Resource and Environment

Charcoal Wastes-to-Fuel Energy Conversion for Circular Economy and Environmental Sustainability in the Global South: A Case of Wood Charcoal Industry in Tanzania

  • Norbert J. NGOWI , *
  • Institute of Development Studies, Mzumbe University, Mzumbe 83, Tanzania
* Norbert J. NGOWI, E-mail:

Received date: 2021-11-03

  Accepted date: 2022-09-30

  Online published: 2023-10-23


Low efficiency of earth kilns used in the carbonising process of wood to make charcoal has been reported as one of the sources of increasing charcoal wastes in the global south. However, the potential link and approaches of converting charcoal wastes-to-valuable energy and for the environmental health is not well known in Africa. Promoting local community capacity engagement in the production and reutilisation of recycled charcoal wastes at the households’ level is one of important measures to maintain environmental services for sustainability since households make decisions on the type of energy used. This paper, presents an approach of converting charcoal wastes to fuel energy for rural households and environmental health in Kilosa District, Tanzania. To achieve the objective of this research, the primary data were collected through interviews held with 298 randomly selected households, Focus Group Discussions and observations. IBM SPSS statistics version 20 Cross tab tools were used in the data analysis. Results revealed that the conversion of charcoal wastes-to-fuel energy approach used in this research demonstrates the ability of recyclable briquettes made from the locally available charcoal pollutants collected at different stages from earth kilns, to selling centers, improves tree harvest behaviour, adds another fuel energy source through reutilisation, and ultimate reduces pollution at the local level. Thus, the study provides a basis for policymakers to adopt charcoal wastes recycling strategies to address matters related to energy and ultimately enhances environmental health for sustainable development in Tanzania and beyond.

Cite this article

Norbert J. NGOWI . Charcoal Wastes-to-Fuel Energy Conversion for Circular Economy and Environmental Sustainability in the Global South: A Case of Wood Charcoal Industry in Tanzania[J]. Journal of Resources and Ecology, 2023 , 14(6) : 1148 -1155 . DOI: 10.5814/j.issn.1674-764x.2023.06.004

1 Introduction

Fuel from biomass supports more than 90% of the rural populations in the global south (Wassie and Adaramola, 2019). Specifically, in Tanzania, the same percentage of rural household uses firewood and charcoal to cook and heat their homes. Thus, charcoal production is considered the main cause of deforestation and pollution (URT, 1998; Kilahama, 2008). Several studies have investigated the use of domestic biogas plants, solar photovoltaic home systems, solar cookers, improved biomass cooking stoves, and use of modern charcoal kilns to reduce over dependence on forests and woodlands for biomass energy (Lewis and Pattanayak, 2012; Wassie and Adaramola, 2019, 2020). In many parts of Africa, wastes from charcoal (mainly small particles and wood scrap) produced during the carbonising process from wood to charcoal in the earth kilns or during packing, and transportation of charcoal to collection or selling centres in the warehouses, are left as pollutants or dumped in open areas thus increasing public health risks (Fig. 1).
Fig. 1 Wood charcoal wastes left in a kiln (a) and warehouse (b)
Fuel wood constitutes an imperative traditional source of energy in Tanzania. For that matter, biomass fuel cannot easily be replaced without affecting the Local Economic Development (LED). Partly because 45% of women are involved in wood biomass related activities such as harvesting of firewood. Given women covered 51% of the population (NBS, 2013), firewood collection activities have an impact on the education of girls, and on food security because of these women’s involvement in biomass energy industry (MNRT, 2015). Despite the significant impact of fuel from biomass, a few studies have been undertaken to show how wastes from wood charcoal can be converted to useful fuel energy for heating of homes and cooking by the rural population. Therefore, this paper, drawing data from Kilosa District, Tanzania, presents an approach of converting charcoal wastes to fuel energy for rural households and environmental health.

2 Study area and methods

2.1 Study area

Kilosa District spans between latitudes 5°55°S-7°53°S and longitudes 36°30°E-37°30°E. The district covers 14918 km2 of the land area (URT, 2012). While the district had a population of 438175 inhabitants (males 218378 and females 219797), selected villages for the study had 9992 people (male 4632 and female 5360) (NBS, 2013). Natural forests and woodlands cover 40% of the whole district. Natural forests cover 88879 ha, national forest reserves 66517 ha, district council forests 8168 ha, reserved villages 208732 ha, and 1692 ha which are under forest plantations (Ishengoma et al., 2016). The forest vegetation is characterised by miombo woodland mixed with shrub and grasslands.
The annual average rainfall varies with the altitude. The mountain areas receive up to 1600 mm, while the plains in the southern part of the district receive between 1000 mm and 1400 mm. The rainfall in the northern parts ranges between 800 mm and 1100 mm respectively (URT, 2012). The annual average temperature is 25 °C. The lowest temperature of 19 °C is experienced in July while the hottest 30°C in March. The district falls in the three agro-ecological zones. The first are mountains with an altitude of 2200 m. The strip runs along the part of the Eastern Arc ecosystem.
This area is characterised by pre-Cambrian metamorphic rocks. The area is suitable for wheat cultivation. The second area is characterised by upland plateaus, known as cultivation steppe featuring an altitude of about 1100 m. This zone is mainly plains with a few hills with clay and loamy soils. As the name depicts, the area is suitable for maize production and livestock keeping. The third zone comprises floodplains on the low altitude of 550 m irrigated by Wami and Ruaha rivers. Together with these rivers, water network in the district is entirely dominated with both seasonal as well as perennial rivers and wetlands. These water resources contribute to sustaining people’s livelihoods through agriculture, fishing, livestock keeping, and tourism.

2.2 Study design, data collection, and analysis

The research adopted a case study design using both primary and secondary data. The primary data were collected between November 2020 and March 2021. The study sought to understand the quantity of pollutants generated the approach of converting charcoal wastes and reuse, the method for disposal, and distance to the disposing site. A combination of the formula by Israel (1992) and the systematic random sampling techniques using regular interval of one household to another was used to get 298 respondents (Table 1). Secondary data on biomass fuel were collected first to get sufficient theoretical information regarding the problem under study. The selected respondents represented the district population sufficiently.
In this formula, n is the sample size, N is the number of households, and e is sampling error.
Table 1 Selection of sample size
Location/Village Population Number of
households (N)
Sample size (n)
Male Female
Ulaya Mbuyuni 1617 1640 581 119
Maguha 3015 3720 1417 179
Sum 4632 5360 1998 298
The criteria for selecting study villages included: villages with highest cover in land forest reserve area (VLFR), large quantity of charcoal (tons) harvested/sold in a year, and registered charcoal markets. These criteria were used to maximize variability of the information on charcoal wastes in the study area.
A structured questionnaire was set and administered to adult respondents who were 18 or above years old and at the same time household-heads. Each respondent was also interviewed. The interview was done simultaneously with a direct observation method. In this study, the sexes of the respondents were assigned different values, where “0” was assigned to male respondent and “1” to female respondent. In examining where charcoal wastes pollutants were disposed and the relative distance in meters from the households, data were collected from respondents and interpreted in the light of the researcher direct observation.
Data on the quantity of charcoal wastes generated from each sack of charcoal bought and used at home or given to a friend by charcoal maker were estimated using small tins to help the respondents in the quantification. The annual quantity of wastes generated was obtained by finding the average of the number of times a given volume of waste tin was produced per sack per household per year. Three levels of quantity produced were obtained:
(1) Small quantity: Between 0 and 50 kg in a year.
(2) Average quantity: Between 51 and 150 kg in a year.
(3) Large quantity: 151 kg and above in a year.
To capture data on where charcoal wastes were being disposed of and the distance covered, the study used a combination of different methods. The interview was followed by Focus Group Discussion (FGD), and personal observation through a transect walk. These enabled surveys in differentiating dumping sites/areas and estimating the distance covered. The IBM SPSS statistics version 20 cross-tabulation tools including the independent sample t-test were used to analyse the data collected using structured interviews. The statistical significance relation was assessed with a P-value of 0.05 as a cut off for statistical significance.

3 Results and discussion

3.1 Quantity of charcoal wastes generated

More than fifty percent of respondents reported that between 51 and 150 kg of charcoal wastes were annually generated by individual household. Small proportion of respondents generated 151 kg and above, and 50 kg and below (Fig. 2).
Fig. 2 Quantity of wood charcoal wastes generated per household per year
The study shows that the charcoal waste quantities produced depended on factors such as: tree species, season, type of kilns used, mode of transport and handling among others. The study shows that the amount of charcoal wastes produced reached roughly between 1 and 3 sacks of 50 kg. Low carbonisation efficiency of earth kiln used in the process of converting wood to make charcoal was mentioned as one of the main reasons leading to large quantity of wastes generated. Corresponding amount is documented in other parts of Africa (Ishengoma et al., 2016) including Madagascar and Rwanda. It is reported that in Madagascar and Rwanda, a low charcoal kiln efficiency of 8% to 36%, as one of the contributing factors to large quantity of wastes henceforth deforestation (Antal and Grønli, 2003). Although permits issued by District Council and the Tanzania Forest Services Agency (TFS) show that charcoal is sold in 50 kg sack, the study found that sacks weighed more than 90 kg for charcoal produced mainly from Brachystegia tree species. Kibati(① Names used to represent participants of the focus groups are not real names.), a charcoal maker from Ulaya Mbuyuni, explained:
During the dry season, charcoal wastes are produced in large quantities at the production points because of the failure to prevent aeration using the soil and grasses before lighting the kiln. During the dry season, the soil tends to be looser than during the wet season when water helps to hold the soil together and maintain a brick-like shape making it more effective in preventing aeration.”
The study enquired measures taken by the local community to reduce or prevent large quantity of charcoal wastes production. In this context, the paper probed focus group participants’ reactions to the waste reservation. During Focus Group Discussion meetings, Mr. Mchomba, another charcoal maker reported that:
Firstly, it is practically impossible to prevent pollution caused by charcoal wastes at the production point.”
When asked why he thinks so, he elaborated that:
Small pieces of charcoal are products from the tree barks removed in the process of charcoal making. If you wish to prevent the production of charcoal wastes, you need to make charcoal from trees that do not have barks. However, this is impossible. So to me, preventing pollution caused by production of charcoal wastes is practically impossible.”

3.2 Advantages of using wood charcoal wastes

3.2.1 Recyclable wood charcoal waste briquettes for fuel energy

The study found that less than half of the respondents were using charcoal wastes (Table 2). The findings show that households that discovered usefulness of charcoal wastes reused them.
Table 2 The use of wood charcoal wastes along gender
Sex Use of charcoal wastes df

No Yes Total count (Percent)
Male 105 (35.2%) 59 (19.8%) 164 (55%)


Female 64 (21.5%) 70 (23.5%) 134 (45%)
Total 169 (56.7%) 129 (43.3%) 298 (100%)

Note: ** is significant at 0.05 level of significance.

The small particles of charcoal wastes that could be collected from earth kilns, warehouses, and charcoal collection centres or markets were used to light charcoal cooking stoves. It was reported that the wastes produced low heat to vaporise water during rice cooking. This method is also reported in Thailand by Dunn et al. (1982) and in steaming banana in Uganda (Asada, 2019). In Uganda, ash and/or dust are frequently used to cool the fire down to give mashed banana its flavor.
Table 3 shows more than 64% of respondents considered charcoal wastes as useless pollutants—that they cannot be used and thus has no economic value. This study establishes that, small-size charcoal particle wastes that passed through grates within the charcoal cooking stoves were found to produce low heat henceforth not preferred by most of respondents.
Table 3 Household attitude on charcoal wastes and the environmental health
Attribute Response Count (Percent) df χ2 P-value Cramer’s V
Attitude on charcoal wastes Wastes are useless 192 (64.4%) 3 89.071 <0.001*** 0.547
Wastes are useful 46 (15.4%)
Wastes are partially useful 58 (19.5%)
Do not know 2 (0.7%)
Separation of charcoal wastes at source No 19 (6.4%) 1 11.953 0.001*** 0.200
Yes 279 (93.6%)
Access to charcoal wastes
No access 291 (97.7%) 2 4.285 0.117 0.120
Access to small quantity 5 (1.7%)
Sufficient access 2 (0.7%)
Availability of charcoal wastes for recyclables Not available 22 (7.4%) 3 22.114 <0.001*** 0.272
Available on average 99 (33.2%)
adequately available 172 (57.7%)
Do not know 5 (1.7%)
Regulations for charcoal wastes No regulations 254 (85.2%) 2 5.471 0.065 0.135
Present not enforced 20 (6.7%)
Enforced 24 (8.1%)

Note: *** is significant at 0.01 level of significance.

The findings indicate that a household which used an outdoor kitchen prefer using firewood during rainy season because they cook fast then go to farm. This attitudinal variation is also reported in other places (Tao et al., 2018). It is reported that majority of respondents claimed to have neither developed recyclable briquettes nor accessed any converted forms of the charcoal wastes as fuel energy source. To test the approach this paper presents a step-by- step innovative procedure of recycling wood charcoal waste to briquettes. The procedure is simple and that can easily be adopted by community for improving the local economy and environmental health of the study area. The steps are presented below and elaborated in Fig. 3.
Fig. 3 Key steps of converting wood charcoal wastes into briquettes (a) and (b), a display of recyclable briquettes (c), and enlightened recyclable briquettes burning in the charcoal stove (d)
Step one: Collect charcoal wastes, sieve them, and mix with clay soil. To maintain the mixture of powder and have good results, it is necessary to use the same mixture throughout the process.
Step two: Make the sticky stiff-porridge stuff, consisting of at least 1-2 kg of the mixture by soaking in a 0.5 L of water mixed with clay soil. The endpoint of mixing the stuff is marked by the sample turning stiff-porridge for at least 30 minutes.
Step three: The moulded sticky stuff produced during step two above, of different sizes depending on the size of charcoal grates in the cooking stove is poured into metal tube then pressed using hammer with metal pressers until fully compacted into a solid matter.
Step four: The solid matter is then ejected from the tube through holed piece of wood.
Step five: The solid matter is then sun-dried for an average of 3 to 4 days depending on the sun intensity.
Step six: The briquettes are now ready to be used as a source of fuel energy.

3.2.2 Treatment of wood charcoal wastes for environmental health

As indicated on Table 3, the majority of respondents were engaged in treatment and separation of charcoal wastes for environmental health. Table 4 provides various techniques of treating charcoal wastes. The methods included: feeding animals or mixing with soils, dumping in open areas accounted for the most common preferred disposal techniques (79.4%). Burning represented only a few (3.0%).
Table 4 Techniques for disposing wood charcoal waste pollutants
Technique Count (Percent)
Dump in open areas (farms and pit holes dug in home yards) 237 (79.4%)
Dump in containers supplied by District Council 29 (9.7%)
Feeding to animals and mixing with soils 23 (7.9%)
Burning 9 (3.0%)
Total 298 (100.0%)
Results show that, most of households disposed charcoal wastes within 10 m from the home yards. The paper finds it very close to the house and that both children and women could go out even during late hours and dispose of the pollutants without fear of dangerous animals. Disposing of pollutants took place once the storage container is full. This pattern is reported by other countries in Africa. For instance, Nweke (2017) reported that, a large quantity of wastes from wood charcoal was dumped off as wastes in many parts of Nigeria. The results show that the main two preferred techniques for reducing pollution caused by charcoal wastes in the area were throwing onto an open areas and pit holes dug near backyards. This was partly attributed by lack of clear regulations governing charcoal wastes management and a response to complex operating institutions and technological factors. Such factors explain why large quantity of charcoal wastes are less utilised and perhaps highlight the importance of increasing awareness on the use of charcoal wastes generated fuel energy among rural areas.
Regarding feeding animals charcoal wastes and on-farm mixing with soil, it was reported that giving small quantities of charcoal wastes to domesticated animals significantly contributed to animal health like pigs, cattle, and chickens. According to the findings, charcoal wastes enhance the levels of body toxin absorption hence improving poultry health status. According to Amprako et al. (2018) from experiments undertaken in Ghana, the use of charcoal wastes as additive feed increase the broiler chicken body weights due to stimulation of feed intake and reduction of negative environmental effect in pig farming by reducing faecal gas emissions. Also Odunsi et al. (2007) indicate that in Nigeria charcoal supplement feeds are used to reduce feed intake levels and induce egg production in poultry.
Results show that mixing charcoal wastes with soil im- proved soil physical and chemical properties. For instance, in Ulaya area, peasants explained that application of dust from charcoal was found to increase soil fertility. It was affirmed that soil mixed with charcoal increased maize production by 6 sacks; from 8 to 14 sacks of maize per hectare. Supporting the findings from this research, a research conducted in Ghana by Oguntunde et al. (2008) revealed that, saturated soils hydraulic conductivity obtained under the charcoal earth kilns increased significantly with decrease by 9% in the bulk density, and increased in porosity from around 46% to 51% compared to other soils adjacent to the charcoal kilns. While soils around kiln sites were found to have high infiltration rates, they had reduced overland flow and less erosion. Elsewhere, Nweke (2017) in South east Nigeria and Deenik et al. (2011) in Hawaii show that, increasing use of wood charcoal wastes on soils had improved the soil properties by increasing soil pH level by about 1.5 units compared with soils that have not been mixed with charcoal. The increase in pH had positive impact on soil-plant nutrients and eventually on crop yields. A study by Glaser et al. (2002) in Central Amazon, report that addition of charcoal to soil increased organic matter content and its fertility. In so doing, it enhanced seed germination, plant growth and, therefore crop produce.

3.3 Disadvantages for not using wood charcoal wastes

3.3.1 Effect on household expenditure

The study shows that money lost for not using charcoal wastes in the area ranged between Tanzanian Shillings (TShs)(② 1 USD=2200 TSh. This is the US Dollar to Tanzanian Shilling exchange rate for the year 2021.) 17000 per bucket and 28000 Shillings per sack. However, the price varies across the volumes of charcoal per sack and the tree species used. In average, it was reported that per each household a sack of charcoal lasts in a month but this varies according to the household size and the season. More charcoal is used during rainy seasons due to difficulty in searching for firewood in the forests and due to shortage of outdoor kitchen. Therefore, the loss of charcoal through wastes can be estimated at USD 77-128 per household per annum. The estimates based on fuel energy bought by a sack in a 10 months maximum. If utilised successfully, the families could save the household incomes spent on energy as well as time spent on firewood collection. In so doing, it will reduce poverty through household energy budget expenditure.

3.3.2 Effect of unused wastes on environment and public health

The study found that unused charcoal wastes could increase the atmospheric temperatures on sun-exposed wastes and water pollution when washed down stream (Fig. 4). These results are supported by participants of focus group discussion who linked the harmful negative effects of increased wood charcoal wastes on the human health in the area. Mr. Mayelle, one of the participants said:
Fig. 4 Openly disposed wastes charcoal (a) and plastic bag wastes (b) in the study sites
Charcoal wastes increases human health risks. When one breathes in dust from charcoal wastes, it can impair the proper lung functioning. In addition, working in the charcoal industry makes someones skin rough and dry, leading to skin-related diseases.”
Lack of thorough knowledge on how to convert wood charcoal wastes to briquettes was mentioned as the main limiting factor of using charcoal wastes. For instance, Benili one of participants reported that:
People with skills of converting wood charcoal wastes to fuel energy briquettes are found in urban centres and not at charcoal production sites. Majority of charcoal production areas are found in rural areas.”

3.4 Impact

This paper shows the impact of the perception of local people on the approach of re-using the high quantity of generated charcoal wastes for energy, public health, and the environment.
One, it was reported that, recyclable charcoal waste briquettes produced enough heat for cooking. Thus, using charcoal wastes can be an alternative energy source. Two,charcoal wastes are said to be good fertilisers. Ms. Pauline asserted that:
Pumpkin and vines do very well in areas rich in charcoal wastes.
This argument was further supported by Mchomba, a charcoal maker, who witnessed that:
Wherever there was a remaining of wastes in the charcoal kilns, pumpkin and potatoes, vines and other traditional spinach germinated and flourished very well as if somebody had planted them.
Three, mixing of a little amount of charcoal wastes to animal feed reduces mortality rates of pigs, increases egg laying capacity for hens (poultry) and milk production in cattle.
The paper presented various possibilities of reducing pollution caused by charcoal wastes and therefore environmental health. The main precaution was through proper handling of the charcoal making and transportation processes. Contributing to this, participants of the focused group discussion enumerated various strategies that can be employed to reduce pollution from quantity of charcoal wastes generated. The strategies include:
(1) Proper handling of the charcoal sacks during loading and unloading the vehicle. Each trader must strictly supervise assistants who are loading and unloading charcoal.
(2) During dry season, one has to ensure that the vehicle (truck) packs at a nearest point to the charcoal kiln. This will reduce the loss during loading and unloading.
(3) Never use a motorcycle for carrying charcoal. A motorcycle is so destructive and leads to massive charcoal wastes production because the sacks are tied up very tightly which is not good. Again, the speed and the paths taken by the motorcyclists make the situation worse.

4 Conclusions

This paper demonstrated positive results of an approach of re-using charcoal wastes for household fuel energy and public health. However, before rolling out the approach to the industry, more experiments on dust-soil-water ratio for producing briquettes, quantity of heat generated from burning recyclable briquettes, and procedures for extinguishing burning recyclable briquettes are recommended. This would validate the approach to allow more households and charcoal makers to recover charcoal pollutants from the environment thus increasing energy security and reducing human health risk caused by charcoal wastes in the global south.


This research was funded by VLIR-UOS/4SiTe programme of Mzumbe University.
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