Organic waste recycling (methods, steps, significance, barriers)

Organic waste is any material that comes from either a plant or an animal and can be decomposed by microorganisms into carbon dioxide, methane, and simple organic molecules . Organic waste includes food scraps, yard trimmings, paper products, wood, animal manure, and sewage sludge . Organic waste accounts for most of the waste generated in nature and also in urban areas where people consume and discard various organic materials.

Organic waste has a significant impact on urban living systems, both positive and negative. On the positive side, organic waste can be recycled or converted into useful products such as compost, biogas, animal feed, and biofertilizers by different methods such as composting, anaerobic digestion, rendering, and immobilized enzyme reaction. These products can help improve soil quality, reduce greenhouse gas emissions, save resources, and generate renewable energy .

On the negative side, organic waste can also cause environmental and health problems when it is not properly managed or disposed of. Organic waste has a high moisture content which increases the volume of waste and lowers the incineration temperature, making it difficult to burn or landfill. Organic waste also produces odors and attracts pests and rodents which can spread diseases. Organic waste can also contaminate soil and water with pathogens, chemicals, and heavy metals if it is not treated or separated from other wastes .

Therefore, organic waste recycling is an important and beneficial practice for urban living systems as it helps reduce the negative impacts of organic waste and enhance its positive potential. In this article, we will discuss the need for organic waste recycling, the methods of organic waste recycling, the general steps of organic waste recycling, the significance of organic waste recycling, and the barriers and challenges of organic waste recycling.

Organic waste recycling is the process of transforming organic materials, such as food scraps, yard trimmings, and animal manures, into useful products like compost, biogas, and animal feed. Organic waste recycling has many benefits for the environment, society, and economy. Some of the main reasons why organic waste recycling is needed are:

• Reducing the waste stream: Organic waste accounts for more than 28 percent of what we throw away, which adds up to millions of tons of waste every year. By composting or digesting organic waste at home or in community facilities, we can divert some of that waste from landfills and incinerators, saving money and resources on waste management.
• Cutting methane emissions from landfills: When organic waste is buried in landfills, it decomposes anaerobically (without oxygen), producing biogas that contains methane and carbon dioxide. Methane is a potent greenhouse gas that contributes to climate change. Landfills are the third-largest source of human-generated methane emissions in the United States. By recycling organic waste into compost or biogas, we can reduce the amount of methane released into the atmosphere.
• Recycling nutrients and improving soil health: Compost is a rich source of nutrients and organic matter that can improve soil quality, fertility, and water retention. Compost can also help suppress plant diseases and pests, reducing the need for chemical pesticides and fertilizers. Biogas can be used as a renewable energy source for heating, cooking, or electricity generation, reducing our dependence on fossil fuels.
• Mitigating the impact of droughts: Compost can help retain moisture in the soil, reducing water runoff and erosion. This can help mitigate the effects of droughts and floods on crops and gardens. Compost can also increase the infiltration and storage of rainwater in the soil, replenishing groundwater supplies.
• Supporting food security and livelihoods: Organic waste recycling can provide valuable products and services for farmers, gardeners, and communities. Compost can enhance crop yields and quality, increasing food production and income. Biogas can provide a clean and affordable energy source for rural households and businesses. Animal feed can reduce the cost of feeding livestock and poultry. Organic waste recycling can also create jobs and opportunities for social inclusion and empowerment .

Organic waste recycling is a sustainable and beneficial way of managing organic waste that can help address some of the major challenges facing our planet today. By recycling organic waste, we can reduce our environmental impact, conserve our natural resources, and support our food systems and well-being.

There are different methods of organic waste recycling, each of which can be used for a particular group of waste to produce some form of useful organic matter. Some of the common methods are described below:

• Composting: Composting is a natural process in which organic waste is broken down into a nutrient-rich soil amendment by microorganisms that require oxygen. Composting can be done at home using food scraps and yard trimmings, or at larger scales using industrial or community composting systems. Composting has many benefits, such as reducing the waste stream, cutting methane emissions from landfills, improving soil health, and saving resources .
• Vermicomposting: Vermicomposting is a type of composting that uses worms to digest organic waste and produce worm castings, which are a valuable fertilizer for plants. Vermicomposting can be done indoors or outdoors using a bin with bedding material and worms. Vermicomposting is suitable for small-scale recycling of food scraps and paper products.
• Anaerobic digestion: Anaerobic digestion is a process that converts organic waste into biogas and nutrient-rich residue by microorganisms that can live without oxygen. The biogas can be used as a renewable energy source, while the residue can be used as a fertilizer or soil conditioner. Anaerobic digestion can handle a wide range of organic waste, such as wastewater, sewage sludge, animal manure, and food waste .
• Rendering: Rendering is a process that converts waste animal tissues into stable and usable forms such as feed protein and fat. Rendering involves exposing animal carcasses, bones, and fatty tissues to high temperature and pressure to destroy pathogens and separate the solid and liquid components. Rendering can be done on both kitchen and industrial scales, and can reduce the volume and odor of animal waste .
• Rapid thermophilic digestion: Rapid thermophilic digestion is a process that rapidly ferments organic waste by activating fermenting microorganisms at high temperatures. A rapid thermophilic digester works faster than a normal biodigester and produces biofertilizer that can be used on the soil. Rapid thermophilic digestion is mainly used for the treatment of sewage sludges .
• Immobilized enzyme reaction: Immobilized enzyme reaction is a process that uses enzymes to degrade organic waste into reusable forms. Immobilized enzymes are enzymes that are attached to a solid support, which allows them to be reused and perform under non-ideal conditions. Immobilized enzyme reaction can modify organic waste into products such as biodiesel, surfactants, and bioplastics .

The overall process of organic waste recycling begins with the collection of waste materials which are then passed through various steps to obtain a usable form of organic matter. The general steps/ mechanism of organic waste recycling can be explained as below;

• Collection: The first step in organic waste recycling is collection. Organic waste is collected from various sources and brought to a central location for disposal. After collection, organic waste can be sorted and processed into reusable materials . For example, composting requires organic waste to be collected in a pit or a bin, whereas anaerobic digestion requires organic waste to be collected in a digester.
• Decontamination: An important step in organic waste recycling is decontamination of waste in order to avoid its harmful effects. This step is particularly important while dealing with organic waste from industries or contaminated sources. Besides, any non-biodegradable substance like glass, plastic, and bricks, if present, should be removed during this step .
• Preparation: Before the organic waste is added to a recycling system, it should be prepared. The method of preparation employed depends on the type of recycling method chosen. For example, composting requires shredding and stacking of organic waste, whereas an immobilized enzyme system requires immobilized enzymes. Some methods might even require a period of stabilization prior to recycling, in which case, the time should be designated.
• Recycling process: Depending on the nature of the organic waste and desired end products, an appropriate method of recycling should be adopted. Human wastes like sewage and fecal wastes should be recycled via anaerobic digestion whereas sewages can be treated with thermophilic digesters. Different methods of recycling have different advantages and disadvantages, which should be considered before choosing one.
• Screening and grading: The obtained residues or compost are then screened into different sizes to be used for different purposes. Depending on the application of the end products, grading and screening are essential. For example, compost can be screened into fine or coarse particles depending on the type of soil or plants it will be applied to.

Organic waste recycling has multiple advantages that help prevent the problems that arise with the accumulation of waste products in nature. Some of the common advantages or significances of organic waste recycling are:

• Reduces greenhouse gas emissions: Recycling organic waste through composting, anaerobic digestion, and other methods can reduce methane emissions from landfills and help mitigate climate change . Methane is a potent greenhouse gas that contributes to global warming and has a higher global warming potential than carbon dioxide. When organic waste is sent to landfills, it decomposes and produces methane, a major contributor to greenhouse gas emissions and climate change . By diverting organic waste from landfills and recycling it into useful products, we can reduce the amount of methane released into the atmosphere and protect the environment.
• Conserves natural resources: Organic waste recycling can reduce the need for synthetic fertilizers by producing high-quality compost and other organic fertilizers . Compost is rich in nutrients and can improve soil health, fertility, and productivity . By using compost instead of chemical fertilizers, we can conserve natural resources, reduce pollution, and save money. Compost can also help retain soil moisture, prevent erosion, and suppress weeds and pests.
• Recycles nutrients: Organic waste recycling can recycle nutrients that are essential for plant growth and soil quality. Organic waste contains carbon, nitrogen, phosphorus, potassium, and other elements that are vital for plant nutrition and soil fertility. By recycling organic waste into compost or biogas, we can return these nutrients to the soil or use them as energy sources. Recycling nutrients can also reduce nutrient leaching and runoff, which can cause water pollution and eutrophication.
• Mitigates the impact of droughts: Organic waste recycling can help mitigate the impact of droughts by improving soil water retention and reducing irrigation needs. Compost can increase the water-holding capacity of the soil by enhancing its structure and porosity. This can help reduce water loss due to evaporation and runoff, and increase water availability for plant growth. Compost can also improve soil infiltration and drainage, which can prevent waterlogging and salinization.
• Reduces the waste stream: Composting is a great way to recycle the organic waste we generate at home. Food scraps and garden waste combined make up more than 28 percent of what we throw away. Not only is food waste a significant burden on the environment, but processing it is costly. The average cost to landfill municipal solid waste in the United States was around $55 per ton in 2019. With the United States generating more than 267 million tons of municipal waste in 2017 and sending two-thirds of that to landfills and incinerators, we spent billions of dollars on waste management. Composting at home allows us to divert some of that waste from landfills and turn it into something practical for our yards.

These are some of the significances of organic waste recycling that demonstrate its importance for environmental sustainability and human well-being. By recycling organic waste, we can not only reduce our environmental impact but also create valuable products that can benefit us and nature.

Even though organic waste recycling is a beneficial and sustainable method of waste management, there are some barriers and challenges that hinder its widespread adoption and implementation. Some of the common barriers and challenges of organic waste recycling are:

• Lack of awareness and education: Many people are not aware of the importance and benefits of organic waste recycling, or how to properly separate and dispose of their organic waste. They may also lack the knowledge of the available methods and facilities for organic waste recycling in their area. This leads to low participation and compliance rates among the public, as well as improper handling and contamination of organic waste .
• Lack of infrastructure and technology: Organic waste recycling requires adequate infrastructure and technology to collect, transport, treat, and utilize the organic waste and its products. However, many regions lack such facilities or have outdated or inefficient systems that cannot cope with the increasing amount of organic waste generated . Moreover, some methods of organic waste recycling, such as anaerobic digestion or immobilized enzyme reaction, require high capital investment and technical expertise, which may not be feasible or affordable for some communities.
• Lack of policy and regulation: Organic waste recycling is often influenced by the policy and regulation framework of the government and other stakeholders. However, some countries or regions may not have clear or consistent policies or regulations to support or incentivize organic waste recycling. For example, there may be no mandatory source separation or collection schemes for organic waste, no standards or guidelines for the quality and safety of recycled products, or no subsidies or tax breaks for organic waste recycling initiatives . This may create uncertainty and confusion among the public and the private sector, as well as discourage investment and innovation in organic waste recycling.
• Lack of market and demand: Organic waste recycling produces valuable products such as compost, biogas, biodiesel, or surfactants that can be used for various purposes. However, there may not be enough market or demand for these products, especially if they have to compete with cheaper or more established alternatives. For example, compost may not be preferred by farmers over chemical fertilizers, biogas may not be compatible with existing energy infrastructure, or biodiesel may not meet the fuel quality standards. This may reduce the economic viability and attractiveness of organic waste recycling.
• Lack of social acceptance and participation: Organic waste recycling involves the participation and cooperation of various actors, such as households, businesses, industries, municipalities, NGOs, etc. However, there may be some social barriers or challenges that prevent or limit their involvement in organic waste recycling. For example, some people may have negative perceptions or attitudes towards organic waste recycling, such as not believing in its environmental benefits, not trusting its safety or quality, or not feeling rewarded or recognized for their efforts. Some people may also face situational or behavioral barriers, such as inadequate containers, lack of space at home, unreliable collections, household disorganization, lack of time or routine. These factors may affect the willingness and motivation of people to engage in organic waste recycling.

These barriers and challenges can be overcome by various strategies and measures, such as raising awareness and education among the public and stakeholders; developing and improving infrastructure and technology for organic waste recycling; establishing and enforcing policy and regulation to support and incentivize organic waste recycling; creating and expanding market and demand for recycled products; and enhancing social acceptance and participation in organic waste recycling.

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