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The World Health Organization (WHO) has indeed highlighted the prevalence of traditional cooking practices and their impact on global health. Cooking with open fires or inefficient stoves can result in high levels of indoor air pollution, leading to respiratory diseases and other health issues. It is estimated that around three billion people, or approximately 40% of the global population, were reliant on such cooking methods at that time [1, 2]. According to estimates by the World Health Organization (WHO), approximately 4 million premature deaths occur annually due to household air pollution caused by traditional cooking devices. This global health issue disproportionately affects developing countries, where reliance on biomass fuels, such as wood, charcoal, or animal dung, for cooking is more prevalent [3]. It is important to remember that pollutant emissions into homes lower indoor air quality, resulting in a variety of diseases linked to solid-fuel inhalation, including high blood pres- sure, acute respiratory infections, cataracts, blindness, low birth weight, infant mortality, and, in particular, chronic obstructive pulmonary disease [ 4 , 5 ]. Indoor air pollution from the combustion of solid fuels, such as wood, coal, or biomass, is a significant health concern in many parts of the world. Prolonged exposure to indoor smoke can lead to respiratory problems, including chronic obstructive pulmonary disease, acute respiratory infections, and other adverse health effects. These risks are especially pronounced for women and children, as they often spend more time indoors in proximity to the source of pollution [6]. 

Biomass can be derived from agricultural and forestry waste, as well as from organic waste generated by industries and households. By using biomass as an energy source, these waste materials can be effectively managed and utilized, reducing the burden on landfills and contributing to waste reduction efforts. Biomass can be converted into various forms of energy, including heat, electricity, and liquid and gaseous fuels. It can be used in residential, commercial, and industrial applications, making it a versatile energy option. Biomass energy production can create jobs and support local economies, particularly in rural areas where biomass feedstocks are abundant. Harvesting, processing, and transporting biomass materials require a labor-intensive workforce, providing employment opportunities for local communities’ fuels [7]. Using biomass as an energy source can indeed help reduce greenhouse gas emissions, particularly carbon dioxide, when compared to the use of fossil fuels. Biomass refers to organic matter derived from plants, animals, and other biological sources, such as agricultural residues, forestry waste, dedicated energy crops, and even organic municipal waste [8]. Direct combustion of biomass releases harmful pollutants such as particulate matter, carbon monoxide, and volatile organic compounds, leading to indoor air pollution. Biomass briquettes, on the other hand, produce less smoke and emissions when burned, resulting in improved indoor air quality and reduced health risks for individuals using them for cooking and heating [9]. Dense solid biomass derived from agricultural residues can present various challenges due to its physiochemical properties, including moisture content, ash content, and flow characteristics. These factors can significantly impact the energy density, combustion quality, and combustion temperature [10]. The ash content of agricultural residues plays a significant role in the briquetting process. Agricultural residues with an ash content of less than 4% are preferred for briquetting because they have a reduced slagging potential. Slagging refers to the formation of molten or partially fused ash deposits during combustion, which can negatively affect the efficiency and performance of the briquettes [11]. Another benefit is the presence of lignin, a natural binder found in plant cell walls. Lignin is a complex organic polymer that acts as glue, holding the biomass particles together during densification. It has a melting point around 140°C and exhibits thermosetting properties, meaning it softens and melts when heated but solidifies and forms a rigid structure upon cooling [12]. In biochemical conversion processes, biological activity is employed to convert biomass into alcohol or oxygenated products. Microorganisms, such as bacteria or yeast, are used to ferment biomass feedstocks and produce biofuels like ethanol or butanol. It's important to note that different conversion processes have varying outputs and efficiencies. Pyrolysis tends to produce a higher quantity of gases, tar, and solid residue (char), while gasification primarily generates gases with a smaller amount of char and ash. The specific choice of conversion process depends on the desired end products and the characteristics of the biomass feedstock being utilized [13]. The primary organic components of biomass are cellulose, hemicelluloses, and lignin. Cellulose, with a general formula of (C₆H₁OO5)n, is a complex carbohydrate and the main structural component of plant cell walls. It forms a strong and rigid structure in biomass but is insoluble in water [14]. Liquefaction is indeed a thermochemical process that converts a substance from its gaseous or solid state into a liquid state. It typically involves subjecting the substance to low temperatures and high pressures to induce the phase change [15]. More than one-third of the world’s populations (2.8 billion people) rely on various forms of solid fuels (firewood, charcoal, dung, residues, etc.) and kerosene in meeting their energy needs [16].  The lack of access to cleaner cooking devices and the inability to afford clean cookstoves are significant factors contributing to the problem of household air pollution (HAP) in many parts of the world. HAP refers to the pollutants emitted from burning biomass fuels such as wood, charcoal, animal dung, and crop residues in traditional cookstoves or open fires. These traditional cooking methods release large quantities of harmful pollutants, including fine particulate matter (PM2.5) and carbon monoxide (CO), among other toxic substances [17]. Nitrogen dioxide (NO2) is a harmful gas that can have adverse effects on human health, particularly on the respiratory system. The World Health Organization (WHO) has established guidelines for acceptable indoor hourly and annual exposure limits to NO₂ to protect public health. As per the WHO indoor hourly exposure limit for NO₂ is set at 163 parts per billion (ppb), and the annual exposure limit is set at 33 ppb [18]. Cardiovascular disorders, including high blood pressure (hypertension), can affect both men and women However; certain factors can make women more susceptible to developing high blood pressure [19, 20],  as well as 3.2 million premature deaths per annum as of 2020 [21].

2.1 Biomass collection

The study's basic materials included maize cobs, rice husk, cocopeat, saw dust and binders including corn starch .maize cobs were gathered from mungeli farm fields, rice husk from a rice mill, sawdust was gathered from a sawmill, and cocopeat was gathered from a nearby market. The reason why the residues and binders were selected is that they are frequently thrown or flared, posing risks to both human and ecological health. They are also produced in vast quantities, are simple to obtain, inexpensive, and easily available.

2.2 Raw materials

The raw materials used in the preparation of briquettes include corncob, rice husk, sawdust and coco peat.

2.2.1 Grinded maize cobs

A byproduct of the maize crop, maize cobs are a lignocellulosic plant material that is rich in energy and organic elements. For every tonne of maize that is shelled, about 180 kg of cobs are produced (Evers et al., 1994). However, lignin (5.6%), water soluble carbohydrate (1.1%), and protein (2.5%) are observed to be present in maize cobs. During densification or briquetting, these compounds have a significant role in the formation of solid bridge linkages (Kaliyan and Morey, 2010).

Fig. 1 Grinded maize cobs

2.2.2 Sawdust

Different types of wood can produce sawdust particles of varying sizes. Generally, sawdust particles range in size from 0.3 to 0.6 mm. However, it's important to note that this is a general range and can vary depending on factors such as the type of wood, the cutting or grinding method used, and the equipment involved in the wood processing.

Fig.2 Sawdust

2.2.3 Cocopeat

Natural fibre called cocopeat is derived from the husk of coconuts. Cocopeat is the byproduct of coconut husk extraction. For the production of various products like cocopeat tablets, blocks, briquettes, and more, cocopeat is sun-dried. Cocopeat contains 1.14% silica, 22.05% fixed carbon, 6.14% ash, 71.80% volatile matter, and 14–20% moisture.

Fig.3 Coco peat

2.2.4 Rice husk
The composition of rice husk can vary, but on average, it contains approximately 60-65% volatile matter, 10-15% fixed carbon, and 17-23% ash. Volatile matter refers to the substances that can easily vaporize, while fixed carbon refers to the solid carbonaceous material remaining after volatile matter has been driven off. Ash represents the inorganic mineral content in the husk.

Fig. 4 Rice husk

2.2.5 Preparation of composition for biomass briquettes production

Briquetting is the process of exerting pressure on a mass of particles, with a binder, to create a compact product with superior burning properties, a high bulk density, and a low moisture content. By combining them with corn starch, the main ingredients employed in the creation of briquettes were rice straw, rice husk, cocopeat and sawdust. The treated mixture was fed into the briquette-making machine to prepare the briquettes. The generated wood was then dried for 3-4 days in the sun at 32°C. Briquettes in their dried form provide for the ideal firewood substitute.

i. Materials with a moisture content of 10-15% are suitable for briquetting, but higher moisture content materials must be dried out.

ii. The material is screened, cut, and ground before being pneumatically transferred into storage bins to unify the moisture content and separate heavier and matchlock particles.

iii. To create ground particles, raw material is put into the hammer mill of the briquetting machine.

iv. Compression increases the material's temperature, softening it and forming intrinsic binders that unite the substance.

v.It is possible to obtain briquettes with a diameter of 40 mm.

Table 1:  Different composition of raw material for making briquettes

Composition	Treatment	Ratio
Corncob:Rice husk	L1	50: 50
	L2 L3	60: 40 40: 60
Corncob:Sawdust	L4	50: 50
	L5	60: 40
	L6	40: 60
Corncob:Coco peat	L7	50: 50
	L8	60: 40
	L9	40: 60

Analysis of Mixture of different raw material

Proximate and Ultimate analysis of fuel was carried out in order to investigate the feed stock characteristics. The sample was heated in an oven at 105.5 °C for 24 h or until constant mass is obtained, the moisture content (MC) was determined using ASTM D 3173–87 method [22]. The volatile matter (VM) was also evaluated using 1 g of sample dried in muffle furnace at 600 °C ± 50 for 6 min according to method ASTM D 3175–07 [ 22 ]. The ash content was determined using method ASTM D 3174–04, which removes organic elements at high temperatures in a furnace at 700 °C.

The value of fixed carbon (FC) was indirectly obtained by using the equation:
FC = 100 – (VM + MC + Ash)     ………………… (1)

3.1 Water boiling test (WBT)

A modified water boiling test was carried out to assess thermal performance improved biomass briquettes. The usual Water Boiling Test (WBT) was used to measure the thermal efficiency of the biomass briquettes (WBT). It is a basic tool that assesses how efficiently a stove uses fuel to heat water in a cooking pot and the amount of emissions created as a result. The ratio of heat energy entering the cooking pot to the energy content of the fuel consumed is known as the thermal efficiency of cook stove. The heat that enters the cooking pot has two quantifiable effects; one it raises the temperature of the water from room temperature to boiling point and other it evaporates the water. A known amount of water is heated in the stove in the standard WBT. The amount of water evaporated after complete burning of fuel is used to calculate efficiency using.

Table 2:  Water boiling test

Treatments                                    Water boiling test
	Fuel taken  (g)	Avg. time taken to burn (min)	Avg. water boiling time  (min)	Avg. water evaporated  (ml)	Avg. ratio of water evaporated to fuel used (ml/g)
L1	300	6.34	21.65	127.36	0.42
L2	300	7.56	23.93	130.86	0.44
L3	300	6.94	23.16	129.56	0.43
L4	300	8.38	26.25	210.42	0.7
L5	300	8.11	23.67	165.13	0.5
L6	300	7.89	22.87	137.76	0.46
L7	300	7.3	21.86	129.27	0.43
L8	300	7.92	24.2	145.41	0.48
L9	300	7.54	23.64	141.74	0.47

According to the above table, the briquette was entirely burned in the locally available cook burner and produced a consistent flame. Biomass briquettes combination L4 had a higher burning rate and a greater amount of water evaporated and fuel utilized ratio than other combinations.

3.2 Analysis of physical characteristics of the prepared biomass briquettes

Fig. 5 physical characteristics of the prepared biomass briquettes

Bulk dry briquette density was found to be low in sample L3 at 290 kg/m³ and high in sample L4 at 610 kg/m³. Higher densified briquettes have longer burned times and greater transporting strength. Moisture content was found to be low in sample L4 at 2.75 % and high in sample L7 at 5.03 %. Lower moisture content of biomass briquettes have larger thermal efficiency and release very small amounts of pollutant gases. The amount of Solid content was found to be low in sample L2 at 94.14 % and high in sample L4 at 98.1 %. Higher solid content of biomass briquettes have lager combustion efficiency and it help in the easily burning of biomass briquettes
3.3 Analysis of calorific value of biomass briquettes

Fig.6 Calorific value of the prepared biomass briquettes

In above figure shows that among the nine prepared samples, Sample L4 was found to have the highest calorific value when compared to the other combinations which was 18 MJ/kg. However, it is important to note that wood charcoal had the highest calorific value among all the tested samples, with a value of 34.86 MJ/kg.
3.5 Proximate analysis of biomass briquettes

Fig.7 Proximate analysis of the prepared biomass briquettes

The percentage by weight of fixed carbon, volatiles, ash and moisture content in the samples were determined by the quantity of fixed carbon and volatile combustible matter present in the fuel. The ash content is a significant parameter in determining the design of furnace grate, combustion volume, pollution control equipment and ash handling system. From above figure it can be concluded that the biomass briquettes combination L4 is suitable for domestic applications. The fixed carbon of the biomass briquettes combination L4 was 47.95%, which is high as compared to the other samples. Heat generation is promoted by the presence of fixed carbon whereas high volatile matter content promotes easy ignition of fuel. When fixed carbon was high then gaseous pollutants such as CO, particulate matter, and other pollutants are very less. The ash content of the biomass briquettes combination L4 was 3.69%, which is less as compared to the other samples. High ash content can affect combustion efficiency, causes fouling, and impact emissions. When the ash content is less combustion efficiency is more. Moisture content represents the amount of water present in the fuel. Moisture in biomass or other fuels has a negative impact on their combustion efficiency because energy is required to evaporate the water before combustion can occur. The moisture content is typically determined using methods such as the oven dry method (ASTM D-3173), where the fuel sample is heated in an oven to remove all moisture. The moisture content of the biomass briquettes combination L4 was 2.75%, it was very less so that the combustion efficiency is more. The volatile matter of the biomass briquettes combination L4 was 45.6%. Volatiles are combustible materials that evaporate or vaporize when the fuel is heated. They contribute to the ignition and flame stability of the fuel. Fuels with higher volatile matter content tend to ignite more easily.

3.6 Thermal efficiency analysis of the prepared biomass briquettes

Fig. 8 Thermal efficiency of the prepared biomass briquettes

In above figure shows that among the nine prepared samples, Sample L4 was found to have the highest thermal efficiency value when compared to the other combinations which was 28%. Thermal efficiency was calculated by following formula (Rathore, 2008).

Where,

Wi= Initial weight of water,kg ,                      Cp = Specific heat of water J/kg°C (4.187 kJ/kg°C)

T ₂ = Final temperature of water, °C           T₁ = Initial temperature of water, °C

W_f = Final weight of water taken, kg              I = Latent heat of water (540 kcal/kg or 2266kJ/kg)

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