is recovered that is then conveyed to the non-ferrous metals storage bay.

• 80-300mm oversize fraction from the trommel screen is conveyed to a ballistic separator. Flat/flexible material climbs up the ballistic separator, while the round hard material rolls down to the base of the separator. Intermediate 45mm fines fraction passes through the unit and is combined into the sub 80mm fines fraction.

• Both outputs from the ballistic separator are conveyed to NIR optical sorters (or sets thereof) to positively eject separate streams of plastics, paper/cardboard, wood and textiles. These are conveyed onwards for manual quality picking stations before being baled for export as appropriate.


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• The remaining fractions from the NIR optical sorters are conveyed to a quality control positions to recover further commodities with any value before the residue is conveyed to the SRF Grade 1 storage area ready for bio-drying biological treatment.

0 to 80 mm stream • The 0-80mm material follows a similar process train as the 80-300mm stream,

comprising permanent over-band magnet and eddy current separator.

The remaining sub 80mm fraction is conveyed to the SRF Grade 2 storage area ready for biological treatment (i.e. bio-drying) to stabilise the waste and remove sufficient moisture to raise the Net Calorific Value (NCV) of the fuel for it to be considered as SRF.

Bio-dried fraction • A high speed rotating trommel separates the material into two streams, 0-30mm and 30-

80mm.

• 30 to 80mm material is conveyed to an air belt separator to remove the very heavy fraction as protection for the granulation stage.

• Light fraction from the air belt separator is conveyed to a granulator to produce SRF Grade 1 specification.

• The 0 to 30mm material is conveyed to a hard particle separator to remove the hard aggregate fraction from the SRF Grade 2 material.

The MRF yields the following outputs: • Segregated dry recyclables: mixed paper & card, ferrous metals, non-ferrous metals,

plastics films, mixed plastics, wood, textiles;

• SRF Grade 1 and SRF Grade 2; and

• Reject to landfill (incl. aggregate + heavy residues).

3.1.1.2 Operational Comment

SLR has been unable to gather any operational feedback from FCC, however it has been possible to make the following comments:

• The Wrexham plant is an example of a high complexity plant and particularly so relative

to its modest size of 50ktpa. In its many process stages, the plant includes multiple high cost optical sorters. Contractors are often cautious in selecting these units as they cannot be assured of their separation efficiency prior to install, and there may be a high cost penalty if they do not function.

• There are many manual picking stations which suggest that the plant should yield high quality recyclate outputs. However the labour requirement for the site will also be high.


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3.1.2 Case Study: Neath Port Talbot Recycling Ltd, Swansea, UK

The Materials Recovery and Energy Centre (MREC) was originally commissioned in 2003 to treat 140 ktpa MSW. The site originally comprised materials processing and recovery at the front-end with output of RDF to an on-site incinerator, and downstream composting of the organics fraction.

The MRF configuration has now been altered to exclude composting, but prioritise the quality of the SRF export for offsite WtE. Curbside recyclables collections have also now been introduced so the facility primarily receives residual waste.

SLR has been, and is currently acting as Technical Adviser to the facility owners and their legal teams. Key tasks have included expert witness statements with regards to technical processes and their integration and liaison regarding the potential actions to remediate, improve and optimise operations at the site.


The contemporary facility comprises the following process stages:

• Input residual waste undergoes a manual visual inspection and pre-sort to remove bulky and non-conforming material e.g. gas bottles – to avoid subsequent issues in the primary shredder.

• The material is then processed through a primary shredder and overband magnet.

• The waste is then subject to manual QA inspection in a picking station, for positive removal of metals (refer to Figure 3-1).

• Further metal contaminants are removed through supplementary primary and secondary ferro-magnetic and eddy current separation. These units follow secondary and tertiary shredder units.

• The waste is then directed to a pelletiser unit to produce RDF, or sent onwards for bio-drying and stabilisation in the IVC reactors (refer to Figure 3—2).

• The output from the IVC reactors is then shredded for a final time to sub-30mm in line with fuel specification requirements, before export as SRF.


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Figure 3—1:

Picking Station at Neath Port Talbot

The MRF now yields the following outputs:

• Residual dry recyclables: ferrous metals, non-ferrous metals – other dry recyclables e.g. glass, paper, plastics are largely collected at source via curbside collections;

• SRF; and

• Oversize rejects to landfill.


The MREC is a high tonnage facility that has now evolved to process residual waste to produce a refined SRF, without expensive advanced separation unit operations:

• Due to the high moisture content (35-40% MC) in the MSW, there were regular issues including blocking of the bag-splitter, and high organics carry over (poor separation) in the trommel.

• There were legislative changes following commissioning regarding the disposal of wastes containing Animal By-Products. This implied that the compost output could no longer be diverted to landfill, which was the principal driver for the IVC install.

• The design of the incinerator was erroneously based upon a raw MSW stream, and therefore the interim RDF (prior to the intended on-site incineration) had a higher net calorific value (CV) and higher moisture content than originally anticipated. The


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resulting operational issues were compounded by the absence of on-line cleaning in the design of the incinerator. These design failures led to the incinerator throughput being curtailed to about 25% of design output. This unit has since been decommissioned with a shift in focus to SRF export from site.

• Owing to these legislative changes and incinerator deficiency/decommissioning, various modifications were made to the plant to promote a high quality SRF as the central product, to supply as an alternative fuel to the cement industry. These included: reducing trommel underflow, enhancing metal removal/recovery in the MRF, improved size reduction equipment (shredders) and employing the IVCs to bio-dry the waste stream and therefore reduce the moisture content of the SRF and improve the net CV.

The main issues in the original design were derived from a lack of technical oversight upon conception and EPCC delivery – there was no site Owner’s Engineer and the Local Authority client did not possess the necessary technical expertise.

SLR also notes that if good separation/recyclate recovery is to be achieved in the MRF, a dry waste stream is preferable; for this to occur the inlet waste stream would usually have to exclude any organics. If a ‘wet’ inlet waste stream (e.g. MSW including organics), is required to be treated, then initial drying of the waste stream is a worthwhile design consideration.

Figure 3—2: Bio-drying IVC Tunnels at Neath Port Talbot


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3.2 MCA Scenario 3: MBT Comprising MRF Producing Recyclables and Organics plus Wet AD Organic Processing Stage in OC

3.2.1 Case Study: Biffa, W Sussex, UK

Working in partnership with West Sussex County Council via a 25 year PFI, waste management company Biffa has provided an MBT facility at the Brookhurst Wood site, Horsham, West Sussex to help the Council reduce the amount of non-recycled ‘black bag’ household waste sent to landfill.

The facility was delivered under an EPC contract with Austrian design & build contractor M&W and is designed to divert over 75% of the incoming waste materials into useful resources; it commenced operation in 2015.

The facility has the capacity to process a single waste stream of 310ktpa mixed, residual MSW, with mechanical recovery of metals for recycling, use of the residual paper/plastic for production of RDF and the biodegradable material treated in the AD plant. The biogas from the AD plant generates up to 4.5MWe electricity to both power the MBT and AD facilities and also the balance of power output is exported to the national power grid.


The start of the MBT process uses a mechanical pre-treatment stage to split the waste into four parts:

• biodegradable waste (e.g. food waste);

• refuse derived fuel (e.g. paper, plastic, cardboard, textiles);

• metals (e.g. magnetic – mostly steel, and non-magnetic – mostly aluminium); and

• inert materials (e.g. bricks, glass, rubble). The process stages are as follows:

• Collected curb-side waste is emptied from the vehicles into one of two 10m deep pits in the reception hall of the MBT facility that can hold over 2,000t of waste.

• A grab crane picks up 5t loads of waste and drops it into a shredder and the shredded waste output drops onto a conveyor.

• Shredded waste passes over a series of conveyors and mechanical screening and sorting equipment to separate out biodegradable waste (mainly food waste) and ferrous/non-ferrous metals from the other materials (see Figure 3—3).

• The separated ferrous / non-ferrous metals are sent for recycling.

• The remaining shredded material, mostly paper and plastics, is used to produce RDF.

• The separated biodegradable waste is sent to the digesters to produce biogas and digestate. The digestion is a conventional wet, mesophilic AD process using concrete tanks for the primary and secondary digesters (refer to Figure 3 - 4 ).

• The separated solid digestate is composted in tunnels to produce a ‘compost like output’ (CLO) that replaces soil as daily cover for the Brookhurst Wood landfill site.


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In the future the digestate may also be used for land remediation or dried to create a fossil fuel alternative.

• Rejects and waste residues that cannot be used or recycled are landfilled.

Figure 3—3 Sorting Lines at Brookhurst Wood

The MBT yields the following outputs:

• Dry recyclables: ferrous metals, non-ferrous metals;

• RDF;

• Biogas / Power and Digestate / ‘Compost-like-output’.

3.2.1.2 Operational Comment SLR notes from recent renewable energy output reports that the AD plant CHP engines have only operated at about 25-35% of design generation capacity. SLR understands that this is due to a combination of lower than expected rate of organics recovery from the mechanical separation plant and poorer quality (lower yield) recovered organics. M&W are working with Biffa to address this.


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Figure 3—4 Wet Anaerobic Digester at Brookhurst Wood

3.2.2 Case Study: Sant Antnin, Malta

The MBT facility at the Sant Antnin Waste Treatment Plant in Marsaskala, Malta was commissioned in 2010 to treat a single waste stream of c. 45ktpa MSW. Alongside the MBT, an MRF was installed (commissioned 2008) to handle co-mingled mixed recyclables.

The facility was developed by Waste Serv Malta Ltd with financial support from the EU Cohesion Fund.

The MBT receives MSW which is input to a process train of basic separation equipment, before the organic rich fraction is fed to an AD plant to produce biogas and power.

SLR have carried out a review of various Maltese facilities, advised on the implementation of a new incinerator on-site and completed waste characterisation studies on behalf of Waste Serv.


• MSW brought by collection vehicles is tipped on the floor of the reception hall.

• Tipped waste is then loaded to the bag opener.

• There is then recovery of metals (ferrous and non-ferrous), paper and dense plastics.


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• The organic rich fraction is separated out (mesh size of 50mm x 50mm) and blended with water for treatment in anaerobic digesters. Typically 30%-35% or 18,000tpa of input waste is recovered as organic rich fraction for treatment in a two-stage wet AD plant (refer to Figure 3 - 5).

• Equipment produced by the German technology provider HAASE is used throughout the plant.

• The output digestate (about 30% DS) is classed as waste and therefore is dewatered and landfilled.

• Rejects from the MBT are directed towards an adjacent MRF for additional recyclates recovery.

Figure 3—5 AD Plant at Sant Antnin (WasteServ Malta Ltd.)


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The MBT and MRF yields the following outputs:

• Dry recyclables: paper, card, plastics, ferrous metals, non-ferrous metals, glass (however principally from comingled recyclables input);

• Reject to landfill; and

• Biogas / Power and Digestate to landfill.


The site is of a similar scale to a potential facility that may be developed in Oxford County and with the associated MRF, is a possible solution for treating most residual residential and commercial wastes.

Relocation and/or an upgrade of the facility is the subject of current political discussions, especially now that the site is 8-10 years old. However, this is by no means its end-of-life.

• There are ongoing maintenance issues regarding grit accumulation11 in the hydrolyser (primary digester). This led to stirrer failure, and erroneous mitigation measures then led to major tank deformation.

• The biogas output of the AD plant also suffers due to the relatively poor quality of the MSW feedstock. This could be mitigated by implementing source-segregation of the feedstock or install of further pre-feed treatment unit operations.

• The AD plant also does not deliver in moving the output waste higher in the waste hierarchy – the digestate is still considered a waste and must be landfilled. Should the necessary pasteurisation and/or screening of the digestate be retrofitted then this may give Waste Serv more flexibility regarding its destination.

• The exhaust gas treatment (regenerative thermal oxidiser) is often turned-off as the plant ordinarily meets the required emissions limits. This was over-specified in the original design and has incurred unnecessary additional CAPEX.

The principal issue with the plant has been related to feedstock quality. It is important to characterise this fully prior to design; a developer should be cautious not to be over-optimistic about the quality of the feedstock.

3.3 MCA Scenario 4: MBT Comprising MRF Producing Recyclables and Organics plus Dry AD Organic Processing Stage in OC

3.3.1 Case Study: Western Isles Council, Scotland, UK

The Western Isles Council Waste Management Facility is located on the Creed Enterprise Park, Stornoway, Isle of Lewis, Scotland.

The facility receives three waste streams:

11Grit accumulation is a common problem with AD plants, particularly of this era before grit removal became the norm. MSW is a notably onerous feedstock and therefore high levels of grit are reasonably expected. Grit removal should be considered on any wet AD facility receiving MSW or source-segregated residential / commercial kitchen waste – unless quality is assured.


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• Source-segregated dry recyclables;

• Source-segregated bio-wastes (combined food and garden waste); and

• Residual waste. The Council wished to be self-sufficient in terms of waste management and preserve the limited landfill capacity available on the island. The plant has been operating since 2007 and treats 7,000tpa wastes, including food, paper and garden wastes and some fish wastes.

The biogas produced by the dry AD process is used in a 350kWe gas engine CHP unit and the waste heat used to maintain the thermophilic dry plug flow AD process. The AD plant has recently been upgraded to include a dedicated batch-pasteurisation step to enable it to accept more fish processing wastes generated from businesses in the islands.

SLR has recently conducted a HAZOP on recent plant modifications and also advised on a number of compliance issues related to the acceptance and treatment of wastes containing Animal By-Products.


3.3.1.1.1 Source-segregated Recyclables

The process stages are as follows:

• Metals are directed to a can separator to isolate ferrous from non-ferrous cans.

• Glass is input to a glass mill to reduce the sharps and enable local use as a decorative product in the islands.

• Paper, card, plastics and scrap metal are all bulked and baled for onward transport to re-processors on the mainland.

3.3.1.1.2 Source-segregated Bio-waste


• The input source-segregated biowaste is processed in a ’terminator’ shredder to reduce the particle size.

• Ferrous metals are then removed in a ferrous metal separator and conveyed to the on-site dry recyclable handling facility.

• The waste stream is directed to a screening drum. The oversize particles from the waste stream are returned to the shredder from the drum overflow.

• The remaining waste is then input into a dry AD plant provided by Linde/Strabag, with a residence time of 25 days.

• The biogas produced is then combusted in an on-site CHP engine with the electricity generated used to power the plant and the remainder exported. The output digestate is pressed in a screw press with the solid/fibre digestate then removed from site for beneficial application to land (including landfill restoration).


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3.3.1.1.3 Residual waste


• The residual waste is manually screened for bulky items which are rejected to landfill.

• The waste stream then undergoes the same principal process steps as the source-segregated bio-waste: shredding, ferrous metal removal, and then screening. However, in this instance, the screening oversize is rejected to landfill (refer to Figure 3 - 6).

• The organic rich underflow is fed to 2 no. ‘Hot Rot’ proprietary IVC units for stabilisation, before transfer off site.

Figure 3—6 Reception Hall at the Western Isles Council Waste Management Facility

The MBT yields the following outputs:

• Dry recyclables: mixed paper & card, ferrous metals, non-ferrous metals, mixed plastics; mixed milled glass [from source-segregated recyclables];

• Biogas / Power and Digestate [from source-segregated bio-waste];

• Compost (CLO) [from residual waste]; and

• Reject to landfill [from residual waste].


The Waste Management Facility is an example of a basic small-scale facility used to manage a low tonnage of waste in a remote location (i.e. without reserve waste infrastructure or immersed in a highly developed waste market).

The original design also made use of the same equipment for initial waste processing of two waste streams: residual waste + bio-waste. Therefore there was real emphasis in the design on minimising capital outlay.


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• Operationally the dry AD plant has struggled somewhat with low input tonnages. However, a pasteurisation stage was recently added (2017) to permit processing of fish wastes and therefore increase tonnages and power output

• Paper and card were originally input into the AD plant. It has been reported that the DS content caused operational issues and these inputs impacted significantly upon gas yield. The dry AD is therefore less flexible in reality than envisaged in the design.

• The major functionality issue has been related to the plant IVCs and indeed these have been out of commission since 2007. It is reported that the IVCs cannot maintain the minimum 6000Crequired to stabilise the residual waste and deem the output as compost. In the absence of other treatment facilities, including any thermal treatment, on the islands the residual waste now goes to landfill but the IVCs are still used to drive-off moisture and reduce the tonnage, to minimise the landfill tax incurred.

• It also has been retrospectively acknowledged that additional screening-out of 50%-75% of the eventual CLO would have been required for it to be diverted from landfill. Hence actual diversion tonnages would be down in comparison with the design basis.

• Inaddition, due to changes in legislation, this CLO would no longer be considered to be recycled material and therefore would not contribute towards achieving the relevant local authority diversion targets.

It is clear from these issues that the residual waste processing design, in terms of the basic unit operations was deficient, but also that insufficient due diligence on the specific IVC equipment was conducted.

3.3.2 Case Study: Tri-Municipal Region, Alberta, Canada

The Tri-Municipal Region of the Capital Regional District comprises the City of Spruce Grove, the Town of Stony Plain and Parkland County, Alberta. The Region has a population of around 80,000, generating around 29,000tpa MSW, prior to diversion. The Region also generated around 30,000tpa of IC&I waste, the majority of which was landfilled at sites controlled by the Region.

Supported by funding from Alberta Innovates, the Region jointly commissioned a study in 2015 comprising a review of waste treatment technology which could improve landfill diversion, selection of a preferred mix of technologies that had achieved a maturity level adequate for implementation and the preparation of a detailed conceptual (Pre FEED) design, from which detailed CAPEX and OPEX estimates could be derived.

The two main settlements have blue box collections in place as well as a modest curbside organic collection system in part of the City. However, it was considered by the Municipalities that source-segregated organics were unlikely to be cost-effective over much of the remainder of the Region.


The current design involves a technology mix comprising:

• A dirty MRF accepting up to 40,000tpa, which would generate the following outputs;


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o 16,000tpa organics-rich fines; o 4,000tpa dry recyclables (metals, plastics, cardboard); o 16,000tpa mixed non-organic fraction (potentially suitable for RDF production,

but initially landfilled until plant is available); and o 4,000tpa residual non-organic fraction to landfill.

• A high-solids, dry AD plant, accepting 4,000tpa of source-segregated organics and the 16,000tpa of organic rich fines from the MRF, which would generate the following outputs:

o Bio-gas converted via a CHP plant to electrical power of up to 3,700MWh/a and heat energy of up to 4,400MwH/a;

o 20,000tpa of digestate, converted to compost in tunnels; and o Up to 2,000tpa of rejects to landfill.

There are currently either no suitable facilities or insufficient capacity at existing facilities to allow RDF to be used in EfW facilities. The options under consideration include either awaiting the availability of such capacity in the Region or developing a dedicated supplementary facility on site, subject to funding and regulatory approval.

The design includes provision for the expansion of the inputs to the facility by 50%, either by capturing a greater proportion of the IC&I waste in the local market, or by attracting MSW or IC&I wastes from neighbouring jurisdictions.

A Class C cost estimate was prepared for the proposed facility and indicated the following CAPEX elements. Note that there are likely to be significant potential savings resulting from a formal procurement process and an opportunity for a contractor to seek synergies between the various design elements. AD facility: $15 million; Dirty MRF: $10 million; and Balance of plant: $25 million.

Estimated operating costs, excluding cost of capital, were as follows: AD operations: around $31 per tonne; and Dirty MRF operationst: around $39 per tonne.

Funding costs will vary significantly between projects and owners, but for guidance it was estimated that overall annual operating costs for the whole facility, including cost of capital, might be in the order of $140/t. Grant funding may be available to support investments of this nature.


The facility is still at the funding approval stage, therefore it is not possible to make any specific comments about future operations. However, if successfully implemented, and following identification of a suitable RDF user, the facility should enable the Region to achieve a net landfill diversion of around 90%. A conceptual design of the facility is shown in Figure 3-7.


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Figure 3—7:

Conceptual design of Combined MRF and High-solids AD plant, Tri-Municipal Region, AB

(Note: Figure provided by Morrison Hershfield)

3.4 Lessons Learned

In compiling the bulleted items in the operational narratives above, a series of headline themes were identified in the lessons learned. These are listed below:

• It is important to characterise the waste stream accurately to serve as the facility design basis. An unexpected waste stream composition will lead to a poorly specified and designed facility.

• Consideration should be given to future potential changes in the waste streams – for example due to future revision of collection mechanisms. It is recommended that facilities are future-proofed as far as reasonably possible to offer maximum flexibility.

• An awareness of the general direction of federal/provincial level legislation relating to waste treatment is also valuable as future changes to these may influence the process inputs or target outputs. This is also an element of future-proofing the facility.

• A competent Technical Advisor or Owner’s Engineer should be appointed to represent the public sector organization, unless sufficient expertise resides in-house. Failure to interrogate contractor’s proposals with the appropriate technical expertise may also lead to a poorly specified facility.

Documents

3.0 TASK 2: CASE STUDIESOF IMPLEMENTED TECHNOLOGIES 3.1 MCA Scenario2: MRF … Waste... · 2017. 8. 24. · 3.2 MCA Scenario 3MBT C: omprising MRF Producing Recyclables and Organics