Hurdles in Organic Waste Recycling: Implications and Solutions

Table of Contents

• Introduction to Organic waste recycling 
• What is organic waste recycling?
• Methods of organic waste recycling
• Process (General Steps / Mechanism) of organic waste recycling
• Significance of organic waste recycling
• Barriers and Challenges of organic waste recycling

Introduction to Organic waste recycling 

• Organic waste comprises biodegradable materials derived from living organisms such as plants, animals, and microorganisms, capable of breaking down into simpler organic molecules.
• These wastes exist in both solid and liquid forms, with solid organic waste typically containing 80-85% moisture.
• They originate from diverse sources like agriculture, households, and industries.
• Examples of biodegradable organic waste include food scraps, food-soiled paper, non-hazardous wood waste, landscape trimmings, and pruning materials.
• While organic waste can enrich soil fertility and support plant growth, improper disposal practices can lead to significant environmental damage.
• In recent times, the management and recycling of organic waste have gained prominence as crucial environmental initiatives.

1. Municipal solid wastes

Municipal solid wastes encompass everyday items such as product packaging, grass clippings, furniture, clothing, bottles, food scraps, appliances, paint, newspapers, and batteries, generated from residential areas, schools, hospitals, and businesses.

2. Cattle wastes

Cattle wastes, derived from animal sources, serve as valuable organic matter. They are rich in micro and macronutrients essential for crop growth and soil fertility, primarily through cattle manure and fodder. Additionally, poultry and piggery wastes contribute to organic waste from animal origin.

3. Food wastes

Food wastes constitute approximately 30% of total organic waste in nature, resulting from both natural processes and human activities. Examples include peelings, cores, leaves, fruits, twigs, outer skins, and sludges. Food wastes originate from fruit and vegetable canning, frozen vegetable processing, fruit drying industries, as well as residential areas, hotels, and restaurants.

What is organic waste recycling?

• Organic waste recycling involves managing organic wastes through various methods to convert them into useful materials.
• The necessity for organic waste recycling has grown with the rise of waste management challenges in many cities worldwide.
• Organic wastes constitute a significant portion of natural waste, impacting urban environments due to their high moisture content. This excess moisture increases waste volume and lowers incineration efficiency, adding to waste disposal burdens.
• To address these challenges, diverse treatment methods and practices have been developed and implemented globally.
• Utilizing microorganisms in organic waste management is a promising approach to enhance soil fertility while managing these wastes.
• In organic waste recycling, various treatments are applied to convert wastes into compost or vermicompost, valuable as natural fertilizers.
• Biological treatments represent a practical and efficient approach to processing organic waste, maximizing recycling and resource recovery.
• The core aim of organic waste recycling is to establish a sustainable cycle where biodegradable organic waste is transformed into beneficial organic manure or fertilizer through effective recycling techniques.

Methods of organic waste recycling

Various methods exist for organic waste recycling, each tailored to specific types of waste to generate useful organic materials. Here are some common approaches:

1. Animal feed

• One of the most common and effective methods of organic waste recycling involves feeding agricultural and food waste to cattle and other animals.
• This approach simplifies waste recycling by allowing people to donate kitchen scraps to farmers for animal consumption.
• However, directly feeding organic waste to animals can lead to health issues, prompting countries like the US to enforce regulations on the types and quantities of food that can be fed to animals.
• Feeding food waste to animals offers several benefits, including reducing landfill pressures, minimizing methane emissions from fruits and vegetables, and avoiding the need to convert organic waste into other forms.
• Additionally, this practice supports farmers by reducing their need to purchase additional animal feed, which can positively impact the economy.

2. Composting

• Composting involves the decomposition of organic materials through the action of soil organisms, converting nitrogen, phosphorus, potassium, and other nutrients into humus-rich components.
• This aerobic process requires specific conditions of moisture and biological heat production.
• While most organic matter can be composted, materials like woodchips and paper decompose more slowly compared to food and agricultural wastes. However, some woodchips are necessary to improve aeration during composting.
• The composting process includes an initial composting phase followed by stabilization to produce a final, stable product suitable for land application.
• Various composting systems exist, ranging from simple, inexpensive bin composting suitable for household use with kitchen waste and garden clippings, to sophisticated, high-cost reactor systems used for large-scale industrial composting.
• Compost bins are ideal for homes but can be slow in completing the composting process.
• Large-scale composting is typically conducted in automated reactors that regulate oxygen and moisture levels, producing significant quantities of compost for industrial purposes.

3. Anaerobic digestion

• Due to the adverse environmental impacts of landfilling and incineration, anaerobic digestion has emerged as a cost-effective technology for both renewable energy production and the treatment of high-moisture, energy-rich materials.
• In anaerobic digestion, specialized microorganisms break down various types of biomass and organic wastes to produce biogas and nutrient-rich residue suitable for land applications.
• The biogas generated in anaerobic digestion consists of methane, carbon dioxide, and small amounts of hydrogen and hydrogen sulfide.
• Compared to alternative methods, anaerobic digestion can process a broader range of substrates, including those with high moisture content and impurities.
• Common substrates used in anaerobic digestion include wastewater, sewage sludge, and animal manure.

4. Rendering

• Rendering is the process of converting animal tissues into stable and usable forms, such as feed protein.
• In rendering, fatty tissues, bones, and animal carcasses are heated to around 130°C and pressurized to eliminate pathogens.
• Rendering can be conducted on both small kitchen scales and large industrial scales.
• In some cases, non-animal products can also undergo rendering to create pulps.
• The products of rendering can be utilized in various ways; solid particles are commonly used in pet food, while fats are often incorporated into soap production.
• However, rendering has limitations, such as its inability to completely break down waste products like blood.

5. Rapid thermophilic digestion

• Rapid thermophilic digestion involves the accelerated fermentation of organic wastes using heat-activated fermenting microorganisms.
• A rapid thermophilic digester operates six to ten times faster than a standard biodigester.
• In this process, organic feedstock is introduced into the digester with forced air to stimulate aerobic microbial growth.
• Thermophilic digestion is an exothermic process that maintains high temperatures between 55-65°C.
• The end product of rapid thermophilic digestion is a biofertilizer that enhances soil fertility when applied.
• One of the primary uses of thermophilic aerobic digestion is in the wastewater treatment sector, particularly for processing sewage sludges.

6. Immobilized enzyme reaction

• Using enzymes instead of chemical catalysts for treating wastewater and similar waste products reduces by-product formation and energy consumption significantly.
• However, challenges such as maintaining enzyme stability and performance necessitate the development of robust enzyme stabilization systems.
• The use of immobilized enzymes in organic waste recycling enables effective degradation even under less-than-ideal conditions.
• Immobilizing enzymes also facilitates the reuse of biocatalysts across multiple processes, thereby reducing the costs associated with both chemical and enzymatic treatments.
• Various immobilization techniques, such as adsorption, entrapment, and encapsulation, can be employed for this purpose.
• Enzymatic processes in waste conversion allow for essential modifications like oxidation, hydrolysis, acylation, and phosphorylation.
• For instance, esterases can esterify oils to produce biodiesel, and sugars can be esterified for use as surfactants.
• These advancements contribute to a more cost-effective and efficient approach to waste management.

Process (General Steps / Mechanism) of organic waste recycling

The organic waste recycling process initiates with the collection of waste materials, followed by a series of steps to transform them into usable organic matter. Here's an outline of the general steps and mechanisms involved in organic waste recycling:

1. Collection

• The initial phase of organic waste recycling begins with gathering waste materials, whether it's at a household scale in kitchens or on a larger scale in industrial settings.
• A sufficient quantity of waste needs to be accumulated and appropriately contained in bags for transportation to the recycling facility.
• For composting, organic waste is gathered and placed in a pit, while for digestion processes, it is deposited into the digester for further processing.

2. Decontamination

A critical stage in organic waste recycling involves the purification of waste to prevent potential harmful effects, especially when handling industrial organic waste.

Furthermore, it is essential to eliminate any non-biodegradable materials such as glass, plastic, and bricks during this phase.

3. Preparation

Prior to integrating organic waste into a recycling system, it must undergo preparation tailored to the chosen recycling method. For instance, composting necessitates shredding and layering organic waste, while an immobilized enzyme system requires the use of immobilized enzymes.

Certain methods may also mandate a stabilization period before recycling, for which a specific duration should be designated.

4. Recycling process

Depending on the characteristics of the organic waste and the desired outcomes, selecting the appropriate recycling method is crucial.

For human wastes such as sewage and fecal matter, anaerobic digestion is recommended, while sewage can be effectively treated using thermophilic digesters.

5. Screening and grading

The residues or compost obtained are subsequently sifted into various sizes tailored for specific uses.

Grading and screening are essential steps depending on the intended applications of the end products.

Significance of organic waste recycling

Organic waste recycling offers numerous benefits that mitigate the issues associated with waste accumulation in the environment. Here are some of the key advantages or significances:

• Recycling biomass or biowastes through processes like anaerobic digestion enables the generation of energy in the form of biogas.
• Converting organic matter into compost conserves resources by providing biofertilizers, reducing reliance on chemical fertilizers.
• Separating organic and inorganic wastes enhances the efficiency of recycling non-organic materials.
• One of the significant benefits of organic waste recycling is its role in reducing air, water, and soil pollution, minimizing issues such as odor and gas emissions.
• Producing biofertilizers through recycling processes improves soil quality, enhancing soil fertility and promoting plant growth.
• Recycling organic wastes decreases greenhouse gas emissions associated with landfilling, transforming waste into less harmful forms.
• By recycling organic wastes, less waste remains for inefficient disposal methods like landfilling and incineration.
• Increasing the organic content of soil through organic matter recycling boosts soil fertility, enriching soil with essential nutrients that increase crop yields.
• Stabilizing organic wastes enhances nutrient content and availability, improving their value as fertilizers in agriculture. This approach aligns with concepts such as cleaner production, zero-waste policies, sustainability, and a bio-based circular economy.
• Certain compost types prepared with suitable substrates act as biocontrol agents, helping prevent and manage plant diseases.

Barriers and Challenges of organic waste recycling

While organic waste recycling is a valuable and evolving method of waste management, it faces several challenges that limit its widespread adoption:

• Prolonged application of compost-recycled waste on soil can lead to the accumulation of heavy metals, which may subsequently transfer to various levels of the food chain.
• Certain persistent organic pollutants, such as chlorinated dioxins, polycyclic aromatic hydrocarbons, and organochlorine pesticides, can accumulate in solids during treatment processes. These compounds may pose risks to lower organisms and potentially to humans and wildlife.
• The use of bio-fertilizers produced through methods like composting and vermicomposting may introduce toxic metals such as cadmium and lead into the environment, impacting human and animal health.
• Recycling processes like composting can generate odors that contribute to air pollution and discomfort in surrounding areas.