The purpose of this study was to carry out controlled cooking tests so as to evaluate the amount of Carbon Monoxide (CO), Carbon Dioxide (CO2) and Particulate Matter (PM2.5), the main causes of indoor air pollution released from incomplete combustion of cooking fuels used by the sampled households. The study was carried out in Kibera Constituency, Nairobi, Kenya. The study found that measuring these emission and highest temperature (°C) reached in the house while cooking was quite important in understanding the extent of indoor air pollution among targeted households. The study further sought to analyze the amount and efficiency of fuel used when cooking a standard meal of breakfast and dinner in a typical household. The fuels evaluated in this study were Charcoal, Kerosene, Electricity and Liquefied Petroleum Gas. Four households were randomly selected from a sample size of 304 households to participate in the Controlled Cooking Tests. Participation in the study was voluntary. Participating household who signed consent forms containing information about the study, the procedure and the benefits of participating in the study was quite symmetrical but participants willingly.
Charcoal; Controlled cooking tests; Household; Kibera; Indoor air pollution
Background of the Study
Provision of clean‚ affordable, safe and sustainable energy is important in poverty reduction‚ wellbeing of people and sustainable development. Many people worldwide have no access to most basic energy services . Clean energy refers to energy types that create less or no pollution to the environment. There is no perfect environmentally friendly energy. Wind energy production for example may cause visual and noise pollution . Hence this study applies the term cleaner cooking energy as opposed to clean which is in line with the Sustainable energy for all guidelines initiated by Ban Ki-Moon in 2011 . As the Secretary-General of the United Nations, he emphasized that, “energy is the golden thread that connects economic growth, increased social equity, and an environment that allows the world to thrive.” Access to energy is a necessary precondition to achieving many development goals that extend far beyond the energy sector in eradicating poverty, increasing food production, providing clean water, improving public health, enhancing education, creating economic opportunity, and empowering women. Hence cleaner energy is needed to prevent climate change‚ reduce premature deaths and economic burden and provide energy security . IEA and OECD (2004) report indicated that worldwide, 2.4 billion people continue to depend on biomass fuels like wood, dung and agricultural residues to be able to meet their basic energy needs for cooking, boiling water, and lighting and, depending on climatic conditions, space-heating.
Rehfuessetal.  noted that, from an environmental point of view, wide- spread use of solid fuels could mistakenly be interpreted as a positive development, given that most biomass fuels constitute a source of renewable energy. From a public health point of view, widespread use of solid fuels is, of course, interpreted as a negative development because of the health risks associated with indoor air pollution. The study further noted that, solid fuel use is a poor proxy for indoor air pollution levels as the concentrations of small particles, CO, and other pollutants vary markedly between different types of solid fuels and between the same fuels being burnt in open fire versus in a well-maintained improved stove. In light of population growth and given the current lack of political commitment, it seems unlikely that the coming decade will witness a large reduction in solid fuel use in most of the developing world. Owusu andAsumadu  stated that,renewable energy sources replenish themselves naturally without being depleted in the earth; they include bioenergy, hydropower, geothermal energy, solar energy, wind energy and ocean (tide and wave) energy.
Zheng et al.  in a study in four neighborhoods in Accra, the capital of Ghana found that household and community biomass fuel use were important predictors of household PM pollution in Accra neighborhoods. The study further noted that, community biomass use had a stronger effect on cooking area Particulate (PM) than a household's own fuel in crude and adjusted estimates. At the household level, fuel use for both own and small-commercial cooking seemed to be associated with PM pollution. We also considered associations by PM size fraction and found that cooking area PM2.5 concentrations consistently exceeded corresponding ambient levels, suggesting the presence of household sources for coarse particles, such as sweeping and resuspension; the pattern for ambient and household PM2.5 was more mixed, According to Energy Technology Perspectives .
‘Climate scientists agree that there is a strong and incontrovertible link between global GHG emissions caused by human activity, their concentration in the atmosphere and average global air and sea temperatures. The global average annual concentration in the atmosphere of CO2– the most important anthropogenic greenhouse gas – reached 410 parts per million (ppm) in 2019, up 3 ppm (0.6%) on the previous year. This is a major increase from pre-industrial levels, which ranged between 180 and 280 ppm. These higher concentrations are responsible for increasing the global average temperature of the planet by about 1 degree Celsius, leading to an increase in global sea levels of about 20 centimeters, the melting of glaciers and reduced sea ice, along with broader changes in weather patterns. Increased CO2 levels in the atmosphere dissolve into the upper ocean waters and are also causing the world’s oceans to become more acidic’.
In most households in Africa south of Sahara, 700 million depend on biomass for cooking energy. Whereas biomass use is on the decline in other parts of the world‚ its use in SSA is increasing. Biomass energy production requires a lot of labor and employs many people. Charcoal contributes around Ks.35 billion to the economy and the industry employs 200,000 people . Charcoal is preferred because it is relatively clean compared to firewood‚ charcoal produces less smoke in terms of fine particulate matter though with higher concentration of carbon monoxide compared to firewood and is readily available . It is estimated that 900 million people will use biomass as cooking energy by 2020. Access to clean energy services remains limited . This may be due to many factors which could be affordability of cooking fuel‚ convenience of cooking fuel .
The current trends in biomass cooking energy production and use are unsustainable and inefficient. Charcoal production process involves burning wood in traditional earth kilns which are inefficient and efficiency range of 10-20%‚ 9% of charcoal produced in Kenya is done by this method which wastes wood and emits large volumes of greenhouse gases. The use of traditional kiln produces 0.77- 1.63 kg of carbon dioxide per kg of charcoal . Environmental impacts include depletion of forests and climate change. Firewood is mainly used by rural households in Kenya who collect it from ‚ public or private farms, branches of pruned tress and dead fallen tree parts. Firewood may also be collected from gazette forest where there is danger of cutting young trees illegally preventing regeneration thereby reducing forest cover. Firewood collection can interfere with fragile ecosystems. The imbalance between firewood supply and demand was 57.2% in 2002 and was expected to rise to 63.4% by 2015 . In firewood collection women travel long distances, spend a lot of time and risks their lives to attacks by human or wild animals and injuries of head, back and legs.
About 82% of urban households in Kenya and 34% of rural households use charcoal [14,15] an inefficient biomass energy which has many negative impacts such as fuel wastage and indoor air pollution. For instance, 600,000 people die every year as a result of smoke inhalation and economic costs are considered in relation to the best case scenario of full adoption of higher performing biomass stoves by households and it is as high as US $36.9 billion per year . There is need to adopt cleaner cooking energy which is more efficient and sustainable.
Alternative sources of cooking energy are available and their implication on livelihoods and environment needs to be understood as well as strategies for enhanced adoption and scaling up. These alternative sources of cooking energy include the following and their average national proportional use; Biogas (0.7%), electricity.0.8%‚ LPG 5.1% Kerosene 11% .
The aim of this study was to investigate indoor air pollution as a result of cooking fuel (Charcoal, LPG‚ Kerosene and Electricity) under actual conditions prevailing in the kitchens in the selected households. Participatory research method was used with four households volunteering to participate in cooking using charcoal ‚ LPG‚ kerosene and electricity. Time taken to light the stove‚ time taken to cook‚ amount of fuel used were recorded. Changes in concentrations of Carbo dioxide‚ carbon monoxide and PM2.5 were recorded. Temperature was also recorded.
The study was carried out in Kibera (Laini Saba village) an informal settlement in Nairobi with a population of 170170 people according to the 2009 Kenya Population and Housing Census Report.
Four households were randomly selected from a sample size of 304 households to participate in the Controlled Cooking Tests. Participation in the study was voluntary. Participating householdssigned consent forms containing information about the study, the procedure and the benefits of participating in the study.
Out of the 4 households selected, 3 households typically used Charcoal, Kerosene or Electricity as cooking fuels at different times of the day while thefourth householdwas selected to join the three household and cook with Liquefied Petroleum Gas (LPG).
Cooking Process Procedure
Eight controlled cooking tests were carried out to cook breakfast and dinner using thefour different fuel types. A total of 32 tests were carried out by the end of this study.
The cooking tests were done between6am-9am for breakfast and 3pm-6pm for supper.Before the cooking begun, ingredients for the meals were sourced from a local shop and weighed using an electric scale.
For breakfast 2000g water, 1000gmilk, 20g tealeavesand 80g sugars were weighed. After weighing, the ingredients were all mixed in a medium sized pot.
The ingredients for dinner, which consisted of two dishes,were 2000g Water, 1000g Maize flour for cooking the first meal and kale, tomatoes,onions, salt and oil all precisely weighed to a total weight of 1100g for the second meal.
Charcoal was weighed in a separate container and put in the stove. When cooking with kerosene, the fuel was poured into the kerosene stove and the weight taken. The whole cylinder was weighed when LPG was used. After weighing the stove was lit with the time taken for it to be fully lit recorded. Cooking began when the stove was fully lit and ended when the meal was fully cooked depending on the household cooking style.
After removing the food from the charcoal stove remaining fuel was placed in a separate container and weighed so as to ascertain the amount of the fuel used in the cooking session. For kerosene the stove with the fuel were weighed to get the weight remaining fuel. When cooking with LPG, the whole cylinder was weighed again to determine the amount of fuel used.
The dimensions of the houses with all the ventilations were measuredat the beginning of the study.The equipment wasplaced at least 1.5m away from any ventilation in the house.
The equipment was hanged 1m away from the stove and 1.5m high in the house using a wire. The distance from the stove emulated the distance from which a person operating the stove sits and the height simulated a person standing in the house.
Carbon Monoxide (CO) data was measured at an interval of 10seconds using EL-USB-CO Carbon Monoxide data logger.
Carbon Dioxide and Temperature data were logged at an interval of 1 minute using HOBO Telaire 7001 TEMP/RH/CO2 data logger combined with the HOBO U12 to record and download the data.
Particulate Matter was also measured at an interval of 1 minute using the University of California, Berkeley Particulate Matter Monitor (UCB-PM Monitor).
The process of measuring the concentration of CO, CO2, Particulate Matter and Temperature changeswhile cooking,begun an hour before lighting of the stove. The equipment waslaunched and set to zero (warm up) for 30 minutes inside zip lock bags. Afterwards the equipment was hanged and left for 30 minutes to monitor ambient CO, CO2, Particulate Matter and Temperature data inside the room where the cooking test took place. After monitoring ambient air data for 30 minutes the stove was brought in the room and cooking started.
After the whole cooking was done, the equipment was again left for another 30 minutes to capture the background air data so as to evaluate the process of returning back to the ambient conditions before any cooking in the room. Data was then downloaded after the final ambient air data logging.
Emission Data Analysis
Raw CO, CO2, Particulate Matter (PM2.5) and Temperature (Ë?C) data captured during the whole indoor air concentration monitoring was analyzed using the MS Excel Descriptive Statistics Function to determine Mean, Median, Mode and Standard Error.
Combustion properties of cooking fuels used in Kbera informal settlements
Charcoal used for cooking was analyzed by KEFRI (Kenya Forestry Research Institute) and the following results (Table 1) were obtained.
|M.C(%)-Moisture Content||V.M(%)-Volatile matter||F.C(%)-Fixed Carbon||A.C(%)-Ash Content||C.V (k.cal/g)–Calorific Value|
Table 1: Combustion test on charcoal sample.
Combustion test for sample of charcoal was done by Kenya Forestry Research Institute (KEFRI) using the standard procedure to analyses combustion properties of charcoal sample used in cooking tests by households in Kibera. Bomb calorimeter was used to determine the calorific value of charcoal sample. Moisture content was determined by heating a sample of charcoal to 103°C in an oven for duration of 12 hours and expressed as % decrease of weight of initial sample of charcoal. Volatile matter was determined by incinerating the dried charcoal sample in a muffle furnace at atemperature of 900°C for 7 minutes and taking weights. Fixed carbon is the combustible portion that is left as a residue after volatile matter has distilled off. Fixed carbon is determined by subtracting the sum of moisture and ash content from the original sample (Tables 2 and 3).
|Viscosity||Density||Solubility||Flashpoint||Heat of combustion|
|Low viscosity||0.78-0.81gm/cm³||Insoluble in water||37-65°C (100& 150° F)||43.1/mJ/kg|
Table 2: Combustion properties Kerosene.
|Flash point||Melting point/Boiling poit||Highest temperature when burned||Calorific value (MJ/kg|
Table 3: Combustion properties of Kerosene.
LPG has good combustion properties compared to Charcoal and kerosene. It has higher calorific value‚hot flame and leaves no unburnt residue (Table 4).
|Household||Length (cm)||Width (cm)||Height (cm)||Distance between partion and roof (cm)||Size of door (The only opening)||Window size|
|Household 1||355||240||355||40||70 cm by 160 cm||0|
|Household 2||386||375||235||50||69 by 171 cm||0|
|Household3||350||344||305||42||74 by 172 cm||49 cm by 43 cm|
Table 4: Kitchen characteristics.
The dimensions of the kitchens in Kibera were measured and recorded in the table above. There was no partition between the kitchen and the living room. The bedroom and the living room were separated with a piece of cloth. Emissions from the kitchen could circulate in the whole house since the rooms were not fully partition. A plastic sheet separated the roof and the rooms in all households sampled for cooking test.
Bar graph shows time taken to light and cook breakfast using the four types of cooking energies (Kerosene‚LPG ‚Charcoal and Electricity). LPG took the shortest time to cook followed by Charcoal Electricity and kerosene respectively. Concerning time taken to light ‚ LPG was instant followed by Kerosene Electricity and lastly Electricity. For electricity‚ the time taken to light was the duration from switching the coil on to when it turns red hot (Figure 1).
Figure 1: Time taken to light stove and cook breakfast.
Bar graph showing the quantities of different fuel types used to cook the same amount of breakfast and dinner.A comparison revealed that kerosene took the smallest quantity to cook dinner followed by LPG and lastly Charcoal. Electricity could not be compared with other cooking energies because households had direct connections to the mains with no meters (Figure 2).
Figure 2: Time taken to light stove and cook dinner.
A comparison of amounts of fuel used to cook breakfast revealed a tie between LPG and Kerosene which took the smallest quantity followed by Charcoal which took more than three times the amount of Kerosene or LPG used.
Bar graph showing the amounts of CO release when cooking a standard breakfast meal with the four different types of fuel (Kerosene‚ LPG ‚Charcoal and Electricity). Cooking with Charcoal results in more emission of CO followed by kerosene‚ Charcoal and electricity respectively (Figure 3).
Figure 3: CO emission before‚ during and after cooking breakfast using different types of fuel.
Bar graph showing the amounts of CO release when cooking a standard dinner meal with the four different types of fuel (Kerosene‚ LPG ‚Charcoal and Electricity). Cooking Charcoal results in more emission of CO followed by kerosene‚ Charcoal and electricity respectively (Figure 4).
Figure 4: Bar graph showing CO Emissions before‚ during and after cooking dinner.
Bar graph showing the amounts of CO2 release when cooking a standard breakfast meal with the four different types of fuel (Kerosene‚ LPG ‚Charcoal and Electricity). Cooking with Charcoal results in more emission of CO2 followed by kerosene‚ Charcoal and electricity respectively (Figure 5).
Figure 5: Bar graph showing the amounts of CO2 released before‚ during and after cooking breakfast.
Bar graph showing the amounts of CO2 release when cooking a standard breakfast meal with the four different types of fuel (Kerosene‚ LPG ‚Charcoal and Electricity). Cooking with Charcoal results in more emission of CO2 followed by kerosene‚ Charcoal and electricity respectively (Figure 6).
Figure 6: Bar graph shows CO2 Emissions before during and after preparation of dinner.
Bar graph showing the amounts of PM2.5 release when cooking a standard breakfast meal with the four different types of fuel (Kerosene‚LPG‚Charcoal and Electricity). Cooking with Charcoal results in more emission of PM2.5) followed by kerosene‚ electricity and Charcoal respectively (Figure 7).
Figure 7: Bar graph showing particulate matter (PM2.5) concentrations, before‚ during and after cooking breakfast.
Bar graph showing the amounts of PM2.5 release when cooking a standard dinner meal with the four different types of fuel (Kerosene‚LPG‚Charcoal and Electricity). Cooking with Charcoal results in more emission of PM2.5) followed by kerosene‚ electricity and charcoal respectively (Figure 8).
Figure 8: Bar graph showing particulate matter (PM2.5) concentrations, before‚ during and after cooking dinner.
Times taken to cook using different types of cooking energy
Time taken to cook a meal was determined by including the time taken to light cooking stove, time taken to prepare and cook all dishes. LPG was found take the shortest time to cook dinner and breakfast (19.20 minutes and 32 minutes respectively), followed by Charcoal (26 minutes, 50 minutes for breakfast and dinner respectively), Kerosene took the third shortest time (40 minutes for breakfast and 51 for dinner) followed by electricity which was last (37minutes for breakfast and 1 hour five minutes for dinner).
Anova results to compare the cooking times found that there is a significant (p<0.05) difference in cooking times.
Cooking with LPG reduced the cooking time by almost half compared to electricity. LPG reduced the cooking time of dinner by 1.56 times compared to charcoal. This makes LPG good for cooking during hours when people are time constrained. Cooking with charcoal increased cooking time because of the long time taken to light it.
Charcoal took the largest amount of fuel to cook food followed by LPG and Kerosene took the least. Electricity could not be compared because all houses using electricity had no meters.
Cooking with LPG and Kerosene reduced the amount of fuel used to cook. LPG was found to reduce the amount of energy by 2.9 times compared to charcoal. Kerosene reduced the quantity of cooking energy four times compared to charcoal.
An Anova test was done to investigate if there is significant difference in quantity of fuel used. Anova test found out P < 0.05 which confirms that there is a significant difference in the quantity of fuel used.
Cooking with LPG or Kerosene can reduce thequantity of charcoal consumed.Switching to LPG or fuel stalking if practiced by households can help reduce the demand for charcoal and this can reduce deforestation.
Emmissions from different cooking fuels
Electricity had the least emission compared to other cooking fuels followed LPG then Kerosene and charcoal had the highest.
Anova test was done to test if there is a significant difference in emmission between different types of cooking fuels. An ANOVA test revealed p<0.05 which comfirms a significant difference in emmission between the different types of coooking energy.
Households cooking with LPG reduced emmission of CO by 6 times compared to charcoal. Cooking with Kerosene reduced CO Emmission by 3 times.
Shifting from cooking with charcoal a traditional cooking energy by majority of people in Kenya to LPG or Kerosene can help reduce health impacts as a result of CO and reduce many premature deaths.
Electricity had the least emission of CO2 followed by LPG then Kerosene and charcoal had the highest emission of CO2.
Household’s cooking breakfast with charcoal released 1.7 times more CO2 thanthose cooking with LPG and 1.2 times with Kerosene.
Using charcoal as a cooking fuel release more CO2 a greenhouse gas than other sources of cooking energy.
A shift from charcoal to LPG may reduce greenhouse gas emission by a great margin
Particulate matter PM2.5.
Electricity had the lowest emission of PM2.5 followed by LPG then Kerosene and charcoal had the highest emissions of PM2.5compared to other cooking fuels. Kerosene had 1.23 time’s higher emissions of PM2.5than charcoal and 1.6 more than LPG.
Cooking with charcoal exposes the households especially the women to nearly three times the level of particulate matter than those cooking with LPG and 1.6times more than those cooking with kerosene.
The use of cleaner energy fuels such Biogas, electricity, LPG is still low in low income countries especially in slum areas. The implication of this on health and environment is quite severe and need to be addressed. This is quite dangerous as more household in the designated places are getting exposed to indoor pollution as a result of cooking fuel. Kerosene which is the most common cooking energy comes from fossils petroleum fuels that produces gaseous pollutants and particulate matter. Charcoal, a common cooking fuel in Kibera slums and many other low income households, come from carbonizing wood and this may lead to deforestation which also has its own consequences. Charcoal making is done in kilns that are highly inefficient leading to wanton destruction of forests. Charcoal cooking also produces harmful carbon monoxide and carbon dioxide gas. Researches indicate that inhaled carbon monoxide competes with oxygen to bind to hemoglobin, resulting in oxygen deprivation to the organs, which can lead to death. The current trends in cooking energy use in Kibera not sustainable and there is need for energy shift to cleaner sources of cooking energy.
Citation: Oluoch DO, Nyamasyo G (2020) Indoor Air Pollution from Cooking and its Effects on Households in Low Income Urban Areas in Developing Countries. J Pollut EffCont 8:260. doi: 10.35248/2375-43126.96.36.1990.
Received Date: Oct 23, 2020 / Accepted Date: Nov 20, 2020 / Published Date: Nov 27, 2020
Copyright: © 2020 Oluoch DO. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.