Introduction
The long-term health and sustainability of natural ecosystems and food production systems are heavily dependent on sustainable human practices like agriculture. The rise in global populations over the last few decades has prompted an increase in agricultural production. Consequently, humans have resorted to the use of chemical substances such as fertilizers, pesticides, and herbicides as well as genetically modified species to increase food production. However, Bux et al. (2022) point out that while conventional fertilizers significantly enhance the volumes of production, their use in agriculture presents significant environmental challenges including climate change, loss of biodiversity, soil degradation, and water pollution. In the Mediterranean areas for example, a study by Hernández et al. (2016) found that the intensive use of nitrate-based chemical fertilizers causes the contamination of superficial and ground waters while also damaging the overall health of the soil. These findings indicate that relying on conventional fertilizers for agricultural production is detrimental to environmental sustainability. Therefore, there is a need to adopt more sustainable measures for increasing agricultural production. Yoshikawa et al. (2021) believe that organic wastes, also referred to as composed manure, provide a viable alternative by increasing soil productivity while also ensuring sustainability.
This study critically assesses the benefits of using composed manure as a sustainable substitute for chemical fertilizers. The study aims to contribute to the ongoing evaluation of the potential of organic materials in correcting the environmental effects that result from using inorganic chemicals in agricultural production. For man to ensure continued food production while also protecting the environment from degradation, it is essential to shift from using conventional fertilizers to more eco-friendly organic fertilizers.
Background
The increased use of chemical fertilizers has resulted in a corresponding increase in food production and environmental degradation in equal measures. Bux et al. (2022) link the widespread application of chemical fertilizers to deteriorating soil quality, underground water pollution, and the overall decline in ecosystem health. The negative influence of these compounds results from adverse phenomena like erosion and runoff into nearby waterbodies or seepage into underground water. Moreover, the manufacturing process of conventional fertilizers is often energy-intensive, furthering their unsustainability (Hernandez et al., 2016). These concerns have heightened the need for eco-friendly alternatives to conventional fertilizers, hence the growing exploration of bio-solids as a more sustainable alternative. In addition, the synthesis of conventional fertilizers involves the release of harmful greenhouse gases like Carbon Dioxide, Nitrous Oxide, and Methane, thereby significantly contributing to global warming and by extension, climate change (Hashimi et al., 2020). Following the need to align agricultural production to environmentally sustainable approaches, the environmental impacts of conventional fertilizers underscore the need to move with speed in exploring eco-friendly alternatives.
Pahalvi et al. (2021): Chemical fertilizers and their impact on soil health
On the other hand, Obi-Njoku et al. (2022) believe that adopting the use of bio-solids in food production is a sustainable strategy, increasing food production without compromising environmental health. Organic fertilizers are obtained from organic sources including animal wastes, plant remains, and compost, which offer an opportunity to recycle them back into the soil. By recycling organic waste and using it in agriculture, Guo et al. (2019) and Montalba et al. (2010) believe that soil microbial activity can significantly improve thereby enhancing the soil structure and ensuring the overall health of the soil. Furthermore, Hernandez et al. (2016) underscore the significance of using organic waste in food production due to its contribution to the circular economy and environmental sustainability. This critical assessment analyses the environmental significance and practical concerns of using organic matter in food production to inform sustainable agriculture by exploring the environmental consequences of conventional fertilizers and the benefits of using bio-solids in agriculture.
Literature Review
Since the turn of the 21st century, different studies have focused on the impacts of conventional fertilizers on environmental health and the need to shift to more sustainable alternatives. A 2021 study by Boudjabi and Chenchouni identifies sewage sludge as a sustainable alternative to conventional fertilizers, underlining that it increases crop yield while maintaining soil quality. Similarly, an experimental study by Hashimi et al. (2020) compares the results of using organic and conventional fertilizers in producing rice and wheat by examining their greenhouse effect and contributions to soul health. While the use of conventional fertilizers leads to higher yields in the short term, they significantly degrade soil quality as opposed to bio-solids and other organic matter (Hashimi et al., 2020). Tuomisto et al. (2012) add to this discussion by comparing the global warming and energy consumption levels of organic and inorganic farming. Due to the release of greenhouse gases during the synthesis of fertilizers, conventional farming significantly contributes to global warming (Tuomisto et al., 2012). Therefore, it is important to adopt agricultural practices that combine increased crop yield and improved soil fertility.
In addition, various studies highlight the need to integrate the use of bio-solids into farming practices to maintain environmental health. A review by Marchuk et al., (2023) establishes that the use of bio-solids obtained from municipal wastewater sludge in agricultural production significantly increases soil fertility and maintains soil quality. Similarly, Guo et al. (2019) observe that the use of organic wastes enhances soil ecology by improving microbial activities. Increased microbial activity increases nutrient production, improving soil fertility. On the other hand, the use of conventional fertilizers adversely impacts soil microbial colonies, degrading soil quality (Damodaran et al., 2016). Moreover, Maltas et al. (2018) observe that using organic wastes on a farm is vital for carbon sequestration. Increasing soil organic matter lowers atmospheric carbon, which is an important step in combating climate change. Further, a study by Kizito et al. (2019) identifies the use of nutrient-enriched biochar, a carbon-rich charcoal made from biomass, as an environmentally sustainable agricultural approach that also enhances crop productivity.
However, with the continued advancement in technology, future studies need to explore how technological solutions can be integrated into agriculture to enhance production while maintaining soil quality. While technology has been in use in the production of conventional fertilizers, it is vital to figure out how it can contribute to the processing of organic wastes to produce bio-solids that not only enhance productivity but also ensure soil health.
Advantages of Organic Wastes
Applying organic wastes to land used for food production is associated with such advantages as enhancing soil nutrient content, improving soil health, safeguarding the environment, contributing to carbon sequestration, and improving soil water-holding capacity.
Nutrient Content
A 15-year study by Liang et al. (2011) establishes that applying farmyard manure (FYM) significantly increases the concentrations of soil organic carbon (SOC) and total nitrogen in the soil, thereby improving crop yield. Similarly, by increasing the SOC, organic matter enhances the activity of microbial communities, which are pivotal for nutrient cycling (He et al., 2023). Furthermore, Boudjabi and Chenchouni (2021) argue that organic wastes like sewage sludge contain vital elements like phosphorus and nitrogen which are essential for crop production. Thus, if used in agricultural land, organic wastes significantly improve soil nutrient content.
Liang et al. (2011): Effects of Farmyard Manure (FYM) and Inorganic Fertilizers (INF) on crop yield
Soil Health
The application of FYM enhances various fractions of SOC such as microbial biomass carbon (MBC), particulate organic carbon (POC), and dissolved organic carbon (DOC), which are significant aspects of establishing soil health (Liang et al., 2011). In addition, organic wastes enhance the abundance and function of soil micro-organisms, improving soil health and promoting plant resilience (Maffei et al., 2019; Mukherjee et al., 2020; Guo et al., 2019). Further, when added to the soil, organic matter balances soil pH and electrical conductivity (Islam et al., 2017), ensuring a safe habitat for microbial communities and improving productivity. Hence, organic farming enhances soil health, leading to long-term and improved productivity.
Liang et al., (2011): Comparative contributions of FYM and INF to soil carbon fractions
Environmental Benefits
The incorporation of bio-solids in agriculture not only improves food production but also contributes significantly to the long-term sustainability of the soil. The use of inorganic fertilizers not only impacts soil quality by impacting microbial activity (Liang et al., 2011) but also lowers the quality of ground and surface water (Ganesh et al., 2011). Therefore, organic wastes offer a safe and sustainable alternative that ensures clean agricultural production (Case et al., 2017). In addition, Hashimi et al. (2020) identify that using inorganic fertilizers in agricultural production releases harmful greenhouse gases such as carbon dioxide, methane, and nitrous oxide, which result in global warming. On the contrary, organic wastes have the potential to remove greenhouse gases like carbon dioxide from the atmosphere through carbon sequestration (Hashimi et al., 2020; Liang et al., 2011; and Maltas et al., 2018). However, while organic wastes have significant contributions to environmental sustainability, Harley-Nyang et al. (2022) advise caution when using bio-solids and sewage sludge as the presence of microplastics may present harm to terrestrial environments. Finally, organic waste significantly contributes to soil physical attributes like improving soil structure (Liang et al., 2011) and preventing soil erosion thereby preventing soil degradation. The figure below illustrates how conventional fertilizers contribute to environmental pollution.
Source: https://farmerline.co/the-impact-of-fertilizers-on-the-environment-inorganic-vs-organic/
Carbon Sequestration
A long-term (42 years) study by Krause et al. (2022) reveals that composting and using organic matter in farmlands significantly increases the levels of soil organic carbon (SOC). Plants absorb carbon dioxide from the atmosphere during photosynthesis and convert it into organic carbons. SOC level is a true measure of healthy soil as it determines nutrient adsorption and desorption, water retention ability, and habitat quality for microbial communities (He et al., 2023). Therefore, organic wastes are essential for agents of carbon sequestration and improvement of soil quality (Liang et al. 2011) while also regulating atmospheric carbon levels. On the other hand, using conventional fertilizers does not increase SOC (Liang et al., 2011) and thus does not improve soil quality in the long run. Further, the manufacture of inorganic fertilizers, through processes like the Haber-Bosch process is often associated with the emission of significant volumes of carbon dioxide into the atmosphere, resulting in climate change.
Source: https://biochar.co.uk/soil-carbon-sequestration/
Improved Water Retention
He at el. (2023) explain that the increase in soil organic matter (SOM) directly improves the soil water retention capacity. According to Bhadha et al. (2017), “every 1% increase in soil OM will help soils hold up to 20,000 gallons more water per acre.” Therefore, organic farming suits both irrigation and rain-fed farming.
Challenges and Limitations
While the organic farming system remains the most environmentally sustainable alternative to conventional fertilizers, it is not without its limitations.
Nutrient Variability
Despite vouching for organic farming, Mukherjee et al. (2020) point out that nutrient content variability associated with organic waste makes it difficult for farmers to achieve the correct application rate. Prolonged uneven distribution may result in nutrient imbalances. Further, Maffei et al.’s (2019) investigation on lettuce farming in Sao Paulo establishes that farmers need to carefully understand the nutrient dynamics in organic material to realise maximum effect. Despite the nutrient inconsistency, organic wastes improve soil quality and prevent degradation.
Application Logistics
The large-scale agricultural application of organic matter may present a challenge to farmers. An exploration of farmer perceptions by Case et al. (2017) reveals farmers’ concerns regarding the application process. In addition, Pellervo et al. (2013) explain that organic fertilizers are often required in large volumes per given area of land compared to conventional fertilizers, presenting transportation and storage challenges. Moreover, special farm equipment may be required to effectively apply organic wastes on farms. Thus, most farmers may be discouraged from adopting organic farming systems due to logistic challenges.
Potential Risks
While organic wastes enhance environmental sustainability compared to chemical fertilizers, it is still essential to understand the risks that such wastes may pose to the environment. The investigation by Harley-Nyang et al. (2022) reveals that the presence of microplastics in organic wastes such as sewage sludge and bio-solids may contaminate terrestrial environments, presenting health risks to humans and other animals. In addition, some pathogen and weed-infected waste may be resistant enough to withstand the composting process thereby transmitting pathogens and weeds onto the farm (Parvaze and Kumar, 2019). Finally, composting pits are associated with unpleasant odours, causing air pollution in the neighbourhood. Therefore, it is vital to assess the potential risks of organic wastes before application as fertilizers.
Comparative Analysis
Achieving environmental sustainability requires the adoption of the most environmentally friendly agricultural practices. Hence, it is vital to compare the contributions of organic and inorganic fertilizers to sustainability. To begin, unlike conventional fertilizers, organic wastes enhance soil health by promoting the activity of microbial communities (Montalba et al., 2010). Inorganic fertilizers, on the other hand, hamper the activity of microorganisms and disrupt soil biodiversity (Maffei et al., 2019). Secondly, Mukherjee et al. (2020) highlight that due to bioaccumulation and biomagnification, chemicals used in conventional fertilizers, herbicides and pesticides may end up in human systems, presenting serious health risks. However, these fears are eliminated when organic wastes are used in crop production as they are free from contaminants (Mukherjee et al., 2020). Third, while organic wastes play a significant role in lowering greenhouse gas levels in the atmosphere, conventional fertilizers release more greenhouse gases into the atmosphere (Tuomisto et al., 2012). The manufacture of chemical fertilizers involves the burning of fossil fuels which releases carbon, a greenhouse gas into the atmosphere. Similarly, the synthesis of inorganic fertilizers often releases harmful gases like nitrous oxide and methane, thus speeding up global warming (Tuomisto et al., 2012). On the contrary, organic matter reduces carbon dioxide levels in the atmosphere through sequestration thereby helping to mitigate the impacts of greenhouse gases (Maltas et al., 2018). Therefore, agricultural use of organic matter ensures human and soil health while also safeguarding atmospheric quality.
In addition, using organic wastes in agriculture is known to preserve groundwater quality. On the other hand, conventional fertilizer-based agriculture is associated with increased contamination of ground and surface water (Ganesh et al., 2011; Khan et al., 2018). Toxic chemicals from inorganic fertilizers are often seeped into groundwater or carried by runoffs into surface waters (Khan et al., 2018). These chemicals degrade water quality. Presenting potential health risks. Finally, in addition to ensuring soil, water, and air quality, and conserving biodiversity, the use of organic wastes in agriculture also contributes to long-term environmental sustainability by reducing the use of non-renewable sources. Since the manufacture of agrochemicals involves the burning of large quantities of fossil fuels, replacing agrochemicals with organic material means a shift from using non-renewable energy sources. Therefore, using organic wastes in food production is a sustainable alternative to the use of conventional fertilizers.
Real-World Case Studies
Food security is a critical issue in the contemporary world with people with most people prioritizing increased output at the expense of environmental sustainability. However, various real-world scenarios demonstrate the possibility of maintaining high agricultural production while still ensuring environmental health. In 2016 Hernandez et al. experimented in Brebes, Indonesia to compare the impact of organic and conventional fertilizers on Lactuca sativa L. The main focus was on soil health and crop yield. Hernandez et al. (2016) established that organic matter not only increased crop yield but also enhanced the health of the crop, increased microbial activity, and ensured optimal soil pH. Similarly, in 2017, Mymensingh, Bangladesh, Islam et al. experimentally compared the impact of using organic and inorganic fertilizers in the production of Tomatoes. After conducting field trials at the Bangladesh Agricultural University (BAU), Islam et al. (2017) established that in addition to enhancing soil quality, using organic material in tomato production ensured better quality tomatoes.
In North China Plain, Liang et al. conducted a 15-year experiment to establish the influence of both organic wastes and conventional fertilizers on SOC and total nitrogen (TN) concentrations. Their experiment established that using FYM significantly increased the concentrations of SOC and TN while applying INF had no recognizable increase in either SOC or liable carbon (Liang et al., 2011). This indicates that organic wastes are vital in carbon sequestration as opposed to INF, thereby improving soil quality and purifying atmospheric air. In addition, Guo et al. compared the influence that biogas slurry and conventional fertilizers have on the abundance, diversity and functionality of micro-organisms of regularly cultivated soils, Chinese chives (2019). Unlike conventional fertilizers, the application of biogas slurry resulted in a significant increase in the population and diversity of soil microbial communities (Guo et al., 2019). Similarly, the functionality of microbes as relates to nutrient cycling significantly improved following the addition of biogas slurry. Finally, in a field experiment, Yoshikawa et al. integrated organic matter composting into spinach farming in Kisatsu, Japan and established that it solves the issue of landfills, mitigates greenhouse gas emissions and improves the overall soil quality (Yoshikawa et al., 2021). These case studies indicate that using organic wastes as opposed to conventional fertilizers in farmlands is a more environmentally friendly agricultural practice.
Recommendations
This critical assessment reveals that organic wastes can be used in agriculture as a sustainable alternative to conventional fertilizers due to their ability to improve the quality and abundance of crop production while also ensuring environmental health. Consequently, there is a need to encourage the adoption of organic farming among agriculturalists. The following recommendations can aid the adoption of organic farming:
Farmer Education
Governments and environmental governing bodies in various regions and countries should work together through workshops, seminars, extension services and training programs to educate farmers on sustainable organic farming practices and their associated benefits. This approach should also involve sharing organic farming successful stories with the farmers to demystify any fears or myths about the practice.
Offering Subsidies to Farmers
There are two common approaches to subsidize organic farming and encourage its adoption by farmers. First, governments can give financial assistance to farmers who agree to practice organic agriculture. Such assistance can include helping the farmers in acquiring organic inputs or implementing technologies to encourage organic farming such as establishing composting plants closer to farmers. Secondly, farmers willing to adopt organic farming systems should receive infrastructural support from governments or non-governmental organizations. This can include financial and technical help in establishing composting units or storage facilities. Further, financial institutions should make it easy for such farmers to access loans to implement the system.
Policy Formulation
Environmental governing bodies in various countries should develop and implement policy regulations that discourage inorganic farming while encouraging organic farming. This could involve limiting the use of certain fertilizers due to their degrading influence on the environment. In addition, governments should formulate policies that assure organic farmers of fair pricing and market accessibility. Competitive pricing for organically produced foods will encourage farmers to adopt organic farming.
Conclusion
Globally, food production has been heavily dependent on the use of chemical fertilizers to increase volumes of production. However, from their production to synthesis, these chemicals pose severe environmental risks; endangering lives, lowering soil quality, and polluting water sources. Organic wastes, when applied directly to land used for food production, present an environmentally sustainable alternative to conventional fertilizers. Instead of dumping organic matter into landfills where they contribute to air pollution, they can be used as farmyard manure/compost or bio-solids in agricultural land where they improve soil health. In soil, organic matter enhances the abundance and functionality of microbial communities, increases carbon sequestration, enhances water-holding capacity, and improves soil nutrient content. While challenges like nutrient variability and application logistics may discourage its adoption, this critical assessment finds organic wastes to be a more sustainable alternative to inorganic fertilizers. Therefore, this critical assessment recommends approaches like farmer education, offering subsidies, and the formulation of policies that encourage farmers to incline more towards organic farming systems.
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