Feasibility study Micro-scale anaerobic digester - DIAD 2 feasibility study.pdf · 1.1 Feasibility study objectives This report details the results of a feasibility study to install

Feasibility study

Micro-scale anaerobic digester

Installing a micro-scale anaerobic digester on the Building Research Establishment site, investigating costs, benefits and technical issues

Project code: OIN001-010 PO:1909 Research date: 1/4/13 – 28/6/13 Date: November 2013

WRAP‟s vision is a world where resources are used sustainably. We work with businesses, individuals and communities to help them reap the benefits of reducing waste, developing sustainable products and using resources in an efficient way. Find out more at www.wrap.org.uk This report was commissioned and financed as part of WRAP‟s „Driving Innovation in AD‟ programme. The report remains entirely the responsibility of the author and WRAP accepts no liability for the contents of the report howsoever used. Publication of the report does not imply that WRAP endorses the views, data, opinions or other content contained herein and parties should not seek to rely on it without satisfying themselves of its accuracy.

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

Written by: Ian Barnett, Gilli Hobbs and Robin Wiltshire of BRE

Front cover photography: BRE Innovation Park in Watford, UK

While we have tried to make sure this report is accurate, we cannot accept responsibility or be held legally responsible for any loss or damage arising out of or in

connection with this information being inaccurate, incomplete or misleading. This material is copyrighted. You can copy it free of charge as long as the material is

accurate and not used in a misleading context. You must identify the source of the material and acknowledge our copyright. You must not use material to endorse or

suggest we have endorsed a commercial product or service. For more details please see our terms and conditions on our website at www.wrap.org.uk

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

Micro-scale anaerobic digester 1

Executive summary

This report summarises the work carried out by Building Research Establishment (BRE) to consider the feasibility of installing and operating a micro-scale anaerobic digestion plant. Key elements of the feasibility study are described below and included in this report. The objective of the feasibility study was to evaluate the potential to install a micro anaerobic digestion plant which, if installed, would produce biogas for use on the BRE site. The feasibility study considered more than just the technical aspects, including opportunities such as integrating the plant into BRE‟s Innovation Park, and awareness raising through collection and treatment of waste from nearby schools and organisations to provide a community-based scheme for extracting the energy value from food waste and green waste. The main output of the feasibility study has been to produce a detailed design for the system to enable the location, costs and benefits to be explored further for the business case to the BRE board. Clarification of issues such as dealing with the digestate, use of the gas and specifications required, training requirements and quantification of available feedstock were also carried out. The system design is presented within this report with an explanation of the elements in the system and why each one is necessary or is the preferred option. Due to the infancy of small-scale anaerobic digestion in the UK, areas of uncertainty arose throughout the project which would require further investigation before commissioning of a system took place. This includes regulatory requirements, maintenance and operational considerations. Realistically, this technology will only be installed if the economic viability was demonstrated. Therefore, a key element of the feasibility study was to assess costs and benefits over the planned operating period to establish overall payback. Overall, the cost benefit analysis predicts that the installation could see a payback period of around 5.5 years, assuming additional financial support from WRAP, and a potential benefit of around £200,000 over a 20-year period through savings in waste costs, gas consumption and subsidy generated through the Renewable Heat Incentive (RHI). Without additional financial support from WRAP, the payback period increases to around 16.5 years. Since undertaking the feasibility study, a business case was produced and discussed by the BRE board. There was verbal agreement to proceed to demonstration (phase 2), subject to receiving additional financial support from WRAP. However, the application to receive phase 2 funding was not successful, so it is unlikely the demonstration will proceed in the short term.


Contents

1.0 Introduction and background: ...................................................................... 4 1.1 Feasibility study objectives .......................................................................... 4 1.2 About anaerobic digestion ........................................................................... 4 1.3 About BRE and Green Gas Technologies ....................................................... 5 1.4 Issues influencing AD on the BRE site .......................................................... 6

2.0 Methodology of the feasibility study ............................................................ 7 2.1 Feedstock .................................................................................................. 7 2.2 Location .................................................................................................... 7 2.3 Process and plant ....................................................................................... 8 2.4 Biofuel ...................................................................................................... 8 2.5 Digestate ................................................................................................... 8 2.6 Scalability .................................................................................................. 8 2.7 Planning and regulation .............................................................................. 9 2.8 Costs ........................................................................................................ 9 2.9 Benefits ..................................................................................................... 9 2.10 Any other issues ........................................................................................ 9

3.0 Results ........................................................................................................ 10 3.1 Feedstock ................................................................................................ 10 3.2 Location .................................................................................................. 10 3.3 Biogas ..................................................................................................... 12 3.4 Process and plant ..................................................................................... 13 3.5 Digestate ................................................................................................. 16 3.6 Scalability ................................................................................................ 16 3.7 Planning and regulation ............................................................................ 17 3.8 Costs ...................................................................................................... 17 3.9 Benefits ................................................................................................... 18 3.10 Other sources of funding .......................................................................... 18 3.11 Any other issues ...................................................................................... 19

3.11.1 Operational ................................................................................... 19 3.11.2 Training ........................................................................................ 19 3.11.3 Health & Safety risk assessment ...................................................... 19

3.12 Competing technologies ............................................................................ 20 3.12.1 Biomass boiler systems ................................................................... 21 3.12.2 Combined heat and Power .............................................................. 21 3.12.3 Heat pumps ................................................................................... 21

4.0 Economic / Cost Benefit Analysis ............................................................... 22 4.1 Environmental Benefits ............................................................................. 23

5.0 Conclusions ................................................................................................ 24 Appendix A – Sources of external waste .............................................................. 26 Appendix B – Potential locations for AD system .................................................. 27 Appendix C – Cost benefit analysis data .............................................................. 32


Figures

Figure 1 BRE site layout and proposed locations for small-scale AD system ...................... 11 Figure 2 Schematic of the proposed BRE Anaerobic Digestion plant. ................................ 15

Tables Table 1 Options for location based upon biogas use ......................................................... 7 Table 2 organic waste produced on BRE site: ................................................................ 10 Table 3 Waste available from external sources: ............................................................. 10 Table 4 Anticipated biogas production from small-scale AD plant based on two feedstock scenarios ..................................................................................................................... 12 Table 5 Predicted levels of biofuel and biofertiliser ......................................................... 16 Table 6 Cost breakdown regarding BRE AD equipment and other costs - initial ................. 18 Table 7 Renewable heat source technologies which have been ruled out in the first instance summary ..................................................................................................................... 20 Table 8 Comparison of costs, benefits and payback periods for different scenarios ........... 22

Acknowledgements

This report was commissioned and financed as part of WRAP‟s „Driving Innovation in AD‟ programme. The report remains entirely the responsibility of the author and WRAP accepts no liability for the contents of the report howsoever used. Publication of the report does not imply that WRAP endorses the views, data, opinions or other content contained herein and parties should not seek to rely on it without satisfying themselves of its accuracy.


1.0 Introduction and background: 1.1 Feasibility study objectives This report details the results of a feasibility study to install a small scale Anaerobic Digestion (AD) system on the BRE site. The immediate objectives of the feasibility study were to:

Work out the best solution to the issues (section 1.4) surrounding AD and the BRE site.

Present evidence to the BRE board relating to the practical and financial feasibility of

installing an AD system on the BRE site.

The wider objectives of installing an AD system would be to:

Reduce disposal costs for segregated organic waste arising from the BRE site.

Reduce environmental costs associated with transporting segregated organic waste to an

external AD facility.

Provide partial replacement of natural gas with biogas to reduce costs and environmental

impact of our operations.

Produce other biofuels and biofertilisers, where appropriate for the system installed.

Create a new feature for the Innovation Park to raise awareness of AD to the construction

sector.

Create new knowledge in relation to combining AD with heating networks (also called

district heating).

Develop a new business area at BRE providing support for those wanting to combine AD

with the provision of heat and/or power to buildings.

Buildings in the UK use a lot of heat, contributing to around 75% of the overall carbon emissions associated with buildings. The UK is very dependent on gas to supply this heat which is an increasingly expensive resource. Therefore, any biogas or biofuel that can be produced to feed into a conventional boiler or to a dedicated biofuel boiler will contribute to the reduction of carbon emissions from buildings. 1.2 About anaerobic digestion1 AD involves the breakdown of biodegradable material in the absence of oxygen by micro-organisms called methanogens. Anaerobic digestion (AD) has been utilised by farms and wastewater treatment plants for a number of years. Large scale anaerobic digestion is also establishing itself as a viable process, with a number of large scale plants being built and operated in the UK and other parts of the world dealing primarily with food waste. There are two main types of anaerobic digestion called thermophilic and mesophilic – the primary difference between them is the temperatures reached in the process. Thermophilic processes reach temperatures of up to 600C and mesophilic normally runs at about 35-400C. The system chosen will largely depend on the feedstock to be processed. For example, 'high solid materials', such as a garden and food waste mixture, tend to be processed at a thermophilic temperature using the batch system, while 'low solid materials', such as animal slurry mixed with industrial and municipal food wastes, are more likely to be processed at a lower temperature using a continuous flow system.

1 From WRAP web site - http://www.wrap.org.uk/content/anaerobic-digestion-1

http://www.wrap.org.uk/content/anaerobic-digestion-1


The process of anaerobic digestion provides a source of renewable energy, since the waste is broken down to produce biogas (a mixture of methane and carbon dioxide), which is suitable for energy production. The biogas can be used to generate electricity and heat to power on-site equipment and the excess electricity can be exported to the National Grid. Other possible uses for the biogas currently being explored in the UK include injection to the gas grid and using it as a vehicle fuel. A further by-product of the process is biofertiliser, which is rich in nutrients such as nitrogen, phosphorus and other elements required for healthy plant growth and fertile soil. 1.3 About BRE and Green Gas Technologies BRE helps government, industry and business to meet the challenges of our built environment. BRE is an independent and impartial, research-based consultancy, testing and training organisation, offering expertise in every aspect of the built environment and associated industries. The BRE Trust was set up in 2002 to advance knowledge, innovation and communication for public benefit. BRE is a subsidiary company of the BRE Trust. As well as our Watford Headquarters (which is where the feasibility study was focussed), we operate from regional offices in the North West and West Midlands of England, and in Scotland and Wales. BRE has a challenging set of sustainability targets governing its own operations – these are embodied in our S-Plan. Established in 2008, this set about transforming the way that BRE thinks about and acts on sustainability within the business. The S Plan sets out a four-year programme of continuous improvement from 2008 - 2012 across eight key areas of sustainability: carbon dioxide (CO2) emissions; community engagement; ecology; information systems; resource efficiency; supply chain engagement; transport; and water. Most of these areas are on track to meet the targets or they have been exceeded. The next phase of S-Plan is being considered at the moment and will require further challenges to be set, some of which will require significant investment to achieve in practice. This is where the key driver for developing an on-site AD applies. BRE are keen to showcase innovation and drive down impacts on our own site. BRE has a great deal of expertise in heating and powering buildings and optimising the use of renewable energy in buildings. We also have centres of expertise dedicated to resource efficiency, air quality, testing and monitoring, and the provision of mechanical and electrical services. Green Gas Technologies were the AD technology providers working with BRE to carry out the feasibility study, in particular in developing the design of a suitable process and plant given the specific circumstances of the BRE site and feedstock. Green Gas Technologies are an engineering company from Norway, partnering with React Environmental, to bring small-scale farm-based AD into the UK. Their team members have a wealth of experience in small-scale AD and have developed systems in both Europe and Africa. Green Gas Technologies have worked with partner engineering companies to develop the small-scale AD system in Wales. Working with React Environmental, they have designed and constructed a demonstration plant to treat up to 1500 tonnes/year of food waste in Llangadog in Camarthenshire. The plant is fully licensed with an Environmental Permit, planning permission and a licence to operate from the State Veterinary service. This plant is currently going through the process of getting the digestate PAS 110 certified.


1.4 Issues influencing AD on the BRE site The issues that this study had to consider were that of technical and financial viability for small-scale anaerobic digestion on a business premises. As well as serving this purpose, a BRE AD plant could reach a large audience with its incorporation into the BRE Innovation Park. This is visited by thousands of people each year, from school children to international delegates and politicians, and offers an excellent awareness raising opportunity for the technology. The AD installation could also explore the way in which feedstock sourcing can be innovatively achieved at a local community level, by the use of food waste from local schools and businesses. The issues which were considered include:

Feedstock - what organic material is available for anaerobic digestion, and how much?

Location – where could be AD plant be located to optimise efficiency and minimise

disruption to the rest of the business?

Process and plant – given the feedstock and the possible use of the biogas, what would

be the best process and plant?

Biofuel – what would be produced and how could it be used?

Digestate – what would be produced and how could it be used?

Scalability – are there opportunities to scale up the system?

Planning and regulation – what would be planning and regulatory implications of a

proposed system?

Costs and benefits – what would be the costs and benefits of the proposed system?


2.0 Methodology of the feasibility study The work undertaken in this study was a desk based assessment of installing an AD system on the BRE site which could possibly be integrated into an existing district heating system. This section provides more detail on the issues that needed to be considered and the method of finding out the necessary information. 2.1 Feedstock The main issue was to establish the type and amount of feedstock available on the BRE site. However, in terms of scaling up at a future date, it was also considered important to determine the potential to source further feedstock from nearby. In summary, the study looked at:

BRE source-separates various on-site putrescible wastes that could be suitable feedstock,

namely food waste and green waste

Options to increase feedstock through taking in food waste/putrescible waste from

external schools and businesses. Work was carried out to understand how much material

could be available, the locations and the likely costs and benefits of collection. This was

called „a feedstock mapping exercise‟.

2.2 Location BRE has a large site with a multitude of options available for locating the AD plant. However, proximity to the building using the heat would minimise heat losses in heating applications, and proximity of the AD plant to a suitable boiler would minimise excavation and pipework costs and disruption. This needed to be set against the practicalities of an operating AD plant, such as space, access, air quality and potential odour issues. Three potential options were considered. These are indicated in Table 1.

Table 1 Options for location based upon biogas use

Preference Option Description

1 B14 district heating

This option would see the AD plant located and incorporated within the BRE Innovation park, whilst also serving one of BRE's office buildings. An advantage of having the plant close to B14 is its proximity to the BRE Innovation Park which attracts thousands of visitors per year. The AD plant and heat network would be additional features for the Innovation Park, giving a more complete picture for visitors of future low carbon community solutions.


2 B7 Industrial gas injection

Building 7 is a furnace hall used for industrial fire testing on the BRE site. This has high gas consumption throughout the year. Gas from the AD plant would thus be injected directly into the gas supply to this building whilst still being available to view during innovation park tours.

3 Innovation Park heating grid

The innovation park is to undergo a substantial re-design. This will feature more than micro-generation such as solar PV, solar thermal and wind, and thus a micro anaerobic digester could feature prominently in its new design. The gas would supply heat to a district network and would serve as a direct showcase of innovation as well as serving the purpose of heating all buildings on the park. These buildings are used both for tours and work activities and thus serve as a legitimate heating requirement.

2.3 Process and plant Collaboration with leading industry experts was crucial owing to the atypical nature of what was being proposed, in terms of scale, feedstock and application. Small-scale AD systems which utilise food and green waste only are very uncommon, thus any plant needed to be specifically designed, rather than there being off-the-shelf solutions or existing examples to adopt. 2.4 Biofuel The main biofuel would be biogas and there were a number of options considered in terms of its use. Heat generated in the system would be needed to maintain the AD process. 2.5 Digestate Dealing with the digestate needed consideration as to what form it would arise and how best to deal with it, either off or on site. Digestate is a biofertiliser and BRE has requirements for landscaping fertiliser on its site and there is also a landscaping firm that rents space on the site. Other options included agricultural and horticultural applications, both of which can be found nearby to BRE‟s site. 2.6 Scalability Future opportunities to scale up operation and output based upon future plans for the BRE site were considered in the design of the system. This included possible development of a mini heating grid for the BRE Innovation Park.


2.7 Planning and regulation An evaluation of the planning and environmental regulation requirements for the AD system needed to be undertaken and factored into the decision making process. This included an assessment of the likely permitting regime that would apply to the plant (e.g. an exemption, a standard permit or a bespoke permit) and the implications on cost. This also included a consideration of complying with the requirements of the animal by-products regulations, and quality standards such as PAS 110 and the AD Quality Protocol. 2.8 Costs To produce the business plan for the BRE, the following costs would need to be calculated: Initial costs -

Cost of plant and equipment

Site preparation

Commissioning costs

Permitting/planning costs

Waste container costs

Educational materials

Ongoing costs –

Training of facilities management staff

Time needed to operate the system

Maintenance time and costs

Testing of outputs

Transport (if bringing in material from outside BRE and possibly for exporting digestate)

2.9 Benefits Set against these costs, were the benefits thought to derive from installing the planned system on the BRE site. These included:

Reduction in waste disposal costs for segregated organic waste (BRE only)

Biogas revenue in terms of the Renewable Heat Incentive (RHI)

Reduction in primary gas costs through partial replacement with biogas

Value of other biofuels and biofertilisers that may arise

Possible gate fee, if accepting organic materials from outside the BRE site.

2.10 Any other issues The BRE site operates within stringent health and safety protocols, so it would be important to fully understand exactly how the plant and process would be tested, operated and maintained to ensure risks were kept to a minimum. In addition, the ability to showcase innovation to the many visitors and school children who come to the Innovation Park was considered. This was an important aspect of locating the system, as well as factoring in design elements that could promote better understanding of the technology.


3.0 Results This section outlines the results from the feasibility study, focussing on the preferred options and specific requirements that would need to be considered in further developments to installation of an AD system on the BRE site. 3.1 Feedstock From the feedstock mapping exercise that was been undertaken, there would be access to material as detailed in the Tables 2 and 3 below. Data provided in table 3 is estimated from the approximate food/green waste arisings from external organisations who stated they would want to send their material to a possible AD facility located at BRE. Collection and gate fees were assumed for the purposes of the overall cost benefit analysis as it was not possible to get accurate data for these from the organisations we spoke to, many of which are tied into mixed trade waste collections currently. It was decided that any demonstration would be commissioned using BRE based feedstock alone, owing to the time and resources that would be required to gain the necessary approvals to accept external waste for treatment. Therefore, during the first years of operation the facility would only utilise BRE‟s own food and green waste (Table 2). During this period, additional work would be undertaken to ensure external waste could be treated in compliance with relevant legislation. This would also be an appropriate stage to consider supplementing feedstock at certain parts of the year to smooth out seasonal variation in relation to green waste.

Table 2 organic waste produced on BRE site:

Waste stream Weekly average (tonnes) Annual total (tonnes)

Food 0.480 24

Green 0.940 45

Total 1.420 69

Table 3 Waste available from external sources:

Waste stream Weekly average (tonnes) Annual total (tonnes)

Food 0.475 24

Green 1.575 81

Total 2.050 105

The external sources from which BRE could collect waste are available to view in Appendix A. It was recognised that the availability of green waste would be seasonal, therefore variation of feedstock should be considered within the design of the process and plant. 3.2 Location The possible location of the AD plant was determined by utilising in-house knowledge of past and possible future developments on site, including what spaces were available close to possible end uses. How suitable these areas were was then assessed in terms of current land use, whether they were on hard standing, would require the excavation of existing hard


standing for pipework and how easily they could be connected to their end uses. Reducing the distance from end use was also an important parameter. Understanding the future development plans for certain buildings and the site as a whole was important in determining the long term viability for the AD plant. Figure 1 illustrates the BRE site and the 5 sites which were analysed as part of the feasibility study.

Figure 1 BRE site layout and proposed locations for small-scale AD system

1 Area 68 2 B 14 visitors‟ car park / Innovation Park 3 North field 4 Exposure site to the North of B 7 5 B 20a & B 20b (Geolabs‟ open storage) (Now rejected)


Requirements considered in terms of location included:

Gas is produced 24 / 7 so ideally a location close to a year-round consumer is needed to

avoid lengthy trench work for underground services

Physical requirements – dimensions 9.5 x 30 Metres minimum. Level / slope, surface and

specific loadings unknown

Access for heavy vehicles

Electricity supply requirements

Water supply requirements

Storage of waste and solid output material

Planning permission

Environmental permits

If not immediately consumed, gas can be stored – low pressure storage is bulky but lower

risk than high pressure storage.

Foul drainage connection

Surface drainage should not be impacted but environmental protection will be needed

Access for visitors and school children

Our main concerns were the issues of offensive smells and the potential hazard of flammable gas storage close to highly populated areas. Further detail relating to these sites is available to view in Appendix B. Locations 2 and 4 are the best in terms of proximity to direct use of the biogas. Any further development to demonstration phase would focus on these areas. The main deciding factor would be related to the end use of the biogas. 3.3 Biogas Green Gas Technologies provided BRE with estimation tables based on the feedstock available; these are summarised in Table 4.

Table 4 Anticipated biogas production from small-scale AD plant based on two feedstock scenarios

Per year quantities, based upon BRE feedstock only

Feedstock Type Quantity

(tonnes)

Methane

content of gas produced (%)

Energy

production (MJ)

Energy

production (kWh)

Biogas

production (m3/year)

Food waste 23 65 70549 19597 3015

Separator fat/oil 1 70 7371 2048 315

Grass cuttings 45 60 103194 28665 4410

Total 69 - 181114 50310 7740


Per year quantities, based upon BRE and external feedstock

Feedstock Type Quantity

(tonnes)

Methane content of gas

produced (%)

Energy production

(MJ)

Energy production

(kWh)

Biogas production

(m3/year)

Food waste (avg) 47 65 144165 40046 6161

Separator fat/oil 1 70 7371 2048 315

Grass cuttings 90 60 206388 57330 8820

Total 138 - 357924 99423 15296

Based upon these projections, and after removing the biogas requirement to maintain the system (the parasitic load), it was clear that there would be potential for partial natural gas replacement in two uses: 1 The heating requirement for B14 and B17, which have a shared energy centre. This

would illustrate, to a certain extent, the possible integration of AD into heating networks. However, the demand for heat is seasonal so a use for the biogas outside of the heating months would need to be developed in more detail for any follow up demonstration.

2 The furnace hall (B7) has a large and continuous natural gas requirement. Therefore, this would be an ideal use for the biogas in terms of partial replacement. However, in terms of replicability, it is an unusual application.

In larger systems, it would be viable to add a combined heat and power (CHP) boiler to the system that would convert the biogas to electricity with a heat residual that could be used to provide hot water. For example, as is typical for waste to energy incinerators providing local district heating. However, the small-scale of the proposed system, even including external feedstock, is not economically viable for CHP. 3.4 Process and plant Technical details regarding equipment to be used on the BRE site required input on:

Plant design and capabilities

Biogas production

Site layout and history

Green Gas Technologies developed a system that would work effectively with the requirements relating to input material, end use of outputs and operating the system. This would be a bespoke solution based upon previous systems developed elsewhere. Site visits were made by Green Gas Technologies so that they could analyse and assess the options which the BRE site could accommodate regarding space and other technical aspects. BRE‟s own on site M&E Engineers were involved so that they could liaise with external experts and help with the identification of technical possibilities. Following these discussions, the key objective for the plant and process was developed: „The objective of this system design is to take organic waste, comply with all relevant regulatory requirements, extract the biogas for use as a fuel; remove remaining nutrients to use as a dry fertiliser, leaving clean water for re-entry to the system or use in irrigation, or release in to natural water courses. At this scale of operation, costs and complications need to be kept to a minimum.„ Consequently, the preferred approach would be to house the process in two 40ft containers, with a low pressure biogas store nearby. The system would be controlled and monitored by


a Programmable Logic Controller (PLC). This would be housed in one of the containers, together with a gas-fired boiler that could also be used to supply heat directly to a heating network. We would consider windowing the containers, but this may not be possible if it affected the integrity of the container in terms of strength and insulation. An alternative would be to have display boards illustrating the inner working attached to the relevant part of the container externally. The system would include the following elements:

Receiver Unit that takes food and soft garden waste (grass and non-woody plants) where

they are chopped, macerated and mixed with water to form an input feedstock of circa

12% dry matter with solids no greater than 12mm on any given surface.

Thermophilic Hydrolyser & Pasteuriser with a multi-chamber design that ensure a

minimum retention time of greater than 12 hours and a temperature of 55°C . This

ensures pasteurisation of the feedstock, as required by the ABP Regulations.

Solids Separator removes non-hydrolysed solids from the substrate for solids greater than

3mm on any given surface. The solids are primarily cellulose based particles with free

lignin. The solids from this first separator can be used for pellets, composting or as a soil

conditioner.

Mesophilic (Methanation) Digester operating in the mesophilic digestion range; digests

remaining liquor to dry matter content around 1%.

Nutrient Separator and Digestate Cleaner separates all remaining solids and all suspended

nitrate, phosphate and potassium leaving process water that can be recycled to the

Receiver Unit. The extracted solids comprise primarily crystalline nitrates, phosphates and

potassium with trace elements such as iron, magnesium etc. The nutrients from this final

separator can be used as a dry fertiliser to replace industrial fertiliser.

The Base Structures Biogas Store provides short term, low pressure storage. It is a double

membrane gas bag system capable of storing volumes of 25m3 to 5 000m3.

Figure 2 provides a schematic of how these elements would fit together.


Figure 2 Schematic of the proposed BRE Anaerobic Digestion plant.

Once a commissioning trial was complete, monitoring of the system should have indicated that conservative projections of biogas production and feedstock potential were correct, proving the system to be on track to deliver the benefits envisaged. The process, as designed, would meet the necessary quality standards and regulations, including PAS 110, AD Quality Protocol and ABPR. This would need to be supplemented with a detailed quality management system for any further development, i.e. should the system be commissioned. This was not developed as part of the feasibility study.


3.5 Digestate Digestate in its unprocessed form would be predominantly liquid, requiring storage and bulk transfer to a nearby farm. This presented several concerns, including:

Cost and location of storage of digestate

Cost of transfer to end user, e.g. local farm

Lost opportunity to make use of the material on-site.

Therefore, it was decided that the system needed to incorporate a dewatering stage. This would effectively remove the water from the digestate and return it to the system. This would result in two outputs – biofuel and fertiliser. Both these materials could be sold or used on-site to replace other manufactured products. Therefore, the proposed system would have two potentially saleable outputs: biofuel and biofertiliser. The approximate amounts that might be produced are summarised in Table 5 below.

Table 5 Predicted levels of biofuel and biofertiliser

Biofuel and biofertiliser production - BRE feedstock only

feedstock Biofuel production t/yr

Nitrogen t/yr

Phosphorus (P2O2) t/yr

Potassium (K2O) t/yr

Food waste 1.38 0.4186 0.0276 0.0115

Green waste

1.8 0.2835 0.0945 0.3015

Biofuel and biofertiliser production - BRE and external feedstock

feedstock Biofuel production t/yr

Nitrogen t/yr

Phosphorus (P2O2) t/yr

Potassium (K2O) t/yr

Food waste 2.82 0.8554 0.0564 0.0235

Green waste

3.6 0.567 0.189 0.603

In terms of application of biofuels, there are biomass boilers on the BRE site that could use this material. Alternatively, staff would be interested in purchasing this material. In terms of the biofertiliser, again there is a need for such materials on the BRE site. Alternatively, the BRE Gardening Club would be a good route to a local market. 3.6 Scalability The main opportunity to upscale the effectiveness of the system would be to combine with other renewable technologies and connect to a heating network, commonly known as district heating. This could be combined with redevelopment of part of the Innovation Park site with the incorporation of a heat network to provide heat to buildings on the park, as opposed to each building having its own central heating and boiler system. District heating provides an opportunity to make efficient use of the heat produced from AD and its outputs. Resources can be combined and optimised to cope with seasonal variations in supply and demand, and the use of thermal stores can help in coping with daily variations in supply and demand. BRE is at the forefront of developing district heating in the UK, both in terms of regional planning and infrastructure and practical implementation, including a


regional events programme attended by town and city planners interested in developing district heating with renewable energy, and have recently completed a study for DECC relating to barriers and opportunities for district heating in the UK. Therefore, any future developments to integrate the benefits of AD with those of District Heating would be based upon a strong technical capability in this area. Some of the issues that arose when evaluating if it could be achieved on the BRE site included:

Availability of heating grids in relation to possible locations of and AD system, bearing in

mind loss of efficiency over distance

Combination of AD biogas with other renewable energy sources that could contribute to

district heating, such as biomass and solar thermal

Seasonal variation of heat demand and possible thermal storage solutions

From a practical perspective, it was decided that the scale and likely location of a potential AD plant on the BRE site would not be compatible with the district heating requirements. However, BRE will be looking to explore AD options further on district heating projects we get involved in. 3.7 Planning and regulation BRE planning experts have advised that it should not be complicated to obtain the required permission owing to the nature of the system, i.e. containerised and therefore not permanent built structures. However, we would need to go through a process of ensuring compliance with the following:

Planning permission

Exemption/ Environmental permit

APBR.

PAS 110

AD Quality Protocol

The system has been designed to incorporate the requirements under APBR and facilitate use of the resultant bio-solids in a range of applications. Our current understanding is that using BRE only feedstock would enable the system to be operated under an exemption (from environmental permitting). However, if waste is received from external sites, the process of securing an environmental permit for all the relevant processes and equipment would need to be carried out. Generally, if canteen waste forms part of the feedstock, the process will be subject to Animal By-Products Regulations, which means the plant has to be approved by the Animal Health Veterinary Lab Agency (AHVLA). Low-risk animal by-products in the plant can be used, i.e. already passed as fit for human consumption (or Category 3 under the regulations). It also means that the process has to reach a certain temperature for a prescribed retention time, there is a restriction on animals grazing on land on which this material has been spread, and various testing/quality regimes need to be followed. Should the demonstration phase proceed, these issues would be investigated in greater detail. 3.8 Costs The total project costs were calculated to be £176,500 (Exc. VAT. This cost has been calculated utilising data from scenario 1, BRE feedstock/waste only. The cost breakdown is provided in Table 6.


Table 6 Cost breakdown regarding BRE AD equipment and other costs - initial

Item Description Unit Cost Units Total

Plant and equipment

Containers £5,393.26 2 £10,786.52

Pasteurisation/Hydrolysis £16,853.93 1 £16,853.93

BS Liners £3,370.79 1 £3,370.79

Front-End Separator £22,471.91 1 £22,471.91

PLC £11,235.96 1 £11,235.96

Engineering [£/hr] £95.51 300 £28,651.69

Nutrient separation £33,707.87 1 £33,707.87

Total £93,129.21 1 £127,078.65

Other costs

BRE commissioning £30,000.00 1 £30,000.00

Site Preparation £10,000.00 1 £10,000.00

Waste containers £3,000.00 1 £3,000.00

Educational materials £3,500.00 1 £3,500.00

ATEX Training £3,000.00 1 £3,000.00

Total £59,500.00 - £49,500.00

- - £176,578.65

In addition, labour costs of £5,600 per year, and testing costs of £1000 per year, rising with inflation, are estimated to be the ongoing costs. Replacement costs also needed to be factored in, but these are highly speculative at this stage. Scenario 2 considers the addition of external feedstock. However, this has additional costs of securing the required environmental permits and collection of the waste as an ongoing cost. In terms of calculating the costs and benefits, it has been assumed that an additional £10,000 would be needed for environmental permitting and that the gate fees would be roughly equivalent to the costs of collection, thus they would cancel each other out. 3.9 Benefits Financial benefits which could be derived from this project include incomes derived from:

BRE waste cost reductions – currently £8,300 per year.

Renewable Heat Incentive (RHI) payments; based on biogas produced – currently 7.3

p/KWh

Gas bill cost reductions – currently 4 p/KWh

Selling biofuel and biofertiliser – assumed £100/tonne for biofuel. An assumption of

£133/tonne, £240/tonne and £600/tonne of nitrogen; potassium and phosphorus levels

respectively was also made (though it would be more likely that a flat rate per kilo of

biofertiliser would be calculated with respect to sales to the site and staff)

Gate fees for waste collection from external premises; it was assumed that this would be

negated by the cost of collecting waste.

3.10 Other sources of funding To improve the financial basis against which costs are allocated, funding is being sourced from three parties. These are illustrated below, along with the proposed contributions from each party:

BRE – £58,750


Green Gas Technologies – £38,000

WRAP – £89,750

Green Gas Technologies have agreed to reduce their costs as indicated above, should the demonstration go ahead using their plant and process. The BRE board is open to low carbon investment cases that have a reasonable payback term, a match funding arrangement is envisaged, rather than BRE having to meet the full cost. WRAP have since rejected an application to financially support the demonstration (phase 2). 3.11 Any other issues 3.11.1 Operational BRE have a directly employed facilities management team who would be trained to operate the plant and a maintenance schedule would need to be developed. A member of the facilities team was part of the project team carrying out this feasibility study. The main issues that were considered included:

Training to understand the system and operate it effectively

Time taken to load/unload the system

Routine maintenance requirements

The estimated time and resource costs for the above were collated and included in the cost benefit evaluation. A specific cost line was developed for external training, hence an external cost. 3.11.2 Training There would be a requirement to train at least one electrician to be able to work in a gas environment. The details of this training are summarised below with indicative costs:

Foundation course (2 days) £385

CompEx EX01 - EX04 (Vapours – 4.5 days) £865

CompEx EX05 - EX06 (Dust – 3 days) £725

Ideally the candidate would complete all the above elements. Without this training, our electricians cannot work on any hazardous area rated equipment. They could however effect an isolation in an emergency situation to „make safe‟ until a suitably qualified engineer arrived. In terms of ongoing maintenance requirements, an estimate of 2 person hours per day (5 days per week) will be used in calculating costs. 3.11.3 Health & Safety risk assessment A risk assessment was produced through adaptation of the generic risk assessment provided by the Environment Agency2 for AD facilities. The key risk elements identified are summarised below:

NOx, local human population, inhalation

Bioaerosols, local human population, inhalation

CO and other gases, local human population, inhalation

Noise and vibration, local human population, air (noise) and ground (vibration)

2 Environment Agency (2013) SR2010No15 Anaerobic digestion facility including use of the resultant biogas. Retrieved from the Environment Agency website: http://www.environment-agency.gov.uk/business/topics/permitting/117255.aspx


Odour, local human population, air

Accidental fire causing pollution to air, water or land, local human population and

environment

Accidental explosion of biogas affecting local population and environment

Arson or vandalism (extremely low risk on BRE site)

Machinery hazard to local human population

Spillage of liquids, effluents etc. affecting local water courses and ground water

It was decided that these risk elements could be minimized and mitigated to extremely low levels through careful siting and design of the plant, adherence with a robust quality and safety management system, regular maintenance, testing and servicing schedules and the incorporation of recommended monitoring equipment (which would also be monitored remotely by Green Gas Technologies via the PLC (Programmable Logic Controller). All these aspects would be detailed and incorporated into a further demonstration phase. 3.12 Competing technologies An assessment of alternative technologies to AD was also undertaken. The results of this assessment are presented here for:

Biomass boilers

Solar thermal panels

Combined heat and power (CHP)

Heat pumps

Landfill gas

Some options can be ruled out in the first instance, these are listed in Table 7.

Table 7 Renewable heat source technologies which have been ruled out in the first instance summary

Technology Reason for omission in the first instance

Solar thermal

A substantial array of solar PV exists already on the BRE site (atop building 14 and building 17 specifically) which rules out an obvious area of installation.

Although BRE currently has a large area of land which could possibly house a solar thermal array, this land is subject to uncertainty with planning permission being sought for this area to build houses.

Solar air heat collectors are predominantly for space heating and would thus need to replace the current building heating system. AD allows for a range of end uses whereas solar air heat collectors cannot do this.

Solar reflectors

Solar power plants require a large number of reflective panels which are angled towards a large tower. This process requires ample space, and desert like conditions of which BRE has neither.

Landfill gas No landfill in close proximity

Therefore, the only options which can be compared in a like with like sense are biomass heating systems, CHP and heat pumps.


3.12.1 Biomass boiler systems BRE produces its own green waste on site, however not a lot of this is wood based, mainly grass cuttings and hedge trimmings. Combined with the fact that food waste cannot be burnt easily this leaves BRE with existing waste costs, whilst also a need to import wood pellets onto site. The closest suppliers of wood pellets are located between 20-40 miles away. The industrial scale biomass boiler on the BRE site would be a significant capital cost, however, the Biomass Energy Centre (2011) indicate that storage and handling costs related to wood burning biomass systems “add significantly” to “complexity and cost”. Therefore the increased costs of handling/storing wood fuel, combined with BRE‟s own waste costs remaining static would see the option of installing a biomass boiler as uncompetitive. Also, the fact that only lower levels of subsidy currently exist for these systems makes them even less competitive regarding cost savings and payback. Biomass boilers are also already commercially available. To date biomass boilers, small and large scale have been tried and tested on a range of applications, thus BRE trialling such systems would be of no use to inform future decisions. 3.12.2 Combined heat and Power CHP plants produce both electricity and heat in a ratio of around 1:1.5 and cost around £1000 per KW. The infrastructure costs required to distribute both heat and electricity to an end use building, combined with the long term increased gas requirement to run the system significantly increases costs. Due to the nature of the BRE site, the heat and electricity would not be used at all times, however CHP efficiencies are lower if the system isn‟t run at 100%, thus this might lead to underperformance and higher costs. BRE would not rule out CHP as source of energy in the future, based upon primary gas consumption, and a larger scale AD scheme would typically consider incorporating CHP to be able to use the biogas irrespective of seasonal variations, i.e. to produce electricity. However, there is not enough biogas predicted to be produced to make this a viable option. 3.12.3 Heat pumps Heat pumps come in two forms, these are ground source and air source. Ground source requires electricity to operate, at a ratio of energy production of around 3:1. The amount of excavation required for ground source systems, either horizontal or vertical, could be problematic on a site with multiple underground services. Air source heat pumps are less efficient in colder weather, which is predominantly when heat is required inside the building, whereas AD biogas production is relatively unaffected by the seasons due to their sealed environment. The lower coefficient of performance (COP) for air source heat pumps leads them to be more inflexible than the AD system proposed.


4.0 Economic / Cost Benefit Analysis This section summarises the cost benefit evaluation for a number of scenarios.

Scenario 1 – BRE only uses putrescible waste generated on site, includes WRAP financial

support.

Scenario 2 – BRE uses putrescible waste from external sources starting in year 2, includes

WRAP financial support.

Scenario 3 – BRE only uses putrescible waste generated on site, does not include WRAP

financial support.

Scenario 4 - BRE uses putrescible waste from external sources starting in year 2, does not

include WRAP financial support.

Table 8 summarises the costs, benefits and expected payback period for each scenario, compared to business as usual.

Table 8 Comparison of costs, benefits and payback periods for different scenarios

Initial costs and ongoing costs and benefits per year Initial costs (one off) Scenario 1 Scenario 2 Scenario 3 Scenario 4

Installation (capital greengas) £127,000.00 £127,000.00 £127,000.00 £127,000.00

BRE commissioning £30,000.00 £30,000.00 £30,000.00 £30,000.00

Site Preparation £10,000.00 £10,000.00 £10,000.00 £10,000.00

Permits/regulatory documents £10,000.00 £10,000.00

Waste containers £3,000.00 £3,000.00 £3,000.00 £3,000.00

Educational materials £3,500.00 £3,500.00 £3,500.00 £3,500.00

ATEX Training £3,000.00 £3,000.00 £3,000.00 £3,000.00

Total £176,500.00 £186,500.00 £176,500 £186,500.00

Ongoing costs year 1 year 3 year 1 year 3

Labour cost /year £5,600.00 £5,941.04 £5,600.00 £5,941.04

Testing Cost /year £1,000.00 £1,060.90 £1,000.00 £1,060.90

Ongoing benefits year 1 year 3 year 1 year 3

RHI payment/ yr £3,216.09 £6,545.65 £3,216.09 £6,545.65

primary gas cost/ kWh £1,542.00 £3,047.00 £1,542.00 £3,047.00

BRE Current Waste Costs £8,300.00 £8,549.00 £8,300.00 £8,549.00

Speculative ongoing benefits year 1 year 3 year 1 year 3

biomass value £318.00 £674.10 £318.00 £674.10

nutrient value £225.20 £475.65 £225.20 £475.65

Total £543.20 £1,149.75 £543.20 £1,149.75

Net ongoing benefit £7,001.29 £12,289.46 £7,001.29 £12,289.46

Contributions (one off)

Greengas contribution £38,000.00 £38,000.00 £38,000.00 £38,000.00

WRAP contribution £83,000.00 £89,750.00 £0.00 £0.00

BRE contribution £55,500.00 £58,750.00 £138,500.00 £148,500.00

Estimated BRE payback period 7 - 8 years 4 - 5 years 16 - 17 years 11 - 12 years


Year 3 was selected for scenarios 2 and 4 as this is when external waste could be added to the existing BRE feedstock, thus increasing the output of biogas, biofuel and biofertiliser. A fuller breakdown of costs and ongoing costs and benefits over a 20 year period can be found in Appendix C. 4.1 Environmental Benefits An environmental cost benefit analysis was not undertaken so it is not possible to provide an estimate of overall environmental benefit over the projected lifetime of a subsequent demonstration phase. However, it would be useful to undertake such an exercise in the future, should the demonstration phase proceed. As with any life cycle assessment, the results are highly dependent upon the boundaries used and the allocation of costs and benefits within, and outside of, the selected boundary. BRE have a great deal of experience in calculating the environment costs and benefits of the built environment and the provision of heating and power to buildings. To do this properly would be a significant project in its own right as BRE consider the following impacts:

Climate change

Water extraction

Minerals extraction

Ozone depletion

Human toxicity

Aquatic toxicity

Terrestrial ecotoxicity

Waste disposal and nuclear waste

Fossil fuel depletion

Eutrophication

Photochemical oxidation

Acid deposition

These can be combined to give a single score, for example CO2 equivalent. To undertake such an assessment, it is likely that the following elements would be relevant:

Manufacture and materials impact of the plant and equipment

End of life issues relating to plant and equipment

Transport of plant and equipment, and the component parts

Site preparation works at BRE

Manufacture, materials, transport and maintenance of pipework and other additional

components required to connect to end use for biogas

Maintenance and operational impacts relating to the system and the production of biofuel

and biofertiliser.

Avoided burdens relating to natural gas displacement

Avoided burdens relating to other fuel displacement (by biofuel)

Avoided burdens relating to fertiliser displacement (by biofertiliser)

Avoided transport impacts for organic waste treated on site (compared to any transport

needed to bring material to the AD system)


5.0 Conclusions It is clear from the feasibility study that micro-level AD is not an easy or quick win. The cost of the plant and equipment compared to the ongoing financial benefits results in a long payback period with several risks to achieving this at any point in the lifetime of the plant. There are a number of variables that would affect this balance in a positive or negative direction. These include cost of alternative waste disposal, cost of fuels being replaced, cost of labour and parts to operate and maintain the system, and renewable energy incentives in place and eligibility criteria. It is also difficult to use the biogas directly throughout the year, unless there is an end use that has a year round gas requirement equal to or greater than the gas produced. This could be exacerbated by the increase in feedstock during the summer months (in relation to green waste), which is when heat requirements are typically at their lowest. Having investigated a number of thermal storage options to balance the heat supply and demand, it seems probable that the only viable route for direct biogas use for heating would be to partially supply the furnace hall at BRE, which has a year round gas requirement greater than any biogas production from the feedstock available. However, even this is not without its issues, as we would need to ensure use of biogas did not compromise the test results of the products being tested in the furnace hall. From a purely technical perspective, the obvious answer would be to significantly increase the size of the plant and import large amounts of feedstock from local surroundings. This would enable the biogas to be used in a combined heat and power boiler, where the primary output would be electricity and the secondary output would be heat. This heat could then be used year round for hot water provision around the site. Aside from the infrastructure requirements to connect multiple buildings to hot water provision, this is not a feasible option for various reasons, including the need to obtain planning and environmental permitting approval, which is unlikely to succeed due to the location of the site within a built up residential area. Also, BRE have little appetite in running a large scale operation of this nature. Therefore, a small-scale plant, despite all the issues that go with it, is the most likely route for any such facility on the BRE site. There is a willingness to work through the difficulties to help build further knowledge in this area and identify improvements that could be made to make installation of such facilities easier and more cost effective in the future. There are various questions that still need to be answered that could be considered in more depth during an actual demonstration project. These include the amount and types of outputs, actual initial and running costs and benefits (compared to predicted), practicalities of using biogas directly, possible combination with other renewable energy sources and thermal storage to manage supply and demand over the year. For the demonstration to proceed, there has to be a reasonable payback period projected for the initial investment; and the running costs would definitely need to be met by savings and revenue. Having done these projections, based upon BRE feedstock only, it was clear that the payback period would be unacceptably long, and may not payback at all if there are minor discrepancies in the assumed costs and benefits. Therefore, funding was sought from WRAP to bring the investment costs down to reasonable levels compared with the likely return on the investment. However, this application for financial support was not successful, so phase 2 demonstration will not proceed in the short term. BRE are keen to work with AD technology providers and other organisations looking to develop small-scale, cost effective and easy to manage systems which could result in a


system being developed on the BRE innovation park at Watford, or at one of the other Innovation Parks we are helping to develop in places such as Beijing, Brasilia, Portland and within the UK. We are also interested in the contribution AD can make to a smart energy mix, which could be feeding a heating network or individual buildings within a development or community. There is also more work that could be done to create thermal storage to optimise the use of renewable energy, including AD, throughout the year and to multiple end user types. It is only by means of a practical demonstration that further cost savings and benefit enhancements could be identified and tried out. Even currently established renewable technologies had initially poor paybacks when they were emerging technologies, but further R&D and refinement of government incentives have enabled these technologies to thrive at a micro level today. BRE were instrumental in this process; for example, in the development of the Micro-generation Certification Scheme. In conclusion, this feasibility study has been useful in developing the decision making factors for locating such a system on the BRE site. These parameters can now be cross referenced to potential systems, and revised as assumptions become more certain, or costs/revenue data changes. It is hoped that at some point in the future the payback will become more favourable and it will be possible to proceed with a demonstration of AD on the BRE site.


Appendix A – Sources of external waste

Sector Organisation

Currently

sort food waste

Waste

Distance from BRE

(miles) Food Waste

produced

Green waste

produced

BRE/Tenants

All tenants utilise BRE's

waste management

system

Yes 480kg p/w 940kg p/w 0

Schools

Coates Way Primary School No 50kg p/w - 1.2

Parmiters Secondary School No 150kg p/w 2 tonnes p/w 1.4

Frances Coombe Academy

Secondary School No 150kg p/w - 1.5

Pubs /

Restaurants

The Swan (Greene King) / Vantage Waste Management

No 50kg p/w - 2

The Gate No 5kg p/w - 1

Pin Wei Restaurant No 60kg p/w - 3

Other

Limestone-landscapes n/a n/a 30 tonnes p/y 0

Simon East Butchers Yes 5kg p/w - 3


Appendix B – Potential locations for AD

system

Locations for a small-scale anaerobic digestion plant Dated 18th June 2013

1 Area 68 2 B 14 visitors‟ car park / Innovation Park 3 North field 4 Exposure site to the North of B 7 5 B 20a & B 20b (Geolabs‟ open storage) (Now ruled out)


1. Area 68

Comments:

Remote location although close to boundary fence and neighbouring properties

Lengthy service runs to utilise product gas

Environmentally sensitive area and habitat for great crested newts


2. Building 14 visitors’ car park / Innovation Park

Comments:

Centrally located, good access for visitors

Highly populated area

Possible gas use for B 17 water heating

The area in the photo is committed to a new build in the near future but there may be a location available on the remaining part of the car park


3. North Field

Comments:

Remote location adjacent to M1 although not viable long-term as the area is to be sold for

redevelopment

Lengthy service runs to utilise product gas

Electricity and water supplies are some distance away


4. Exposure site to the North of B 7

Comments:

Adjacent to year-round gas consumer

Product gas quality might not be suitable for testing

Relatively remote location away from highly populated areas


Appendix C – Cost benefit analysis data

Scenario 1 – BRE only uses putrescible waste generated on site, includes WRAP financial support.

Year 0 Year 1 Year 2 Year 3 Year 4 Year 5 Year 6 Year 7 Year 8 Year 9 Year 10 Year 11 Year 12 Year 13 Year 14 Year 15 Year 16 Year 17 Year 18 Year 19 Year 20

Initial

Installation (capital greengas) -£127,000.00

BRE commissioning -£30,000.00

Site Preparation -£10,000.00

Permits/regulatory documents

Waste containers -£3,000

Educational materials -£3,500

ATEX Training -£3,000

Replacement plant -£5,000 -£20,000

Total -£176,500 £0 £0 £0 £0 £0 £0 £0 £0 -£5,000 £0 £0 £0 £0 £0 £0 £0 £0 £0 £0 -£20,000

Ongoing

Labour cost /year -£5,600 -£5,768 -£5,941 -£6,119 -£6,303 -£6,492 -£6,687 -£6,887 -£7,094 -£7,307 -£7,526 -£7,752 -£7,984 -£8,224 -£8,471 -£8,725 -£8,986 -£9,256 -£9,534 -£9,820

Testing Cost /year -£1,000 -£1,030 -£1,061 -£1,093 -£1,126 -£1,159 -£1,194 -£1,230 -£1,267 -£1,305 -£1,344 -£1,384 -£1,426 -£1,469 -£1,513 -£1,558 -£1,605 -£1,653 -£1,702 -£1,754

RHI payment/ yr £3,216 £3,313 £3,412 £3,514 £3,620 £3,728 £3,840 £3,955 £4,074 £4,196 £4,322 £4,452 £4,585 £4,723 £4,865 £5,011 £5,161 £5,316 £5,475 £5,639

primary gas cost/ kWh £1,542 £1,542 £1,542 £1,542 £1,542 £1,619 £1,619 £1,619 £1,619 £1,619 £1,700 £1,700 £1,700 £1,700 £1,700 £1,785 £1,874 £1,968 £2,066 £2,170

BRE Waste disposal cost savings £8,300 £8,549 £8,805 £9,070 £9,342 £9,622 £9,911 £10,208 £10,514 £10,830 £11,155 £11,489 £11,834 £12,189 £12,554 £12,931 £13,319 £13,719 £14,130 £14,554

Total £0 £6,458 £6,606 £6,757 £6,914 £7,075 £7,318 £7,489 £7,665 £7,847 £8,033 £8,307 £8,505 £8,709 £8,919 £9,136 £9,444 £9,763 £10,094 £10,436 £10,790

Speculative ongoing

biomass value £318 £334 £351 £368 £387 £406 £426 £447 £470 £493 £518 £544 £571 £600 £630 £661 £694 £729 £765 £804

nutrient value £225 £236 £248 £261 £274 £287 £302 £317 £333 £349 £367 £385 £404 £425 £446 £468 £492 £516 £542 £569

Total £0 £543 £570 £599 £629 £660 £693 £728 £764 £803 £843 £885 £929 £976 £1,024 £1,075 £1,129 £1,186 £1,245 £1,307 £1,373

Contributions

Greengas contribution £38,000

WRAP contribution £83,000

BRE contribution -£55,500

Total -£55,500 £7,001 £7,176 £7,356 £7,543 £7,735 £8,011 £8,217 £8,430 £3,649 £8,876 £9,192 £9,434 £9,685 £9,944 £10,212 £10,573 £10,949 £11,339 £11,743 -£7,837

Balance -£55,500 -£48,144 -£40,787 -£33,431 -£25,888 -£18,153 -£10,141 -£1,924 £6,505 £10,155 £19,031 £28,222 £37,657 £47,341 £57,285 £67,497 £78,070 £89,019 £100,358 £112,101 £104,263

ItemTime period


Scenario 2 – BRE uses putrescible waste from external sources starting in year 2, includes WRAP financial support.


Initial

Installation (capital greengas) -£127,000

BRE commissioning -£30,000

Site Preparation -£10,000

Permits/regulatory documents -£10,000




Replacement plant -£5,000.00 -£20,000.00

Total -£186,500 £0.00 £0.00 £0.00 £0.00 £0.00 £0.00 £0.00 £0.00 -£5,000.00 £0.00 £0.00 £0.00 £0.00 £0.00 £0.00 £0.00 £0.00 £0.00 £0.00 -£20,000.00

Ongoing

Labour cost /year -£5,600 -£5,768 -£5,941 -£6,119 -£6,303 -£6,492 -£6,687 -£6,887 -£7,094 -£7,307 -£7,526 -£7,752 -£7,984 -£8,224 -£8,471 -£8,725 -£8,986 -£9,256 -£9,534 -£9,820


RHI payment/ yr £3,216 £6,355 £6,546 £6,742 £6,944 £7,153 £7,367 £7,588 £7,816 £8,050 £8,292 £8,541 £8,797 £9,061 £9,333 £9,613 £9,901 £10,198 £10,504 £10,819



Total £0 £6,458 £11,153 £11,396 £11,647 £11,905 £12,323 £12,596 £12,878 £13,169 £13,468 £13,936 £14,253 £14,580 £14,917 £15,263 £15,788 £16,333 £16,897 £17,481 £18,087

Speculative ongoing

biomass value £318 £642 £674 £708 £743 £780 £819 £860 £903 £949 £996 £1,046 £1,098 £1,153 £1,211 £1,271 £1,335 £1,401 £1,471 £1,545

nutrient value £225 £453 £476 £499 £524 £551 £578 £607 £637 £669 £703 £738 £775 £814 £854 £897 £942 £989 £1,038 £1,090

Total £0 £543 £1,095 £1,150 £1,207 £1,268 £1,331 £1,398 £1,467 £1,541 £1,618 £1,699 £1,784 £1,873 £1,966 £2,065 £2,168 £2,276 £2,390 £2,510 £2,635

Contributions


WRAP contribution £89,750


Total -£58,750 £7,001 £12,248 £12,546 £12,854 £13,172 £13,654 £13,994 £14,346 £9,709 £15,086 £15,635 £16,037 £16,453 £16,883 £17,328 £17,956 £18,609 £19,287 £19,991 £723

Balance -£58,750 -£46,204 -£33,658 -£21,112 -£8,258 £4,914 £18,568 £32,562 £46,907 £56,617 £71,702 £87,337 £103,374 £119,826 £136,709 £154,037 £171,994 £190,603 £209,890 £229,881 £230,603

ItemTime period


Scenario 3 – BRE only uses putrescible waste generated on site, does not include WRAP financial support.


Initial




Permits/regulatory documents





Total -£176,500 £0 £0 £0 £0 £0 £0 £0 £0 -£5,000 £0 £0 £0 £0 £0 £0 £0 £0 £0 £0 -£20,000

Ongoing

Labour cost /year -£5,600 -£5,768 -£5,941 -£6,119 -£6,303 -£6,492 -£6,687 -£6,887 -£7,094 -£7,307 -£7,526 -£7,752 -£7,984 -£8,224 -£8,471 -£8,725 -£8,986 -£9,256 -£9,534 -£9,820


RHI payment/ yr £3,216 £3,313 £3,412 £3,514 £3,620 £3,728 £3,840 £3,955 £4,074 £4,196 £4,322 £4,452 £4,585 £4,723 £4,865 £5,011 £5,161 £5,316 £5,475 £5,639


BRE Waste disposal cost saving £8,300 £8,549 £8,805 £9,070 £9,342 £9,622 £9,911 £10,208 £10,514 £10,830 £11,155 £11,489 £11,834 £12,189 £12,554 £12,931 £13,319 £13,719 £14,130 £14,554

Total £0 £6,458 £6,606 £6,757 £6,914 £7,075 £7,318 £7,489 £7,665 £7,847 £8,033 £8,307 £8,505 £8,709 £8,919 £9,136 £9,444 £9,763 £10,094 £10,436 £10,790

Speculative ongoing

biomass value £318 £334 £351 £368 £387 £406 £426 £447 £470 £493 £518 £544 £571 £600 £630 £661 £694 £729 £765 £804

nutrient value £225 £236 £248 £261 £274 £287 £302 £317 £333 £349 £367 £385 £404 £425 £446 £468 £492 £516 £542 £569

Total £0 £543 £570 £599 £629 £660 £693 £728 £764 £803 £843 £885 £929 £976 £1,024 £1,075 £1,129 £1,186 £1,245 £1,307 £1,373

Contributions


WRAP contribution


Total -£138,500 £7,001 £7,176 £7,356 £7,543 £7,735 £8,011 £8,217 £8,430 £3,649 £8,876 £9,192 £9,434 £9,685 £9,944 £10,212 £10,573 £10,949 £11,339 £11,743 -£7,837

Balance -£138,500 -£131,144 -£123,787 -£116,431 -£108,888 -£101,153 -£93,141 -£84,924 -£76,495 -£72,845 -£63,969 -£54,778 -£45,343 -£35,659 -£25,715 -£15,503 -£4,930 £6,019 £17,358 £29,101 £21,263

Time periodItem


Scenario 4 - BRE uses putrescible waste from external sources starting in year 2, does not include WRAP financial support.


Initial




Permits/regulatory documents -£10,000





Total -£186,500 £0 £0 £0 £0 £0 £0 £0 £0 -£5,000 £0 £0 £0 £0 £0 £0 £0 £0 £0 £0 -£20,000

Ongoing

Labour cost /year -£5,600 -£5,768 -£5,941 -£6,119 -£6,303 -£6,492 -£6,687 -£6,887 -£7,094 -£7,307 -£7,526 -£7,752 -£7,984 -£8,224 -£8,471 -£8,725 -£8,986 -£9,256 -£9,534 -£9,820


RHI payment/ yr £3,216 £6,355 £6,546 £6,742 £6,944 £7,153 £7,367 £7,588 £7,816 £8,050 £8,292 £8,541 £8,797 £9,061 £9,333 £9,613 £9,901 £10,198 £10,504 £10,819



Total £0 £6,458 £11,153 £11,396 £11,647 £11,905 £12,323 £12,596 £12,878 £13,169 £13,468 £13,936 £14,253 £14,580 £14,917 £15,263 £15,788 £16,333 £16,897 £17,481 £18,087

Speculative ongoing

biomass value £318 £642 £674 £708 £743 £780 £819 £860 £903 £949 £996 £1,046 £1,098 £1,153 £1,211 £1,271 £1,335 £1,401 £1,471 £1,545

nutrient value £225 £453 £476 £499 £524 £551 £578 £607 £637 £669 £703 £738 £775 £814 £854 £897 £942 £989 £1,038 £1,090

Total £0 £543 £1,095 £1,150 £1,207 £1,268 £1,331 £1,398 £1,467 £1,541 £1,618 £1,699 £1,784 £1,873 £1,966 £2,065 £2,168 £2,276 £2,390 £2,510 £2,635

Contributions


WRAP contribution


Total -£148,500 £7,001 £12,248 £12,546 £12,854 £13,172 £13,654 £13,994 £14,346 £9,709 £15,086 £15,635 £16,037 £16,453 £16,883 £17,328 £17,956 £18,609 £19,287 £19,991 £723

Balance -£148,500 -£135,954 -£123,408 -£110,862 -£98,008 -£84,836 -£71,182 -£57,188 -£42,843 -£33,133 -£18,048 -£2,413 £13,624 £30,076 £46,959 £64,287 £82,244 £100,853 £120,140 £140,131 £140,853

ItemTime period

www.wrap.org.uk/diad

Feasibility study Micro-scale anaerobic digester - DIAD 2 feasibility study.pdf · 1.1 Feasibility study objectives This report details the results of a feasibility study to install

Documents