Annex 6 - Waste
1. Introduction
1.1.Purpose of this Document
This document is an Annex to the “Guidance document on national nitrogen budgets” (UNECE 2013),
which outlines how to construct a national nitrogen budget. In the guidance document, eight pools
are identified which are: 1) Energy and fuels, 2) Material and products in industry, 3) Humans and
settlements, 4) Agriculture, 5) Forest and semi-natural vegetation including soils, 6) Waste, 7)
Atmosphere, and 8) Hydrosphere. This document specifically addresses the development of a
Nitrogen budget for waste systems (household waste, sewage etc).
The document will provide an overview of the ‘Waste’ pool and sub-pools within it, including the
nitrogen species which are involved, their transformation or transport to other pools within the
system. It will also provide information on how to find data and to construct the ‘Waste’ pool of a
national nitrogen budget.
1.2. Amounts to be expected
Although the absolute value of flows within each nitrogen budget will differ, the work of Leip et al.
(ENA ref) can provide us with an indication of the potential relative importance of flows within the
‘Waste’ pool, which may be of help when starting to construct a national nitrogen budget. Leip et al.
brought together national nitrogen budget data for a selection of European countries and also
constructed a European level nitrogen budget, which although incomplete is a starting point for
comparison when conducting national level nitrogen budgets. The pools within the Leip et al. budget
which correspond to the ‘Waste’ pool (which is the subject of this annex), are the ‘Solid Waste’ and
‘Sewage’ pools.
Looking at the inflows in relation to these pools in the Leip et al. budget, the largest overall
contributor is the ‘Consumer’, from which 59% (3.1 MtN/yr) of the N flows are from ‘Sewage’ and
36% (1.9MtN/yr) are from ‘Solid Waste’ respectively, with the final roughly 5% (0.24 MtN/yr) from
the Industrial sector in the form of ‘Sewage’. This makes a total inflow of N to the ‘Waste’ pool of
5.24mt N/yr, however, the outflows from the ‘Sewage’ and ‘Solid Waste’ system add up to only
2.67MtN/yr, which suggests an accumulation of N in the system of around 50% per year. It is
possible that due to the lack of information available, the Leip et al. study underestimates the
outflow from the ‘Waste’ pool, however it is to be expected that there is an increase in the total N
which is stored in this pool (stock N), trapped in landfill, but little data exists on what this might be in
either relative or absolute terms . Coming back to the Leip et al. study, in relative terms however,
the main outflows are from wastewater to surface water, 68% (1.8MtN/yr), denitrification of sewage
to N2 of 30% (0.8MtN/yr). Further flows are significantly smaller then, with around 1.7%
(0.045MtN/yr) of the nitrogen being passed to the ‘Agriculture’ pool as sewage sludge for fertilising
fields and finally the smallest fractions are the release of N2O to the atmosphere during sewage
processing (0.3%, 0.0079MtN/yr), and roughly equal releases of N2O and NH3 from solid waste
processing of 0.19% (0.005 MtN/yr) and 1.7% (0.0044 MtN/yr) respectively.
2. Definition
2.1. Activities and Flows encompassed by the pool
The main in-flows come from both domestic and industrial situations, and although agriculture can
be considered as a type of industry, as with the overall pools, agriculture is described separately
here for clarity (e.g. flows of manure into the solid waste system which are N rich) and also flow back
to the agricultural (and other systems) of treated sewage sludge (again N rich).
The waste pool flows include N2O, NOx, NH3 and Nitrate and also ultimate de-nitrification to N2.
There are close links between the pool ‘Waste’ and the ‘Human and settlements’ and ‘Materials and
products in industry’, as this is the point at which products are discarded and therefore become
waste. There is a close connection with the ‘Atmosphere’ pool also, through the emissions and
denitrification from wastewater treatment and solid waste disposal processes and also the
hydrosphere. Figure 1 outlines the major flows between ‘Waste’ and the further seven pools, there
may also be export and import of waste products to the ‘rest of world’ i.e. outside the boundaries of
the national budget.
Energy and Fuels
Agriculture
Compost from
digestion use on
soils
Solid agricultural
waste, such as
un-used slurries
and manure,
animal carcasses
not for
consumption**
Humans
and
settlements
Sewage Sludge
use on soils
Exported
waste
Atmosphere
Wastewater
treatment
Wastewater
/sewage
Compost from
digestion use on
soils
Forests and
semi-natural
vegetation
Imported
waste
Waste to energy
operations
(biogas/anaerobic
digestion, incineration),
including from import
Solid waste
(including
food)*
Sewage Sludge
use on nonagricultural soils
*Industry and agricultural
based food waste and human
sewage also included here
Solid waste
treatment
Solid Waste
Untreated
wastewater run-off
and leachate from
solid waste
Wastewater
and sewage
Solid waste
(NOT
including
food)
Hydrosphere
Waste recycling, e.g.
Glass, plastics.***
Material and products
in industry
** Not including food
waste related to the
farm workers on site
** *Recycling of
glass etc from
industrial sites, for
use within industry,
remains an internal
cycle in industry
pool
Figure 1: Flows connecting the ‘Waste’ pool, with the other seven pools.
2.2. Overall approach and main sub-pools
The main considerations with respect to waste and Nitrogen flows, is to consider where this material
is generated (in which pools is material no longer needed and discarded as waste), what types of
material these are and then how this is managed (collection and processing). This can then be linked
to the N flows passed on, or emitted/transformed at each stage. There are also considerations
regarding the boundaries of the ‘Waste’ pool in relation to the other pools, such as ‘Products and
materials in industry’ and ‘agriculture’.
Waste is generated at any sites where humans live or work, therefore at the following sites (this is
an indicative not an exhaustive list):
a) Households
b) Offices
c) Shops
d) Markets
e) Restaurants
f) Public institutions
g) Industrial installations
h) Water works and sewage facilities
i) Construction and demolition sites
j) Agricultural activities
There are two main ‘sub-pools’ considered within this annex, ‘solid waste’ (any item discarded at
domestic or industrial sites) and ‘wastewater and sewage’ (domestic and industrial site drainage,
including wastewater and sludge from industrial applications). The ‘Solid waste’ can be further
divided by processing method:
 Solid waste disposal on land
 Biological and other treatments
 Incineration and open burning of waste
There is one other pathway for an item which has been discarded, which is recycling. Firstly we
should clarify that for the purposes of this annex (in line with IPCC guidance, ref), we refer to
recycling ONLY as the re-use of materials such as glass, plastic etc, and NOT to waste-to-energy
schemes (such as anaerobic digestion, leading to biogas generation). In the case of waste-to-energy
schemes, the emissions related to this are ascribed to the ‘energy and fuels’ pool. In the case of
recycling of materials, such as glass, plastics etc, this constitutes an outflow to the ‘materials and
products from industry’ as these items will be re-used to make further goods for consumers. The
emissions associated with recycling these products are therefore assigned to the ‘materials and
products in industry’ pool.
In flows to the ‘waste’ pool as a whole come from three main other pools ‘agriculture’, ‘materials
and products in industry’ and ‘humans and settlements’ in the form of both ‘solid waste’ and
‘sewage and wastewater’ from each pool.
The methods of processing and disposal then discern which pool the ‘outflow’ will enter. Solid waste
disposal on land gives rise to certain emissions, depending on the method used and the pool itself
should increase in size (i.e. there should be a positive stock change) in N in this sub-pool over time
(unless there are significant landfill recovery schemes in operation, which would then release more
of the stored N). Biological and other treatments, such as composting, will both emit nitrogen to the
‘Atmosphere’ pool, and pass N flows to possibly both ‘Agriculture’ and ‘Forests and semi-natural
ecosystems’ in the form of compost or digestate, and in the case of biogas generation, the waste
flow is accounted for in the ‘energy and fuels’ pool. Likewise in the case of incineration and burning
of waste, if this is done to generate energy, then the flow passes to the ‘energy and fuels’ pool, the
two products of incineration are the gases emitted and the ash left behind, which is sent to landfill.
Most of the N stored in the waste is converted to gases and emitted to the ‘atmosphere’ pool. An
overview of the sub-pools and processing methods can be seen in Figure 2, along with an indication
(dotted line) of the boundary of the ‘waste’ pool and inflows and outflows in relation to it. It is also
worth mentioning that in two cases, part or all of waste related materials are assumed to be re-used
within other pools and therefore does not enter the ‘waste’ pool. This is in the case of part of the
manure and slurry produced in the ‘agriculture’ pool, (see agricultural activities Figure 2), which is
re-used at farm level – the emissions related to this are accounted for in the ‘agriculture’ pool. The
second case is for materials from within the ‘materials and products in industry’ which are discarded
(i.e. waste), but re-cycled and re-used to make further products. The suggestion is that these flows
of N and emissions related to the re-cycling process are internal to ‘Materials and Products within
Industry’.
Manure and
slurry
Burni
agri
waste
28-7-14
Agricultural
Activities
sewage
Solid waste
disposal
Solid
Waste
Handling
Industrial and domestic
waste (including food)
Managed waste
disposal sites
[aerobic OR nonaerobic]
4A
Industrial and domestic
waste (including food), non
food carcasses and manure
and slurry
2
NO3-
NOx
N2O
Sewage sludge
Applying
digestate to
land
sewage
Recycled products (waste
including food) [to fuel or
industry]
4B
Biological
treatment
of solid
waste
N2O
NOx
Biogas
generation
(anaerobic
digestion)
Waste to
energy (from
incineration)
4D
Recycling
Industrial
activities
Composting
digestate
NH3
sewage
Uncategorised
waste disposal sites
3
Sewage
sludge non
agricultural
soils
Domestic
activities
1
Unmanaged waste
disposal sites
N2
Sewage and
wastewater
handling
Domestic
4C
1
Incineration
and open
burning of
waste
Industrial
2
NOx
N2O
NH3
NO3-
Ash
NOx
N2O
Waste incineration
and open burning
of waste
1
Open burning of
waste
2
Figure 2: Schematic of the waste pool. Note this is a work in progress and is more part of the
development process than the final diagram for users. Also please assume that where NOx, NH3, N2O
and N2 are shown, this implies an outflow to atmosphere and for nitrate a flow to the hydrosphere.
Dotted lines indicate flow to another pool.
2.3. Nitrogen Species
Several nitrogen species are transported and transformed within this pool.
Nitrogen
species
N polymers
Molecular
Formula
N content
[% m/m]
Aggregate
state
Occurrence
See Table 14, Error! Reference source not found.,
Error! Reference source not found. (in HS).
polymer of
amino acids
Proteins
(nutrition)
16
NO3-
Nitrate
NH4+
Ammonium
solid/liquid
feed/food
23
78
Inflow
Waste non-food
products
Wasted
agricultural
products/food
products
food/
private
gardening/wast
ewater
dissolved
(ionic)
drinking
water/food/
fertilizer
NOx
Nitrogen
oxide1
Urea
gaseous
burning
processes
47
dissolved
(ionic)
excrements
0.1-0.3
solid
forest
products
40
CH4N2O
N in wood
Ammonia
NH3
gaseous
Nitrous Oxide
N2O
Gaseous
Denitrification
N content calculated based on NO2:NO as a ratio of 1:1
Emissions to
atmosphere
, from
storage
and/or
disposal
Emissions to
atmosphere
, from
storage
and/or
disposal
To surface
and
groundwate
rs, either
post
wastewater
treatment
OR leakage
from solid
waste
disposal
Emissions to
atmosphere
related to
storage
and/or
disposal
wastewater
Volatilization
from organic
and synthetic
fertilisers
1
Outflow
non-food
products
-
-
residual
materials
Emissions to
atmosphere
from
wastewater
treatment
and
biological
treatment
of solid
waste
Emitted
during the
treatment
and or
disposal of
wastewater
and solid
wastes
3. Internal Structure
The ‘waste’ pool has two sub-pools which are linked to other pools, by outflows and inflows.
Energy and Fuels
Agriculture
B
D
P
P Imported
waste
O
A
Atmosphere
C
N
Solid Waste
Humans
and
settlements
E
R
Q
Wastewater
and sewage
F
G
L
Hydrosphere
H
Forests and
semi-natural
vegetation
M
K
I
J
Material and products
in industry
A Waste to energy
operations
(biogas/anaerobic
digestion, incineration),
including from import
B Compost from
digestion use on
soils
C Sewage Sludge
use on soils
D Solid agricultural waste,
such as un-used slurries and
manure, animal carcasses not
for consumption**
E
Wastewater
/sewage
F
Solid waste
(including
food)*
G Compost from
digestion use on
soils
H Sewage Sludge
use on nonagricultural soils
I Solid waste
(NOT
including
food)
M
Wastewater
treatment
J
Wastewater/
sewage
K Waste recycling, e.g.
Glass, plastics.***
L Untreated
wastewater
run-off
N Solid
waste
treatment
O Exported
waste
P Imported
waste
Q Leachate
from landfill
R household waste
seperated from
sewage
Figure 3: Schematic of the relationship between the pools and sub-pools within the ‘waste’ pool.
Note: The boxes are included at the moment just for information – needs tidying up/putting
elsewhere.
3.1. Sub-pool Solid Waste Disposal
3.1.1. Solid waste disposal on land
3.1.2. Biological and other treatments
3.1.3. Incineration and open burning of waste
3.1.4. Stock and Stock Changes
3.2. Sub-Pool Wastewater and Sewage
4. Flows: Calculation Guidance
I have various forms of information from IPCC and EEA which will inform this section (some of the
notes are included below). Further literature research will then be needed on the nitrates story –
outflow from landfill and wastewater processing.
The IPCC National GHG Inventory Codes are included in the relevant places on Figure 3 and these will
be used as data sources for these parts of the pool. Please note that the categories may have been
updated since the original guidance document was written – current guidance lists the categories as
‘4’ rather than 6.
Also there are many links to the human settlements pool – I need to make the links to the inflows to
the waste pool, including using the correct terminology. I also need to set up that terminology for my
flows.
General Notes from other documents
IPCC N2O
Nitrous oxide is produced in most treatments addressed in the Waste volume.
The importance of the N2O emissions varies much depending on the type of treatment and conditions during the
treatment.
IPCC Non-GHG
Waste and wastewater treatment and discharge can also produce emissions of non-methane volatile organic
compounds (NMVOCs), nitrogen oxides (NOx), and carbon monoxide (CO) as well as of ammonia (NH 3).
However, specific methodologies for the estimation of emissions for these gases are not included in this Volume,
and the readers are guided to refer to guidelines developed under the Convention of Long Range
Transboundary
Air Pollution (EMEP/CORINAIR Guidebook, EEA, 2005) and EPA's Compilation of Air Pollutant Emissions
Factors (U.S.EPA, 1995).
EEA (2005). EMEP/CORINAIR. Emission Inventory Guidebook – 2005. European Environment Agency. URL:
http://reports.eea.eu.int/EMEPCORINAIR4/en
IPCC Indirect N2O Emissions
The NOx and NH3 emissions from the Waste Sector can cause indirect N2O emissions.
NOx is produced mainly in burning of waste, while NH3 in composting. Overall, the indirect N2O from the Waste
Sector are likely to be insignificant. However, when estimates of NOx and NH3 emissions are available, it is good
practice to estimate the indirect N2O emissions for complete reporting (see Chapter 7 of Volume 1).
However, for the purposes of this annex, indirect N2O emissions should be within the ‘atmosphere’ pool as this
is where the transformation occurs.
Wastewater
[from IPCC volumne 5, chapter 6]
Nitrous oxide (N2O) is associated with the degradation of nitrogen components in the wastewater,
e.g., urea, nitrate and protein. Domestic wastewater includes human sewage mixed with other
household wastewater, which can include effluent from shower drains, sink drains, washing
machines, etc. Centralized wastewater treatment systems may include a variety of processes,
ranging from lagooning to advanced tertiary treatment technology for removing nitrogen
compounds. After being processed, treated effluent is typically discharged to a receiving water
environment (e.g., river, lake, estuary, etc.). Direct emissions of N2O may be generated during both
nitrification and denitrification of the nitrogen present. Both processes can occur in the plant and in
the water body that is receiving the effluent. Nitrification is an aerobic process converting ammonia
and other nitrogen compounds into nitrate (NO3-), while denitrification occurs under anoxic
conditions (without free oxygen), and involves the biological conversion of nitrate into dinitrogen gas
(N2). Nitrous oxide can be an intermediate product of both processes, but is more often associated
with denitrification.
[from EMEP/EEA Guidebook]
Biological treatment plants, minor importance to air – N2O most important here. NH3 is also possible,
but contribution to total emissions is minor.
In most cases an insignificant source of air pollutants.
Items considered: biological treatment plants and latrines (dry toilets with underground storage
tanks).
Latrines are a minor source of NH3. In Poland however, the contribution to total ammonia emissions
is reported to be 3%.
The emission factor for latrines has been determined from the similarity between latrines and open
storage of animal manure in lagoons or ponds (Guidebook, 2006). 1.6kg NH3 per person per year with
a 95% confidence level from 08.-3.2 (guidebook 2006).
Guidebook (2006). European Monitoring and Evaluation Programme (EMEP)/Corinair Emission
Inventory Guidebook, version 4 (2006 edition), published by the European Environmental Agency.
Technical report No 11/2006. Available via
http://reports.eea.europa.eu/EMEPCORINAIR4/en/page002.html.
Nitrates and wastewater
Information on how much nitrate goes in – and what happens to sewage sludge.
http://www.who.int/water_sanitation_health/dwq/chemicals/en/nitrateschap4.pdf
Further sections/information to include
Underlying data:
suggestions of data sources to be used (e.g., reference to other guidelines);
Factors and models:
detailed descriptions of calculation algorithms for quantitative flow (and stock change) information,
labelling of flows that are determined as residual from closing balance equations;
Uncertainties
data quality issues and other items critically affecting results; indication of potentially missing flows;
References
bibliography, further reading; Document version, author contact information.