1 Introduction

Globally, 2.5 billion people, or one-third of the world's population rely on the traditional use of solid biomass to cook their meals [1]. The worldwide domestic biomass supply in 2019 was 56.9 EJ. Solid biomass sources, such as wood chips, wood pellets, and traditional biomass sources, accounted for 85% of the domestic supply. 1.93 billion m3 of wood fuel was produced globally in 2020. Asia had the highest share of wood fuel production with a contribution of 37% [2]. Thereafter, Bangladesh is a greatly environmentally hazardous country suffering from a high deficiency of fuels, particularly biomass fuels. Moreover, the rural people of Bangladesh depend mainly on biomass fuels, namely wood, leaves, twigs, bark, roots, bamboo, shell and coir of coconut, agricultural residues such as rice husk, straw, jute stick, bagasse, and cow dung for their domestic consumption [3, 4]. Biomass plays an important and complex role in Bangladesh, particularly in rural areas where approximately 74.5% of the population lives [5]. However, the efficiency of biomass fuel in the overall primary energy supply is about 60% in Bangladesh [6]. Besides, the country has only 11% of its total land under forest [7], and the surviving forests are losing tree cover at an alarming rate [8]. At the same time, the deforestation rate is the highest of any other country in the world [9]. Again, Bangladesh is one of the most densely populated countries in the world [10]. Due to the rising growth of the population, the per capita energy consumption in Bangladesh increased from 5 GJ (gigajoules) in 1977 to 6.2 GJ and 8.98 GJ in 2009 and 2012 respectively [11,12,13]. Thus, the phenomenon of high population growth as well as growing energy demand reveals unlimited pressure on biomass, when burning more biomass imparts adverse impacts to the environment.

A potential cause of gaseous and particulate matter emissions to the troposphere is burning biomass [14, 15]. Globally, burning biomass generates around 20–30% of the CO2 emissions as well as chemically active gases such as hydrocarbons, CO, and NOx [16]; burning biomass also results in approximately 42% of the world's black carbon and 74% of the world's primary organic carbon (OC) [17]. These compounds have a severe impact on air quality, atmospheric chemistry, climate change, and human health [18,19,20,21,22,23]. Furthermore, pollutants from household biomass burning can result in more than 1.6 million deaths each year [24]. Biomass smoke particles are composed of ̴ 50–60% organic carbon and ̴ 5–10% black carbon [23]. The impacts of smoke particles are suspected to be numerous, spanning from mesoscale to individual [25]. Increased smoke particles may result in smaller cloud droplets, which can also change cloud brightness [26] and persistence [27]. Radiative interactions caused by smoke particles can potentially alter the amount of sunlight accessible for agriculture [28] by reducing visibility [29, 30] and surface irradiance [31, 32]. Indoor smoke exposures are one of the biggest public health risks in developing countries, is to account for respiratory problems and air pollution [33].

Nevertheless, more than half of the world's people live in the rural areas of developing countries where the majority of them depend basically on biomass fuels for their energy supply and have no access to modern forms of energy [34]. Again, most of the people in Bangladesh live in rural areas [35], and use biomass as their primary energy carries instead of using commercial fuel due to higher running costs and lower economy [22, 36]. On the other hand, a large majority of them use relatively inefficient cooking stoves for biomass-based cooking, whose emissions cause hazardous gases that lead to indoor air pollution, human health risks, and substantial carbon dioxide emissions to the atmosphere [20, 22].

In Bangladesh, a number of studies have been conducted on the consumption pattern of biomass fuels. Akther et al. [37] investigated the biomass fuel consumption pattern in the countrified region of the Meghna floodplain zones of Narsingdi district, Nath et al. [38] conducted study in degraded Sal (Shorea robusta) forest areas in Dhaka, Gazipur, Mymensingh and Tangail districts, Miah et al. [39] studied at Chandanaish upazila of Chittagong district, Jashimuddin et al. [36] did study in Chittagong and Noakhali district, Baul et al. [40] investigated in the suburban region of Chittagong.

Although, some studies are conducted in Bangladesh on the status of energy and biomass fuel consumption depends on many socioeconomic and demographic factors in several regions of the country [20, 22, 37,38,39]. Whereas, the updated biomass consumption patterns in Khulna district are limited. After that, we thoroughly examined it by posing three research questions, such as,

  1. 1.

    How much and what types of biomass are consumed by the households in the study area?

  2. 2.

    How different socio-economic factors affecting its consumption level?

  3. 3.

    What are the types of sources and end uses of biomass fuels, and what are the common species at the household level and most preferred fuel wood species used for cooking purposes?

However, it is urgently necessary to use biomass-based energy through appropriate biomass energy-saving technologies, such as biogas and sustainable energy support for the environment [41, 42]. Therefore, it is needed to the development of biomass production and its utilization with the formulation of a biomass-based rural energy policy in rural Bangladesh. The present study may lead to planning and decision-making for biomass-based energy services. This endeavor is additionally planned to describe possible options that provide environmentally friendly energy services using locally accessible biomass sources.

2 Materials and methods

2.1 Survey procedure and data collection

This study comprised a socio-economic survey on the household energy consumption pattern in the selected areas of the Khulna district of the southwestern part of Bangladesh. Bangladesh is divided into 64 districts (administration division managed by the local government), and Khulna is an important district in the south-western part of Bangladesh. It is located between 21°41' and 23°00' north latitudes and between 89°14' and 89°45' east longitudes [43].

The study involved a socio-economic survey on household energy consumption pattern in the selected three upazilas (Table 1) of southwestern part of Bangladesh. Prior to the final survey, a preliminary reconnaissance survey was conducted to know the overview of the study area. Finally, the study was conducted through a multistage random sampling technique using a semi-structured questionnaire from February 2018 to July 2018. The sequence of sampling was from upazila to union council (smallest rural administrative unit under upazila), from union to village, and then from village to households. Two unions from each upazila, two villages from each union, and ten households from each village were randomly selected. Kharnia and Bhandarpara union from Dumuria upazila, Batiaghata and Jalma union from Batiaghata upazila, and Haridhali and Lata union from Paikgachha upazila were randomly selected. From Kharnia union, Boratia and Bahadurpur villages, from Bhandarpara union, Bhandarpara and Sahosjoykhali villages, from Batiaghata union, Kesmotfultala and Borofultala villages, from Jalma union, Jhorvanga and Sachibunia villages, from Haridhali union, Gadhaypur and Sonatonkathi villages and from Lata union, Pana and Putimari villages were selected for the study. The reconnaissance survey indicated that on average 12% of the households were found to be rich, 57% of them were middle class and 31% of them were poor.

Table 1 Profile of the study area
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The respondent was asked to provide socio-economic information such as family size, occupation, education level, total land holding, type of housing, and monthly income. Subsequently, they were requested to provide information on types and sources of energy use, monthly consumption of different energy fuels, types and sources of biomass fuels, monthly consumption of various biomass fuels, types of use of biomass fuels, monthly expenditure for different energy fuels, type of stoves used for domestic cooking, name of the common tree species at household level, and name of the most preferred fuel wood species.

Thus, in this study, a total of 120 households, 40 from each upazila were selected randomly. The list of selected unions and villages for the study is given in Table 2. The surveyed household who seem to provide confusing information were also cross-checked with the help of other neighboring people and key person of the society. The questionnaire can be available via journal’s authority upon request.

Table 2 Selected union and villages for the study
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Based on household income, the households were broadly categorized in to three income group namely poor, middle class, and rich denoted by G1, G2 and G3 respectively, where G1 =  ≤ 10,000 BDT (≤ 119.44 USD), G2 = 10,000–19,000 BDT (119.44–226.94 USD) and G3 =  ≥ 19,000 BDT (≥ 226.94 USD) based on August 2018 rates. The literacy of the household was divided into four categories, i. e. illiterate, primary, secondary and above secondary. The illiterate was coded with 0 followed by primary as 1 to 5, secondary as 6 to 10 and three categories for above secondary named higher secondary, graduate, and post graduate as 12, 16 and 17 respectively. To conduct this study we followed the methodology of some other published studies [20, 36, 39].

To calculate the physical quantities of various energy consumption three physical units were used, e.g. kilogram (kg) for biomass and candle, kilowatt hour (kW-h) for electricity and liter (l) for kerosene and LPG. The data processing and analysis were carried out with IBM SPSS Statistics 23. The statistical analysis (ANOVA) was used to know statistically significance difference among the variables. Then the multiple comparison test (post-hoc ANOVA) was used to look the specific differences between them.

3 Results

3.1 Consumption of biomass and non-biomass fuels

Biomass, electricity, liquefied petroleum gas (LPG), kerosene and candle were found as the energy used in the rural households of the Khulna district. The study showed that households used different energy sources like biomass 97%, electricity 90%, LPG 22%, kerosene 57%, and candles 48%. The average monthly consumption of energy was 192.53 kg biomass, 64.65 kW-h electricity, 1.84 L LPG, 0.74 L kerosene and 0.06 kg candle per household. In particular, biomass consumption between Batiaghata (144.14 kg), Paikgachha (146.87 kg), and Dumuria (286.60 kg) upazila (sub-district) significantly (p < 0.05) differed. Again, there were significant (p < 0.05) differences in kerosene consumption comparing Batiaghata (0.20 L), Paikgachha (1.51 L), and Dumuria (0.52 L) upazila. On the other hand, the access of grid electricity was found highest at 86.70 kW-h in Batiaghata upazila, but such access was lowest at 30.20 kW-h in Paikgachha upazila and medium in Dumuria upazila at 77.07 kW-h, with significant (p < 0.05) differences (Table 3).

Table 3 Consumption of biomass and non-biomass fuels in the Khulna district of Bangladesh
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The average consumption of biomass fuels household−1 month−1 was found to be highest in medium income group. The average consumption of biomass fuels among poor, medium and rich households were about 160.81 kg month−1, 245.20 kg month−1 and 171.60 kg month−1 respectively. Both the average consumption of electricity and LPG household−1 month−1 were highest in high income group and lowest in low income group. For the households of high income group, the average consumption of electricity and LPG was found to be 73.80 kw-h month−1 and 4.48 L month−1 respectively, while it was 50.75 kw-h month−1 and only 0.15 L month−1 respectively for the households of low income group. There was no remarkable difference in monthly kerosene and candle consumption between the income groups of the study households. The average consumption of kerosene among poor, medium and rich households was 0.85 L month−1, 0.64 L month−1 and 0.74 L month−1 respectively. Furthermore, the average consumption of candle in poor households was only 0.06 kg month−1, such consumption in medium and rich households was 0.08 kg month−1 and 0.03 kg month−1 respectively. The consumption of biomass and LPG among different income groups were significantly different (df = 2; df = 4.85 and 14.49 respectively; p < 0.01) (Table 4).

Table 4 Consumption of biomass and non-biomass fuels by different income groups in the Khulna district
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The consumption of different biomass in the rural households of the Khulna district of Bangladesh is presented in Table 5. It was found that firewood was used by 97% of households, leaves and twigs by 82%, shell and coir of coconut by 76%, rice husk by 23%, crop residues (i.e. rice straw, pulses, anise, bagasse, jute stick) 32% and cow dung by 68%. Whereas, 55% of the households used multiple biomass materials (e.g. root, bark, shell and coir of fan palm and bamboo etc.) which are termed as ‘others’. Among the biomass fuels, the consumption of firewood was highest (105 kg), followed by that of cow dung, leaves and twigs, shell and coir of coconut, crop residues and rice husk, respectively. The consumption of firewood was found to be highest at 166 kg per household per month in Dumuria upazila and lowest at 69 kg in Paikgachha upazila. Regarding the regions, no significant differences (p < 0.05) were found in the consumption of leaves and twigs and rice husks. However, significant differences were found for the consumption of firewood, coconut, crop residues and cow dung (df = 2; F = 7.49, 4.72, 5.09 and 4.05 respectively; p < 0.05) (Table 5).

Table 5 Consumption of different biomass fuels by households in the Khulna district of Bangladesh
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Among the poor, medium and rich housing types, the monthly highest firewood consumption was found in medium type households compared to poor and rich types. The consumption of firewood in poor, medium and rich households was 74 kg month−1, 140 kg month−1 and 101 kg month−1 respectively. The consumption of cow dung was found highest in medium type households as 52 kg month−1, whereas it was lowest in rich type households as 42.00 kg month−1 respectively. The households who had limited access to firewood, mainly dependent on leaves and twigs, roots, bamboo and shell and coir of coconut and fan palm for their biomass fuels. However, monthly average consumption of leaves and twigs was found highest in poor categories households as 24 kg month−1 and lowest in rich categories households as 14.20 kg month−1 . The monthly average consumption of coconut, rice husk and crop residues was found highest in medium categories households as 10.75 kg month−1, 2.85 kg month−1 and 7.25 kg month−1 respectively. The consumption of firewood among different income groups were significantly different (df = 2; F = 5.09 respectively; p < 0.01) (Table 6).

Table 6 Consumption of different biomass fuels by different income groups in the Khulna district
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3.2 Expenditure of biomass and non-biomass fuels

On average, the rural households spent USD 12.11 (5.56% of their income) for their supplementary energy supply, of which biomass (USD 5.86) contributed more compared to non-biomass fuels. Concerning non-biomass fuels, the expenditure was highest for electricity USD 3.75 and lowest for candles USD 0.21. The expenditure on biomass fuel was considerably high in Dumuria upazila at USD 8.24 per household per month. The expenditure of electricity per household per month was considerably highest in Batiaghata upazila at USD 5.26 and lowest at USD1.52 in Paikgachha upazila. The average monthly households’ expenditure of LPG in Batiaghata, Dumuria and Paikgachha upazila was found USD 2.79, USD 1.10 and USD1.24 respectively. While the expenditure on kerosene was highest at USD 1.17 in Paikgachha upazila and for candles, the expenditure was found highest at USD 0.31 in Batiaghata upazila (Table 7).

Table 7 Expenditure of biomass and non-biomass fuels in the Khulna district of Bangladesh
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Among the three income groups, the average monthly expenditure of the high income group households was found highest mainly for using electricity and LPG. The high income group spent nearly double energy supply than low income group. The average monthly expenditure of biomass fuels in poor, medium and rich households was found USD 4.59, USD 7.78 and USD 5.21 respectively. The average monthly expenditure of electricity and LPG was found highest as USD 4.48 and USD 4.16 respectively in rich households and lowest as USD 2.85 and USD 0.14 respectively was found in poor households. The average expenditure of kerosene in poor, medium and rich households was found USD 0.65, USD 0.50 and USD 0.58 month−1 respectively. Furthermore, the average expenditure of candle was highest as USD 0.29 in medium households and lowest as USD 0.12 in rich households. There were significantly differences in the expenditure of biomass and LPG among rich, medium and poor households (df = 2; F = 7.04 and 14.50 respectively; p < 0.01) (Table 8).

Table 8 Expenditure of biomass and non-biomass fuels by different income groups in the Khulna district
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Regarding biomass fuels, the households spend the highest amounts on firewood USD 4.03 and the lowest on rice husk USD 0.09. The average monthly expenditure of firewood per household per month was found to be highest at USD 5.78 in Dumuria upazila and lowest at USD 2.86 in Paikgachha upazila. The average monthly household expenditure of cow dung and leaves and twigs was found highest at USD 1.15 and, USD 0.53 respectively in Dumuria upazila and lowest at USD 0.52 and USD 0.29 respectively in Batiaghata upazila. The monthly average household expenditure of shell and coir of coconut was highest at USD 0.19 in Dumuria upazila and lowest at USD 0.08 in Paikgachha upazila. However, the crop residues expenditure per household per month in Batiaghata and Dumuria upazila was USD 0.23 and USD 0.21 respectively, whereas in Paikgacha upazila no household uses crop residues as fuel (Table 9).

Table 9 Expenditure of different biomass fuels in the Khulna district of Bangladesh
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The average monthly household expenditure of firewood in poor, medium and rich households was found USD 2.85, USD 5.26 and USD 3.98 respectively. Furthermore, the average monthly household expenditure of cow dung was found highest as USD 0.89 in medium type households. However, monthly average expenditure of leaves and twigs was found highest as USD 0.52 in poor categories households and lowest as USD 0.30 in rich categories households. The average monthly expenditure of shell and coir of coconut was found almost similar as USD 0.14 and USD 0.15 in both poor and medium type households, while it was lowest as USD 0.08 rich housing types. The result showed that the consumption of firewood among different income groups was significantly different (df = 2; F = 5.25; p < 0.01) (Table 10).

Table 10 Expenditure of different biomass fuels by different income groups in the Khulna district
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The study relevant with the households, where 36.67% of them were Kacha (clay) type followed by 33.33% Semi-pucca (brick and clay) and 30% Pucca (brick and cement) type. The study showed that the total land of the Pucha type households was found highest as 2.35 acre, while it was found to be lowest both in Kacha type households having 0.58 acre. Similarly, the dwelling size of the Pucha type households was found highest, 0.18 acre, while it was lowest, 0.09 acre for the Kacha type households (Table 11).

Table 11 Housing types and fuels consumption by rural households
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The consumption of energy per month was found to be different for different housing pattern. For biomass, the Kacha type households had the highest, 204.70 kg, while it was lowest, 175.50 kg for Semi-pucca type households. For electricity and LPG, the highest consumption was found in Pucca type as 97.23 kw-h and 4.65 L respectively, whereas the households of Kacha type had the lowest as 46.60 kw-h and 0.27 L respectively. For the consumption of kerosene, the households of Kacha type had the highest as 0.90 L, whereas the lowest consumption was found in Pucca type as 0.54 L. For candle consumption, the same amount, 0.05 kg was used by the households of Kacha type and Semi-pucca type followed by 0.07 kg by Pucca type households. (Table 11). The average family size was found 5.10 with maximum of 15 and minimum of 2. Both the median and mode of the family size were found to be 4.5.

It was observed that the education status was positively correlated with using the modest form of energy. In the study area, every household used grid electricity to which had access to them. The households used LPG had highest literacy score as 11.23 followed by using candle as the next highest literacy score as 8.48. The average consumption of biomass, electricity and kerosene had 7.77, 7.62 and 7.82 literacy score respectively. The result showed that the consumption of biomass and LPG among different literacy level were significantly different (df = 2; df = 2.50 and 2.65 respectively; p < 0.01) (Table 12).

Table 12 Fuel consumption and literacy of the household respondents
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3.3 Sources of biomass fuel

In the study area, households in general collected biomass fuels mainly from their homesteads and/or agricultural lands. It was also found that people collect biomass from the local market. The study showed that 76.66% of the households collected stems from their homesteads and/or agricultural lands, 25% from the temporary market, 30% from the permanent market and 10% from the roadside plantation. About 65% of the households collected branches from their homesteads and/or agricultural lands, 20% from the temporary market, 8.33% from the permanent market and 13.33% from the roadside plantation. Besides, stems and branches, cow dung was found the most prominent biomass fuel based on its use. About 52% of the households collected cow dung from their homesteads and/or agricultural lands, whereas 18.33% were from the temporary market and 20% from the permanent market. Only 70% of the households used leaves and twigs as fuel collected from their homesteads and/or agricultural lands, whereas 28.33% from the temporary market and 16.66% from roadside plantations (Table 13).

Table 13 Sources of biomass fuels for the rural households in the Khulna district of Bangladesh
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3.4 End uses of biomass fuel

Table 14 showed the end uses of biomass fuels by the households in the study area. Most rural households used biomass fuel for domestic cooking. The biomass fuel was also used for paddy parboiling, molasses making and other purposes (i.e. making smoke in the cow shed). About 96.66% of the households used stems for domestic cooking, whereas for the same purposes, 85% used branches, 81.66% used leaves and twigs, 76.66% used coconut, 23.33% used rice husk, 33.33% used crop residues, 68.33% used cow dung and 53.33% used other biomass resources. For paddy parboiling, 3.33% of the households used firewood, 6.66% used branches, 8.33% used leaves and twigs, 10% used rice husk and 5% used crop residues. Making molasses, 8.33% of households used firewood, 6.66% used branches and 5% used cow dung.

Table 14 End uses of different biomass fuels by the households in the Khulna district of Bangladesh
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The study also found that about 2.25 tons (97.79%) of biomass household−1 year−1 used for domestic cooking, whereas biomass of only 0.02 tons (0.87%) was used for paddy parboiling, 0.023 tons (1%) was used for molasses making and 0.008 tons (0.34%) used for other uses.

3.5 Type of stoves used for domestic cooking

Different cooking materials were used for domestic cooking in their households. About 88.33% of the households used general stoves, 10% used improved cooking stoves, 22.5% used LPG, 28.33% used electric cooker and only 1.66% used biogas for domestic cooking (Fig. 1). Only two households use biogas plant in the study area. They don't use any other types of fuels in their households except cow dung.

Fig. 1
figure 1

Different cooking materials used for domestic cooking by rural households

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3.6 Common tree species at household level and tree species used as biomass fuel

A total of 54 tree species were identified by the respondents from the study area. The main difference between commonly available species at household level and preferred fuel wood species was that the species that were ordinarily planted in their locality as known as commonly available species and the species which were preferred by the households for burning value, strong fire, long-lasting embers as well as fast growing tree species known as preferred fuel wood species. Based on commonly used characteristics, a list of 36 species is presented in Table 15. Generally they raised tree species in their homestead for the production of timber and fuel wood. They also raise tree besides their agricultural land as well as other marginal lands. The species including both fruit trees, palm trees, timber species as well as fast growing species were identified as common tree species at the household level in the study area (Table 15).

Table 15 Common tree species at the rural household level
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Based on overall preferences, the ten most preferred firewood species identified by the respondents are presented in Fig. 2. Raintree (Albizia saman) was the most preferred tree species in the study area. Coconut (Cocos nucifera), Am (Mangifera indica), Mahagoni (Swietenia macrophylla), Tentul (Tamarindus indica), Akashmoni (Acacia auriculiformis), Tal (Borassus flabellifer), Boroi (Ziziphus mauritiana), Sil koroi (Albizia procera) and Chambol (Albizia richardiana) are also preferred by the households ranked after Raintree (Fig. 2). Households used both stem wood and leaves of these species as fuel purposes.

Fig. 2
figure 2

Preferred species used as fuel by the rural households in the Khulna district of Bangladesh

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4 Discussion

4.1 Biomass fuels consumption

The present study showed that biomass fuel is used more frequently as the cooking fuel in rural households than any other form of commercial fuel. Besides biomass, electricity, LPG, kerosene, and candle were used as commercial fuels in the study area corresponds with the previous studies in rural Bangladesh [22, 39, 44]. However, the average consumption of biomass fuel in the study area was found 192.53 kg per household per month, which is somewhat similar to the findings of 218 kg per household per month reported by Hassan et al. [20] from four upazilas (Kalaroa, Nachole, Nakla, and Chakaria) located in four distinct agro-ecological zones of Satkhira district, Bangladesh. Thereafter, Akther et al. [37] reported a higher quantity of average biomass fuel (665 kg per household per month) consumption in the countrified region of the Meghna floodplain zones of Narsingdi district, Bangladesh while, Miah et al. [39] found the lower amount of biomass fuel consumption, including 66 kg per household per month at Chandanaish upazila of Chittagong district, Bangladesh. So, the consumption pattern of biomass fuel greatly varies according to region. However, the results showed that there was different level of consumption of biomass and other commercial fuels between the socio-economic groups. It was observed that the middle class households used more biomass fuels than poor and rich categories households. The per day consumption of biomass fuels in rich categories households found lowest due to highest level of using commercial energy, and it was found lowest in poor categories households because of saving fuels through less cooking items and per day less times cooking. The study showed that the households of high income groups used more electricity and LPG than households of low income groups. Hassan et al., [45] and Miah et al., [46] state that the rich households use more commercial fuels than that of poor households. Bhatt and Sachan and Rao and Reddy [47, 48] also stated that poor households cannot afford to them of using modern fuels as their per capita income is low.

Therefore, it was observed that, among biomass fuels, firewood was the most preferred and largest source. This trend of using firewood by households was also reported in previous studies in the context of rural Bangladesh [20, 36, 37, 39, 45, 46]. Cow dung was found as the next prominent biomass fuel, whereas its average consumption was 45.75 kg households−1 month−1. This is in agreement with the findings of Hassan et al. [20]. Thereafter, the other regularly used biomass fuels were leaves and twigs, shells and coir of coconut and crop residues in the study area. Such types of biomass fuel used in the study area have been corroborated by the findings of other studies [20, 36, 37, 39, 45, 47]. The monthly highest firewood consumption was found highest in medium type households compared to poor and rich types. The consumption of cow dung was found highest in medium type households. It was observed the substantial use of leaves and twigs was high in the poor categories households corresponding with Biswas and Lucas [49]. In our work, households with high literacy rates preferred spending more on LPG and candle compared to other biomass and non-biomass fuels corresponding with other studies by Rahut et al. and Miah et al. [39, 50].

4.2 Sources and end use of biomass fuels

Biomass fuels were mainly used for domestic cooking, whereas it was partly used for other purposes. The present study revealed that above 97% of biomass fuel was used for domestic cooking and 0.87% used for paddy parboiling, which is somewhat similar to the findings of 96.7% for cooking and 0.8% for boiling reported by Miah et al. [39]. Whereas, Baul et al. [51] found 92% of households use biomass for cooking, followed by rice parboiling and water heating. The findings showed that the main sources of biomass fuel were the own homestead and agricultural land. FAO [52] and Hassan et al. [20] stated that in the rural areas of Bangladesh, homestead forests meet more than 90% of firewood demand. Baul et al. [51] reported around 70% of households dependent on the homestead forest for biomass fuel supply was mainly. However, an excessive dependency on the homestead forest for biomass collection may cause a gradual depletion of resources and a scarcity of fuels soon. To prevent depletion, this requires less harvesting and sustainable forest management practices. Finding out alternative biomass fuel sources, such as woodlots (forest plantations) and markets can minimize over-dependency on homestead forests [51]. It was observed that the financial crisis of the households was the main reason for using biomass fuel. Furthermore, a reasonable price and local availability are the main reasons for the comprehensive use of biomass fuel in rural households. It has been reported that due to the poverty of the rural people, biomass fuel catalyzes the cost safety and most available sources of fuel for their cooking in Asia Pacific region [5], South Africa [53] and India [47], Nepal [54] and Bangladesh [45, 51].

4.3 Types of stoves used in households

The majority of rural households used inefficient cooking stoves in the study area. In the study's area, only 10% of households used improved cooking stoves, whereas 88.33% of households used traditional stoves. In Bangladesh, fewer than 20% of people have access to clean cooking [1]. As demonstrated in previous studies, using traditional cooking stoves results in higher emissions from incomplete combustion than using improved cooking stoves (e.g. [38, 55, 56]. Whereas, many studies [22, 57,58,59,60,61] reported that improved stoves can reduce large emission level. Improved stoves can save 27% fuels and 25% CO2 emissions compared to traditional cooking stoves (TCS) [51]. Whereas, Atikullah and Eusuf [62] reported that the improved stoves save 50–70% fuels compared with the traditional ones. Chagunda et al. [63] reported that improved stoves named Esperanza which can save 60% wood fuel under controlled conditions compared to the traditional stove. Improved cooking stoves have saved over 375.84 Bangladeshi Taka per stove per month, resulting in cumulative savings of over 600 million Bangladeshi Taka [64].

4.4 Bangladesh’s renewable energy policy and implementing projects

It is well understood that emissions from woody biomass fuel and agricultural waste burning are the major source of ambient carbon content [65] and are regarded as one of the major sources of atmospheric pollution [66]. The Government of Bangladesh (GoB) has taken a variety of actions to advance renewable energy technologies. According to the Renewable Energy Policy 2009, the target is to meet the demand for 5% of total electricity using renewable energy technologies by the year 2015, 10% by 2020 and 20% by 2035. This aims to boost the potential and dissemination of renewable energy sources and their technologies, such as biomass gasification and clean energy promotion while substituting non-renewable energy resources [67]. With the help of national and international funding, the government and private organizations are developing a number of biomass-related projects [68]. The state-owned non-banking financial institution Infrastructure Development Company Limited (IDCOL) is currently implementing two projects on biogas plant and one project on biomass gasification. Till February 2023, IDCOL has funded construction of over 65,800 biogas plants all over the country through its partner organizations. IDCOL is also implementing a project of biogas plants to generate electricity from poultry droppings. In the field of biomass gasification, IDCOL has started funding a project to produce electricity through the gasification of rice husks. [68]. In the field of biogas, the National Domestic Biogas and Manure Programme, for instance, has been supporting the installation of biogas technology in the rural areas of Bangladesh, where it is estimated that 80,000 small-scale systems that use animal waste are currently in operation [1]. Also many more national and international organizations are working, though the number is far less than required.

4.5 National forestry policy

Bangladesh National Forestry Policy, 2016 (Draft) has given high priority to fuel saving technologies and devices for the protection of forests. Under this policy, several tree planting programmes have been suggested, including the formulation and execution of extensive plantation programmes in suitable Unclassed State Forest (USF) land; the promotion of agro-forestry activities in all suitable and available land; the establishment of social/participatory forestry activities extended to the entire country; and strengthening plantation programmes on roadside, railway track side, embankment slopes that can promote sustainable consumption of biomass for fuel. Through appropriate programmes and projects, this forest policy attempts to stop deforestation and the degradation of forest resources, enrich and extend the areas under tree cover, and ensure that at least 20% of the country comes under tree cover by 2035, with at least a canopy density of 50% [69].

4.6 Challenges for policy implementation

There are several challenges exist to promote sustainable consumption of biomass fuel in Bangladesh. Bangladesh has a number of biogas facilities, but they are quite few in comparison to the country's overall population. In our study area, only two cow dung biogas plants were found. Whereas, no poultry droppings based biogas plants or biomass gasification plants were found. Moreover, low per capita land holding (one of the lowest in the world) is one of the major challenges for production of wood-based biomass fuels. This means that little land is available for the population to sustain their livelihood in regard to food, fuels and building materials. Conversion of woodland to non-forestry purposes is one of the major concerns for the sustainable supply of wood fuel in the country. Choudhury and Hossain [70] stated that a long-term governmental afforestation, reforestation, and forest enrichment programmes, a lack of coordination among governmental departments on land and forest management, weak institutional governance, lack of commitments on the implementation of forestry related policies and plans were identified as the main impediments to wood-based biomass development in Bangladesh. Residues from rice and other crops are recognized as promising for bioenergy production. However, due to technical, financial, institutional, policy and information barriers, crop residues-based biomass technologies have not yet reached the commercialization stage [71]. In addition to wood fuel and crop residues, animal dung has also traditionally been used as a fuel by most rural households and by many small-scale enterprises. Poor women and children are generally involved in the collection of animal dung, and in the processing and preparation of fuel cakes. They often collect animal dung from open areas, such as open agriculture fields and village roads. However, the availability of animal dung is increasingly limited due to the decrease in the number of cattle, decreased/increased farm sizes, restriction of open grazing facilities, conversion of wasteland to agricultural lands, and increased agricultural mechanization. A paucity of sustainable biomass-based energy strategies and policies, as well as their poor implementation due to minimal financial and human resources at both the regional and the national level could be limiting factors in the development of biomass-based energy in Bangladesh [39].

4.7 Possible solutions to overcome the challenges

One solution to this problem is to increase the efficiency of biomass fuel utilization and to take immediate action for wide spread use of improved stoves. Generally, Sustainable Development (SD) encompasses three fundamental approaches: economic, environmental and social, which are interrelated and complementary [72]. Economic sustainability aims (1) to maximize the flow of per capita income including a basic equity, and (2) to improve the living standards of the local population. Environmental sustainability aims (1) to maintain a sustainable yield and consumption of renewable resources, (2) to reduce environmental pollution, and (3) to prevent depletion of non-renewable resources. However, social sustainability refers (1) to the ability of a community which not only meet the needs of its current members but also support the ability of future generations to maintain a healthy community [73].

Non-renewable energy such as kerosene and liquid petroleum gas (LPG) release ten and 15 times more CO2 kg−1, respectively compared to wood [74]. Our results can be related to the renewable energy policy; as such, the biomass consumption of 192.53 kg could be alternatively used by the installation of biomass-based small-scale power plants and gasification systems at the village level to produce electricity and heat to fulfil the local energy demand. This clean energy use would result in fewer carbon emissions compared to the direct combustion of biomass, and simultaneously reduce the dependency on non-renewable fossil fuels through substitution. Due to the poor efficiency of cooking fuel conversion [75], biomass harvested from homestead forests was used excessively. Improved cooking stoves can substitute natural gas and LPG in households, minimizing a household's dependency on the homestead and public forests, thereby preventing overexploitation [38, 55, 76]. Before the widespread adoption of such technologies, therefore, policy support, research and design on the feasibility of biomass-based technologies, as well as accessibility to improved stoves at the village level, are crucial. The government of Bangladesh should extend invitations to local land users, research institutions, and international donor agencies/NGOs to work together with concerned government bodies on technological development and biomass-based energy to secure clean and equal energy access for everyone.

5 Research gaps

In our research, we did not investigate the use of improved cooking stoves or the feasibility of biomass-based technologies. Furthermore, this study's main drawback is that it only focuses on specific geographical areas. Conducting studies in specific regions has some inherent problems that may occur due to different biotic and abiotic variables that influence functional variables. At the same time, geographic [19, 65, 77], climatic [78], and seasonal variation [19, 79, 80] may affect the functional variables, e.g., biomass consumption. Another inquiry that would calculate consumption levels is suggested all year round for the entire country of Bangladesh considering different regions.

6 Conclusion

The study revealed with the consumption of biomass fuels as well as non-biomass fuels and their expenditure is influenced by different socio-economic factors like per capita income, housing types, per capita total land, per capita dwelling size and education status. Energy in rural households comprises biomass and commercial energy, whereas their consumption pattern mainly depends on expenditure issues. In the study area, majority of rural households used biomass rather than that of commercial energy. Likewise, illusive running costs, a lower economy, and locally available biomass cause the limited use of non-biomass energy in rural households. On the hand, several tree species such as A. saman, C. nucifera, M. indica, S. macrophylla, T. indica, A. auriculiformis, B. flabellifer, Z. mauritiana, A. procera and A. richardiana were also identified by the household as their preferred sources of biomass. Apart from that, cow dung is available in almost all parts of the village and the use of the biogas plant can be a possible solution in this situation in the study area. When both the enrichment of rural households' socio-economic conditions and the price of modern energy at a reasonable price are important, the majority of crop residues, including leaves, twigs, and cow dung, can be properly utilized for clean energy services. The findings of this study could be an important pathways not only in the study area but also other parts of the country as well across the globe. So, this study will help decision makers to take any decision regarding biomass consumption in the rural household condition and thus, may accelerate policy making process significantly.