Effects of Palm Oil Processing Waste on Soil Microorganisms

Introduction

Oil palm, (Elaeis guineensis) African tree in the palm family (Arecaceae), cultivated as a source of oil. The oil palm is grown in West and Central Africa, as well as in Malaysia and Indonesia. Palm oil, obtained from the fruits, is used in making soaps, cosmetics, candles, biofuels, and lubricating greases and in processing tinplate and coating iron plates. Palm kernel oil, from the seeds, is used in manufacturing such edible products as margarine, chocolate confections, cookies, and bread, as well as many pharmaceuticals. The cake residue after kernel oil is extracted is use as cattle feed. The plant is also grown as an ornamental in many subtropical areas [1]. The global production of palm oil is increasing rapidly, which is leading to an increase in waste from palm oil mills. This waste is causing significant environmental problems [2]. Soil is the key component of natural ecosystem [3], and as such environmental sustainability depends largely on a sustainable soil ecosystem. Soil can be defined as a dynamic, living ecosystem that performs a variety of functions, including supplying nutrients and water to plants, storing and cycling carbon and other elements, and providing habitat for a vast array of microorganisms and invertebrates.

The soil is composed of five components: minerals, water, soil air, organic matter and soil living organisms. Due to its chemical composition and physical properties soil form a habitat for larger amounts of microorganisms and other living organisms [4]. Microorganisms found in the soil include bacteria, algae, fungi, actinomycetes, protozoa and viruses, but bacteria are the most abundant of all soil microorganisms. They are characterized by high metabolic activity. Most soil bacteria are characterized by the ability to adhere to surfaces of the mineral molecules and to the soil colloids [5].

While human industrial and economic activities have improved living standards in many ways, they have also led to increased waste production. This waste is often disposed of on land, which can disrupt the natural ecological balance and pose a threat to human health and the survival of microorganisms in the environment [6]. Palm oil processing waste (POPW) is one of the major most problematic environmental pollution potentials among wastes [7]. It has the residual liquid waste product obtained after the extraction of oil from the fruits of the oil palm. It consists of the liquid effluent arising from the sterilization of the fruits (the sterilizer condensate) and the sludge effluent (clarification sludge) arising from the maceration of the fruit mesocarp and subsequent decantation/clarification of the oil. Various methods have been proposed for disposing of palm oil waste, including both traditional and innovative solutions [3]. Some methods of palm oil waste disposal include channeling the waste into ditches, landfills, and streams and rivers, or simply discharging it onto open land. However, these methods can have negative environmental and health impacts. In Nigeria, palm oil extraction is often carried out by small-scale farmers using semi-mechanized methods. This results in the production of large amounts of waste, which is often dumped on nearby land without any further processing [8]. When the palm oil waste has accumulated considerably in the area due to continued deposit, the site is abandoned and a fresh site is located. The negative environmental effects of palm oil waste being discharged into streams have been well documented. However, the impact of palm oil waste on soil microorganisms has not been studied in depth. This is an important issue that needs to be addressed, as soil microorganisms play a vital role in maintaining soil health and fertility [9]. The aim of this research is to determine the effect of Palm oil processing waste on soil microorganisms.

Results

This study was carried out to assess the effect of palm oil processing waste on soil Microorganisms. Table 4.1 shows the physicochemical parameters of both the control soil and three samples from three locations. It shows that the pH of the soil decrease compared to the control soil. The moisture content or water holding capacity of the soil samples increased compared to the control while there was a rise in temperature of the soil samples compared to the control soil. Table 4.2 shows that there was a decrease in the total colony count and total viable count of microorganisms in the sample soil compared to the control soil. There was also a decrease in the total Fungi count of sample soil compared to the control soil, though the decrease was not as high as that of the total bacteria count. Table 4.3 presents the Cultural, morphological and Biochemical characteristics of Bacteria and identification of these organisms. Bacteria suspect to be present were E.coli, Klebsiella spp_, Proteus_ spp_, Staphylococcus_ spp_, Bacillus_ spp_, and _Shigella spp. Presented on Table 4.4 is the Microscopic and macroscopic characteristics of fungi. This table presented both macroscopic and microscopic features of fungi and the probable fungi. The fungi suspected were Mucor spp, Rhizopus spp, and Aspergillus spp. Table 4.5 shows the percentage prevalence of bacteria isolated with klebsiella having the highest prevalence while Table 4.6 shows the prevalence of fungi with Rhizopus spp and Aspergillus spp being the most prevalent.

Discussion

In this study, it was observed that there was a decrease in pH of the polluted soil samples compared to the control soil sample (pH decrease from 6.30 ±0.00 to 5.33 ±0.434 mean of pH from the three sites). The decrease in pH is associated with decay of organic matter in soil Palm oil processing waste (POPW) which alters the pH. This is in agreement with the work of Ong HKA, et al. [13] who opined that one major effect of palm oil processing waste on soil is the decrease in soil pH. It was also observed that there was rise in temperature in soil samples polluted with POPW compared to the control soil sample (a rise in temperature from 27.95 ±0.212 in control sample to 28.96 ±0.188 in the mean of samples from the three sites). This agrees with the study of Chin MS, et al. [14] which concluded that microbial decomposition of organic compounds in Palm oil processing waste releases heat as a byproduct, causing a temperature rise in the soil. It was also observed that there was an increase in moisture content of soil polluted by palm oil processing waste might be as a result of much organic matter present in POPW. This is in agreement with the work of Ong HKA, et al. [13].

Soil samples impacted with palm oil processing waste (POPW) yielded low microbial population and diversity when compared to soil samples without POPW. This is in agreement with work of Oyeleke SB, et al. [15]. He observed that there was a decrease of bacteria isolates in soil impacted with POPW which could be due to high organic content, which can lead to oxygen depletion and create unfavorable conditions for many soil microorganisms. This may disrupt the soil microbial community and impact overall soil health. The total Fungi count also dropped, but the effect was not as much as that of bacteria (a decrease from 44.33 ±1.527 to 28.88 ±2.590 mean of the three samples). This may likely be due to the fact that soil fungi may exhibit ability to break down tough organic matter and have resilience or adaptation mechanisms that mitigate the negative effects of POPW, leading to a perceived lesser impact. This aligns with the findings of Smith JL, et al. [16] but contradicts the study by Yeoh BG, et al. [17], which asserts that POPW leads to an elevation in soil fungi abundance.

Six Bacteria and three fungi were isolated from three samples in three different locations. They include (Bacteria) Klebsiella, Proteus, Staphylococcus, Bacillus, Shigella spp and E.coli. (Fungi) Mucor spp_, Rhizopus_ spp_, and _Aspergillus spp which is in agreement with the work carried by Ong HKA, et al. [13] who isolated similar organisms. Klebsiella spp (33.33%) prominence suggests a significant presence in the studied samples, possibly indicating its adaptability or prevalence in the environment under investigation. The coexistence of Staphylococcus spp (25%) and Proteus spp (16.67%) highlights microbial diversity within the sample. Staphylococcus spp, known for its versatility, may contribute to this diversity alongside Proteus spp, indicating varied microbial sources. The comparable percentages of Bacillus spp (8.33%), Shigella spp (8.33%), and E. coli (8.33%) suggest a balanced distribution among these isolates. This is agreement with the findings of Orji MU, et al. [18]. This equilibrium may signify a dynamic microbial community, influenced by factors such as environmental conditions or host interactions. Staphylococcus spp and Klebsiella spp, with higher prevalence, raise concerns about potential health risks, considering their pathogenic nature. This warrants further investigation into the specific strains present and their associated virulence factors.

Conclusion

The examination of palm oil processing waste impact on soil microbial communities revealed significant consequences of palm oil processing waste on soil microorganisms. It was observed that there were significant differences in the determined soil physicochemical parameters of polluted soils when compared to the control sample. There were reduction in microbial population and diversity in soil samples impacted with palm oil processing waste (POPW) yield when compared to soil samples without POPW. Inadequate management could pose a substantial threat, as the persistent use of palm oil processing waste may induce alterations that negatively impact soil micro biota and subsequently soil fertility. This could result in diminished agricultural yields when the effluent is improperly disposed of on farmlands.

Recommendation

Based on the results of the findings, the following recommendations were made;

1. Implement a long-term monitoring strategy to capture changes in soil microbial communities over time, providing a more comprehensive understanding of the sustained effects of palm oil processing waste (POPW).
2. Formulate clear policy recommendations based on the study findings, aiming to guide government initiatives in regulating and managing the disposal of POPW to minimize environmental and agricultural impacts.
3. Develop and implement public awareness campaigns to educate farmers, industries, and the general public about the potential hazards of improper POPW disposal and the importance of adopting responsible waste management practices.