Review Comments by Experts on First Order Draft of Volume 5 of 2019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories
Comment ID Volume

Comment

ExpertResponse

Authors note

2826

5

Chapter From line

To lineGeneral remark: The proposed refinement of the 2006 guideline for waste water will leadto a strong increase of emissions due to the introduction of CH4-emissions from aerobic
treatment plants (especially from those with advanced biological nutrient removal system)and due to the tremendous increase of the N2O emissionf factor for direct emissions fromadvanced treatment plants. The increase of the N2O EF can be argued, as a lot of literature
is availabe showing substantial higher N2O emissions from waste water treatment plants
compared to the default value included in the 2006 guideline. However, for the methane
emissions the number of literature justifying the introduction of this new source is muchsmaller, and is not presented in the refinement.
The new emission factors resp. MCF factors or emissions from aerobic waste water
treatment systems shall be as robust as possible in order to avoid future amendements of
the MCF.

Christoph Lampert

Accepted withmodification

We agree that the proposed refinement of emission factors could lead to astrong increse of emissions and agree that sufficient justification for therefinements are necessary. The text has been updated to include morediscussion of the source of these emissions as well as citations for the emission
factors presented.

2828

5

General remark: The refinement of the guideline should bear in mind the relevance ofsubsectors. Gathering a lot of activity data (in many cases it is not clear if information will
be available) and combine it with EFs or MCFs with a high uncertainty will not improve
the accuracy of the inventory . Especially the refinements in the waste water treatment
requires several new information which will not be available in many countries.

Christoph Lampert

Accepted withmodification

We agree that the relevance of the emissions should be considered when
determining its inclusion in the refinement. The text has been updated to offerdifferent tiers for estimating emissions to take into account the availability ofactivity data.

2830

5

General remark: All new EF, MCFs, etc. shall be supportet by relevent literature. Up to
now this is often not the case.
Units given shall be exact to avoid misunderstandings (e..g sewage sludge in kg dry
matter, wetmass before thickening, afterthickening, after dewatering, etc.)

Christoph Lampert

Accepted

Effort has been made in seeking and considering more literature in relation to
the comments' issues.

1536

5

2

An additional generic comment refers to terminology - although there are broadly threemain type of anaerobic landfills (MSW, C&D and C&I), a distinction is not made - it isimportant to note this, as DOCf values for a given organic material (e.g. paper) are lower
in a C&D landfill compared to a MSW landfill, where conditions are much more
conducive for decay to take place.

Fabiano Ximenes

Noted

No action can be taken because comment is out of scope of 2019 Refinement

1534

5

2

This chapter requires considerable editing to improve readability and to correct
grammatical mistakes - some examples below just from the first few lines

Fabiano Ximenes

Accepted

The final draft was edited before publication.

2682

5

2

1

273

The 2019 refinement gives an update of defaults for waste generation and composition.
For me it is unclear how to use this? Does this new information overwrite the defaults inthe 2006 GL. Or is does the change in defaults simply describe an autonomous
development. So 2006 GL valid for 2000; the refinement for 2010

Hans Oonk

Accepted

The text in the chapter was clarified and improved to explain that the updated
values used for the year 2010 onwards while the old values can be used foryears prior to 2010 when constructing a full time series. In addition, the valuesof year 2000 of the 2006 IPCC Guidelines is still valid and it depends on party
to decide to use them.

9728

5

2

100

101

The classification of regions in Table 2.3 does not match Table 2.1. For example, Central
Asia and Middle Africa in Table 2.1 are missing from Table 2.3 which has "Middle East"
instead. Please align the classification and names where possible to make it easier develop
calculation tools.

Mingming Wang

Accepted

Classification has been changed to ensure consistency.

9730

5

2

100

101

In Table 2.3, the % of all composition categories for each region add up to 102.5%, not
100%. Please rectify.

Mingming Wang

Accepted

Revised the number as suggested.

2756

5

2

100

101

Table 2.3: Region Western Europe: The total of all waste types including "others" amounts
to 128,3%. The waste type "others" (40,1%) is very high, and no information on theorganic carbon content can be determined. It would be helpful, if the waste types in table
3.3 correspond to the waste types in Line 83 (especially nappies are missing in MSW)

Christoph Lampert

Accepted withmodification

We make further consideration to disaggrigate 'others' to reflect more organics
content to be in line with line 83 which is form 2006 IPCC Guidelines

2412

5

2

102

126

If possible, It is better to indicate data sources supporting all default values (e.g. for dry
matter content, DOC etc.).

Takefumi Oda

Rejected

All values in this table are derived from Phyllis 2 database for biomass andwaste. The data source is referenced under the table. More effort will be put inseeking relevance references .

Comment ID Volume

Chapter From line

To lineComment

ExpertResponse

Authors note

111

First it is said, that for domestic sludge the default DOC is 5%. However in Line 110 it ismentioned that raw sludge and aerobically or anaerobically stabilized sludge may havedifferent compositions. It would be good to provide default values for raw sludge andstabilised sludge.
It would be more helpful if the default values are given as percentage of wet waste.

Christoph Lampert

Accepted

The values of DOC for raw and stabilized sludge were included in the SOD.

Kewei Yu

Rejected

To be consistant with 2006 IPCC Guidelines, percent is applied in the text and% in the table and box.

The DOC default for industrial sludge listed as 9 % seems to be inconsistent with thevalues presented in Table 2.4a.

Ole-Kenneth Nielsen

Accepted withmodification

127

Table 2.4A says for Paper industry the Nitrogen content is 0.5% with +/- 130%
uncertainty. That means -0.15% ~ 1.15% of nitrogen content. How could it be negative?
Please clarify and update if necessary.

Mingming Wang

Accepted

The 9% was based on the assumption of 35% dry matter, which corresponds toapproximately 26% on dry basis. This number is an average number for allindustrial sludges. The numbers in table 2.4.a are for sludges from specificindustries. These numbers are higher than the average for some industries andlower than the average for other industries. Clarification on this issue wasprovided in SOD.
The uncertainty values are revised and presented in Table 2.4A .

126

127

Uncertainty of Nitrogen content for Paper industry cannot be -130%; suggest revising toprovide a +130% and a more appropriate lower bound, like -90%

Jeffrey Coburn

Accepted

The uncertainty values are revised and presented in Table 2.4A .

2

126

127

It would be very useful to have a similar table for domestic sludge, i.e. a table showing
default values for CC, nitrogen content and DOC and the uncertainties.

Ole-Kenneth Nielsen

Accepted

Table 2.4 A has been revised in responseto to s the comment.

5

2

135

135

Sludge is described in the definition as "semi-solid". Depending on the water content
sludge can also be "wet" or even "dry".

Christoph Lampert

Accepted withmodification

2414

5

2

146

146

In the figure in the Box3.1A, "incineration" and "landfilling" should be linked with the"Vol 5", not "Vol 4".

Takefumi Oda

Accepted

Revised as suggested.

10212

5

2

146

147

Figure on sludge treatment pathway; the IPCC reference for Landfilling should be toVolume 5, Chapter 3 (not Vol 4)

Jeffrey Coburn

Accepted

Revised as suggested.

9734

5

2

153

In Annex 2A.1, for countries showing "NA" in some cells, does it mean data not available
or not applicable (none-existent)? And if country level data is not available, is the default
approach to use regional data? Please clarify.

Mingming Wang

Accepted

Revised as suggested.

9736

5

2

153

In Annex 2A.1, the fraction of MSW open dumped, landfilled, incinerated, composted andunspecified do not always add up to 100%, for example for Syrian Arab Republic they add
up to 105%. Please rectify.

Mingming Wang

Accepted

For countreis where the total exceeded 100%, the values were based on ranges
given in the WB publicaiton. The values were adjusted in the SOD based on
expert judgement. Also, a mistake for Thailand was found since recycling was
not taken into account and this was fixed in the SOD.

9584

5

2

153

153

It would be convenient to have the "header" of the table repeated at each page, so thereading is easier

Denise Fussen YanqueAccepted

Revised as suggested.

1564

5

2

153

154

I think I can update the data(MSW generation and treatment data) in Republic of Korea inthis table. I will submit supplementary materials in accordance with the form.

Eui-Chan Jeon

Noted

Thank you communications have been done.

10300

5

2

153

154

The small numbers 1,2,3,4,5 aren´t explained

Cristobal Felix Diaz
MorejonAccepted

Numbers 1,2,3,4,5 are explained in the footnotes.

10302

5

2

153

154

I suggest to revise any values that stand out in the Annex 2.A.1: 1) in MSW Generation
Rate year 2010: Sri Lanka 1,86, Seychelles 1,09, Bahamas 1,19, Barbados1,73, Grenada,Saint Kitts and Nevis 1,99, Guyana 1,95 almost all SIDS and situated in the Caribbean 2)

Cristobal Felix Diaz
MorejonAccepted withmodification

2416

5

2

153

154

There are no legend of data source No. in the table 2A.1.

Takefumi Oda

Accepted

2758

5

2

106

4758

5

2

107

8700

5

2

112

112

9732

5

2

126

10210

5

2

8702

5

2760

replace "percent" with "%"Agree with comment to avoid confusion, the word "semi-solid" is removed
and redrafted the sentence.

The values of the generation rates are based on the assumption that the waste is
generated by urban population only for developing countries (same assumption
was used in 1996 and 2006 guidelines). Therefore these generation rates should
be multiplied by the urban population only to estimate the total waste generated
in the country. Clear guidance has been explained.
Revised as suggested

Comment ID Volume

To lineComment

ExpertResponse

2284

5

Chapter From line
2

153

154

Sebahattin Sari

Accepted withmodification

10304

5

2

155

155

The Turkish Statistical Institute (TurkStat) compiles data from all the municipalities in
Turkey and publishes the generated amount of municipal waste biennially since 1994. The
following link refers to the indicators on waste statistics.
http://www.turkstat.gov.tr/PreTablo.do?alt_id=1019“Municipal waste generation per capita” should be calculated from the table named;
Main Waste Indicators of Municipalities.
As seen in the table municipal waste generation per capita: 0.40 for 2010, 0.41 for 2012,
0.40 for 2014, 0.42 for 2016
The title of Annex 2.A.2 at the moment isn´t corect because regional averages are notreflected

Cristobal Felix Diaz
MorejonAccepted

We keep the title to be in line with 2A.1 and adress the regional values in thetable for consistency across the chapter.

1566

5

2

155

158

I think I can update the data(Updated MSW composition data) in Republic of Korea inthis table. I will submit supplementary materials in accordance with the form.

Eui-Chan Jeon

Noted

Thank you communications have been done.

2418

5

2

156

It is better to normalize items in the table 2A.2 in line with previous line 83 (e.g. not"food/kitchen waste", but "food waste").

Takefumi Oda

Accepted

Table 2A2 is modified as suggested.

9586

5

2

156

156

It would be convenient to have the "header" of the table repeated at each page, so thereading is easier

Denise Fussen YanqueAccepted

Effort has been made on this issue to ensure consistency and transparency ofthe heading.

10306

5

2

156

157

Pay attention with the high value for plastic in United Arab Emirates 24,3

Cristobal Felix Diaz
MorejonRejected

The value was reconsidered but limited published references were found.

10290

5

2

159

273

The majority of references have more than 10 years and we want a refinement for 2019
year, please try to seek more actualized literature and studies related to waste and data

Cristobal Felix Diaz
MorejonAccepted withmodification

10292

5

2

39

50

I suggest to maintain of V5-Chapter 2: Waste Generation, Composition and Management
Data Introduction in 2006 IPCC Guidelines the following text:¨The starting point for the estimation of greenhouse gas emissions from solid waste
disposal, biological treatment and incineration and open burning of solid waste is thecompilation of activity data on waste generation, composition and management. Solid
waste generation is the common basis for activity data to estimate emissions from solid
waste disposal, biological treatment, and incineration and open burning of waste. Solid
waste generation rates and composition vary from country to country depending on theeconomic situation, industrial structure, waste management regulations and life style. The
availability and quality of data on solid waste generation as well as subsequent treatment
also vary significantly from country to country. Statistics on waste generation andtreatment have been improved substantially in many countries during last years, but atpresent only a number of countries have comprehensive waste data covering all waste
types and treatment techniques.¨

Cristobal Felix Diaz
MorejonAccepted

1538

5

2

40

40

This sentence requires clarification - do you mean to say that the Chapter uses waste
generation data published in 2010?

Fabiano Ximenes

Accepted withmodification

The introduction part has been rewritten to increase clear understanding.

1540

5

2

42

42

Suggested change in text for clarity: "…subjected to change over time"

Fabiano Ximenes

Accepted withmodification

The introduction part has been rewritten to increase clear understanding.

1542

5

2

43

43

"…measures such as…"

Fabiano Ximenes

Accepted withmodification

The introduction part has been rewritten to increase clear understanding.T

4756

5

2

62

Kewei Yu

Accepted withmodification

The introduction part has been rewritten to increase clear understanding.

10294

5

2

62

63

The value of Fraction of MSW disposed to landfills in Eastern Africa of 0.98 like veryhigh. It is greater than Europe, Asia, America. Please revise this or explain in the text

Cristobal Felix Diaz
MorejonAccepted

The value was checked and found that it was correspond to dumpsites and notlandfills. Revision has been done.

10296

5

2

62

63

The value of MSW Generation Rate in the Caribbean 0,95 really is very high incomprison with the other Regions, except with Oceania.

Cristobal Felix Diaz
MorejonAccepted withmodification

According to references used( Hoornweg et al, 2012), the values of thegeneration rates are based on the assumption that the waste is generated byurban population only for developing countries (same assumption was used in
Revised 1996 and 2006 IPCC Guidelines). Therefore these generation rates
should be multiplied by the urban population only to estimate the total waste
generated in the country. The high value of WRG in Caribbean include waste
generation from tourists.

replace "," with "." for decimal point in all places

Authors note
The data from Eurostat is the same data used in Turkstat. In order to becomparable across countries, data from Eurostat is used.

The data to be used should be comparable among countries and therefore it was
decided to use 2010 as the year where most of the data can be available.
Revised as suggested.

Comment ID Volume

ExpertResponse

Authors note

10298

5

Chapter From line
2

62

To line63

The values of Australia and two Small Islands Developing States in Oceania would be
revised because are very big mainly Melanesia and Polynesia

Comment

Cristobal Felix Diaz
MorejonAccepted withmodification

2408

5

2

62

63

Figures in the table 2.1 should not include comma "," (e.g. 0,34), but period "." (e.g.
0.34).

Takefumi Oda

Accepted

According to references used( Hoornweg et al, 2012), The values of thegeneration rates are based on the assumption that the waste is generated byurban population only for developing countries (same assumption was used in
Revised 1996 and 2006 IPCC Guidelines). Therefore these generation rates
should be multiplied by the urban population only to estimate the total waste
generated in the country. The high value of WRG in Melanesia and Polynesia
include waste generation from tourists.
Revised as suggested.

8944

5

2

62

63

For TABLE 2.1, MSW generation rate is varied not only between regions but also
economic level of the region. Regional default values should be shown at least for low,
middle and high income situations.

Masato Yamada

Rejected

There are many factors that can affect the MSW generation rates apart from theeconomic level. The classificaiton by region partly captures the economic level .
It would not be possible to capture all factors in the categorization. It was
decided to use the regional classificaiton, which is consistent with what wasdone in the 2006 IPCC Guidelines, which is the best option for categorization.

2410

5

2

79

81

It thought be that most paper and cardboard, and textiles (natural fiber) can be classified asorgaric waste, too.
Otherwise wood is also not entirely included in this classification since wood as plyboard
containes small amount of adhessive made by fossil carbon.

Takefumi Oda

Accepted withmodification

Information on waste components containing fossil part were mentioned in the
SOD.

8704

5

3

1

288

It is difficult to interpret how to use this chapter with the 2006 IPCC GL. In othervolumes, the completely unchanged sections have been indicated with a 'No refinement'
while sections that have been partly changed have had the original text from the 2006
IPCC GL in marked with grey and the new text unmarked. The lack of this makes it very
difficult to assess what is new and how it is consistent with the text of the 2006 IPCC GL.
This should be improved.
"some studies…that is" should be "some studies…that are"Ole-Kenneth Nielsen

Accepted

In general, same basis of refinement have been applied for all volume. Since
refinement issues in this chapter are DOCf and MCF of active aeration,therefinement text covers only the issues addressed in the TOC. Nevertheless, we
improve the structure of this chapter in order to facilitate invenotry compiler.

10224

5

3

101

102

Jeffrey Coburn

Accepted

8706

5

3

101

104

The issue of N2O emissions from landfills is mentioned here as well as in box 3.0b withseemingly several references. However, no quantitative information is available. The
expected magnitude of emissions should be mentioned and if possible a methodology anddefault EF should be included if the data allows it. Otherwise, this should be clearly stated.

Ole-Kenneth Nielsen

Accepted withmodification

Description in Box is not intended to give any guidance nor detailed
methodology. However we recongnize that information in this part is moresuitable to put in Appendix. We have re-located it to Appendix 3B with moreellaboration.

Revised as suggested.

10222

5

3

101

127

The intro and text box is written in broken English, with many typos. Recommend
someone with English as a primary language talk with the author and re-write this box.
Some specific edits/issues are outlined in the following comments on specific lines in the
text box.

Jeffrey Coburn

Accepted

We have rewriiten the text in Box 3.0B. However, we have considered thesuitability of this box and reallocated it to Appendix 3A.

10226

5

3

104

104

"...emission estimated is…" should be either "...emission estimation is…" or "...emission
estimation methodology is…"

Jeffrey Coburn

Accepted

Revised as suggested.

Comment ID Volume

To lineComment

ExpertResponse

Authors note

2560

5

Chapter From line
3

105

127

As far as I know, normal landfills are not a significant source of N2O, because processes
take place under anaerobic conditions. Ammonification does take place and as a result
large part of the N in the wate will end up as ammonia in th leachate of a landfill. However
nitrification does not occur, simply because the conditions in a landfill are not favourable
for nitrification. A clear indication of absence of is that landfill leachates do not containnitrate/nitrite. When no nitrification occurs, no denitrification will occur and also no N2Oemissions might occur. So N2O-emissions from normal landfills are unlikely to besignificant. As far as I know, N2O-emission measurements in the past have proved that
N2O-emissions from landfills, covered with soil and e.g. grass vegetation are not thatdifferent from N2O-emissions from other grass-lands (see also Zhang et al., 2009:
Atmospheric Environment, Volume 43, Issue 16, May 2009, Pages 2623-2631, who statethat processes in the top-cover are the main source of N2O at landfills). Rinne (2005),
comes to the conclusion, that emissins might be 10 times as high, but also concludes that
due to the small area of landfills, compared to other surfaces, landfills are a minor sourceof N2O. When expressed in CO2-eq., N2O-emissions are about 1% of methane emissions(based on table 2 in Rinne, 2005). You further refer to Matthew (2005), who concludes:"Mean fluxes of N2O were negligible over the duration of the study". Also Ishikagi
concludes that N2O-emissions are not often found in emissions from landfills. Semiaerobic management of poorly managed surfaces might result in N2O. So based on yourliterature, I think N2O-emissions from nomal landfills is of no concern.

Hans Oonk

Accepted withmodification

The "normal landfill", which might means anaerobically managed SWDS, has
not been considered to be a siginificant N2O source so far. But updating of thescientific fact must be essentially expected and we described it with moredetails in Appendix 3A for future development of the guideline. The new
description is going to cover the various type of SWDS management.

2768

5

3

105

127

BOX3.0B could be skipped as no further guidance (emission factors etc) are given.
Especially for N2O from anaerobically managed landfills the relevance is not obvious (seealso the precendent comment).

Christoph Lampert

Accepted withmodification

2556

5

3

105

127

I don't understand the intention of Box 30B. What guidance does this box intend to give.
Do you suggest that countries should quantify N2O-emissions from aerobic landfills?
From semi-aerobic landfills? Or from all landfills? If so, please be clear about yourintentions and provide proper guidance. If not, please remove the box.

Hans Oonk

Accepted withmodification

Description in Box is not intended to give any guidance nor detailed
methodology. However we recongnize that information in this part is moresuitable to put in Appendix. We have re-located it to Appendix 3B with moreellaboration.
See comment 2768 above.

2558

5

3

105

127

At the moment you only refer to the CDM-document. If you want countries to estimate
N2O from semi-aerobic or aerobic landfills, please give clear and complete guidance. Youmight decide to use option 2 in the CDM-method (page 9 in the CDM methodology) as a
Tier 1 in the 2019 refinement. And you might add use of measurements as a Tier-2/3
method. But you need to include clear guidance, otherwise you will have different
interpretations by different countries.

Hans Oonk

Rejected

See comment 2768 above.

10228

5

3

107

108

The FAR (2007) [and it is "Fourth" not "Forth"] is after the 2006 Guidelines, so "already"is inappropriate; "mention on it" is bad English. Would re-write this sentence entirely as:"The IPCC Fourth Assessment Report (2007) indicated significant generation of N2O ispossible from SWDS; however, the 2006 IPCC Guidelines document does not present a
methodology or factors by which N2O emissions may be estimated.

Jeffrey Coburn

Accepted

Revised as suggested.

2764

5

3

107

119

Aeration of SWDS typically takes place when the landfills are closed and the landfill gas
production diminishes and the gas can not be used for energy production or even can not
be flared. This time will be reached several years (or even decades) after the closure of thelandfill. Therefore, waste composting can not be regarded as analogue process (at least notwith the intensive rotting stage).

Christoph Lampert

Accepted withmodification

10230

5

3

108

111

The description of AM0083 is poor and there are 2 options for estimating N2O emissions,but they are not "optional". Suggest re-writing as: "Approved CDM methodology,
AM0083 (UNFCCC CDM Executive Board 2009), is applicable to project activities
where landfilled waste is treated aerobically on-site by means of air venting (overdrawing)or low pressure aeration with the objective of avoiding anaerobic degradation processes
and achieving aerobic degradation. The AM0083 provides two alternative methodologies
for estimating N2O emissions."

Jeffrey Coburn

Accepted

This part is not intending to provide the guidance. And every kind of
information will be given here as an example or practices. In particular, theexplanation for adopting the emission factor from composting is theinformation given by the AM083, and this is not recommendation nor default. I
understand there might be lots of arguments on appropriateness of emission
factor, but the discussion will be skipped because the methodology itself is notgoing to be introduced in this refinement. However we considered thesuitability of this part and relocated in Appendix.
Development of text on example of higher estimation from CDM project wasdone in the appedix 3B to address the used of higher teir in estimation ofemission

Comment ID Volume
10232

5

Chapter From line
3113

To line114

Comment
Last half of sentence needs re-writing. "... and the emission factor given in AM0083 isbased on waste composting, which is an analogus process to low pressure aeration."

ExpertResponse

Jeffrey Coburn

Accepted

Revised as suggested.

Authors note

Revised as suggested.

10234

5

3

114

119

Please re-write; poor grammar…

Jeffrey Coburn

Accepted

225

5

3

118

119

Revise to - that can also be taken into consideration

Archis Ambulkar

Accepted

Revised as suggested.

10236

5

3

120

120

"...is also common and have been…" should be "...is also common and has been…

Jeffrey Coburn

Accepted

Revised as suggested.

2766

5

3

120

127

The relevance is doubtful. It is true, that denitrification occurs under anaerobic conditions.
However, denitrification requires a preceding nitrification step, which requires oxygen. In
anaerobic landfills oxygen is not available (at least not in the major part of the landfill).

Christoph Lampert

Rejected

It is widely known that those two processes are taken place in landfills at
different zone. Environmental condition in landfills is not uniform andmigration of substances should be considered.

10238

5

3

122

127

Please re-write; very difficult to understand what is being said here.

Jeffrey Coburn

Accepted

Revised

8708

5

3

136

189

This is an example of where it is not clear how this text is to be used with the 2006 GL.
Should the text on DOCf and MCF replace the text in the 2006 GL and the text on
methane recovery, oxidation factors, half-lifes, etc. Is unchanged? It would be useful, if
this could be explicit what parts of the 2006 IPCC GL that are updated.

Ole-Kenneth Nielsen

Noted

The refinement of this DOCf section is developed to be used with existing
2006 IPCC Guidelines. The heading of this section indicates that they are to be
used as an update of DOCf section.

1544

5

3

139

139

"papers" include the categories listed immediately after - better to say "paper products
including coated paper,…"

Fabiano Ximenes

Accepted

Revised as suggested.

1546

5

3

140

141

Harvested wood products such as sawn wood and engineered wood products have beenshown to be less decomposable than garden waste - thus would be more appropriate to usethem as examples of materials with low biodegradability

Fabiano Ximenes

Accepted

Revised as suggested.

226

5

3

144

144

Revise to - residual fraction present in theArchis Ambulkar

Accepted

Revised as suggested.

227

5

3

145

145

Revise to - were found to largely vary from one component to other, ranging from few

Archis Ambulkar

Accepted

Revised as suggested.

228

5

3

146

146

Revise to - percentages (for wood) to high percentages

Archis Ambulkar

Accepted

Revised as suggested.

229

5

3

149

149

Not how it fits in paper comparison statement - "whereas the diaper exhibited limited
biodegradability"

Archis Ambulkar

Accepted

Revised as suggested. The sentence was revised to "Meanwhile, the diaper
exhibited limited biodegradability".

1548

5

3

149

150

It is important to make a distinction here - the paper cited (Wang et al 2016) describes the
decay of hardwood and softwood tree branches. Branches differ considerably fromstemwood in their anatomy and chemical profiling. I would suggest citing an earlier paper(Wang et al 2011) which describes the decay of sawn wood products and engineered wood
products, which are al derived from stemwood. In Wang et al, the carbon conversion
factors (or DOCf) range from 0-7.8% for hardwoods and 0.1-1.4% for softwoods. Of theengineered wood products, the DOCf was very low for the key product types(particleboard, MDF and plywood), ranging from 1.1-1.4%. The only exception wasoriented strand board (OSB) made of hardwoods, which had a DOCf of 19.9% (OSB
made of softwooods had a DOCf of 0). However, as OSB production represents only
about 5% of global engineered wood products manufacture (FAO 2016), the weighted
average of DOCf for engineered wood products would be approximately 1.7%.

Fabiano Ximenes

Accepted withmodification

Revised the sentence to "Wang et al. (2011), carbon conversion to methane
were different for softwoods (0.1-1.4%) and hardwoods (0-7.8%). Of theengineered wood products, the DOCf was low for key product types such as
particle board, medium-density fiber board and plywood, ranging from 1.11.4%."

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Fabiano Ximenes

Accepted

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Suggest rewriting the sentence for accuracy: "The carbon loss for wood samples recoveredfrom landfills were found to be low and climate did not influence much on decay of woodin landfills - the observed higher levels of decay for some wood samples were attributed todifferences in wood species (Ximenes et al., 2015)."
Table 3.0 provides DOCf for different types of waste and also for bulk waste. It is unclear
if a country/city should use the specific DOCf for different types of waste (based on thedefault fraction provided in Volume 5.2), or use the value for bulk waste because different
types waste are not collected separately in some nations or areas. Please clarify.

Mingming Wang

Accepted withmodification

Revised as suggested.

The following description is provided in Table 3.0 for bulk waste "to be used
when the waste composition is not available".

Comment ID Volume

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ExpertResponse

Authors note

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I would suggest that based on DOCf values available in the literature for harvested wood
products other than paper products and garden waste, the suggested DOCf for lessdecomposable waste is too high. Some of the references quoted are in my view unsuitable
for the derivation of DOCfs (e.g. Banyard et al 2017 use BMP tests to derive decay
factors - however BMP values are not a suitable proxy to determine DOCf in real life
landfills, with experts (e.g. Prof. Barlaz at NCSU) in agreement that results derived fromreactors kept under anaerobic conditions more closely resemble landfill conditions). The
literature for harvested wood products (e.g. Wang et al 2011) suggests that there is little
variation in the decay of sawn wood and engineered wood products, allowing for acommon default value to be used for those products (these results have been confirmed byindependent bioreactor results carried out in our laboratories in Australia - twomanuscripts are currently been prepared describing these results). As there is no available
data to support a weighted average based on the relative volumes of garden waste and
HWPs disposed off in landfills, I would suggest using a straight average of the relative
DOCfs as a way to derive the default DOCf for less decomposable waste. An alternative
DOCf for less decomposable waste could be derived as folows: Garden waste (treebranches, etc...) - average of factors provided by Eleazer et al (1997) and Wang & Barlaz(2016): DOCf = 13.8%. For harvested wood products other than paper, the average would
combine published factors for engineered wood products (1.7% from Wang et al 2011 and4.8% from Ximenes et al 2017 - average - 3.2%) and published factors for sawn wood
(Wang et al 2011 - average 2.4%). Thus the overal average for engineered wood products
and sawn wood would be 2.8%. The new revised DOCf for less decomposable waste
would be the average between this value and that for garden waste ((13.8 + 2.4)/2) =8.1%. Details of additional references as follows: 1) Wang, X., Padgett, J.M., De la Cruz,
F.B., Barlaz, M.A., 2011. Wood biodegradation in laboratory scale landfills. Environ. Sci.
Technol. 45, 6864–6871. 2) Ximenes, F.; Cowie, A., Barlaz, M. 2017. The decay ofengineered wood products and paper excavated from landfills in Australia. Waste
Management. https://doi.org/10.1016/j.wasman.2017.11.035

Fabiano Ximenes

Accepted withmodification

The proposed DOCf value for less decomposable wastes is revised from 0.2 to
0.1. by using the recommended methodology.

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In the table 3.0 there is no clear explanation what the values in brackets (n) mean.

Irina Govor

Accepted withmodification

The "n" values are removed from Table 3.0 to avoid confusion. Only numberof references are provided.

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167

When large amount of rapidly degradable organic waste is landfilled, conditions might
become acidic (so hydrolysis and acificication proceed rapidly) and methanogenesis isinhibited. In such a situation DOC-concentrations in a landfill leachate might become high.
In combination with high excess rainfall, this means that a large part of DOC might be
flushed out. Experiences at older Dutch landfills (pre-1985 ... I heard it from older landfill
engineers, when I just started my work) was that sometimes high DOC-concentrations inleachate could occur. However with a more mixed waste composition (increased amountof moderately degradable material, larger amount of biological inerts, that might even act
as a buffer), this poblem has disappeared. I think less than 1% of methane potential isflushed out as DOC (DOC-concentrations in leachate are typically 1000-2000 mg/l; excess
rainfall is 300 mm, so you have annually about 0.3-0.6 kg/m2/yr of DOC flushed out withleachate). With a landfill of 30 m high and a DOC of 100 kg/m3, you have 3000 kg DOC
stored per m2, so the 0.3-0.6 kg/m2/yr flushed out is 0.01-0.02% of total DOC per year.
So for many countries, this is not relevant. Please do not make the line 172-174 (therefore
it is good practice ...) a general rule. You might rephrase this as: "Under wet, tropicalconditions and when the waste contains large part of rapidly orgnic waste, it is goodpractice .... "Hans Oonk

Accepted withmodification

Revised the sentence to "Under extremely wet condition such as high leachatelevel in landfill and when the wastes contain high percentages of rapidly
biodegradable waste components, it is good practice …".

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If you give guidance on correcting methane emissions for DOC flushed from landfills, youneed to provide the appropriate equations. And this correction should be included in the
IPCC waste model (MS Excel-tool provided by IPCC).

Hans Oonk

Accepted withmodification

The guidance (Box 3.0b) is provided as information to the users to aware thesignificance of DOC leaching under specific conditions, e.g. high food waste
percentages and wet climate condition. Correction to the DOC available forbiodegradation can only be done when information of DOC leaching from
SWDS is available. This estimation will only performed when using higher tiermethodology and not for the default methodology.

Comment ID Volume
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To lineComment

ExpertResponse

Authors note174

BOX 3.0c: The relevance of the DOC leaching is based only on 1 literature (Zahn et al(2017) which is not available, (article in press). Further this literature deals with "highfood waste content MSW landfills", which is not a clear definition of the waste type. The
estimation of the DOC leaching seems to be restricted to anaerobic landfills under wet
conditions and to leachate with a high organic loading in high food waste content MSW.
What does it mean "wet conditions" (>1000mm annual precipitation etc.)? DOC leachingis only relevant for high food waste content MSW?
"Recent literature" comprises only 2 citations. However, the fact that carbon wash out
increases with rainfall is quite obvious ((Karanjekar et al., 2015). It is unclear, that theconsideration of the DOC leaching can be considered as "good practice" up to now.
In the 2006 Guideline page 3.13 it is said: "The amount of DOC leached from the SWDS
is not considered in the estimation of DOCf. Generally the amounts of DOC lost with theleachate are less than 1 percent and can be neglected in the calculations". It should bemade clear, in which cases the leachate of DOC shall be considered.
It will be difficult do collect relevant data especially in countries where climatic conditions
vary significantly within the country
good practice in italic

Christoph Lampert

Accepted withmodification

In Zhan et al. (2017), loss of LFG potential by 13% was observed in high foodwaste content MSW with food waste composition of approx. 60% (wet weightbasis). The wet condition refer to high leachate level in the landfills. The
guidance (Box 3.0c) is provised as information to the users to aware thesignificance of DOC leacing under high food waste percentages and wet climate
condition.

Kewei Yu

Accepted

Revised as suggested.

Archis Ambulkar

Accepted

Full term of MSW is provided.

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171

Define MSW in the sentence - abbrevation used for the first time in this chapter

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189

Table 3.1 introduces three new MCFs for different site types. However, no references areprovided for the MCFs. The references for these new MCFs should be transparently
provided.

Ole-Kenneth Nielsen

Accepted

References was given in manuscript in the Box3.0A. We also put thereferences in Table 3.1 after Matsufuji et al.

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189

The improvements in Table 3.1 would be justified and in which literature it is based. I
agree whith the changes because give more amplitude of selection

Cristobal Felix Diaz
MorejonAccepted

References was given in manuscript in the Box3.0A. We also put thereferences in Table 3.1after Matsufuji et al.

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footnotes 3 and 5: conditions for the classification as poor management are mentioned. It
is not clear, if all conditions have to be met, or just one out of them.
It is questionable if relevant information will be available for the new types of sites
especially for "managed poorly - semi aerobic" and "managed poorly - active aeration"

Christoph Lampert

Accepted withmodification

If the situation of management meets at least one condition in the footnote, it isconsidered as poorly-managed.
It was revised in the SOD to increase understanding.

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218

Sentence not clear - updated information on reported in the variation of DOC percentages

Archis Ambulkar

Accepted withmodification

The sentense is revised as "This section provides updates on uncertainty ofdefault DOCf value as shown in Table 3.5 (Updated)".

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222

Uncertainty of Fraction of Degradable Organic Carbon Decomposed (DOCf) = 0.2 of +/140%. Again a -140 % uncertaintin in not physically possible. Suggest providing
different upper and lower limits of unceratinty for this value.

Jeffrey Coburn

Accepted withmodification

The uncertainty value is re-calculated using the reported DOCf values used toderive default DOCf value for less decomposable waste.

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It is better that uncertainties of MCF newly established are indicated as well as DOCfs'.

Takefumi Oda

Accepted

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Uncertainty range is missing in MCF=0.7.

Masato Yamada

Accepted

Revised as suggested.

4760

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Kewei Yu

Accepted

Revised as suggested.

216

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42

42

Define SWDS in the sentence - abbrevation used for the first time in this chapter

Archis Ambulkar

Accepted

Revised as suggested.

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48

Revise to - the fraction of degradable organic carbon (DOC) in the waste..

Archis Ambulkar

Accepted

Revised as suggested.

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Chapter, upper case

Kewei Yu

Accepted

Revised as suggested.

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70

"High-pressure … reduction of moisture". Please be aware of that this is a very one-sided
description of an ongoing technological discussion. And also be aware of existing
commercial interests. Prof. Stegmann is owner of the company IFAS, which is the supplierof low-pressure aeration. Marco Ritzkowski works at the Technical University of
Hamburg (TUHH), at a department, also led by prof. Stegmann. TUHH/IFAS havecommercial interests in having low-presure aeration accepted and have competing
technologies as high-pressure aeration discredited. In USA companies exist, that promote
high-pressure aeration. Systems in USA have different objectives than the German
projects, start at an earlier stage. The American objective is more to complete
biodegradation more rapidly and reduce amount of waste, thus creating space for new
waste. The German objective is to reduce the leachate concentrations of older landfills. So
they cannot be properly compared. Both systems are in development and I think it is too
early to claim that one is working and the other not. Please remove this sentence.

Hans Oonk

Accepted

Relevant sentence was removed and revised for clearer understanding.
We aim to provide relevant knowledge and current existing technologies as
INFORMATION in the guideline.

methane should be CH4

Table 3.5 is updated to address uncertainty.

Comment ID Volume

ExpertResponse

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To line73

Revise sententence - has shown 70% reductions in CH4 emissions

Comment

Archis Ambulkar

Accepted

Authors note
Revised as suggested.

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75

75

Is the term "escape substantial penetration of oxygen" correct

Archis Ambulkar

Accepted

Revised as suggested.

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75

Something is wrong with this sentence: "...the escape substantial penetration…"
Suggested revision "…the escape of oxygen and the lack of substantial penetration…"

Jeffrey Coburn

Accepted

Revised as suggested.

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79

The two literatures presented show very large differences in respect to the reduction of
methane emissions. Consequently a MCF value would imply a high range of uncertainty.It
would be helpful if literature is provided including long term measurements on a field
scale, including type of waste disposed off, measurement methods, type of ventilation
system etc.

Christoph Lampert

Rejected

The investigations shown in the literatures were field scale projects which are
different from long-term measurement. Technical properties were provided ineach literatures but we can not disclose them in detail in this refinement.

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I disagree with your conclusion that both Raga and Hrad drew conclusions on reduction inmethane emissions. I've been reading Raga et al. and Hrad et al, and do not find theconclusion, as you mention in your draft. Hrad mentions, that methane concentrations
above the surface were measured twice a year, but does not report results (page 2062 in
Hrad et al., under 2.2 it says 'data not shown') and interpret them. Hrad et al. performed
surface screening, which only gives a qualitative indication of emissions but is result in aquantification of emissions. I think, the effectiveness of landfill aeration is stillinsufficiently demonstrated, and is depending on the aeration design and operation. Whenwell designed, methane emissions might be completely abated. However effectiveness isstill unsufficiencly demonstrated and large parts of a landfill might be out of reach of theoxidation system. E. g. Van Turnhout in his PhD-thesis (2017, could not add this to thisreview, but available online via:
http://pure.tudelft.nl/ws/files/22085082/dissertation_agvanturnhout.pdf, see chapter 5)
performed CFD-calculations and demonstrated that in current designs for low pressure
aeration, large part of the waste gets insufficient oxygen to establish aerobic conditions. I
am also not aware of convincing secondary indications of successful aeration in mostdemonstration projects (e.g. a sigificant reduction in NH4+ and COD in leachate). In
conclusion: as long there is no agreement on what aeration systems to use, and without
convincing evidence on it impact on methane emissions, I don't agree with any default
value for MCF at aerobic landfills. I do understand the potential methane emission
reduction. However I think the way forward is to monitor methane emission reduction
project by project (using operational data that are normally collected in the projects) andgive guidance how to use this information to quantify methane emission reduction. I will
mention possibilities in my next comments.

Hans Oonk

Accepted withmodification

Taken into consideration and revised as approapriate.

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All demonstrations of low pressure aerotion of landfills you mention until now are
performed on old landfills. These are landfills that at first are operated as conventional
landfills. Only in the final stage of decomposition (IFAS is one on the key developers of
aerobic landfills in Germany, and they advise to implement landfill aeration, when 90% of
the easy and moderate biodegradable material is reduced by more than 90% (see ref Van
Vossen et al., page 22. Added in this review). Also theexamples you mention inyour draft(Raga et al., Hrad et al.) are examples of normal landfills, that are retrofitted as aerobic
landfills. Active aeration in an earlier stage is considered economically less feasible andbears risks of accidental landfill fires (Van Vossen et al., Ritzkowsi and Stegman, 2012
from your reference list). In such a landfill, MCF is not a constant value throughout its
emission lifetime. Instead biodegradation will initially proceed under largely anaerobic
conditions and emissions can be calculated, assuming the MCF from the 2006 guidelines.
Only in the final stages, emissions might be calculated with a modified model, whichmight be simply a reduced MCF. You might try and adapt the current IPCC-model toallow changes of MCF in time. However you might also recommend to calculate the effectof changing MCF by using seperate models, e.g. one assuming a higher value of MCF forthe years when a landfill is not aerated, and one for years when a landfill is aerated.

Hans Oonk

Accepted withmodification

Taken into consideration and revised as approapriate.

Comment ID Volume

To lineComment

ExpertResponse

Authors note

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I do understand the potential methane emission reduction in landfill aeration. However I
think the way forward is to monitor methane emission reduction project by project (using
operational data that are normally collected in the projects) and give guidance how to use
this information to quantify methane emission reduction. The situation is similar tomethane collection at landfills in 1999/2005, when the GPG and 2006 GL were drafted. Atthat time there was serious concern on the validity of default values for methane
collection. At the same time, methane collection and utilisation is easily measured at
individual landfills and therefore use of actual measurement data was included in the
GPG/2006 GL as good practice. I think the same goes for aerated landfills. There noagreement yet on how landfill aeration should be designed and operated, and aeration
systems vary considerably. At the same time, daily operation of landfill aeration provides
monitoring data. The 2019 refinement should give guidance how to use monitoring data of
individual projects of quantify methane emission reduction. (i) One option (mainly valid
for systems using overextraction and perhaps not applicable to other systems) is toquantify MCF during aeration from the ratio of CO2 ad CH4 in the gas extracted.
Aanerobic decomposition results in a micture of about 50% methane and 50% CO2.
Aerobic decomposition results in 100% CO2. So the ratio CO2/CH4 is an indicator of
aerobic vs. anaerobic processes. (ii) an another option might be to consider an approach inwhich initial decomposition of waste is still to produce 50% methane and 50% CO2, andaeration results in oxidation of methane produced inside the landfill. In this way, methane
emissions can be calculated using a conventional generation model, but need to becorrected for methane recovery and internal methane oxidation. Methane recovery andmethane oxidation an again be calculated from CH4 and CO2-collected (e.g. assumingthat collection and internal oxidation equals 50% of the moles of CH4 and CO2collected). (iii) apart from having impact on the ratio aerobic/anaerobic decomposition,
aeration might enhance biodegradation. So most likely upon aeration, the amount CO2-C
and CH4-C collected exceeds the amount of DOC dissimilated, as calculated with the
IPCC waste model. So maybe a modified model needs to be made in which DDOCm/dt(and thus the decrease of remaining methane potential in time) is not calculated, but
quantified, based on actual monitoring data. I do realise that these three options require
more explanation. It will be too far fetching to do this in this comment. The main message
I want to convey is that there are possibilities to quantify he effect of aeration on a landfill
by landfill basis, using monitoring data that are collected in daily operation of an aerobic
landfill.

Hans Oonk

Accepted

We recognize the importance of accumulation of the measured data for
inprovement of methodology and development of EF. The description in MCF
using locally available deta including measured data is added though this isregarded as higher Tier and is out of scope of the refinement. For Tier 1
methodlogy, single and conservative MCF is required.

220

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79

Revise to - reduction of CH4 emissions by about

Archis Ambulkar

Accepted

Revised as suggested.

221

5

3

80

80

Revise to - Cases of lower conversion during aerobic conditions

Archis Ambulkar

Accepted

Revised as suggested.

222

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84

84

Revise to - Aeration of fresh waste is less effective than aged waste in SWDS

Archis Ambulkar

Accepted

Revised as suggested.

223

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85

Revise to - the tropical climate or where moist waste is to be disposed.

Archis Ambulkar

Accepted

Revised as suggested.

224

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85

86

Revise to - Best results of aerobic coversion in managed well-active aeration category
correspond to 0.4 MCF default value.

Archis Ambulkar

Accepted

Revised as suggested.

10216

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85

86

"Best result of aerobic conversion as 0.4 was given to a default MCF ..." Would be moreclear if it said "The best observed result of aerobic conversion of 60% was used to develop
a default MCF of 0.4 for managed well - active-aeration."

Jeffrey Coburn

Accepted

Revised as suggested.

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88

This sentence appears to be for "managed poorly - active-aeration." Also ".average"
should be deleted so the sentence should read "Default MCF of 0.7 for a category ofmanaged poorly - active-aeration was derived…" Also, the range "shown above" was 0.4
to 0.9, not 0.5 to 0.9.

Jeffrey Coburn

Accepted

Revised as suggested.

10220

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89

Should note that this category was included in the 2006 Guidelines with an MCF of 0.5(for clarity).

Jeffrey Coburn

Rejected

This is a refinement document and non-change part is kept as original.

259

5

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103

104

Change to - as well as the operating conditions

Archis Ambulkar

Accepted

Revised as suggested.

260

5

5

113

113

Change to - commercially operated pyrolysis-melting plant, condensable

Archis Ambulkar

Accepted

Revised as suggested.

261

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115

Change to - system is unavailable

Archis Ambulkar

Accepted

Revised as suggested.

Comment ID Volume

Chapter From line

4768

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To lineComment"it is" should not be in italic, and check others

ExpertResponse

Kewei Yu

Accepted

Authors note
Revised as suggested.

262

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125

Change to - system is unavailable

Archis Ambulkar

Accepted

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132

In Table 5.3A, default CH4 emission factors for pyrolysis of waste vary a lot by different
reactor types and operating temperatures. However, it can be challenging forcountries/cities to find out such level of details about each of their waste incineration
plants. Therefore it is recommended that IPCC also provides some default
situation/emissions factors for each region/nation if it is not possible to determine which
specific ones to use. It is also recommended that IPCC or UNFCCC requests country-levelresearch (or regular surveys) on current incineration technology deployment in eachcountry.

Mingming Wang

Accepted withmodification

Revised as suggested.

Archis Ambulkar

Accepted

Revised as suggested.

Irina Govor

Accepted

Revised as suggested.
Revised as suggested.

Since there is little information on the regional data and results regarding
pyrolysis, gasifiction, ans plasma technology, it would be difficult to supply theregional data for the new technologies. We decided to put one sentence in the2009 Refinement to clearly respond to this comment as follows: "GHG
emissions from thermal treatments of solid wastes are highly dependent on their
physico-chemical properties of solid waste. Since pyrolysis, gasification, andplasma technology are quite new to treat solid wastes, little information is now
available for reflecting the regional characteristics of solid wastes to determine
the regional CH4 and N2O factors from the new technologies".

263

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133

Change to - gasification vary with the types

8514

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141

Table 5.5 should be Table 5.3B

264

5

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147

Change to - and the operating conditions

Archis Ambulkar

Accepted

265

5

5

155

155

Change to - and the operating conditions

Archis Ambulkar

Accepted

Revised as suggested.

8516

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159

Words "waste plasma" should be better change to "waste plasma technology" or "waste
plasma plants"

Irina Govor

Accepted

Revised as suggested.

266

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162

Change to - and the operating conditions

Archis Ambulkar

Accepted

Revised as suggested.

10312

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165

In the new elaborated Table 5,4 A the authors forgot to put in place the numbers 1,2,3 thatmatch with different references and not permit to can realice a bigger analysis.

Cristobal Felix Diaz
MorejonAccepted

Revised as suggested.

10310

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77

I propose to add in the beginning of the Introduction the first paragraph of theIntroduction of Chapter 5 of 2006 IPCC Guidelines ¨ Waste incineration is defined as the
combustion of solid and liquid waste in controlled incineration facilities. Modern refuse
combustors have tall stacks and specially designed combustion chambers, which provide
high combustion temperatures, long residence times, and efficient waste agitation while
introducing air for more complete combustion. Types of waste incinerated include
municipal solid waste (MSW), industrial waste, hazardous waste, clinical waste andsewage sludge. The practice of MSW incineration is currently more common in developed
countries, while it is common for both developed and developing countries to incinerateclinical waste.

Cristobal Felix Diaz
MorejonAccepted withmodification

The sentences was added in the SOD but not in the begining of the chaapter inorder to have a smooth explanation of thermal technologies in this chapter.

8512

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94

There is no explanation how to estimate carbon dioxide emissions from these newtechnologies and emission factors for them are not presented.

Irina Govor

Accepted withmodification

Pyrolysis, gasification, and plasma technology are usually applied to produce
valuable fuels from solid wastes. The fuels generated from the newtechnologies are generally combusted to use as fuel at either the site or outside.
It is also expected that the CO2 emissions of new technologies are similar to
those of solid waste incineration and stationary combustion devices using fossil
fuel. Therefore, CO2 emission methodology for the new technologies is thesame as that in the 2006 IPCC Guidelines. We refined the guideline to explain
the processes of new technologies to clarify the CO2 emission mechanisms by
new technologies.

232

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36

Revise to - new thermal treatment methods of solid waste (such as gasification andpyrolysis) are not included

Archis Ambulkar

Accepted

Revised as suggested.

233

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37

Revise to - and became important

Archis Ambulkar

Accepted

Revised as suggested.

8506

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39

Really, there are no methan and nitrous oxide emission factors for plasma technology inthis refinement.

Irina Govor

Rejected

The commercially operating plasma plant is quite few worldwidely for treating
solid wastes. Even if there are several plasma plants to treat solid wastes,
information is unavailable for CH4 and N2O emissions from plasma plants aswell their emission factors. Also, in spite of our intensive literature surveys forscientific papers and reports, we cannot find the emission factors of CH4 andN2O from plasma technology. However, we will carry out more extensive
survey to find out the emission factors of CH4 and N2O.

4766

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methane should be CH4, nitrous oxide should be N2O

Kewei Yu

Accepted

Revised as suggested.

Comment ID Volume

Chapter From line

To lineComment

ExpertResponse

Archis Ambulkar

Accepted

Revised as suggested.

Irina Govor

Accepted

Revised as suggested.

Should it be - gases used for energy purpose will be reported from energy sector

Archis Ambulkar

Accepted

Revised as suggested.

41

MSW is referred in Chapter 3 before, does it need to be defined in this chapter again

Archis Ambulkar

Accepted

Revised as suggested.

42

42

Begin sentence with - As per the 2006 IPCC Guidelines “…..Waste incineration is definedasArchis Ambulkar

Accepted

Revised as suggested.

5

46

46

Revises to - defined as a thermochemical reduction process that converts

Archis Ambulkar

Accepted

Revised as suggested.

5

46

46

Revised to - gaseous and liquid

Archis Ambulkar

Accepted

Main point is gas not gaseous product

5

47

47

Revise to - products (mainly containing hydrocarbon components) and solid residue (withhigher carbon contents) at

Archis Ambulkar

Noted

No action has been taken as the existing text can explain clearlyof pyrolysis
definition.
Revised as suggested.

234

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38

Revise to - gasification and plasma technologies

8508

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40

I think it should be better to rewritе this part of the phrase as "whereas gases used forenergy purposes will be reported in the Energy Sector."

235

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40

236

5

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41

237

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Revise to - at high temperatures (above 700℃) or at temperatures above 700℃

Archis Ambulkar

Accepted

242

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Revise to - producer gas, mainly used as fuelArchis Ambulkar

Accepted

Revised as suggested.

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Revise to - light hydrocarbons along with

Archis Ambulkar

Accepted

Revised as suggested.

244

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Revise to - gasification, and plasma methods have been

Archis Ambulkar

Accepted

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Revise to - While these new technologies have been mostly applied to recoverArchis Ambulkar

Accepted withmodification

The new technologies have been mostly applied to

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Revise to - plastics, they are also used to treat theArchis Ambulkar

Accepted withmodification

while --> whereas they are used

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These phrases a little bit confused - many or few facilities really have been operated?

Irina Govor

Accepted withmodification

Many plants have been closed.

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Revise to - have been installed to treat wastes, only a few facilities are operational

Archis Ambulkar

Accepted

Revised as suggested.

248

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Revise to - Rising environmental standards and clean energy demands have recently

Archis Ambulkar

Accepted

Revised as suggested.

249

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Revise to - and new plants are getting installed in the developed countries

Archis Ambulkar

Accepted

Revised as suggested.

250

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Revise to - plasma systems for waste treatment without energy

Archis Ambulkar

Accepted

Revised as suggested.

251

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Revise to - emissions from such technologies with energy recovery

Archis Ambulkar

Accepted

Revised as suggested.

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Elaborate term AFOLU

Archis Ambulkar

Accepted

Revised as suggested.

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Revise to - When gas products of the three processes are

Archis Ambulkar

Accepted

Change to 'when gas, liquid, and solid products of the three processes'.

254

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Revise to - Methodology from the 2006 IPCC Guidelines

Archis Ambulkar

Accepted

Revised as suggested.

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Section 5.3.2. The following text could be inserted: as regards N crop residues openburned a cross check with the amount of NbeddingMS of the Equation 10.41 Managed
manure N available for application to managed soils and the categories "Crop residue N,
including N-fixing crops and forage/ pasture renewal, returned to soils, (FCR)" (includedin the 3D CRF category - volume 11 chapter 11 section 11.2.1.3) and "Field Burning ofAgricultural Residues" (3F CRF category - volume 4 chapter 5 section 5.2.4 Non-CO2
greenhouse gas emissions from biomass burning), relative to the amount of agriculturalresidues that is open-burned other than the amount of agricultural residues that is removed
for other purposes (e.g. bedding) or returned to soils or burnt on-site should be done. Seebox reported in Crop residues (see comment above regarding crop residues). This isimportant to eliminate the possibility of double counting.

Eleonora Di Cristofaro

Accepted withmodification

Revised as suggested.

The 2006 IPCC Guidelines of the Waste sector provide non-CO2 GHGs (CH4
and N2O) emission factors from open burning of solid wastes only. Since nonCO2 GHGs (CH4 and N2O) emissions from the open burning of agriculture
residues are only reported under Agriculture sector, there is no double counting
issue. We refined the guideline to clearify the non-CO2 GHGs emissions fromopen burning of solid wastes only not including those from the open burning of
the crop residues.

Comment ID Volume

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ExpertResponse

Authors note

It is known that uncontrolled burning of domestic waste is a common activity in many
developing regions, and many cities do not have the facilities to carry out adequate
collection and treatment of urban solid waste, so it is recommended that IPCC provides
more guidance on estimating those emissions.

Mingming Wang

Accepted withmodification

A chamber method has been applied to estimate the GHG emissions from theopen burning of solid wastes and crop residues. The chamber method is to
artificially install a chamber where open burning of solid wastes and crop
residues are simulated and flue gases are collected for gas analyses. However,the chamber method estimating GHG emissions from open burning are at a
research state. There is no standard method for estimating flue gas emissions aswell as GHG emissions. It is early to offer the estimation method of GHG
emission from open burning. However, in the 2019 Refinement, we may
introduce the chamber method briefly with some references.

91

Revise to - factors for open burning

Archis Ambulkar

Accepted

92

Revise to - from experiments in Japan

Archis Ambulkar

Accepted

Revised as suggested

92

93

Sentence not clear - The condition of combustion is smouldering combustion with the
moisture content is 35 percent.

Archis Ambulkar

Accepted

Revised as suggested

93

93Change to - In Table 5.2 below, except

Archis Ambulkar

Accepted

Revised as suggested

General comment: There will not be any updates to Table 6.5? Some of the values in thetable are close to 20 years old which would motivate an update.

Klara Westling

Rejected

No action can be taken because comment is out of scope of 2019 Refinement.

Generally, It is better to indicate data sources or justifications supporting expert judgementfor defaoult EFs and parameters (on the update table 6.3, 6.8,6.12,6.14 etc.), if possible.

Takefumi Oda

Accepted

The text has been updated to include the citations for the emission factors
presented. In addition, where appropriate, annexes are presented to provide
further details.

A general remark on the methodology for centralised treatment of waste water: This
remark will be made more specific for parts of the draft, where it is relevant. Methane
emissions from waste water treatment plants are generally low. When most waste water istreated at centralised plants, the subsector will be a non key category source in a specificcountry. I think you should keep this in mind, when drafting the guidelines. The methodshould give guidance for countries without any statistics on water treatment (here TOW
for the treatment pathways still needs to be estimated), and countries where statistics areavailable of amount of TOW/N treated or sludge produced. The chapter needs to give
guidance for all situations and this might call for a tiered approach. In any case, thecomplexicity must match the importance of the subsector and when it is of minor
importance, you can not request countries to perform major additional inventories togather relevant activity data. (i) A Tier-1 (or Tier 1A) methodology might simply describe
emissions from WWTP as a function of the amount of TOW treated in waste water
treatment systems, so CH4wwtp = EFwwtp*TOWwwtp (in the Netherlands we use a CSmethod in which is assumed, that 0,085 g of methane is produced per kg COD in theinfluent of WWTP, irrespective of way waste water/sludge is treated, see Oonk et al. 2004
which is added. I don't want to suggest to use this EF, because there is sufficient
information available to improve on this. However I want to suggest the development of a
Tier-1 method with the simplicity of this Dutch approach). (ii) A Tier-2 methodology
might be used, e.g. when countries have detailed information available (for example,
amount TOW/N treated in different types of WWTP, amount of sludge produced andtreated in aerobic systems and digesters). In this Tier-2 (Tier 1B) method a method might
be used, in line with your draft: emissions from the water ponds and sludge treatment canbe quantified separately and different types of waste water treatment/sludge treatment
might be distinguished. However, when I read the PhD-thesis of Daelmans, it appears themost methane that is emitted from the water line, is already generated in the sewer system,
enters the WWTP with the influent and is subsequently released as a gas. So it is not
generated in the water ponds and if this is true, the nature of the WWTP (managed, notwell managed, simple, advanced, overloaded during parts of the year) has not that much
impact on methane emissions. The only thing having significant impact is, whether sludge
is treated in an anaerobic digester. So a Tier 1B method makes also sense to me, in which
the amount of TOW in the influent is used as an AD, and is quantified for e.g. 3 different
types of WWTP: (i) aerobic WWTP with sludge treatment, other than AD; (ii) aerobic
WWTP with AD of sludge; (iii) anaerobic treatment of waste water. In such a method
seperate overall MCFs can be quantified, based on available measurements.

Hans Oonk

Accepted withmodification

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Revised as suggested

The existing 2006 Guidelines already provides a tiered approach for estimationof CH4 emissions, which we are not proposing to change. This tiered approachalready requires the collection of data on the share of wastewater treatment ineach pathway, and provides suggested values for the degree of utilisation oftreatment and discharge pathways in Table 6.5. These values should be replacedby national values if they are available.
We agree that the majority of emissions from the water line of the centralised
treatment plants originates from the upstream collection system. We havetherefore introduced an emission faction for these systems regardless ofwhether they are "well managed" or not. We have also clarified that systems
that are not well managed will have fewer organics removed during treatment,
which will affect the value of Smass in Equations 6.3B and 6.3C.
We also agree that anaerobic digestion of sludge generates significant CH4 inthe biogas; however, if the biogas is recovered and flared or upgraded, theemissions can be very small.

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A second general comment: the IPCC guidelines intend to improve the quality of theemission inventories and provide a basis for review. Quality is defined as ACCCT andcomparability of the methodologies used between countries is important. I think it isimportant to have no 'open ends' in the methodology, at least not in a Tier-1, and as few as
possible in a Tier-2. Open ends are for example EF/MCFs, that remain undefined (e.g.
MCF when a waste water treatment plant is overloaded for part of the season). Open ends
will cause problems upon emission inventory and review. Countries are forced to perform
R&D and reviewers will need to evaluate, whether results are acceptable, so open ends
create a lot of work in the process. Without clear descriptions how to fill in blanks (e.g.
specifying what type of measurements) the 2019 refinement will damage comparability
between parties. Please be aware that the IPCC Guidelines does not necessarily requires
full agreement of the scientific community to make certain choices. When information islacking, IPCC is authorised to make an educated guess. For example, in solid waste
deposition, methane oxidation is important. Methane oxidation is very difficult to measure
and little or no reliable information is available on oxidation. Therefore a value of 0.1 was
proposed for managed and covered landfills. Everyone agrees that this value is not correct,
but this value is not really at discussion, because of its strength in making inventories
comparable.

Hans Oonk

Accepted withmodification

Authors note

2570

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1004

Hans Oonk

Rejected

We have not suggested to use conservative assumptions anywhere in the 2019
Guidelines refinement. NB. The 2006 Guidelines does state that the approachto estimating N2O emissions from wastewater effluent disposal is conservative
where data on sludge removal are not available (section 6.3.4 ).

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A third general comment: sometimes the draft suggests, that countries have to demonstrate
good practice, otherwise a higher emissions need to be calculate (conservative approach). I
think this is in contradiction with the 2006 guidelines, where Accuracy (one of the
TCCCA-criteria) is defined as follows (2006 GL, Volume 1, Chapter 1, page 1.8): 'Thenational greenhouse gas inventory contains neither over- nor under-estimates so far as canbe judged. This means making all endeavours to remove bias from the inventory
estimates.' So a Tier 1 method should be free of bias, compared to a Tier 2 or higher. Anysuggestion to use of conservative assumptions in a Tier 1 is in contradiction with'Accuracy'.
General comment no 4: In a number of paragraphs throughout the draft, you explain
methane emissions from supersaturation of water. I suggest you to look critically at theseparagraphs. I have a few problems with this: (i) the text should explain relevant processes
to non-experts. However nowhere in the draft it is explained why supersaturation isrelevant for methane emissions from water treatment. So I am afraid the draft will generate
more questions, than it answers; (ii) supersaturation of water is suggested to be the causeof emissions. This is not entirely true. The cause of methane emissions is methanogenesis
of TOW. To enable diffusion of methane to the atmosphere, concentrations of dissolved
methane in water increase. So increased methane concentrations/supersaturated
concentrations are a symptom, but not the primary cause of emissions. It is when someone
has the flu and feels sick because of high fever. The flu is the real cause of the sickness
and the fever is just one of the symptoms and at best a secondary cause of not feeling well.
(iii) Supersaturation and subsequent diffusion is just one of the mechanisms through whicha system releases its methane. Deemer et al. (2016, in your reference list, Figure 1)
indicate that methane emissions occur through diffusion and ebubbulation, withebubbulation becoming the dominant mechanism, when emissions rates are high. I will
repeat this comment, whenever considered necessary.

Hans Oonk

Accepted withmodification

Methane concentration and supersaturation % is relevant to CH4 water-to-airtransfer and emissions in wastewater processes, as it governs the driving force
and water-to-air mass transfer processes (during aeration or in static systems).
The reviewer comment about "the cause of methane emissions ismethanogenesis of TOW" is also not entirely true, as this is also only part of thefull story of generation plus flux/emission. Supersaturated conditions occur
when the rate of methanogenesis in the liquid exceeds the rate at which themethane is oxidised and/or transferred to the gas phase, so flux processes arewhat drive emissions, which includes dissolved (supersaturation) concentration.
The higher the percent supersaturation, the higher the mass transfer coefficient
will be and the greater the driving force and rate of water-to-air CH4 transfer
and subsequent emission. Bubble evolution (ebullition) is more of aphenomenon of importance for anaerobic processes and so is not relevant toCH4 transfer/flux in water line processes; it is more relevant to processes likeanaerobic wastewater treatment/sludge lagoons. We have added the following
new sentence on Line 304 after existing text "...Castro-Morales et al, 2014)."
NEW TEXT: "Supersaturated conditions occur when the rate ofmethanogenesis exceeds the rate at which the CH4 is oxidised and/ortransferred to the atmosphere, and is important as it governs the driving force(mass transfer coefficient) and likely water-to-air CH4 emission from a
receiving environment."

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128

For sludge stream, there is possibly a case of sludge disposal into aquatic environment. It
should be described in the figure 6.1.
Considering decomposition process, this stream, specifically ocean disposal of sewage
sludge, should be reported in the category wastewater discharge, not in the category
SWDS.

Takefumi Oda

Accepted

The text and Figure 6.1 have been adjusted to specifically discuss ocean
disposal of sewage sludge from the wastewater treatment plant.

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Figure 6.1 only provides two types of treatment of sludge, which is not aligned with thesludge pathway given in Box 2.1A of Volume 2. Please clarify and consider making
reference to the pathway given in Box 2.1A.

Mingming Wang

Accepted

Figure 6.1 has been adjusted to align with Box 2.1A.

See response to comment 2566.

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9436

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To lineComment

ExpertResponse

129"Sludge energy recovery" should be replaced with "thermal reduction". Incineration is aform of "thermal reduction". Little energy is recovered from the thermal reduction ofprimary plus biological sludge; supplemental energy must be added for sludge that has
undergone anaerobic digestion. We normally reserve the term "energy recovery" forprocesses like anaerobic digestion that produce a form of energy (e.g. biogas, syngas).
That which remains after digestion may go to land or thermal destruction. Some solids goto land or another industry without energy recovery (e.g. treated with lime, composted,and dried).
Table 6.1, item Sewers (close and under ground): COMMENT: There is now enough datato conclude that close sewers will produce methane. In my opinion, the sentence"However, little data exist to quantify" should be deleted. To support this, I am quoting aparagraph of a manuscript of my main authorship that will be submitted shortly: "Several
field studies (Guisasola et al., 2008; Foley et al., 2009; Willis et al., 2012; Chaosakul etal., 2014; Eijo-Rio et al., 2015; Liu et al., 2015; Short et al. 2017) have demonstrated thatthe assumption in the IPCC Guidelines about closed underground sewers not being asource of CH4 is not supported. Assessing the contribution of sewer systems to methane
emissions, Guisasola et al. (2008) measured dissolved methane in two sewers (rising
mains) in the Gold Coast (Queensland, Australia), finding a wide range of values (4.8 and
30 mg/L). In the same area, Foley et al. (2009) determined dissolved methane
concentrations of 1.0 – 1.9 mg/L for fresh sewage and up to 9 mg/l after a 1.9 km longrising mains. Later, Liu et al. (2015), also in the Gold Coast, observed that the dataobtained in a rising main showed a variation in dissolved methane concentration: 5 - 15
mg/L in summer and 3.5 - 12 mg/L in winter. In Georgia (USA), Willis et al. (2012) founddissolved methane in a rising mains discharge manhole between 1.5 to 9 mg/L in summer.
Additional data for lower concentrations of dissolved methane entering WWTP areprovided by Eijo-Rio et al. (2015), who measured a summer average of 0.150 mgCH4/L(0.046 – 0.249) and 0.032 mg/L in winter (0.019 –0.056) in Catalonia (Spain). For a
facility in Galicia (Spain), the values for summer were 0.193 mg/L (0.137 – 0.271) andwinter 0.081 mg/L (0.008 – 0.258). With the same purpose, Short et al. (2017) sampled
dissolved CH4 in the influent of three large WWTP in New South Wales (Australia)
served by gravity sewers. The CH4 concentration detected (around 1 mg/L) allowed toconclude that gravity sewers have 10 to 20 fold lower dissolved CH4 than pressurized
sewers (rising mains) in that country. In contrast, a gravity sewer in a peri-urban village in
Thailand reached higher values, depending on the season. For the dry period, Chaosakul etal. (2014) measured an average of 10.1 mgCH4/L (7.6 - 13.1) for a sewage temperature of
33°C, while for the wet period the average was 4.6 mg/L (0.0 – 11.4) and 30°C."

Patrick Coleman

Accepted withmodification

Figure 6.1 has been adjusted to reflect biogas recovery associated withanaerobic digestion of sludge.

Authors note

Adalberto Noyola

Accepted withmodification

We agree that there are sufficient data to conclude that CH4 is produced withinsewer collection systems, which has been reflected in the refinements made to
the description in Table 6.1. However, we disagree with the comment
questioning the phrase "However, little data exist to quantify." While there area lot of data now to support estimations of CH4 production (and less often
emission) from sewers, there is still no clear consensus on how to estimate theseemissions for large municipal sewer networks (e.g., work has been done on
invividual rising/trunk mains or sewer segments, but not integrated acrossnetworks including differrent pipe configurations, area/volume ratios,surcharge/flow rates, pump station operations, etc). Nobody has characterised
CH4 mass transfer coefficients for the different sewer types and operational
conditions and there are a lot of variables which will ultimately affect emission
rates (CH4 production rates are much better characterised).

Table 6.1, item Centralized aerobic wastewater treatment plants. The line "…due toreduced removal of organics in sludge" in may opinion is confusing. Maybe it should bechange to "…due to organic overload or low dissolved oxygen concentration in aerobictank"Adalberto Noyola

Accepted withmodification

The description in Table 6.1 has been revised to address reduced removal oforganics in primary treatment.

Table 6.1, item Sludge anaerobic treatment in centralized aerobic wastwater treatment
plant. In these systems methane will be emitted in all cases, even if it is "recovered andflared". Fugitive and unintended methane emissions take place in the sludge treatment
facilities, even if well managed. In my opinion, the sentence could be rewritten as: "Sludge
digestion and handling may be a source of fugitive CH4, even if produced CH4 isrecovered and flared". To support this, I am quoting a paragraph of a manuscript of mymain authorship that will be submitted shortly: "However, fugitive (unintended) emissionsof CH4 may be produced as leaks in the anaerobic digesters due to inefficiencies in biogas
capture and flaring systems. It has been reported that these fugitive emissions represent
between 2 to 10 % of the total methane emissions and a loss of potential energy and heat
(Flesch et al., 2011; Dumont et al., 2013; Yoshida et al., 2014b). Higher leakage values
may be encountered resulting in many cases due to poor operation and maintenancepractices (Yoshida et al., 2014b)."

Adalberto Noyola

Accepted withmodification

The description in Table 6.1 has been revised to address fugitive emissions
from sludge treatment and handling.

Comment ID Volume

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Comment

ExpertResponse

Table 6.1, item Anaerobic lagoons. The word "Likely" should be deleted. It should bechanged to "Significant". As mentioned in the text, it would be an inconsistency with thegiven MCF in table 6.3 for this same system.

Adalberto Noyola

Accepted withmodification

131

Nitrification and denitrification plant, by definition, do not include an anaerobic zone.
Denitrification occurs in a zone where aerobic or facultative organisms oxidize nitrogen(e.g. nitrite, nitrate) in the absence of free oxygen (i.e. O2). The oxidized nitrogen is theelectron acceptor in the absence of free oxygen. These plants are not a source of methane
because the oxidation reduction potential does not drop low enough. There are processes
with anaerobic steps including biological phosphorus removal, UASB reactors and somelagoon plants.

Patrick Coleman

Rejected

There are some anaerobic zones even in a denitrification process. So, a plantwith nutrient removal (nitrification and denitrification) could be a source of
CH4 and N2O. In addition, we have revised the MCFs presented for centralised
treatment systems and only provide one factor for all aerobic treatment systems.
These systems may produce limited CH4 from anaerobic pockets, but are more
likely to liberate CH4 generated in upstream sewer networks during turbulent
and/or aerobic treatment processes.

130

131

There is a form of lagoon referred to as facultative. In these lagoons, which are shallow,
the algae and air movement create an aerated layer and the bottom is anaerobic layer.
These lagoons are not a significant source of methane.

Patrick Coleman

Rejected

As described by the commenter, facultative lagoons contain an aerobic surface
layer over an anaerobic layer. The oxygen needed for aerobic treatment isprovided primarily by algae and therefore, the depth of the aerobic surface layer
is constantly in flux and affected by meterological changes. These systems are
considered primarily an anaerobic system, and the aerobic surface layer can turnanoxic or anaerobic during some periods, notably at night when photosynthesis
ceases. Methane emissions from these systems have been documented inseveral countries, including the USA, Australia, and Brazil. Therefore, we haveclarified in Table 6.1 and 6.3 that facultative lagoons can be a source of
methane.

6

130

131

Advanced plants with nutrient removal (nitrification and denitrification) are considered assources of Methan and N2O. For N2O a lot of literature is available which underlines this.
However, in respect of methane, the number of literature is much smaller, probably tosmall.

Christoph Lampert

Accepted withmodification

We agree that advanced plants are a source of both N2O and CH4. We also
agree that the amount of research on CH4 is smaller compared to the researchon N2O, but we disagree that it is insufficient to conclude that there are
emissions occurring from centralised aerobic treatment systems. However, wehave revised the CH4 factors to provide one value for all centralised aerobic
treatment systems because the majority of these emissions are in fact from
dissolved CH4 entering the treatment plant after being formed within upstream
sewer collection systems.

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Patrick Coleman

Accepted

The Introduction was intended to be an amendment to the the existing
Introduction in the 2006 Guidelines. This section has been revised to to create amore complete discussion for the reader. In addition, terminology has beenreviewed for consistency.

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219

This section is confusing, particularly to a non-wastewater professional. For the purpose ofthis document, wastewater plants are designed to remove biologically degradable material.
Some of this material is settled out (e.g. primary treatment) and some is oxidized to carbon
dioxide and bacterial mass (secondary treatment). Some plants oxidize ammonia(nitrification) to oxidized nitrogen (e.g. nitrate, nitrite). Some plants utilize the oxidized
nitrogen as a replacement for oxygen reducing oxidized nitrogen to a gaseous form
(denitrification).
The secondary process requires the system to retain biomass in the system. This may be
accomplished by a large basin, by growing biomass on media retained in the system (e.g.
biological filters) or separation and return (e.g. settling tanks, membranes, and dissolved
air flotation).
If this part is intended to be an introduction to methane and nitrous oxide emissions fromwaste water treatment and discharge, be sure it is complete. Table 6.1 gives an overview ofthe subsector and you might use this table to check whether your description is complete
and covers all major sources in a similar way. E.g. methane generation in sewers are
mentioned in table 6.1 but not in the text. Constructed wetlands are mentioned in the text,
but not in the table. Lagoons are briefly mentioned in the first sentence, but are notexplained further. The paragraph on direct discharge only focusses on the effect ofnutrients in the receiving waste body on emissions. Please make sure your terminology is
consistent throughout the chapter (e.g., in the table 6.1 you use the word 'collected'. In the
text 'centralised'. This might be obvious to you and me, but users might get confused andnot understand that you use these words as synonyms).

Hans Oonk

AcceptedSee response to 7530.

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2574

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The description in Table 6.1 has been revised to address fugitive emissions
from sludge treatment and handling.

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Authors note

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In the 2006 guidelines, sewers are mentioned to be no source of methane. This is not true.
There is plenty of anecdotal evidence that methane can be produced in closed undergroundsewers. Just check youtube and search for 'sewer explosion" and you will find many
examples. Daelmans in his PhD-thesis describes that methane dissolved in the influent of a
WWTP is a major source of methane, emitted from a WWTP. Only a fraction of methane
generated in the sewer might be dissolved in the water phase, and large part of the methanemight be released in a diffuse way. Guisasola et al. (water reserch, 2008, vol 42, pp. 14211430), measured methane formation in Australian sewer systems. They estimated thatabout 100 mg/l COD is lost,of which 70% is removed anaerobically and produces
methane. Emissions from closed sewers are a significant unknown in emissions from waste
water treatment and discharge and especially at high (from a Dutch perspective) ambient
temperatures might be a significant, yet neglected source of methane. Closed undergroud
sewers are briefly mentioned in table 6.1, I propose you describe this as an importantunknown in your introduction, e.g. under centralized treatment systems.

Hans Oonk

Accepted withmodification

See response to 9436. In addition, the Introduction text has been expanded tomore fully describe the potential for emissions associated with sewers.

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142

Add "and/" fefore "or"Delphine Groupe de travail
GES - Astee répésenté par
VALENTIN

Accepted

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147

The term “anoxic” should be defined. The dictionary definition implies the absence ordeficiency of oxygen. This is not the case in wastewater treatment. The definition iswastewater treatment is a zone where there is no free oxygen but there is oxidized nitrogen(i.e. aNOxic or anoxic). The definition of an anaerobic condition is the absence of all
forms of oxygen.

Patrick Coleman

Accepted

Text has been augmented to specify that denitrification occurs in a zone where
aerobic or facultative organisms oxidize nitrogen (e.g., nitrite, nitrate) in theabsence of free oxygen (i.e., O2).

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151

upload of the document was not possible ("Wrong Access")

Christoph Lampert

Noted

No action can be taken because comment is out of scope of 2019 Refinement.

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There is also literature showing, that the major part of N2O-emissions stems from thedenitrification step - the literature enclosed includes a broad overview on N2O emissions
from sewage treatment plants.

Christoph Lampert

Accepted

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The year of the cited reference should be 2010

Adalberto Noyola

Accepted

7534

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151

Error in the year for Ahn et al

Patrick Coleman

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153

Remove "plug flow". Indeed in France and other Europen countries, CAS is not only plug Delphine Groupe de travail
GES - Astee répésenté par
flow reactors (mainly used for large WWTP) but also MLE and so on. This "pluf flow"
VALENTIN
specification is not necessary.

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155

This should read "a common example of a centralized system configuration is an activatedsludge treatment system." The term "plug flow" is too specific. There are many batch, step
feed, completely mixed, granular and lagoon activated sludge plants.

Patrick Coleman

Accepted

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156

Further systems could be described using the activated sludge system. Especially the
Sequencing Batch reactor could be described as later on an EF für N2O for this kind ofreactor is provided.

Christoph Lampert

Rejected

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This is too specific. I would delete it. We only use the term "centrate" when are speakingof the water separated by a centrifuge from the sludge feed. We normally use the term"thickening and dewatering reject water" because the term "liquor" does not translate wellinto non-english speaking parts of the world. The last line in this paragraph does not makesense and seems irrelevant.

Patrick Coleman

Accepted withmodification

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155

Remove "plug flow". Same reason than previously

Delphine Groupe de travail
GES - Astee répésenté par
VALENTIN

Accepted

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157

Typically, the clarified effluent is NOT disinfected prior to discharge.

Christoph Lampert

Accepted withmodification

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158

Remove "plug flow". Same reason than previously

Delphine Groupe de travail
GES - Astee répésenté par
VALENTIN

Accepted

Accepted
Accepted

No need to provide further examples.

Language has been revised.

Softened the statement so as not to imply disinfection always occurs.

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Christoph Lampert

Rejected

Methane emissions from aerobic systems reflect the emission of dissolved
methane that was formed in the collection system and emitted in the headworks
or primary treatment stage, as well as other methane that may form within thetreatment system and be emitted. Therefore, inclusion of this source isappropriate as it is not insignificant.

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Adalberto Noyola

Accepted withmodification

Text has been revised to discuss dissolved methane entering the treatment
system and being emitted during aerobic treatment.

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CH4 emissions from well managed centralized aerobic plants may be small, they are notzero. This is probably correct. But are CH4-emisisons really relvant from this kind ofsystems?
Focus should be led on the direct N2O emissions from advanced waste water treatment
plants - the provided emission factor now is 28 to 90 times higher than in the 2006
guideline!
This sentence may be improved with the following: "…….they are not zero, AS CH4
MAY ENTER DISSOLVED IN THE INFLUENT AND THEN EMITTED IN THE
AERATED ZONES OR EVEN PRODUCED IN CERTAIN PARTS OF THE
PROCESS. To support this, I am quoting a paragraph of a manuscript of my main
authorship that will be submitted shortly: the assumption of a CH4-neutral treatment
facility, as established in the IPCC methodology in the case of a well-managed centralized
aerobic treatment plant (IPCC, 2006a) is not supported. The dissolved exogenous CH4entering the WWTP will be desorbed from the aerated grit chamber and the aeration tank,regardless of eventual anaerobic pockets that would produce methane on-site. As theemission point is in the WWTP, it is here that the control measures should be applied; inconsequence, the Tier 1 should consider this emission in the CH4 inventory of thewastewater treatment facilities."
I would delete this paragraph. Most activated sludge plants nitrify if the sewage is warm.
Denitrification is commonly used to reduce the energy consumption of the plant. We
normally reserve the tern “BNR” for plants that denitrify or remove phosphorus
biologically. There are only “anaerobic” zones in plants the remove phosphorus
biologically.

Patrick Coleman

Accepted withmodification

BNR is quite common and typically used as we have outlined in line 172,
therefore this text remains unchanged. However, we have removed the use of
the term "ENR" as on line 172, as it is not commonly used.

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Different systems can show different potentials for CH4 and N2O emissions. But it isuncertain, if enough evidence to derive new EFs will be available.

Christoph Lampert

Rejected

We reconsidered the categories of treatment processes for which new N2O EFs
are presented from that included in the FOD. Sufficient literature exists todevelop new or refined emission factors as specified in this Refinement
document.

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176

The consideration of biological nutrient removal systems is a sound decision. In mymanuscript to be submitted shortly, this is proposed, based on literature data.

Adalberto Noyola

Accepted

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195

Most onsite systems in developed countries are septic tanks followed by a tile field. Moreadvanced systems are only used when the environment or property cannot support a septic
tile field. This is because the tile field requires are large portion of land. The treatment
occurs within the first few feet (meter) of the material surrounding the tiles. The soil
bacteria consume the organic material and oxidize the nitrogen.

Patrick Coleman

Accepted withmodification

The comment is not in contraction with what is currently in the FOD. Anyway,
to increase transparency, the text has been changed to "The treated effluent isdischarged into the environment via surface irrigation or infiltration throughabsorbsion trench."

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Figure 6.1a only provides a range of values for each country, which is not easy to use.
Please also provide exact figures in a table format if possible.

Mingming Wang

Accepted

The data associated with the map published in 2013 by Graham and Polizzoto isincluded as an annex to the chapter.

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The title of the paragraph doesn't reflect the intention of the paragraph. I think in theparagraph you want to express, that the nutrient availability of the receiving water bodyhas impact on emissions. So the title should not be 'Eutrophic waters', but 'Impact ofnutrient availablity'. But it might be even better to make a general paragraph on 'directdischarge', to complement the previous paragraphs on 'centralised' and 'non-centralised'.
Please consider what the message is, you want to convey in the introductory paragraph andmake sure that this is in line with the other paragraphs in the introduction.

Hans Oonk

Accepted withmodification

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2017) ??

Kewei Yu

Accepted

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methane should be CH4

Kewei Yu

Accepted

For consistency, the gas was given its chemical symbol.

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217

The last sentence of the paragraph is methodological guidance. I think this should not begiven in the introduction, but in 6.2.2.2, under 'discharge from treated and untreatedsystems' and under 6.3.1.2.

Hans Oonk

Accepted

We moved the sentence in question.

219

219

The heading has been changed to "Emissions from receiving waters."

The citation has been fixed to include the author names.

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I do not understand why you propose recipient conditions to have impact on N2O, but not
on CH4. In line 210 you explicitly mention the strong correlation between the condition of
aquatic environment and CH4 as well. However you are using the fact that most fresh
waters are supersaturated as an reason not to distinguish between eutrophic andoligotrophic wasters for methane. I can not follow this, so can you please explain?
According to Deemer et al. (2016) there is no clear correlation between methane emissions
and supersaturation of waters, since ebubbulation of methane for deposits on the waterbottom is the prevailing mechanism for emissions. So based on the conclusion that all
surface waters are supersaturated, you can not conclude that the MCF of all surface waters
are similar. When the condition of the receiving water is important, my question is whether
the default MCF of 0.27 refers to eutrophic waters, oligotrophic waters or some global
average. Please note that the guidelines should be 'accurate' as much as possible, so neither
leading to an over- nor underestimation. Assuming worst-case should not be part of aguideline.

Hans Oonk

Accepted withmodification

The reviewer makes a good point about the data on relative methane and carbon
dioxide emissions having a basis in reservoir measurements. Diffusive andebullitive methane emissions are indeed strongly related to sedimentaccumulation, as indicated by table 1 in Deemer et al 2016. For ease of tier 1
method operation, we therefore changed the approach here, to using one figure
for rivers and another for reservoirs and estuaries (where sedimentaccumulation is more typically relevant). We used the data from table 1 inDeemer to calculate the relative yield figures, but replaced the 1800 Tg/y figure
which Deemer took from Raymond et al (2013) with the 650 Tg figure from amore recent review (Lauerwald et al, 2015).

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It is unclear from the text in Volume 5, Chapter 6, whether the emissions estimates fromequation 6.1A refer to the CH4 produced from the BOD (or COD) entering a treatment
system/pathway, or whether it refers to the CH4 produced from the BOD (or COD)
decomposed (removed) in a treatment system/pathway. This distinction becomes
particularly important when considering emissions from treated wastewater entering awaterbody.
From the discussion on the origin of B0 (Annex 6A.1, lines 752-772), it is clear that B0
was derived from the potential methane produced with complete decomposition(oxidation) of glucose. However, in Volume 5, Chapter 6 the emissions calculations
appear to be based on BOD (or COD) entering, or “in” a treatment system rather than thedecomposition of BOD (or COD) in that system. For example, Equation 6.1 and 6.1A
define TOW as the organics in wastewater of treatment/discharge pathway or system,
which can be interpreted as the organics entering the system, rather than the organics being
removed via the treatment system.
I would recommend that the text and equation 6.1A be adjusted to reflect that emissions
are estimated from the organics (BOD or COD) removed via a treatment system/discharge
pathway, rather than the organics “in” a pathway.
In general, wastewater treatment systems do not remove (decompose / oxidize) all of the
BOD entering the treatment system. Some of the BOD remains in the effluent and isdischarged to water bodies. Distinguishing the BOD (or COD) removed via treatment
from the BOD remaining in effluent discharged to water bodies is important to avoid
double counting emissions when the emissions from treated wastewater discharged to awater body are estimated as discussed in lines 291 to 303.
To avoid double counting emissions from decomposition of organics in treated wastewater
discharged to a water body, the emissions from the treatment system should only consider
the organics removed (decomposed) in that system. The remaining BOD should then be
estimated as the organics discharged to natural water bodies.
I would suggest clarifying Equation 6.1A to be, either:
Option A (new text underlined):
Lines 264-655: TOW = organics in wastewater removed via treatment system/pathway j,or the organics in wastewater discharged to a water body, for each income group fraction iin inventory year kg BOD/yr.
Line 269: j = each treatment/discharge pathway or step within a multi-step system,
including the good practice of including discharge of treated or untreated wastewater to awater body.
Line 270: EFj = emission factor for treatment/discharge pathway or system or treatment
step within a multi-step system, j, kg CH4 / kg BOD removed
Option B (lines 259 to 272 new or changed equation parameters presented only. Note thisis similar to the approach used in Australia’s 2017 National Greenhouse Gas Accounts

Emil Laurin

Rejected

Emissions are estimated from the total organics in wastewater (TOW)(expressed as either BOD or COD) entering a pathway, reduced by the amountof organics removed as sludge (S) in that treatment pathway. The degree towhich the entering TOW is removed by conversion to methane is expressed by
the MCF.
The proposed changes to Equation 6.1A to calculate methane emissions reflect
a different and more complex approach for emission estimation and would
require a complete redesign of the wastewater chapter and the MCFs presented.
If the equation were to be altered to apply the emission factor (i.e., Bo X MCF)
to the amount of organics in wastewater after treatment (and after the emissions
occurred), the MCF would need to be redefined accordingly. In other words,
the current approach to estimating the methane emissions uses the TOWin
reduced by the amount removed in sludge, and an MCF which has been defined
based on this type of calculation. Changing the calculation to (TOWin TOWsludge - TOW out - TOW gas) would require the MCFs to be redefinedon the lower basis of organics, resulting in higher MCFs.
We agree that not all TOW is removed in a treatment or pathway and that theremaining TOW discharged should be calculated to estimate emissions
associated with discharge.

Comment ID Volume

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Authors note

Rejected

BOD reflects the biologically oxidisable fraction of total organic content and so
is preferable to COD in the context of CH4 emissions, since COD includes bothlabile and recalcitrant organic fractions which may not undergo biologicaldegradation. In addition, factors are provided to relate BOD to COD if that isbetter for them to do the calculations.

(Section 7.6.2 Domestic wastewater (5.D.1) methodology)
Equation 6.1Aa: CH4 emissions = SUM(TOWij – Sij – OWout,ij) *EFj - Rij,
Where, TOWij = organics in wastewater entering a treatment system pathway…
OWout = organic in wastewater effluent leaving the treatment system/discharge pathway j,for each income group fraction for each income group fraction i in inventory year, kg
BOD/yr.
Possible a default values for OWout could be something like 50 % of TOW for primary
treatment, 15% of TOW for secondary treatment systems and 0 for wastewater entering awater body based on Sonune and Ghate (2004).
Further discussion:
If TOW it is based on the organics decomposed (removed) via the treatment system(pathway), then further guidance on estimating default TOW removal via treatment would
be helpful. For example, defaults based on typical primary and secondary systemefficiencies of ~70% and ~95% BOD removal, or a general ~85% BOD removal
efficiency per Metcalf and Eddy 2001). Default values for organics removal could
compliment default defaults for the remaining organics in the discharge to water bodies
after treatment (as discussed lines 291 to 313). For example emissions from centralized
aerobic treatment pathway are estimated based on the removal of (a figurative estimate of)
85% of the organics entering the system, the emissions from remaining 15% of organics inthe treated effluent are estimated from receiving water body.
Looking at one hypothetical facility for illustrative purposes, for example, a facility
receiving influent wastewater with a BOD5 of 100 mg/L having a total wastewater volumeof 10,000 ML/yr wastewater will receive an annual TOW of 1.0 million kg BOD5/y.
Assuming no sludge removal for simplicity, if the wastewater is treated to an effluent
concentration of 5 mg BOD5/L, the facility would remove (decompose) 0.95 million kg
BOD5/yr. If the wastewater is treated to 30 mg BOD5/L it will only remove (decompose)
0.70 million kg BOD5/yr.
Clearly, the amount of BOD decomposed varies by the level of treatment or regulatory
standards. The facility with the higher level treatment (assuming the same MCF) would
emit more CH4, yet both receive the same TOW. On the other hand, the receiving body ofwater in this example would receive treated discharge with either 0.05 million kg BOD5/yr
or 0.30 million kg BOD5/yr, which, depending on the relative MCF compared to thetreatment system, might be an important difference in overall emissions. Scale this up tonational levels and the differences become more important still.
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General remark for all the equations dedicated to domestic wasteawater: The choice of the Delphine Groupe de travail
BOD was favored over that of COD, why?
GES - Astee répésenté par
VALENTIN

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230

Please be accurate and consistent in terms. In the 2006 guidelines, TOW is defined as'total organics in waste water'. In line 264 in the 2019 draft 'organics in waste water'. In
line 230 'organically degradable carbon'. 'organically degradable' seems incorrect English
to me and means degradable under organic conditions. 'Degradable organic' seems to bebetter English, but I would prefer that you stick with the terms that are defined elsewhere
for TOW.

Hans Oonk

Accepted withmodification

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Many countries don't have accurate statistics on stabilised sludge production (as it leaves
the fence of WWTP). I guess no country will have accurate statistics on a national level ofprimary and secondary sludge production (prior to on-site treatment). Also information on
methane recovery from sludge digesters might not be complete. We will need either asimplified method for countries, without proper information on sludge production andmethane recovery, or you will need to include a recommendation to estimate sludge
production/methane recovery, along with default methods to estimate them, e.g. based on
defaults of sludge production per ton of TOW removed. Maybe the information in line
368-371 is intended to be a basis for such a default. However in such a case I would preferto have the estimation method specified more clearly, e.g. made explicit as an equation. In
order to ensure comparability, this method for estimating sludge generation should also
have one single default value, rather than a range (now in line 370-371 a range is given:"aerobic WWTP without primary treatment ... 1-1.5 kg BOD per kg sludge, depending on
process type. If this is meant as guidance, you will need to give guidance without suchopen ends). My preference however would be a tiered approach with a simple Tier 1
method, simply describing methane emissions from WWTP as a function of TOW in theinfluent (e.g. CH4wwtp = TOWwwtp* EFwwtp) and a Tier 2 method (comparable to thecurrent method), which can be used when sufficient information is available.

Hans Oonk

Accepted withmodification

A new table was included to provide default factors for organics removed insludge from various treatment types.

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In your draft 2019 Refinement you encourage countries to calculate emissions from water
ponds again separately from emissions from on-site sludge treatment. However I missclear guidance how to do this and a default for the quantification of emission from sludge.
You mention that sludge treatment can be treated as a seperate treatment pathway. Does
this mean, that equation 6.1A can be used to calculate emissions from sludge as well? I am
struggling with this. Equation 6.1A describes the calculation of emissions from water
ponds. I think you will need to describe the calculations of emissions from sludge
treatment as equation 6.1B, something like: "CH4-emissions = sum (Sj * EFsludge
treatmentj - R) or "CH4-emissions = sum ((Sj-SSj) * EFsludge treatmentj - R)" in which
SSj is the amount of TOW removed as stabilised sludge from the perimeter of the WWTP.

Hans Oonk

Accepted withmodification

See response to comment 2596.

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The scope of 5D needs to be defined unambiguously, because in the past I did notice thatsome countries report emissions from on-site sludge treatment under 5B and sometimes
5A. In my understanding everything within the perimeter of the WWTP is quantified under
5D and this includes on-site sludge treatment and storage (see also table 6.1, in which thescope is clearly stated). In this paragraph you mention several times 'sludge treatment'. I
propose you make this 'on-site sludge treatment' or 'sludge pretreatment'. Otherwise,
countries might think that emissions due to final treatment of sludge (e.g. landfills) need to
be included as well.

Hans Oonk

Accepted

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If you want countries to quantify emissions from sludge treatment, separately from theemissions from the water ponds, you need to provide guidance for all types of sludge
treatment. If you think sludge treatment, other than anaerobic digesters, results innegligible emissions, this needs to be added to table 6.3. E.g. as "Other sludge treatment
systems: MCF=0". I do think that sludge treatment, other than anaerobic digestion mightalso result in methane emissions, because of anaerobic conditions during storage, pre- andposttreatment.

Hans Oonk

Accepted withmodification

Text updated to reference on-site sludge systems.

See response to comment 2596.

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As mentioned, yes, indeed, there is a serious confussion with the term S when using
equation 6.1, particularly for centralized aerobic treatment plants with anaerobic sludge
digestion. Again, I quote a paragraph of a manuscript of my main authorship that will be
submitted shortly. "Another misleading aspect is the procedure for estimating the CH4
emissions from “anaerobic digester for sludge” using Tier 1, as referred to in table 6.3 ofthose guidelines (a 0.8 default MCF is recommended, with a range between 0.8 and 1.0).
Based on a simple mass balance consideration, the CH4 emissions from this source should
be calculated based on the BOD of the sludge removed (represented by S in equation 6.1
in the IPCC Guidelines) and not using the TOW. As a result, the total CH4 emissions from
centralized, aerobic wastewater treatment facilities with anaerobic digestion for sludge
stabilization should be calculated in a Tier 1 two-step operation, based on equation 6.1 ofthe IPCC guidelines: first, the emissions from wastewater treatment (using the term TOW– S), and then the emissions from sludge treatment with anaerobic digesters (using theterm S, with a removal factor based on the fraction of volatile solids removed in thedigester). A default value for the removal factor would be in an interval of 0.45 and 0.65,
based on the removal efficiencies of anaerobic digesters reported by Metcalf & Eddy
(2003). The guidelines recognize that only few countries may have data on sludge removal(S) and CH4 recovery (R); if no data is available, the default values should be zero,
resulting in a one-step calculation and a serious simplification for aerobic treatment
facilities with anaerobic digesters for sludge stabilization.

Adalberto Noyola

Accepted withmodification

See response to comment 2596. Adjustments have also been made to the text
related to Equation 6.1A.

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In the document it is encouraged, as an example, to calculate the emissions and any CH4
recovery directly associated with the aerobic treatment system as one pathway. Whichaerobic treatment system produces CH4 in such amounts that recovery will be possible?

Christoph Lampert

Accepted

Text changed to reflect that there is no recovery from the aerobic treatment
system pathway (only from the anaerobic sludge digestion pathway).

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Please check is the word is supposed to be "aerobic:"

Patrick Coleman

AcceptedSee response to comment 2786.

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This equation is problematic because it depends on what the EF is based on. If the EF isbased on the total load ot the plant, then the sludge should not be subtracted because therate would already taken into account that some material is removed with the sludge. theEF and activty data must match. Most EFs are based on raw sewage activity data because
the assessment is high level. To use equation 6.1A, you have to do each plant separately.

Patrick Coleman

Accepted withmodification

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This equation seems to be incomplete if waste water is treated: (this is also true for the2006 guideline): In a typical modern waste water treatment plant about 55% of the BOD
ends up in the sludge and 10% is in the discharge. But: about 35% of the TOW is used upby the biomass and leaves the system as CO2 which is not included in the formula.

Christoph Lampert

Rejected

Equation 6.1A represents the same approach as original equation 6.1, but now
stresses the estimation of emissions by wastewater treatment/discharge
pathway. The MCFs, which make up the emission factors, are developed fromexperimantal data which account for sludge removal. Equation 6.1A is intended
to be used the same way as Eq. 6.1 using national level data.
If the inventory compiler chooses and has plant-level activity data available, Eq.
6.1 or 6.1A can also be used to generate plant-level emissions. However, it
should be noted that it would be more appropriate to develop plant-specificemission factors if developing plant-level emission estimates
The EF is estimated as Bo multiplied by the MCF. Bo represents the theoreticalmaximum CH4 that can be liberated from a type of waste, which by definition
includes complete decomposition. The estimation of Bo already includes thefact that a part of the organic load is emitted as CO2 (see annex 6A.1).

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The calculation of emissions from anaerobic digestion as "generation - recovery" is very
inaccurate. I would prefer a calculation of emissions as % of methane potential or EF *TOW or EF*S (comparable to calculation of emissions from anaerobic digestion of solid
waste in chapter 4, table 4.1, where emissions are calculated from the mass of waste
digested and an emission factor per kg waste treated). Emissions will most likely be 0-10
% of total generated methane (see also 2006 IPCC guidlines, volume 5, chapter 4, page4.4). So the difference between generation and recovery is small and therefore error
propagation is very unfavourable. A slight overestimation of generation is amplified andresults in a significant overestimation of emissions. E.g. assume a digester, where actual
generation is 100 kg/hr and measured recovery 98 kg/hr, resulting in actual emissions of 2
kg/hr. When emissions from this digester are quantified, actual generation is not known
and needs to be estimated. When generation is overestimated by 10%, calculated
generation becomes 110 kg/hr and with measured recovery of 89 kg/hr, estimatedemissions are 12 kg/hr. So a 10% overestimation of generation results in 500%
overestimation of emissions. On a national scale methane emissions from digested sludge
is calculated as Smass * Krem * B0 * MCF and the inaccuracy will be much higher than
10%.

Hans Oonk

Accepted withmodification

We have updated the procedure to estimate emissions from anaerobic digestion
by referring to the methodology in Chapter 4.

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261

Emissions from anaerobic digestion are most likely not due to leaks in the digester itself.
Anaerobic digestion of solid waste in extensively studied by Cuhls et al. (2015) and one of
his conclusions is that most methane is generated from post-treatment of digestate andminor emissions can also be expected upon pretreatment. The digester itself is generally
leak-tight. I know anaerobic digesters, working under underpressure, where possible leaks
will result in dilution of the biogas with ambient air, rather than emissions of methane.
Dealman describes something similar in his study of the Kralingseveer WWTP). 72% of
total methane emissions (including inlet and water line) here came from pre and posttreatment unit operations, related to anaerobic digestion: the gravitational thickener, thecentrifuge, the effluent buffer tank, storage of dewatered sludge.

Hans Oonk

Accepted withmodification

Emissions from on-site sludge treatment should be reported as part of the
Wastewater category. These emissions should use the same methodology
reported in Chapters 3, 4, and 5 of the Waste Volume, as appropriate, and thishas been added to Table 6.1 and 6.3 to be more clear. Pre- and post-handling ofsludge were not examined as they were not in scope of the refinement.

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266

S in equation 6.1A needs to be clearly defined. In my interpretation S refers to the primaryand secondary sludge, as removed from the waste water treatment ponds. So it is theamount of sludge produced by the water ponds, which is subsequently pre-treated on-site,
after which it is utilised or disposed of elsewhere. S does not refer to stabilised sludge as itleaves the gate of the WWTP. Does your S refer to sludge removed from primary andsecondary treatment (prior to on-site treatment) or to stabilised sludge, leaving the gate.

Hans Oonk

Accepted withmodification

The factor, S, in Equation 6.1A represents the organic component removed as
sludge in inventory year, in units of kg BOD/yr. This is the same as the factor,
S, presented in the IPCC 2006 guidelines.

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270

Smass in Equation 6.3B represents the mass of raw sludge removed fromsedimentation and activation ponds of a WWT plant, in units of tons/year. Alsoin this equation we have introduced the use of the factor, Krem, which allows theuser to convert the mass of sludge to the mass of organic pollution removed(S).

Should not there be a reference of what used to be Equation 6.2 EF = Bo * MCF?

Patrick Coleman

Rejected

Maybe it wll be clearer if "flared" is added: "amount of CH4 recovered (or flared) from …
……"

Adalberto Noyola

Accepted

We have added a table of Krem values for various categories of sludge,
including stabilised sludge.
The Refinement is to be used as a supplement to the 2006 IPCC Guidelines;
therefore, Equation 6.2 is still valid to be used to calculate the EF.

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I am struggling with my assessment on B0. I am trying to put my thoughts on paper. To
start, I think the current default value for B0 of 0.25 for COD and 0.6 for BOD are toohigh (I will elaborate on this in another comment). At the other hand, when the values of
MCF are based on results of actual emission measurements, the assumption on B0 is not
relevant. An emission measurement results in an EF (e.g. kg methane per kg of COD
treated). The EF is the product of B0*MCF. MCF is calculated, by assuming a value of B0
and an overestimation of B0 is compensated by an underestimation of MCF. Importantconsequence is, that B0 and MCF come in pairs. One should not revise B0 and keep theexisting assumptions on MCF. For example, when measurements show methane emissionsof 0.001 kg methane per kg COD treated, an assumption of B0=0.25 results in an MCF of
0.004. When afterwards B0 is revised (e.g. because of lab-measurements) to 0.125, theyalso need to recalculate MCF, assuming an B0 of 0.125. In this example the MCF fromthe measurement needs to be revised to 0.8, in order to explain the EF as measured. For
this reason I don’t agree with line 283-285. The 2019 refinement should discourage oreven forbid countries to use country specific data for B0, because B0 and MCF aredependent variables. If a country wants to use CS-data for B0, they also need to reevaluate their values of MCF, based on original emission measurements and taking into
account their CS-B0. One more drastic solution would be not to use B0*MCF at all in the2019 refinement, but simply define default EF in Table 6.3, specifying the methane
emissions per kg BOD in the influent (with a footnote that EF should be divided by 2.4,
when COD is used as TOW).

Hans Oonk

Accepted withmodification

We agree that Bo and MCF values must be considered together when revisions
are made to introduce country-specific data, for the reasons explained in thecomment. A modification to the text has been included to encourage inventory
compilers to use country-specific Bo and MCF for the calculation of countryspecific emission factor.
In response to the suggestion to replace the use of Bo x MCF with directemission factors, that effort is beyond the scope of this refinement.

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I think the value of B0 for BOD of 0.6 is too high. Methane potential is calculated fromthe oxygen consumption of a sample, and I agree with the glucose example in appendix
A6.1, that potential methane generation is 25% of oxygen consumption. However we have
two ways to determine oxygen consumption of a sample: chemical and biological. Both ofthem are incomplete as an indicator. Domestic waste water is for a large part excretion andexcretion consists of remaining fiber material from food and bacteriological biomass fromthe intestines. Not all of this is matter biodegradable (food fibers and cell-walls of biomass
are generally very resistent towards biodegradation) and does not contribute to methane
generation. A COD analysis determines all organic matter (whether it is biodegradable ornot) in the influent. Assuming a B0 of 0.25 for COD implies that all COD will bebiologically degrade under anaerobic conditions. This is not true (fibers won't biodegrade,
bacteria are resistent against biodegradation) and this will result in an overestimation of
actual emissions. Without having made a full overview, I point out to you an article byZhang et al. (Chemical Engineering Journal, 2018, vol. 334, pp 2088-2097), whocharacterised the biological methane potential of domestic waste water and found out thatin a 30 day lab-test only 50% of total COD is anaerobically removed and is therefore asource of methane. This results in a B0 of 0.125 for COD in this domestic waste water.
Since the composition of COD (degradable, non degradable) varies, B0 of COD is also
not a constant and depends on the source of waste water (also illustrated by your new table
6.2A - line 428). When the waste water contains more simple hydrocarbons (as is the casein waste water from many food industries), B0 of COD will be closer to the theoreticalmaximum of 0.25. Alternative for a COD-analysis is a BOD-analysis, which will be more
selective towards biodegradable material. When in a BOD-test all biodegradable material
would be measured, B0 of BOD would be 0.25. However a BOD-analysis is normally cut
off after 5 days, and there is a chance that after 5 days part of the methane potential in asample is not yet biologically oxidised, so the 0.25 might be a slight underestimation of B0
for BOD. Appendix 6A.1 is correct that when all COD would be biodegradable glucose,
B0 of COD would be 0.25. However when all COD would be glucose, BOD of the sample
would be almost equal to COD and the COD/BOD-ratio would be close to 1. B0 of BOD
would be calculated for this sample as 0.25*COD/BOD ~ 0.25. In the 2000 GPG and the2006 GL, a maximum value of B0 for COD (0.25) is multiplied by an average value of
COD/BOD (2.4), yielding B0=0.6 for BOD. This is where things go wrong. For
calculation of B0 for BOD you either multiply a maximum value of B0 of COD (0.25)
with a minimum value of COD/BOD (~1.2) or you need to multiply an average B0 of
COD (0.125) with an average value of COD/BOD (2.4). In both cases, B0 for BOD in
domestic waste water will be about 0.25-0.3.

Hans Oonk

Rejected

Although one might argue there is an overestimation of the maximum methane
generation capcitity (Bo in kg CH4/BOD) of wastewater, the emission factors
used are the product of (Bo)x(MCF) and the values of MCF are based on resultsof actual emission measurements and the default value of Bo. Therefore, anychange to the Bo value would trigger a need to reevaluate the default MCFs as
well.

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Kewei Yu

Accepted

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For me it is unclear what guidance this paragraph tends to give for treated waste water.
Please add an explicit conclusion and also make sure that the methodology, as expressedin eq. 6.1-6.3 is in line with this conclusion. Are you suggesting, that remaining TOW in
the effluent of a waste water treatment plant needs to be considered as a source of
methane, even when the accepting water body into which the effluent is discharged isoxic? If this is your intention, you need to express this in a more explicit way, e.g. byadding an equation 6.3D, indicating that TOW_discharged in open water = TOW_directdischarged + TOW_in effluent WWTP. And since not all countries with WWTP havesufficient data to quantify TOW_in effluent WWTP, you will have to hand them a Tier-1
methodology to assess this, e.g. by defining a default TOW-removal of a WWTP.

Hans Oonk

Accepted withmodification

Revisions were made to the text and equations to provide clarity to thecalculation of emissions from discharge of treated wastewater.

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It seems you want to justify that also under oxic conditions, part of the TOW will be
converted to methane, since (i) Tang (2017) showed that methanogenesis is feasible underoxic conditions and (ii) surface waters tend to be supersaturated therefore a flux will existof methane from the water to the atmosphere. However, there is also vast evidence thatoxygen significantly inhibits methanogenesis. Just search google scholar for"methanogenesis oxygen sensitivity". My reaction to (i) is that methanognesis may still bepossible onder oxic conditions, but it will be significantly reduced, compared to anaerobic
conditions. And under oxic conditions, there are efficient aerobic mechanisms, competingwith methanogenesis, e.g. aerobic microbial degradation or direct consumption by higher
aquatic life forms (e.g. water fleas). So the MCF in oxic waters will be significantly less,compared to anoxic or anaerobic waters. This can also be read in Smith et al. (2017), who
mention in chapter 3.4 that redox conditions modulate CH4-production. Both Smith et al.
(2017) and Tranvik (2009) mention that methane is mostly generated from deposits on thewater-bottem, where conditions become anaerobic. When well-permitted, the receiving
water body of the effluent of a WWTP will remain oxic. Due to inhibited methanogenesis
and existence of effective aerobic removal mechanisms, you can not simply extrapolate
your proposed MCF of 0.27 to discharge of effluent of WWTP (again I am not surewhether this is the intention of this paragraph, since it is not explicitly concluded). My
reaction to (ii) is that supersaturation of surface waters tend is an indication that the waterphase is a source of methane. Surface waters are a known natural source of methane,because of rotting terrestial and aquatic sediments in the water. As Deemer et al. (2016)indicates, it is difficult to correlate supersaturation of water to actual fluxes, sinceebubbulation from anaerobic deposits will be the dominant mechanism of emissions. I
think supersaturation might also be explained from natural emissions and is not bydefinition an indication of anthropogenic influence.

Hans Oonk

Accepted withmodification

While the supporting information in the Deemer et. al., 2016 review of global
publications provides a dataset for 262 reservoirs, only 81 measured both CO2
and CH4 emissions, and for only 8 and 4 of these were classifications of thereceiving environments as eutrophic or oligotrophic provided. That limited datasuggests a factor 2 between the relative CH4/CO2 yield due to recipient status.
On the other hand, the data in Table 1 indicates a much larger difference, anorder of magnitude, between rivers and other environments. As a Tier 1
method then, distinguishing between riverine and reservoir/lake morphologies
is the most useful improvement on the FOD we can make. We therefore use
these data, updating the riverine CO2 emission datum using Lauerwald, 2015 togenerate the EFs. This takes into account that the accumulation of organic
matter in sediments is a key factor in the evolution of methane.

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I don't understand the justification of the default value of MCF of 0.27 (increase from 0.1
in the 2006 GL). Can you provide a more accurate description of your method of
estimating this MCF? Please be accurate in use of your references, and don't add
references you are not actually using. I've been reading the references Deemer et al (2016);
Smith et al. (2017); Wang et al. (2017) en Yang et al. (2017) and they all only reportsurface emissions of methane in e.g. mg/m2/day and the variation in emissions isenormous (e.g. figure 1 in Deemer shows emissions might vary from 1-1000 mg/m2/day).
How do you recalculate these surface emissions to get en estimate of MCF? In order to doso, you will need the total surface of a reservoir (to calculate total emissions from areservoir in ton CH4 per day) and in addition collect information of the population sizethat deposits waste water into the reservoir, to get an estimate of TOW into the reservoir(in ton BOD per day). MCF can be calculated from the ratio of total daily emissions fromthe reservoir, total daily input of BOD into the reservoir and B0. Did you make suchcalculations and can you show us the data? Or did you e.g. only use the carbon budgets infigure 1 from Tranvik et al. (2009)? Here two cases are described. In one 19% of(DIC+DOC+POC) is converted in methane. In the other one 2% of
DIC+DOC+TOC+POC is converted to methane. Again, I don't recognise the MCF=0.27.

Hans Oonk

Accepted withmodification

It may be possible to construct overall carbon budgets for reservoirs around theworld in the manner suggested by the reviewer, but this would be a massive
undertaking. Instead, we revised our proposed default factor using a global
average partitioning factor based on Figure 5 from Tranvik to partition carbon
inputs to aquatic systems between the atmosphere and other recipients. Then weused the flux data contained in the reports collated by Deemer, plus the others
mentioned, to describe the relative yield of the principal gaseous emissions(CO2 versus CH4). This results in a much lower default factor based on rivers(0.035) and 0.19 for reservoirs. The derivation of the MCFs are now provided
in a new annex.

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The value of MCF=0.27 is for sea, river and lake discharge and the justification of the
MCF=0.27 is based on Deemer et al (2016); Smith et al. (2017); Wang et al. (2017),
Yang et al. (2017) and Tranvik et al. (2009). Alle these articles (apart from Smith et al.)are about emissions from lakes and reservoirs. Deemer et al. start their article, stressing theimportance of reservoirs for the global methane budget. Wang mentions reservoirs to be
hotspots for methane. I get the impression that reservoirs react sgnificantly different thane.g. rivers . In another comment I questioned the justification of MCF=0.27. Howevereven when this 0.27 is justified, I think it might only apply to reservoirs and lakes. In
rivers, flow rates are much higher and you will have much less deposits, containing
organic carbon under anaerobic conditions, which are an important source of methane inlakes and reservoirs. How do you justify the extrapolation of the MCF for lakes andreservoirs to rivers and seas?

Hans Oonk

Accepted withmodification

See response to comment 2602.

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I don't understand the relevance of the sentence "using the stoichiometric … dissolved O2
is obtained". How is this sentence relevant for understanding the proposed MCF=0.27?

Hans Oonk

Accepted

Explanatory text was added to a new annex. The MCF is derived from the mass
ratio of the yields of methane and carbon dioxide. These gases are derived fromcarbon inputs to the aquatic system. To convert those inputs to a practical
COD-based figure we use the same assumption as was applied to generate thevalue Bo, that glucose is the carbon source.

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It is not clear to me. Is it "kg dissolved O2"? In short, 1 kg of C per kg of O2, what does it
mean? Where is this ratio found or when should it ba applied?

Adalberto Noyola

Accepted

We have revised the text to refer to this value as "kg COD." It is just the inverseof the value calculated in appendix 1.

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The MCF of 0,27 should be applied also to treated waste water, even the organic content
of the treated waste water mainly consists of COD, which was not degraded in the waste
water treatment plant?

Christoph Lampert

AcceptedSee response to comment 2600 and 2602.

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Is there a difference in the MCF if the waste water is discharged to a reservoir, to a lake or
to rivrs, where flow rates are much higher?

Christoph Lampert

AcceptedSee response to comment 2602.

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It is not clear how the MCF of 0,27 was derived.

Christoph Lampert

AcceptedSee response to comment 2602.

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Deemer et al (2016) may not be an appropriate reference or data source for the ratio of
CH4 to CO2 emissions from aquatic systems receiving wastewater. The MCF for
freshwater systems appears to be primarily based on data from this study, and isconsequently likely to be too high to represent natural water bodies. Deemer et al (2016)
studied the impacts of artificial reservoirs created by dams, which as they note in the paper"are distinct from natural systems". One key difference that they highlight is that thegreater fluctuations in water levels in artificial reservoirs compared to lakes can enhanceCH4 bubbling (ebullition) rates. Deemer et al (2016) demonstrate that average areal CH4emissions from reservoirs are higher than natural water bodies (e.g. Table 1; emissions
from reservoirs -- their study -- compared to emissions natural water bodies, derived fromother sources).

Emil Laurin

Rejected

Deemer's data actually suggests that the yield of methane versus methane +carbon dioxide emissions from natural lakes overlaps the range for reservoirs ofvarious kinds. She says "we did not detect any significant difference between
the areal emission of CH4, CO2, or N2O from hydroelectric versus
nonhydroelectric systems" (p959). Her Table 1 suggests reservoirs in her study
emit 27% of the (CO2+CH4 carbon) as CH4-C, while the range for other folks'
calculations was 14-16%, other hydroelectric reservoirs 6-15% and lakes 16%.
This is before consideration of the fact that only 52% of those cases assessed
ebullition, which Deemer says is responsible for 40-60% of emissions.
Correcting for this the other calculations are 20-22%, 8-20% and 19%
respectively. The datum Deemer borrowed from Raymond 2013 for rivers is
obsolete and inflated according to Lauerwald 2015. (Taking Lauerwald's update(650 Tg/yr) into account Deemer's riverine yields are between 0.2 and 3%, butthat does not include ebullitive flux - correcting the data from Stanley et al2016 raises that range to 0.4-6%.) The main point here is that the absolute flux
rates may be higher for artificial reservoirs than natural lakes, but the ratio offlux rates is not so different. The contrast with rivers is much stronger, where
Deemer's table has a lower methane yield. For a discussion of the relevance of
this, see comment 2606. This is now described in the annexes.

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Please supply a motivation/justification for the change in methodology and the
MCF=0.005 for centralized, aerated treatment plants. Although I welcome that you
removed the difference between "well managed" and "not well managed", yousignificantly decrease the emissions from waste water treatment plants in countries, where
until now part of the WWTP were assumed not well managed. For other countries (withlargely well managed waste water treatment plants), emissions are significantly increased. I
think such a change in average MCF requires a motivation, preferably justified by aninventory of recent emission measurements at waste water treatment plants.

Hans Oonk

Accepted withmodification

Although it may appear that the removal of "well managed" and "not wellmanaged" from the emission factors would result in no differentiation between
those types of systems, that is not the case. Not well managed systems would
have fewer organics removed from the treatment system, and would therefore
result in a higher level of methane emissions, all else being equal.
Regarding the justification to revise the MCF for centralised, aerobic treatment
system, additional text and citations for the MCF have been added. Sewer
collection systems provide an environment conducive to the formation of CH4,
which can be substantial depending on the configuration and operation of thecollection system (Guisasola et al, 2008). Recent research has shown that atleast a portion of CH4 formed with the collection system enters the centralised
system where it contributes to CH4 emissions from the treatment system(WSAA, 2009). Although there are insufficient data to quantify emissions
directly from the sewer collection system, the emission factors presented forcentralised treatment plants account for dissolved methane entering thetreatment systems.

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In his PhD-thesis Daelman refers to measurements performed by STOWA at two WWTP
(Kortenoord, Papendrecht). The majority of emissions (86% and 77%) from those two
WWTP was attributed to methane, generated in the sewer system, coming with the effluent
and being stripped in the WWTP. So here it appears that it is not that much the water linein the WWTP, that is causing emissions but methanogenesis in the sewer system. This is
an indication that emissions from the water-line of a WWTP is not that much dependent
on the WWTP itself, its load or its management. I remember Felix Vogel (LSCE) giving apresentation (at TNO in Utrecht, with your LA Céline Gueguen present), referring as wellto the importance of the influent as a source of methane.

Hans Oonk

Accepted withmodification

See the response to comment 2610.

Authors note

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In the past 12 years, since the publication of the 2006 IPCC Guidelines, a number ofgroups have been measuring methane emissions from waste water treatment. Did you
perform an inventory of these measurements, when defining the MCF for WWTP? I think
it is not my task as a reviewer to perform a full overview, but I know measurements are
performed and reported by Jakob Monster and Charlotte Scheutz (DTU Denmark); Felix
Vogel et al. (LSCE France); Arjan Hensen (ECN, Petten Netherlands); Matthijs Daelman(TU Delft, Netherlands), STOWA (Netherlands). There will be more, so I think there is a
lot of scientific information available, that can be used to improve MCF for WWTP. This
table is an overview of some of the available measurememts of total emissions from
WWTP (incl. sludge treatment), based on Oonk (2004) and Daelmans PhD-thesis, chapter
5, with some additions. Emissions in kgCH4/kgCOD in the influent. Daelman (2015):
0.0113; Czepiel et al. (1993): 0.0016; Wang et al. (2011): 0.0008; STOWA (2010):
0.0087; STOWA (2010): 0.0053; STOWA (2010): 0.0120; Hensen (2001): 0.0035;
Hensen (2001): negligible; Hensen (2001): 0,0015. Additional estimates can be found e.g.
in Yver-Kwok et al. (2014), whose measurement boils down to an estimated 0,0015 andYoshida (2014) whose measurements result in 0.02. LSCE (France) is about to publish
their emissions from WWTP, as a part of a PhD-project. Considering the importance of
this IPCC-process, LSCE might be persuaded to hand over the information to the IPCCexpert group. If you want to make an overview of this for the 2nd draft, I hereby offer myassistance to gather and interpret information.

Hans Oonk

Accepted withmodification

See the response to comment 2610.

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No arguments are given, why "well managed" and "not well managed" systems shall show
the same MCF-value. However, especially the O2-concentration in the waste waterstrongly influences methan generation.

Christoph Lampert

Rejected

The removal of "well managed" and "not well managed" was intended to be
replaced by an assessment of sludge removed for "not well managed" systems,
and to acknowledge that the EF isn't necessarily different, just the amount oforganics subject to conversion to methane. Additional text has been added toelaborate on this topic. See also response to comment 2616.

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This paragraphs suggests, that methane emissions from waste water treatment plants are
significantly increased, the moment the design capacity of a waste water treatment plant isexceeded. Do you have proof of this? I do not believe this is true. First of all, there isdifference between design capacity and technical capacity. An engineer/supplier of a
WWTP is responsible for the WWTP to be able to meet its objectives and he might beheld accountable when this is not the case. So there will always a technical overcapacity,
compared to design capacity, where the system will still run without problems. There isalso a seasonal influence. In summer (tourist season), water temperatures are increased,biological processes are enhanced and the technical capacity might even be increased
further beyond the design capacity. When the technical capacity is exceeded, residence
time in the WWTP might be insufficient or aeration might be insufficient. If anything
happens, conditions will first become anoxic under anoxic conditions both anaerobic andaerobic degradation is limited and the concentration of BOD5 in the effluent will increase.
Part of the BOD5 will volatilise and cause odour nuisance. When aeration becomes evenworse, conditions become mildly reducing (negative redox). Because they are relatively
easily reduced, N and S in the wastewater will be converted to NH3 and H2S, causingodour nuisance. Methanogenesis requires severe reducing conditions (high negative
redox) and an almost exhausted pool of N and S. So even when technical capacity is
exceeded, this will cause other problems, before it will result in methane. First of all a
WWTP will not comply anymore to its legislation (BOD in effluent) and this is frequently
monitored and reported. So maybe compliance to BOD5-criteria is a better indicator andmore accessible criterion of a waste water treatment plan working well, than overload incertain seasons.

Hans Oonk

Accepted withmodification

If a plant is overloaded, the removal of organic material as sludge will be
reduced and should be reflected in the calculation of S in Equation 6.1A.
Therefore, compliers do NOT have to consider different emission factors forwell managed versus not well managed since the amount of organics removed
from overloaded systems will be reduced and will result in a higher amount ofmethane emissions compared to well managed systems. The text was revised toelaborate on this topic.

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Hans Oonk

Accepted

This paragraph has been removed

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Hans Oonk

Accepted withmodification

See response to comment 2618

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This paragraph will create a lot of extra work for inventory compilers and managers ofwaste water treatment plants. Please be aware that some countries have thousands of waste
water treatment plants (WWTP). Germany has almost 4000; Poland 1500; UK 1800. EUMember States have statistics available on load entering and physical capacities all
WWTPs in the framework of the Urban Waste Water Treatment Directive. However this ison a annual basis. They don't have information available, to evaluate whether during partsof the year design capacity is exceeded. Your proposal forces countries to perform a major
inventory-effort to improve the emission estimate of something which is at the moment a
non-key category emission source.
Without further guidance, this paragraph will cause a lot of discussions upon review. Your
draft might be interpreted by reviewers, that countries need to develop a CS-method toquantify emissions, the moment they can not proof that all WWTP within a country do not
exceed design capacity during parts of the year. So many countries will be forced into aliterature review of a R&D-programme by reviewers. And all of this for for a non-key
category emission. When you propose this inventory of seasonal variability of load to
WWTP as part of good practice, you will also need to supply a Tier 1/Tier 2 default
methodology that countries can use, including emission factors for WWTP, when design
capacity is exceeded for parts of the year.
Inventory compilers should evaluate if an aerobic wastewater treatment system isoverloaded or not. In consequence this would mean, that annual data will not be sufficientand compilers resp. the treatment plants would have to gather/provide intraannual data. In
many contries it will be difficult even to obtain annual average data. The consideration of
the number of tourists is not really helpful, as (i) tourism is concentrated to several regions(the regions may differ between summer and winter) and (ii) typically the design capacityof waste water treatment plants is significantly higher than the average load which meansthat there is a"reserve" for additional loads. Further the regulations concerning effluent
quality have to be met, independend from the number of tourists.
As a conclusion: data on overloading will be difficult to be obained or will not be
available.

Christoph Lampert

Accepted withmodification

See response to comment 2618

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The GL's advices that it is good practise to consider tourist quantity in the evaluation of
the overloaded statutus of a aerobic treatment plant. However GL's do not define the"tourist areas" and there are no method how to obtain the tourist quantities. This might bedifficult task to include tourist quantities in the emission estimation in different regions of
the countries and to a certain wastewater treatment plant.

Pia-Kristiina Forsell

Accepted withmodification

See response to comment 2618

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It is not clear to me. Does it mean that in such cases, limited influent BOD will be
converted to biomass (S)? If it is the meaning, then the fraction of influent BOD notconverted to biomass will end in the effluent (and at the receiving water body).

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Please add a clear definition of 'advanced plants' in Table 6.1. In the 2019 refinement, you
introduce a new class of waste water treatment plants (WWTP): advanced plants. However
there is no clear definition of 'advanced plants'. The description suggests that any waste
water treatment plant with nitrification/denitrification has to beconsidered 'advanced'. In
many countries nitrification/denitrification is state of the art for a few decades, so'advanced' is not that advanced anymore. In the text on page 6.11 you describe this as
andvaced biological nutrient removal system (which is a unit-operation at a WWTP). Thisis even more confusing, because of you have a waste water treatment plant withnitrification/denitrification, does this qualify as a centralised, aerobic treatment plant anddo you need to calculate emissions from nitrification/denitrification separately?

good practice in italic

Authors note

Kewei Yu

Accepted

Adalberto Noyola

Accepted withmodification

It means that if a plant is overloaded, it will not operate as designed andtherefore will not achieve the level of solids removal that it was designed toachieve. Therefore, the amount of organics removed (S) will be smaller than atypical well managed plant, and (TOW-S) will increase resulting in increased
emissions. In this case, the mass of sludge removed (Smass) should be adjusted
to reflect the performance of the overloaded system. In addition, as stated by
the commenter, the amount of organics in the effluent will likely increase.

Hans Oonk

Accepted withmodification"Advanced plants" have been removed from the methane section, and a more
precise definition added to the nitrous oxide section.

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Give a proper justification of the high MCF for advanced plants or remove the difference
between advanced plants and managed aerobic treatment systems. In the 2019 refinement,
you introduce a new class of waste water treatment plants (WWTP): advanced plants. In
many countries, largest part of the waste water treatment plants will be consideredadvanced. Under the 2006 guidelines, these WWTP would count as 'well managed' with an
MCF=0. Now these WWTP become 'advanced' with an MCF=0.05. This will have a huge
impact on emissions from WWT&D for these countries. I think this change is only
justified, when you have substantial information supporting the assumption that
MCF=0.05 for waste water treatment plants with nitrification/denitrification. Please also
be aware that denitrification proceeds under much milder redox-conditons, than required
for methanogenesis. I don't think this qualitative explanation suffices as a justification ofthis huge increase in MCF. Do you have emission measurements available, that support
this MCF?

Hans Oonk

Accepted withmodification"Advanced plants" have been removed from the methane section, and an
updated MCF has been provided for all centralised aerobic treatment systems.
See response to comment 2610.

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Your proposed MCF is very high, compared to measured emissions. E.g. STOWA reports
emissions from 4 Dutch Advanced WWTP to be about 0,01 kg CH4 per kg COD
assuming in the influent (0,0025 kg CH4 per kg BOD; assuming B0=0.6, this yields an
overall MCF of 0.004. This is including the emissions from sludge treatment). Daelmans
measures emissions at the Kralingerveer WWTP, and ends up with relative high emissions.
However emissions are attributed to the pretreatment of sludge and posttreatment ofdigestate and not to the nitrification/denitrification at this plant.

Hans Oonk

Accepted withmodification

See response to comment 2610. The MCF for centralised aerobic treatment
systems was developed using data from Czepiel et al, 1993; Daelman et al,2013 (which references STOWA data); Kozak et al, 2009; Kyung et al, 2015;
and Wang et al, 2010.

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Why is the MCF for advanced plants insensitive for overloading? For centralised aerobic
plants, you propose an evaluation, whether the system is overloaded. I would expect
similar guidelines for advanced plants.

Hans Oonk

Accepted"Advanced plants" have been removed from the methane section, and an
updated MCF has been provided for all centralised aerobic treatment systems.
Regarding overloaded plants, the emissions should be based on an assessmentof organics removed in sludge, which would be less efficient for overloaded
plants.

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Only plants with anaerobic stages would be in this category. A advanced biologicalnutrient removal plant that only targets nitrogen (e.g. 4-stage bardenpho) does not have ananaerobic stage.

Patrick Coleman

Rejected

Some treatment systems with aerobic treatment zones may still form anaerobic
pockets where methane generation can occur. In addition, dissolved methane
formed within the collection system can enter an aerobic treatment system andthe methane is emitted in stages open to the air.

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see comment L_175

Adalberto Noyola

Accepted

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No literature is provided indicating that CH4-losses from advanced biological nutrient
removal systems are relevant. This is also true für centralized aerobic treatment plants(line 314-327). The production of Methane strongly depends on the temperature. The
MCF presented in Table 6.3 relate to which temperature of the waste water?

Christoph Lampert

Accepted withmodification

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Delphine Groupe de travail
GES - Astee répésenté par
VALENTIN

Accepted

add Phosphorus: to encourage the reduction of nitrogen and phosphorus..."See the response to comment 2610. In addition regarding temperature, much of
the research reviewed applies to cooler climate regions (Europe, North
American, China, and sub-tropical Australia), so sewage temperatures will belower and CH4 production rates/MCF are assumed to be conservative of thosein tropical climates with warmer sewage termperatures. Indeed one article
presented in Short et al (2017) by Chaosakul et al. (2014;
https://doi.org/10.1080/10934529.2014.910071) showed much higher
dissolved CH4 concentrations (10 to 20-fold higher) in sewered wastewater inThailand (sewage temperature 33 degrees C) than that observed in Australia(sewage temperature 22 degrees C), so it is likely that sewage CH4
production/conversion rates will be higher than what much of the literature todate suggests.

Comment ID Volume

To lineComment

ExpertResponse

Authors note

2636

5

Chapter From line
6

338

351

This paragraph is a bit disappointing. 80% of the paragraph ephasises the importance oftemperature for methane emissions from septic tanks, only to conclude in the last threesentences, that insufficient information exists to quantify this effect. When this isconsidered as highly relevant (e.g. in a Tier-2), I do recommend you to draft amethodology, even when ample information is available. Within the guidelines there are
more assumptions made, based on little or no evidence, but still widely accepted (e.g.
Ox=0.1 for managed landfills). Such an assumption will contrbute to the comparability ofemission estimates and makes it easier to review a Tier-2. Some information, that might beused: Based on measurements of CH4 emission rates from septic tanks a revised MCF of
0.22 for use in the emissions models is suggested (WERF – Water Environment Research
Foundation (2010): Leverenz, H.L.; Tchobanoglous, G.; Darby, J.L.: Evaluation ofGreenhouse Gas Emissions from septic systems. University of California). In AT an MCF
of 0.27 – applied for total TOW without sludge deducted – is used, based on temperaturedependent MCFs and average temperature conditions in Austria (based on Steinlechner,
E.; Berghold, H.; Cate, F.M.; Jungmeier, G.; Spitzer, J. & Wutzl, C. (1994): Mö
glichkeiten zur Vermeidung und Nutzung anthropogener Methanemissionen. Report desJoanneum Research: Institut für Umweltgeologie und Ökosystemforschung).

Hans Oonk

Rejected

From line 338 to line 341 the text indicates that temperature has an impact onanaerobic digestion, which is well known. However, we disagree that there issufficient information at this time to develop guidance or a Tier 2 methodology
incorporating the effects of temperature on CH4 production in septic systems.
Unfortunately, some countries have considered that there are no CH4 emissions
if their average annual ambient temperature is low. This is not correct. In order
to avoid that kind of conclusion, lines 341 to 343 in the text indicates that thetemperature in the septic tank does not solely correspond to atmospherictemperature, but also the use of hot and cold water and the ultimate gradient of
temperature inside the underground tank. In lines 343 to 348, the text also
indicates that countries that have seasonnal temperature trends that have low
CH4 emissions in winter are compensated by high CH4 emissions whentemperatures start warming (spring boil phenomena). In other words, the settled
TOW not converted to CH4 during the colder period will convert as soon as
temperatures warm sufficiently. Therefore, for simplicity and consistency, theTier 1 methodology does not consider a temperature-dependant EF.

9460

5

6

342

343

I think a reference is missing

Adalberto Noyola

Accepted

All the paragraph is based on the same reference [Leverenz 2010]. The
reference has been added.

2634

5

6

345

346

I don't understand why gas solubility is relevant for methane emissions from septic tanks.
Small part of methane generated is temporarily dissolved in the water phase. However adecrease/increase of this amount of methane, due to temperature changes won't havesignificant effect on methane emissions.

Hans Oonk

Rejected

It is specified because the decrease of solubility contribute to the "spring boil"
phenomena : CH4 is produced in large amounts (as TOW settled during the cold
period is now converted to CH4) AND CH4 tends to be emitted because of thedecrease of solubility.

4778

5

6

348

[ ]?

Kewei Yu

Accepted

The reference is indicated between [ ] instead of ( ) by mistake. It has beencorrected .

9462

5

6

351

Table 6.3, item Centralized aerobic treatment. The dissolved CH4 comming in the influent
is not considered. I think that is should be, by all means. See comments L_130 (Table 6.1,
first one) and L_162. I emphazise the following: "As the emission point is in the WWTP,
it is here that the control measures should be applied; in consequence, the Tier 1 should
consider this emission in the CH4 inventory of the wastewater treatment facilities."

Adalberto Noyola

AcceptedSee response to comments 9436 and 9446.

9464

5

6

351

Table 6.3, item Advanced biological nutrient removal system. In the paper of myauthorship that will be sumbitted shortly, we recommend a MCF of 0.08 for intertropicalcountries.

Adalberto Noyola

Accepted withmodification

9466

5

6

351

Table 6.3, item Anaerobic reactor. I suggest to add: (UASB or similar). No confusion willarise with anaerobic sludge digesters (see following comment)

Adalberto Noyola

Accepted

9468

5

6

351

Table 6.3, item Anaerobic digester for sludge. A clear explanation should be provided inorder to use this MCF properly. It should be explained that it will affect only the sludge
removed from the wastewater treatment line, as it will be that waste stream that will trated
in the digester. See comment L_245.

Adalberto Noyola

Accepted withmodification

See response to comments 2596 and 9468. Adjustments have also been made to
the text related to Equation 6.1A.

2638

5

6

351

In the 2006-version of this table, an MCF for septic tanks of 0.5 was given, with anadditional remark there was an additional remark, that 50% of TOW settles in the tank.
The common interpretation of this is, that 50% of the methane potential of the influent isemitted as methane. Formally, this interpretation is not in line with eq. 6.1, since an MCF
of 0.5 strictly means, that 50% of the difference between (TOW-S) is metabolised into
biogas. So when 1 kg TOW enters the septic tank, 0,5 kg settles in the tank as sludge andof the remaining 0,5 kg TOW, 50% is a source of methane. But again, I believe this formalinterpretation of the 2006 guidelines is not what was intended. Nonetheless, the 2006
guidelines were somewhat ambiguous and I guess are in need of improvement. One way
forward is to introduce a default assumption that 50 % of TOW is removed as sludge, in
combination with an MCF=1.

Hans Oonk

Rejected

In the 2006 Guidelines, the MCF was an estimation based on a MCF and an
hypothesis assuming that 50% of TOW is settled in the tank and available foranaerobic decomposition. In the 2019 refinement, the MCF has been calculated,consistently with Equations 6.1A and 6.3C and the default Bo, from a set ofmeasurement data collected from septic systems. The MCF "seems" to be thesame as the one presented in the 2006 Guidelines (i.e., 0.5) but based on
guidance in the 2019 Refinement the MCF has to be applied in combination
with the parameter Sseptic. See also the response to comment 2650.

351"Advanced plants" have been removed from the methane section, and an
updated MCF has been provided for all centralised aerobic treatment systems.
See response to comment 2610. There were insufficient data to differentiate
methane emissions from non-BNR and BNR treatment systems.
Text has been updated.

Comment ID Volume
8712

5

Chapter From line
6351

To lineComment

ExpertResponse

352

The MCF for sea, river and lake discharges has almost trebled compared to the 2006
IPCC GL. However, it is not clear exactly what is the basis for this value. The referencesused and a description on how the MCF has been derived from the references should be
included. The default MCF for centralised aerobic plants has been changed while retaining
the same range. The text (line 315ff) states that the update has been made to reflect thepotential for emissions. However, the potential was recognised in the 2006 GL with theindication of a range of 0-0.2. The reasoning for changing the default value from 0 to
0.005 should be included. These same two comments apply for Table 6.8 as well.

Ole-Kenneth Nielsen

Accepted withmodification

7552

5

6

351

352

Anaerobic shallow lagoons would only occur in warm countries and depends on theirloading, see previous comment on Advanced biological nutrient removal systems

2640

5

6

352

358

2642

5

6

363

4168

5

6

364

Authors note
Regarding the MCF for sea, river, and lake discharges, see the responses tocomments 2602 and 2608.
Regarding the MCF for centralised aerobic plants, see the responses tocomments 2610 and 2778. Although the potential for emissions was recognizedin the range provided in the 2006 Guidelines, the use of zero as a default factor
essentially eliminated this source of emissions from many countries'
inventories. The default factor has been updated to reflect the most recent
measured data, and to affirm that emissions do occur from these systems.

Patrick Coleman

Rejected

Anaerobic shallow lagoons are also used in temperate climate countries likeFrance and Australia for sludge stabilization and drying as well as forfacultative/anaerobic wastewater treatment.

An increasing number of countries have statistics available on total amount of BOD/COD
in the influent of all waste water treatment plants, or people equivalents of waste water
treated. These statistics can be used as activity data in the calculation of emissions andthis should be preferred above estimation of TOW, using eq. 6.3A. Other countries don't
have statistics on BOD/COD/p.e. treated, but have good statistics on the share of total
population, connected to centralised WWTP, using septic tanks, etc. use of these statistics
is also preferred. Please include a paragraph, explaining that use of these statistics ispreferred above estimation of TOW for specific treatment pathways, using 6.3A. On top(and even though it is straightforward), you need to include guidance on how statistiscs on
BOD/COD/p.e./connection to sewers and centralised treatment can be used to quantify
TOW.

Hans Oonk

Accepted withmodification

Countries are able to use country-specific data in a higher tier approach thanthat presented in the refinement.

368

In my understanding of the 2006 guidelines, S is the amount of TOW removed as sludge(2006 GL, Vol 5, Chapter 6, page 6.20). TOW in the influent (TOW_influent) is either
metabolised and released as a gas (TOW_gas, mainly as CO2), ends up in sludge(TOW_sludge) or is released with the effluent (TOW_effluent). The overall materialbalance applies for TOW, so TOW_influent = TOW_gas + TOW_sludge +TOW_effluent. In my understanding eq. 6.1 in the 2006-GL (and also the 1995 revised
guidelines) describes methane emissions, as being proportional to the amount of TOW
metabolised and released as gas (= TOW_influent-TOW_sludge, while neglecting
TOW_effluent). In addition, emissions from sludge can be assumed to be proportional tothe amount of TOW metabolised and removed as gas during sludge treatment. Again myunderstanding S is the amount of TOW, removed as sludge (so TOW_sludge in thematerial balance above). Your definition of Krem in line 366 is ''how much organic matteris removed per ton of sludge produced" and I can only interpret this as Krem=(TOW_gasTOW_sludge)/Smass, while it should be Krem=TOW_sludge/Smass. The default value inline 390 of 0.8 seems to be in line with the definition of Krem= TOW_sludge/Smass.

Hans Oonk

Accepted

Text has been updated to clarify that we are discussing the amount of organic
matter removed in sludge.

371

It is unclear how the default value of 0.8 for Krem was derived from the numberspresented and discussed in in this section. Please clarify or discuss in more specific detail
how the sludge factor, Krem, was derived from the % and kg of BOD removed in primaryand secondary treatment. If the discussion is not directly relevant to the Krem value orother numbers used in the guidelines, I would recommend removing that text.

Emil Laurin

Accepted withmodification

The text has been updated to provide a better explanation of Krem.

Comment ID Volume

To lineComment

ExpertResponse

Authors note

2644

5

Chapter From line
6

367

371

Hans Oonk

Rejected

The question is not "How much sludge is generated from BOD?" starting froma defined amount of BOD, but "How much BOD is removed per kg of sludge?"
starting from a known amount of sludge. Primary sludge is about 70% of thetotal mass of sludge generated and about 0.5 kg of BOD is removed per 1 kg of
primary sludge. Secondary sludge is about 30% of the total mass of sludge
generated and about 1.5 kg of BOD is removed per 1 kg of secondary sludge.
Thus Krem = (0.7*0.5) + (0.3*1.5) = 0.8.

2646

5

6

367

371

This sentence gives a rough estimation of sludge production in a WWTP. However, I do
not understand this information. In the primary treatment 30% of TOW is removed as
sludge. In a secondary treatment 1 kg sludge is produced per 1,7 kg BOD removed. So
assume the influx of a WWTP is 100 kg BOD per hour. 30 kg BOD per hour is removed
as primary sludge, which is 37.5 kg sludge (assuming 0.8 kg BOD per kg sludge). 70 kg
BOD per hour is fed into the secondary treatment. Assume the effluent contains 2 kg perhour BOD, 68 kg BOD is removed upon secondary treatment. Assuming 1.7 kg BOD
removed per kg secondary sludge, secondary sludge production is 40 kg per hour. So wehave 37,5 kg per hour primary sludge and 40 kg per hour secondary sludge. In total 77,5kg per hour. Assuming 0.8 kg BOD per kg sludge, 62 kg BOD per hour is removed as
sludge (and 36 kg BOD per hour metabolised and emitted largely as CO2?). The 70%
primary sludge and 30% secondary sludge in the following sentence seems to contradict
this.
This is detailed information on sludge production of WWTP. However I don't understandhow this information is used in the emission inventory, so for me causes confusion. If thisinformation is used, please give guidance on how it is used. If it is not used, please remove
the information from the draft.

Hans Oonk

Accepted withmodification

This information on sludge production provides an explanation of theparameter Krem. The Krem factor allows the inventory compiler to use a known
mass of generated sewage sludge in tons to and calculate the parameterS (theorganic component in the sludge) using Equation 6.3B.

2802

5

6

367

371

The different units used are confusing (primary sludge: 30% of influent BOD, secondary
sludge: 1,7 kg BOD per kg; 70% primary sludge and 30% secondary sludge by weight. It
would be helpful if the same units are used.

Christoph Lampert

Accepted

2804

5

6

367

371

In plants with primary treatment 1,7 kg BOD per kg of secondary sludge are removed(Line 368). Why is the amount of sludge removed (1-1,5 kg BOD per kg) in plants with noprimary treatment even lower?

Christoph Lampert

Accepted withmodification

See response to comment 9470.

9470

5

6

368

371

I tried to find out how the relationship 1.7 kg BOD per kg of secondary sludge and the 1 1.5 kg BOD per kg of sludge. Could it be better explained or give a reference? Does kg ofsludge means kg of total suspended solids?

Adalberto Noyola

Accepted withmodification

2630

5

6

372

376

What happended to the factor "I" in the 2006 GL, equation 6.3? This correction factor for
additional industrial BOD discharged into sewers is no longer included in new equation
6.3A calculating TOW for the various discharge pathways. If this is done, by accident,
please repair this in the next draft. If "I" is removed deliberately, please motivate this.

Hans Oonk

Rejected

WWT plants with primary clarification produce by sedimentation primarysludge in which 0.5 kg BOD is removed per 1 kg of TSS. Secondary sludge isformed from microorganisms which grow by consuming BOD. This BOD isused for cell formation and as an energy source; thus, 1.5 kg BOD is removed
per 1 kg of sludge. WWT plants whithout primary clarifiers combine bothprocesses in one tank and the resulting sludge is a combination of primary andsecondary sludge. This BOD removal should be between 0.5 - 1.5 kg BOD
removed. The text has been updated to provide a better explanation of Krem. But
note that there is no relation between 1.7 kg BOD per 1 kg secondary sludge
and 1 - 1.5 kg BOD per 1 kg sludge. These factors characterise two different
processes.
The factor I is still included in Equation 6.3 and should be used whencalculating the overall TOW treated. Equation 6.3A is then used to determine
the amount of TOW that is treated in a particular treatment/discharge pathway
or system, j, and each income group fraction i in inventory year. See Section
6.2.2.1, Step 1 for details.

7554

5

6

378

378

It is poor practice to not define the biocehmical oxygen test by the length of the test. The
most common test is BOD5. This test will measure most of the rapidly biodegradable
material and some particulate degradable material. In some countries, they use the BOD7
test. The BODu test is for over 20 days. Standard Methods for the Examination of Water
and Wastewater groups these tests under Section 5210.

Patrick Coleman

Rejected

This information is already provided in the 2006 Guidelines, which states on
page 6.7 that "the BOD concentration indicates only the amount of carbon thatis aerobically biodegradable. The standard measurement for BOD is a 5-day
test, denoted as BOD5. The term ‘BOD’ in this chapter refers to BOD5."

4952

5

6

379

Where is the equation 6.2A. Is is not present in the 2006 Guidelines as well.

Delphine Groupe de travail
GES - Astee répésenté par
VALENTIN

Accepted

The equation has been corrected to remove the reference to Equation 6.2A.

4954

5

6

380

Where is the equation 6.2A. Is is not present in the 2006 Guidelines as well.

Delphine Groupe de travail
GES - Astee répésenté par
VALENTIN

Accepted

The equation has been corrected to revise the reference to Equation 6.3 (in the2006 Guidelines).

4162

5

6

380

380

The text includes: “See Equation 6.2A”; however there is no equation 6.2A in the FOD
Draft Refinement, nor the in IPCC 2006 Guidelines.

Emil Laurin

Accepted

The equation has been corrected to revise the reference to Equation 6.3 (in the2006 Guidelines).

2632

5

6

380

380

Calculation of TOW (equation 6.2A) is missing in the draft

Hans Oonk

Accepted

The equation has been corrected to revise the reference to Equation 6.3 (in the2006 Guidelines).

The text has been updated to be more clear and consistent in use of units.

Comment ID Volume

Chapter From line

ExpertResponse

Authors note

Is tons of sludge, tons of dry matter (total solids)? Avoid confussion and specify.

Adalberto Noyola

Accepted

The equation has been revised to specify that tons/year sludge should be as dry
mass.

The water content of the sludge influences the amount of sludge. It should be clear whichamount shall be provided: the amount of primary and secondary sludge before thethickener (data will not be available in many cases), the amount of sludge after the
thickener, the amount of sludge after dewatering, the amount after drying or the amoutn ofdry matter? This comment refers also to line 390 (kg BOD/kg sludge).

Christoph Lampert

Accepted

The equation has been revised to specify that tons/year sludge should be as dry
mass.

I could not find out the basis for proposing that default value (0.8 kg BOD/kg sludge). If I
use the following well known coversion factors ( 1.42 kg COD/ kg VSS ; 2.4 kg BOD/kg
COD) and considering a volatile fraction of 0.8 of TSS, I obtain 0.475 kg BOD/kg TSS

Adalberto Noyola

Rejected

The parameter 1.42 kg COD/ kg VSS describes the COD of sludge removed
from the system. The parameter S in Equation 6.1A is defined as the organic
component removed as sludge from the system. The factor calculated by you as
0.475 characterises only BOD converted to cell mass, but there is also BOD
converted to energy by cells (microorganisms) and is emitted as CO2. Therefore
the proposed default value is 0.8, as it includes both BOD removed for cellmass and BOD removed as source of energy.

390

Should there be different sludge factors for facilities with primary-only treatmentcompared to facilities with both primary and secondary treatment? From the discussion onlines 364-371, it appears that different amounts of sludge are generated in primary andsecondary settling.

Emil Laurin

AcceptedYes, different factors can be estimated for each process. A table has been added
to the text to provide such factors.

390

390

Do you have a justification for the default value of Krem of 0.8? The lines 368-371 might
be intended as a justification, but I don't fully understand it, and don't recognise the 0.8
from here.

Hans Oonk

Accepted withmodification

6

390

390

The default factor is 0.8 kg BOD/kg sludge. How does this fit to the values presented inline 368 (1,7 kg BOD/kg sludge resp. 1-1,5 kg BOD/kg sludge (line 371). Is this due to alow BOD of primary sludge?

Christoph Lampert

Accepted

5

6

392

394

The factor "0.5" should be e xplained below the equation.

Patrick Coleman

Accepted

Sludge produced in a WWT plant is a mixture of primary and secondary sludge.
Therefore, the resulting Krem is lower. The text has been updated to provide a
better explanation of Krem.
Additional discussion has been added to the text.

5

6

392

405

Hans Oonk

RejectedSee response to comment 2638.

2652

5

6

392

405

In the 2006 Guidelines it is described, that 50% of TOW entering the septic tanks, settles
as sludge. I think that the MCF of 0.5 for septic tanks is an elaboration of this assumption
in a sense that 50% of TOW settles as sludge and 50% is assumed to anaerobicallymetabolised into biogas. So the 2006 guidelines are not consistent in application of eq.
6.1, and you will have a chance to repair it in the 2019 refinement. By introducing
equation 6.3C, I think you will have a clear improvement of the guidelines for septic tanks
and I think the default of the 2006 guidelines can be best described by assuming 50% of
TOW settles as sludge (so in equation 6.3C F=1) and MCF=1. So instead of describing
emissions as B0*0,5*TOW, you describe emissions as B0*1*(TOW-S)=B0*1*(TOW0,5*TOW)=B0*0,5*TOW. So the latter assumption boils down to the same. However it isa more in line with Equation 6.1.
My interpretation of 'Accuracy' (one of the ACCCT-criteria) is that the default value of Fin equation 6.3C should be free of bias. So a default value should not be a worst case (nosludge removal), but a best guess of the effect of average sludge removal. The proper way
forward to encourage countries to improve their estimate of F through the decision tree.
When using the default value results in a conclusion, that emissions from septic tanks are
relevant (e.g. contributes to WWT&D being a key source category), application of ahigher Tiered method should be encouraged and a more country specific value of F
should be determined.

Hans Oonk

Accepted withmodification

2424

5

6

428

Takefumi Oda

Accepted

Typo corrected.

8714

5

6

428

429

In addition to listing B0 defaults for specific industries, there should also be a default for
non-specified industry, e.g. the default value from the 2006 IPCC GL of 0.25.

Ole-Kenneth Nielsen

Accepted

A value for other industry not elsewhere specified has been included.

2810

5

6

429

430

As mentioned above, not literature is provided on the MCF values from "Centralized,
aerobic treatment plants" and from "Advanced biological nutrient removal system".

Christoph Lampert

Accepted

See the responses to comments 2610 and 2774.

2812

5

6

437

437

"Updated default values are in new Table 6.15, Section 6.4.3." In Table 6.15 no default
values for the MCF are presented.

Christoph Lampert

Accepted

This reference has been fixed. Table 6.15 presents uncertainty data for nitrous
oxide emission factors. Uncertainty for MCFs can be found in Table 6.7(domestic and industrial wastewater).

9472

5

6

389

2806

5

6

389

9474

5

6

390

4170

5

6

390

2648

5

6

2808

5

7556
2650

To line389

Comment

A “Bo” on the new table 6.2A appears ”B zero”.

The text has been updated to provide a better explanation of Krem.

We agree that establishing a default factor for F of zero (which corresponds tono sludge removal) results in a conservative assumption in terms of estimating
emissions. Instead, we propose a default factor of 0.5, which corresponds to thesituation where 50% of the population managing their septic system arecomplying with the sludge removal instruction.

Comment ID Volume

To lineComment

ExpertResponse

Authors note

7176

5

Chapter From line
6

467

469

When a country-specific emission factor (EF) is not available for lack of measurements, aregion-specific EF approach could be used. For instance, few WWTPs have been
investigated for N2O emissions in South America. However, EFs have been published forseveral WWTPs in Rio de Janeiro, Brazil (see supporting materials, Vol5_Chp6_L467469_ACB_1,Vol5_Chp6_L467-469_ACB_2, Vol5_Chp6_L467-469_ACB_3). Thus,
countries in South America could use the EF developed in Brazil for their estimations. To
expand it a little further, EFs from tropical climate countries may differ significantly fromtemperate climate countries, as temperature plays a significante role on the microbialactivity and N2O production. Therefore, using a EF based on climatic-specifc regions
should be considered in this report.This way, tropical countries could make use of EF
published for Brazil, Australia, etc, which is far more appropriate than making use of a
global EF. Therefore, I propose modifications to the tier methods: for countries where acountry-specifc EF is not available (Tier 2), using a climate-specific or a region-specific
EF should be highly considered instead of falling into the Tier 1 method.

Ariane Coelho Brotto

Accepted withmodification

Use of a country-specific EF which comes from the same region or climate area
is also good practice. Such EFs might be available not only in scientific
literatures but also in the EFDB. Default values were not provided in this 2019
Refinement but explanation was added to this paragraph.

7178

5

6

471

473

Even though Tier 3 method is the most suitable approach for national GHG inventories,
since N2O emissions are highly variable depending on the treatment process, treatment
operations (e.g.diurnal variations of nitrogen load, anoxic-aerobic transitions, etc.) andexternal influences (e.g. seasons, temperature), national level policies and incentives forbottom-up measurements are still lacking. Therefore, the Tier 3 method approach will
likely be overshadowed and lose its purpose.

Ariane Coelho Brotto

Rejected(inter)national policy incentives are not currently in existence/enforced to drive
bottom-up N2O emissions method development; however, some countries havenevertheless done a lot of research in this area. These are very good data for thedevelopment of a Tier 3 method. So it should be at the discretion of individual
nations to determine the most appropriate N2O reporting/inventory method.

2654

5

6

479

499

Since N2O is generated upon nitrification/denitrification, its emissions will be related tothe amount of N removed in WWTP. In equation 6.7 you propose to calculate N2Oemissions, using TN_DOM as activity data. I would prefer to calculate N2O-emissions
proportional to the amount of N-removed so TN_DOM * N_REM. This also avoids
double counting, because the part of N that is not removed in WWTP will still be a sourceof N2O after discharge in open waters.

Hans Oonk

Rejected

N2O emissions arise from the amount of N processed (nitrified/denitrified);however, it does not necessarily apply directly to the fraction removed. For
example, for WWTPs nitrifying only or targeting partial nitritation, N removal
is not achieved, only transformation from NH3 to NOx; however, N2O
emissions will still arise. Furthermore, many published research papers reported
the N2O conversion rate based on influent N loading.

4956

5

6

509

Accepted

EFj is expressed in kg N2O-N/kg N. The units were corrected in the relevant
text.

2656

5

6

511

511

Indirect emissions occur, when waste water is discharged directly into surface waters andwhen the effluent of waste water treatment plants are discharged. The sentence here only
suggests the latter. I propose that you replace: 'It is also required to estimate indirect N2Oemissions from waste water treatment effluent ...' into 'It is also required to estimate
indirect N2O-emissions from direct discharge of waste water and discharge of waste water
treatment effluent ...'

Hans Oonk

Accepted withmodification

The text was changed according to the comment.

2814

5

6

518

518

The expression "N2O Emissions DOM" is misleading, as the total N2O emissions fromwaste water could be understood. "N2O effluent DOM" would be clearer.

Christoph Lampert

Accepted

N2O EmissionDOM was changed to N2O EffluentDOM.

2662

5

6

532

535

Please provide references of relevant publications on which your EF are based. Without
references, I can not check, whether I have additional N2O-measurements from waste
water available.

Hans Oonk

Accepted

A reference to the annex containing the references used to develop thisemission factor was added to the text.

2664

5

6

532

535

You plan to distinguish different types of WWTP, with different EF. On what information
will these be EF based? Will these EF be based on measurments at actual systems? If so,please make sure that measurements are of sufficient quality, cover sufficient temporal
resolutiona and are also performed under comparable conditions. Daelmans in his PhDthesis spends a whole chapter on the impact of sampling strategy on N2O-emissions. Both
diurnal and seasonal variation is large and as a result, development of reliable emission
factors require sufficient measurement data, througout the year. Please be aware, that thistable will have commercial impact as well. Communal investments often require an
environmental impact assesment. The 2019 refinement will be authoritative in future
impact assessments and will have impact on actual investments. Please make sure that yourEF are free of company interests (so are based on independent research).

Hans Oonk

Accepted withmodification

EFj is expressed in kg N2O/kg N BUT Table 6.12 expresses units in kg N2O-N / kg N -> Delphine Groupe de travailis this an error of units in the formula?
GES - Astee répésenté par
VALENTIN

Emission factors included in Table 6.12 are based on measurement data and arefree of bias.

Comment ID Volume

ExpertResponse

4958

5

Chapter From line
6536

To line

New table 6.12: The title should be Default EF values for domestic and industrial
wastewater since line 661 indicates that the default EFs for industrial wastewater are
shown in thisTable 6.12

Comment

Delphine Groupe de travail
GES - Astee répésenté par
VALENTIN

Accepted

Authors note

4960

5

6

536

New table 6.12: The type of treatment and discharge column is not clear enough for the
Wastewater treatment system part;

Delphine Groupe de travail
GES - Astee répésenté par
VALENTIN

Accepted withmodification

The type of treatment and discharge column has been renamed to "Type oftreatment and discharge pathway or system" for consistency with Figure 6.1. In
addition, the types of treatment included in Table 6.12 have been incorporated
into Figure 6.1.

4962

5

6

536

Conventional activated sludge processes = Are we talking about traditional Activatedsludge? If Yes the proposed EF is enormous! (0,047 kg N-N2O/kg N)

Delphine Groupe de travail
GES - Astee répésenté par
VALENTIN

Accepted withmodification

Categories of type of treatment were updated and further explanation of type oftreatment was added. Regarding the EF value itself, references and result ofanalysis for each EF are provided in the main body and annex.

4964

5

6

536

Oxidation ditch processes = Activated sludge (channell)?

Delphine Groupe de travail
GES - Astee répésenté par
VALENTIN

Accepted withmodification

Categories of type of treatment were updated and further explanation of type oftreatment was added. Upon further review of the data, an emission factor forthis type of system was not included.

4966

5

6

536

Anaerobic-aerobic processes = Activated sludge (BioP)?

Delphine Groupe de travail
GES - Astee répésenté par
VALENTIN

Accepted withmodification

See response to comment 4964.

4968

5

6

536

Sequencing Batch reactors = Activated sludge (SBR)?

Delphine Groupe de travail
GES - Astee répésenté par
VALENTIN

Accepted withmodification

See response to comment 4964.

7180

5

6

536

536

NEW TABLE 6.12. As discussed in comment Vol5_Chp6_L467-469, I propose to breakout the emission factors (EF, kg N2O-N/kg N) by region, either geografical or climatic,
instead of having only one glabal EF for each type of treatment.

Ariane Coelho Brotto

RejectedSee response to comment 7176. We don't think development ofgeographical/climatic EFs is possible and may not be warranted, as temperature
differences between global climatic zones are less likely to have a determining
influence on N2O emissions as they are on CH4 emissions, with methanogenesis
much more temperature-sensitive than equivalent N cycling processes.

7182

5

6

536

536

Ariane Coelho Brotto

Accepted withmodification

There are many different variations of treatment processes and it is not feasiblethat the guidelines cover all of these explicitly. However, the categories of typeof treatment were updated to be more comprehensive. See also response tocomment 4964.

2816

5

6

536

537

NEW TABLE 6.12 - "Type of treatment and discharge pathway or system": There areother types of treatment that have been investigated with a bottom-up approach for N2O
production and emission pathways that have not been listed in the table, for instance:
Moving and Fixed-Bed Biofilm Reactors, namely Integrated Fixed-Film Activated Sludge(IFAS) and denitrification filters, respectively. Please see supporting document forreference.
The provided emission factor now is 28 (Sequencing batch reactor) to 90 (conventional
activated sludge process) times higher than in the 2006 guideline. Respective literature
should be included.

Christoph Lampert

Accepted

Regarding the EF value, references and result of analysis for each EF areprovided in the main body and annex.

8716

5

6

536

537

The indirect emission is listed as being for untreated systems, it seems that the indirectemissions should be calculated based on the amount on nitrogen discharged to the aquatic
environment regardless of whether the wastewater has been treated or not. This should beclarified.

Ole-Kenneth Nielsen

Accepted

As you commented, these EFs are used for both untreated system and treatedwastewater. Explanation was added in the main text.

2658

5

6

536

537

In the introduction (line 217) you propose to use a Tier 2 method for indirect N2O,
distinguishing between eutrophic and oligotrophic waters. I think you should clarify what
default values in table 6.12 are intended as a general Tier 1 EF, and what values areproposed as a Tier 2 EF for oligotrophic and Tier 2 EF for eutrophic waters. I stress that a
Tier 1 method should be 'accurate', not leading to over- or underestimation (as far as you
can judge when preparing the 2019 refinement). So both a best- and worst caseassumptions should not be part of a Tier-1 methodology.

Hans Oonk

Accepted withmodification

Explanation was added to table 6.12 to clarify which one is EF for Tier 1 or 2.

2660

5

6

536

537

For indirect N2O, can you come with a clear definition of the receiving waters,
corresponding to the EF of 0.005 and of 0.018? The explanation is very technical withterms as 'hypoxic' and 'eutrophic'. The term 'oligotrophic' used in the introduction, but not
used in table 6.12? The term 'river' is in both 'sea, river and lake' discharge and in thecomments under 'estuarine, ...'. lakes also fit in both. For me it would be logical that you
distinguish between situations where you will have prevailing oxygen-rich conditions:'discharge of treated waste water or dischare in flowing rivers or open sea' and situations
with prevailing low-oxygen conditions (discharge of uncleaned waste waters in laes,
estuaries and reservoirs).

Hans Oonk

Accepted withmodification

Explanation was added to table 6.12 to clarify the how to use these EFs. Basedon other comments and discussion within authors, one EF would be used forTier 1, and another EF would be used for Tier 2.

The title of Table 6.12 was revised according to the comment.

Comment ID Volume

To lineComment

ExpertResponse

2666

5

Chapter From line
6

536

537

Most contries countries will have no reliable statistcs available on how much waste water
is treated in the various WWTP-systems. The source will be no key category in mostcountries, so you can not expect countries to perform elaborate inventories, to characterise
their WWTP. I think you will need to define a Tier 1 method, containing an average
default emission factor, a method distinguising different types of WWTP (as presented intable *) might be part of a Tier-2 method.

Hans Oonk

Accepted withmodification

Generic EF for Tier 1 method was provided in Table 6.12.

Authors note

2668

5

6

536

537

Is a sludge digester relevant in this context? Part of the N will be removed by sludge andpretreatment of sludge and post treatment of digestate might be a source of N2O. But thiswill be also the case (maybe even more) in other methods for on-site sludge treatment. If
you choose to include a sludge digester here, you need also consider adding information
non-AD sludge treatment.

Hans Oonk

Accepted withmodification

Other sludge treatment systems are included in this Table.

2670

5

6

536

537

The types of discharge pathways for calculation of N2O differ from the types, used for
calculation of methane emissions. This is very unhandy, because countries will have tocompile different sets of activity data for waste water treatment and discharge: one formethane (aerobic treatment plants, advanced plants, septic tanks) and one for N2O(conventional activated sludge proesses, oxidation ditch, anaerobic-aerobic, ...). I would
prefer if you would be able to synchronise the methodologies for calculation of methane
and N2O, using similar treatment pathways in both (goes for direct and indirect emissions)Hans Oonk

Accepted withmodification

Synchronization of treatment and discharge pathway or system for CH4 andN2O was considered and incorporated as applicable.

2672

5

6

536

537

For completeness, please make sure that all relevant discharge pathways, treatment
processes are dealt with in Table 6.12. This means that also treatment processes that most
likely do not result in N2O-emissions should be mentioned in the table (e.g. wate water
treatment processes, that do aim for N-removal, with removal efficiency and EF bothbeing 0).

Hans Oonk

Accepted withmodification

All relevant treatment/discharge pathways were considered in Table 6.12.
Explanation was added for some specific processes.

2674

5

6

536

537

Does the list of treatment pathways for waste water treatment systems include all possible
waste water treatment systems? E.g. where does the Anammox-process fit in? Are all
definitions well established? Will everyone understand what you mean with e.g. anoxidation ditch?

Hans Oonk

Accepted withmodification

See response to comment 2672.

4980

5

6

536

537

CAS EF is very high compared to some SUEZ on site measurements

Delphine Groupe de travail
GES - Astee répésenté par
VALENTIN

Accepted withmodification

Regarding the EF value, references and result of analysis for each EF areprovided in the main body and annex.

4982

5

6

536

537

Delphine Groupe de travail
Presently, it is seems to be not clever to identify different EF for different processes.
Indeed, many articles and also Suez trials showed that EF are impacted by biological tanks GES - Astee répésenté par
VALENTIN
operational parameters whatever the process in place (SBR/plug flow, biofilters, etc):
ammonia concentration, nitrites concentration, DO level, COD/N ratio, pH, T°, etc

Accepted withmodification

These parameters are highly dependent on the types of the processes in place aswell as the operational conditions. Although there is uncertainty associated with
the EFs proposed for all types of processes, we agree that grouping of thetreatment processes would be useful. We reconsidered the categores oftreatment processes when developing the new N2O EFs.
If a country has detailed plant-specific information, a higher tier approach canbe applied.

7558

5

6

536

537

The term "conventional" should not be used as its definition changes depending on what
jurisdiction the reader sits. Normally, we split the plants for this purpsoe into
carbonaceous only, nitrifying and nitrying/denitrifying. Biolgical treatment can be achived
bya number of means inclduing fixed film (e.g. trickling filters), suspended growth (e.g.
activated ludge), granular or hybrid (e.g. integratated fixed film activated sludge).

Patrick Coleman

Accepted withmodification

We reconsidered the categores of treatment processes with developing the new
N2O EFs. Clear distinction within categories of treatment process was provided.

7560

5

6

536

537

There is a degree of confusion in this section. An oxidation ditch is just an activatedsludge plant in a race track configuration. It may be aerated using a horizontal mechanicalaerator or a mixer + diffused. An MBR plant is an activated sludge plant that uses
membranes rather than a settling tank. Both can be set up to nitrify or nitrify/denitrify. I do
not see why they are not grouped with other activated sludge plants.

Patrick Coleman

Accepted withmodification

See response to comment 7558.

7562

5

6

536

537

Aerobic digesters nitrify and in some cases, also denitrify - why are they not on the list.
Authothermic Aerobic Digesters (ATAD) do not nitrify but may include a nitrification stepafter the digesters.

Patrick Coleman

Accepted withmodification

See response to comment 7558.

Comment ID Volume

To lineComment

ExpertResponse

Authors note

4808

5

Chapter From line
6

536

537

As above - it would be helpful to provide some discussion of the linkages between the EFs
for N2O in rivers and estuaries in footnote 21 in Volume 4, Chapter 11 and the EF for
Sea, river and lake discharge in table 6.12 in this Chapter. For example - can it beassumed that the EF in table 6.12 is the sum of both river and estuary factors from Vol4,
CH11? If this not the case why would there be different factors between Agriculture andwaste?

Mark Hunstone

Accepted

We added a description of the fact that the discharges from agriculture are of adifferent character to sewage discharges. Particularly the presence not just ofnitrates from fertiliser runoff but also ammonia and organic matter.

2818

5

6

541

542

Ammonia-N can not be removed by denitrification processes in the sewer system.
Probably the wording should be "nitrification-dentirification processes".
In sewer systems nitrification and denitrification should be low, if the residence time of thewaste water in the sewer system is low.

Christoph Lampert

Accepted withmodification

The wording in the text was changed to "nitrification-dentirification processes."
We note the comment regarding nitrification and denitrification in sewer
systems.

2820

5

6

547

547

"nitrogen is about 3.3 % of sludge by dry weight": in Vol 5 Chapter 3 Table 2.4A a default
value of 4.2% N is given for sewage sludge

Christoph Lampert

Accepted withmodification

Digested sludge can have a total N content anywhere in the order of 3-5% on a
dry weight basis (or even >5%), so both values are acceptable. That said, thistext was removed from Chapter 6 in order to not cause unnecessary confusion.

4780

5

6

559

Kewei Yu

Accepted withmodification

The underline was meant to reinforce that the data should reflect protein
consumed and not protein available. We have removed the underline.

7564

5

6

571

571

Fnon-com depends on the use of in sink disposal units which are banned in many cities

Patrick Coleman

Rejected

Table 6.13 presents default factors based on in-sink disposal or waste bin
disposal. In addition, this factor can be selected depending on the nation's
circumstances.

7566

5

6

572

572

Find-com will depend on local policy. Many jurisdictons do not allow or make it
economically painful to discard industrial nitrogen into the sewer.

Patrick Coleman

RejectedSee response to comment 7564.

2822

5

6

579

580

"Bath and laundry water can be expected to contribute an additional 10% to nitrogenloadings as well." What is the source of this additional 10%? If it is e.g. skin flakes, than
this would be allready included in the protein consumption.

Christoph Lampert

Rejected

Bath and laundry cleaning products are a source of nitrogen not included indata concerning protein consumption. There is evidence to support the 10%
additional loading of nitrogen from these sources, including:
G. Tjandraatmadja et al: Sources of contaminants in domestic wastewater:
nutrients and additional elements from household products, 2010, see pg. 35.
Mogens Henze. Biological Wastewater Treatment: Principles Modelling and
Design. ISBN: 9781843391883. IWA Publishing, 2008, see table 3.20
Gurpal S. Toor et al: Onsite Sewage Treatment and Disposal Systems:
Nitrogen, 2011, 2017
J. S. Lambe R. S. Chougule: Greywater - Treatment and Reuse, India IOSR
Journal of Mechanical and Civil Engineering (IOSR-JMCE) ISSN: 2278-1684,
PP: 20-26.

2824

5

6

583

584

Table 6.13: the logic is not clear. If a default value of 0,85 for protein consumed isassumed (Line 577) the resulting TNDOM differs depending on the Basis of Protein
activity data:
e.g. activity data protein available, in sink disposal: 100 % protein * 1,1 = 110%e.g. activity data protein consumed, in sink disposal: 0,85 * 100 % protein * 1,25 = 106%
But even more important: How is it possible, that finally more than 100% of the protein
available ends up in the sewer system if there is no significant additional N-source in thehouseholds (in sink disposal). The same is true for Waste bin disposal: if the FAOSTAT
data includes the available amount of protein, how is it possible that 100% of this protein
ends up in the sewer system even some part of the protein is disposed of in waste bins
(again, there is no signifiicant additional N-source)

Christoph Lampert

Accepted withmodification

There is an additional 10% nitrogen contributed from chemicals used inhouseholds. The parameter name may be confusing: originally "factor of nonconsumed protein" but after refinement "factor of non-consumed protein andadditional nitrogen from household products."

2678

5

6

591

593

Please move Equation 6.8 before equation 6.7.

Hans Oonk

Rejected

The numbering of equations and the order of presentation is to work in concert
with the existing 2006 GL.

2676

5

6

593

593

N_REM in this equation seems to be a country average N-removal factor over all
treatment pathways. So either specify that you need to calculate N_REM as the average of
N_REM for individual treatment pathways als listed in Table 6.12. Or rewrite thisequation as a summation over all treatment pathways, j. So N_EFFLUENT, DOM =SUM_j (TN_DOM,j * N_REM, j).

Hans Oonk

Accepted withmodification

consumed should not be underlined

Equation was revised as summation over various pathways.

Comment ID Volume

Chapter From line

To lineComment

ExpertResponse

Delphine Groupe de travail
GES - Astee répésenté par
VALENTIN

Accepted

Authors note
Nremov description deleted.

4970

5

6

640

"Nremoval = ..." is mentioned BUT this element does not appear in equation 6.11 sodelete this text

2426

5

6

640

Parameter “N removal” is not employed in the new equation 6.11.

Takefumi Oda

Accepted

Nremov description deleted.

2428

5

6

654

N2O emissions =>> N2O emissions ”IND”

Takefumi Oda

Accepted

Equation term was revised.

8718

5

6

687

688

Some of the wastewater generation data in Table 6.14 are identical to Table 6.9 of the2006 IPCC GL. However, several categories in Table 6.9 have been omitted from table
6.14 without any apparent reason. It would make good sense to have the tables consistentfor CH4 and N2O in terms of the industry types covered. Also, there should be somereferences for the nitrogen content as it is doubtful that such specific knowledge could bebased solely on expert judgement.

Ole-Kenneth Nielsen

Accepted withmodification

The industries listed in Table 6.14 are those in which N2O is emitted while
industries listed in Table 6.9 of the 2006 IPCC GL are those identified as CH4
emitters. Therefore, the industry list should not be the same for both tables. A
clarification has been added to the text and the list of citations has been
included.

8720

5

6

687

688

Landfill leachate is introduced as a separate source of emission from wastewater.
However, it is not clear exactly how this is to be interpreted. Is the intention that inventory
compilers should know (or acquire) the total surface area of landfills in the country inorder to estimate this? Also, it should be defined what 'well compacted' means and there
should be one default value, e.g. 17.5 % (with a range of 15-20) and 37.5 (with a range of
25-50).

Ole-Kenneth Nielsen

Accepted withmodification

Landfill leachate generated and treated at industries should be consideredwithin the industry emissions and not as a separate industry source of N2O.
Therefore, this entry has been deleted from the table.

7568

5

6

690

692

It is important to note that a nitrfying plant does not remove nitrogen except with thesludge. The nitrogen will either leave the plant with the effluent or the sludge.

Patrick Coleman

Accepted withmodification

We agree with the comment. Nitrogen removal ratio was provided in new
Table.

4782

5

6

691

use %

4972

5

6

696

Equation 6.14 is wrong: replace the - by ×: TN × Nremoved

2430

5

6

698

2432

5

6

702

7570

5

6

752

8722

5

6

4916

5

4918

Kewei Yu

Rejected

Delphine Groupe de travail
GES - Astee répésenté par
VALENTIN

Accepted withmodification

Equation 6.14 was revised.

This section has been removed.

New equation 6.14 is possibly a wrong equation. It may be “Σi(TN IND i *(1-N
REMOVED))”.

Takefumi Oda

Accepted withmodification

See response to comment 4972.

Does the “N REMOVED “ in the new equation 6.14 mean “N removal “ in the previous
new equation 6.11? If so, using same style is better.

Takefumi Oda

Accepted withmodification

See response to comment 4972.

772

It should be stated the value is 0.25 kg CH4/kg COD degraded. This is what Lexmondstated in his orginal report. Lexmond then stated that ratio of COD degraded to BOD5
=1.7 which means the equation is 0.425 kg CH4/kg BOD5 (assuming all the BOD5 isdegraded). The typical degradable COD fraction of raw sewage in Canada and the US isabout 18% to 20%. This COD does not degrade to form methane. Therefore, if you areusing COD data, you must correct your activity data for COD degraded. If you are using
BOD5, then use 0.425 kg CH4/kg BOD5 because the BOD5 test does not measure theunbiodegradable COD.

Patrick Coleman

RejectedSee response to comment 2684.

773

814

Annex 6A.2 is very interesting and could have impact as the gas generated fromwastewater treatment is currently accounted for as wholly biogenic. The science based on
the research cited seems to be quite solid also compared to many of the sources includedin the main chapter. It should be considered to describe this issue in more detail in themain chapter and whether the science is not sufficiently solid to include guidance in themain chapter on a default factor for fossil carbon in the wastewater.

Ole-Kenneth Nielsen

Rejected

Noted. No action can be taken because comment is out of scope of 2019
Refinement.

6.1

128

128

In Figure 6.1, please clarify in figure text that dotted lines correspond to sludge treatment
and filled lines correspond to wastewater treatment

Klara Westling

Accepted

A legend has been added to Figure 6.1 to clarify what lines represent
wastewater versus sludge.

5

6.1

130

130

In Table 6.1, I recommend to add "…or upgraded" or similar in the sentence "Sludge may
be a significant source of CH4 if emitted CH4 is not recovered and flared." located in twoboxes.

Klara Westling

Accepted

Additional text has been added.

4920

5

6.1

152

152

Might be good to clarify that no matter where N2O is formed it is usually stripped to air in
aerated parts of the treatment process

Klara Westling

AcceptedThat information was added to the text.

4922

5

6.1

176

176

I have seen measured values showing lower N2O emission from MBR processes, would
be good to clarify that the main contributor to emitted amount of N2O is HOW theprocess is operated, no matter what type of process it is.

Klara Westling

Accepted withmodification

See response to comment 4982.

Comment ID Volume

To lineComment

ExpertResponse4924

5

Chapter From line
6.2.2.1

230

240

In the updated version, I assume the steps will be renamed to Step 1-4, to avoid confusion
and misunderstanding.

Klara Westling

Rejected

Authors note

4926

5

6.2.2.1

254

254

Spelling error; "reports" should be "report"

Klara Westling

Accepted

4930

5

6.2.2.2

283

288

The suggested default value of 0.6 kg CH4/kg BOD is totally unrealistic. As shown inAnnex 6A.1 the theoretical value is 0.25 kg CH4/kg BOD removed. The figure 0.6 kg
CH4/kg BOD is formed by multiplication of 0.25 with 2.4 which is a common ratio
between COD and BOD in domestic wastewater. But with this operation all organic matter(measured as COD) is supposed to be degradable (normally measured as BOD, the part of
COD that is readily degradable). Of course it could be stated that given enough time allorganic matter will be degraded, but this takes at least several thousand years. It is
probably not even true under anaerobic (methane producing) conditions, look at peat andcrude oil.In the different listed systems in Table 6.3 the actual retention time is in mostcases from 10 hours to one year. During this time it is very unlikely that more than BOD isdegraded, giving methane. This means that the actual maximum methane formation is 0.25
x BOD. Using the factor 0.6 will overestimate the methane formation by at least the factor
2.4.The overestimation is probably even greater since the value of BOD is determined inaerobic systems. The actual anaerobic degradation is normally less than BOD. This is due
to both the fact that more compounds are aerobically degradable than anaerobically, and to
the presence of some oxygen, nitrate and sulphate in most wastewaters.If the factor 0.6 kg
CH4/kg BOD is used to calculate the estimated methane formation from a certain amountof BOD this will lead to a great overestimation of methane emissions. We hope we havemisunderstood the use of the factor 0.6 kg CH4/kg BOD. It is less embarrassing for us tobe wrong, than it would be to have given totally wrong figures in the statistics.

Klara Westling

Rejected4928

5

6.2.2.2

294

294

Dishcarged BOD values are even lower for "new" processes such as the MBR process. It
usually generates discharged concentrations of BOD < 2 mg/L. This is also common inwell managed conventional activated sludge processes.

Klara Westling

Accepted4944

5

6.2.2.3373

394

Regarding equation names, will the numbering be kept as eg. 6.3A, 6.3B, 6.3C or will they
be changed to eg. 6.1, 6.2, 6.3, 6.4, 6.5? The same question goes for numbering of Tables
etc.

Klara Westling

Rejected

Because the 2006 Guidelines are still applicalbe, the equation and table
numbering is meant to coordinate with that document. Therefore, thenumbering is not expected to change.

4932

5

6.3.1

474

474

Even though only a few countries have sludge removal data, all countries have some kindof sludge removal. I therefore find the default value of zero too low, even though we alsofind it difficult to quantify a specific default value.

Klara Westling

Rejected

It is difficult to decide default value for sludge removal as you mentioned.
Besides, no sludge removal from WWTPs such as lagoon would be practical insome cases. To be conservative, zero as a default value is reasonable.

4934

5

6.3.1.1

486

487

We are missing the footnote explaining the superscripted "1" after the box stating "Is this a
key category?".

Klara Westling

Accepted

The footnote was added. "1. See 2006GLs, Volume 1 Chapter 4,"Methodological Choice and Identification of Key Categories" (noting Section
4.1.2 on limited resources), for discussion of key categories and use of decision
trees."

4936

5

6.3.1.2

536

536

Spelling error in Table 6.12; the third (from the top) "Comments" box, "aerated tank"should be "aerated tanks".

Klara Westling

Accepted"aeration tank" was changed as "aeration tanks"

4938

5

6.3.1.3

597

597

Should NREM always be taken from Table 6.12, even if more country specific data isavailable?

Klara Westling

Rejected

Use of country-specific data is always recommended. Default values in the table
can be used if there are no country-specific data available.

4940

5

6.4.1.1

631

632

It might be a good idea to give an example of industry sectors with large N2O emission
potential (eg. refer to Table 6.14?)

Klara Westling

Rejected

N2O emission potential depends on how much nitrogen is discharged into a
WWTP and the type of WWTP used. Therefore, it would not be the same in all
countries.

4942

5

6.4.1.1

631

632

I am missing the footnote explaining the superscripted "1" after the box stating "Isindustrial wastewater a key category?".

Klara Westling

Accepted

The footnote was added. "1. See 2006GLs, Volume 1 Chapter 4,"Methodological Choice and Identification of Key Categories" (noting Section
4.1.2 on limited resources), for discussion of key categories and use of decision
trees."

2544

5

Annexes

Table 2A.1. Fourth Column (MSW Generation Rate, year 2010). The value of Argentina(South America) 0.45 should be replaced by 0.37.

Estela Santalla

Accepted

Revised as suggested.

2546

5

Annexes

Table 2A.2. There is available and updated data for Argentina

Estela Santalla

Accepted

Revised as suggested in FD.

Because the 2006 Guidelines are still applicalbe, the equation and table
numbering is meant to coordinate with that document. Therefore, thenumbering is not expected to change.
See response to comment 2684.