1. BSEN40320 – WASTE TO ENERGY PROCESSES AND TECHNOLOGY
Integrated
WasteManagement
Facility for the Greater
Dublin Region
Martin, L. McKeirnan, D. Kumar-Singh, A. Priyadarshan-Kale, A & Hemant-Karmarkar, M.
11/28/2014
The feasibility of developing an integrated waste management facility to cater for the greater Dublin
region was investigated. A suitably-sized site was located with 18km of the city and was designed to
include a landfill, incinerator, anaerobic digester and composting facility. The cost of developing the
site was estimated to be in the region of €157million however the initial investment is expected to
be paid back through the generation of heat and electricity from on-site processes in addition the
economies of scale. Overall such a facility is viewed as a worthwhile investment for the sake of
upgrading Irelands waste management system to a sustainable entity whilst minimizing the
environmental damage associated with waste disposal.

2. 1
Contents
Section 1: Introduction ...........................................................................................................................5
Section 2: Site Selection..........................................................................................................................6
Section 3: Site Layout............................................................................................................................11
..........................................................................................................................................................13
Section 4: Landfill..................................................................................................................................14
Site Infrastructure.............................................................................................................................14
Landfill Design...................................................................................................................................15
Liner Design.......................................................................................................................................15
Leachate............................................................................................................................................16
Gas ....................................................................................................................................................17
Ground Water and Surface Water....................................................................................................18
Section 5: Incineration..........................................................................................................................20
Incinerator types:..............................................................................................................................21
1. Moving Grate: .......................................................................................................................21
2. Rotary Kiln:............................................................................................................................22
3. Fluidised Bed:........................................................................................................................22
State of the art moving grate incinerator:........................................................................................23
Incinerator Efficiency:.......................................................................................................................25
Section 6: Anaerobic Digestion:............................................................................................................27
Importance of AD:.............................................................................................................................28
Feedstock for AD...............................................................................................................................29
Chemical Reactions in AD .................................................................................................................30
Variable Parameters in AD................................................................................................................31
Temperature .................................................................................................................................31
Redox potential.............................................................................................................................31
C:N ratio ........................................................................................................................................31
pH..................................................................................................................................................32
Inhibitory Substances....................................................................................................................32
Types of AD .......................................................................................................................................32
Single stage and Two-stage digesters...........................................................................................32
High Solid or Dry Anaerobic Digestion and Low solid or Wet Anaerobic Digestion .....................33
Planning and Financial viability.....................................................................................................33
Planning Regulations (SEAI: Application guidelines).........................................................................34

3. 2
Section 7: Composting ..........................................................................................................................35
Composting in Ireland.......................................................................................................................35
Site layout .........................................................................................................................................36
Windrow (mechanical aeration) .......................................................................................................36
Type of Wastes Used for the Composting process...........................................................................37
Requirements for Composting :........................................................................................................37
Carbon: Nitrogen ratio..................................................................................................................38
Moisture Content..........................................................................................................................38
Oxygen ..........................................................................................................................................38
pH..................................................................................................................................................38
Temperature .................................................................................................................................39
Particle size ...................................................................................................................................39
Conclusion.........................................................................................................................................39
Advantages of composting................................................................................................................40
Section 8: Discussion and Conclusions..................................................................................................41
References: .......................................................................................................................................42
Appendix 1: Incineration efficiency calculations ..............................................................................47
Appendix 2: Methane production rates from landfill equations......................................................48
Appendix 3: Distribution of workload...............................................................................................49

4. 3
List of figures:
Figure 1:Waste Management Hierarchy (EPA, 2004) 5
Figure 2: Dublin Recycling rates 2000-2010 (Dublin Local Authorities, 2012) 6
Figure 3: Potential locations for waste treatment facility (Google Maps, 2014) 7
Figure 4: The composition of Irish MSW 8
Figure 5: Layout of the various waste treatment technologies and the site in Mayne, Co. Meath 13
Figure 6: Liner System Design showing both soil layer and synthetic layer 15
Figure 7 Vertical gas collection system for proposed landfill 17
Figure 8: Methane emissions and uses from 1990-2008. 18
Figure 9: Waste management strategies of different E.U countries. (Eurostat, 2012) 20
Figure 10: Moving Grate Incinerator (igniss.pl, 2014) 21
Figure 11: Rotary Kiln Incinerator (infohouse, 1996) 22
Figure 12: Fluidized bed incinerator (infohouse, 1996) 22
Figure 13: Typical design of a MSW incinerator (Murdoch University, 2014) 23
Figure 14 Figure1. Anaerobic digestion installed capacity in Europe 27
Figure 15: Complete flow Cycle of AD (Photo Courtesy: Pagels Ponderosa; Utah State University): 29
Figure 16 Figure3. Chemical Reactions in Anaerobic Digestion (www.wastewaterhandbook.com,2014) 31
Figure 17: Lemvig biogas plant overview (Source: www.lemvigbiogas.com) 33
Figure 18: Locations of the composting facilities in Ireland (Herity 2013) 35
Figure 19: Diagram of Windrow (Harvest Quest, 2014) 37
Figure 20: Market for Compost in Ireland. McGovern (2012) 40

5. 4
List of tables:
Table 1: Criteria for site selection (Leão et al, 2004) 10
Table 2: Capital costs of the integrated waste facility 12
Table 3: Products from AD 28
Table 4: Constituents of Biogas (Source: SEAI & Teagsac) 28
Table 5: Potential Feedstock for Electricity Production in Ireland ( teagasc 2013) 30
Table 6: Variable Parameters in AD (Zupan & Grilc, 2007) 32
Table 7: Specification for AD plant in Dublin 34

6. 5
Section 1: Introduction
Traditionally in the times of more relaxed environmental laws, landfilling was the preferred
option of waste disposal which up until recently appeared to be the most economical means
of waste disposal
(Daskalopoulos et al, 1998).
In Europe, this archaic
method of waste disposal is
becoming less and less
favoured due to EU
legislation which insists on
countries diverting their
waste from landfill and
devising more
environmentally responsible
waste management plans. Ireland’s interpretation of which is expressed in the “Waste
Management Act, 1996” and promotes the use of the hierarchy outlined in figure 1.1.
Despite the introduction of this act and a rigorous recycling campaign, the majority of the
country’s waste still ends up in landfill. As trends of rapid economic growth looks set to
continue landfills will reach capacity soon and unless Ireland develops a more sustainable
waste management plan there could be a waste crisis on the country’s hands (Davies, 2004).
According to Stehlik et al (2009) the development of Waste-To-Energy-Centres (WTEC’s)
along with new developments in waste-to-energy processes (WTE), can help rapidly growing
countries reach their waste and emissions reduction targets. Ireland’s susceptibility to
NIMBYism is hindering our capability to deal with waste adequately (Davies, 2004) and
causing the country to fall way behind in meeting emissions reductions in comparison to our
European counterparts such as Denmark (Hjelmar, 1997) and Belgium (Van Gervan, 2005).
There is ample evidence that the combination of waste sorting and recycling, composting,
anaerobic digestion, incineration and finally landfill with biogas recovery is the most
efficient way to treat waste with respect to environmental impact and land use reduction
(Cherubini et al, 2009; Daskalopoulos et al, 1998; Mendes et al, 2004). The aim of this study
is to investigate the feasibility of siting an integrated waste management centre to deal with
the municipal solid waste of the greater Dublin area. This centre will incorporate
Figure 1:Waste Management Hierarchy (EPA, 2004)

7. 6
 an anaerobic digester and a composting system for the treatment of organic
materials,
 an incinerator with energy recovery for the treatment of inorganic materials,
 a landfill with biogas recovery.
Section 2: Site Selection
Dublin is the capital city of Ireland with a population of 1.27 million as of 2014. According to
the central statistics office this is set to increase to somewhere in between 96,000 and
286,000 by 2021. The city produced almost 1.2 million tonnes of municipal solid waste
(MSW) in 2010 with this annual figure expected to rise steadily to 1.4 million tonnes by 2020
(Dublin local Authorities, 2012). According to figure 2 the rigorous recycling campaign
implemented by the Dublin councils appears to be successful with targets being exceeded in
2010.
However the remaining proportion of waste is still being sent to landfill. Setting aside the
emissions from this method of waste disposal for a moment the main issue with this in
Dublin’s case is a spatial one. According to Tammemagi (1998) even countries with
seemingly endless amounts of space cannot afford to waste land on landfills. In Dublin most
of the surrounding area outside the city limits consists of valuable agricultural land.
According to DoELG, (1999) the main aim of the 1996 Act is to reduce the amount of waste.
The development of an integrated waste facility can significantly reduce the amount of
space required to store waste whilst simultaneously using that waste as a resource to
generate energy from biogas or refuse derived fuels. When selecting a site there are a vast
number of criteria which must be satisfied in order to minimise environmental impact and
Figure 2: Dublin Recycling rates 2000-2010 (Dublin Local Authorities, 2012)

8. 7
human health concerns. Figure 3 shows the final sites considered for the waste
management plan.
Figure 3: Potential locations for waste treatment facility (Google Maps, 2014)
The final three sites considered are roughly 20-30 km form the city centre ranging from 27
hectares to 40 hectares in size. Using the following equations, taken from Kiely (1997) along
with population and waste generation estimates from the Dublin local authorities (2012) the
optimum sized site was calculated.
Assuming a required lifespan of 20 years for a projected population of 1.4 million
(CSO,2012) with an average of 3.5 people per household, this gives us a density of 285kg of
waste per household per week with an assumed density of 500 kg/m².
A) 𝐖𝐚𝐬𝐭𝐞 𝐠𝐞𝐧𝐞𝐫𝐚𝐭𝐞𝐝 =
Total population
persons per house
∗
household waste per week
10³
=
1,400,000
3.5
∗
285
103
= 11,400 𝑡𝑜𝑛𝑛𝑒𝑠 𝑝𝑒𝑟 𝑤𝑒𝑒𝑘
= 592,800 𝑡𝑜𝑛𝑛𝑒𝑠 𝑝𝑒𝑟 𝑦𝑒𝑎𝑟
B) 𝟖𝟓% 𝐕𝐨𝐥𝐮𝐦𝐞 𝐫𝐞𝐝𝐮𝐜𝐭𝐢𝐨𝐧 𝐝𝐮𝐞 𝐭𝐨 𝐢𝐧𝐜𝐢𝐧𝐞𝐫𝐚𝐭𝐢𝐨𝐧, 𝐫𝐞𝐜𝐲𝐜𝐥𝐢𝐧𝐠, 𝐛𝐢𝐨 𝐭𝐫𝐞𝐚𝐭𝐦𝐞𝐧𝐭 = 592,800 ∗
.15 = 88,920 tonnes per year
C) 𝐕𝐨𝐥𝐮𝐦𝐞 𝐨𝐟 𝐥𝐚𝐧𝐝𝐟𝐢𝐥𝐥 =
88,920∗103
500kg/m²(density of waste)
=177,840m³ per year
𝐇𝐞𝐢𝐠𝐡𝐭 𝐫𝐞𝐬𝐭𝐫𝐢𝐜𝐭𝐢𝐨𝐧 𝐨𝐟 𝟏𝟐. 𝟓𝐦 =
177,840
12.5
= 14227.2𝑚2
= 1.4ℎ𝑎

9. 8
D) 𝐀𝐫𝐞𝐚 𝐫𝐞𝐪𝐮𝐢𝐫𝐞𝐝 𝐟𝐨𝐫 𝟐𝟎 𝐲𝐞𝐚𝐫𝐬 =
1.4ha ∗ 20(years) ∗ 1.5(extra space for infrastructure) = 42ha
Figure 4: The composition of Irish MSW
Fig. 4 shows the approximate composition of MSW derived from the Dublin Local
Authorities (2012). This is important for determining the size of treatment facilities such as
composting, anaerobic digestion and incineration.
The projections of these equations suggest that for a 20 year lifespan, the ideal size required
would be 42 hectares. At 40hectares, Site A, Mayne is closest to this spatial requirement.
Looking at table 1, this site holds a number of advantages over sites B and C located closest
to the city centre (18km) but furthest from residential areas (>0.5km). In addition, site A is
approximately 2km from the M3 and lies at least 3km from the nearest amenities.
Although the population density of this area is low, there are
likely to be a number of objections to the development of a waste management centre at
this location especially from farmers from the surrounding area, nearby residents,
environmental groups and commercial property owners in the area. The Irish public in
general has a tendency to object to any kind of new development suggested by the
government. Cavazza (2013) suggests that a general lack of public trust in local authorities
hinders the development of any kind of new waste technology. It appears that Ireland’s
history of cloak and dagger politics is severely impeding the upgrading of its waste
management facilities. These concerns could be alleviated by:
Glass(9%)
Metals(8%)
Textiles(2%)
Plastic(11%)
Organic (21%)
Other(17%)
Paper(32%
MSW Compostion in Ireland

10. 9
 Compensating property owners within a defined radius of the facility with heat and
power generated from the on-site facilities.
 Carrying out the development with complete transparency, outlining the overall
benefits of this facility such as emissions reduction, spatial reduction and jobs.
 Encouraging public participation in the planning process. Patel-Tonra (2010),
recommend formally inviting any landowners within 1km of the development to an
information and Q&A seminar whilst posting newspaper adverts to notify any other
interested parties.
 Take measures taken to reduce odour, noise and aesthetic pollution such as
incorporation of a green buffer region and designated slip road from the motorway
for refuse lorries.
The biggest drawback of this site is that it borders a tributary to the River Tolka which feeds
right into Dublin city (biodiversityireland.ie, 2014) however this issue can be addressed by
infrastructural safety measures such as the inclusion of leachate barriers into landfill design.
The fine loamy drift soil-type is composed of a 40:40:20 ration of sand, silt and clay
(Teagasc, 2014). A higher clay composition would be more ideal to assist in the absorption
of odours and leachates thus the landfill design will have to ensure alternative solutions to
these issues.

11. 10
Table 1: Criteria for site selection (Leão et al, 2004)
Site A Site B Site C
Name of
site
Mayne Athgoe Slate Quarries (Rathmore )
Size 40 Hectares 32 Hectares 27.9 Hectares
Cost (Euro) 1.3 Million 1 Million 485,000
Distance
from
Dublin
18km 20km 27.3km
Distance
from Road
Network
2 km from M3 2 km from N7 1.5 km from N81
Residential
Distance
>0.5km <0.4km >0.5km
Slope <5° >20° 5°<x>20°
Soil Type Fine Loamy Drift with Limestone Fine Loamy Drift with Limestone Fine Loamy over Shale/Slate
Current
Land Use
Agricultural Agricultural Agricultural
Distance
from
Amenities
>3km <2km >3km
Water
bodies
Borders tributary to R. Tolka <0.5 km from a drainage ditch <0.5km from a drainage ditch
Links to the
property
http://www.myhome.ie/commercial/brochur
e/mayne-clonee-meath-approx-100-
acres/2488626
http://www.myhome.ie/commercial/brochur
e/athgoe-newcastle-co-dublin-lands-approx-
80-acres-newcastle-dublin-county/2682926
http://www.myhome.ie/commercial/broch
ure/farm-c-69-acres-slate-quarries-
rathmore-naas-kildare/2913312

12. 11
Section 3: Site Layout
Fig. 5 shows a plan view of the chosen site for the proposed waste to energy centre at
Mayne, Co. Meath. An access road of approximately 200m in length will be constructed to
connect the WTEC to the Bracetown business park road which is approximately 500m from
N3 road. At the site entrance a weigh bridge will be constructed to quantify the amount of
waste delivered to the facility. Located immediately after the site entrance are the
administration buildings covering an area of 100m². A permanent roadway will be
constructed to connect the various waste treatment facilities. To the right of the access
road, a sorting centre will be erected. All four municipalities of Dublin are serviced with
separate collections of organic waste (brown bins), recyclables (green bins) and unsorted
refuse (black bins) meaning the majority of waste is pre-sorted upon arrival. Hence this area
need not cover too much area. The anaerobic digester will be located to the north of the
site as indicated in fig.5. In accordance with SEAI guidelines (2008) the digester is at least
250m from any residential accommodation in this location taking up approximately 0.5
hectares. The mass burn incinerator will be located to the south of the site to satisfy DEFRA
(2010) guidelines of siting the facility at least 500m from residential accommodation and
takes up approximately 3ha of site space. This point is the optimum location this site allows
with the nearest residences located >600m away to the East of the site. It is proposed to
build a CHP plant between these two units. Here electricity and heat can be generated and
used for:
 supplying electricity and heat for on-site processes
 supplying electricity and heat to the nearby industrial estates consisting of
Bracetown on the site perimeter and Damastown located 2km to the south east of
the site.
 Exporting remaining power to the national grid.
The landfill will be located in the south east of the site. Even with the mass reduction of
wastes exhibited in the treatment processes, the landfill still requires the most substantial
space. Fig.5 shows a punnet square of intended development over the 25 year lifespan of
the site. This is a worst case scenario as the development would inevitably bring the landfill
closer to residential areas. The optimum scenario is that the land indicated by the shaded

13. 12
area to the south of this site will come available on the market within 5 years of the
commencement of waste management activities; and landfill development will be
concentrated in this direction, maintaining safe distances from residences. The owner of this
property will be more inclined to sell this site considering that its value will depreciate
significantly due to the presence of the waste facility in its vicinity. The composting facility,
consisting of 3 windrows and a grinding unit will be located to the north of the site taking up
0.2ha for recommended windrow width and separation along with the grinding unit area.
This satisfies the minimum distance requirement outlined by Forgie et al, (2004) of 400m
away from residential units. Initial use of the compost generated from this facility will be
applied as fertilizer to the proposed green buffer zone to facilitate growth. It is proposed
that rapid-growing coniferous trees will be planted in the outlined area to obscure the
waste treatment facilities on-site from public view.
Property/Technology Capital Cost (€)
Site 1.3 million
Incinerator 150 million
Anaerobic Digester 4 million
Composting Technology 120,000
Administration buildings 70,000
CHP Plant 350,000
Machinery for site maintenance 400,000
Potential site expansion 750,000
Total building Cost 156,990,000
Table 2: Capital costs of the integrated waste facility

14. 13
Figure 5: Layout of the various waste treatment technologies and the site in Mayne, Co. Meath
Anaerobic Digester
Weigh-bridge
Access Road
Administration
Sorting Centre
CHP Plant Composting Grinder
and Windrows
Incinerator
Proposed Site
Expansion
Landfill
N3
Dublin City Centre 18km
Site Boundary (40ha)
Green Buffer Zone
Damastown Industrial
Estate 2 km

15. 14
Section 4: Landfill
Daire McKiernan
Since July 2009, there has been a significant improvement in the operation of MSW landfill
sites in Ireland (EPA, 2010). This is due to the regulations which have been enforced and
monitored by the EPA. It is imperative that as much biodegradable municipal waste (BMW)
as possible is diverted away from the proposed landfill. Article 5 of the Landfill Directive
requires that Ireland reduces the amount of BMW being landfilled to 0.427 million by 2016.
As landfill has been the cheapest form of waste disposal, it has been the traditional form of
waste management. However, in recent years, there has been an increased shift to
integrated waste management and the sustainable disposal of our waste.
The aim of the EPA, under directives from the European Union, is to reduce the impacts of
and reliance on landfill and to promote an integrated management approach to waste
disposal (Cummins et al, 2002). The landfill is required to operate in accordance with the
Landfill Directive and its main objectives are to prevent or reduce any negative effects on
the environment or human health that are associated with the landfilling of waste (EPA,
2010). Under Statutory Instrument No.194 of the Waste Management (Landfill Levy)
Regulations 2013, landfill costs are set at €75 per tonne of waste.
Site Infrastructure
Site facilities such as weighbridge, office and staff buildings and storage facilities for small
amounts of oils and chemical wastes have been accounted for in a previous section. A
garage or workshop is needed for machinery directly associated with the landfill such as
compactors and excavators. The location of this building can be seen in figure 5. A
permanent internal road which allows access to the landfill can also be seen. Temporary
roads associated with the landfill which lead to the current working cell can be constructed
using debris from nearby construction sites.
The public’s knowledge of the daily activities which take place in the landfill should be kept
to a minimum. This can be carried out by erecting embankments along the perimeter of the
site which act as a green buffer zone. Coniferous trees and shrubs should also be added to
ensure a permanent green buffer zone for screening of the site and control of air pollution

16. 15
also. In the initial phases of the landfill, temporary mobile fences may be necessary to
screen the cells which are being worked on a daily basis.
Landfill Design
The primary goal of the landfill design is to reduce as much as possible the negative effects
the landfill can have on the environment. This is a containment site, where the leachate and
gas are surrounded from the surrounding environment (Kiely, 1997). It is proposed that this
landfill occurs in 6 separate phases. Phasing allows the progressive use of the landfill area in
terms of filling and restoration being carried out at different locations within the site. This is
a ground level landfill and following topsoil removal, waste will be deposited on the surface
up to a height of 12.5m. This type of landfill requires the import of daily and intermediate
covers which can be constructed using up to 1m of compacted soil to prevent
As it is a difficult task to select a location which will have no negative impact or conflicting of
interests, the best compromise location has been selected which minimises the impact on
the environment and the public also.
To ensure minimum pollution and environmental degradation due to the landfill and its
operations, a number of landfill designs should be taken into account. These include liner
design, leachate and gas management and monitoring of the surrounding ground- and
surface water and air quality.
Liner Design
According to Annex I of the Landfill Directive, protection of soil, groundwater and surface
water is to be achieved by the combination of a
geological layer and a bottom liner (EPA, 2010).
Liners are designed to protect the surrounding
water sources by preventing leachate from
seeping out of the contained landfill (EPA, 2000).
To minimize the impact of leachate, a protective
layer called a lining system must be implemented.
As this site has a soil composition ratio of 40:40:20, sand,
silt and clay (Teagasc, 2014), another protective layer must
Figure 6: Liner System Design showing
both soil layer and synthetic layer

17. 16
be added to minimize run off. It is recommended that imported clay of depth 0.5m and
compacted in layers of not more than 20cm should be applied.
The soil should have a very low hydraulic conductivity of <10-9
m/s. Along with this, a
synthetic lining system should be utilized due to the close proximity to the underground
tributary to the Tolka River. The various leachate control methods can be seen in fig.6.
These are usually made out of polyethylene and up to 2.0mm in thickness (Kiely, 1997). A
layer of about 1m of waste should be placed on top of the liner before machinery start to
compact the waste.
Leachate
Leachate is a water-type liquid that is commonly found in landfills that can consist of a
number of chemicals. Leachate generally occurs due to rainfall combined with the moisture
fraction of the waste. As a result, leachate contains organic material and heavy metals and is
toxic to the environment (Kiely, 1997). To collect this leachate, a drainage system must be
constructed which consists of a series of wells and pumps. The leachate is then pumped to
an onsite storage tank where it is treated in an effluent balance tank which has a series of
aerators to agitate the leachate and encourage aerobic conditions. Another method of
reducing the potentially toxic composition of leachate is by recirculating through the landfill
which dilutes the leachate to acceptable levels.
As leachate is produced, it must be collected and removed from the landfill liner. Leachate
collection pipes collect this waste which builds up along the landfill liner. These drainage
pipes then lead to a leachate collection pond where it can be treated by either biological or
physical-chemical methods (EPA, 2000). All active cells should have at least 2 leachate
monitoring points with one located at the leachate collection point.
Monthly, quarterly and annual monitoring of leachate are requirements as part of the
Landfill Directive. Parameters such as leachate level, pH, conductivity, temperature,
ammonia, chloride, BOD/COD, total oxidised nitrogen, total phosphate, metals, sulphates
and fluoride must be monitored at the aforementioned frequencies (EPA, 2010).

18. 17
Gas
Landfill gas is a product of biochemical reactions which occur within the landfill under
anaerobic conditions (Kiely, 1997). The composition of the gas is dependent on a number of
conditions such as the type and age of the waste. Landfill gas can have a calorific value of 15
to 21 MJ/m3
with the gas consisting of up to 60% methane and 39% CO2 (EPA, 1997, 2000)
and is therefore a possible greenhouse gas and environmental risk. In 2009, it accounted for
71% of all complaints in relation to landfill sites.
There are four phases which lead to the production of gas in a landfill:
1. Initial Aerobic Phase – Generally takes days to weeks and O2 is used up as the more
easily degradable organic waste is broken down. This results in elevated
temperature and CO2 production.
2. First Transition Phase – Lasts from weeks to months as anaerobic and acidic
conditions begin to develop due to O2 being completely used up and a drop in pH 6-
4. Hydrogen and CO2 are produced in this stage.
3. Second Transition Phase – This stage takes 3-5 years and involves methanogenic
bacteria activity which convert simple acids like acetic and formic acids to methane
and methanol. Requires a pH 6-7 to effectively work.
4. Methane Phase – A stable process due to all the organic acids being used up by the
methanogenic bacteria.
A gas management system must be put in
place to reduce impact on air quality,
minimise risk of gas migration to other sites,
permit effective control of gas emissions and
if possible to maximise energy recovery. A
landfill gas collection system made up of gas
wells, wellheads and collection pipes can be
used to actively collect and utilise this
resource or to dispose of it through flaring.
Fig.7 shows how gas is collected by means of
vertical gas collection system. This process
can offset some of the costs of control as the gas can be used to make electricity which can
Figure 7 Vertical gas collection system for proposed landfill

19. 18
then be used onsite or sold to local businesses. However, a minimum of 200,000 tonnes of
waste is needed to sustain a commercially viable gas electricity scheme (Department of
Trade and Industry, 1995). As only 88,920 tonnes/year are expected to go to landfill it will
be a number of years before the biogas plant can produce 1MW of electricity. The volume
of gas produced from the landfill has been calculated as 435.76L CH4/kg of wet waste
(Appendix 2).
If the quality of the gas is too low to be collected and used for energy production, it must be
disposed of through flaring. At landfill sites across Ireland this is the most common type of
disposal of landfill gas with all 31 open landfill sites in 2008 utilising flaring (EPA, 2010). Only
20,000 tonnes of methane produced by landfills in 2008 was utilised through energy
recovery with 58,000 tonnes being disposed of through flaring.
Figure 8: Methane emissions and uses from 1990-2008.
Ground Water and Surface Water
The Landfill Directive (EPA, 1999) requires that all ground and surface water be monitored.
Monitoring must be carried out to test the quantity and quality of surface and ground water
on a period basis. This is done to ensure that any impacts the landfill is having on the
environment can be controlled and prevented. Council Directive 80/68/ECC was
implemented through the Waste Management Act of 1996 to prevent pollution of ground
waters and eliminate the effects of the pollution which has already occurred.

20. 19
To assess for risks to groundwater, information regarding water table height, location of
various groundwater features, ground water quality and groundwater vulnerability should
be collected.
Surface water management is essential to reduce the amount of leachate produced and
minimise the transport of chemicals from the landfill. This can be done by designing a
surface water collection system. This collection system allows the collection and
transportation of run off to a settlement pond away from the landfill operations. This is
done by constructing a series of drainage pipe systems (EPA, 2000).

21. 20
Section 5: Incineration
Luke Martin
The incineration of MSW is easily the most controversial waste management process to be
incorporated into the proposed waste to energy centre (WTEC) at Mayne. Much to the
annoyance of the E.U, Ireland has been slow to adapt their waste management strategy to
include modern, environmentally-friendly waste treatment methods (Davies, 2004).
Figure 9: Waste management strategies of different E.U countries. (Eurostat, 2012)
Fig.9 shows Ireland’s favoured waste disposal methods in relation to the rest of Europe.
These figures show the country performs reasonably well in recycling and composting waste
with approximately 49% waste diverted by these methods; however a massive percentage
of Irelands waste is still being disposed of in landfills. The countries which perform best in
minimizing their reliance on landfill, the likes of Denmark, Sweden and the Netherlands,
have all invested in the thermal treatment of their waste. Up until 2011, Ireland has resisted
the use of incinerators largely due to the factors discussed in section 2 such as “NIMBYism”
and lack of trust in planning authorities (Davies, 2004; Cavazza, 2013). The completion of
the Indaver WTEC accounts for the 8% of waste which Ireland treats via incineration in
figure 1. Contrary to public opinion, the health risks associated with incineration are
estimated to be five times lower than those associated with landfill (Moy et al, 2008). In a
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
WasteTreatmentPreferences
E.U Country
Management of MSW in E.U Countries 2012
Landfilled
Recycled/Composted
Incinerated

22. 21
similar study, Cangialosi et al (2008) has claimed that the health impacts which may arise
from inhalation, dermal contact or soil and food ingestion of PCDD’s and PCDF’s emitted
from incinerators are well below the background levels of these carcinogens. In addition,
Sabbas et al (2003) report that incineration can reduce waste to one-tenth its initial volume
meaning less space is required for final disposal. This observed 8% towards incineration is a
step in the right direction for Irelands waste management plan. Another argument
specifically in opposition to incineration is that a move to this technology will discourage the
more environmentally-friendly practice of recycling due to the constant demand of
feedstock’s for these devices (Snary, 2002). However this argument barely holds water
considering 43% of waste in Ireland is going towards landfill despite rigorous recycling
campaigns. There is more than enough feedstock composed of non-recyclable material to
justify the development of an incinerator.
Incinerator types:
There are three main types of incinerators classified by the method used to manoeuvre
waste through the various heating zones.
1. Moving Grate: This involves a system
of moving grates which facilitate the
movement of waste through the
furnace (Fig.10). The waste goes
through three stages of heating. The
drying stage at <100°C (A); the
pyrolysis stage in which waste is
heated in the absence of oxygen at
<700°C (B); and the combustion stage
at 700-1000°C (C). Flue gas is directed
towards a scrubber at 850°C for MSW and 1100°C for hazardous waste to ensure
chemical bonds of harmful molecules are broken (DEFRA, 2010). Air is drawn in from
below for two functions; to induce combustion and to cool the grates. Grates are
arranged at angles to allow waste to proceed through the furnace via gravity.
Bottom ash, recovered at the end of the process is roughly 10% the initial volume of
the waste. According to Nixon et al (2013) this class of incinerator is the most
Figure 10: Moving Grate Incinerator (igniss.pl, 2014)

23. 22
popular in the U.K as most operators identify moving grate as most reliable
technology for heat recovery from waste.
2. Rotary Kiln: This type of
incinerator consists of an
inclined rotating drum
(Fig.11). This is a modular
design type consisting of
two heating zones; a
pyrolysis zone and a
combustion zone. The
action of rotation on an
incline shifts waste slowly
through the pyrolysis chamber,
where solid waste is volatilized into various gases. The combustion chamber
completes the phase change of pyrolysis gases into simpler molecules. This design
type is less expensive to build than moving grate and is suited to small scale,
specilized treatment plants located in close proximity to the sources of waste (Nixon
et al, 2013).
3. Fluidised Bed: This design involves
waste being fed through a waste feeder
and being immersed in violently moving
red-hot sand (fig.12). Waste burns
instantaneously on contact with with the
sand resulting in a high incineration ratio
per unit area. This type of incinerator
cannot support the combustion of non-
uniform sized material meaning pre-
treatment methods such as shredding
are required. These systems are easiest
Figure 11: Rotary Kiln Incinerator (infohouse, 1996)
Figure 12: Fluidized bed incinerator (infohouse, 1996)

24. 23
to operate with lower start-up and stop times however they require upto 50%
higher power demand than moving grate incinerators. According to Nixon et al
(2013) the greatest advantage to these systems is that quantities of bottom are
significantly reduced.
Considering the proposed WTEC is designed to cater for the municipal solid waste from the
greater Dublin area, the moving grate incinerator is deemed as the most appropriate
technology for this facility. With over 250,000 tonnes of waste expected per year at this
facility (Equation 1(B) minus 49% for recycling), efficiency is key. Moving grate incinerators
can accept a continuous flow of non-homogenously sized waste without enlisting in the use
of pre-treatment methods. This limits the likelihood of malfunctions which, in turn boosts
the efficency of collection systems.
State of the art moving grate incinerator:
Fig.13 shows a schematic of the overall layout of the on-site incinerator including
connections to boilers and turbines along with scrubbers to limit the emission of harmful
gases and particulates.
Figure 13: Typical design of a MSW incinerator (Murdoch University, 2014)

25. 24
The system begins with the deposition of municipal solid waste into a storage bunker (a).
Ideally only unsorted refuse waste will be fed into the storage pit. Waste can be further
sorted by a grabber (b), to avoid placing hazardous materials into the hopper(c) or to
retrieve non-ferrous metals. The hopper then gradually releases waste into the moving-
grate incinerator (d). Waste is shifted through the various heating stages outlined in fig.10
(A, B & C) steadily via the moving grates (e). Temperature must be increased gradually to
inhibit the development of cold pockets or gas channelling (DEFRA, 2010). Bottom ash exits
the system via the ash chute (f) and is transported via conveyor belt to a slag removal
system (g), or a magnet to remove any non-ferrous metal residue (not illustrated in this
diagram). Forteza et al (2004) has shown that after a minimum storage time of one month,
the leachates within bottom ash stabilize sufficiently to enable environmentally sound usage
of these residues in road and pavement construction. Flue gases rise through the
combustion chamber (h) at temperatures of 850-1100°C to facilitate the “cracking” of the
strong molecular bonds exhibited in furans and dioxins. The breakdown of these bonds
leads to the creation of another hazardous compound in Nitrous Oxide. Zandaryaa et al,
(2001) recommend the injection of ammonia into the combustion chamber at this stage
which acts as a reagent, reducing the harmful NOᵪ into harmless molecular nitrogen and
water vapour (process known as selective non-catalytic reduction). At least one auxiliary
burner linked to a temperature sensor must be present in this chamber to ensure these
temperatures are maintained throughout the entire process followed by rapid quenching of
the material (DEFRA, 2010). Failure to do so may allow hazardous compounds to reform (de
novo synthesis) in the 400-250°C temperature range.
Flue gases continue out of the after-burn chamber to heat the boiler system (i) which
generates steam to be exported to an on-site turbine. DEFRA (2010) recommends the use of
combination of the following four technologies to maximise energy recovery;
 Boiler system to utilize waste heat,
 Turbines powered by steam from these boiler to generate electricity,
 Combined heat and power (CHP) scheme to utilize exhaust steam,
 Internal heat exchangers for flue reheating.
Suggestions on where to incorporate such features are discussed in section 3 (site
selection). Upon passing the boiler system; flue gases proceed to the economizer (j) where

26. 25
heat is recycled for on-site usage either for supplementary heat supply to the incinerator
itself, or for water and space heating. It is important to locate these heat recovery features
at this point in the cycle, straight after combustion because flue gas temperatures are at
their highest but also require rapid quenching.
After the heat recovery stage, flue gases are now at temperatures of approximately
160°C. It is at this point where the secondary processes associated with gas clean-up begin
in order to ensure minimal harmful emissions to the outside environment. Under E.U
legislation, all modern incinerators must limit their daily average emissions of HCL and TOC
(10mg/m³), HF (1mg/m³), SO₂ (50mg/m³) along with other chemicals such as mercury
(DEFRA, 2010). In order to remove these components safely, gases are first treated in a wet
scrubber (k) which utilizes reagents which target these specific molecules. These scrubbers
also capture fractions of dust simply due to water droplets encapsulating these small
particles. Gas is then further treated in a highly efficient filtration device known as an
electrostatic precipitator (l). This system utilizes an electro-static charge to which designed
to extract the finest portion of particulate matter from the gas. Considering dioxin and furan
pollutants are at the centre of most incinerator objections (Davies, 2004), it is necessary to
include a further, pre-cautionary filtration system in place to prevent their release. Hence
gas passes through a final dioxin filtration system (m) consisting of a catalytic fibre which
oxidises dioxins to form CO², HCL and H₂O (Gore Creative Technologies, 2001). The chimney
stack (n) should be 70m in height for this plant considering 250,000 tonnes of waste are
expected per year (DEFRA (b), 2007).
Incinerator Efficiency:
According to CEWEP (2012), larger incinerators (intake of 250,000 tpa) in northern Europe
tend to have the most favourable R1 value of approximately 0.77. This R1 value is a way of
expressing the energy efficiency relative to conventional power plants hence are suitable for
heat recovery (European Commission Directive, 2008/98/EC). With heat available in the
flue gas in this moving grate incinerator of 8582GJ/day, overall efficiency of this system is
estimated at 80% (Kiely, 1997) [Calculations shown in Appendix 1]. Tolis et al, (2010) has
calculated payback periods of MSW incinerators to be 26-28 years. Gasification yields
greater energy from substrates and has much lower payback periods than mass burn
incineration (8-10 years) so one might argue why invest in incineration? According to

27. 26
Asadullah (2014) these technologies have not yet been successfully up-scaled to deal with
the volumes of waste this site will intake nor are the suited to the heterogeneous sizes for
MSW. Hence the inferior efficiencies of this incinerator is over written by its versatility in
accepting different waste types.

28. 27
Section 6: Anaerobic Digestion:
Anant Kumar Singh
Anaerobic digestion is defined as the controlled breakdown of complex organic matter into
simpler compounds by anaerobic or facultative bacteria in the absence of oxygen.
Anaerobic digestion (AD) is one of the most efficient waste treatment technologies. There is
a recent surge in the installation of AD in Europe due to EU attention towards sustainable
waste management. The technological advancement in better control and optimization of
the anaerobic digestion process is making it financially viable option for waste treatment.
More than 80% composting plants in Netherlands and Belgium will have an anaerobic
digestion facility installed by 2015 as primary treatment.
The economic value associated with syngas makes the AD process more financially feasible
than landfill. The proper waste collection and segregation mechanisms are helping the AD to
run on specific mixture of waste or residue and improving plant operational condition and
reduction of variability. (Baere & Mattheeuws, 2012)
Figure 14 Figure1. Anaerobic digestion installed capacity in Europe

29. 28
Type of product Concentration by mass Uses
Biogas 2-4% For power generation or as cooking gas.
Fiber 7-25% Nutrient rich can be used as soil conditioner
Liquor 75-93% Liquid Fertilizer
Table 3: Products from AD
Component Concentration (by volume)
Methane (CH4) 50-75%
Carbon dioxide (CO2) 25-45%
Water vapor (H2O) 2-7%
Oxygen (O2) <2%
Nitrogen (N2) <2%
Ammonia (NH3) <1%
Hydrogen (H2) <1%
Hydrogen sulphide (H2S) 20-20,000ppm
Table 4: Constituents of Biogas (Source: SEAI & Teagsac)
Importance of AD:
( Baere & Mattheeuws, 2012; Jenkins et al., 2008)
1. It reduces future environmental impacts of waste by degradation into simplest
molecules.
2. AD reduces the spread of harmful diseases and weed seeds.
3. Better control of methane emissions than landfill.
4. Waste water treatment and potential application of liquor in the farm as liquid
fertilizers.
5. To meet the EU environmental regulation and increase of the renewable energy
share.
6. Odour reduction and limited space requirement.

30. 29
7. Better application of nutrient in the soil and reduction of nitrate run-off into water
bodies.
Figure 15: Complete flow Cycle of AD (Photo Courtesy: Pagels Ponderosa; Utah State University):
Feedstock for AD
Waste or agricultural residual having moisture content more than 80% can be used as
feedstock for AD. Any type of easily biodegradable waste like grass, MSW, agricultural waste
from farm can be used as a feedstock.

31. 30
Animals Population Wet tonnes
available
MWh/tonne Potential
Electricity MWh
Cattle 6.4m 32m 0.04 1,280,000
Pigs 1.4m 2.4m 0.024 57,600
Grass 3.4m hectares 204m 0.250 51m
Poultry 13.9m 0.2m 0.180 36,000
Table 5: Potential Feedstock for Electricity Production in Ireland (Teagasc 2013)
Chemical Reactions in AD
A group of bacterium accomplices the task of anaerobic digestion of organic matter in
synergistically.
1. Hydrolysis- The degradation of complex organic matter takes place. Like
Carbohydrates, starch, protein, fats into smaller compounds. It is a rate limiting step if
cellulose is present in higher amount due to slow degradation of cellulose.
Pretreatment of the feedstock is required to improve the hydrolysis.
2. Acidogenesis- These compounds are further broken down into lactic, butyric, propionic,
and valeric acid.
3. Acetogenesis- These short chain molecules are further broken down into produce
carbon dioxide, Hydrogen and acetic acid by fermentation. This can be rate limiting step
if high amount of fat rich substrate is present in the feed.
4. Methanogenesis- This is the last step of biogas production. Different biochemical
pathways used by methanogenic bacteria to produce methane, CO2 and other gases.
Acetotrophic methanogenesis: It uses acetic acid to produce methane. It is the main
producer of methane.
4 CH3COOH 4 CO2 + 4 CH4
Hydrogenotrophic methanogenesis: A small amount of methane is produced by
utilizing CO2 and H2.
CO2 + 4 H2 CH4 + 2 H2O
Methylotrophic methanogenes: It uses methanol to produce methane.
4 CH3OH + 6 H2 3 CH4 + 2 H2O

32. 31
Figure 16 Figure3. Chemical Reactions in Anaerobic Digestion (www.wastewaterhandbook.com,2014)
Variable Parameters in AD
Temperature
Anaerobic digestion works in a variety of temperatures based on the nature of the bacteria.
Generally, physchrophilic bacteria (15-20°C), mesophilic bacteria (25-40°C) and thermophilic
bacteria (50-60°C) are the main types of bacteria identified in anaerobic digester. Higher
temperature increases the rate of digestion. Mesophilic bacteria are used in AD because it
can sustain variation in temperature and require low heat.
Redox potential
Methanogenic bacteria can work at a redox potential of -300mV to -330mV. Low redox
potential is required for the electron transfer in AD.
C:N ratio
For successful AD operation, the C:N ratio should be from 3:1 to 30:1. But, any further
increase in C:N ratio leads to slow growth of bacteria due to absence of nitrogen for the

33. 32
growth. But, a C:N ratio lowers than 3:1, cause ammonia formation which is toxic to bacteria
in high concentration at higher pH.
pH
The AD works in the pH range of 6.5-7.5. A reduction in the pH below 6.5 due to more acid
production has a toxic effect on methnogenic bacteria. The pH reduction below 6.9 is
considered as an indication of pH change and proper treatment and buffering system is
applied. There are two different buffering systems are applied in the AD to maintain the pH.
1. Carbon dioxide – hydrogen carbonate–carbonate buffering system.
2. Ammonia–ammonium buffering system.
Inhibitory Substances
Inorganic salts (like sodium, potassium, calcium, Magnesium), heavy metals (lead, cadmium,
copper, zinc, nickel and chromium) have inhibitory effect on bacteria in high concentration
and simulating effect on low concentrations.
Parameter Hydrolysis/
Acidogenesis
Methanogenesis
Temperature Mesophilic: 25-30°C Mesophilic: 30-40°C
Thermophilic: 50-60°C
pH value 5.2-6.3 6.7-7.5
C:N:P:S ratio 500:15:5:3 600:15:5:3
Trace elements --- Ni, Co, Mo, Se
Table 6: Variable Parameters in AD (Zupan & Grilc, 2007)
Types of Anaerobic Digestion
Single stage and Two-stage digesters
In single phase AD, all the reactions take place in a single compartment. These are simple to
design, build, and operate and less capital expensive. These digesters depend on the ability
of methanogenic organisms to tolerate a decline in pH by the formation of acidic
compounds. More than 80% of the digesters in Europe are based on single stage digesters.
The methanogenesis stage is separated from the initial hydrolysis or acidogenesis stage in
two stage digesters. The production of biogas is higher and better process control. But,
these are capital expensive. (Jenkins et al., 2008; Sinpaisansomboon et al. , 2007; Zupan &
Grilc, 2007)

34. 33
High Solid or Dry Anaerobic Digestion and Low solid or Wet Anaerobic Digestion
The solid content is more than 15% of the total feed and rest is water. The substrate and
biomass are in presoaked solid form. Due to lesser amount of water, the reactor volume is
less and more production of methane. There is reduced inhibitory effect of ammonia in this
process. But, the transportation of substrate is energy intensive process. Low solid digesters
generally have solid content from 5-15%. These are either batch or continuous based on the
plant requirement. (Jenkins et al., 2008; Sinpaisansomboon et al., 2007; Zupan & Grilc,
2007)
Planning and Financial viability
AD is financially viable and great income source if it is managed properly and constructed on
a large scale. As a part of the integrated waste facility, a consistent supply of feedstock is
always available.
Main revenue sources are biogas sale, heat, liquor production and direct electricity sale.
Liquor and fiber is separated in separator and liquor goes to heat exchanger to preheat the
cold incoming slurry. Around 20-30% heat generated by the digester is used in the anaerobic
digestion process.
Figure 17: Lemvig biogas plant overview (Source: www.lemvigbiogas.com)

35. 34
Specification Proposed plant for Dublin City Lemvig Plant (Case study)
Land Area 1 hectare >1 hectares
Installed biogas capacity 7100m3
14300m3
Input substrate Around 300t/day≈109500 t/yr
20% industrial waste + 20-30%
MSW from home + 50% Slurry
Around 615 ton/day (83%
manure and 17% organic
waste)
Conditions Thermophilic Thermophilic
Installed Power 1.5MW 3MW
Investment 4m (1-2m subsidies from EU) 10.2m (1.2m subsidies from EU
& cost included land)
Positive factors Free heat to public Cheaper biogas rates and heat-
good public perception
Operating cost 40,000 40,000-50,000
Payback period 5-6 years 4 years
Table 7: Specification for AD plant in Dublin
Planning Regulations (SEAI: Application guidelines)
1. All waste storage and treatment must not be within 10m of any watercourse or
250m from any spring well or borehole.
2. Biogas must be burnt in an appliance with a net rated thermal input of less than
3MW.
3. Permitted waste types comprise sludges, plant tissue waste and manure from
agriculture, horticulture, forestry and fishing and some wastes from the dairy
products industry.
4. A Standard Rules Environmental Permit for off-farm anaerobic digestion is that the
distance to any off site building used by the public must be 250m or greater.

36. 35
Section 7: Composting
Aneesh Priyadarshan Kale and Mugdha Hemant Karmarkar
Composting is the natural degradation of organic material by micro-organisms and its
conversion into a stable earth like material called humus. This process is accomplished in an
aerobic environment. This material can be used in soil so as to increase it’s the overall
fertility (Curran, 2014). The micro-organisms break down the raw organic matter and get
energy which is used up by them for the process of reproduction. (Composting Council of
Canada, 2014)
The decomposed matter that is left consists of dead and living micro-organisms along with
non-degraded organic matter is called as "Compost".
Composting in Ireland
As seen there are lists of composting facilities in the country. In Ireland, mostly windrows
are used for composting technology followed by in-flow and aerated systems. This is
because windrows require low maintenance costs, low initial costs (Herity, 2003).
Figure 18: Locations of the composting facilities in Ireland (Herity 2013)

37. 36
Site layout
There would be a network of roads connecting the rest of the facility as well as small roads in
between the composting unit for movement of machinery and vehicles to carry the compost.
There is a grinder located next to the composting unit to reduce waste particles to the
required size. For the waste facility windrow composting is been proposed.
Windrow (mechanical aeration)
Windrows are basically long rows of piles of organic waste. These are turned frequently either
manually or mechanically over a period of time so to facilitate movement of air (EPA, 2014).
The site is to have a pair of windrows. Preferably the piles are around 1 to 3 meters tall .The
width would be around 2-5m. It is kept in such a way that there is enough air flow in it so as
to maintain the temperature. There are a number of machines that are used to mix the waste
such as front end loaders (EPA, 2014).
A series of pipes are to be installed below the composting unit so as to catch the leachate,
which can be treated in a small unit next to the composting site. This will help to nullify any
soil or ground water pollution from happening. There can also be presence of detachable
rooftop, to offer protection from rain and control the temperature. Turning at frequent
intervals maintains temperatures.
Windrow composting tends to have many benefits over other conventional methods. Since
there is frequent turning there is good amount of air exchange that takes place. It also helps
to maintain the desired temperature range. Constant and hard-core mixing helps grinding the
particles to as small as possible thus increasing microbial activity and at the same time
reducing the time.

38. 37
Figure 19: Diagram of Windrow (Harvest Quest, 2014)
Type of Wastes Used for the Composting process
Most of the wastes used for the composting process, are biodegradable garden and park
wastes, food and kitchen wastes from kitchens, restaurants, fast food joints, caterers, wastes
from food processing plants. (Curran 2014)
According to ABP 2002 regulations, Category 2 and 3 could be used for composting. Under
category 2, manure and gut contents can be used directly in a compost plant. In Category 3,
food of animal origin, catering waste is suitable for composting. (Curran 2014)
Category 3 before submitting to a compost plant, it should be ssubjected to a treatment
(Curran, 2014)
It is a highly popular technique as it yields high quality product at the same time it requires
less investment as well. The space available in the proposed facility is sufficient enough to
have an installation of two windrows.
As the final product is of good standard, it can be sold off as high quality compost.
Requirements for Composting :
The process of composting is carried by diverse population of micro-organisms. To make the
process more effective, the system should be managed properly by supplying a sufficient
proportion of the parameters required by the micro-organisms (Curran, 2014).

39. 38
Carbon: Nitrogen ratio
Main nutrients required for the composting process is Carbon and Nitrogen. Proper
amounts of carbon and nitrogen will help in carrying out the process effectively (Hattemer &
Stettler,2000).
If the carbon levels are high and decrease in the nitrogen level, the microbial activity will
slow down, since, nitrogen is required to break the carbon sources. This will have an adverse
effect on the process. If the carbon is less and more amount of nitrogen, excess of carbon
will be broken down and nitrogen will be easily lost in the atmospheres in the form of
ammonia gas. Thus, the process will be affected in a negative way on the environment
resulting in bad composting process. The optimum range of C:N will be 25:1 to 35:1(Earth
easy, 2014). When the ratio decreases to 12-20:1, this means that the process is finished
(Hattmar & Stettler, 2000).
Moisture Content
With the help of moisture, the micro-organisms move and transport materials. It is also
essential for all the chemical reactions taking place during the process.
The optimum moisture content range should be 50-60%. (Curran, 2014). If the moisture
content exceeds 60%, the microbes will not thrive. Also, if the content reduces below 15 %,
the microbial activity will stop. (Hattemer & Stettler,2000)
Oxygen
Lack of oxygen can result in anaerobic decomposition which will lead to inefficient compost
and undesirable odours. It should be well supplied to the entire pile. The concentration of
oxygen required is minimum 5% (Curran, 2014). Despite of the aeration, the amount of air
do not reflect the amount of oxygen reaching the microorganism. This is because, most of
the micro-organisms require aqueous environment for them to sustain (Hattemer &
Stettler, 2000).
pH
The ideal pH range for the microbial activity is between 6.5 to 8.0 (Hattemer & Stettler,
2000) Acidic pH has a negative effect on the compost. Bacterial growth is significant in such
conditions, thus, slowing down the process (Composting Council of Canada, 2014). pH
should be considered when some materials are rich in nitrogen. This material will increase

40. 39
the alkalinity of the compost forming ammonia. This ammonia results in the loss of nitrogen
through volatilization. This affects the environment in a negative way (Hattemer & Stettler,
2000).
Temperature
During the process wherein the micro-organisms break down the materials there is release
of heat in the compost. This increases the temperature. It indicates that the process is
taking place in a proper manner (Composting Council of Canada, 2014). On the other hand,
if the temperature fails to increase, this indicates insufficient amount of nitrogen and
moisture content. Temperature is to be maintained around 40-60 degree Celsius (Friesen,
2002).
Particle size
Different materials used in the compost, have different particle size. The maximum size of
the particles should be 12mm.Good particle size leads to good air flow, (Earth Easy, 2014).
Conclusions
In 1998, the Irish Government policy of waste management aimed to reduce the amount of
biodegradable waste dumped in landfills over a period of 15 years. These targets included
50% diversion of the house hold waste to landfills(Citizen Information Board, 2010). Thus a
composting unit will not only serve the purpose, but also the compost that is obtained be
sold in the Irish market. According to McGovern (2012), the price of compost directly from
the site can fetch anywhere between 10-40Euros per m3 of compost. If this is to be further
treated and bagged the price of compost is seen to go high as 180 Euros.
According to McGovern (2012) the main markets for compost are highlighted in the figure
below.

41. 40
Figure 20: Market for Compost in Ireland. McGovern (2012)
Since there is a potential market that is available for the compost, it can serve as a source of
revenue for the waste facility.
Advantages of composting
According to U.S Environmental Protection Agency, (2014) composting has many benefits.
 Good quality of compost tends to improve soil quality.
 It thus helps reduce dependency of chemical fertilizers on agricultural land by
improving crop yield.
 Compost has also been known in helping pest and plant diseases.
 The compost process tends to absorb odour and treat semi volatile and volatile
 The trend of composting tends to move away waste from landfills and incinerators,
thus reducing the stress on them as well as bring down the pollution levels
associated with them.
 The compost obtained when spread on soil tends to arrest soil erosion.
 Use of compost means use of less water, fertilizers and pesticides. It is an economic
commodity and a low cost option to landfill and other methods.

42. 41
Section 8: Discussion and Conclusions
Overall the task of siting an integrated waste management facility within a reasonable
distance of Dublin is feasible. The city provides a more than adequate feedstock to justify
the construction of these technologies. Despite exorbitant initial capital costs in the region
of 157 million the project is entirely worth undertaking due to the following reasons:
 The majority of on-site processes have payback periods within the 25 year lifespan of
the site due to power generation (incinerator and AD) as well as commercial
ventures (composting, ash for road construction).
 These processes reduce the environmental impact of waste disposal considerably by
converting waste in controlled environments, capturing harmful emissions before
they reach the outside environment thus limiting the emission of GHG’s and other
harmful chemicals.
 Incineration and AD can generate power, offsetting fossil fuel use by supplying up to
25,000 homes with electricity whilst simultaneously providing the site with power
and heat. Nearby industrial estates could avail of this power also.
 These processes can enable the recycling of post-treatment residues such as non-
ferrous metals from incineration, pathogen-free compost and raw materials which
can subjected to the Fischer-Tropsch cycle to make synthetic fuels.
 These processes divert a massive amount of waste from landfill; In the case of
incineration, 80-90% of the initial volume of the waste can be diverted hence less
space is required for the landfill.
 Economies of scale; by integrating all these process on one site, many savings can be
made from on-site vehicles and by building just one large CHP plant as opposed to a
few on a number of sites.
 In addition, transport costs and emissions can be reduced by eliminating residue
transport to distant sites. Further transport costs can be made by the fact that
Ireland would no longer have to export waste to Germany and other countries in
Europe to be disposed of appropriately.

43. 42
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48. 47
Appendix 1: Incineration efficiency calculations
R1 formula for Efficiency of MSW incinerator in relation to conventional power plants (European
Commission Directive, 2008/98/EC) :
𝐸𝑛𝑒𝑟𝑔𝑦 𝑒𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦 =
𝐸𝑝 − 𝐸𝑓 + 𝐸𝑖
0.97 ∗ (𝐸𝑤 + 𝐸𝑓)
Where : Ep is annual energy produced as heat/electricity
Ef is the annual energy input to the system via fuels for production of steam.
Ew is annual energy contained in waste by Net calorific value (GJ/year)
Ei is annual energy imported excluding Ew and Ef (GJ/reay)
0.97 is a factor accounting for bottom ash+ radiation energy losses
Mass/Balance calculations for incineration (Kiely, 1997):
Assumptions:
MSW: 685,000kg/day of MSW; 374,010 combustible(54.6%); 164,400 non-combustible(24%);
146,590 water(21.4%)
Heating Value: 11,780 kJ/kg
5% unburned Carbon in residue with LHV of: 32,564
Total losses of heat (excluding C in residue): 1.66x10⁸kJ/day
Boiler efficiency: 85%
Calculations:
Gross heat input = (685,000kg/day) x (11780kJ/kg)= 8.7x10⁹ kJ/day
Heat loss due to unburned C = 164,400kg/0.95 = 173,053 kg/day
Unburned C in residue = 173,058kg/day x (0.05) = 8652.65 kg/day
Heat Loss in unburned C = (8653kg/day) x (32,564 KJ/kg) = 281,776,292 kJ/day
Heat available in flue gas = Gross heat input – (losses due to unburned C + total losses of heat) =
(8.7x10⁹ kJ/day – (281,776,292 + 1.66x10⁸) = 8252GJ/day
Combustion efficiency = Net available heat/Gross heat input x 100 =
8,252,223,708/8.7x10⁹ x 100 = 94.85%
Overall efficiency = (0.9485) x (0.85) = 80%

49. 48
Appendix 2: Methane production rates from landfill equations
Methane production rate of landfill without sulphur but including water is (C70H150O70N) (Adapted
from Kiely (1997)).
Assumptions
CHON is 30% of the wet weight of waste going to landfill.
a = 150 (number of atoms in hydrogen molecule)
b = 70 (number of atoms in oxygen molecule)
c = 1 (number of molecules in nitrogen molecule)
d = 4n + a – 2b – 3c 𝑑 = (4 𝑥 70) + 150 − (2𝑥70) − (3𝑥1) = 287
e = 0.96 (fraction of waste converted to biomass)
n = 70 (number of atoms in carbon molecule)
Solution:
𝑉𝑜𝑙𝑢𝑚𝑒 (𝐿)𝑜𝑓 𝐶𝐻4/𝑘𝑔 𝑤𝑎𝑠𝑡𝑒 =
(
𝑑𝑒
8
) 𝑉𝑜𝑙𝑢𝑚𝑒 𝑆𝑇𝑃
𝑚𝑜𝑙𝑒𝑐𝑢𝑙𝑎𝑟 𝑤𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑤𝑎𝑠𝑡𝑒/𝐶𝐻𝑂𝑁
𝑀𝑜𝑙𝑒𝑐𝑢𝑙𝑎𝑟 𝑊𝑒𝑖𝑔ℎ𝑡 = (70𝑥12) + (150𝑥1) + (70𝑥16) + (1𝑥14) = 2124𝑔/𝑚𝑜𝑙𝑒
𝑀𝑜𝑙𝑒𝑠 𝑜𝑓 𝐶𝐻4 𝑝𝑒𝑟 𝑚𝑜𝑙𝑒 𝑜𝑓 𝑤𝑎𝑠𝑡𝑒 =
𝑑𝑒
8
=
287𝑥0.96
8
= 34.5
𝑉𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑚𝑒𝑡ℎ𝑎𝑛𝑒 𝑝𝑒𝑟 𝑢𝑛𝑖𝑡 𝑤𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑤𝑎𝑠𝑡𝑒 (
𝐿
𝑘𝑔
) =
34.5𝑥88920
2124/0.3
= 435.76𝐿 𝐶𝐻4/𝑘𝑔 𝑜𝑓 𝑤𝑒𝑡 𝑤𝑎𝑠𝑡𝑒

50. 49
Appendix 3: Distribution of workload
Abstract, table of contents, introduction, site selection, incineration, conclusions and reference list –
Luke Martin.
Table of figures/tables, Site Layout, Site Map, landfill and proof-reading – Daire McKeirnan.
Site Layout and Anaerobic Digestion – Anant Kumar Singh
Composting – Aneesh Priyadarshan Kale
Composting - Mugdha Hemant Karmarkar