Abstract

The management of the environment in slaughterhouses and of rumen contents requires great care to prevent any environmental or health risks. Moreover, rumen contents can be used to produce energy through anaerobic digestion, which would help avoid risks associated with the disposal of such organic waste into the natural environment, particularly in developing countries. However, any waste recovery policy—particularly those involving slaughterhouse waste—requires a thorough quantitative and qualitative assessment. This study aims to evaluate the quantity and quality of bio-waste produced at the municipal slaughterhouse in Man (Côte d’Ivoire), while analyzing the site’s environmental conditions. The methodological approach combines interviews with slaughterhouse managers and analyses of the physicochemical characteristics of the rumen contents of cattle slaughtered at the facility. The results highlight a lack of adequate waste management, with the discharge of rumen contents into the city’s main waterway (the Koh River) and the accumulation of carcasses. The slaughterhouse slaughters approximately 21 cattle on an average day, with peaks during holiday periods 35 on Christmas Day, 39 on New Year’s Day, 43 on Eid al-Fitr (marking the end of Ramadan), and 42 the day after Eid al-Adha (festival marking the conclusion of the Hajj pilgrimage), with consistent weight, and generates an average of 25.90 kg of rumen waste per cattle. The average physicochemical characteristics of the slaughterhouse’s rumen waste are a pH of 6.9, 84.1% moisture, 15.9% dry matter, 88.1% volatile matter, 3.5% nitrogen, 50.6% carbon, and a carbon-to-nitrogen (C/N) ratio of 14.5. The utilization of this waste will theoretically lead to the production of 66683.01 m³ of bio-methane annually. This study highlights the potential for utilizing beef rumen waste from the Man slaughterhouse in biogas production. It emphasizes the necessity of co-digestion with a carbon-rich substrate to enhance the carbon to nitrogen (C/N) ratio, which is crucial for effective biogas conversion.

Keywords

Health Risk, Rumen Waste, Rumen Content, Man (Côte d’Ivoire), Koh River

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1. Introduction

Waste management remains a critical environmental and public health issue, particularly in developing countries where inadequate methods such as open-air landfills and open burning predominate. These practices, as highlighted by Zhang et al. [1] and Anokye et al. [2], contribute to widespread contamination of water sources, the proliferation of diseases, and significant greenhouse gas emissions, all of which are the result of substandard waste management practices. Key problems include uncontrolled landfills, unregulated burning of waste materials, and inadequate management of leachate produced from the decomposition of waste. The situation is particularly dire in urban areas, exacerbated by high population density and rapid urbanization, which complicate the effective management of municipal solid waste. The ramifications of these issues manifest in various forms, including visual pollution, air quality deterioration, unpleasant odors, increased emissions of greenhouse gases, proliferation of disease vectors, and contamination of both surface and groundwater resources, confirming findings by Ferronato and Torretta [3].

Given the challenges surrounding municipal solid waste management in developing countries, considerable research has focused on household waste issues [1] [2] [4], disposal methods, and projections for future waste generation [5]-[7]. A significant yet often overlooked contributor to this problem is slaughterhouse waste, especially the rumen content from cattle. Poorly managed rumen waste leads to serious environmental issues, notably water and soil pollution, as improper disposal practices contaminate water sources, resulting in eutrophication and the degradation of water quality [8] [9]. Additionally, the accumulation of organic waste in open areas attracts disease vectors such as flies and rodents, heightening the risk of waterborne and diarrheal diseases as well as respiratory illnesses among local populations. The unsightly odor from anaerobic decomposition poses an additional challenge, affecting air quality and causing discomfort in communities. Moreover, the solid waste can obstruct urban sewer systems, exacerbating the risk of flooding during heavy rainfall events [9] [10].

To enhance the management of rumen waste and mitigate its adverse effects, several strategies can be pursued, including composting, utilizing it as animal feed, implementing controlled agricultural applications, and employing anaerobic digestion [11]. Specifically, anaerobic digestion stands out as a method that facilitates the conversion of ruminal contents into biogas, effectively reducing both the volume of waste produced and methane emissions. This process presents a viable alternative energy solution, particularly crucial given the continued reliance on fossil fuels, which contribute significantly to environmental degradation, climate change, and various public health challenges [12] [13]. The integration of anaerobic digestion could thus play a pivotal role in addressing energy needs sustainably and reducing the ecological footprint associated with traditional energy sources [6] [14].

In Côte d’Ivoire, annual meat consumption is roughly 13.0 kg per person, with beef constituting the most significant portion at 4.9 kg in 2016. Beef consumption saw a slight increase from 2.5 kg per capita in 2017 to 2.7 kg in 2018, reflecting both local production and cattle imports. This situation generates large amounts of organic byproducts, notably rumen contents, which are frequently mismanaged in slaughterhouses [15]. The resulting environmental challenges are particularly severe in the nation’s secondary cities, where insufficient political commitment and coordination hinder effective quality oversight by public authorities [16]. The municipal slaughterhouse in Man, the capital of the Tonkpi region, exemplifies this crisis. Established in 1945, the facility has deteriorated significantly and lacks adequate infrastructure to handle waste. Blood and rumen waste are carelessly discarded on an unpaved floor, ultimately polluting the nearby Koh River [17]. This research seeks to evaluate the quantity and quality of bio-waste produced at the Man municipal slaughterhouse, while also scrutinizing the environmental conditions of the site to better understand the on-site management of rumen waste.

2. Materials and Methods

2.1. Study Area

This study examines the municipal slaughterhouse in Man, western Côte d’Ivoire. It is located between latitudes 7˚20' and 7˚35' North and longitudes 7˚25' and 7˚45' West [18]. Built in 1945, the slaughterhouse underwent renovations in 2019. It is conveniently located next to a river (the Koh) and the city center (see Figure 1). It comprises three main facilities: a slaughter shed, cattle cages and an area for basic tasks such as hoof trimming and skin smoking. The operational procedures at the slaughterhouse are characterized by an outdated assembly-line approach. These include tasks such as providing livestock by pen attendants, manually killing animals by butchers, processing corpses by cutters, and cleaning meat by cleaners. Finally, tricycles are used to distribute meat to nearby markets.

Figure 1. Study area.

2.2. Data Collection

The data collection comprised three primary operations, which took place between January and March 2024: counting the number of cattle killed, conducting field observations and launching a campaign to weigh the rumen contents. Furthermore, rumen samples were subjected to physicochemical tests in chemistry laboratories at the University of Man and the Félix Houphouët-Boigny National Polytechnic Institute in Yamoussoukro, Côte d’Ivoire.

2.2.1. Estimation of the Number of Cattle Slaughtered at the Slaughterhouse and Field Observations

To gain a concrete understanding of the number of cattle slaughtered at the Man slaughterhouse, as well as the environmental conditions, discussions were held with the facility’s managers, followed by a tour of the premises. The objective was to collect data on the number of animals slaughtered during peak periods throughout the year. In addition, a daily count was conducted over the course of a week to estimate the number of cattle slaughtered on an average day. This daily count, conducted between January and March 2024, was carried out during a period without festivities in order to observe the normal flow of animal slaughter at the facility. In addition, the analysis was designed to cover all seven days of the week, with the aim of identifying any trends that might emerge throughout the week.

The assessment of environmental conditions included an inspection of the various sections of the slaughterhouse, accompanied by photographs taken on-site to illustrate the findings.

2.2.2. Weighing Campaign and Rumen Content Sampling

The weighing campaign aimed to evaluate the average amount of rumen residue produced by the slaughterhouse in Man. On each weekday, three rumen samples were collected from different cattle selected from those scheduled for slaughter that day, and weighed to quantify ruminal waste production. After assessing the rumen contents from each cattle, approximately 1 kg samples were collected in plastic bags for subsequent physicochemical analysis of the residues. By the end of the week, a total of 21 samples of rumen contents had been successfully collected for analysis purposes.

2.2.3. Physicochemical Analysis of Rumen Contents

In the study, rumen samples obtained from a slaughterhouse were carefully examined, with three subsamples taken from each main sample to ensure the reliability of the findings. This systematic approach allowed for replicated analyses across all assessed parameters, reinforcing the accuracy of the data evaluation and validating the robustness of the results.

The physicochemical parameters identified in the daily collected rumen samples included pH, dry matter (DM) content, volatile organic matter (VOM) content, moisture (M) content, total carbon (C) content, and nitrogen (N) content. Additionally, the carbon-to-nitrogen (C/N) ratio was calculated to provide further insight into the samples.

The dry matter content, reflecting the total solid residue left after drying a sample at 105˚C for 24 hours, was determined using Equation (1), as referenced by the American Public Health Association (APHA) guidelines [19]. This rigorous methodological framework is essential for ensuring the reliability and credibility of the research findings.

$\text{\%DM}=\frac{\text{DMM}}{\text{TM}}\times 100$ (1)

With:

• DMM corresponds to the dry matter mass;

• TM corresponds to the total mass of the samples.

In accordance with Equation (2) provided by the APHA [19], the moisture content (%M) was determined by calculating the difference in sample mass before and after the drying process.

$\text{\%M}=\frac{\text{TM}-\text{DMM}}{\text{TM}}\times 100\text{or}100-\text{\%DM}$ (2)

The volatile organic matter (VOM) content was calculated by incinerating the residue from the dry matter (TS) test in an oven preheated to 550˚C for two hours. Then, the amount of organic matter in the sample was determined using Equation (3), also described by the APHA [19].

$\text{\%VOM}=\frac{\text{DMM}-\text{MSD}}{\text{TM}}\times 100$ (3)

With:

• DMM corresponds to the dry mass of the sample.

• MSD corresponds to the mass of the sample after oven drying.

• TM corresponds to the total mass of the sample.

The total organic carbon (TOC) in the waste was estimated using Equation (4), proposed by Allison [20]:

$\text{\%TOC}=\frac{\text{\%VOM}}{1.74}$ (4)

The total nitrogen concentration of the substrates was determined using the Kjeldahl method. First, approximately 2 g of dried substrate samples were added to a digestion tube containing 15 mL of concentrated sulfuric acid. Then, approximately 7 g of potassium copper sulfate were added. The tube was heated to 37˚C using a digestion block. The ammonium ion was converted to ammonia by adding sodium hydroxide. Then, the nitrogen was extracted by distilling the ammonia and collecting the distillate in a 0.1 N sulfuric acid solution. The amount of nitrogen in the condenser flask was determined by titrating the ammonia with a 0.1 N sodium hydroxide solution in the presence of a methyl red indicator and 0.1 N sulfuric acid. Finally, we used Equation (5), according to Mibulo et al. [21], to calculate the amount of nitrogen present.

$\%N=\frac{\left(V_1-V_0\right)\times c\times f\times 0.014}{m\times 100}$ (5)

where:

• %N: Total Kjeldahl nitrogen content.

• V₀: volume of sulfuric acid consumed during the blank titration (mL).

• V₁: volume of sulfuric acid consumed during the titration of the sample (mL).

• c: normality of the acid (mg/L).

• f: acid factor;

• m: Mass of the sample (g).

2.3. Data Analysis

The data collected during immersion in the slaughterhouse allowed for a detailed analysis of the average masses of rumen contents, which were then compared across days. In addition to these masses, the physicochemical parameters of the rumen samples collected daily were analyzed. Since the data were normally distributed, an ANOVA test (T test) was applied to compare results from one day to the next and identify significant variations in measurements over time. These comparisons were performed using R software, with a significance threshold set at 5%.

Narrative information regarding the state of the slaughterhouse environment is presented alongside photographic illustrations. The images were taken during on-site visits and accurately reflect the observed conditions. This visual and narrative approach aims to provide a clear, detailed understanding of the environmental conditions at the slaughterhouse to facilitate an assessment of the observed issues and practices.

The total annual rumen yield at the Man City slaughterhouse was estimated based on the average rumen mass (ARM) obtained during weigh-ins. This estimate is based on the approximate total number of cattle slaughtered each year. This figure is derived from the average number of cattle slaughtered on ordinary days and holidays, such as Christmas, New Year’s Day, Eid al-Fitr, and the day after Eid al-Adha. The formula for calculating the approximate rumen mass is expressed by mathematical Equations (6) and (7), which are as follows:

$\text{ARM}=\text{CSY}\times \text{RMC}$ (6)

where:

• ARM: the average annual rumen mass.

• CSY: the average number of cattle slaughtered per year.

• RMC: the average rumen mass per head of cattle.

And,

$\text{CSY}=361\times \text{CSOD}+\text{CSCD}+\text{CSNYD}+\text{CSEFD}+\text{CSDA}$ (7)

where:

• CSOD: the average number of cattle slaughtered on an ordinary day.

• CSCD: the average number of cattle slaughtered on Christmas Day.

• CSNYD: the average number of cattle slaughtered on New Year’s Day.

• CSEFD: the average number of cattle slaughtered on Eid al-Fitr Day, and

• CSDA: the average number of cattle slaughtered the day after Eid al-Adha.

This approach provides an estimate based on measurable and observed data, thereby facilitating waste management in the slaughter industry, as well as the use of these products in other sectors.

The theorical volume of biomethane that this annual rumen waste production could generate was calculated using the relationship for biomethane production potential (BPP) of bovine rumen described by Coulibaly et al. [22] in Equation (8):

$\text{BPP}\left({\text{m}}^3\right)=\text{ARM}\times \text{\%VOM}\times \text{\%DM}\times \text{Ip}$ (8)

where

• Ip: the productivity index, which is estimated at 2.52 m³ CH₄/kg VS, according to Barros et al. [23].

• %VOM: Average volatile matter content of rumen waste from the Man City slaughterhouse.

• %DM: Average dry matter content of rumen waste from the Man City slaughterhouse.

Thus, no biochemical methane potential tests were performed on the Man samples.

3. Results

3.1. Environment of the Municipal Slaughterhouse in Man

The killing space of the Man municipal slaughterhouse is around 40 meters wide and 50 meters long (Figure 2(a) & Figure 2(b)). In this location, cattle carcasses and rumen waste are not managed properly. A pressurized pipe is used to flush rumen waste into the Koh River (Figure 2(c) and Figure 2(d)). The river is the city’s primary source of surface water. Additionally, the carcass waste produced by the cattle slaughtering process is dumped behind the slaughtering area at the back of the slaughterhouse once the skins are removed in the basic processing area (Figure 2(e)).

Figure 2. View of the sections of the municipal slaughterhouse in the city of Man. (a) = slaughter area; (b) = discharge pipe for rumen waste; (c) = rumen waste transported to the Koh River; (d) = point where waste from the slaughterhouse enters the Koh River; (e) = pile of carcasses disposed of behind the slaughter area.

3.2. Statistics on Cattle Slaughter at the Man Slaughterhouse

The on-site visit to the Man slaughterhouse revealed that the daily range of cattle slaughtered was 18 to 24, with an average of 21 per day. Figure 3 illustrates this observation. However, interviews with the managers revealed that the highest number of cattle are slaughtered during holidays. These include Christmas, New Year’s Day, Eid al-Fitr Day, and the day after Eid al-Adha (see Table 1). The average number of cattle slaughtered is 35 on Christmas Day, 39 on New Year’s Day, 43 during Eid al-Fitr Day, and 42 the day after Eid al-Adha. Data concerning the average number of cattle slaughtered is sourced from records that are meticulously kept by the managers of slaughterhouses.

Figure 3. Number of cattle slaughtered each day during the slaughterhouse immersion period in the city of Man.

Table 1. Peaks in cattle slaughter at the man slaughterhouse over two consecutive years.

3.3. Rumen Content Mass of Cattle

Rumen content weighing operations at the Man slaughterhouse showed variation in masses measured per day throughout the week (see Table 2). The daily average ranged from 19.8 to 28.5 kg over the entire weighing period. This results in a consolidated average of approximately 25.9 kg of rumen contents. However, the daily weighing averages are of the same order of magnitude, except for the average obtained on the second day, which is 19.8 kg (T-test; p > 0.05).

Table 2. Rumen content mass measured in cattle slaughtered at the Man. slaughterhouse. Values within the same row that are followed by the same letter (e.g., a, b, c) do not differ significantly at a significance level of p < 0.05.

3.4. Physicochemical Characteristics of the Rumen

Analyses of the physicochemical parameters of rumen samples collected at the Man slaughterhouse during the immersion period reveal that the daily mean values of the parameters do not differ significantly (p > 0.05) (see Table 3). The pH ranged from 6.5 to 7.4, with an overall mean of 6.9 ± 0.4. The moisture content ranged from 81.5% to 85.5%, and the dry matter content ranged from 14.5% to 18.5%. Volatile matter accounted for 86.8% to 89.3% of daily samples on average (88.1%). The carbon and nitrogen levels were between 49.9% and 51.3% (average 50.6%) and between 3.4% and 3.6% (average 3.5%), respectively. These levels resulted in a carbon-to-nitrogen ratio ranging from 14 to 15, averaging 14.5.

Table 3. Physicochemical characteristics of the rumen at the Man slaughterhouse. Values within the same row that are followed by the same letter (e.g., a, b, c) do not differ significantly at a significance level of p < 0.05.

3.5. Theorical Biomethane Production Potential of Beef Rumen Waste from the Man Slaughterhouse

Estimates of the theorical biomethane potential of rumen waste produced at the Man slaughterhouse indicate a high annual production of 66683.01 m³ (Table 4). Daily production values vary by day, reaching 180.92 m³ on regular days, 301.54 m³ on Christmas Day, 336.00 m³ on New Year’s Day, 370.46 m³ during Eid al-Fitr Day, and 361.85 m³ on the days following Eid al-Adha.

Table 4. Theorical biomethane potential of rumen waste produced at the Man slaughterhouse. NMB: average number of cattle slaughtered, ARM: average mass of cattle rumen content, %DM: dry matter content, %VOM: volatile organic matter, Ip: productivity index.

4. Discussion

The visit to the slaughterhouse in Man revealed an absence of a structured waste management process. This situation poses a significant environmental risk, primarily due to the disposal of carcasses behind the slaughtering area and the direct discharge of organic waste into the city’s main waterway. This poor waste management raises significant environmental and public health concerns and poses potential risks to aquatic resources and the safety of residents, as Zahui et al. [17] observed in this same river. Rumen contents consist of partially digested plant matter that is rich in water, biodegradable organic matter, nitrogen, and microorganisms. Without proper collection, storage, and treatment, they become a significant source of environmental and health pollution [24]. Paradoxically, rumen waste is a valuable resource rather than mere waste. Scientific studies have shown that rumen contents can be anaerobically digested alone or with other slaughterhouse waste. This process reduces pollution, produces renewable energy, and creates a digestate that can be used as an organic fertilizer [25].

Observation of slaughterhouse activities during the immersion period revealed significant figures regarding the number of cattle slaughtered. On average, the slaughterhouse processes between 18 and 24 cattle daily, with a steady average of 21 cattle per day. However, interviews with managers highlighted significant fluctuations during holiday periods. Christmas Day, New Year’s Day, Eid al-Fitr Day, and the day after Eid al-Adha show peaks in slaughter activity. The number of cattle slaughtered reaches 35 on Christmas Day, 39 on New Year’s Day, 43 during Eid al-Fitr Day, and 42 on the day after Eid al-Adha. These figures underscore the impact of cultural traditions and celebrations on slaughterhouse activity, revealing a seasonal pattern that may influence operations and resource management [26]. The observation of increased animal slaughter on the day after Eid al-Adha rather than on the holiday itself is explained by the Muslim tradition of sacrifice, which primarily takes place on that day. During Eid al-Adha, also known as Eid al-Kabir or the Feast of the Sacrifice, most of the consumed meat comes from family sacrifices. This ritual commemorates the sacrifice of Ibrahim (Abraham) and leads to a temporary pause in slaughterhouse operations [27]. However, starting the day after the festival, demand for meat increases significantly for several reasons. First, households that did not participate in the sacrifice—that is, those that did not slaughter an animal—seek to purchase meat through formal channels. Second, food service establishments, such as restaurants and hotels, must restock their meat reserves to meet customer demand [28].

Weighing the contents of the rumen at a slaughterhouse revealed non-significant differences in measured masses throughout the week. The results indicate that the daily average weight fluctuates between 19.8 kg and 28.5 kg, with a consolidated average of 25.9 kg. With the exception of the second day, which recorded a value of 19.8 kg, the other daily averages tend to be consistent, suggesting that the slaughtered cattle are similar in size. This consistency in weights indicates small variation in weight among animals, which contributes to consistency in slaughter operations [29]. However, the low weight on the second day may be due to farmers occasionally slaughtering heifers for economic reasons because raising heifers is considered unprofitable [30]. It is also important to note that the average weight observed in this study is lower than those measured in Cotonou and the slaughter areas of Porto-Novo and Abomey-Calavi in Benin [31]. This difference could be attributed to various livestock feeding practices, which highlights the potential impact of husbandry practices on animal weight at slaughter [29].

Analyses of the physicochemical parameters of rumen samples collected at the Man slaughterhouse reveal that the daily mean values do not show significant differences, with a p-value greater than 0.05. The rumen pH, generally close to neutral, ranges between 6.5 and 7.4, with an average of 6.9, consistent with the studies by Mutisi et al. [32]. This value is optimal for anaerobic digestion, which is indicated to be between 6.5 and 8.5 according to Moletta [33]. The near-neutral pH is linked to the physiological function of the rumen, which is a fermentation medium, highlighting a significant technical and economic advantage, as the rumen can be directly introduced into the digester without requiring pH adjustment, unlike other substrates [34]. The samples also exhibit a high moisture content of 81.5% to 85.5% (mean 84.1% ± 1.2%), corresponding to a relatively low dry matter content (14.5% to 18.5%, mean 15.9% ± 1.2%). These observations are corroborated by Selormey et al. [35], who report a dry matter content of approximately 15.06% ± 1.72% in ruminal contents. This high water content is essential for the hydration of feed particles and the functioning of the microorganisms responsible for the degradation of organic matter [36]. In wet anaerobic digestion systems, a dry matter content below 15% is typically sought to ensure effective mixing and prevent clogging [37]. Regarding volatile matter, the samples show a high content ranging from 86.8% to 89.3% (average of 88.1%), confirming a high richness in fermentable organic compounds, a key indicator of a substrate’s methanogenic potential [38]. This rate is corroborated by Selormey et al. [35], who reported a volatile matter content of 87.35% ± 5.52%. The high availability of volatile matter in the rumen, consisting of partially digested plant residues, volatile fatty acids, and microorganisms, presents an opportunity for biogas production through anaerobic digestion [36].

The analyzed samples reveal carbon and nitrogen levels that vary little, ranging from 49.9% to 51.3% (average of 50.6%) for carbon and from 3.4% to 3.6% (average of 3.5%) for nitrogen. The carbon-to-nitrogen (C/N) ratios range from 14 to 15, averaging 14.5. However, these ratios fall short of the recommended range of 20 to 30 for promoting anaerobic digestion, as indicated by Rajlakshmi et al. [39] and Zainudeen et al. [40]. Low C/N ratios indicate high nitrogen concentrations, which can lead to ammonia inhibition, as noted by Ihoeghian et al. [41]. However, Sittijunda [42] suggests co-digestion as a solution to rebalance the C/N ratio of substrates. Therefore, biogas conversion of rumen waste from the Man municipal slaughterhouse requires co-digestion with a carbon-richer substrate to optimize the C/N ratio. However, these results are inconsistent with those of Selormey et al. [35] and Mutisi et al. [32], who reported C/N values of 20.81 ± 3.96 and 23.5 ± 0.820, respectively. This discrepancy may be related to different livestock feeding regimens, which highlight the significant influence of diet on rumen content characteristics, as indicated by Zhang et al. [43].

Co-digestion using carbon-rich substrates in a local context in Côte d’Ivoire could involve cocoa shells, fruit and vegetable waste from markets, as well as certain food crop residues [44]. However, before being introduced into digesters, rumen waste requires pretreatment to optimize its biodegradability and ensure the system functions properly. These pretreatment steps are essential to ensure maximum efficiency in the anaerobic digestion process, which may include grinding, sorting, homogenization, or other methods aimed at improving the decomposition of organic materials. Paying close attention to these steps will help maximize biogas production and reduce the environmental impacts of organic waste [45].

The assessment of the theoretical biogas potential from the rumen waste of the Man slaughterhouse estimates an annual production of approximately 66683.01 m³. Daily production levels vary significantly throughout the year, with ordinary days averaging around 180.92 m³. Notably higher production occurs on specific occasions: 301.54 m³ on Christmas, 336.00 m³ on New Year’s, 370.46 m³ during Eid al-Fitr, and 361.85 m³ on the day following Eid al-Adha. This variation indicates that rumen waste can be an effective substrate for biogas production, particularly through anaerobic digestion, as supported by research from Klintenberg et al. [46]. However, it is important to note that no biochemical methane potential tests were conducted on the specific samples from the Man slaughterhouse. Thus, while the potential for biogas production appears robust based on the estimated volumes, further testing on the methane potential of these samples would be beneficial for more comprehensive insights.

5. Conclusions

An investigation at the municipal slaughterhouse in Man revealed inadequate waste management, resulting in significant environmental issues, including the discharge of organic waste into the city’s primary waterway, the Koh River, and the accumulation of carcasses.

The slaughterhouse generates an average of 25.90 kg of rumen content waste per cow and slaughters an average of 21 cows per day, 35 on Christmas Day, 39 on New Year’s Day, 43 during Eid al-Fitr day, and 42 the day after Eid al-Adha. Analysis of this waste revealed favorable physicochemical characteristics for methanization: an optimal pH, high volatile matter content, a low C/N ratio (which could be improved through co-digestion), and a suitable moisture content for wet anaerobic digestion. Furthermore, recovering rumen waste from the slaughterhouse could produce up to 66683.01 m³ of biomethane per year.

However, the current management of slaughterhouse waste poses risks to public health and the aquatic environment. Rumen contents are rich in biodegradable matter and could be valorized through anaerobic digestion. Therefore, biogas conversion of rumen waste from the Man municipal slaughterhouse requires co-digestion with a carbon-richer substrate to optimize the C/N ratio. This process would contribute to pollution reduction and the production of renewable energy.

Acknowledgements

The authors would like to express their gratitude to the Central Laboratory at the University of Man and to the laboratory at the Félix Houphouët-Boigny Polytechnic Institute in Yamoussoukro for their support. They would also like to thank the management of the Man slaughterhouse for their collaboration and invaluable assistance in collecting field data.

Conflicts of Interest

The authors declare no conflicts of interest regarding the publication of this paper.

References