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Incineration of municipal solid waste in Brazil: An analysis of the economically viable energy potential
Journal Pre-proof Incineration of municipal solid waste in Brazil: An analysis of the economically viable energy potential Leo Jaymee de Vilas Boas da Silva, Ivan Felipe Silva dos Santos, Johnson Herlich Roslee Mensah, Andriani Tavares Tenório Gonçalves, Regina Mambeli Barros PII:
S0960-1481(19)31631-3
DOI:
https://doi.org/10.1016/j.renene.2019.10.134
Reference:
RENE 12503
To appear in:
Renewable Energy
Received Date: 30 April 2019 Revised Date:
14 August 2019
Accepted Date: 24 October 2019
Please cite this article as: da Silva LJdVB, dos Santos IFS, Mensah JHR, Gonçalves AndrianiTavaresTenó, Barros RM, Incineration of municipal solid waste in Brazil: An analysis of the economically viable energy potential, Renewable Energy (2019), doi: https://doi.org/10.1016/ j.renene.2019.10.134. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier Ltd.
1
Incineration of Municipal Solid Waste in Brazil: An Analysis
2
of the economically viable energy potential
3
Leo Jaymee de Vilas Boas da Silva1, Ivan Felipe Silva dos Santos2, Johnson
4
Herlich Roslee Mensah3, Andriani Tavares Tenório Gonçalves4 and Regina
5
Mambeli Barros5
6
1 Natural Resources Institute. Federal University of Itajubá (UNIFEI - MG). Email: leovilasbo-
7
[email protected].
8
2 Natural Resources Institute. Federal University of Itajubá (UNIFEI - MG). GEER – Renewable Energy
9
Group. Email: [email protected].
10
3 Natural Resources Institute. Federal University of Itajubá (UNIFEI - MG). GEER – Renewable Energy
11
Group. Email: [email protected].
12
4 Institute of management and production. Federal University of Itajubá (UNIFEI - MG). Email: andria-
13
[email protected].
14
5 Natural Resources Institute. Federal University of Itajubá (UNIFEI - MG). GEER – Renewable Energy
15
Group. Email: [email protected].
16
ABSTRACT
17
In Brazil, most Urban Solid Waste (USW) is disposed of in loosely controlled and low-
18
quality dumps and landfills. One of the alternatives for improved management is incin-
19
eration. This largely reduces the amount of waste in sanitary landfills, in turn enabling
20
energy generation, which is encouraged by the Brazilian National Policy on Solid Waste
21
(PNRS). In order to further the debate for the application of incineration plants in Bra-
22
zil, the present study presents an energy and economic analysis. Calculations were car-
23
ried out for different population groups in order to determine the minimum population
24
and the respective waste generation to make an incineration plant viable. The country’s
25
energy potential was also estimated as a function of the energy tariff. The results show
26
that the energy produced through incineration can provide power to an average of 15%
27
of the waste generating population. The viable energy potential in the country was con-
28
firmed only for scenarios with higher energy sales tariffs than those currently applied on
29
the Brazilian market. These results indicate the need for government intervention in
1
30
order to make this technology economically viable, which would in turn reduce inade-
31
quate waste disposal throughout the country.
32
Keywords: Urban Solid Waste; Incinerators; Energy potential and Economic Viability.
33
1. Introduction
34
With an increasing global population, industrial development and an ever-
35
growing demand for consumer goods, these factors have coalesced, resulting in a signif-
36
icant increase of the daily production of Urban Solid Waste (USW) [1,2]. Collection
37
and disposal of USW are among the greatest challenges currently faced in many coun-
38
tries. Solutions must be technically feasible, economically sustainable, socially and le-
39
gally acceptable, as well as environmentally friendly [3].
40
In 2016, two billion tons of USW were generated around the world, resulting in
41
a daily average generation of 0.74 kg/person. With rapid population growth and urbani-
42
zation, global waste generation is expected to increase by as much as 70% compared to
43
2016 [4]. In Brazil, this global trend is also seen, where the daily generated amount
44
grew 39% between 2007 and 2016, totaling 214,405 tons per day [5,6].
45
All of these factors make waste disposal one of the biggest challenges in Brazil.
46
Of the amount collected, only 58.4% was correctly disposed of in landfills in 2016 (the
47
only form of adequate disposal widely used in the country). This is a 0.3% decrease
48
when compared to 2015, when a total of 29.7 million tons of waste were sent to inade-
49
quate units such as dumps and lower-quality landfills [6]. Due to waste management in
50
the country, Green House Gas emissions exceeded 90 million tons of CO2 in 2016.
51
57.5% of these emissions were due to final waste disposal [7]. These data demonstrate
52
how final disposal methods still do not meet the National Solid Waste Policy (PNRS)
53
efforts [8] to do away with landfills and seek appropriate alternatives for USW disposal.
2
54
Leme et al. (2014) [9] compared incineration with landfills (both with and with-
55
out energy recovery) through a life-cycle analysis. According to the authors, incinera-
56
tion is more advantageous than landfills in all environmental matters except for human
57
toxicity potential. Cherubini et al. (2009) [10] classify landfills (also through a life-
58
cycle analysis) as the worst environmental option for USW disposal. One of the options
59
for reducing the wide use of landfills is through incineration. This option is encouraged
60
by the PNRS [8] when applied with energy recovery, provided that the technical and
61
environmental feasibility of the project is ensured [11].
62
The main purpose of the incineration process is to get the oxygen to react with
63
combustible components that are present in the residues (oxygen, carbon, sulfur) at
64
temperatures above 800°C, thus converting their chemical energy into heat. Solid waste
65
has a high calorific value, especially for those found in plastics, paper and rubber [12].
66
In addition to incineration, there are other USW energy conversion routes such
67
as pyrolysis, gasification, anaerobic digestion, ethanol fermentation, dark fermentation,
68
among others [13]. Several studies have compared these types of technology under dif-
69
ferent perspectives, such as economic, energy, environmental [14, 15, 16]. In environ-
70
mental terms, Dong et al. (2018) [15] obtained, through a Life Cycle Analysis (LCA),
71
better results for a gasification plant than those of incineration in all the analyzed as-
72
pects.
73
In energy and economic terms, Tan et al. (2015) [14] obtained better results
74
(higher energy production and lower cost per ton of waste) for incineration than for gas-
75
ification when analyzing waste management in a Malaysian city. Clearly these results
76
may vary depending on the type of waste, as well as the scale and efficiency of the sys-
77
tem and studied region. It is noteworthy that Henriquez (2016) [17], when studying the
78
situation in Brazil, concludes that a system integrating tailings gasification, anaerobic
3
79
digestion of organic matter and recycling is the ideal system in environmental terms,
80
although integrated systems may present less economic viability [18]. Table 1 summa-
81
rizes the advantages and disadvantages of power generation technologies from USW. Table 1: Advantages and disadvantages of key solid waste energy generation technologies. Compiled by the authors based on [12, 13, 18, 19, 20, 21, 22]. Technology Incineration
Advantage •
Small installation areas
•
Energy recovery during USW combustion through electric generation or
Disadvantages •
Potentially high concentration of metals in the ashes
•
cogeneration
Elevated operation and maintenance costs
•
High yield and continuous feed
•
Low generation of noise and odor
chlorinated compounds (such as
•
Plant installation within the city lim-
dioxins and furans) which require
its, thus reducing transport costs
a rigorous gas treatment system
•
Greater reduction of the waste vol-
•
•
Particle emissions, SOx, NOx and
Inviable results for wastes with high moisture content (low calo-
ume to be disposed of in landfills
rific value) or chlorinated compounds (for the risk of toxic gas emissions)
Pyrolysis
•
Produce high-quality fuel (Char, bio-
•
High costs
•
Oily liquid products have high
oil and syngas)
water content due to moisture in
•
Reduce flue gas treatment
feedstock
•
Suitable for carbonous waste
•
Up to 80% energy recovery rate
•
Smaller NOx and SO2 emissions
•
High viscosity of pyrolysis
•
Washing of syngas before combus-
•
High operating, maintenance and
tion
•
Coke
formation
from
liquid
products
capital cost
4
•
Higher quality solid residues; high calorific value products (~38 MJ/kg)
Gasification
•
Ease in transporting liquid fuel
•
Production of fuel gas/oil, which can
•
Tar production
be used for several purposes
•
More suitable for large scale
•
Waste volume reduction up to 90%
•
Easily expanding technology
•
Higher capital and operating costs
•
Can be used for all kinds of wastes
•
Immature, inflexible technology
power plants using Rankine cycle
with risk of failure •
Corrosion of metal tubes during reaction
Anaerobic
•
digestion
Preferred for biomass with high water
•
content •
Higher
Unsuitable for wastes containing less organic matter
composition
of
methane
(CH4) and lower composition of car-
•
Lignin can persist for very extended periods of time to degrade
bon dioxide (CO2) than landfills •
Suitable for organic matter
•
Production of fertilizers
82 83
Incineration plants require an exhaust gas control and treatment system. This is
84
one of its main drawbacks, leading to high costs [12]. Reducing hazardous emissions
85
from incineration is a theme constantly investigated in the literature. As an example, we
86
can cite Silva Filho et al. (2019) [23], who proposed a reactor model that combines py-
87
rolysis and incineration powered by a mixture of USW and Wood Chips, a mixture with
88
high calorific value. With this apparatus, the authors were able to minimize emissions of
89
compounds such as HCl, dioxins and furans, achieving emissions below the legal stand-
90
ards of Brazil and several other international environmental agencies. Such innovations
5
91
are important for the future of incineration and power generation from USW. A com-
92
plete review of the evolution and improvement of gaseous effluent treatment methods in
93
incineration plants over the last decades can be found in [24].
94
As a result of these high costs, this technology is not implemented globally and
95
thus concentrated mainly in three regions of the world: Europe, Asia and North Ameri-
96
ca, as shown in the map seen in Figure 1. Nevertheless, the potential of incineration in
97
regions of the world where this technology is not widespread is very high. To cite the
98
example of the African continent, Scarlat et al. (2015) [25] obtained a potential of 34
99
TWh/y for wastes collected in the region in 2012.
100 101 102
Figure 1: Global distribution of waste incineration in percentage of residual waste after recycling [26].
103 104
Based on these facts, research that assesses energy generation and economic po-
105
tential for USW incineration in regions or countries where it is not widespread, such as
106
Brazil, is relevant because it encourages discussion about this technology, quantifies its
107
benefits, attracts investments and makes it possible to include in planning waste man-
108
agement and energy generation. 6
109
Studies of this type have been carried out by several authors who have investi-
110
gated such matters in Brazil. Santos et al. (2019) [18] evaluated the level of electricity
111
generation costs for incinerating in several scenarios for the city of Sao Jose dos Cam-
112
pos (SP, Brazil), which has a population of approximately 600,000 inhabitants. The au-
113
thors obtained a range of 113.32 to 183.24 USD/MWh, which was considerably higher
114
than other energy recovery options studied by the authors, such as landfill disposal (69.9
115
to 107.7) and solid waste methanization (103.5 to 156), thus demonstrating the difficul-
116
ty in applying economically viability of the incineration practice in Brazil. Values close
117
to these were also obtained by Nordi et al. (2017) [27], who studied various waste man-
118
agement scenarios considering incineration, recycling and anaerobic digestion, in a Bra-
119
zilian city, finding generation costs ranging from 80 to 150 USD/MWh.
120
Lino and Ismail (2017) [28] studied the energetic potential of USW incineration
121
in Campinas (SP, Brazil – a city with a population of approximately 1,200,000 inhabit-
122
ants). They concluded that the electricity generated through this practice could supply as
123
many as 135,680 houses with electricity and generate an income of approximately 5.8
124
million USD per month. According to Dalmo et al. [29], the implantation of USW in-
125
cineration plants in the state of Sao Paulo could generate up to 5.7 TWh, a potential
126
capable of meeting 79% of the state's energy demand. Waste incineration in just 16 ma-
127
jor Brazilian cities could replace 1.8% of total domestic electricity consumption
128
throughout the country [30].
129
An important parameter for incineration is waste material composition. This var-
130
ies depending on the city, level of urbanization, population income, etc. [13, 31]. The
131
average organic matter content in Brazilian waste (51.4% [32]) is a typical level of mid-
132
dle-income countries [33]. Waste of major interest for incineration is USW fractions
133
that have high calorific value, such as plastics, paper, cardboard and rubbers [12]. Or-
7
134
ganic matter has higher moisture content and can hinder the process. However, the use
135
of organic matter in incineration helps to reduce the volume of these residues and has
136
been a scenario considered by several authors studying these techniques in Brazil [12,
137
28].
138
In the context described above, the advantages and limitations of incineration,
139
the importance of adequate waste disposal in Brazil, along with the need to evaluate
140
economic and energy generation potential for USW incineration plants, all fit into the
141
objectives in this study. The objective here is to evaluate the viability of the total energy
142
potential and the viable energy potential of USW incineration in Brazil and, based on
143
the results obtained, discuss the opportunities and limitations of incineration implemen-
144
tation in the country. This paper brings forth a new proposal in that the estimation of
145
energy potential and economic viability of incineration can be seen as a function of
146
population, with the objective of calculating the viable energy potential in the country.
147
The methodology can be replicated in other regions or for other wastes, promoting im-
148
portant discussions about energy planning and waste management.
149
2. Methodology
150
The methodology applied is based on the energy and economic calculation of the
151
implantation of incineration plants for different population sizes, obtain a complete
152
analysis of the parameters in function of the population, and estimate a minimum popu-
153
lation that makes such a venture feasible. Once this population is defined, it is possible
154
to determine the total potential of economically viable energy derived from the pro-
155
posed incineration plants throughout Brazil. This methodology was followed by studies
156
such as Barros et al. (2014) [34] (for disposal of USW in landfills), Luz et al. (2015)
157
[35] (for gasification of USW) and Bernal et al. (2017) [36] (in their studies on the rela-
8
158
tion of a ton of ground cane and the economic viability of a biogas plant from the sugar
159
cane vinasse). The following section details each step of this methodology.
160
2.1. Population definitions and calculation of waste generation
161 162 163
Calculations were performed for nine sets of population data (2,000; 5,000;
164
10,000; 20,000; 50,000; 100,000; 500,000; 1,000,000; and 3,000,000) established based
165
on the upper limits of the population sizes defined by the Brazilian Institute of Geogra-
166
phy and Statistics [37]. The daily waste generation for each population range was calcu-
167
lated using Equation 1. Due to the lack of more detailed data, and to the fact that present
168
work calculations do not refer to a specific locality but rather to population ranges, the
169
Brazilian average gravimetric composition (presented in Table 2) was used to calculate
170
the production of each type of residue in each analyzed population class (using Equation
171
2). Table 2: Average gravimetric composition of urban solid waste in Brazil. Source: Adopted from [32].
Wastes
Percentage (%)
Metals
2.9
Steel
2.3
Aluminum
0.6
Paper, cardboard and
13.1
tetrapak Total plastic
13.5
Plastic film
8.9
Rigid Plastic
4.6
Glass
2.4
Organic matter
51.4
Others
16.7
9
Table 2: Average gravimetric composition of urban solid waste in Brazil. Source: Adopted from [32].
Total
100
172 173
=
∙ (%) 1000 =
∙
(1)
(2)
174 175
Where: R = waste production (t/day); Pop = population and IG = per capita waste genera-
176
tion index (kg/person day), Fi = fraction of each type of residue removed from the grav-
177
imetric composition (Table A of supplementary materials – [38]) and Ri = daily produc-
178
tion of each type of residue. The IG index was obtained through data from the National
179
Sanitation Information System (SNIS) and can be seen in Table A of supplementary
180
materials [38]. Only solid waste with greater calorific value of the following substances
181
were considered in the calculations: organic matter, plastic, paper, cardboard and tetra-
182
pak.
183 184
2.2. Energy calculations
185
Based on heat-generating values for each type of residue presented in Table 3,
186
the total heat value (Equations 3 and 4) was calculated [12, 18]. The available power
187
and the energy produced by the incinerator were calculated using Equation 5 [9] and 6
188
[39].
189
=
∙
∙
(3)
190
10
(4)
= =
∙ η ∙ R ∙ k
!=
∙
"
(5)
∙ 8,760
(6)
191 192
Where: LCV = lower calorific value of each type of residue in kcal / kg (Table 3); k1 =
193
conversion constant from kcal/kg to kJ/kg = 4.184; LCVi calorific value contained in
194
each RSU fraction in kJ / kg; LCVTotal = total calorific value of the residue in kJ/kg; η =
195
electric recovery of all energy generation systems from incineration = 22% (obtained in
196
[12]); k2 = unit adjustment constant so that the resulting power is in kW = 0.01157; P =
197
electric power in kW; 8,760 = number of hours per year; CF = capacity factor adopted
198
as being equal to 80% [12] and E = electric energy produced in kWh/year. Table 3: Lower calorific value. Source: Adapted from [12]. USW
LCV on Wet basis kcal/kg
Moisture (%)
Organic matter
712
25
Plastic
8,193
3
Paper and
2,729
5
cardboard 199 200
2.3. Economic Calculations
201
For the economic considerations of this study, two viability evaluation parame-
202
ters were used for each population size: Net Present Value (NPV) and Levelized Cost of
203
Electricity (LCOE). In addition, investment costs corresponding to the acquisition and
204
installation of the equipment was also considered.
205
Equation 7 allows the calculation of NPV. When NPV values are positive, the
206
investment proposal is economically viable. Additionally, the greater the NPV, the more
207
attractive the proposal [40]. The LCOE (Equation 8) represents the minimum rate of 11
208
sale of energy that makes the investment economically viable. In other words, if the
209
energy sales tariff is higher than the LCOE, then the proposal is economically viable
210
[41, 42]. =
(! ∙ ') −
0! =
n
o&m
(1 + i)
∑ ∑
–
(6)
2
(1 + 3)2 !2 (1 + 3)2
(7)
211 212
Where: Cn = cost of the enterprise per year in USD; i = interest rate; I = initial
213
investment in USD; Co & m = cost of operation and maintenance in USD/year; t = en-
214
ergy sales tariff in USD/MWh; m = project life and n = year of analysis.
215
The value adopted for interest rate i corresponds to the current value of the min-
216
imum rate obtained at the Central Bank of Brazil, equal to 6.5% per year with a risk
217
factor of 2.5% [43]. The costs of installation I of the enterprise were obtained through
218
Equation 8 as a function of the electric power in kW according to [44]. = 15,797 ∙
6.8
(8)
219
The costs for operation and maintenance (Co & m) were adopted as 4% of the
220
initial investment (according to [44]). For the calculation of annual revenues, the energy
221
sales tariff was set at 51.01 USD/MWh: the A-4 generation auction ceiling for the Bra-
222
zilian National Electric Energy Agency (ANEEL) for gas-fired thermal power plants in
223
2018 [45].
224
2.4. Potential calculations and sensitivity analyses
225
In order to achieve economic viability (NPV> 0 and LCOE
226
to determine the minimum population (Popmin) that would contribute to the total amount
227
of waste sent to the incinerator. The population classes and population distribution by 12
228
size of Brazilian municipalities presented by [37] were then used to adjust a regression
229
curve to determine the percentage of resident population, up to a certain population val-
230
ue of Y. This curve is shown in Figure 2. Subtracting this curve from the value of
231
100%, it is possible to determine the municipalities with a population higher than a cer-
232
tain value (parameter here called %Pop) (According to Equation 9).
233
234 235
Figure 2: Distribution of the percentage of Brazilian population, by population bands.
236
%
= 100 − 9 = 100 − (13.606 ∙ ln<
= − 112.28)
(9)
237 238
Where: Y = Percentage of the Brazilian population that inhabits cities with
239
populations lesser than a given population; % Pop = Percentage of the Brazilian popula-
240
tion that inhabits cities with a population greater than a given Pop population.
241
The minimum to obtain viability (Popmin) can be used in Equation (9) to deter-
242
mine the percentage of the population residing in cities with populations greater than 13
243
(Popmin). With this result, and considering the total Brazilian population (209.3 million),
244
the total population residing in cities where urban solid waste incineration plants are
245
economically viable, was calculated by applying the energy equations to this value
246
(Equations 3 to 6), thus resulting in the total viable energy potential in the country.
247
Finally, a sensitivity analysis was conducted with the objective of observing the
248
impact of the increase of the energy tariff on Popmin and the viable potential of every
249
country, a result that furthers relevant discussions about the Brazilian energy scenario.
250
3. Results
251
3.1. Energy calculations
252
Through Equation 5, annual energy production values for each population range
253
were obtained and can be seen in Table 4. With a population of 1,000,000 inhabitants,
254
the installed capacity of waste incineration is 14.1 MW, equal to a small hydropower
255
plant (which in Brazil is projected between 5 and 30 MW [46]). According to Fernandes
256
(2016) [47], who studied energy recovery for landfills in several Brazilian cities, the
257
average power generated from biogas is 5 W/city inhabitant. Thus, a city with 1,000,000
258
inhabitants would have an installed capacity of 5 MW. It is thus observed that the power
259
of the incinerator is about 2.8 times higher than that generated by sanitary landfill bio-
260
gas for the same waste stream. The energy generated by this same population reaches
261
almost 100 GWh/year. Given that the average residential consumption in Brazil is 160
262
(kWh/month) [48] and considering an average of three residents per household [49], one
263
can conclude that the energy produced could power 51,607 residences or 154,820 inhab-
264
itants; that is, 15.4% of the population. These results demonstrate the substantial energy
265
potential of incineration. Table 4: Energy and power production Population
Waste
Power
Energy
14
(inhabitants)
generation (t/d)
(kW)
(MWh/y)
2,000
1.4
26.8
187.5
5,000
3.4
66.9
468.8
10,000
6.9
133.8
937.6
20,000
13.7
267.6
1,875.2
50,000
35.1
684.1
4,794.4
100,000
70.2
1,368.3
9,588.9
500,000
331.5
6,461.3
45,280.9
1,000,000
725.4
14,138.9
99,085.4
3,000,000
2,386.8
46,521.6
326,023.1
266 267
These data show that incineration can be an option for contributing to a greater
268
portion of the national energy matrix, which currently suffers from rising levels of
269
thermal generation from fossil fuels and recurring reductions in the volumes of hydroe-
270
lectric reservoirs due to the scarcity of rainfall. In addition, the growth of large-scale
271
incineration on the national energy grid would provide support for the insertion of in-
272
termittent renewable sources, which require sources that provide stability to the system.
273
3.2. Economic Analysis
274
The economic results are provided in Table 5. When analyzing Table 5, it can be
275
noticed that for the current energy sale price values, all population sizes present nega-
276
tive NPV results, thus making the investment inviable; this is due to the high investment
277
costs related to construction. This is mainly caused by the emission control and treat-
278
ment stations [12]. Table 5: Net Present Value (NPV) and LCOE Results Population
Investment
Operation
Revenues
(inhabitants)
(USD)
and mainte-
(USD/y)
NPV (USD)
nance costs
LCOE
Unit cost
(USD/
(USD/kW)
MWh)
(USD/y) 2,000
269,015.8
10,760.6
14,424.4
-278.651,3
235.4
10,037.9
15
5,000
570,280.6
22,811.2
36,060.9
-561.398,2
199.6
8,524.4
10,000
1,006,776.8
40,271.1
72,121.8
-945.876,1
176.2
7,524.5
20,000
1,777,369.8
71,094.8
144,243.5
-1.579.416,3
155.5
6,641.9
50,000
3,837,882.4
153,515.3
368,804.4
-3.103.947,0
131.3
5,610.1
100,000
6,775,420.4
271,016.8
737,608.8
-5.017.254,0
115.9
4,951.7
500,000
24,195,595.8
967,823.8
3,483,152.8
13.378.386,6
3,744.6 87.7
279 280
Table 5 shows that although the NPV became increasingly negative as the popu-
281
lation increases (due to the increase in initial investment), LCOE values decreased ac-
282
cording to the population size and demonstrated that the required rate for viability re-
283
duces as the scale of the enterprise increases. Using the LCOE and population data, one
284
can construct Figure 3, where it is observed that the behavior of LCOE as a function of
285
population best fits a logarithmic curve, presenting a high correlation coefficient (R² =
286
0.968). The trend curve can be used for the initial LCOE estimation for incineration
287
plants in Brazil, which helps in the elaboration of economic studies and the potential of
288
these plants in the country while collaborating with the development of this technology.
16
289 290
Figure 3: Variation of LCOE with population
291 292
The minimum LCOE value was 61.5 USD/MWh (for 3 million inhabitants),
293
still 10.5 more than the 51.0 USD/MWh tariff for the sale of thermoelectric power
294
plants in Brazil. Therefore, a higher specific tariff for USW incineration energy sales in
295
Brazilian bidding processes would need to be created, which would consider LCOE
296
variations according to the population and installed power so that incineration plants
297
could become economically viable. In this way, the curve in Figure 3 can be used as an
298
auxiliary tool to define such tariffs.
299
In analyzing the unit cost data, it can be seen that these rates are generally higher
300
than those of other renewable energy sources such as wind power (around 1,360
301
USD/kW) and small hydroelectric plants (1,670 USD/kW) [50]. Unit incineration costs
302
are only beginning to approach those of biogas (around 2,700 USD/kW) for populations
303
of around 3 million. This also reinforces the high costs of incineration.
17
304
As presented by Santos et al. (2019) [18] and previously discussed, USW incin-
305
eration generates more energy than other energy recovery options. By generating more
306
energy from waste, less fossil fuel energy will be required and a smaller amount of CO2
307
will be emitted into the atmosphere. In addition, incineration drastically reduces USW
308
volume, thereby reducing disposal in landfills and generating geographical preservation
309
as well as reducing the environmental impacts of these structures. The creation of inter-
310
municipal consortia, where the waste from nearby cities is sent to a single waste treat-
311
ment unit, can contribute not only to the increase of energy production in these plants,
312
but also to waste management throughout an entire region. Therefore, it is necessary to
313
create mechanisms that convert the environmental benefits of this technology into eco-
314
nomic ones, thereby increasing the revenues of these projects and facilitating their fi-
315
nancial viability.
316
Another way to increase the financial attractiveness of incineration (especially in
317
smaller cities) is the application of the distributed energy generation market. This mar-
318
ket has been developing recently throughout the country due to policies adopted by
319
ANEEL, both by Resolution No. 482/2012 [51] and by Resolution No. 687/2015 [52].
320
The Resolution stipulates that projects with a capacity of up to 3 MW may benefit from
321
this policy. In turn, this allows an entrepreneur to invest in one form of generation and
322
use the energy produced to reduce the demand of other units or companies that are reg-
323
istered under the same document.
324
Entrepreneur income will grow, due to the economy with the purchase of energy
325
from the distributor, whose tariff is higher than the sale in government biddings. Ac-
326
cording to the Brazilian Association of Energy Distributors (ABRADEE) [53], the value
327
of the energy tariff in this market is close to 165 USD/MWh. Comparing this value to
328
the LCOE values presented in Table 5, populations of up to 220,000 inhabitants could
18
329
apply USW incineration in the distributed generation market. Viability in this market
330
would be obtained for population values between 20,000 and 220,000 inhabitants.
331
It is worth mentioning that the calculations of the present study were carried out
332
without considering importation taxes levied on the equipment. Therefore, the creation
333
of a national industry that allows the localized production of this technology, reducing
334
the initial investment costs, is fundamental to the development of the incineration plants
335
within Brazilian borders. The creation of this industry can also collaborate with the gen-
336
eration of jobs and development of the national economy.
337 338
3.3. Sensitivity Analysis
339
The impacts of the increased energy sales tariff on the energy and economic po-
340
tential of the incineration were analyzed using NPV as a parameter. The NPV ratio
341
curves by population were calculated for different values of energy sales tariffs from 51
342
USD/MWh (current value) to 129 USD/MWh at a rate of 26 USD/MWh. Figure 4 illus-
343
trates how such a variation occurs.
344 345
Figure 4: Effect of the variation of the energy sales tariff on the NPV. 19
346
It is observed that higher values for energy sales tariff result in a more positively
347
inclined curve. This indicates greater attractiveness for investment. The tariffs stipulated
348
here exceed the values adopted by ANEEL in energy auctions, thus making these sce-
349
narios consider the government's actions which encourage incineration rates. From Fig-
350
ure 4, the minimum population (Popmin) values for incineration viability were obtained
351
for each of the tariffs analyzed. The relationship between Popmin and T is presented in
352
Table 6. For T = 51 USD/MWh, no population size attained viable results. With the
353
Popmin values, one can calculate the population that could be benefited only by economi-
354
cally viable incineration plants (through Equation 9) and the feasible energy potential in
355
the country (Table 6). Table 6: Minimum viable population per energy sale tariff Minimum
Population
Population
Economically viable
viable
receiving
Receiving
energy potential in
Population
Power
Power (% of total)
the country
(inhabitants)
(inhabitants)
77
1,410,141
40,927,385
19.6
4,430,308.67
103
294,713
85,335,583
40.9
9,239,716.57
129
85,312
120,502,793
57.8
13,048,325.34
Energy sale tariff (USD/MWh)
(MWh / y)
356 357
With tariff increases, the increase in the population who would receive power is
358
significant, showing an average increase of USD 1/MWh. This, in turn, would result in
359
an increase of the viable energy potential throughout the country by an average of 165
360
GWh/year, demonstrating the overall impact of the energy tariff on a national level.
361
In the best scenarios (T = 129 USD/MWh), incineration is feasible for more than
362
half of the Brazilian population (more than 120 million inhabitants). As the per capita
363
waste generation index in Brazil is close to 1.03 kg/person/day [6], the total generation
364
of waste in this scenario, which would not be sent to landfills. That would add up to
365
nearly 123.6 thousand tons/year. This is a considerable reduction in the areas required 20
366
for waste burial while also avoiding possible soil and groundwater contamination
367
caused by the disposal of waste in incorrect locations. In addition, the country would
368
have a new energy source that could replace the production of energy from fossil fuels.
369
Using the same values of average energy per residence and inhabitants per resi-
370
dence applied in section 3.1 (160 kWh/month and 3 inhabitants/residence – [48, 49]), it
371
is seen that economically, the viable energy potential in this scenario could supply a
372
population of 20 million inhabitants; that is, almost 10% of the country’s total popula-
373
tion.
374 375
4. Conclusions
376
This study sought to analyze energy generation through implantation of USW
377
incineration plants in Brazil, and analyze the economic feasibility through a function of
378
the waste generation population. Incineration is encouraged by the National Solid Waste
379
Policy of Brazil and stands out as a great alternative for final disposal of USW. This can
380
be applied to reduce the quantity and land-area occupied by landfills, which are the pre-
381
dominant disposal technique in the country and consuming a significant area and gener-
382
ating pollution threats.
383
The results showed how incineration is advantageous from an energy generation
384
perspective, and that it is able to supply more than 15% of the population that contrib-
385
utes waste to the plants. The power generated by an incinerator is about three times
386
greater than that which could be generated by landfill biogas for the same waste mass.
387
In economic terms, incineration does not yet yield good results. For the energy
388
sale tariff values currently used on the Brazilian energy market, financial viability was
389
not verified. This is due to the elevated installation costs, along with operational and
390
maintenance costs for the equipment required by the incineration plants, which is 21
391
caused by the need for a strict gas control and treatment system in these plants. Through
392
the sensitivity analysis, the energy sales tariff had a significant impact on the economic
393
viability of these plants and on the overall viable energy potential. This energy potential
394
grows on average by 165 GWh per year for each increase of 1 USD/MWh in the energy
395
sales tariff.
396
Given the impact which such economic factors exercise on energy potential for
397
incineration in Brazil, it is fundamental that municipal, state and federal government
398
work to establish a basis for large-scale implantation of this technology, either through
399
incentives for production of technology at the national level, an increased energy sales
400
tariffs values, or through mechanisms that convert the environmental benefits of this
401
technology into economic benefits.
402
The methodology developed in this paper includes calculations for energy and
403
economic potential which are elaborated according to population size and enable the
404
calculation of total viable energy potential throughout the country of Brazil, can be ap-
405
plied in other regions and scenarios, as well as for other types of waste. In doing so, the
406
extension of this methodology will thereby help studies and further discussion on ener-
407
gy use from waste in general.
408
Acknowledgements
409
We wish to thank the Coordination for the Improvement of Higher Education Personnel
410
(Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, CAPES; in Portu-
411
guese) for the support given by granting Doctor of Science scholarships to Ivan Felipe
412
Silva dos Santos and Andriani Tavares Tenório Gonçalves and Master of Science schol-
413
arships to Johnson Herlich Roslee Mensah. The authors would like to thank
414
the Brazilian National Council for Scientific and Technological Development (Conselho
415
Nacional de Desenvolvimento Científico e Tecnológico, CNPq; in Portuguese), for 22
416
granting a productivity in research scholarship to Prof. Regina Mambeli Barros (PQ2,
417
Process number: 301986/2015-0).
418
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31
Energy potential of MSW incineration was calculated in function of the population; Economic feasibility of MSW incineration in Brazil was evaluated and discussed; Economic feasible energy potential of MSW incineration in Brazil was estimated; A sensitivity analysis was conducted in function of energy sale rate.
Ms. Ref. No.: RENE-D-19-01938 Title: Incineration of Municipal Solid Waste in Brazil: An Analysis of the economically viable energy potential Renewable Energy
Dear Soteris Kalogirou, PhD Editor-in-Chief Renewable Energy
Based on the reviewers' comments, we made the following revisions. We have carefully revised the entire manuscript in response to the reviewers. Reviewer #1 1. The authors made an effort to study the energy and economic potential for the incineration of MSW in Brazil. I would suggest authors consider below modifications for easy readability and to improve the article further. The authors are grateful for the reviewers' complimentary comments and report that they endeavored to respond to all of their comments. 2. I suggest authors proofread for spelling and grammatical mistakes. To improve the writing of the article, the authors submitted it to the service of a native English proofreader. The authors understand that the new version of the manuscript is superior to the previous one. 3. Please insert a Graphical Abstract. The authors added a graphical abstract, as suggested by the reviewer. As the results were many, the authors focused on the main conclusions of the sensitivity analysis regarding the potentially served population and energy potential for constructing the figure. 4. What are the best approach to convert MSW into bioenergy, thermochemical (pyrolysis, combustion, gasification) or biochemical, and why? This issue is not a simple answer question, as it depends on the focus (environmental, energy, economic) and a variety of factors such as waste composition, scale, region analyzed (like costs, type and volume of waste and availability of labor vary from region to region), among others. However, to discuss this issue in our article, we insert two paragraphs presenting the results of several works that indicate the best technology according to the analyzed
approach (environmental, energy, etc.) (See lines 68 to 82). A table containing the advantages and disadvantages of each technology was also compiled by the authors based on seven different references and inserted in the introduction (See table 1). 5. Lines 75-87: Please cite the possibility the use of co-utilization of municipal solid waste with biomass as wood chips to minimize toxic gaseous emissions as in the following publication Da Silva Filho et al. (2019), Renewable Energy,
Volume
141,
October
2019,
Pages
402-410
~ https://doi.org/10.1016/j.renene.2019.04.032. Besides, the migration of chlorine can be controlled depending on the process conditions using a novel pilot-scale system combining pyrolysis and combustion processes. Thus, I think you need to highlight this potential by writing a sentence in the introduction of your manuscript along with the previous paper, which could be used to improve the manuscript. The authors appreciate the reviewer's suggestion and understand that the work indicated is of high relevance. For this reason, they inserted a portion of text between lines 86 and 94 to mention such potential in the context of the reduction of emissions generated by the MSW incineration process. 6. MSW characteristics influence the results of this study, but there is scarce information on MSW except for LHV in Table 1. To broaden discussions on MSW characteristics in the new version of the article, the authors added Table 2 to the methodology, which contains information on the gravimetric composition of waste in Brazil. Also, they added a paragraph between lines 130 and 137 of the introduction of the article discussing aspects such as the importance of waste composition on the incineration process. This paragraph is presented below: “An important parameter for incineration is waste material composition. This var-ies depending on the city, level of urbanization, population income, etc. [13, 31]. The average organic matter content in Brazilian waste (51.4% [32]) is a typical level of mid-dle-income countries [33]. Waste of major interest for incineration is USW fractions that have high calorific value, such as plastics, paper, cardboard and rubbers [12]. Organic matter has higher moisture content and can hinder the process. However, the use of or-ganic matter in incineration helps to reduce the volume of these residues and has been a scenario considered by several authors studying these techniques in Brazil [12, 28]"
7. Line 257: Instead of "Table 3 below" simply use Table 3. The authors have corrected this mistake.
Reviewer #2: 1. The manuscript is very well prepared, and technical quality and presentation
of
the
results
are
fairly
good.
The results/outcomes may be useful for decision-makers in Brasil. The authors thank the reviewers for their complimentary comments. 2. Reference style> Indicate references by numbers in square brackets in line with the text. Please check the guide for authors. This error was corrected by the authors, as suggested by the reviewer and the journal rules. 3. The writing style may be improved. To improve the writing style of the article, the authors submitted this to the service of a native English proofreader. The authors understand that the new version of the text is superior to the previous one. 4. Table 1 caption should be corrected. Lower calorific power?! The authors corrected this mistake. 5. The literature review may be extended. See e.g. 10.1016/j.rser.2015.05.067 10.1016/j.renene.2019.03.022 - 10.1177/0734242X17705721. The authors thank the article suggestions s by the reviewer and report that two of them used to extend the literature review (Scarlat et al., 2015 and Nordi et al., 2017). The authors have also inserted several other articles by other authors on this topic. In the new version of the article, the introductory chapter (in which the literature review is inserted) has 1778 words, a 57 % increase over the previous value (1,132 ). The increase in the number of references in the article was also significant, from 38 to 53 (an increase of 39 %). The authors understand that the new version of the article has a much higher quality literature review than the previous one. 6. The novelty is not clearly discussed. Please clearly state your news results. The novelty of this article lies in the estimation of the country's energy potential and economic viability as a function of the population in order to define the viable energy potential in the country using a methodology that can be replicated in other regions or for other waste, promoting important discussions about the
energy planning and waste management in Brazil. This remark was added in the last paragraph of the introduction of the article. The manuscript has now been resubmitted to your journal. We look forward to hearing from you and would like to thank you for all your input so that we may successfully publish our manuscript. We remain at your disposal for any further corrections. Yours sincerely,
Ivan Felipe Silva dos Santos Corresponding Author
S0960-1481(19)31631-3
DOI:
https://doi.org/10.1016/j.renene.2019.10.134
Reference:
RENE 12503
To appear in:
Renewable Energy
Received Date: 30 April 2019 Revised Date:
14 August 2019
Accepted Date: 24 October 2019
Please cite this article as: da Silva LJdVB, dos Santos IFS, Mensah JHR, Gonçalves AndrianiTavaresTenó, Barros RM, Incineration of municipal solid waste in Brazil: An analysis of the economically viable energy potential, Renewable Energy (2019), doi: https://doi.org/10.1016/ j.renene.2019.10.134. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier Ltd.
1
Incineration of Municipal Solid Waste in Brazil: An Analysis
2
of the economically viable energy potential
3
Leo Jaymee de Vilas Boas da Silva1, Ivan Felipe Silva dos Santos2, Johnson
4
Herlich Roslee Mensah3, Andriani Tavares Tenório Gonçalves4 and Regina
5
Mambeli Barros5
6
1 Natural Resources Institute. Federal University of Itajubá (UNIFEI - MG). Email: leovilasbo-
7
[email protected].
8
2 Natural Resources Institute. Federal University of Itajubá (UNIFEI - MG). GEER – Renewable Energy
9
Group. Email: [email protected].
10
3 Natural Resources Institute. Federal University of Itajubá (UNIFEI - MG). GEER – Renewable Energy
11
Group. Email: [email protected].
12
4 Institute of management and production. Federal University of Itajubá (UNIFEI - MG). Email: andria-
13
[email protected].
14
5 Natural Resources Institute. Federal University of Itajubá (UNIFEI - MG). GEER – Renewable Energy
15
Group. Email: [email protected].
16
ABSTRACT
17
In Brazil, most Urban Solid Waste (USW) is disposed of in loosely controlled and low-
18
quality dumps and landfills. One of the alternatives for improved management is incin-
19
eration. This largely reduces the amount of waste in sanitary landfills, in turn enabling
20
energy generation, which is encouraged by the Brazilian National Policy on Solid Waste
21
(PNRS). In order to further the debate for the application of incineration plants in Bra-
22
zil, the present study presents an energy and economic analysis. Calculations were car-
23
ried out for different population groups in order to determine the minimum population
24
and the respective waste generation to make an incineration plant viable. The country’s
25
energy potential was also estimated as a function of the energy tariff. The results show
26
that the energy produced through incineration can provide power to an average of 15%
27
of the waste generating population. The viable energy potential in the country was con-
28
firmed only for scenarios with higher energy sales tariffs than those currently applied on
29
the Brazilian market. These results indicate the need for government intervention in
1
30
order to make this technology economically viable, which would in turn reduce inade-
31
quate waste disposal throughout the country.
32
Keywords: Urban Solid Waste; Incinerators; Energy potential and Economic Viability.
33
1. Introduction
34
With an increasing global population, industrial development and an ever-
35
growing demand for consumer goods, these factors have coalesced, resulting in a signif-
36
icant increase of the daily production of Urban Solid Waste (USW) [1,2]. Collection
37
and disposal of USW are among the greatest challenges currently faced in many coun-
38
tries. Solutions must be technically feasible, economically sustainable, socially and le-
39
gally acceptable, as well as environmentally friendly [3].
40
In 2016, two billion tons of USW were generated around the world, resulting in
41
a daily average generation of 0.74 kg/person. With rapid population growth and urbani-
42
zation, global waste generation is expected to increase by as much as 70% compared to
43
2016 [4]. In Brazil, this global trend is also seen, where the daily generated amount
44
grew 39% between 2007 and 2016, totaling 214,405 tons per day [5,6].
45
All of these factors make waste disposal one of the biggest challenges in Brazil.
46
Of the amount collected, only 58.4% was correctly disposed of in landfills in 2016 (the
47
only form of adequate disposal widely used in the country). This is a 0.3% decrease
48
when compared to 2015, when a total of 29.7 million tons of waste were sent to inade-
49
quate units such as dumps and lower-quality landfills [6]. Due to waste management in
50
the country, Green House Gas emissions exceeded 90 million tons of CO2 in 2016.
51
57.5% of these emissions were due to final waste disposal [7]. These data demonstrate
52
how final disposal methods still do not meet the National Solid Waste Policy (PNRS)
53
efforts [8] to do away with landfills and seek appropriate alternatives for USW disposal.
2
54
Leme et al. (2014) [9] compared incineration with landfills (both with and with-
55
out energy recovery) through a life-cycle analysis. According to the authors, incinera-
56
tion is more advantageous than landfills in all environmental matters except for human
57
toxicity potential. Cherubini et al. (2009) [10] classify landfills (also through a life-
58
cycle analysis) as the worst environmental option for USW disposal. One of the options
59
for reducing the wide use of landfills is through incineration. This option is encouraged
60
by the PNRS [8] when applied with energy recovery, provided that the technical and
61
environmental feasibility of the project is ensured [11].
62
The main purpose of the incineration process is to get the oxygen to react with
63
combustible components that are present in the residues (oxygen, carbon, sulfur) at
64
temperatures above 800°C, thus converting their chemical energy into heat. Solid waste
65
has a high calorific value, especially for those found in plastics, paper and rubber [12].
66
In addition to incineration, there are other USW energy conversion routes such
67
as pyrolysis, gasification, anaerobic digestion, ethanol fermentation, dark fermentation,
68
among others [13]. Several studies have compared these types of technology under dif-
69
ferent perspectives, such as economic, energy, environmental [14, 15, 16]. In environ-
70
mental terms, Dong et al. (2018) [15] obtained, through a Life Cycle Analysis (LCA),
71
better results for a gasification plant than those of incineration in all the analyzed as-
72
pects.
73
In energy and economic terms, Tan et al. (2015) [14] obtained better results
74
(higher energy production and lower cost per ton of waste) for incineration than for gas-
75
ification when analyzing waste management in a Malaysian city. Clearly these results
76
may vary depending on the type of waste, as well as the scale and efficiency of the sys-
77
tem and studied region. It is noteworthy that Henriquez (2016) [17], when studying the
78
situation in Brazil, concludes that a system integrating tailings gasification, anaerobic
3
79
digestion of organic matter and recycling is the ideal system in environmental terms,
80
although integrated systems may present less economic viability [18]. Table 1 summa-
81
rizes the advantages and disadvantages of power generation technologies from USW. Table 1: Advantages and disadvantages of key solid waste energy generation technologies. Compiled by the authors based on [12, 13, 18, 19, 20, 21, 22]. Technology Incineration
Advantage •
Small installation areas
•
Energy recovery during USW combustion through electric generation or
Disadvantages •
Potentially high concentration of metals in the ashes
•
cogeneration
Elevated operation and maintenance costs
•
High yield and continuous feed
•
Low generation of noise and odor
chlorinated compounds (such as
•
Plant installation within the city lim-
dioxins and furans) which require
its, thus reducing transport costs
a rigorous gas treatment system
•
Greater reduction of the waste vol-
•
•
Particle emissions, SOx, NOx and
Inviable results for wastes with high moisture content (low calo-
ume to be disposed of in landfills
rific value) or chlorinated compounds (for the risk of toxic gas emissions)
Pyrolysis
•
Produce high-quality fuel (Char, bio-
•
High costs
•
Oily liquid products have high
oil and syngas)
water content due to moisture in
•
Reduce flue gas treatment
feedstock
•
Suitable for carbonous waste
•
Up to 80% energy recovery rate
•
Smaller NOx and SO2 emissions
•
High viscosity of pyrolysis
•
Washing of syngas before combus-
•
High operating, maintenance and
tion
•
Coke
formation
from
liquid
products
capital cost
4
•
Higher quality solid residues; high calorific value products (~38 MJ/kg)
Gasification
•
Ease in transporting liquid fuel
•
Production of fuel gas/oil, which can
•
Tar production
be used for several purposes
•
More suitable for large scale
•
Waste volume reduction up to 90%
•
Easily expanding technology
•
Higher capital and operating costs
•
Can be used for all kinds of wastes
•
Immature, inflexible technology
power plants using Rankine cycle
with risk of failure •
Corrosion of metal tubes during reaction
Anaerobic
•
digestion
Preferred for biomass with high water
•
content •
Higher
Unsuitable for wastes containing less organic matter
composition
of
methane
(CH4) and lower composition of car-
•
Lignin can persist for very extended periods of time to degrade
bon dioxide (CO2) than landfills •
Suitable for organic matter
•
Production of fertilizers
82 83
Incineration plants require an exhaust gas control and treatment system. This is
84
one of its main drawbacks, leading to high costs [12]. Reducing hazardous emissions
85
from incineration is a theme constantly investigated in the literature. As an example, we
86
can cite Silva Filho et al. (2019) [23], who proposed a reactor model that combines py-
87
rolysis and incineration powered by a mixture of USW and Wood Chips, a mixture with
88
high calorific value. With this apparatus, the authors were able to minimize emissions of
89
compounds such as HCl, dioxins and furans, achieving emissions below the legal stand-
90
ards of Brazil and several other international environmental agencies. Such innovations
5
91
are important for the future of incineration and power generation from USW. A com-
92
plete review of the evolution and improvement of gaseous effluent treatment methods in
93
incineration plants over the last decades can be found in [24].
94
As a result of these high costs, this technology is not implemented globally and
95
thus concentrated mainly in three regions of the world: Europe, Asia and North Ameri-
96
ca, as shown in the map seen in Figure 1. Nevertheless, the potential of incineration in
97
regions of the world where this technology is not widespread is very high. To cite the
98
example of the African continent, Scarlat et al. (2015) [25] obtained a potential of 34
99
TWh/y for wastes collected in the region in 2012.
100 101 102
Figure 1: Global distribution of waste incineration in percentage of residual waste after recycling [26].
103 104
Based on these facts, research that assesses energy generation and economic po-
105
tential for USW incineration in regions or countries where it is not widespread, such as
106
Brazil, is relevant because it encourages discussion about this technology, quantifies its
107
benefits, attracts investments and makes it possible to include in planning waste man-
108
agement and energy generation. 6
109
Studies of this type have been carried out by several authors who have investi-
110
gated such matters in Brazil. Santos et al. (2019) [18] evaluated the level of electricity
111
generation costs for incinerating in several scenarios for the city of Sao Jose dos Cam-
112
pos (SP, Brazil), which has a population of approximately 600,000 inhabitants. The au-
113
thors obtained a range of 113.32 to 183.24 USD/MWh, which was considerably higher
114
than other energy recovery options studied by the authors, such as landfill disposal (69.9
115
to 107.7) and solid waste methanization (103.5 to 156), thus demonstrating the difficul-
116
ty in applying economically viability of the incineration practice in Brazil. Values close
117
to these were also obtained by Nordi et al. (2017) [27], who studied various waste man-
118
agement scenarios considering incineration, recycling and anaerobic digestion, in a Bra-
119
zilian city, finding generation costs ranging from 80 to 150 USD/MWh.
120
Lino and Ismail (2017) [28] studied the energetic potential of USW incineration
121
in Campinas (SP, Brazil – a city with a population of approximately 1,200,000 inhabit-
122
ants). They concluded that the electricity generated through this practice could supply as
123
many as 135,680 houses with electricity and generate an income of approximately 5.8
124
million USD per month. According to Dalmo et al. [29], the implantation of USW in-
125
cineration plants in the state of Sao Paulo could generate up to 5.7 TWh, a potential
126
capable of meeting 79% of the state's energy demand. Waste incineration in just 16 ma-
127
jor Brazilian cities could replace 1.8% of total domestic electricity consumption
128
throughout the country [30].
129
An important parameter for incineration is waste material composition. This var-
130
ies depending on the city, level of urbanization, population income, etc. [13, 31]. The
131
average organic matter content in Brazilian waste (51.4% [32]) is a typical level of mid-
132
dle-income countries [33]. Waste of major interest for incineration is USW fractions
133
that have high calorific value, such as plastics, paper, cardboard and rubbers [12]. Or-
7
134
ganic matter has higher moisture content and can hinder the process. However, the use
135
of organic matter in incineration helps to reduce the volume of these residues and has
136
been a scenario considered by several authors studying these techniques in Brazil [12,
137
28].
138
In the context described above, the advantages and limitations of incineration,
139
the importance of adequate waste disposal in Brazil, along with the need to evaluate
140
economic and energy generation potential for USW incineration plants, all fit into the
141
objectives in this study. The objective here is to evaluate the viability of the total energy
142
potential and the viable energy potential of USW incineration in Brazil and, based on
143
the results obtained, discuss the opportunities and limitations of incineration implemen-
144
tation in the country. This paper brings forth a new proposal in that the estimation of
145
energy potential and economic viability of incineration can be seen as a function of
146
population, with the objective of calculating the viable energy potential in the country.
147
The methodology can be replicated in other regions or for other wastes, promoting im-
148
portant discussions about energy planning and waste management.
149
2. Methodology
150
The methodology applied is based on the energy and economic calculation of the
151
implantation of incineration plants for different population sizes, obtain a complete
152
analysis of the parameters in function of the population, and estimate a minimum popu-
153
lation that makes such a venture feasible. Once this population is defined, it is possible
154
to determine the total potential of economically viable energy derived from the pro-
155
posed incineration plants throughout Brazil. This methodology was followed by studies
156
such as Barros et al. (2014) [34] (for disposal of USW in landfills), Luz et al. (2015)
157
[35] (for gasification of USW) and Bernal et al. (2017) [36] (in their studies on the rela-
8
158
tion of a ton of ground cane and the economic viability of a biogas plant from the sugar
159
cane vinasse). The following section details each step of this methodology.
160
2.1. Population definitions and calculation of waste generation
161 162 163
Calculations were performed for nine sets of population data (2,000; 5,000;
164
10,000; 20,000; 50,000; 100,000; 500,000; 1,000,000; and 3,000,000) established based
165
on the upper limits of the population sizes defined by the Brazilian Institute of Geogra-
166
phy and Statistics [37]. The daily waste generation for each population range was calcu-
167
lated using Equation 1. Due to the lack of more detailed data, and to the fact that present
168
work calculations do not refer to a specific locality but rather to population ranges, the
169
Brazilian average gravimetric composition (presented in Table 2) was used to calculate
170
the production of each type of residue in each analyzed population class (using Equation
171
2). Table 2: Average gravimetric composition of urban solid waste in Brazil. Source: Adopted from [32].
Wastes
Percentage (%)
Metals
2.9
Steel
2.3
Aluminum
0.6
Paper, cardboard and
13.1
tetrapak Total plastic
13.5
Plastic film
8.9
Rigid Plastic
4.6
Glass
2.4
Organic matter
51.4
Others
16.7
9
Table 2: Average gravimetric composition of urban solid waste in Brazil. Source: Adopted from [32].
Total
100
172 173
=
∙ (%) 1000 =
∙
(1)
(2)
174 175
Where: R = waste production (t/day); Pop = population and IG = per capita waste genera-
176
tion index (kg/person day), Fi = fraction of each type of residue removed from the grav-
177
imetric composition (Table A of supplementary materials – [38]) and Ri = daily produc-
178
tion of each type of residue. The IG index was obtained through data from the National
179
Sanitation Information System (SNIS) and can be seen in Table A of supplementary
180
materials [38]. Only solid waste with greater calorific value of the following substances
181
were considered in the calculations: organic matter, plastic, paper, cardboard and tetra-
182
pak.
183 184
2.2. Energy calculations
185
Based on heat-generating values for each type of residue presented in Table 3,
186
the total heat value (Equations 3 and 4) was calculated [12, 18]. The available power
187
and the energy produced by the incinerator were calculated using Equation 5 [9] and 6
188
[39].
189
=
∙
∙
(3)
190
10
(4)
= =
∙ η ∙ R ∙ k
!=
∙
"
(5)
∙ 8,760
(6)
191 192
Where: LCV = lower calorific value of each type of residue in kcal / kg (Table 3); k1 =
193
conversion constant from kcal/kg to kJ/kg = 4.184; LCVi calorific value contained in
194
each RSU fraction in kJ / kg; LCVTotal = total calorific value of the residue in kJ/kg; η =
195
electric recovery of all energy generation systems from incineration = 22% (obtained in
196
[12]); k2 = unit adjustment constant so that the resulting power is in kW = 0.01157; P =
197
electric power in kW; 8,760 = number of hours per year; CF = capacity factor adopted
198
as being equal to 80% [12] and E = electric energy produced in kWh/year. Table 3: Lower calorific value. Source: Adapted from [12]. USW
LCV on Wet basis kcal/kg
Moisture (%)
Organic matter
712
25
Plastic
8,193
3
Paper and
2,729
5
cardboard 199 200
2.3. Economic Calculations
201
For the economic considerations of this study, two viability evaluation parame-
202
ters were used for each population size: Net Present Value (NPV) and Levelized Cost of
203
Electricity (LCOE). In addition, investment costs corresponding to the acquisition and
204
installation of the equipment was also considered.
205
Equation 7 allows the calculation of NPV. When NPV values are positive, the
206
investment proposal is economically viable. Additionally, the greater the NPV, the more
207
attractive the proposal [40]. The LCOE (Equation 8) represents the minimum rate of 11
208
sale of energy that makes the investment economically viable. In other words, if the
209
energy sales tariff is higher than the LCOE, then the proposal is economically viable
210
[41, 42]. =
(! ∙ ') −
0! =
n
o&m
(1 + i)
∑ ∑
–
(6)
2
(1 + 3)2 !2 (1 + 3)2
(7)
211 212
Where: Cn = cost of the enterprise per year in USD; i = interest rate; I = initial
213
investment in USD; Co & m = cost of operation and maintenance in USD/year; t = en-
214
ergy sales tariff in USD/MWh; m = project life and n = year of analysis.
215
The value adopted for interest rate i corresponds to the current value of the min-
216
imum rate obtained at the Central Bank of Brazil, equal to 6.5% per year with a risk
217
factor of 2.5% [43]. The costs of installation I of the enterprise were obtained through
218
Equation 8 as a function of the electric power in kW according to [44]. = 15,797 ∙
6.8
(8)
219
The costs for operation and maintenance (Co & m) were adopted as 4% of the
220
initial investment (according to [44]). For the calculation of annual revenues, the energy
221
sales tariff was set at 51.01 USD/MWh: the A-4 generation auction ceiling for the Bra-
222
zilian National Electric Energy Agency (ANEEL) for gas-fired thermal power plants in
223
2018 [45].
224
2.4. Potential calculations and sensitivity analyses
225
In order to achieve economic viability (NPV> 0 and LCOE
226
to determine the minimum population (Popmin) that would contribute to the total amount
227
of waste sent to the incinerator. The population classes and population distribution by 12
228
size of Brazilian municipalities presented by [37] were then used to adjust a regression
229
curve to determine the percentage of resident population, up to a certain population val-
230
ue of Y. This curve is shown in Figure 2. Subtracting this curve from the value of
231
100%, it is possible to determine the municipalities with a population higher than a cer-
232
tain value (parameter here called %Pop) (According to Equation 9).
233
234 235
Figure 2: Distribution of the percentage of Brazilian population, by population bands.
236
%
= 100 − 9 = 100 − (13.606 ∙ ln<
= − 112.28)
(9)
237 238
Where: Y = Percentage of the Brazilian population that inhabits cities with
239
populations lesser than a given population; % Pop = Percentage of the Brazilian popula-
240
tion that inhabits cities with a population greater than a given Pop population.
241
The minimum to obtain viability (Popmin) can be used in Equation (9) to deter-
242
mine the percentage of the population residing in cities with populations greater than 13
243
(Popmin). With this result, and considering the total Brazilian population (209.3 million),
244
the total population residing in cities where urban solid waste incineration plants are
245
economically viable, was calculated by applying the energy equations to this value
246
(Equations 3 to 6), thus resulting in the total viable energy potential in the country.
247
Finally, a sensitivity analysis was conducted with the objective of observing the
248
impact of the increase of the energy tariff on Popmin and the viable potential of every
249
country, a result that furthers relevant discussions about the Brazilian energy scenario.
250
3. Results
251
3.1. Energy calculations
252
Through Equation 5, annual energy production values for each population range
253
were obtained and can be seen in Table 4. With a population of 1,000,000 inhabitants,
254
the installed capacity of waste incineration is 14.1 MW, equal to a small hydropower
255
plant (which in Brazil is projected between 5 and 30 MW [46]). According to Fernandes
256
(2016) [47], who studied energy recovery for landfills in several Brazilian cities, the
257
average power generated from biogas is 5 W/city inhabitant. Thus, a city with 1,000,000
258
inhabitants would have an installed capacity of 5 MW. It is thus observed that the power
259
of the incinerator is about 2.8 times higher than that generated by sanitary landfill bio-
260
gas for the same waste stream. The energy generated by this same population reaches
261
almost 100 GWh/year. Given that the average residential consumption in Brazil is 160
262
(kWh/month) [48] and considering an average of three residents per household [49], one
263
can conclude that the energy produced could power 51,607 residences or 154,820 inhab-
264
itants; that is, 15.4% of the population. These results demonstrate the substantial energy
265
potential of incineration. Table 4: Energy and power production Population
Waste
Power
Energy
14
(inhabitants)
generation (t/d)
(kW)
(MWh/y)
2,000
1.4
26.8
187.5
5,000
3.4
66.9
468.8
10,000
6.9
133.8
937.6
20,000
13.7
267.6
1,875.2
50,000
35.1
684.1
4,794.4
100,000
70.2
1,368.3
9,588.9
500,000
331.5
6,461.3
45,280.9
1,000,000
725.4
14,138.9
99,085.4
3,000,000
2,386.8
46,521.6
326,023.1
266 267
These data show that incineration can be an option for contributing to a greater
268
portion of the national energy matrix, which currently suffers from rising levels of
269
thermal generation from fossil fuels and recurring reductions in the volumes of hydroe-
270
lectric reservoirs due to the scarcity of rainfall. In addition, the growth of large-scale
271
incineration on the national energy grid would provide support for the insertion of in-
272
termittent renewable sources, which require sources that provide stability to the system.
273
3.2. Economic Analysis
274
The economic results are provided in Table 5. When analyzing Table 5, it can be
275
noticed that for the current energy sale price values, all population sizes present nega-
276
tive NPV results, thus making the investment inviable; this is due to the high investment
277
costs related to construction. This is mainly caused by the emission control and treat-
278
ment stations [12]. Table 5: Net Present Value (NPV) and LCOE Results Population
Investment
Operation
Revenues
(inhabitants)
(USD)
and mainte-
(USD/y)
NPV (USD)
nance costs
LCOE
Unit cost
(USD/
(USD/kW)
MWh)
(USD/y) 2,000
269,015.8
10,760.6
14,424.4
-278.651,3
235.4
10,037.9
15
5,000
570,280.6
22,811.2
36,060.9
-561.398,2
199.6
8,524.4
10,000
1,006,776.8
40,271.1
72,121.8
-945.876,1
176.2
7,524.5
20,000
1,777,369.8
71,094.8
144,243.5
-1.579.416,3
155.5
6,641.9
50,000
3,837,882.4
153,515.3
368,804.4
-3.103.947,0
131.3
5,610.1
100,000
6,775,420.4
271,016.8
737,608.8
-5.017.254,0
115.9
4,951.7
500,000
24,195,595.8
967,823.8
3,483,152.8
13.378.386,6
3,744.6 87.7
279 280
Table 5 shows that although the NPV became increasingly negative as the popu-
281
lation increases (due to the increase in initial investment), LCOE values decreased ac-
282
cording to the population size and demonstrated that the required rate for viability re-
283
duces as the scale of the enterprise increases. Using the LCOE and population data, one
284
can construct Figure 3, where it is observed that the behavior of LCOE as a function of
285
population best fits a logarithmic curve, presenting a high correlation coefficient (R² =
286
0.968). The trend curve can be used for the initial LCOE estimation for incineration
287
plants in Brazil, which helps in the elaboration of economic studies and the potential of
288
these plants in the country while collaborating with the development of this technology.
16
289 290
Figure 3: Variation of LCOE with population
291 292
The minimum LCOE value was 61.5 USD/MWh (for 3 million inhabitants),
293
still 10.5 more than the 51.0 USD/MWh tariff for the sale of thermoelectric power
294
plants in Brazil. Therefore, a higher specific tariff for USW incineration energy sales in
295
Brazilian bidding processes would need to be created, which would consider LCOE
296
variations according to the population and installed power so that incineration plants
297
could become economically viable. In this way, the curve in Figure 3 can be used as an
298
auxiliary tool to define such tariffs.
299
In analyzing the unit cost data, it can be seen that these rates are generally higher
300
than those of other renewable energy sources such as wind power (around 1,360
301
USD/kW) and small hydroelectric plants (1,670 USD/kW) [50]. Unit incineration costs
302
are only beginning to approach those of biogas (around 2,700 USD/kW) for populations
303
of around 3 million. This also reinforces the high costs of incineration.
17
304
As presented by Santos et al. (2019) [18] and previously discussed, USW incin-
305
eration generates more energy than other energy recovery options. By generating more
306
energy from waste, less fossil fuel energy will be required and a smaller amount of CO2
307
will be emitted into the atmosphere. In addition, incineration drastically reduces USW
308
volume, thereby reducing disposal in landfills and generating geographical preservation
309
as well as reducing the environmental impacts of these structures. The creation of inter-
310
municipal consortia, where the waste from nearby cities is sent to a single waste treat-
311
ment unit, can contribute not only to the increase of energy production in these plants,
312
but also to waste management throughout an entire region. Therefore, it is necessary to
313
create mechanisms that convert the environmental benefits of this technology into eco-
314
nomic ones, thereby increasing the revenues of these projects and facilitating their fi-
315
nancial viability.
316
Another way to increase the financial attractiveness of incineration (especially in
317
smaller cities) is the application of the distributed energy generation market. This mar-
318
ket has been developing recently throughout the country due to policies adopted by
319
ANEEL, both by Resolution No. 482/2012 [51] and by Resolution No. 687/2015 [52].
320
The Resolution stipulates that projects with a capacity of up to 3 MW may benefit from
321
this policy. In turn, this allows an entrepreneur to invest in one form of generation and
322
use the energy produced to reduce the demand of other units or companies that are reg-
323
istered under the same document.
324
Entrepreneur income will grow, due to the economy with the purchase of energy
325
from the distributor, whose tariff is higher than the sale in government biddings. Ac-
326
cording to the Brazilian Association of Energy Distributors (ABRADEE) [53], the value
327
of the energy tariff in this market is close to 165 USD/MWh. Comparing this value to
328
the LCOE values presented in Table 5, populations of up to 220,000 inhabitants could
18
329
apply USW incineration in the distributed generation market. Viability in this market
330
would be obtained for population values between 20,000 and 220,000 inhabitants.
331
It is worth mentioning that the calculations of the present study were carried out
332
without considering importation taxes levied on the equipment. Therefore, the creation
333
of a national industry that allows the localized production of this technology, reducing
334
the initial investment costs, is fundamental to the development of the incineration plants
335
within Brazilian borders. The creation of this industry can also collaborate with the gen-
336
eration of jobs and development of the national economy.
337 338
3.3. Sensitivity Analysis
339
The impacts of the increased energy sales tariff on the energy and economic po-
340
tential of the incineration were analyzed using NPV as a parameter. The NPV ratio
341
curves by population were calculated for different values of energy sales tariffs from 51
342
USD/MWh (current value) to 129 USD/MWh at a rate of 26 USD/MWh. Figure 4 illus-
343
trates how such a variation occurs.
344 345
Figure 4: Effect of the variation of the energy sales tariff on the NPV. 19
346
It is observed that higher values for energy sales tariff result in a more positively
347
inclined curve. This indicates greater attractiveness for investment. The tariffs stipulated
348
here exceed the values adopted by ANEEL in energy auctions, thus making these sce-
349
narios consider the government's actions which encourage incineration rates. From Fig-
350
ure 4, the minimum population (Popmin) values for incineration viability were obtained
351
for each of the tariffs analyzed. The relationship between Popmin and T is presented in
352
Table 6. For T = 51 USD/MWh, no population size attained viable results. With the
353
Popmin values, one can calculate the population that could be benefited only by economi-
354
cally viable incineration plants (through Equation 9) and the feasible energy potential in
355
the country (Table 6). Table 6: Minimum viable population per energy sale tariff Minimum
Population
Population
Economically viable
viable
receiving
Receiving
energy potential in
Population
Power
Power (% of total)
the country
(inhabitants)
(inhabitants)
77
1,410,141
40,927,385
19.6
4,430,308.67
103
294,713
85,335,583
40.9
9,239,716.57
129
85,312
120,502,793
57.8
13,048,325.34
Energy sale tariff (USD/MWh)
(MWh / y)
356 357
With tariff increases, the increase in the population who would receive power is
358
significant, showing an average increase of USD 1/MWh. This, in turn, would result in
359
an increase of the viable energy potential throughout the country by an average of 165
360
GWh/year, demonstrating the overall impact of the energy tariff on a national level.
361
In the best scenarios (T = 129 USD/MWh), incineration is feasible for more than
362
half of the Brazilian population (more than 120 million inhabitants). As the per capita
363
waste generation index in Brazil is close to 1.03 kg/person/day [6], the total generation
364
of waste in this scenario, which would not be sent to landfills. That would add up to
365
nearly 123.6 thousand tons/year. This is a considerable reduction in the areas required 20
366
for waste burial while also avoiding possible soil and groundwater contamination
367
caused by the disposal of waste in incorrect locations. In addition, the country would
368
have a new energy source that could replace the production of energy from fossil fuels.
369
Using the same values of average energy per residence and inhabitants per resi-
370
dence applied in section 3.1 (160 kWh/month and 3 inhabitants/residence – [48, 49]), it
371
is seen that economically, the viable energy potential in this scenario could supply a
372
population of 20 million inhabitants; that is, almost 10% of the country’s total popula-
373
tion.
374 375
4. Conclusions
376
This study sought to analyze energy generation through implantation of USW
377
incineration plants in Brazil, and analyze the economic feasibility through a function of
378
the waste generation population. Incineration is encouraged by the National Solid Waste
379
Policy of Brazil and stands out as a great alternative for final disposal of USW. This can
380
be applied to reduce the quantity and land-area occupied by landfills, which are the pre-
381
dominant disposal technique in the country and consuming a significant area and gener-
382
ating pollution threats.
383
The results showed how incineration is advantageous from an energy generation
384
perspective, and that it is able to supply more than 15% of the population that contrib-
385
utes waste to the plants. The power generated by an incinerator is about three times
386
greater than that which could be generated by landfill biogas for the same waste mass.
387
In economic terms, incineration does not yet yield good results. For the energy
388
sale tariff values currently used on the Brazilian energy market, financial viability was
389
not verified. This is due to the elevated installation costs, along with operational and
390
maintenance costs for the equipment required by the incineration plants, which is 21
391
caused by the need for a strict gas control and treatment system in these plants. Through
392
the sensitivity analysis, the energy sales tariff had a significant impact on the economic
393
viability of these plants and on the overall viable energy potential. This energy potential
394
grows on average by 165 GWh per year for each increase of 1 USD/MWh in the energy
395
sales tariff.
396
Given the impact which such economic factors exercise on energy potential for
397
incineration in Brazil, it is fundamental that municipal, state and federal government
398
work to establish a basis for large-scale implantation of this technology, either through
399
incentives for production of technology at the national level, an increased energy sales
400
tariffs values, or through mechanisms that convert the environmental benefits of this
401
technology into economic benefits.
402
The methodology developed in this paper includes calculations for energy and
403
economic potential which are elaborated according to population size and enable the
404
calculation of total viable energy potential throughout the country of Brazil, can be ap-
405
plied in other regions and scenarios, as well as for other types of waste. In doing so, the
406
extension of this methodology will thereby help studies and further discussion on ener-
407
gy use from waste in general.
408
Acknowledgements
409
We wish to thank the Coordination for the Improvement of Higher Education Personnel
410
(Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, CAPES; in Portu-
411
guese) for the support given by granting Doctor of Science scholarships to Ivan Felipe
412
Silva dos Santos and Andriani Tavares Tenório Gonçalves and Master of Science schol-
413
arships to Johnson Herlich Roslee Mensah. The authors would like to thank
414
the Brazilian National Council for Scientific and Technological Development (Conselho
415
Nacional de Desenvolvimento Científico e Tecnológico, CNPq; in Portuguese), for 22
416
granting a productivity in research scholarship to Prof. Regina Mambeli Barros (PQ2,
417
Process number: 301986/2015-0).
418
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[53] ABRADEE. Brazilian Association of Electric Distributors. Energy tariffs. 2017.
627
Available
628
energia/tarifas-de-energia>. Accessed on: 10/2018 (In portuguese).
in:
<
http://www.abradee.com.br/setor-de-distribuicao/tarifas-de-
31
Energy potential of MSW incineration was calculated in function of the population; Economic feasibility of MSW incineration in Brazil was evaluated and discussed; Economic feasible energy potential of MSW incineration in Brazil was estimated; A sensitivity analysis was conducted in function of energy sale rate.
Ms. Ref. No.: RENE-D-19-01938 Title: Incineration of Municipal Solid Waste in Brazil: An Analysis of the economically viable energy potential Renewable Energy
Dear Soteris Kalogirou, PhD Editor-in-Chief Renewable Energy
Based on the reviewers' comments, we made the following revisions. We have carefully revised the entire manuscript in response to the reviewers. Reviewer #1 1. The authors made an effort to study the energy and economic potential for the incineration of MSW in Brazil. I would suggest authors consider below modifications for easy readability and to improve the article further. The authors are grateful for the reviewers' complimentary comments and report that they endeavored to respond to all of their comments. 2. I suggest authors proofread for spelling and grammatical mistakes. To improve the writing of the article, the authors submitted it to the service of a native English proofreader. The authors understand that the new version of the manuscript is superior to the previous one. 3. Please insert a Graphical Abstract. The authors added a graphical abstract, as suggested by the reviewer. As the results were many, the authors focused on the main conclusions of the sensitivity analysis regarding the potentially served population and energy potential for constructing the figure. 4. What are the best approach to convert MSW into bioenergy, thermochemical (pyrolysis, combustion, gasification) or biochemical, and why? This issue is not a simple answer question, as it depends on the focus (environmental, energy, economic) and a variety of factors such as waste composition, scale, region analyzed (like costs, type and volume of waste and availability of labor vary from region to region), among others. However, to discuss this issue in our article, we insert two paragraphs presenting the results of several works that indicate the best technology according to the analyzed
approach (environmental, energy, etc.) (See lines 68 to 82). A table containing the advantages and disadvantages of each technology was also compiled by the authors based on seven different references and inserted in the introduction (See table 1). 5. Lines 75-87: Please cite the possibility the use of co-utilization of municipal solid waste with biomass as wood chips to minimize toxic gaseous emissions as in the following publication Da Silva Filho et al. (2019), Renewable Energy,
Volume
141,
October
2019,
Pages
402-410
~ https://doi.org/10.1016/j.renene.2019.04.032. Besides, the migration of chlorine can be controlled depending on the process conditions using a novel pilot-scale system combining pyrolysis and combustion processes. Thus, I think you need to highlight this potential by writing a sentence in the introduction of your manuscript along with the previous paper, which could be used to improve the manuscript. The authors appreciate the reviewer's suggestion and understand that the work indicated is of high relevance. For this reason, they inserted a portion of text between lines 86 and 94 to mention such potential in the context of the reduction of emissions generated by the MSW incineration process. 6. MSW characteristics influence the results of this study, but there is scarce information on MSW except for LHV in Table 1. To broaden discussions on MSW characteristics in the new version of the article, the authors added Table 2 to the methodology, which contains information on the gravimetric composition of waste in Brazil. Also, they added a paragraph between lines 130 and 137 of the introduction of the article discussing aspects such as the importance of waste composition on the incineration process. This paragraph is presented below: “An important parameter for incineration is waste material composition. This var-ies depending on the city, level of urbanization, population income, etc. [13, 31]. The average organic matter content in Brazilian waste (51.4% [32]) is a typical level of mid-dle-income countries [33]. Waste of major interest for incineration is USW fractions that have high calorific value, such as plastics, paper, cardboard and rubbers [12]. Organic matter has higher moisture content and can hinder the process. However, the use of or-ganic matter in incineration helps to reduce the volume of these residues and has been a scenario considered by several authors studying these techniques in Brazil [12, 28]"
7. Line 257: Instead of "Table 3 below" simply use Table 3. The authors have corrected this mistake.
Reviewer #2: 1. The manuscript is very well prepared, and technical quality and presentation
of
the
results
are
fairly
good.
The results/outcomes may be useful for decision-makers in Brasil. The authors thank the reviewers for their complimentary comments. 2. Reference style> Indicate references by numbers in square brackets in line with the text. Please check the guide for authors. This error was corrected by the authors, as suggested by the reviewer and the journal rules. 3. The writing style may be improved. To improve the writing style of the article, the authors submitted this to the service of a native English proofreader. The authors understand that the new version of the text is superior to the previous one. 4. Table 1 caption should be corrected. Lower calorific power?! The authors corrected this mistake. 5. The literature review may be extended. See e.g. 10.1016/j.rser.2015.05.067 10.1016/j.renene.2019.03.022 - 10.1177/0734242X17705721. The authors thank the article suggestions s by the reviewer and report that two of them used to extend the literature review (Scarlat et al., 2015 and Nordi et al., 2017). The authors have also inserted several other articles by other authors on this topic. In the new version of the article, the introductory chapter (in which the literature review is inserted) has 1778 words, a 57 % increase over the previous value (1,132 ). The increase in the number of references in the article was also significant, from 38 to 53 (an increase of 39 %). The authors understand that the new version of the article has a much higher quality literature review than the previous one. 6. The novelty is not clearly discussed. Please clearly state your news results. The novelty of this article lies in the estimation of the country's energy potential and economic viability as a function of the population in order to define the viable energy potential in the country using a methodology that can be replicated in other regions or for other waste, promoting important discussions about the
energy planning and waste management in Brazil. This remark was added in the last paragraph of the introduction of the article. The manuscript has now been resubmitted to your journal. We look forward to hearing from you and would like to thank you for all your input so that we may successfully publish our manuscript. We remain at your disposal for any further corrections. Yours sincerely,
Ivan Felipe Silva dos Santos Corresponding Author