Methods of Organic Waste Recycling

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:

1. Animal Feed

• One of the most common and efficient ways of recycling organic waste is by giving agricultural and food waste to cattle and other animals as food.
• Feeding organic waste to animals is a simple and easy method of waste recycling.
• People can contact some farmers and donate their kitchen wastes so that the animals can take them up.
• However, the direct feeding of organic waste to animals might result in some health issues in such animals.
• Therefore, different countries like the US have made regulations on the extent of food and the type of food given to the animals.
• Recycling food through animal feed has many advantages like reduced pressure on landfills, reduced methane productions from fruits and vegetables, and the lack of need to convert organic waste into some other forms.
• This also helps the farmers as they do not have to buy extra animal feed and eventually, helps the economy.

2. Composting

• Composting is the process of decomposition of organic material where the organic material is acted on by soil organisms resulting in the recycling of nitrogen, phosphorus, potassium, and other soil nutrients into humus-rich components.
• Composting is an aerobic process that takes place under correct conditions of moisture and biological heat production.
• Even though all organic matter can be composted, some materials like woodchips and paper take much longer to compost than food and agricultural wastes.
• However, some amount of woodchips is essential to increase aeration in the composting process.
• The overall process of composting includes both the composting time followed by a period of stabilization to produce a final stable product that can then be applied to the land.
• There are different composting systems ranging from simple, low-cost bin composting to highly technical high-cost reactor systems.
• Compost bins are most suitable for use in houses to compost simple kitchen waste and garden cuttings. One of the major issues with compost bins is the time taken for the completion of the process.
• Large scale composting is conducted in large reactors with an automated supply of oxygen and moisture to generate large tons of compost for industrial applications.

3. Anaerobic Digestion

• Due to the negative impacts of landfilling and incineration, anaerobic digestion has been proposed due to the cost-effective technology for renewable energy production and treatment of high moisture and energy-rich material.
• During the anaerobic digestion process, anaerobic microorganisms convert different types of biomass and other organic wastes into biogas and nutrient-rich residue that can be used for lap applications.
• The biogas produced by anaerobic digestion includes gases like methane, carbon dioxide, and a trace amount of hydrogen and hydrogen sulfide.
• When compared to other methods, this method can utilize a much wider range of substrates, even those with high moisture content and impurities.
• Some of the commonly used substrates for anaerobic digestion include wastewater, sewage sludge, and animal manure.

4. Rendering

• Rendering is the process of conversion of waste animal tissues into stable and usable forms like feed protein.
• During the rendering process, fatty tissues, bones, and animal carcasses are exposed to a high temperature of about 130°C and then pressurized to destroy pathogens.
• Rendering can be carried out on both the kitchen and industrial scales.
• Some cases of non-animal products can also be rendered down to form pulps.
• The products of rendering can be applied in different forms where the solid particles are used in pet food products, and the fat is added to soap-making operations.
• Rendering, however, has some disadvantages like it cannot completely degrade waste products like blood.

5. Rapid Thermophilic Digestion

• Rapid thermophilic digestion is the process of rapid fermentation of organic wastes by activating fermenting microorganisms at high temperatures.
• A rapid thermophilic digester works six to ten times faster than a normal biodigester.
• In a thermophilic digester, the feedstock is fed into the digester with air forced through the material to support the growth of aerobic microbes.
• The process of thermophilic digestion is an exothermic process that maintains a thermophilic condition at 55-65°C.
• The product of rapid thermophilic digestion is a biofertilizer that can be used on the soil to increase soil fertility.
• The most common application of thermophilic aerobic digestion is in the wastewater industry for the treatment of sewage sludges.

6. Immobilized Enzyme Reaction

• The use of enzymes over chemical catalysts in the treatment of wastewater and other similar waste products reduces the formation of by-products and significant energy inputs.
• However, some challenges like maintaining the stability and performance of enzymes require the development of stabilized energy systems.
• The use of immobilized enzymes during organic waste recycling allows degradation activity even under non-ideal environments.
• Immobilization of enzymes also supports the reuse of biocatalysts for multiple processes which then reduces the cost of chemical and enzymatic processes.
• Immobilization techniques like adsorption, entrapment and encapsulation can be applied.
• The use of enzymes for the conversion of organic waste into reusable forms allows important modifications like oxidation, hydrolysis, acylation, and phosphorylation.
• Enzymes like esterases can be used to esterify oils to form biodiesel. Similarly, sugars can also be esterified to use as surfactants.
• All of these processes allow for a more economical and efficient way of waste management.