Appraisal of Biogas Potential of Biogas from Animal Dung in Saeedabad, Pakistan

Pakistan is facing energy scarcity. The biogas is one of the renewable substitutes. It does not only overcome the energy scarcity but also harness the energy from animal dung which causes the CO 2 emissions. The present study was done on the appraisal of potential of biogas from the dung of animals (Buffaloes, Cows, Goats and Sheep) within the villages surrounded by Taluka Saeedabad. The purpose of the study was the energy potential of the biogas and the selection of the most suitable design and size of the biogas plant for the villagers. The present study also includes the domestic biogas plant economics. As per the estimation, total quantity of animal dung generated was about 129 tons/day, which can produce 3859 m of biogas per day. On the contrary, for cooking villagers require only 2748 m of biogas per day. Moreover, the surplus biogas of 1111 m per day can be used to produce electricity of 6666 kWh per day, which can fulfill the demand of about half of the population of villages under study. People are using firewood, cotton stalks, kerosene oil and LPG (Liquefied Petroleum Gas) for cooking. Converting animal dung into the biogas not only reduces the consumption of the traditional fuels used (Firewood, Cotton Stalks, Kerosene Oil and LPG), but also prevents about 900 thousand tons of CO 2 emissions into the environment. Additionally, a fixed dome biogas plant of 8-10 m size was recommended for each of the houses under study.

annually on energy source to meet its demands [1].
Pakistan is a 24 th international country in production of natural gas. Annually, it produces around 43000 million m 3 of natural gas [2]. From last decade, natural gas has been used in 3.7 million vehicles. On the basis of consumption of the natural gas in vehicles, Pakistanis ranked as 2 nd country in the world [3]. Pakistan has great The biogas is produced in an anaerobic digester without the presence of oxygen. It is obtained through three staged biochemical process, i.e. hydrolysis, acidification and methanogensis. An important element of biogas is methane, which is about 56-70%, followed by carbon dioxide of about 21-40%. Biogas also contains some traces of hydrogen, Sulfur dioxide, ammonia, nitrogen and water vapor [5][6]. According to Pakistan livestock census [7], phases [8]. The biogas is a serious solution of greenhouse gas emissions and reduces the carbon and methane gas emissions from cake of dung [4]. The data obtained from the questionnaire was analyzed by the weighted average method [12]. Moreover, Equation ( ) Where A is the number of animals in all villages, B is the number of Buffaloes in a house, C is the number of Cows Where TD is the total quantity of dung from all animals in Where PB is potential of Biogas in m 3 , and the constant digit is the specific biogas, which was obtained from the literature as one kg of dung produces biogas of 0.03 m 3 [13]. Then, an Equation (6) was designed through which biogas required is calculated each village.
Where BR is biogas required in m 3 , and the constant digit is the specific quantity of biogas required by a person/day. A specific quantity of biogas required by a person/day was obtained from literature as 0.26 m 3 [14]. Equation (7) was developed to calculate existing fuel used in the villages or sources of energy used for the cooking.
( ) Where FU is existing fuel used in villages, CF is Where FP is the price of fuel, PF is the price of firewood/ kg, PC is the price of cotton stalks/kg, PK is the price kerosene oil/liter and PLPG is the price of LPG/kg.

Population of Villagers
Total 650 houses were surveyed during the field study.
Approximately, 80% of houses of each village were visited and interviews were conducted. Population of different villages surrounded by Saeedabad is shown in   [15]. As compared to total animals in Pakistan, the quantity of animals in the selected villages is very low, but still significant in terms of domestic energy supply and environmental point of view.

Measurement of Animal Dung
The mass of animal dung (Buffalo, Cow, Goat and Sheep) was measured by using an electronic balance for samples of all four-animal species and collected for a week. Samples of animal dung were divided into two categories, i.e.
grazing and non-grazing. The Fig. 3 show weights of different animal dung, based on the grazing and nongrazing animals.
The quantity of the dung of the non-grazing animals was higher than to the grazing animals.  [19]. During the field survey, it was also observed that about 90% of animals were grazing and only 10% were non-grazing, thus for the research work the minimum quantity of the animal dung was encountered (i.e. for grazing animals).

Quantity of Animal Dung
Total quantity of dung of animals from buffaloes, cows, goats and sheep produced in all villages were in the order of 92.5, 32.4, 3.2 and 0.86 tons/day, respectively as shown in Fig. 4. The total quantity of dung of all four species in all the villages was 129 tons/day. Buffaloes have good quantity of dung, followed by cows, whereas the quantity of the dung from goat and sheep was considerably low.

Existing Uses of Animal Dung
The existing use of the animal dung is shown in Fig. 5.
From the field survey, it was observed that the villagers

Biogas Potential and Required for Cooking
The biogas potential from animal dung and biogas required for cooking were estimated for each village as shown in Fig. 6. As per the estimation from the quantity of the animal dung, it was observed that the large quantity of dung is produced from buffalos and cows, whereas only 3% is produced from the goats and sheep. Also, from the literature, it was observed that each kilogram of fresh animal dung produces about 0.03m 3 of biogas [13]. The Equation (5) was used to estimate the biogas potential available if the total quantity of the dung is utilized to convert it into the biogas. On the contrary, the quantity of the biogas required by each village was estimated through Equation (6), where it was considered that a person utilizes 0.26 m 3 of biogas in a day [14].

Appraisal of Potential of Biogas from Animal Dung in Saeedabad, Pakistan
Mehran

Energy Resources Used by the Villages for Cooking
From the field survey collected data, it was observed that the villagers were also using fire wood, cotton stalk, LPG and kerosene oil for cooking as shown in

Health and Environmental Benefits
The biogas is clean and eco-friendly fuel for cooking [24], while burning of firewood cause lungs and eye diseases in women and children. Additionally, the women spent hours out of home to collect firewood and face a lot of sexual violence problems in Darfur [25]. The biogas potential in the selected villages was estimated as 3859 m 3 /day, which can provide health and environmental benefits to the villagers, especially to the women. Moreover, the digested (bio-slurry), which is the byproduct of biogas production is a good organic fertilizer.
It increases fertility of soil and ultimately increase the crops production [26][27].
Moreover, the burning of firewood produced CO 2 emissions and causes deforestation, indoor air pollution and thus, pollute our environment. The total quantity of the dung consumed by the all selected villages is about 249 tons/month. As per the estimation, burning of one kg of wood produces about 1.65-1.80 kg of CO 2 [28]. By considering the lowest emission rate of 1.65 kg of CO 2 per kg of firewood burnt, and 249 tons of firewood consumption by the selected villages, the annual production of the CO 2 was estimated as 4930 tons.
Furthermore, one kg of fresh animal dung emits 0.01 kg of CH 4 [29]. The total amount of animal dung used as the organic fertilizer and dumped in the selected villages was estimated as 89 tons/day, which has the potential to produce 325 thousand tons of CH 4 per year. Considering the stoichiometric combustion of CH 4 with O 2 , one kg of CH 4 will produce 2.75 kg of CO 2 , thus the equivalent CO 2 produced from the animal dung used as the organic fertilizer and dumped in the selected villages will be 893 thousand tons per year. So as the cumulative, if the total quantity of the animal dung produced in the all selected villages is utilized to produce the biogas, then about 900 thousand tons of CO 2 emissions could be prevented to contaminate the environment through the global warming.

Most Suitable Size and Design of the Biogas Plant
The to Rs. 140,000/- [30]. From the field survey, it was observed that the human population in each house was ranging from 8-10 persons, thus the fixed dome biogas plant of 8-10 m 3 is the most suitable for the installation at each house.
The design of the fixed dome biogas plant is shown in Fig. 8 [31].

Economic Benefits
The economics of the biogas plant starts with the selection of the type of the biogas plant and its capital cost. The economics of the 10 m 3 fixed dome biogas plant in comparison to the existing use of the energy for cooking in the selected villages are summarized in

FIG. 8. DESIGN OF MOST SUITABLE SIZED FIXED DOME BIOGAS PLANT FOR THE VILLAGERS OF SAEEDABAD (ALL DIMENSIONS IN M) TABLE 1. ECONOMICS OF THE 10 M 3 FIXED DOME BIOGAS PLANT IN COMPARISON TO THE EXISTING USE OF THE ENERGY FOR COOKING
Furthermore, a centralized biogas plant can be installed for all the selected villages. The centralized plant will preferably the combine heat and power unit that will not generate the biogas for cooking and heating, but also generate the electricity.

CONCLUSION
The area under study was full of animal dung, and there cooking. The animal dung generated there will not only fulfill energy demand for cooking, but also improve the health of women, the quality of an environment, but also provides employment due to the construction and operation of biogas plants.