E-ISSN: 2814 – 1822; P-ISSN: 2616 – 0668
ORIGINAL RESEARCH ARTICLE
1Bako, I., 1Bilal, S., and1Aliyu, A. A
1Department of Chemical Engineering, Faculty of Engineering, Ahmadu Bello University Zaria, Kaduna State, Nigeria
Corresponding Author’s Email: akidat2006@gmail.com
The depletion of fossil fuel reserves, energy crisis, industrialization, rapid growth in population and environmental issues across the globe have aroused interest and attention to be shifted to biofuels (biogas) production. This research focused on biogas production using co-digestion of Chicken droppings with Ipomoea perfurea grass through Simplex Centroid Design (S.C.D). The proximate compositions of the formulated substrates were determined on co-substrates A (Ipomoea perfurea), B (Chicken droppings), and A+B (equal mixture of Ipomoea perfurea and Chicken droppings). The volatility contents were 47.10, 52.60 and 55.80%, while moisture contents were 18.10, 16.01, and 14.20% and carbon contents were 29.26, 26.08, and 24.04% for formulations A, B, and A+B, respectively. The biogas production temperature (mesophilic), ranging between 26oC to 31oC, was observed after 42 days. The optimum yields for dried substrates were 334g/kg for mono substrates (B) and 357g/kg for co-substrates (A+B), while the optimum yield for fresh substrates was 410g/kg for mono-substrate A and 430.5g/kg for co-substrate A+B, respectively. The methane flammability test confirmed the biogas was combustible, and a pale bluish flame that burnt for 1minutes and 45seconds without soot was observed. The least and optimum C/N ratios for dried mono and fresh co-digested substrates were 14:1 and 21:1, respectively. The fresh co-digested substrates produced a better yield than the dried co-digested substrates in the production of biogas for cooking.
Keywords: Biogas, Mono-digestion, Co-digestion, Mesophilic temperature, Substrate.
Energy is an essential factor and also an ingredient that stimulates, supports economic growth and development (Dar et al., 2021). Global energy demand is fast growing with a rapid increase in population, industrialization, which accounts for about 88% of current fossil fuel demand (Marbaix et al., 2021). Biomass residues available from agricultural products and other allied derivatives constitute a potential source for bioenergy production (Saleem, 2022).
Currently, there exist numerous forms of bioenergy such as bioethanol, biodiesel, bio-methanol, bio-hydrogen, di-methylfuran (D.M.F), and biogas (Sindhu et al., 2019). Biogas remains a versatile mixture of gases, a sustainable source from anaerobic digestion of organic waste, such as animal waste (chicken droppings), plants/vegetation (grass), municipal waste and butchery remaining due to bioactivities of anaerobic microbes such as Clostridium spp, bacteroids and Aspergillus spp in the absence of oxygen (Godbole et al., 2023). Anaerobic breakdown remains a natural process in which complex biomass resources are broken down to smaller monomers. This is widely employed as a replenish energy source that produces appreciable methane, carbon dioxide, and other constituents in traces (Hussain et al., 2020). The breakdown process begins with biomass hydrolysis as the involved material breaks down biological polymer linkages to monomers such as sugars, which makes them available for microorganisms to utilize (Chukwuma et al., 2021). The Acidogenic bacteria degrade and convert the multipart polymeric compounds like sugar and amino acids into carbon dioxide, hydrogen, ammonia and organic acids, where the acetogenesis bacteria convert the resultant organic acid into acetic acid, which is collected with additional ammonia, hydrogen and carbon dioxide. The methanogenic bacteria therefore, degrade and converted the product into methane and carbon dioxide (Enzmann et al., 2018).
According to Liew et al. (2022), animal waste materials such as cow dung and Chicken droppings contain more readily digestible materials than other agricultural waste materials in biogas production. As such, studying various substrates before formulation for anaerobic digestion is commendable. Likewise, Wang et al. (2022) opined that co-digestion of poultry dung with added biological material recompenses abundant biogas yield, stocking of readily decomposable materials, better-quality and stability of nutrients in terms of C/N ratio, and decreases ammonia formation in anaerobic breakdown processes. This leads to weakening of toxic substances with superior quality gas and price decline due to the ability to process dissimilar substrates in a single set-up, owing to a higher concentration of lignin and lignocellulose bio-fibres of about 40 – 50 % total solids depending on substrates which increase a promising mixing atmosphere in anaerobic digesters (Elsayed et al., 2022).
\(T.S = \frac{M2 - M4}{M2}X\ 100\ \)……………………………………………………………………Eq. 2
Chicken droppings were acquired from NAPRI (A.B.U Zaria) in a clean polyethylene bag, sorted, and dried immediately to get rid of moisture. Ipomoea perpurea grass was obtained near a pond behind post graduate schools and the school of accounting at Ahmadu Bello University, Zaria. The grass identified at the Biological Science Department (Botany unit)herbarium A.B.U Zaria and a voucher number A.B.U V.N: 1635 was obtained and deposited. Size reduction was carried out to smaller particles of about 10mm using a cutter, part of the substrate was dried for 2weeks and crushed to powder using a mortar and pestle prior to proximate analysis, while part was used as a fresh substrate for the production. Mixing formulation was employed in designing the experiment as shown in Table 1, using Minitab software version 17 (Alfa et al., 2014).
Table 1: Design of Experiment
| Substrate ID | Standard order | Run order | Grass | Chicken Droppings | Percentage (%) | Ratios |
|---|---|---|---|---|---|---|
| A | 1 | 1 | 8,300 | 0 | 100 | 1:0 |
| B | 2 | 2 | 0 | 8300 | 100 | 0:1 |
| A+B | 3 | 3 | 4150 | 4150 | 50:50 | 1:1 |
Mixing formulation using (Mini tab software, Version 17) (Wall, 2015)
Key Note: A= Chicken droppings, B= Ipomoea purpurea, A+B= Chicken dropping+Ipomoea purpurea,
Fig 1. Schematic Experimental Design Set-up
Source: Oyewole et al. (2014)
The percentage ratio of the chicken droppings and Ipomoea perfurea grass in grams. Eight thousand three hundred grams of chicken droppings were weighed using a digital weighing balance and dissolved in a water bowl to form a slurry in (1:2). The slurry was filled into an anaerobic digester (5L gallon), and the anaerobic digester was sealed using 4-minute sealant gum to maintain an air-tight condition for suitable metabolic activities. The same procedure was repeated for other respective formulations. The biogas was eventually collected using a transparent graduated urine bag container as a collector (Oyewole, 2010).
The culture media used include Nutrient broth, Nutrient Agar (NA), Sabouraud dextrose agar (SDA), Potato dextrose Agar (PDA), Eosin Methylene Blue Agar (EMB), Centrimide Agar & Mannitol Salt Agar were prepared according to the manufacturer’s instructions.
One gram (1g) of the samples (A, B and A+B) were weighed and dissolved in 9mls of sterilized distilled water and allow for 10minutes and these were labeled as 10-1 followed by transfer of 1ml from10-1 to the next as 10-2, 10-3, up to 10-4 respectively (Aliyu, 2019). One milliliter (1 mL) from each of 10-4 was transferred into the petri plates, followed by NA and PDA for total bacterial and fungal counts. This was then followed by autoclaving at 30 ± 2 °C and at room temperature for 24 hours and 5 days (Aliyu, 2019).
The 10-4 dilution factor was spread using sterile bent glass onto nutrient agar and PDA plates for the enumeration and isolation of bacteria and fungi. The nutrient agar plates and PDA were incubated anaerobically at 37 °C for 24 hours and 5 days, respectively, inside an anaerobic candle jar (Adebayo, 2019). The bacteria and fungi that grew on different media were subcultured on respective nutrient agar and PDA plates. Bacterial and fungal counts were performed by placing the agar plate on a digital colony counter and counting (Oyewole, 2010; Islam et al., 2019).
Gram staining was done according to the standard method described by Osatogbe et al. (2024), while the biochemical profile includes;
Using a straight wire loop, the tested colonies were emulsified in Kosser's citrate media and incubated at 37 °C for 24 hours. A blue colour with growth indicates a positive result; no change in colour indicates a negative result (Osatogbe et al., 2024).
The tested organism was inoculated into peptone water and incubated at 37 °C for 24 hours. The indole reagent was added. Pink ring colour indicated a positive result. The absence of a pink ring on the surface indicated a negative result (Osatogbe et al., 2024).
The isolate was inoculated into motility medium by a fine stab with a sterile needle to a depth of 2 cm length of the bottom of the tube. It was then incubated at 37 °C for 24 hours. The line of inoculation was defined, and the medium was cleared for non-motile organisms, while the line of inoculation that was not defined for motile organisms was somewhat cloudy (Osatogbe et al., 2024).
Methane, a principal constituent of biogas with flammable characteristics, was tested by igniting a flame on a Bunsen burner connected to the digester, where a bluish flame was obtained and lasted for 1 minute 45 seconds (Fatima et al., 2018).
This was carried out using a pH meter. The pH meter was inserted into the slurry, and the reading was recorded after stability. Likewise, the Temperature measurement was carried out using a digital thermometer. The thermometer was inserted into the slurry, and the reading was recorded after the slurry had reached stability (Akintayo et al., 2020).
This was carried out using the gravimetric method described by Demarchi (2013). A measured weight (2g) of samples of A, B, and A+B was weighed into a moisture can and labeled. The samples were dried in an oven at 105 °C for 3 hours. Cooled in a desiccator and reweighed, and returned to the oven for further drying, cooling, and weighing repeatedly was carried out at an hourly interval until when there were no further diminutions in the weight that is constant weight was obtained. The weight of moisture was calculated and expressed as a percentage of the weight of the sample analyzed, given by the expression:
\(M.C = \frac{M3 - M1}{M2 - M1}X\ 100\ \)………………………………………………………………Eq. 1
Where,
m1= weight of empty moisture Can
m2= weight of empty can + sample before drying
m3= weight of can + sample dried to constant weight
The total solids (T.S.) content was determined according to Vaishnavi (2023) using a standard method. A sample of 2g was taken into a pre-weighted silica crucible and dried at a temperature of 105 °C for one hour (1 hr). The silica crucible containing the sample was placed in an oven at a temperature of 105 °C for six hours (6 hours). Afterwards, the crucible was placed in the desiccator until its temperature reduced to room temperature, and then it was weighed. Finally, the % Total solid(T.S) was determined using the relation as the quantity of the sample remaining in the crucible:
Where,
M2 = mass of crucible including sample and
M4 = is the mass of crucible plus residue after heating @ temperature of 550 °C.
Determination of the Volatile Solid Content (V.S)
The percentage volatile content was determined by ignition of the dried samples in an inert atmosphere at 550 °C. After Volatile Solids (V.S) determination, the silica crucible was placed into a muffle furnace at a temperature of 550 °C for 2 hours, where the loss of mass on heating was the measure of Volatile substance (V.S), which was determined using the relation below:
\(V.S = \frac{M4 - M1}{M3 - M1}X\ 100\)……………………………………………………………… Eq. 3
Where,
M1 = mass of empty crucible
M3 = mass of crucible plus residue after heating in an oven @ 105 °C,
M4 = mass of crucible plus residue after heating @ temperature of 550 °C (Vaishnavi, 2023).
The percentage volatile content was determined by ignition of the dried samples in an inert atmosphere at 550 °C. After Volatile Solids (V.S) determination, the silica crucible was placed into a muffle furnace at a temperature of 550 °C for 2hrs, where the loss of mass on heating was the measure of Volatile substance (V.S), which was determined using the relation below:
\(A.C = \frac{M2 - M3}{M2}X\ 100\ \)…………………………………………………………………Eq. 4
Where, M2 = Initial value, M3 = final value (Vaishnavi, 2023).
This was determined using the method of James et al. (2017). Zero-point one gram (0.1g) of samples A, B, and A+B were weighed using an analytical balance. The samples were then introduced into their respective 250ml conical flasks. Next, 10ml of 0.167 mol/L K2Cr2O7 was measured using a measuring cylinder, followed by 20ml of concentrated H2SO4. H2SO4 was added to the respective samples (Through the surface of the sample container), and dark green coloration was seen after the addition. This was allowed to stand for 30minutes and cool, after cooling, 100 mL of distilled water was added to the respective dark green coloration mixture and additional 5 drops of Ferroin indicator was added to solution above and this was titrated against 0.5mols of iron 2 sulphate FeSO4 until greenish colour was noticed, the % carbon content wasdetermined by the relation:
\(\% C = \frac{B - T\ \ x\ M\ \ x\ 1.33x0.003}{wt\ of\ sample}\ X\ 1OO\)......................................................................... Eq. 5
Where
B = blank sample
T= titre value
M= molarity of Iron sulphate
Zero-point one gram (0.1g) of the respective substrates A, B, and A+B was weighed and introduced into 100 mL of their respective conical flasks. Twenty milliliters (20ml) of Distilled water and 20ml of sulfuric acid were added to the respective substrates one at a time. A few copper catalyst particles were added to the substrates, then heated with the aid of a hot plate until it fumed, indicating the presence of Nitrogen. Filter paper was used to filter the mixture from the conical flask to the volumetric flask. A dark green to light yellow mixture was observed in the volumetric flask. Ten milliliters (10 mL) of the filtrate were introduced into a round-bottom flask, and 10 mL of 40% NaOH was added. An additional 10 mL of 2% boric acid was measured and introduced into a separate beaker, along with a few drops of mixed indicator. Then 0.01 Normal HCl was used to titrate against the distilled sample. The condenser was kept cool below 30 °C by allowing sufficient water to flow through, regulating heat, and minimizing frothing. Then, 50ml of the distillate was collected and distilled before stopping.
Then, % N content was determined by the relation:
\(\% N = \frac{0.14\ x\ V.D\ x\ N\ x\ 100xT.V}{wt\ of\ soil\ x\ Ad}\)............................................................................ Eq. 6
Where
V.D = volume of digest
N = Normality of Acid
TV = Titre value
Al = Aliquot of digest James et al. (2017).
The gas analyser was calibrated using manufacturers instructions. All tubing was ensured to be very tight, and none was leaking. Direct sampling was employed, and the gas source was connected directly to the analyser. The gas system was flushed and purged to avoid contamination from previous samples. The instrument was turned “ON” and allowed to warm up. The samples were labelled and introduced into the analyser for analysis, and stability was allowed to be attained before recording the results of the respective samples. The values for all respective components analysed were recorded (Mezex et al., 2017).
The data obtained were analyzed using descriptive statistics, where mean values, experimental design, and mixing ratio formulations were determined with the application of Minitab software version 17 (Sachin et al., 2023).
Figure 1 shows proximate composition results prior to the introduction of fresh/dried mono and co-digested substrates into the digester. The results revealed the potential of volatile organic matter for biogas production in relation to mono/ co–substrates, at 47.10%, 52.60%, and 56.80% for substrates A, B & A+B, respectively. The degree of volatility of the substrates was found to be higher with respect to the co-digested substrate A+B when mixed in an equal ratio than with mono substrates A and B.
From Figure 1, the potentiality in terms of solubility content revealed 18.09, 16.01 and 14.20% for substrates A, B & A+B respectively, this shows that the magnitude of solubility was a bit higher in carbon-based substrates (A) than Nitrogen based substrates (B), and likewise when mixed on same proportion (A+B) the potentiality was found to be the least, but reverse might be the case on different proportion.
However, also from Figure 1, the potentiality in terms of carbon content was found to be 29.26 26.08 and 25.04% % for substrates A, B & A+B respectively, this shows that substrate A was found to be rich (high) in carbon as a source of energy to the microbes than B and likewise A+B was found least when mixed in equal proportion.
Although ash content determines the reusability of the ash for other purposes after digestion, such as biofertilizer production. The result revealed a high content of ash with respect to mono substrates A (5.55%), B (5.31%), but least in co-digested A+B (4.96) substrates,
Figure 1:MeanProximate Analysis for Fresh Ipomoea Perfurea Grass and Chicken Dropping
Key: VS= Volatile solids, MC= Moisture content, CC= Carbon content, AS= Ash content
Figure 2 shows the biogas yield for dried and fresh Ipomoea perfurea grass as single substrates and with Chicken droppings as co-substrates. The results indicated that biogas production began from the first day across all substrates that consisted of substrate A (100%, 1:0) Ipomoea perfurea grass; B (100%, 0:1) Chicken dropping, A+B (50%:50%, 1:1) combination of the 2 substrates in equal proportion. The results also revealed that anaerobic microorganisms, such as Clostridium spp., bacteroids, and Aspergillus spp., were relatively active, and biodegradation began from the first day after introducing the substrates into the digester. This may be attributed to the nature of the substrate, the magnitude of the volatility of organic matter, and the synergetic effect that resulted in a carbon-nitrogen balance.
Figure 2: Mean Biogas yield from the Co-digestion of Chicken dropping and Ipomoea perfurea grass
Confirmatory flame tests (Plate 3 and 4) show methane at the hydrolysis and methanogenesis stages. At the hydrolysis stage, immediately after opening the biogas collector and igniting the flame, the flame was extinguished, confirming a higher presence of CO2 at that stage than methane, as well as hydrogen, hydrogen sulfide, and traces of other gases. While at the methanogenesis stage (plate 4), immediately after opening the biogas collector and igniting the flame, a bluish flame was observed that lasted for 1 minute. 45 seconds confirming methane gas.
Plate 1: Biogas production in progress
Plate 2: Biogas in a urine bag collector
Plate3: Flammability test at Hydrolysis stage
Plate 4: Blue Flame at Methanogenesis stage
Table 3 presents the mean and standard deviation of bacterial and fungal populations (expressed as ×10⁴ colony-forming units, CFU) in three sample categories. Sample A, Sample B, and a combination of both (A + B). The results indicate notable differences in microbial load across the samples.
Table 3: Mean and Standard Deviation for Bacteria and Fungi Counts
| Sample ID | Bacteria Count (104) | Fungi count (104) |
|---|---|---|
| A | 107 ± 3.0 | 65.5 ±2.5 |
| B | 152 ± 4.0 | 44.5 ± 3.5 |
| A + B | 390 ± 2.0 | 49.5 ±3.5 |
Table 4 shows the compositional profile of biogas production. The results revealed higher methane content with respect to fresh mono- and co-digested substrates than dried mono- and co-substrates, at 57, 56, and 60.5% for fresh mono/co-substrates A, B, and A+B, respectively, while 50, 49.5, and 51% for dried mono/co substrates, respectively. This indicates that the methane content was found to be higher in both fresh mono/co-formulated substrates and in dried substrates.
However, the methane content determined the magnitude of flammability and extent of combustion from 41- 45% according to Ofoefule et al. (2010) who reported ‘Biogas production from blends of Bambara nut Chaffs with some plants and animal waste’. This may be attributed to the nature of the substrates, their formulation, and the proportional volatility of the substrates, as well as the efficiency of microbial activity that led to effective digestion. Additionally, synergy between carbon and nitrogen contributed to a reasonable methane content in the biogas.
Table 4: Compositional Analysis from the Co-digestion of Chicken Droppings and Ipomoea perfurea Grass
| Parameters | CO% | Methane (CH4) % | CarbonDioxide (CO2)% | Oxygen (O2) % | Hydrogen (H2) % | |||||
|---|---|---|---|---|---|---|---|---|---|---|
| Subs. I.D | Dried | Fresh | Dried | Fresh | Dried | Fresh | Dried | Fresh | Dried | Fresh |
| A: Ipomoea perfurea | 0 | 0 | 51 | 56 | 22 | 21.5 | 15.5 | 9.5 | 10 | 11.5 |
| B: Chicken Droppings | 0 | 0 | 49.5 | 57 | 23 | 20.5 | 13.5 | 9.0 | 12.5 | 11.5 |
| A+B | 0 | 0 | 50 | 60.5 | 22.5 | 21 | 15 | 5.5 | 10.5 | 11.5 |
The volatile solids (VS) increased in the 1:1 mixture in this study is consistent with the report of Li et al. (2013), who observed better volatile solid degradation during the co-digestion of kitchen waste, maize stover, and chicken manure. According to Romero-Guiza et al. (2014), solid-state digestion benefits from lower moisture, which bolsters the advantages of the low moisture found in the 1:1 combination observed in this study. This study's carbon content results are similar to those of Samadi et al. (2024), who found that co-digestion optimized microbial digestion by balancing the high C/N ratio of lignocellulosic biomass with the low C/N ratio of poultry manure.The advantages of co-digestion were further supported by Okewale and Babayemi (2019) who similarly demonstrated that poultry droppings enhanced the anaerobic digestion performance of elephant grass. However, the low ash percentage observed in the 1:1 mixture corresponds with the report of Hasan et al. (2023), who highlight the positive correlation between decreased ash content and improved volatile matter and energy output. Likewise, the strong methane potential for co-digestion in this investigation was suggested by other studies, which found methane outputs ranging from 300 to 1200 mL/g volatile solids, depending on the substrate balance and synergy (Li et al., 2015; Hassan et al., 2023).
According to studies, co-digestion techniques frequently shorten lag phases and increase microbial hydrolytic activity. The study's rapid commencement of biogas production across all treatments (A, B, and A+B) is consistent with this finding (Owamah et al., 2014; Zhang et al., 2020). For example, Zhang et al. (2020) reported effective lignocellulose breakdown in co-digestion systems, which they partially attributed to fungal activity. These findings are consistent with yours. With the A+B treatment, a synergistic effect is likely associated with improved C/N ratios. Co-digestion frequently improves nutrient balance and increases biogas yields above those of mono-digestion, a finding highly confirmed by various studies (Hassan et al., 2020). The findings in this study with respect to yield shows an improved biodegradation and microbial activity from day one which are supported by other studies that revealed 20–24% higher bio-methane outputs and synergistic effects in the same C/N range when grass and manure are mixed ( meadow grass + cattle dung) (Song et al., 2023). It has been observed that Aspergillus and Penicillium species play important roles in the breakdown of lignocellulose during co-digestion, which helps produce biogas much earlier (Owamah et al., 2014). The rapid decline in volatile solids and the commencement of gas production in this investigation were likely due to their enzymatic activity.
The biogas ignition test reveals a visible flame that signifies successful combustion and verifies the presence of enough methane in the generated gas. To maintain ignition and a steady flame, methane combustion typically requires a minimum concentration of approximately 40% CH₄ in the gas mixture (Cellek et al., 2024). Furthermore, stable combustion indicates that harmful amounts of inhibitory gases, like ammonia or hydrogen sulfide, were absent, which is consistent with other studies showing that well-balanced anaerobic digestion processes produce cleaner, flammable gas (Bastiaans, 2023). The observed flame likely results from a methane-rich mixture produced by the effective co-digestion of the substrates in this study. The flammability test observed in this study was in conformity with the work of Aliyu (2019), who reported ‘Biogas production from cow dung for sustainable energy generation. The results were also in agreement with the work of Ajiboye et al. (2018), who reported the evaluation of the effect of sodium solution on biogas yield for the anaerobic digestion of poultry waste and digestate.
Sample A had a bacterial count of 107 × 10⁴ CFU and a fungal count of 65.5 × 10⁴ CFU, suggesting a relatively high level of fungal presence compared to the bacterial population. In contrast, Sample B exhibited a higher bacterial count of 152 × 10⁴ CFU but a significantly lower fungal count of 44.5 × 10⁴ CFU. This inverse pattern in microbial dominance suggests varying environmental or compositional conditions influencing microbial proliferation in the two sample types, as also reported in previous studies (Smith & Jones, 2020). Interestingly, the combined sample (A + B) showed a marked increase in bacterial count (390 × 10⁴ CFU), which exceeds the sum of the individual means for Samples A and B. This may imply synergistic microbial interactions or changes in substrate conditions that promote bacterial growth when the two samples are combined (Kumar et al., 2021). However, the fungal count in the combined sample (49.5 × 10⁴ CFU) falls between the values observed in Samples A and B, indicating a possible stabilizing effect or competition between fungi and bacteria in the combined environment.
The methane content in this study was higher than that reported by Ofoefule et al. (2010), who reported Biogas production from blends of Bambara nut Chaffs from plants and animals, which indicated the magnitude of flammability and extent of methane combustion at 41-45%. However, this may be attributed to the nature of the substrates, their formulation, and the proportional volatility of the substrates, as well as the efficiency of microbial activity that led to effective digestion, and, of course, synergy between carbon and nitrogen, which contributed to a reasonable methane content in the biogas. The profiles were in agreement with the work of Natthawud et al. (2017) who reported ‘Biotechnological application of sustainable Biogas production through dry anaerobic digestion of Napier grass’. Likewise, dried mono- and co-substrates had a higher content in terms of carbon dioxide, oxygen, and hydrogen than fresh mono- and co-substrates.
The result obtained revealed a bit higher content of CO2in dried Ipomoea perfurea grass both for mono and co-substrates ranging from 22 – 23%, but a bit lower in fresh co and mono- substrates ranging from 20.5 - 21.5 %, though excess CO2 may serve as agent that hinders compression of biogas into the cylinder and the impurities inhibits methanogenic microorganism from conversion of materials for bioenergy production. However, the profile further revealed a lower oxygen content in fresh substrates, showing a more promising combustion range of 5.5–9.5% compared to dried substrates, which ranged from 13.5% to 15.5%.This was commendable because the oxygen content might be detrimental to the entire anaerobic digestion process. This indicates that methanogenic microorganisms are highly sensitive to oxygen and cannot thrive in oxygenated conditions, which consequently inhibits methane production. The results obtained were in agreement with the work of Pedizzi et al. (2016), who reported the Effect of oxygen on the microbial activities of thermophilic anaerobic biomass. Perhaps H2 may serve as an important intermediate product in anaerobic digestion processes, aiding stability to ignition and combustion, and also acting as a reducing agent for the conversion of carbon dioxide into methane. The result revealed an H2 content of 11.5% for fresh substrates, but slightly higher in dried substrates, ranging from 10 to 12.5% accordingly. The result agreed with the work of Gawel et al. (2022), who reported hydrogenation from sour cabbage through dark fermentation.
Based on the study, the proximate analysis profile revealed the proximate compositions of substrates A, B, and A+B with respect to their volatility, moisture, ash, and carbon content. Co-substrates A+B had the best volatility content, carbon content, and the least ash content compared to the mono-substrate. In contrast, mono-substrates had higher solubility compared to co-substrates. However, varying the proportion of the substrates may alter the trend. The best biogas yields were A+B (357g/kg) and A+B (430.5g/kg) for dried and fresh substrates, respectively. The methane flammability test confirmed that the biogas was combustible and burned with a pale, bluish flame, producing no soot, for 1 minute and 45 seconds. The fresh / dried co and mono substrates revealed the same synergy with a Carbon-Nitrogen (C/N) ratio of 21:1, 15:1, and 14:1 for A+B, A, and B, respectively. The Optimum methane content for fresh substrates in the study was 60.5%, whereas dried substrates had an average of 51%.
Adebayo, A. O., Jekayinfa, S. O., Ahmed, N. A., & Ogunkunle, O. (2019). Effect of organic loading rate on biogas yields of pig slurry in a continuously stirred tank reactor at mesophilic temperature. Procedia Manufacturing, 35, 337–342. [Crossref]
Ajiboye, A. V., Lasisi, K. H., & Babatola, J. O. (2018). Evaluation of the effect of sodium hydroxide solution on biogas yield of anaerobic digestion of poultry waste and the digestate. International Journal of Energy and Water Resources, 2(1), 23–31. [Crossref]
Akintayo, O. A., Hashim, Y. O., Adereti, A. G., Balogun, M. A., Bolarinwa, I. F., Abiodun, O. A., & Alabi, O. F. (2020). Potentials of rice as a suitable alternative for the production of ogi (a cereal-based starchy fermented gruel). Journal of Food Science, 85(8), 2380–2388. [Crossref]
Alfa, M. I., Olatunde, S. D., & Oliver, J. (2014). Comparative evaluation of biogas production from poultry droppings, cow dung, and lemon grass. Journal of Bioresource Technology, 57, 270–277. [Crossref]
Aliyu, S. (2019). Biogas production using different wastes: A review. UMYU Journal of Microbiology Research, 4(2), 75–82. [Crossref]
Aremu, M. O., & Agarry, S. E. (2013). Enhanced biogas production from poultry droppings using corn-cob and waste paper as co-substrate. International Journal of Engineering Science and Technology, 5(2), 247–253.
Bagudo, B. U., Garba, B., Dangoggo, S. M., & Hassan, L. G. (2008). Comparative study of calorific values and proximate analysis of biogas from different feedstock. IOP Conference Series: Materials Science and Engineering.
Bastiaans, R. J. (2023). Combustion emissions, health and energy transition aspects: The biomass gas case. Journal ISSN, 2766, 2276. [Crossref]
Cellek, M. S., Demir, U., & Coskun, G. (2024). Investigation effects of different calorific values and operating conditions on biogas flame: A CFD study. Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 46(1), 8171–8189. [Crossref]
Chukwuma, O. B., Rafatullah, M., Tajarudin, H. A., & Ismail, N. (2021). A review on bacterial contribution to lignocellulose breakdown into useful bio-products. International Journal of Environmental Research and Public Health, 18(11), 6001. [Crossref]
Dange, P., Pandit, S., Jadhav, D., Shanmugam, P., Gupta, P. K., Kumar, S., Kumar, M., Yang, Y.-H., & Bhatia, S. K. (2021). Recent developments in microbial electrolysis cell-based biohydrogen production utilizing wastewater as a feedstock. Sustainability, 13(16), 8796. [Crossref]
Dar, R., Parmar, M., Dar, E., Sani, R., & Phutela, U. (2021). Biomethanation of agricultural residues: Potential, limitations and possible solutions. Renewable and Sustainable Energy Reviews, 135, 110217. [Crossref]
Deepanraj, B., Sivasubramanian, V., & Jayaraj, S. (2014). Biogas generation through anaerobic digestion process—An overview. Research Journal of Chemistry and Environment, 18(5).
Demarchi, S. M., Ruiz, N. A. Q., De Michelis, A., & Giner, S. A. (2013). Sorption characteristics of rosehip, apple and tomato pulp formulations as determined by gravimetric and hygrometric methods. LWT-Food Science and Technology, 52(1), 21–26. [Crossref]
Elsayed, M., Andres, Y., & Blel, W. (2023). Anaerobic co-digestion of linen, sugar beet pulp, and wheat straw with cow manure: Effects of mixing ratio and transient change of co-substrate. Biomass Conversion and Biorefinery, 13(13), 11831–11840. [Crossref]
Enzmann, F., Mayer, F., Rother, M., & Holtmann, D. (2018). Methanogens: Biochemical background and biotechnological applications. AMB Express, 8(1), 1–1. [Crossref]
Gawel, S. (2022). Analysis of biogas component production for anaerobic digestion of sour cabbage in microaeration conditions under different pH conditions. Biomass, 2(1), 14–26. [Crossref]
Godbole, A., Wadetwar, R. N., Lawal, T. O., Mahady, G. B., & Raut, N. A. (2023). Microbiology of waste. In 360-Degree Waste Management, Volume 1 (pp. 159–184). Elsevier. [Crossref]
Hassan, M. S., Saba, A., & Zhu, H. (2023). Methane generation from anaerobic co-digestion of cassava waste and poultry manure: Optimization and kinetic evaluation. Renewable Energy, 209, 842–851. [Crossref]
Hussain, Z., Mishra, J., & Vanacore, E. (2020). Waste to energy and circular economy: The case of anaerobic digestion. Journal of Enterprise Information Management. [Crossref]
Islam, M. A., Biswas, P., Sabuj, A. A. M., Haque, Z. F., Saha, C. K., Alam, M. M., & Saha, S. (2019). Microbial load in bio-slurry from different biogas plants in Bangladesh. Journal of Advanced Veterinary and Animal Research, 6(3), 376. [Crossref]
James, N. D., de Bono, J. S., Spears, M. R., Clarke, N. W., Mason, M. D., Dearnaley, D. P., ... & Sydes, M. R. (2017). Abiraterone for prostate cancer not previously treated with hormone therapy. New England Journal of Medicine, 377(4), 338–351. [Crossref]
Khalid, A., Arshad, M., Anjum, M., Mahmood, T., & Dawson, L. (2011). The anaerobic digestion of solid organic waste. Waste Management, 31(8), 1737–1744. [Crossref]
Kucuker, M. A., Demirel, B., & Onay, T. T. (2020). Enhanced biogas production from chicken manure via enzymatic pretreatment. Journal of Material Cycles & Waste Management. [Crossref]
Kumar, R., Patel, S., & Mehta, P. (2021). Microbial synergy and antagonism in mixed cultures: Ecological and industrial perspectives. Journal of Microbial Ecology, 49(3), 210–219. [Crossref]
Li, W., Li, Q., Zheng, L., Wang, Y., Zhang, J., Yu, Z., & Zhang, Y. (2015). Potential biodiesel and biogas production from corncob by anaerobic fermentation and black soldier fly. Bioresource Technology, 194, 276–282. [Crossref]
Liew, C. S., Yunus, N. M., Chidi, B. S., Lam, M. K., Goh, P. S., Mohamad, M., ... & Lam, S. S. (2022). A review on recent disposal of hazardous sewage sludge via anaerobic digestion and novel composting. Journal of Hazardous Materials, 423, 126995. [Crossref]
Marbaix, J., Mille, N., Carrey, J., Soulantica, K., & Chaudret, B. (2021). Magnetically induced nanocatalysis for intermittent energy storage: Review of the current status and prospects. Nanoparticles in Catalysis: Advances in Synthesis and Applications, 307–329. [Crossref]
Mézes, L., Bai, A., Nagy, D., Cinka, I., & Gabnai, Z. (2017). Optimization of raw material composition in an agricultural biogas plant. Trends in Renewable Energy, 3(1), 1–10. [Crossref]
Mukhtar, F., Abubakar, A., Saulawa, U. A., & Garba, H. (2018). Biogas production from cow dung for sustainable energy generation. UMYU Journal of Microbiology Research, 3(1), 81–86. [Crossref]
Musa, B., & Raji, H. M. (2016). Quantitative and qualitative analysis of biogas produced from three organic wastes. International Journal of Renewable Energy Research, 6(1), 299–305.
Natthawud, D., Rameshprabu, R., & Tapana, C. (2017). Biotechnological application of biogas production from locally sourced substrate materials. Nigerian Journal of Basic and Applied Sciences, 16(2).
Natthawud, D., Rameshprabu, R., & Tapana, C. (2017). Biotechnological application of biogas production from locally sourced substrate materials. Nigerian Journal of Basic and Applied Sciences, 16(2).
Ofoefule, A. U., & Ibeto, C. N. (2010). Effect of chemical treatment on biogas production from Bambara nut chaff and its blend with wastes. Biomass Unit, National Centre for Energy Research & Development, University of Nigeria, Nsukka. [Crossref]
Ojo, A. O., Lasisi, K. H., Nurudeen, S. A., Akinmusere, O. K., & Babatola, J. O. (2019). Engineering design of combined septic tank with treatment facilities for partial treatment of wastewater. Research Article.
Okafor, E. D. I. F., & Ugwuoke, P. E. (n.d.). Proceedings of the 4th International Conference/Training Workshop on Energy for Sustainable Development in Africa.
Okewale, A. O., & Adesina, O. A. (2019). Evaluation of biogas production from co-digestion of pig dung, water hyacinth and poultry droppings. Waste Disposal & Sustainable Energy, 1(4), 271–277. [Crossref]
Olawole, S. I., & Opeyemi, S. A. (2014). Evaluating the biogas yield and design of biodigester to generate cooking gas from human faeces. Leonardo Electronic Journal of Practices and Technologies, 13(24), 1–12.
Osatogbe, A. J., Attah, D. D., Manga, S. S., & Farouq, A. A. (2024). Bacteria isolates from oral cavities of malnourished children at Specialist Hospital, Sokoto, Nigeria. International Journal of Medical Research and Health Sciences, 7(4), 1–21.
Owamah, H. I. (2019). Optimization of biogas production through selection of appropriate inoculum-to-substrate (I/S) ratio. Nigerian Journal of Technological Development, 16(1), 17–24. [Crossref]
Oyewole, M. O., Olugasa, T. T., & Odesola, I. F. (2014). Energy production from biogas: A conceptual review for use in Nigeria. Renewable and Sustainable Energy Reviews, 32, 770–776. [Crossref]
Oyewole, O. A. (2010). Biogas production from chicken droppings. Science World Journal, 5(4).
Pedizzi, C., Rodriguez, I., Rodriguez, I., Verde, Lema, J. M., & Carballa, M. (2016). Effect of oxygen on the microbial activities of thermophilic anaerobic biomass. Bioresource Technology, 211, 765–768. [Crossref]
Romero-Guiza, M. S., Peces, M., Astals, S., Benavent, J., Valls, J., and Mata Alvarez, J. (2014). Implementation of Proto type Optical Sorter as Core of the new Pretreatment Configuration of a Mechanical- Biological Treatment Plant Treating of MSW through anaerobic-digestion. Applied energy. 135: 63 -70. [Crossref]
Sachin, K. G., Chandan, B. M., & Sagar, M. A. (2023). Experimental investigation and optimization of light transmitting brick using ANOVA method of regression using Minitab software. Materials Today: Proceedings.
Saleem, H., Sadaqat, H. A., Razzaq, H., & Ramazan, J. (2022). Sorghum as a potential source of sustainable bioenergy crop. Journal of Agricultural and Forestry Meteorological Studies, 1(1), 1–6.
Samadi, M. T., Leili, M., Rahmani, A., Moradi, S., & Godini, K. (2024). Anaerobic co-digestion using poultry slaughterhouse and vegetable wastes to enhance biogas yield: Effect of different C/N ratios. Biomass Conversion and Biorefinery, 14(22), 28303–28311. [Crossref]
Sharma, N., Yadav, A., Yadav, S., Singh, S., Sharma, A. K., & Kumar, S. (2025). Insights into application of novel citric acid modified Saccharum munja biosorbent for facile removal of fuchsin basic dye, crystal violet dye and copper metal ion: Statistical modelling, kinetics, thermodynamics and equilibrium studies. Biomass Conversion and Biorefinery, 15(5), 7139–7162. [Crossref]
Sindhu, R., Binod, P., Pandey, A., Ankaram, S., Duan, Y., & Awasthi, M. K. (2019). Biofuel production from biomass: Toward sustainable development. Current Developments in Biotechnology and Bioengineering (pp. 79–92). [Crossref]
Smith, L., & Jones, T. (2020). Fungal and bacterial dynamics in cohabited environments: Patterns of interaction and competition. Microbiology Research Reports, 38(2), 155–162. [Crossref]
Song, Y., Pei, L., Chen, G., Mu, L., Yan, B., Li, H., & Zhou, T. (2023). Recent advancements in strategies to improve anaerobic digestion of perennial energy grasses for enhanced methane production. Science of the Total Environment, 861, 160552. [Crossref]
Tambuwal, A. D., & Ogbiko, C. (2018). Proximate and chemical analyses of selected agricultural wastes used for biogas production. SRA-Archives, 9(1), 55–60.
Ugochukwu, C. O., Ejiroghene, O., & Anthony, O. O. (2016). Comparative study of the optimal ratio of biogas production from various organic waste and weeds for digester and retard digester. Journal of King Saud University - Engineering Sciences.
Vaishnavi, S. M., & Ganesh, A. H. (2023, December). Proximate analysis of lignocellulose biomass used for production of biogas anaerobically. In AIP Conference Proceedings (Vol. 2901, No. 1, p. 050003). AIP Publishing LLC. [Crossref]
Wall, A. M., Allien, E., Herrmann, C., Xia, A., & Murphy, J. D. (2015). Gross energy yield of third generation gaseous biofuels sourced from seaweed. Energy, 81, 352–360. [Crossref]
Wang, D., Huang, H., Jiang, Y., Duan, X., Lin, X., Aghdam, M. S., & Luo, Z. (2022). Exogenous phytosulfokine α (PSKα) alleviates chilling injury of banana by modulating metabolisms of nitric oxide, polyamine, proline, and γ-aminobutyric acid. Food Chemistry, 132179. [Crossref]
Zhang, X., Witte, J., Schildhauer, T., & Bauer, C. (2020). Life cycle assessment of power-to-gas with biogas as the carbon source. Sustainable Energy & Fuels, 4(3), 1427–1436. [Crossref]