Waste to energy: An experimental study of utilizing the agricultural residue, MSW, and e-waste available in Bangladesh for pyrolysis conversion.

The paper aims to study different aspects of liquid fuel production through pyrolysis from agricultural residues, MSW, and e-waste available in Bangladesh. The abundant production of various crops generates massive amounts of residue such as rice straw, wheat straw, rice husk, jute stick, and sugarcane bagasse in Bangladesh have great potential for liquid fuel production for pyrolysis conversion. Bangladesh produces almost 25,000 tons of solid waste per day from urban areas, and Dhaka city alone contributes to one-quarter of all urban waste in the country. The biomass and waste-derived pyrolysis fuel can be successfully used in turbines, boilers, engines and upgraded to high-quality hydrocarbon transportation fuels through distillation. The concise data obtained from the study is anticipated to provide valuable information regarding the effective utilization of municipal solid waste and agricultural residues by using pyrolysis process so that further detailed work on these resources can pave a pathway towards scientific research and significant energy contribution in Bangladesh. The feasibility study has been conducted through physical properties, proximate analysis, elemental analysis, and thermogravimetric analysis of the selected agricultural residues, municipal solid wastes, and plastic e-wastes for pyrolysis conversion in Bangladesh. It has been found that polythene has a better thermochemical potential than rice straw (13.71 MJ/kg) owing to its high calorific value (46.41 MJ/kg). The foremost volatile matter obtained from plastic waste is 98.1 wt.%, and the minimum from rice husk is 57.19 wt.%. The maximum carbon amount is possessed by plastic waste (84.03 wt.%). The ultimate analysis showed that the MSW sample contains more sulfur content than agricultural residue and e-waste, whereas the case is the opposite in terms of oxygen. Rice husk and tire waste have the highest ash content, i.e., 19.70 and 4.38 (wt.%), respectively, indicating a significant amount of unwanted material. TGA examination of feedstock revealed that the majority of mass loss occurred between 250-450 °C for agricultural residue attributed to the release of volatile materials during the formation of char and the evolution of pyrolysis gases. For MSW samples, the range varies between 350-500 °C, which is the appropriate temperature for optimizing liquid oil production in plastic pyrolysis.

Introduction

Waste refers to worthless, defective matter that is discarded after primary use and of no use. The daily waste generation rate in 2016 was 0.74kg/person/day, and total production was 2.01BT, with estimates of 7100 BT/day (total 2.59 BT) by 2030 and 9320BT/day (total 3.40 BT) by 2050 [1]. Waste is classified generically into three types: liquid waste, solid waste, and gaseous waste. The solid waste consists of municipal solid waste (MSW), construction, industrial, commercial, and agricultural solid waste [2]. Out of all different waste, municipal waste is a vital waste stream and one of the most studied. White et al. [3] added that MSWs are challenging to manage because of components diversity. Global MSW output is now 1.3 billion tons annually, but that figure is predicted to almost double by 2025 [4]. MSW contains a variety of waste types, including organic waste (wood, process residues paper, brush, yard leaves, food scraps, grass, and so on), paper waste (beverage cups, cardboard, paper scraps, newspapers, telephone directories, magazines, paper bags, wrapping paper, shredded paper and boxes, and so on), plastic waste (PW) (cups, packaging, containers, bottles, bags, and lids), glass waste (colored glass, broken glassware, bottles, light bulbs (rubber, textiles, e-waste, ash, appliances, leather element, other inert materials, etc.). MSW can also include a recyclable waste (metals, plastic, glass, paper, etc.), compostable organic matter (vegetable and fruit waste, fruit waste, etc.), toxic substances (discarded batteries, paints, pesticides, medicines, etc.), and hazardous solid waste (disposable medical elements such as syringes; sanitary napkins, etc.). Waste generation has a variety of negative environmental consequences, including the emission of greenhouse gases (GHG), such as CO2, N2O, and CH4. Methane emissions from improper waste management contribute 5% of total greenhouse gas emissions to the atmosphere [5, 6], along with nitrogen pollution and ocean plastic accumulation [7].

Bangladesh is an agriculture-based country and produces an enormous amount of agricultural residues each year. Crop residue is used mainly in rural areas as a cooking fuel (57.06%), animal feed (68.04%), cow dung ball (61.86%), reuse during subsequent cultivation, and organic manure on farms. Due to the expense of collecting the residues and the absence of appropriate technology, around (29–100%) of various crop residues are burned in the field or left to rot [8]. As a consequence, a significant amount of this energy is wasted. Hossen et al. [9] reported that if just 33% of biomass is used properly, the country's whole energy need can be fulfilled. M.N.Uddin et al. [10] explored that industrial and municipal solid wastes, human excreta and animal manure, forest, and agriculture residue can be potentially sustainable resources for power generation in Bangladesh [11].

Eleven feedstocks are chosen for this study, which fall into three categories. There are several reasons for selecting these particular feedstocks. Such as, out of all the agriculture residues, the chosen crop feedstocks are those residues generated from the main crops of Bangladesh, which indicates abundancy. The feedstocks chosen as MSW are polythene waste, plastic waste, tire waste, paper waste, and furniture waste. The components of MSW have a wide range and type; for example, food waste, glass, metals, etc., are not included in this study. Even though food waste accounts for the most significant percentage of MSW composition, it is not included because of its high moisture content compared to the feedstocks used in this study. Though e-waste is a different category consisting of several components, only electronic plastic waste has been considered in this study.

Crop residues from agriculture are roughly divided into two main categories: field residue and process residue. Process residue recovery percentage is higher, almost 100%, and can be effectively used for further energy production. But field residue recovery chances are lower; only 35% is utilized for fertilizer and other uses without impacting future crops [12, 13]. Numerous crop remnants, including rice, jute, corn, sugarcane, and wheat, have been verified as viable feedstocks for environmentally friendly and sustainable energy generation. The availability of these feedstocks makes them more compatible with renewable resources in Bangladesh. Table 1 shows the agriculture residue energy potential of Bangladesh in 2020.

Table 1

The energy potential of agricultural residue in 2020 in Bangladesh.

Crop Residues	Crops Production (kton1)	Residue Generation Ratio (kton/capita/day)	Residue Generation (kton/year)	Residue Recovery (kton/year)	Dry residue recovery (kton/year)	Energy potential(PJ/year)2
Rice husk	36604 [14]	0.28 [15]	9773.27	9773.26	8561.38	157.02
Rice straw	36604 [14]	1.69 [15]	62043.78	21715.32	18957.47	289.67
Wheat straw	1029 [14]	1.75 [16]	1800.75	630.26	582.99	9.50
Jute stick	8045 [14]	3 [16]	24135	8447.25	7644.76	147.93
SugarcaneBagasse	3683 [14]	0.29 [17]	1068.07	1068.07	544.70	9.99

In Bangladesh, around 300,000 tons of polythene are dumped each year. Bangladesh's urban areas generate 633,129 tons/year and almost 303 kg/day of plastic waste, comprising 8.45% of total waste. Approximately 2.7 million metric tons of electronic waste are generated in Bangladesh each year. Tire waste includes different tire types such as bus, truck, bicycle, rickshaw tire, motorcycle tire, auto-rickshaw tire. Every year, about 1.72 million motorcycle tires (5160 metric tons), 20.50 million bicycle/rickshaw tires, and 6,35,328 (28907.50 metric tons) bus and truck tires end up in the garbage, and they are stored until they can be disposed of properly or recycled. Food waste accounts for between 68 and 81% of total municipal solid waste, making it the category with the most significant contribution. Food waste can be generated from diverse sources, including the food manufacturing and processing industries, commercial institutions (such as supermarkets), hospitals, restaurants, and households. Every day, waste from food and vegetable markets adds up to a significant volume of trash. The food processing sector in Bangladesh also adds a tremendous amount of waste, such as shrimp processing, juice, paste, jelly, baking, potato chips, etc. About 52% said food waste occurs at wedding ceremonies, and 30% said it happens at restaurants. Table 2 illustrates the waste production composition in Bangladesh's urban areas.

Table 2

Composition of waste generated in Bangladesh's urban regions [18].

Types of waste (wt.%)	City/Town
	Dhaka	Chittagong	Khulna	Rajshahi	Barisal	Sylhet	Average
Food Waste	68.30	70.50	78.90	70.00	81.10	73.5	74
Paper	10.70	4.63	9.50	9.00	7.20	8.60	8
Plastic	4.30	8.70	3.10	9.00	3.50	3.50	5
Textile and wood	2.20	2.40	1.30	6.00	1.90	2.10	2
Leather and rubber	1.40	5.80	0.50	1.10	0.10	0.60	2
Metal	2.00	2.65	1.10	3.00	1.20	1.10	2
Glass	0.70	1.00	0.50	1.10	0.50	0.70	1
Others	10.40	7.40	5.10	0.80	4.50	9.90	6

Due to the enormous quantity of waste generated every day throughout Bangladesh, waste-to-energy conversion techniques attracted researchers in recent years. O.Alam et al. [19] published a review paper about Bangladesh's MSW management, treatment, and disposal processes. For waste to energy conversion, the authors emphasized using thermochemical conversion technologies (pyrolysis, gasification, and incineration). S.Mia et al. [20] proposed a waste management structure to utilize the urban waste of Bangladesh through the pyrolysis process. The authors analyzed that the proposed system could produce 3969 tons of biochar per day from municipal waste with a 210 million dollars annual return. U. Som et al. [21] published a research paper evaluating the energy production from the plastic content of the medical waste product in the Jessore district, Bangladesh, using the pyrolysis process. The authors found that about 3 tons of medical waste produced every day is 6.89% of the city's total waste. M.H. Masud et al. [22] investigated biomass energy's current status and prospects in Bangladesh. The authors also highlighted some different conversion techniques (direct and indirect combustion techniques) to produce energy. A.S.N. Huda et al. [23] conducted an experiment to illustrate Bangladesh's biomass energy conditions and prospects. The authors also described the thermochemical and biochemical conversion techniques to use biomass waste properly. M.S. Islam et al. [24] experimented with extracting pyrolytic oil from municipal solid waste at 400–550 °C, in which cellulosic biomass (organic food waste) was the primary raw material. The authors used scrap tires, waste paper, and plastic in an externally heated feed reactor pyrolysis system and analyzed and compared the pyrolytic fuel properties with petroleum-based oil. M.A. Aziz et al. [25] found that a maximum of around 42 wt.% of liquid yield can be achieved from scrap tire feed material while maintaining the feed size of 15 cm3 at 400 °C. M.S. Hossain et al. [26] derived the liquid pyrolytic oil using co-pyrolysis of polythene waste and rice straw. The authors obtained the highest 61% of liquid yield at 430 °C using a 1:1 combination. S.M. Rafew et al. [27] performed a simulation study for the Bangladeshi metropolis of Khulna to forecast solid waste production, collection, treatment, and landfill capacity until 2050. To assess the need for waste management in that particular city, the authors employed a system dynamics (SD) model. M.A. Habib et al. [28] analyzed solid waste scenarios and waste management in Rajshahi, Bangladesh, using qualitative and quantitative methods. According to the authors, the waste generation rate within this city is 358.19 tons per day, and anaerobic digestion may be a promising option in that area.

Only a few studies discussed the three broad categories of pyrolysis feedstock in one research. A complete analysis of different agricultural residues, MSW, and electronic waste considering a wide range of feedstock is essential. Most research in liquid fuel generation or reactor design and modification is based only on one kind of feedstock. Maintaining the experimental conditions for all selected samples is critical for evaluating the viability of various feed materials. There has yet to be comprehensive research that characterizes the different feedstocks while retaining the same experimental settings.

The aforementioned information gap served as the impetus for this research. To the best of the authors knowledge, this is the first systematic research of pyrolysis conversion in which a diverse range of samples of major categories of agricultural residue, MSW and e-waste feedstock were evaluated.

This present study aims to focus on the characterization of feed material. The research evaluates various tests on agricultural waste, MSW, and e-waste to perform a comprehensive analysis. This analysis includes heating value, ultimate analysis, proximate analysis, and ultimate analysis. Furthermore, thermogravimetry analysis (TGA) is also conducted. This research gave us the first-time ability to compare the various feedstock characterizations for pyrolysis of Bangladesh's abundant agricultural, municipal, and electronic waste. The information gathered will help researchers better grasp their potential for pyrolysis-based liquid fuel generation, which will be beneficial for energy and fuel applications.

Thermochemical conversion technology

The ultimate application must be defined in order to select the most appropriate thermochemical conversion technique. If heat is the primary concern, incineration may be a viable waste management option, and pyrolysis is beneficial when liquid fuel is preferred to a gaseous fuel in a particular application. On the contrary, syngas produced during gasification is used to generate energy.

Incineration involves the combustion of the organic substance found in waste materials with the presence of a sufficient amount of oxygen to fuel. Pyrolysis is the heat degradation of a substance in the absence of oxygen. Gasification can be seen between these two, where partial oxidations occur due to a small amount of oxygen supply. Table 3 shows three basic thermochemical conversion technologies.

Table 3

Comparison between three basic thermochemical conversion technologies.

Parameters	Incineration	Gasification	Pyrolysis
Atmosphere	No oxidant	Partial oxidizing	Oxidizing atmosphere
Temperature	(850–1200) ˚C	(550–1600) ˚C	(500–800) ˚C
Feedstock(Particular waste type)	Municipal solid waste, hazardous waste, medical waste, etc. [29].	Numerous waste streams, including municipal solid waste, industrial waste, and agricultural residue, are noteworthy examples [30].	Municipal solid waste, plastic waste, organic waste, forest residue, industrial wastes, agricultural residue are important examples [31]
Primary product	Heat	Gas	Gas, tar and oils, char
Product recovery	Boiler	Boiler, gas turbine, engine, synthesis	Gas (Boiler, gas turbine, engine, synthesis)
			Tar and oils (boiler, gas turbine, upgrading extraction)
Secondary product	Electricity	Electricity	Electricity
			Ammonia methanol, chemicals from synthesis
		Ammonia methanol, chemicals from synthesis	Gasoline
			Char used in soil amendment
High heating value (MJ/kg)	16–19	nil	5-20 [32]
Energy requirement [33]	Less than gasification and pyrolysis	Less than pyrolysis	More energy requirement but compensates by lower emission and energy recovery
Storage and transportation	Heat is used in the production site for heating purposes	Syngas needs immediate use after production	Bio-oil is easier to transport than syngas but difficult to store for long due to its corrosiveness [34].
Economic viability	Expensive	Comparatively expensive [35]	Cost effective [35]
Pollutants	SO2, NOx, HCl particulate matter, dioxins and furans etc.	H2S, HCl,NH3,HCN,tar, particulates etc.	H2S, HCl, NH3, HCN,tar, particulates, heavy metals etc. [36].
Emission	Higher emission of air pollutants [37]	Lower emissions of air pollutants than incineration	Lower emissions of air pollutants than incineration [37]
Emission control	Particulate collector	Bulk particle removal using a cyclone separator and filters	To remove heavy metals and dioxins in pyrolysis, the flue gas may be cleaned with an injection of reactive hydrated lime, perhaps in conjunction with active carbon, and then passed through a ceramic fiber filter before being released to the atmosphere.
		Fine particles, ammonia, and chlorides are removed by wet scrubbing.
	Acid gas scrubbers	Mercury and trace heavy metal removal using solid absorbents
		Adjusting the H2/CO ratio via a water-gas shift (WGS)
	In a variety of municipal waste incinerators, add-on NOx flue gas control systems include selective noncatalytic reduction (SNCR), mercury-based dioxin and furan removal, with powdered activated carbon injection [38].	Acid gas removal (AGR) for removing sulfur-bearing gases and converting COS (Carbonyl sulfide) to H2S, and catalytic hydrolysis for converting COS (Carbonyl sulfide) to H2S
		Engross grate combustion, Ebara fluidized bed process, plasma-assisted gasification etc. [39].
Social aspects	Reduce waste volumes	Reduce the waste volumes dumped in landfills	Reduce the waste volumes, mainly plastic waste, which will be dumped in landfills
	Hazardous emission affects the public health of the locality	Release less GHG gases	Release less GHG gases
	Create concern about the environmental emission	Water pollution used for cooling affects the locality	Danger related public health is less
	Employment opportunities	Employment opportunities	Employment opportunities
	Can supply particular energy demand of the surrounding cities from the output product	Can supply particular energy demand of the surrounding cities from the output product	Can supply energy demand of the surrounding cities from the output product
		Awareness of waste and residues used for energy production	The consciousness of waste and residues used for energy production

Material & methods

Feedstock characterization

Proper choice of feedstock plays an essential role in achieving a higher yield of bio-oil. Preparation of solid biomass feedstock is vital to obtain the high bio-oil output of fast pyrolysis. The practice is done in such a manner that expedites the bio-oil to achieve appropriate heat transfer rates. The combustion characteristics of fuel can be broadly understood by the provided heating value, ultimate and proximate analysis results of that particular fuel. The product yield of available feedstocks is represented in Table 4.

Table 4

Product yield from different feedstock.

Feedstock	Liquid (%)	Char (%)	Gas (%)	Temperature (˚C)	Reference
Rice husk	47	24.71	28.29	550	[33]
Rice Straw	26	47	17	500	[40]
Sugarcane bagasse	46	26	28	500	[41]
Jute stick	66.70	22.60	10.70	500	[42]
Wheat straw	49.90	32.90	15.60	400	[43]
Waste paper	48	28	24	600	[44]
Polythene	80	20	0	500	[26]
Plastic waste	79	20	1	500	[45]
Electronic waste	28.20	68.70	3.10	240	[46]
Tire	42	48	10	450	[47]
Furniture waste	58.10	21.30	20.60	450	[48]

Methods

The feasibility study of the selected materials has been conducted by determining higher heating values, bulk density, proximate analysis, ultimate analysis, and TGA analysis. The agricultural residues samples are collected locally from farming fields and corps processing mills, and solid waste are collected from dumpsites of Rajshahi City Corporation (RCC) of Bangladesh. All the samples are sun-dried and then oven-dried up to 110 °C for 8 h. The dried pieces are ground in particle form for laboratory tests/analyses. The heating value is determined from the Heat Engine Lab of RUET by using the Oxygen Bomb Calorimeter of model Parr 1341EB by following ASTM 2015-85 procedure [49]. Proximate analyses (volatile matter, ash content, moisture content, and fixed carbon) are carried out at the laboratory of the Bangladesh Council of Science and Industrial Research's (BCSIR) Institute of Fuel Research Development (IFRD), Dhaka, Bangladesh. The proximate analysis is undertaken in accordance with ASTM 3172 [50]. The elemental analysis is performed at the laboratory of the Analytical Research Division, BCSIR, Dhaka, Bangladesh [51]. Thermal gravimetric analysis (TGA) is conducted in the Science Laboratory of Rajshahi University using PerkinElmer TGA 4000 Thermogravimetric Analyzer by following the ASTM standard [52].

Heating value

A unit quantity of fuel's heating value or greater calorific value refers to the amount of heat produced by the complete combustion of a unit quantity of fuel. It is usually expressed in kJ/kg of fuel. It is an essential criterion for bio-fuel as it illustrates the total energy content of that fuel. The calorific value may be expressed as either net calorific value or gross calorific value, depending on the amount of water contained in the fuel. When water is present as a vapor, it is referred to as net calorific value; while water is available as a liquid, it is referred to as gross calorific value [53]. Its value relies on the relative proportion present in the fuel and the nature of the fuel. As the moisture content and hydrogen content increase, the calorific value decreases. The heating value affects the fuel efficiency; the efficiency of a heating system is related to its proportional value.

Proximate analysis

Basic specifications including volatile matter, ash content, moisture content, fixed carbon, and others provide a rough assessment of the fuel's behavior during combustion and give typical notions about traditional metrics like ash loading and predictions for emission characteristics constituents sulfur.

Moisture content

It can be characterized as the water weight in a material divided by the weight of the material in the dry state. The moisture level of agricultural wastes varies substantially depending on storage and drying processes. The moisture level of the feedstock is critical in influencing the drying cost and the energy content of the product. Higher moisture content is also an immediate concern for all thermal processes since it requires more energy to evaporate the water. It decreases the calorific value and adds unnecessary weight during transportation. Higher moisture content in the feedstock also causes a considerable amount of heat loss in water evaporation. It can be determined in two ways such as green basis and dry basis.

Volatile matter

Under specific conditions and in the absence of air, the volatile matter is driven off when a given sample is heated to 950 °C. It is usually a combination of long and short-chain hydrocarbon, aromatic hydrocarbon, and some sulfur. It is nothing but a toxic gas (CO, H2, H2O, CO2, CH4, N2, O2) [54]. Biomass having a greater content of volatile matter is more likely to provide a high concentration of bio-oil. The higher percentage of volatile matter increases the calorific value as well as produces long flames.

Ash content

It is the remaining inorganic residue when the sample is heated in the presence of the oxidizing agent, and the organic matter and water have been removed [55]. In this process, organic substances are placed in a muffle furnace, incinerated at 550 °C temperature, and inorganic matter as ash remains in the heater. It is measured by remaining inorganic matter weight [56]. A decrease in ash content increases the calorific value as ash is an incombustible matter. So, the ash content in the material should be as minimum as possible.

Fixed carbon

The fixed carbon determines the quantity of char produced during the pyrolysis process fixed carbon content may be readily determined by subtracting the percentages of ash content, volatile matter and moisture content from the initial mass. The combustible solid residue that stays around after the volatiles matter drives off [57]. Fixed carbon derived from the proximate analysis is different from the total carbon amount of the ultimate analysis. Fixed carbon does not include organic carbon, which escapes during combustion as a volatile matter, but total carbon from the ultimate analysis comprises this.

Ultimate analysis

The ultimate analysis identifies the sample's oxygen, sulfur, hydrogen, nitrogen, and carbon content. The percentage of hydrogen and carbon causes a higher calorific value and reduces the requirement of a large combustion chamber. Sulfur and nitrogen content affects the emission and corrosiveness of equipment. The combustion product of nitrogen and sulfur, i.e., NOx, SO2, and SO3, are harmful. The greater the calorific value, the smaller the proportion of oxygen. The moisture-holding capacity of fuel improves as the oxygen concentration increases, whereas the calorific value of fuel drops.

TGA analysis

Thermal gravimetric analysis, often known as thermogravimetric analysis (TGA), is a kind of thermal analysis in which the mass of a sample is measured over time as the temperature varies [58]. The measurement delivers precise information about physical incidents, such as absorption, phase transitions and desorption, and chemical fact, including solid-gas reactions (e.g., reduction or oxidation), chemisorption, and thermal decomposition. In addition, the TGA provided information regarding the temperature at which pyrolysis began, the temperature where the devolatilization rate was at its greatest, and the temperature at which the process was finished. Furthermore, the TGA curve revealed the fractional weight loss of volatiles in the sample as a function of temperature and time.

Result and discussion

The higher calorific value of all specimens is presented in Table 5. The proximate analysis provides moisture content, volatile matter, fixed carbon, and ash content of the feed material shown in Table 6. The ultimate analysis includes elemental composition (Carbon, Hydrogen, Nitrogen, Sulfur, Oxygen) of all samples presented in Table 7. Some feed material has a lower calorific value because of the presence of moisture content in the sample. The result obtained from the proximate analysis shows that moisture content is higher in agro residue and electronic waste. The maximum moisture content is 18.31 wt.% from wheat straw, and the minimum is 0.92 wt.% from electronic waste. For pyrolysis conversion, the moisture content should be kept near 10% if possible. Biomass possesses high moisture content because of the need for water for photosynthesis reactions. Lower moisture content leads to higher calorific value. The existence of large quantity of carbon (85.86%) and hydrogen (13.01%) was attributed to polythene's maximum higher calorific value (46.41 MJ/kg). In contrast, the smallest increased calorific value of waste paper was linked to the presence of a small amount of carbon (38.92 %) and hydrogen (6.77%).

Table 5

Higher Calorific Value of Selected feed materials.

Feed Material		Higher Calorific value in (MJ/kg)3
Rice Husk	Mean	18.34
	Standard Deviation	0.72
Rice Straw	Mean	15.28
	Standard Deviation	1.23
Sugarcane Bagasse	Mean	18.34
	Standard Deviation	1.24
Jute Stick	Mean	19.35
	Standard Deviation	1.20
Wheat Straw	Mean	16.30
	Standard Deviation	0.49
Waste paper	Mean	15.28
	Standard Deviation	1.32
Polythene	Mean	42.79
	Standard Deviation	3.07
Plastic Waste	Mean	31.58
	Standard Deviation	1.23
Electronic Waste	Mean	31.58
	Standard Deviation	1.93
Tire Waste	Mean	35.66
	Standard Deviation	0.48
Furniture Waste	Mean	37.7
	Standard Deviation	2.77

Table 6

Proximate Analysis of Selected Feed Material on wt.% basis.

Feed Material		Moisture Content (wt.%)	Volatile Matter (wt.%)	Ash Content(wt.%)	Fixed Carbon(wt.%)
Rice Husk	Mean	7.31	65	16	11
	Standard Deviation	0.87	4.78	2.83	2.46
Rice Straw	Mean	9.54	68.11	10.19	12.16
	Standard Deviation	1.05	6.64	2.20	3.29
Sugarcane Bagasse	Mean	6.41	81.77	0.97	10.85
	Standard Deviation	1.30	3.22	0.24	1.63
Jute Stick	Mean	11.23	85.33	0.30	2.63
	Standard Deviation	1.47	1.81	0.078	0.38
Wheat Straw	Mean	17.81	76.66	2.21	3.32
	Standard Deviation	0.52	0.70	0.70	0.67
Waste Paper	Mean	7.89	78.92	2.68	10.50
	Standard Deviation	0.40	2.40	0.54	0.35
Polythene	Mean	4.98	92.55	1.46	1.31
	Standard Deviation	0.24	2.28	0.42	0.44
Plastic Waste	Mean	2.09	97.3	0.23	0.37
	Standard Deviation	0.8940	0.7422	0.0632	0.0989
Electronic Waste	Mean	1.33	88	1.83	8.84
	Standard Deviation	0.57	2.46	0.12	0.11
Tire Waste	Mean	1.66	67.03	3.28	28
	Standard Deviation	0.27	2.15	0.96	2.12
Furniture Waste	Mean	6.63	74.99	2.7	15.68
	Standard Deviation	1.35	0.90	0.41	1.23

Table 7

Ultimate Analysis of Selected Feed Material on wt.% basis.

Feed Material		Carbon (wt.%)	Hydrogen (wt.%)	Nitrogen(wt.%)	Sulfur(wt.%)	Oxygen(wt.%)
Rice Husk	Mean	36.21	5.63	1.67	0.19	56.21
	Standard Deviation	2.40	0.39	0.40	0.38	2.34
Rice Straw	Mean	48.30	5.80	1.40	0.18	44.32
	Standard Deviation	0.73	0.43	0.59	0.02	3.45
Sugarcane Bagasse	Mean	49.23	5.62	0.19	0.02	44.94
	Standard Deviation	0.61	0.70	0.30	0.01	1.18
Jute Stick	Mean	48.21	5.83	0.46	0.04	45.46
	Standard Deviation	1.02	0.10	0.17	0.01	0.79
Wheat Straw	Mean	42.7	6.21	2.78	0.17	48.14
	Standard Deviation	0.66	0.38	0.20	0.06	1.18
Waste Paper	Mean	40.27	7.12	0.24	0.05	52.32
	Standard Deviation	0.89	0.45	0.07	0.02	0.80
Polythene	Mean	84.12	12.43	0.31	0.09	3.05
	Standard Deviation	1.30	0.51	0.08	0.01	0.48
Plastic Waste	Mean	83.91	8.43	0.06	1.32	6.40
	Standard Deviation	0.11	0.58	0.02	0.16	0.14
Electronic Waste	Mean	67.01	6.25	1.43	0.61	24.7
	Standard Deviation	0.26	0.52	0.22	0.12	1.87
Tire Waste	Mean	83.90	8.00	0.44	1.46	6.3
	Standard Deviation	3.09	0.20	0.07	0.16	0.84
Furniture Waste	Mean	41.28	6.23	0.17	1.65	50.67
	Standard Deviation	2.237	1.03	0.06	0.25	1.38

The amount of fixed carbon in biomass shows the amount of non-volatile organic matter present and its high calorific value. Tire waste has the highest increase in fixed carbon (30.3%), which corresponds to the acceptable heating value (36.01 MJ/kg). In pyrolysis, char is formed because of the presence of fixed carbon. Sometimes they get higher due to incomplete combustion and the presence of excessive moisture content.

Volatile matter refers to the volatile substances of the biomass residue, eliminating all organic components such hemicellulose, cellulose, and the majority of the lignin and moisture in the residue. According to the data given in Table 6, the plastic waste contains the most volatile matter (98.1%) and the least fixed carbon (0.26%). In comparison, tire waste has an insufficient volatile matter amount (63.51%) and the largest amount of fixed carbon (30.3%). By and large, high volatile matter enriched biomass generates a large quantity of syngas and bio-oil, whereas fixed carbon boosts the synthesis of biochar via thermochemical reactions [59]. Volatile matter is comparatively higher in MSW than crop residue because volatile matter, mainly non-water gases released at high temperatures, yields a higher calorific value. Non-volatiles comprise char with a higher calorific value and components that lead to ash formation, such as silica and a small amount of lignin. Calculating the ash content of biomass before processing for biofuel production is necessary since it can considerably impact the biomass conversion to biofuels, particularly in the biochemical process [60]. For agricultural residue, rice husk has the highest ash content (19.70%) as it has low volatile matter (69.1%) whereas, the jute stick shows higher volatility (87.03%) due to lower ash content (0.38%). For MSW, the highest ash content (4.38%) was found for tire waste due to the low amount of volatile matter. In contrast, the lowest ash content (0.14%) was obtained for plastic waste as a higher amount of volatile matter (96.1%) was present in it.

The ultimate analysis of the selected sample is illustrated in Table 7. In the ultimate analysis, it has also been shown that carbon, which is more critical for heat energy, is convenient in the selected feed material. The range of carbon present in all the samples is in the field of 32.29–85.85%. Hydrogen and nitrogen are found in the range of 4.53–13.01% and 0.145–3.07%, respectively. Sulfur lies in the range of 0.014–1.97%, and oxygen is found in the field of 2.38–58.92%. Sulfur and nitrogen should be as minimum as possible because of their harmful production of NOx, SO2, and SO3. Sulfur also has some corrosion effects on the equipment. As the oxygen level of the fuel grows, its moisture-holding capacity increases, lowering the fuel's calorific value. The higher oxygen content (53.18 %) in waste paper accounts for the higher volatile matter (81.21 %), but it also leads to a lower heating value (16.39 MJ/kg). The maximum carbon, hydrogen, nitrogen, sulfur, and oxygen have been obtained from plastic waste, polythene, wheat straw, furniture waste, and rice husk. The lowest carbon, hydrogen, nitrogen, sulfur, and oxygen have been obtained from rice husk, jute stick, waste paper, wheat straw, and plastic waste. The result may be sometimes unfavorable due to incomplete combustion, mixed foreign particles (dust, dirt, or additives), inhomogeneity of the sample.

Thermoanalytical techniques are widely used to investigate the kinetics and thermal properties of pyrolysis. TG or Thermogravimetric analysis is a process that shows the loss of a sample's mass against temperature in a TG curve under a regulated heating rate and gaseous atmosphere. This study's goal is to understand better heat degradation characteristics and kinetics of the feed material. Table 8 measures the decrease in subtracting mass caused by the release of volatile during thermal decomposition as a function of time. The pyrolysis kinetics gives essential information regarding pyrolysis conversion. From TGA analysis, the percentage of weight reduction can be determined which higher value indicates low moisture content, low residence time in the combustion chamber, high volatile matter for pyrolysis conversion.

Table 8

TGA Analysis of Selected Feed Material on wt.% basis.

Temp (°C)		Weight (%)(Rice Husk)	Weight (%) for(Rice Straw)	Weight (%) (SugarcaneBagasse)	Weight (%) (Jute Stick)	Weight (%) (Wheat Straw)	Weight (%) (Waste Paper)	Weight (%)(Plastic Waste)	Weight (%) (Electronic Waste)	Weight (%) (Furniture Waste)
30.41	Mean	99.86	99.46	99.94	99.93	99.82	99.94	99.71	99.99	99.90
	Standard Deviation	0.01	0.54	0.01	0.01	0.01	0.01	0.01	0.01	0.01
50	Mean	98.38	97.82	99.20	98.86	97.49	98.99	99.05	100.01	98.37
	Standard Deviation	0.01	0.01	0.01	0.01	0.01	0.01	0.01	0.01	0.01
75	Mean	95.36	93.91	97.29	95.89	94.15	96.46	98.73	99.88	94.24
	Standard Deviation	0.01	0.01	0.01	0.01	0.01	0.01	0.01	0.01	0.01
100	Mean	93.60	92.04	96.39	95.22	93.08	95.08	98.81	99.66	90.62
	Standard Deviation	0.01	0.01	0.01	0.01	0.01	0.01	0.01	0.01	0.01
125	Mean	93.07	91.52	96.27	94.97	92.91	94.68	98.78	99.44	89.39
	Standard Deviation	0.01	0.01	0.05	0.01	0.01	0.01	0.01	0.01	0.01
150	Mean	92.90	91.23	96.29	94.53	92.87	94.53	98.89	99.26	89.11
	Standard Deviation	0.01	0.01	0.01	0.01	0.01	0.01	0.01	0.01	0.01
175	Mean	92.78	91.08	96.20	94.20	92.84	94.49	98.84	99.12	88.94
	Standard Deviation	0.01	0.01	0.01	0.01	0.01	0.01	0.01	0.01	0.01
200	Mean	92.53	90.71	95.81	94.04	92.68	94.43	98.83	98.99	88.65
	Standard Deviation	0.01	0.01	0.01	0.01	0.01	0.01	0.01	0.01	0.01
225	Mean	91.89	89.55	94.46	93.45	91.94	94.25	98.76	98.83	87.94
	Standard Deviation	0.01	0.01	0.01	0.01	0.01	0.01	0.01	0.01	0.01
250	Mean	89.98	85.20	91.50	91.34	88.74	73.70	98.67	98.46	85.65
	Standard Deviation	0.02	0.01	0.01	0.01	0.01	0.01	0.01	0.01	0.01
275	Mean	84.23	73.31	82.80	84.16	78.59	91.88	98.44	97.73	79.33
	Standard Deviation	0.04	0.02	0.01	0.02	0.02	0.01	0.01	0.01	0.02
300	Mean	7.48	56.83	65.69	71.00	57.96	85.74	98.11	95.89	59.16
	Standard Deviation	0.05	0.02	0.03	0.02	0.01	0.02	0.01	0.01	0.06
325	Mean	57.73	44.60	42.32	43.36	40.58	62.12	97.45	93.75	37.35
	Standard Deviation	0.04	0.01	0.02	0.08	0.12	0.07	0.03	0.01	0.02
350	Mean	48.93	39.23	34.21	25.45	33.55	39.01	96.14	91.94	28.52
	Standard Deviation	0.01	0.01	0.01	0.01	0.01	0.01	0.01	0.01	0.01
375	Mean	44.25	34.72	29.29	20.29	28.00	35.70	92.12	88.37	19.33
	Standard Deviation	0.01	0.01	0.01	0.01	0.01	0.01	0.01	0.01	0.02
400	Mean	40.08	29.25	24.40	15.54	21.65	32.86	77.59	79.74	9.23
	Standard Deviation	0.01	0.01	0.01	0.01	0.01	0.01	0.03	0.02	0.01
425	Mean	35.75	22.45	18.06	10.51	14.02	29.41	39.03	66.01	1.09
	Standard Deviation	0.01	0.31	0.10	0.01	0.01	0.01	0.07	0.03	0.01
450	Mean	30.65	14.75	9.86	5.09	8.71	23.52	6.06	56.78	-4.01
	Standard Deviation	0.01	0.01	0.01	0.01	0.01	0.01	0.02	0.01	0.01
475	Mean	24.45	10.45	4.06	2.49	6.68	20.28	0.56	51.17	-5.13
	Standard Deviation	0.01	0.01	0.01	0.01	0.01	0.01	0.01	0.01	0.01
500	Mean	20.56	10.09	2.56	2.94	6.47	20.18	-3.52	44.24	-5.20
	Standard Deviation	0.01	0.01	0.09	0.01	0.01	0.01	0.01	0.01	0.01
525	Mean	19.55	9.96	2.60	2.27	6.41	20.12	-8.76	37.07	-5.21
	Standard Deviation	0.01	0.01	0.01	0.01	0.01	0.01	0.01	0.01	0.01
550	Mean	19.17	9.85	2.60	2.23	6.35	20.10	-9.43	34.20	-5.22
	Standard Deviation	0.01	0.01	0.01	0.01	0.01	0.01	0.01	0.01	0.01
575	Mean	18.99	9.74	2.59	2.19	6.30	20.09	-9.44	32.65	-5.24
	Standard Deviation	0.01	0.02	0.01	0.01	0.01	0.01	0.01	0.01	0.01
600	Mean	18.88	9.63	2.54	2.05	6.23	20.05	-9.45	31.35	-5.28
	Standard Deviation	0.01	0.01	0.01	0.01	0.01	0.01	0.01	0.01	0.01
625	Mean	18.80	9.48	2.53	2.01	6.09	19.82	-9.47	30.30	-5.36
	Standard Deviation	0.01	0.01	0.01	0.01	0.01	0.01	0.01	0.01	0.01
650	Mean	18.72	9.36	2.51	1.95	6.05	19.26	-9.44	29.71	-5.44
	Standard Deviation	0.01	0.01	0.01	0.01	0.01	0.01	0.01	0.01	0.01
675	Mean	18.64	9.33	2.50	1.87	6.02	18.02	-9.42	29.45	-5.49
	Standard Deviation	0.01	0.02	0.01	0.01	0.01	0.01	0.01	0.01	0.01
700	Mean	18.59	9.32	2.48	1.74	6.00	15.83	-9.40	29.34	-5.51
	Standard Deviation	0.01	0.01	0.01	0.01	0.01	0.01	0.01	0.01	0.01
725	Mean	18.54	9.28	2.45	1.56	5.94	13.08	-9.40	29.29	-5.53
	Standard Deviation	0.01	0.01	0.01	0.01	0.01	0.01	0.01	0.01	0.01
750	Mean	18.48	9.21	2.42	1.34	5.87	12.91	-9.43	29.25	-5.56
	Standard Deviation	0.01	0.01	0.01	0.01	0.01	0.01	0.01	0.01	0.01
775	Mean	18.43	9.08	2.36	1.02	5.73	12.87	-9.50	29.21	-5.61
	Standard Deviation	0.01	0.05	0.01	0.01	0.01	0.01	0.01	0.01	0.01
791	Mean	18.38	8.97	2.30	0.72	5.60	12.84	-9.58	29.18	-5.64
	Standard Deviation	0.01	0.04	0.01	0.01	0.01	0.01	0.01	0.01	0.01

Lignocellulosic biomass has a very complex structure consisting of moisture, cellulose, hemicellulose, and lignin. Therefore, TGA analysis is an indicator for determining the composition of biomass. Thermal degradation of lignin, cellulose, and hemicellulose is a set of sequential processes that takes place primarily in three stages.

For all the agricultural residue, waste paper, and furniture waste, the first zone starts at (29 °C–31 °C) and ends at (100 °C–110 °C) interval with a slight weight loss (3–10) %. The stage refers to the removal of water or moisture existing in the material and external water that is constrained by surface tension.

The second zone occurs from 110 °C and finishes at (350 °C–375 °C) with an average weight loss of (42–60%) for all residue and furniture waste. For paper waste, decomposition initiates from 100 °C to 450 °C with 77% weight loss. This second zone is referred to as the active pyrolysis zone due to high weight loss rates. The holocellulose (hemicellulose + cellulose) decomposition was observed in this stage.

The third zone which begins at around ((350 °C–375 °C) and keeps going to (700 °C–791 °C) with an average weight loss of (30–40) % (for residues and furniture waste) and for the paper waste starting point is 450 °C and continues to 791 °C for a minimal weight loss is termed as passive pyrolysis zone since reduction of weight is relatively low than the second zone. This zone is recognized as the lignin decomposition zone because lignin degradation happens slowly in most situations across a wide temperature range [61].

TGA analysis was also carried out for plastic and electronic waste, which shows two stages of decomposition to determine the optimum temperature for thermal degradation. The plastic waste initial degradation occurs at 350 °C and lasts to 420 °C with a 90% weight reduction. The rest degradation continues to 791 °C. The first stage of degradation of electronic waste begins at 350 °C and lasts to 520 °C with a 65% weight reduction. The rest degradation continues to 791 °C. For plastic and furniture waste data shows negative weight reduction, which may occur due to not maintaining an inert atmosphere or the machine is not calibrated correctly. If the experiment was carried out under an oxygen atmosphere, using a pan for two consecutive samples used previously under nitrogen atmosphere. This causes the sticking of ash in the pan. So, in the next using the exact pan cause (ash + existing sample) weight loss means more than the sample size gives a negative percentage. Maintaining an inert atmosphere is good to avoid oxidation because those nitrogen and argon gases do not interfere with the sample during thermal treatment. Under the oxygen atmosphere, black carbon starts burning at above 300 °C, CO and CO2 are produced, which causes more to lose weight. Table 8 shows the TGA analysis of nine feed materials.

Future challenges

Bangladesh has a vast number of resources that can be potential and effective feedstock for pyrolysis conversion. Still, pyrolysis is presently unacceptable due to its excessive energy consumption and higher financial costs than conventional fuel. Additional research and development (R & D) are needed to commercially achieve pyrolysis technology acceptable for liquid fuel production. The most fundamental challenges of this technological development are demonstrating, building the prototype, project permission, financial accessibility, pilot plant, and scale-up. The Government should prioritize non-conventional energy resources considering the emission and pollution and set the rules for approval of pyrolysis plants in any locality. Some of the crucial challenges are listed below for future pyrolysis research.

Social Acceptance: Since pyrolysis is still in the demonstration stage, many features of this technology are vague. So, people are unaware of this technology, the feedstock used, environmental impacts, cost, utilization of pyrolysis derived products, etc. In this respect, different NGOs, media, and researchers can play a crucial role by campaigning, advertisement in TV and newspapers, seminars, pilot plant demonstration, informing waste management benefits, etc.

Economic hurdles: The pyrolysis process still is not yet in commercial allocation due to its high production cost. This increased production cost makes it impossible to compete economically with fossil fuels. M.N Islam et al. [62] investigated rice husk conversion to pyrolysis oil and solid char. This research evaluated three different-scale fluidized bed reactors with feed rates of 0.3, 100, and 1000 kg/h. It concluded that the greater the plant size and lower the unit product cost and hence more economically suitable, whereas small plants dramatically increase the production cost. C. Eongkhorsub et al. [63] estimated that cost of 4500 L/day plant requires a total production cost of 202789.39 BDT (approximate 2368.41 dollars) from plastic derived pyrolysis oil and 91064 BDT (approximate 1063.55 dollars) for 2000 L/day tire waste pyrolysis. Profits from the sale of pyrolysis byproducts can be used to offset operational costs.

Technological limitations

Due to the scale-up limits of various heat transfer technologies, the fluidized bed reactor requires careful consideration for large-scale operation. In this case, the performance of bubbling fluid-bed pyrolizers is outstanding and reliable, with average liquid yields of 70–75 wt.% from wood on a dry-feed basis.

Due to the fact that char is an effective catalyst for vapor cracking in a fast pyrolysis process, it is vital to distinguish char quickly and precisely by ejection and entrainment. Systems such as transportable and Empyro bed reactors can reduce the residence time of the char circulating fluid bed (CFB).

In the case of fast pyrolysis, particle size should be small as the heat transfer rate limits the reaction rate through the biomass particles. As a result of ablation, high particle pressure on the hot reactor wall can be achieved through mechanical and centrifugal force means and high particle-to-reactor wall relative motion. In ablative pyrolysis, the wall temperature can be reached lower than 600 °C. There is no need for inert gas, and the equipment for the process is smaller, resulting in a more intense reaction system.

Another factor to think about is low thermal conductivity. Microwave pyrolysis is a more direct way of fast heating biomass than conventional pyrolysis. Because byproducts are far less likely to respond with pyrolyzed biomass, microwaves are expected to reduce secondary reactions.

Heat transfer to the reactor is one of the significant obstacles in commercial applications that may be overcome by using the energy of the byproduct charcoal, which is achieved by burning the char in the air. According to industry standards, char represents around 25% of total energy in the feedstock, and approximately 75% of that energy is needed to facilitate the achievement [64].

Upgrading Bio-oil: One of the important challenges is that pyrolysis oil cannot be used directly for power generation due to its physical and chemical properties such as corrosiveness, viscosity and stability [65]. As a result, the pyrolysis oil must be upgraded for storage and transportation; otherwise, it will cause damage to boilers, refineries processing equipment, and engines. Emulsion, filtration, solvent addition, distillation, Solid-phase extraction (SPE), Liquid-liquid extraction (LLE), chemical refining routes such as catalytic hydrogenation, fluidized catalyzed cracking, catalytic esterification, steam reforming; co-pyrolysis refining; and physical-chemical refining route are among the available upgrading technologies [66, 67].

Commercialization: Market launch and commercialization is the next most significant barrier. The Government should provide loans for the startup of pyrolysis oil production from waste to reduce petroleum demand. In Bangladesh, both the public and private sector power generation can use pyrolysis-derived products in combined heat power plants, boilers, turbines, etc. Not only the public but also the private sector should come forward in this respect. Also, the industry (for industrial heating, steam production, etc.) and individual consumers should be interested in using pyrolysis products.

Environmental concern: Since pyrolysis generates furans, sulfur oxides, dioxins, acid gases, sulfur dioxide, nitrogen oxides, particulates, etc., during the production of oils, ash, and char causes air pollution. The exhaust gas needs to be treated before releasing it into the atmosphere, which is also a crucial issue that should be kept in mind while installing any pyrolysis plant.

Industrial application

Numerous industrial sectors throughout the world use pyrolysis products for various applications, and they may also be beneficial for industrial uses in Bangladesh. The heat produced from pyrolysis oil by direct combustion in a boiler or furnace can produce heat in Bangladesh's steel, cement, brick, and glass factories. An investigation into the feasibility of utilizing pyrolysis fuel oil from tire waste as an industrial burner fuel was conducted in a case study [68].

For many years, Ensyn has used renewable fuel oil (RFO) for industrial heating applications. In 2014, Ensyn and Honeywell's UOP subsidiary combusted 20 million gallons commercially in various boilers and furnaces throughout Canada and the United States and various facilities operated by the public and commercial sectors in Europe, Brazil, and Malaysia. They determined that their pyrolysis technique is capable of mass producing RTP fuel at a price of $45 per barrel, a crude oil rival (of oil equivalent). Ensyn has recovered over 30 biochemicals from bio-oil, including flavoring compounds for culinary applications and sticky resins for the construction sector [69]. Battelle successfully met the challenge by producing commercially feasible transportation fuels from biomass pyrolysis at the United States Department of Energy on May 7, 2015, in, Ohio. On a single catalyst charge, researchers at Battele have demonstrated the long-term sustainability of a continuous hydrotreatment process that converts biomass pyrolysis into transportation and aviation fuels after 1,000 h of continuous hydrotreatment [70]. Additionally, the business developed a portable device in 2013 that utilizes catalytic pyrolysis to transform undesirable biomass resources such as agricultural waste or wood chips into valuable bio-oil. As-built, the Battelle-supported system can produce up to 130 gallons of wet bio-oil daily from a ton of sawdust, pine chips, and shavings [71]. Empyro, a pyrolysis oil production plant from the Netherlands, commenced in 2015. From 2017, the plant produces 24 tons of bio-oil per year. Aside from producing oil, the facility also generates enough energy to meet its own needs. The steam and oil produced by the plant are supplied to the neighboring salt factory and diary company (FrieslandCampina). The business intends to progressively expand production capacity to more than 20 million liters (5.3 million US gallons) of pyrolysis oil per year. This quantity of renewable oil would replace 12 million cubic meters of natural gas, the yearly usage of 8,000 Dutch families, resulting in a CO2 reduction of up to 20,000 tons per year [69]. Another plant-based on pyrolysis oil OPRA BV, located in the Netherlands, converts waste into pyrolysis oil and synthetic gas that can be utilized in gas or steam turbines to generate energy. In 2010, they performed combustion tests using BTG-BTL pyrolysis oil. OPRA is changing the combustion chambers of its gas turbine in response to these testing, enabling 100% pyrolysis oil firing [72]. Dynamotive, a Canadian pyrolysis company, built fast pyrolysis machines suitable for processing 130 metric tons per day in west Lorne (Ontario) and 200 metric tons per day in Guelph (Ontario). A 2.5 MW Orenda turbine driven by bio-oil generates energy for the Ontario grid at the West Lorne facility [73]. Fortum's new bio-oil factory in Joensuu, Finland, is the world's first to employ fast pyrolysis to manufacture bio-oil by using different kinds of wood as raw materials. The bio-oil plant is distinctive in that it is integrated with Fortum's Joensuu CHP4 facility. Waste wood from forests and other sources of biomass feedstocks, such as residues from the forestry sector, are used as feedstock, and the wood is sourced from within the Joensuu region. The annual production of 50,000 tons of bio-oil at the Joensuu bio-oil plant is enough to meet the heating demands of more than 10,000 households [74].

Limitations associated with MSW for energy, fuels application, and environment

The major problems associated with MSW are fuel conversion and application (waste gas clean up, conversion efficiency, regulatory hurdles, high capital costs, etc.). When MSW is utilized as a feedstock, the gas must be cleaned of tars and particles to obtain clean and efficient fuel from various processes (e.g., pyrolysis and thermal gasification). When combusted, the levels of nitrogen, sulfur, and ash species in MSW are unquestionably higher than those found in lignocellulosic feedstocks, and they produce criterion pollutants (e.g., nitrogen and sulfur oxides).

Since MSW has diverse elemental composition, the characterization methods of MSW need physical handling processes (e.g., separations, washing) for selective technologies that are sensitive to those species, which adds more cost. Besides a significant component of MSW having a greater moisture content, a substantial amount of energy is lost during the heating and drying processes (i.e., evaporating the water beforehand). Also, sometimes due to geographical location and season, the energy content found in MSW is very low. Due to air quality concern, the methods adapted increases regulatory hurdles and makes it expensive.

Plastic waste is the second most significant element of MSW. Both plastic and polythene waste seems potential candidate for the production of liquid fuels compared to agricultural and other MSW due to their high calorific value. Still, when compared with different categories of MSW and agricultural waste, plastic waste possesses some environmental drawbacks. Plastic waste emits toxic fumes when used as feedstock in pyrolysis. The liquid fuel generated from it is not as clean as a biofuel since plastic is almost entirely derived from petrochemicals manufactured from fossil oil and gas. On the other hand, biofuels from agricultural waste or different MSW categories of MSW such as paper and furniture waste are cleaner and produce lesser greenhouse gases (GHG emissions) and mitigate global warming [75].

Yet in terms of economic consideration, agricultural waste can be expensive to gather, transport, and store than plastic waste due to its high moisture content. Plastic waste is also cheaper than other categories of municipal waste such as glass, rubber, etc. However, the continuous disposal of plastic in landfill causes serious environmental problems as plastics are not biodegradable and take up to billion years to degrade naturally. So plastic waste to fuel conversion can effectively contribute to energy demand and waste management [76].

Most of the waste-to-energy conversion technology are expensive and have environmental and health hazards. Because incineration, gasification, and pyrolysis all fall under the category of thermal conversion, the detrimental effects of these technologies on the environment and the need for emission management have been highlighted in Table 3 along with possible solutions. Definitely, the ‘4Rs’—reusing, recycling, recovery, and reducing offer a more practical answer to solve the waste management problem. But some waste cannot be easily reused or recycled, and it's difficult to reduce consumption for the purpose of less waste generation. And then these waste to energy conversion technology might be the most sensible choice when disposing of these products. However, there is uncertainty whether this technology will become commercially viable within the near future. But still, there's a tremendous amount of innovation in this space at the moment, and it's essential to support it.

Conclusion

This ascertained the feasibility of producing liquid fuel from the selected feedstocks by pyrolysis conversion. Analyzing the characterization of selected agricultural residue, MSW and e-waste show that polythene is the potential candidate among the MSW for liquid fuel production due to higher heating value, hydrogen, and carbon components. For agricultural residue, jute stick can be an excellent feed material as it has the highest volatile matter and higher heating value among the agro residue. TGA study revealed weight loss of (42–60%) in the second zone for agricultural residues and furniture waste. In the active pyrolysis zone, paper and plastic waste lost weight at a rate of 77% and 90%, respectively. Plastic waste can reach 90% pyrolysis conversion (based on volatiles) at low-temperature intervals. According to these observations, all of the selected feedstocks exhibit substantial pyrolysis potential. They do, however, provide significant advantages over other criteria and may be beneficial for a specific purpose, such as environmental issues (agro residues) or waste management, as well as a greater calorific value (MSW). This is the first systematic report of selected eleven feed materials (agro residue, MSW and e-waste) considering their characterization and availability in Bangladesh. This study provides the baseline of future work on agro residue, municipal solid waste, and e-waste not only to pyrolysis conversion but also to other thermo-chemical conversion processes.

Declarations

Author contribution statement

Md. Kaviul Islam: Conceived and designed the experiments; Performed the experiments; Analyzed and interpreted the data; Wrote the paper.

Mst. Sharifa Khatun: Performed the experiments; Contributed reagents, materials, analysis tools or data; Wrote the paper.

Md. Arman Arefin: Analyzed and interpreted the data; Contributed reagents, materials, analysis tools or data; Wrote the paper.

Mohammad Rofiqul Islam: Performed the experiments; Wrote the paper.

Mehadi Hassan: Contributed reagents, materials, analysis tools or data; Wrote the paper.

Funding statement

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Data availability statement

Data will be made available on request.

Declaration of interests statement

The authors declare no conflict of interest.

Additional information

No additional information is available for this paper.