The objectives of this study were to enhance the production of biogas through using a mixture of cow and chicken manure and to investigate the effect of digested manure on plant growth. Biogas digester consisted of a plastic polyethylene tank with a volume of 0.25 cubic meters. Cow and chicken manures were collected from certified animal and chicken farms. Mixture of manure was prepared by mixing 5 kg of chicken manure and 5 kg of cow manure together in 100 L plastic tank containing 90 L water free from chlorine. Percentage of manure in all cases was 10% (w/v). The manures were transferred to the digesters and kept in greenhouse to insure warm conditions (30 °C - 39 °C). Produced biogas was measured each two days and digestate samples were taken every two days for pH, EC, BOD, COD determination. Results showed increased biogas production and reached the highest quantity after 28 days and the amount of biogas produced from the mixture of cow and chicken manures was higher than the amount produced from each manure individually. Decreases in pH values were observed during biogas production followed by BOD, COD reduction. On the other hand, increases on EC values were observed. Application of digested manure in agriculture increased yield of lettuce by 75% comparing with the control sample. The study recommended using cow manure mixed with chicken manure to increase the production of biogas and to use the digested manure in agricultural.
Rapid growth of population and development in industrial activities require large quantities of energy, and on the other hand, generate large quantities of waste that should adequately be disposed without risks to human life and ecosystems [
The limitation of the abovementioned reports is that they focused on evaluating the biogas from one type of manure. They did not evaluate mixtures of manure in biogas production. Furthermore, they did not make biogas purification or using the digested manure as a fertilizer. Furthermore, quantification of biogas production remains poorly investigated. The authors of this study focused their efforts on evaluating the effects of mixing manure on the quantity of biogas production and further provided a chemical technique for biogas production and investigated the digested materials as fertilizers.
The fresh cow manure and poultry manures were collected from certified cow and poultry farms in Gaza Strip. About 100 kg slurry in a ratio of 1:9 of manure and water each were taken and mixed well to form a homogenous mixture as shown below: treatment 1 contains 10% cow manure + 90% water; treatment 2, contains 10% poultry manure + 90% water and treatment 3 contains 5% cow manure + 5% poultry manure + 90% water. These three mixtures were transferred into three plastic polyethylene tank of 250 L capacity each.
A basic biogas digester consists of a plastic polyethylene tank of 250 L capacity each, purchased from a local market. The biogas design is shown in
A homogenized manure prepared according to the above mentioned ration was added to digester through an inlet and be removed after complete digestion from the outlet in the bottom of digester. The digester was 95% filled with manure homogenate. The oxygen in the 5% air was consumed by burning a small was on a plastic plate under closed condition.
The wax will be turned off immediately after complete consumption of oxygen occurred.
Temperature of digester was measured by using pie inserted in digester. The upper cover of digester is attached with a plastic tube to collect the produced biogas into a big elastic bag.
The collected biogas was allowed to pass into three containers for complete purification. The 1st container contained ferric oxide that reacts with hydrogen sulfide. The 2nd container contained calcium hydroxide the react with CO2 to form CaCO3. The 3rd container contained Boric acid that react with NH3 or NH4OH (
Samples of the manures were taken before starting biogas production and after 28 days of retention time from each plastic tank. Then samples were taken each two days for determination of acidity (pH), electric conductivity (EC), total solid (TS), chemical oxygen demand (COD), biological oxygen demand (BOD), phosphates (PO4), sulfate (SO4) and cations. The total kegldahl nitrogen (TKN) and total organic carbon (TOC) were determined in the initial and final digestion as previously reported [
The produced biogas was collected in a rubber bag pre-weighted before installation with the biogas production system, after complete filling of the rubber bag with biogas it was weighted again. The difference between the initial and final weights indicates the weight of the produced biogas. These steps were repeated each to days to weight the amount of produced biogas.
Following the procedures previously described [
At the end of biogas production, three L samples were collected from the outlet of the system (
Lettuce seedlings were sown in plastic pots 10 L containing 9 kg sand soil collected from an agricultural area has a free history of using organic or mineral fertilizers. The experimental design includes three treatments as follows: control sample includes lettuce seedling sown in 5 plastic pots and receiving only fresh water, treatment 1 includes lettuce seedlings sown in 5 plastic pots and receiving fresh manure (before biogas production), treatment 3 includes lettuce seedling sown in plastic pots receiving digested manure. The quantity of manure tested corresponded to the rate of 1 kg/m2 of soil according to the recommendation of ministry of agriculture [
Based on previous published work [
% Growth = 100 × (Lt − Lc)/Lt (1)
where, Lt and Lc are the plant length/weight (cm/g) in the treatment and the control sample. Then %GI values were regressed with the tested.
Average and standard deviation were calculated to each treatment. t-test was used to detect differences among treatment at p-value = 0.05 low value of standard deviation indicates homogenization and accuracy of the work. We included error bars in the figures where applicable. An overlapping of error bars indicates no significant differences. We also added letters in tables to indicate similarity of results.
The biodigesters are plastic tanks made of polyethylene to avoid broken down due to movements. They are usually back or blue to absorb heat energy during the operation process to accelerate biogas production.
Immediately after mixing the manure as mentioned above, it was transferred to the biodigesters for incubation in the greenhouse at a temperature ranged from 25˚C - 30˚C for 3 - 7 days to start working. The volume of the plastic tube for biogas collection was taken as an indicator of system operation. As the volume increased rapidly as the operation process went smoothly.
The process included passing the produced biogas along with the impurities to the purification system which consisted of three units connected directly to gather as seen in
Sampling of Digestate was performed each two days to understand the effect of time on the biogas production.
The collected gas during 28 days in two days’ period is presented in
can be seen that mixture of manure produced higher quantity of biogas than cow or poultry manure. This indicates that mixing manure would be an optimal choice for biogas production.
Daily measurements of pH values of the manure during the gas production period are shown in
It can be seen that all pH ranges declined to a more acidic value during the biogas production regardless to the alkalinity range.
The values of TS of the manures are presented in
Measured values of EC in manure are presented in
The insoluble large molecules consist of many small molecules joined together by chemical bonds and thus need to be hydrolysis before entering the bacterial cell, the hydrolysis step is carried out by several different anaerobic and facultative bacteria, the results of very small components with ionic characteristic, so the conductivity of the manure salary with increase gradually, by increase the decomposition, E.C for the three reactors increases.
Time (days) | Cow manure | Chicken manure | Mixed manure | |
---|---|---|---|---|
0 | 7.97 ± 0.02 | 8.50 ± 0 | 7.97 ± 0 | |
2 | 7.93 ± 0.04 | 8.50 ± 0 | 7.97 ± 0.01 | |
4 | 7.88 ± 0.04 | 8.49 ± 0.01 | 7.96 ± 0.01 | |
6 | 7.83 ± 0.04 | 8.48 ± 0 | 7.97 ± 0.02 | |
8 | 7.78 ± 0.04 | 8.45 ± 0.04 | 7.89 ± 0.13 | |
10 | 7.74 ± 0.02 | 8.41 ± 0.01 | 7.77 ± 0.05 | |
12 | 7.67 ± 0.07 | 8.40 ± 0.01 | 7.72 ± 0.02 | |
14 | 7.61 ± 0.01 | 8.40 ± 0.12 | 7.66 ± 0.06 | |
16 | 7.58 ± 0.04 | 8.39 ± 0.01 | 7.64 ± 0.03 | |
18 | 7.53 ± 0.04 | 8.33 ± 0.08 | 7.65 ± 0.01 | |
20 | 7.54 ± 0.06 | 8.27 ± 0.01 | 7.61 ± 0.05 | |
22 | 7.52 ± 0.09 | 8.23 ± 0.04 | 7.56 ± 0.01 | |
24 | 7.45 ± 0.03 | 8.20 ± 0.07 | 7.54 ± 0.01 | |
26 | 7.52 ± 0.09 | 8.20 ± 0.1 | 7.52 ± 0.02 | |
28 | 7.58 ± 0.01 | 8.20 ± 0.01 | 7.50 ± 0.01 |
COD and BOD values are presented in
This indicated that biogas production generated a bioremediation process of manure.
Influence of digested manure on plant growth is shown in
Properties | With Bio-Fertilizers | Without Bio-Fertilizers |
---|---|---|
Weight | 950 ± 50 g | 540 ± 35 g |
Color | Very Green | Dull and yellow |
Leaf area | Large area | Small area |
It can be noticed that biomass of lettuce is increased dramatically due to the use digested manure. It can be noticed that plant biomass increased about 75% compared to the control sample. Furthermore, the color of the treated plant was dark green whereas the control group was yellow. This indicated the influence of digested manure on the quality of plant growth.
Furthermore, it can be noticed that digested manure dramatically increased plant growth as seen by increased biomass and increased leaf area of lettuce (
The data in
The data in
The purification containers are transparent units to be able to visualize the reactions and to make the necessary chemical changes.
The purification process included removal of H2S, NH3 and CO2 according to the following equations
H 2 S + Fe → FeS (2)
CO 2 + Ca ( OH ) 2 → CaCO 3 (3)
NH 4 OH + H 3 BO 3 → BO 3 ( NH 3 ) 3 (4)
These equations are in agreement with El-Nahhal et al., [
The data in
This is in agreement with previous investigators [
The data in
Moreover, the data in
ORGANICMANTTER + O 2 → CO 2 + H 2 O (5)
ORGANICMANTTER + BACTERA → CO 2 + H 2 S + NH 4 OH + H 2 O (6)
CO 2 + METHANOGENESISBACTERIA → CH 4 + H 2 S + NH 3 (7)
Accordingly removal of COD and BOD is related to biogas productions. This is in agreement with El-Nahhal et al. [
The data in
A comparison between the present study and those from the literature is presented in
It is obvious that the present study dealt with raw cow, chicken and mixed manure whereas published work [
Tested parameter | Present study | Zhang et al. [ | Böjti et al. [ | Gomaa, and Abed [ |
---|---|---|---|---|
Cow manure | Ö | - | - | - |
Chicken manure | Ö | Ö | Ö | - |
Mixed manure | Ö | - | - | - |
Fecal | - | - | - | Ö |
Biogas production | Ö | Ö | Ö | Ö |
Biogas purification | Ö | - | - | - |
pH | Ö | Ö | - | - |
EC | Ö | - | - | - |
COD status | Ö | - | - | Ö |
BOD status | Ö | - | - | - |
Bioassay Digested manure | Ö | - | - | - |
from the impurities that emerged during the biodegration process was not achieved at any study except the present one which provided a chemical method for purification.
Moreover, the present study determined the physico-chemical properties of manure and provided kinetic evaluation of pH, EC, BOD, COD, whereas other studies provided kinetic evaluation for biogas production only except [
However, the study of Zhang et al. [
It can be concluded that the present study integrated the picture of biogas production by providing the value of mixed manure, purification method for the biogas and bioassay technique for the end product. So that this study is opening a new area of investigation in the biogas technology.
This study showed a simple and easy applicable method for biogas production. Biogas production was tremendously increased by time and reached maximum point after 28 days of operation under laboratory or field conditions. Produced biogas was higher from mixed manure than cow or chicken manner. Chicken manure produced the lowest quantity of biogas. The impurities associated with biogas were removed by chemical method. Reduction of BOD and COD indicated the bioremediation of manures. Application of digested manure as a fertilizer provided higher yield of agricultural production.
The authors declare no conflicts of interest regarding the publication of this paper.
Hammad, E.I., Al-Agha, M.R. and El-Nahhal, Y. (2018) Enhancing Biogas Production: Influence of Mixing Cow and Chicken Manures. Energy and Power Engineering, 10, 383-397. https://doi.org/10.4236/epe.2018.108024