Economic Feasibility Study of the Production of Biogas, Coke and Biofuels from the Organic Fraction of Municipal Waste Using Pyrolysis

Abstract

The objective of this study is to analyze the economic viability of municipal household solid waste (organic matter + paper) for the production of gas, coke and biofuel through the pyrolysis and distillation process. The waste was collected in the city of Belém do Pará-Brazil and pretreated at the Federal University of Pará. The analyzed fraction (organic matter + paper) was subjected to the pretreatment of drying, crushing, and sieving and was subsequently subjected to proximate characterization and, finally, pyrolysis of the organic fraction (organic matter + paper) in a fixed bed reactor. Initially, it was necessary to review the literature, and with the yields obtained by pyrolysis of the fraction, economic feasibility analyses were carried out. The economic indicators for evaluating the most viable pyrolysis process were basic payback, discounted payback, net present value, internal rate of return, and profitability index, which are all financial metrics commonly used in investment analysis and decision making. These metrics provide valuable insights into the financial viability and attractiveness of investment projects. They are essential tools for assessing the feasibility and profitability of various ventures, helping decision-makers make informed choices in allocating resources. The analysis of the indicators showed the economic viability considering an analysis horizon of 10 years of materials based on organic material and paper. The breakeven point obtained was USD 0.96/dm³ and the minimum biofuel sales price found in this project was USD 1.30/dm³. The sensitivity research found that material costs (organic matter + paper), bio-oil yield, total project investment and electricity, respectively, are the variables that most affect the minimum biofuel sales price.

1. Introduction

The production of urban solid waste (MSW) has increased exponentially over the years. Taking into account this growth, public policies, laws, federal and international agreements such as the Kyoto Protocol, the Paris agreement and more recently the Sustainable Development Goals (SDGs) established by the United Nations (UN) have emerged to establish criteria and limits for a previously unrestrained generation. The increase in waste generation and inadequate management from production to final disposal have generated numerous problems for society and the global scenario, aggravated by inadequate material management, generating negative impacts at a social, environmental, economic and even public health level [1,2].

According to the current consumer goods production scenario, MSW production will increase worldwide and is estimated to reach 3.4 billion tons by 2050, mainly due to population growth, increasing average incomes and accelerating urbanization rates [3,4].

Solid waste management affects everyone, but those who are most compromised by the negative impacts of poor management of this service are, in most cases, the most vulnerable in society. The dominant development model traditionally follows a linear economic approach called extract, produce and suppress. Efforts to optimize linear management practices are generally limited to the Rs of sustainability (rethink, reject, reduce, reuse and recycle), without considering the great potential to maximize the value of solid waste [5].

Distinct from traditional approach, which still eliminates waste in an environmentally inappropriate way, we present the circular economy, which seeks to maximize the value of using materials through the creation of a closed-loop economy. In other words, it is a regenerative system that minimizes resource input and waste by slowing, closing and narrowing the cycle, which can be achieved through maintenance, repair, reuse, recovery and recycling of materials [6,7,8].

Distinct from the traditional approach, which still eliminates waste in an environmentally inappropriate way, we present the circular economy, which seeks to maximize the value of using materials through the creation of a closed-loop economy. In other words, it is a regenerative system that minimizes resource input and waste by slowing, closing and narrowing the cycle, and this can be achieved through maintenance, repair, reuse, recovery and recycling of materials [8].

This reflection coincides with a new concept of urban planning that has emerged in recent decades, which proposes a change in models of spatial, social and environmental organization, which are “sustainable cities”, also called “green cities” or “smart green cities”. Urban waste management is a fundamental factor in this new urban vision; however, unless these new paradigms are enshrined in legislation, they will not drive real changes in urban planning and little progress will be made towards the recommended sustainable management [9].

With these changes in mind, the National Solid Waste Policy (PNRS) was sanctioned in Brazil, created by law 12.305/10 to regulate the management of urban waste. This law is very broad, with modern concepts, including shared product life cycle and reverse logistics. It places responsibility on producers and government agencies for the production and proper disposal of waste. However, even after its introduction, the remaining challenges are significant. Many municipalities do not comply with the requirements, especially when it comes to eliminating open dumps [10].

Among the many factors that impede these adjustments, one is the high cost of environmentally appropriate management of this waste. Currently, municipalities have limited budgetary resources and municipal accounts are difficult to balance [11].

In Brazil, MSW management is the third expense item in the budget of medium-sized municipalities, and may correspond to the main expense in municipalities with more than 50 thousand inhabitants [12].

In addition to the strong demand for public resources necessary for solid waste management, the economic situation of Brazilian municipalities stands out. Low capacity to generate revenues to finance administrative structures and services, together with high budgetary rigor are considered the elements of a structural financial crisis [13].

However, solutions must be discussed and implemented to mitigate the factors that hinder the adequate management of urban solid waste. We know that implementing correct management is not an easy task, as it involves multiple social actors, whether they are individuals or legal entities, public or private, who are directly or indirectly responsible for the solutions [14]. Additionally, there is a need to understand that some definitions contained in the PNRS are fundamental for a better basis in decision making, as mentioned in verbis (article 3 of the PNRS):

“VII—environmentally appropriate final destination: waste destination that includes reuse, recycling, COMPOSTING, RECOVERY AND ENERGY USE or other destinations admitted by the competent bodies of Sisnama, SNVS and Suasa, including final disposal, observing specific operational standards in order to avoid damage or risks to public health and safety and to minimize adverse environmental impacts;

VIII—environmentally appropriate final disposal: orderly distribution of WASTE in landfills, observing specific operational standards in order to avoid damage or risks to public health and safety and minimize adverse environmental impacts;

XV—waste: solid waste that, after exhausting all possibilities of treatment and recovery using AVAILABLE AND ECONOMICALLY VIABLE TECHNOLOGICAL PROCESSES, does not present any other possibility than environmentally appropriate final disposal;

XVI—solid waste: discarded material, substance, object or good resulting from human activities in society, whose final disposal is carried out, is proposed to be carried out or is obliged to be carried out, in solid or semi-solid states, as well as gases contained in containers and liquids whose particularities make their release into the public sewage system or bodies of water unfeasible, or require solutions that are technically or economically unfeasible in the face of the best available technology;”

Based on the definitions of solid waste, rejects, final destination and final disposal, the PNRS clearly states that any new treatment system implemented must meet the basic process guidelines before final disposal of the waste. This basic sequence can be described as follows: All waste must be reused and/or treated and only waste from these processes can be deposited in landfills. It is important to respect the criteria defined by the PNRS to become a final destination and ensure greater reintegration of waste into the production system, always respecting the technical feasibility and economic and financial viability of the projects [15].

There are several technologies currently available for the treatment and conversion of urban solid waste, including biological, physical–chemical and thermal treatments. As a heat treatment method, pyrolysis can transform materials such as waste biomass, thermoplastic polymers, hard and soft plastics, cardboard, recycled and nonrecycled paper, organic materials and municipal solid waste. A large amount of research in the literature delves into this subject. Bioprocesses and other thermochemical processes, such as the manufacture of liquid fuels and charcoal, a solid phase with adsorbent properties, have advantages of pyrolysis. The process also produces non-condensable gases with combustion properties and occurs at moderate ambient temperatures and pressures [16,17,18].

In this scenario, the present work analyzed the economic viability of producing biofuels (bio-oil, bio-coal and gas) by pyrolysis and catalytic thermal cracking of the fraction (organic matter + paper) of municipal household solid waste (MSW) from the Municipality of Belém-Pará-Brazil.

Recently, some work has been carried out to evaluate the economic viability of producing biofuels from the most diverse types of waste through the pyrolysis process. A summary of the latest works cited in the literature is listed below.

In a previous study [19], a facility was established for the technical and environmental evaluation of implementing pyrolysis in the treatment of hospital waste (RSS) in the city of Lindo Horizonte. Productivity 3000 L RSS per cycle. The evaluation process showed several benefits in waste management, such as mass reduction of 46.75–58.77% and the use of low-cost supplementary fuel (biomass) in wastewater treatment plants. From an economic point of view, it seems possible to produce bio-oil from pyrolysis to be sold at prices similar to mineral oils. This possibility is greater if comparatively large installations are used and if it is possible to sell the bio-oil at a price lower than that of distilled fuel oil but higher than the price of residual fuel oil. In January 2017, the ideal price would be between USD 1.119 and USD 2.632 per liter.

Already in [20] the thermal treatment of solid hospital waste (RSH) using a pyrolysis catalyst resulted in an oil content of 67.5% by weight, a density of 0.82 kg/L and a viscosity of 2318 mm²/s. These characteristics allow it to be used as a fuel in thermal processes or to create electrical energy in internal combustion engines. The production result expressed in money was verified with an economic balance comparing the two income-generating alternatives. The final balance (result of revenue subtracted from operating costs) from the sale of oil was estimated at R$3968.58/t (corresponding to 2678.79 R$/t RSH). Revenue from the sale of electrical energy was calculated by taking as a reference the sales value of MWhe of electrical energy produced from a renewable source (combustion of sugarcane bagasse). In this case, the revenue from the sale of electricity was calculated at R$2896.94 R$/t (corresponding to 1955.43 R$/t of RSH). Consequently, oil sales are economically more attractive than electricity sales, as they provide higher revenues than electricity sales, of 1071.64 R$/t, that is, 723.36 R$/t of RSH.

In [21], it can be concluded that the slow pyrolysis process using urban solid waste (MSW) offers many advantages not only for the city of Mossoró but also for other forms of treatment and use in environmental and economic terms, which applies to most Brazilian municipalities. The aforementioned municipality served as a basis for making an approximate estimate of the financial gains with the possible installation of a pyrolysis plant capable of processing 30% of the MSW generated per day, receiving 3,941,586.0 R$ per year from the sale of the energy, biofuels and coal produced, saving approximately 5623,393.50 R$ over the plant’s 25-year useful life.

This study [22] estimates the energy efficiency product costs and environmental impacts of biomass pyrolysis oil using life cycle assessment (LCA). As a case study, a factory with an annual production of 10,000 t was selected that uses Cryptomeria (Japanese cedar) as a raw material. The results show that production occupies the majority of the biomass oil life cycle, regardless of input costs, energy consumption or environmental impact. Pyrolysis oil costs approximately USD 9.74/dm³ (including bio-char) and the selling price (assuming 17% corporate income tax and 7% internal rate of return) is 19.6% higher than that of an equivalent amount of energy from low sulfur fuel oil. The ratio of output energy to input energy is approximately 13.2 (including biochar) or 7.3 (not including biochar), which indicates the high energy efficiency of pyrolysis oil.

This study’s [23] goal is to perform a thorough economic analysis of the thermal catalysis process used on palm oil neutralization sludge and crude palm oil. Additionally provided are the biofuel yields produced by fractional distillation. By examining the important variables and indicators, the thermo-catalytic processes of CPO and PONS are shown to be economically viable for both crude palm oil (Elaeis guineensis, Jacq) and palm oil neutralization sludge. This study establishes USD 1.59/dm³ for crude palm oil and USD 1.34/dm³ for residual neutralization of palm oil as the minimum fuel selling price for biofuels. Taking into account the residual neutralization of palm oil, USD 1.24/dm³ is the optimal balance point that was reached.

Given the economic conditions observed towards the close of 2019 and the initial months of 2020, the technical and economic feasibility of producing bio-oil from the three suggested biomass sources is evident. The raw material that has been most interesting is sugarcane bagasse, as it is the most economical raw material. The multifunctional plant developed in this study had an installation cost of approximately USD 31.40 million and was shown to be capable of handling these and other biomasses with chemical and biological properties similar to those of the present study. Considering the raw materials used in this process individually or a mixture of them, the annual production cost remains between USD 18.53 million and USD 80.49 million. In Scenarios 1 (conservative) and 2 (optimistic), the possibility of circularity between raw materials is presented. The project is viable for 20 years of operation, followed by 3 years of construction. In both situations, these plants are more profitable than investing in fixed assets with a minimum attractiveness of 25%. The internal rate of return (IRR) of Scenario 1 was 68% per year, and the internal rate of return (IRR) of Scenario 2 was 98% per year. The payback time in Scenario 1 was 4.43 years, considering three years of construction, and in Scenario 2, this time would be reduced to 3.74 years, which is a very good result [24].

We chose coconut biomass due to the large amount of residual biomass in the state of Alagoas. A total of 33,906.0 tons of biomass were constructed with an energy potential of approximately 60,800.0 MJ. The energy obtained from the pyrolysis of coconut biomass is significant, considering that the fresh mesocarp biomass containing a higher calorific value (PCS) is 17.466 MJ kg⁻¹, which will produce biochar with PCS of 26,587 MJ kg⁻¹ pyrolysis at 400 °C and PCS 27.020 can be obtained by pyrolysis at 600 °C. Coming from the natural biomass of the endocarp with a PCS of 19,401 MJ kg⁻¹, a biochar with a PCS of 31,062 MJ kg⁻¹ is obtained by pyrolysis at 400 °C and a biochar with a PCS of 32,403 MJ kg⁻¹ is obtained by pyrolysis at 600 °C. The best performance obtained is 56.38% of bio-oil by pyrolysis of the endocarp at a temperature of 600 °C. Therefore, the best performance and highest PCS were obtained at a temperature of 600 °C. Energy gains can reach 4841 MJ kg⁻¹. The evaluation results with a profit of 6%, NPV of 268,710.0 R$ and positive IRR of 17.10% suggest the viability of the investment [25].

Going beyond the technical conclusions, compared to the viability of the urban solid waste treatment unit, the two models investigated, both the slow rotation drum pyrolysis unit and the pyrolytic gasification unit, are viable. The main thing would be for the municipalities to be compensated for the treatment of their waste (which already occurs today) at a value of R$196.48, which the current value makes viable and, in addition, profitable for the facilities to be installed. This leads us to believe that there is a very interesting scope for the private sector to enter this area strongly because it is possible to be profitable with very robust values. Another scenario would be to consider a public investment where the municipality would have to bear the initial value of the unit and a minimum value per ton for the projects to be viable; in the case of the 141 t/d unit, it would be 133.00 R$/t, while a 120 t/d factory R$/t/day would be 88.00 R$/t [26].

Activated carbon is very important in the adsorption process in wastewater treatment plants. In particular, malt bagasse, a residue from the brewing industry, can be used to obtain charcoal, which has been applied on an industrial scale to remove drugs from aqueous systems due to its removal potential. To determine the minimum selling price of coal per kilogram, I conducted a literature analysis focusing on net present value and the internal rate of return, with predetermined assumptions. An analysis of a charcoal production unit from a brewery (on-site) and a bagasse and charcoal supply company (off-site) resulted in an on-site selling price of USD 1.78/kg and USD 1.84/kg for external products, both of which confirmed the economic viability of the project. Furthermore, with an annual production of 108 tons of coal, the costs can be paid with a minimum selling price of USD 1.78, generating a return of 9% [27].

Even though previous projects developed to evaluate the economic viability of producing biofuels from waste through the pyrolysis process presented positive results, the innovation of this study is its demonstration of the economic viability for the production of bio-oil from the organic fraction (organic matter + paper) of municipal household solid waste based on economic indicators, basic payback, discounted payback, net present value (NPV), internal rate of return (IRR) and profitability index (IL), with the aim of analyzing the viability of the project. A sensitivity analysis was used to evaluate bio-oil sales prices (MFSP—“Minimum Fuel Sale Price”), to measure the economic impact of varying the parameters used in the project analysis, such as initial investment, costs, expenses and revenues.

2. Materials and Procedures

2.1. Materials

2.1.1. Composition of Urban Solid Waste

The results from the gravimetric analysis of Municipal Solid Waste (MSW) gathered in Belém-Pará, Brazil, during the period from 18 to 29 October 2021, are detailed in

Table 1. Gravimetric examination of Municipal Solid Waste (MSW) [28].

Date:	18/10/2021	Time	20/10/2021	Time	27/10/2021	Time	29/10/2021	Time
Mass of MSW	102.00	07:30	106.50	07:30	107.25	07:30	113.50	07:30
Class of MSW	Mass (kg)	(wt.%)	Mass (kg)	(wt.%)	Mass (kg)	(wt.%)	Mass (kg)	(wt.%)
Paper	1.00	0.98	2.70	2.54	4.70	4.40	3.70	3.27
Cardboard	2.05	2.01	2.60	2.45	3.60	3.37	2.90	2.56
Tetra Pak	1.10	1.08	1.10	1.04	2.05	1.92	0.30	0.26
Hard Plastic	4.75	4.66	10.25	9.65	2.40	2.25	7.95	6.76
Soft Plastic	9.65	9.47	4.30	4.05	5.90	5.53	11.15	9.85
Metal	4.80	4.71	1.75	1.65	5.50	5.16	1.60	1.41
Organic Matter	55.50	54.44	69.95	65.84	62.40	58.50	76.40	68.52
Glass	9.80	9.61	1.60	1.51	1.90	1.78	0.35	0.33
Inert	13.30	13.05	12.00	11.29	18.20	17.06	8.80	7.77
Total	101.95	100.00	106.25	100.00	106.65	100.0	113.15	100.00

below. This table also includes information such as route number, date, collection time, MSW mass, and the percentage breakdown of MSW fractions (textiles, aluminum foil + plastic layers + cardboard + plastic caps + bioplastics = tetra pack, paper, cardboard, tissue + masks + disposable diapers + sanitary pads = domestic sanitary waste), along with other relevant data [28].

2.1.2. Organic Fraction (Organic Matter + Paper)

The organic content, comprising a blend of carbohydrates, lipids, proteins, fibers, and paper, derived from Municipal Solid Waste (MSW) in the Municipality of Belém-Pará, Brazil, underwent pretreatment (including drying, crushing, and sieving). Subsequently, it was preserved in a freezer to prevent any physical–chemical and microbiological deterioration, following the procedures outlined in the literature [28] (refer to Figure 1).

The desiccated portion, comprising organic matter and paper, underwent a process of crushing and sieving and was then subjected to proximate characterization [28].

2.1.3. Characterization of the Fraction (Organic Matter + Paper)

The desiccated, pulverized, and sifted portion, consisting of organic matter and paper, underwent proximate characterization to determine lipids, proteins, moisture, ash, pH, and electrical conductivity. The analysis followed the prescribed methodologies outlined in AOCS 963.15, AOCS 991.20, AOCS 935.29, ASTM D 3174-04, ASTM D129318, and ASTM D 1125-14, as described in details elsewhere [28]. The obtained results are detailed in

Table 2. Centesimal analysis was conducted on the dried, crushed, and sieved fraction containing organic matter and paper to determine the content of lipids, proteins, moisture, ash, pH, and electrical conductivity [28].

Centesimal Characterization	(wt.%)
Lipids	10.41
Proteins	11.33
Moisture	28.74
Ash	6.73
Volatile matter	-
Fixed carbon	-
Physicochemical characterization
pH, 27.0 °C (-)	5.77
Conductivity, 27.2 °C (μS/m)	15.31

[28].

2.2. Pyrolysis of Materials

2.2.1. The Influence of Temperature on the Pyrolysis Process

Table 3. On a laboratory scale, the pyrolysis of the MSW fraction (comprising organic matter and paper) at temperatures of 400, 450, and 475 °C, and under atmospheric pressure (1.0 atmosphere), involves the examination of process parameters, mass balances, and the resulting yields of reaction products, including liquids, solids, H₂O, and gas [28].

Process Parameters	0.0% (wt.)
	400 °C	450 °C	475 °C
Mass of residual fat (g)	50.14	50.29	50.49
Cracking time (min)	70	100	70
Initial cracking temperature (°C)	397	348	318
Mechanical system stirring speed (rpm)	0	0	0
Mass of solid (Coke) (kg)	22.94	19.07	17.82
Mass of liquid (Bio-oil) (kg)	1.32	3.74	4.75
Mass of H2O (kg)	17.59	17.10	14.43
Mass of gas (kg)	8.29	10.09	13.49
Yield of Bio-oil (wt.%)	2.63	7.43	9.41
Yield of H2O (wt.%)	35.08	34.00	28.58
Yield of Coke (wt.%)	45.75	37.92	35.29
Yield of Gas (wt.%)	16.54	20.65	26.72

displays the parameters of the process, mass balances, and yields of reaction products (liquids, solids, H₂O, and gases) generated from the pyrolysis of the MSW fraction (organic matter + paper) at temperatures of 400, 450, and 475 °C, and atmospheric pressure on a laboratory scale. The increase in pyrolysis temperature enhances the production of bio-oil due to the greater energy available for breaking strong organic chemical bonds. The temperature also significantly influences the distribution of reaction products. The findings indicate that, at 400 °C, biochar exhibits the highest yield at 45.75% by weight, whereas oil and gas achieve their highest yields at 475 °C, with percentages of 9.41% by weight and 26.72% by weight, respectively [28].

2.2.2. The Impact of the Catalyst on Pyrolysis

Table 4. Exhibits the parameters of the process, mass distributions, and the outcomes of reaction product yields (liquids, solids, H₂O, and gas) derived from thermocatalytic cracking of the fraction (organic matter + paper) at 475 °C, 1.0 atm, with catalyst concentrations of 5.0%, 10.0%, and 15.0% (by weight) Ca(OH)₂, conducted on a laboratory scale [28].

Process Parameters	475 (°C)
	0.0 (wt.)	5.0 (wt.)	10.0 (wt.)	15.0 (wt.)
Mass of the organic fraction of municipal solid waste (g)	50.49	40.0	40.0	40.0
Cracking time (min)	70	75	70	70
Initial cracking temperature (°C)	318	220	206	268
Mass of solids (Coke) (kg)	17.82	14.11	13.56	12.16
Mass of liquid (Bio-oil) (kg)	4.75	2.21	2.27	3.16
Mass of H2O (kg)	14.43	14.15	13.72	13.73
Gas mass (kg)	13.49	9.53	10.45	10.95
Bio-oil yield (by weight)	9.41	5.52	5.67	7.90
H2O yield (by weight)	28.58	35.37	34.30	34.32
Coke yield (by weight)	35.29	35.27	33.90	30.40
Gas yield (in weight)	26.72	23.82	26.12	27.37

illustrates the catalytic cracking of the MSW fraction (organic matter + paper) at 475 °C and 1.0 atmosphere, with catalyst additions of 5.0%, 10.0%, and 15.0% (by weight) of Ca(OH)₂, conducted on a laboratory scale. The presence of CaO as a catalyst has a notable impact on the yields of bio-oil, gas, and biochar. An increase in CaO content enhances bio-oil and gas yields but diminishes the bio-char yield while the H₂O phase remains consistent. The findings indicate that within the CaO content range of 0.0% to 7.0% (by weight), the yields of the H₂O phase and biochar remain stable, gas production slightly increases, and the bio-oil yield decreases [28].

By pyrolysis of the pretreated solid mixture of organic matter + paper, coming from municipal solid waste (MSW) from the Municipality of Belém-Pará-Brazil, they were treated in detail by [28]. The increase in pyrolysis temperature results in higher bio-oil yields, as the greater energy availability facilitates the breakdown of robust organic chemical bonds (Table 4).

2.3. Management and Project Assessment Criteria

Project management is the application of knowledge, skills, tools, and technicians to project activities to meet project needs. Project management is carried out through the application and integration of the following project management processes: initiation, planning, execution, monitoring and control, and closure [29].

Therefore, for a better understanding of the project management process and the assessment of economic viability, a biofuel production flow through thermal processing of pretreated material (organic + paper) was created, as shown in Figure 2.

Making decisions on the conception, design and evaluation of an industrial project requires some economic criteria [30]. The most effective way is to simulate the investment according to some decision-making indicators or economic models, as described in detail by Amaral et al. [31], such as Basic Payback [31,32,33], Discounted Payback [30,31], Net Present Value (NPV) [30,31,32,33,34], Internal Rate of Return (IRR) [31], and Profitability Index (IL) [31,33,34]. In this way, the cash flows generated with the investment made are compared. In addition, the calculation methodology, taking into account the main decision-making indicators, must be proposed and/or constructed for each particular case, as described by Amaral et al. [31].

2.4. Calculation Methodology

All data used to calculate feasibility for decision making on project viability are listed in

Table 5. Data used to calculate economic viability indicators.

Process Parameters	Value	Unit	Reference
M = is the mass of organic material + paper	2.610	kg/day	author
Nsh = number of shifts per day	3	-	author
d = density of organic material + paper	1.213	kg/dm3	[35]
Ybio-oil = yield of the bio-oil pyrolysis process	9.41	%	[28]
Ycoke = material coke yield in the pyrolysis process	35.29	%	[28]
Pcoke = price of coke	0.224	$/kg	[31]
dcoke = absolute density of coke	1 × 10−3	kg/dm3	[31]
Ygas = yield of methane gas from the material’s pyrolysis process	2672	%	[28]
PLPG = price of liquefied petroleum gas	0.275	$/dm3	[36]
dgas = density of methane gas	0.72 × 10−3	kg/dm3	[31]
Yd,bio-oil = yield of the material distillate process	60	%	author
PRM = raw material price of the material	0.1953	$/kg	[37]
Psieve = power of the sieve equipment	0.7457	kW	[38]
tsieve = sieving time per day	2	h	author
Nsieve = number of sieving batches per day	2	-	author
PKWh = price of KWh	0.2186	$/kWh	[39]
Pdry = drying equipment power	3	kW	[40]
tdry = drying time per day	24	h	author
Ndry = number of drying batches per day	5	-	author
Pcrus = power of crusher equipment	11	kW	[41]
tcrus = crusher time per day	1	h	author
Ncrus = number of crusher batches per day	1	-	author
mLPG = percentage of liquefied petroleum gas in relation to the feed rate	10	%	[42]
Cm = labor cost in thirty days	2343.7	$/month	author
PKWd = distillation column power	5	kW	[31]
td = distillation operating time during one day	24	h	author
Ndest. = number of distillation batches per day	2	-	author
%T = tax percentage	10	%	[31]
SPbio = selling price of biofuels produced with organic material + paper	1.30	$/dm3	author

.

The data mentioned in Table 5 are parameters used to calculate all possible expenses and revenues necessary for the production of bio-oil, gas and bio-char from organic waste + paper.

Expenses and income such as feed, organic liquid product (PLO), solid product (coke), gaseous product (biogas), distillate biofuel, raw material cost, liquefied petroleum gas (LPG), cost of manpower, distillation, taxes and profit margin were treated in detail by Amaral et al. [31], with the following new computation being included in this work:

2.4.1. Sieving

$$C_{sieve}=\frac{{(P}_{sieve}\times t_{sieve}\times N_{sieve}\times P_{kwh})}{(D_{bio}+m_{coke}+m_{gas})}$$

(1)

C_sieve = sieving cost [$/dm³]; P_sieve = power of the sieve equipment [kW]; t_sieve = sieving time per day [h]; N_sieve = number of sieving batches per day [-]; and P_kwh = price of kWh [$/kWh].

2.4.2. Drying

$$C_{dry}=\frac{{(P}_{dry}\times t_{dry}\times N_{dry}\times P_{kwh})}{(D_{bio}+m_{coke}+m_{gas})}$$

(2)

C_dry = drying cost [$/dm³]; P_dry = drying equipment power [kW]; t_dry = drying time per day [h]; N_dry = number of drying batches per day [-]; and P_kwh = price of kWh [$/kWh].

2.4.3. Crusher

$$C_{crus}=\frac{(P_{crus}\times t_{crus}\times N_{crus}\times P_{kwh})}{(D_{bio}+m_{coke}+m_{gas})}$$

(3)

C_crus = crusher cost [$/dm³]; P_crus = power of the grinding equipment in [kW]; t_crus = grinding time per day [h]; N_crus = number of grinding batches per day [-]; and P_kwh = price of kWh in [$/kWh].

3. Results

Table 6. Financial metrics for conducting discounted cash flow analysis.

Lifespan	10	years
Plant Size/Feeding Rate	2610	kg/day
Discount rate	10	% per year
Financing	100	% own capital
Depreciation	-	% per year
Investment recovery period	10	years
Taxes	10	%
Start-up	-	months
Raw material cost	0.1953	$/kg
Plant availability	87.5	%
Plant operating time	7665	h
Reference year	2023
Electricity price	0.2186	$/kWh
Total equipment cost (CTE)	112,793.25	$
Direct costs (include installation of equipment, instrumentation and control, piping, electricity and buildings)	68,803.88	$ (61% CTE)
Total equipment installation cost (CTIE)	181,597.13	$ (61% CTE + CTE)
Storage	2723.96	$ (1.5% CTIE)
Space construction-warehouse	8171.87	$ (4.5% CTIE)
Total installation cost (CTI)	192,492.96	$ (CTIE + warehouse + space development)
Field Indirect Costs (CI)
- Field expenses	38,498.59	$ (20% CTI)
- Offices and building fees	48,123.24	$ (25% CTI)
- Contingency	5774.79	$ (3% CTI)
- Prominent costs	19,249.30	$ (10% CTI)
Total Capital Investments (ITC)	304,138.88	$ (CTI + CI)
Other costs (start-up, licenses, etc.)	30,413.89	$ (10% ITC)
Total project investment (ITP)	334,552.77	$ (ITC+ other costs)

outlines the financial metrics utilized in the discounted cash flow analysis. The comprehensive investment for the project amounted to USD 334,552.77. This figure represents the initial cash flow investment, derived from price survey data for each utilized equipment and other associated expenses.

Table 7. Income and expenses from the use of organic material and paper are computed using the equation described elsewhere [31].

Revenues
Feed_87.50% (Availability)_Cracking (1)	2151.69	dm3/day_d = 1.213 kg/m3
PLO product/bio-oil_9.41% (2)	202.47	dm3/day_Fre. distillation
Solid product (coke)_35.29% (3)	170.55	$/day
Gaseous Product (biogas)_26.72% (4)	11.23	$/day
Biofuel Product Distillation_60% (5)	121.5	$/day
Sale price (6)	1.30	$/dm3
Total expenses (7) = (8) + (9) + (10) + (11) + (12) + (13) + (14) + (15)	1.24	$/dm3
Raw Material (Neutralization Waste)_1 $/kg (8)	0.543	$/dm3
Sieving (0.7457 kW)_(2T/h) (9)	0.0003	$/dm3
Drying (3 kW)_(0.582 T/h) (10)	0.1118	$/dm3
Crusher (11 kW)_0.425 t/h (11)	0.0026	$/dm3
Liquefied Petroleum Gas (LPG)_10% (12)	0.063	$/dm3
Manpower (8MIL) (13)	0.333	$/dm3
Distillation (Heating)_5 kW (14)	0.056	$/dm3
Taxes_10% (15)	0.130	$/dm3
Profit Margin (16) = (6)–(7)	0.06	$/dm3
Total Profit	189.1	$/day
Month	5672	$/month
Year	68,063	$/year

displays the combined revenue, overall expenses, and yearly profit, amounting to USD 68,063.00. The determined minimum fuel sales price (MFSP) for biofuels in this study was USD 1.30/dm³. The previous literature mentioned in this research covers a range of values spanning from USD 1.11/dm³ to USD 9.74/dm³.

Table 8. Yearly cash flow related to organic material and paper for basic payback analysis.

Year	0	1	2	3	4	5
Cash flow	−334,552.77	68,062.78	68,062.78	68,062.78	68,062.78	68,062.78
Accumulated value	−33,452.77	−266,489.98	−198,427.20	−130,364.42	−62,301.64	5761.14
Year	6	7	8	9	10
Cash flow	68,062.78	68,062.78	68,062.78	68,062.78	68,062.78
Accumulated value	73,823.92	141,886.70	209,949.49	278,012.27	346,075.05

illustrates the cash flow for investment analysis, applying the basic payback criterion. The outcome indicates that the complete recovery of the investment, amounting to USD 5761.14, is achieved by the fifth year. Consequently, within the 10-year analysis horizon, the project is deemed economically viable.

Table 9. Yearly cash flow generated from the pyrolysis of organic material + paper, involving the production of bio-oil, coke, and bio-gas, along with the application of discounted payback analysis and net present value assessment.

Year	0	1	2	3	4	5
Cash flow	−334,552.7	68,062.78	68,062.78	68,062.78	68,062.78	68,062.78
Present value	−334,552.77	61,875.26	56,250.23	51,136.57	46,487.80	42,261.63
Accumulated value	−334,552.77	−272,677.51	−216,427.28	−165,290.70	−118,802.91	−76,541.27
Year	6	7	8	9	10
Cash flow	68,062.78	68,062.78	68,062.78	68,062.78	68,062.78
Present value	38,419.67	34,926.97	31,751.79	28,865.26	26,241.15
Accumulated value	−38,121.61	−3194.64	28,557.15	57,422.41	83,663.56

displays the cash flow pertaining to the investment analysis, incorporating the discounted payback criterion, net present value (NPV), internal rate of return (IRR), and the profitability index (IL). Utilizing the discounted payback criterion, it is determined that by the eighth year, the investment is fully recouped, considering a 10% per annum cash flow discount rate. This renders the project economically viable, as the analysis horizon for project evaluation extends over 10 years. In the context of the NPV criterion, it is ascertained that by the tenth year, there is a cumulative capital increase of USD 83,663.56 in profit, with a 10% per annum cash flow discount rate. This underscores the economic viability of the project, as the NPV remains positive by the eighth year within the 10-year analysis horizon. The internal rate of return (IRR) criterion indicates that for the 10-year analysis horizon, the obtained value is 15.55%, simulating the cash flow discount rate in

Table 10. Yearly cash flow resulting from the pyrolysis of organic material + paper, encompassing the production of bio-petroleum, coke, and biogas, along with an analysis of the internal rate of return.

Year	0	1	2	3	4	5
Cash flow	−334,552.77	68,062.78	68,062.78	68,062.78	68,062.78	68,062.78
Present value	−334,552,77	58,903.42	50,976.65	44,116.61	38,179.73	33,041.80
Accumulated value	−334,552.77	−275,649.35	−224,672.70	−180,556.09	−142,376.36	−109,334.56
Year	6	7	8	9	10
Cash flow	68,062.78	68,062.78	68,062.78	68,062.78	68,062.78
Present value	28,595.29	24,747.16	21,416.88	18,534.76	16,040.49
Accumulated value	−80,739.27	−55,992.11	−34,575.23	−16,040.48	0.02

up to the moment when the NPV tends to zero in the last year of analysis, surpassing the project’s minimum attractiveness rate of 10% per annum. This signifies the economic viability of the project. Lastly, the profitability index (IL) yields a value of 1.25, calculated by adding the initial investment (USD −334,552.7) to the NPV (USD 83,663.56) and dividing by the initial investment. This signifies that for every dollar invested in the project, a return of USD 1.25 is anticipated. According to the criteria of this index, the project is deemed economically viable.

Figure 3 represents the sensitivity analysis conducted for a fraction volume of 2151.69 dm³/day. In order to attain the fuel minimum fuel selling price (MFSP) of USD 1.30/dm³, an assumed internal rate of return (IRR) of 10% is applied. It is concluded that the cost of material (organic matter + paper), bio-oil yield, total project investment and electricity, respectively, are the most significant variables that affect the MFSP.

Figure 4 demonstrates that the increase in the yield of bio-oil in the pyrolysis results in a reduction of the MFSP. It is evident that percentages of 5% of bio-oil yield increase the MFSP to USD 1.45/dm³, while the improvement of the percentage of bio-oil yield to 15% reduces the MFSP to values below USD 1.19/dm³.

Figure 5 illustrates the Minimum Fuel Selling Price (MFSP) in relation to material cost through sensitivity analysis for a daily production volume of 2151.69 dm³/day of the fraction. Simultaneously, Figure 6 portrays the MFSP as a function of electricity through sensitivity analysis for the same daily production volume. Both graphs demonstrate that increasing material cost and increasing energy value result in an increase in MFSP. Figure 5 demonstrates that when the material cost reaches USD 0.14/kg, the MFSP reaches USD 1.12/dm³ and when the material has a higher cost, close to USD 0.25/kg, the MFSP also increases, now to USD 1.48/dm³. Figure 6 demonstrates that when the value of electricity is reduced to around USD 0.10/kWh, the MFSP is reduced to USD 1.20/dm³ (a value extremely close to that applied in Brazil to biofuels), when electricity reaches a value of USD 0.31/kWh, the MFSP increases the exponentiation to USD 1.40/dm³.

Figure 7 illustrates the relationship between minimum fuel selling price (MFSP) and project investment through sensitivity analysis, considering a specific production volume of 2151.69 dm³/day of the fraction. The chart illustrates that augmenting the overall project investment leads to a rise in the minimum fuel selling price (MFSP). Figure 7 indicates that when the total project investment is diminished to approximately [insert value], the MFSP experiences a corresponding reduction USD 304,892.0, the MFSP is reduced to USD 1.20/dm³ and for a project investment of around USD 364,213.00, the MFSP is increased to USD 1.42/dm³.

Operating cost, payback period, and break-even analysis are used to investigate the relationships between planned project cost and rate of return. The break-even point is the point at which total cost and total revenue are equal, which means there is a balance between revenue and expenses [43]. From this condition, we obtained the project’s breakeven point value of USD 0.96/dm³.

4. Conclusions

After using the project evaluation criteria (basic and discounted payback, NPV, IRR and IL) and understanding the process of using pyrolysis, we can guarantee the economic viability of using urban solid waste (organic material and paper) for the production of biogas, coke and biofuels. This result corroborates a secondary cause of this work, which is to provide an adequate, profitable and environmentally correct destination for urban solid waste, avoiding the traditional MSW treatment process of Brazilian municipalities, which collect non-selectively and allocate a large part to open dumps, without any prior treatment, further increasing local basic sanitation problems.

For the project developed, the initial investment was USD 334,552.77 with an annual profit of USD 68,063.00 for a minimum fuel sales price (MFSP) of USD 1.30/dm³, compatible with both the value established in the Brazilian market and in the literature cited in this work (USD 1.11 to 9.74/dm³).

Considering the project evaluation criteria, the amount initially invested was fully recovered in 8 years according to the discounted payback criteria, corroborating the viability of the project.

Finally, to reach the MFSP of USD 1.30/dm³ of fuel, a sensitivity analysis was carried out for a production of 2151.69 dm³/day of the studied fraction, being the cost of the material, bio-oil yield, total investment and electricity as the parameters that most affect the MFSP.