Biodrying of Municipal Solid Waste: A Case Study in Malaysia

Abstract

Municipal solid waste (MSW) in Malaysia contains excessive moisture, which complicates recycling segregation and makes the use of advanced technology, such as solid waste combustion, inappropriate and harmful. Furthermore, MSW pre-treatment to reduce moisture content is uncommon in Malaysia. Biodrying is a cost-effective and environmentally beneficial technology since the fundamental principle relies on internal energy generated by the decomposition of organic waste. The process of biodrying could be a useful alternative for MSW management, allowing for the production of derived fuel. This chapter focuses on the potential of biodrying to reduce excessive moisture content for MSW, particularly in Malaysia. Through nine sub-chapters, this book chapter provides an overview of the fundamentals of solid waste biodrying as well as the potential of solid waste biodrying systems in Malaysia. The first chapter provides a succinct overview of the concerns and challenges of solid waste management in the world and Malaysia. In Chap. 2, a concise explanation of the drying technology is described. The solid waste biodrying treatment system is covered in Chap. 3, followed by the design of the biodrying reactor in Chap. 4. In Chap. 4, there is also a more detailed description of the case study that is being conducted at Universiti Kebangsaan Malaysia. The factors that influence the biodrying process are discussed in Chap. 5. Chapter 6 presents the direct observation of fieldwork at solid waste biodrying plants in Malaysia and abroad. The importance of biodrying from various perspectives is elaborated in Chap. 7, and the potential use of solid waste biodrying in solid waste management in Malaysia is discussed in Chap. 8. Finally, Chap. 9 concludes the importance of a solid waste biodrying system in the future.

Glossary

Biodrying

Is a pre-treatment method for solid waste that combines biological and mechanical principles. It is a sort of natural biological solid waste treatment that uses internal heat to eliminate moisture. When compared to the use of high-cost, cutting-edge treatment technologies, natural biological treatment is an effective treatment method that is also environmentally friendly. Furthermore, biodrying waste can be used as an energy source. The potential for heat recovery from solid waste is facilitated and improved by biodrying of plants, which creates refuse-derived fuel (RDF) as the major product by eliminating excess moisture.

Calorific Value

Is defined as the amount of heat produced by the complete combustion of a unit volume of a substance. Kilojoule per kilogram (kJ/kg) is the unit of calorific value. It is also known as a parameter used to define the energetic content of materials; it is also known as gross calorific value (GCV) or high heating value (HHV). It is significant because it provides the value of fuel or food in numbers that can be calculated using a formula. Because humans consume fuels and food on a daily basis, it is critical to track their consumption, which is also important in health and financial aspects.

Composting

Is the natural process of microorganism ‘rotting’ or decomposing organic materials under controlled settings. After composting, raw organic materials such as crop residues, animal wastes, food waste, some municipal wastes, and suitable industrial wastes improve their suitability for application to the soil as a fertilising resource. Controlled biological decomposition of organic solid waste materials can occur under aerobic or anaerobic conditions. Composting can be accomplished in windrows, static piles and enclosed vessels.

Conduction Drying

Is a method that heats the air using a heat source, such as an electric heater. Heat is transferred from the heater to the air through physical contact between the two. In an indirect heat-transfer dryer, wet materials are not in direct contact with heating media. A blower or fan is then used to convey the warm air to the drying area. The heat in the air is then used to speed up the drying process, which entails evaporating any water (or other liquid) that remains on the part after it has been cleaned and rinsed.

Convection Drying

Is the use of convective transfer in the drying process. During convective drying, the ambient air is frequently heated. This air will circulate around the damp material. This contact between the heated air and the material results in a heat and mass exchange between the two media.

Dissolved Air Flotation (DAF)

Has recently been understood as one of the most efficient and reliable methods for removing suspended solids (TSS), biochemical oxygen demand (BOD5), fats, oils and grease (FOG), phosphorus (P) and nutrients from wastewaters. Contaminants are eliminated by pumping air under pressure into a recycled stream of clarified DAF effluent to create a dissolved air-in-water solution. In an internal contact chamber, dissolved air escapes from the solution in the form of micron-sized bubbles that adhere to the contaminants, and this recycle stream is combined and mixed with incoming wastewater. Bubbles and contaminants rise to the surface and form a floating bed of material, which a surface skimmer removes into an internal hopper for further processing.

Dynamic Respiration Index

Is used in a respirometer system to determine the current rate of aerobic microbial activity of solid recovered fuels. The current rate of aerobic microbial activity is determined by measuring the oxygen uptake rate by microorganisms to biodegrade easily degradable organic matter in the sample itself under defined continuous airflow and adiabatic conditions.

Freeze-Drying

Is also known as lyophilisation is a water removal process that is commonly used to preserve perishable materials in order to extend their shelf life and/or prepare them for transport. Freeze-drying is the process of freezing a substance, then lowering the pressure and increasing the heat to allow the frozen water to vaporise (sublimate). The three steps of freeze-drying are freezing, primary drying (sublimation) and secondary drying (adsorption). Freeze drying can reduce drying times by up to 30%.

Green Technology

Is the development and usage of products, equipment and systems that help to protect the natural environment and resources while minimising and reducing the negative effects of human activity. It can also refer to clean energy production, which is the use of alternative fuels and technologies that are less destructive to the environment than fossil fuels. Green technology’s goal is to protect the environment, repair past environmental damage, conserve natural resources, and preserve the Earth’s natural resources. Green technology has also grown into a thriving industry that is attracting massive amounts of investment capital.

Hydrolytic

Literally means water reaction. It is a chemical mechanism in which a molecule is broken into two pieces by adding a molecule of water. The most common hydrolytic occurs when a salt containing a weak acid or a weak base (or both) is dissolved in water.

Perforated Baffle

Is typically a straight pipe with a lot of small holes. As a result, vapour condensate can easily pass through this perforation.

Rotary Dryer

Is used to remove excess water from organic materials in order to make them more usable. Rotary dryers elevate materials and circulate them through heated air, allowing moisture to evaporate and making organic materials viable. The feed materials in all rotary dryers pass through a spinning cylinder known as a drum. It is a cylindrical shell made of steel plates that is slightly inclined. In some circumstances, a negative internal pressure (vacuum) is used to prevent dust from escaping.

Solar Drying

Is a system that makes use of solar energy to heat air and dry any substance that is loaded. Solar dryers can be classified as either direct or indirect. The former entails directly exposing the material to sunlight. In the latter, the material is dried by circulating hot air over it without being directly exposed to the sun. The benefits of any solar dryer would be determined by the type and amount of material to be dried.

Spray Drying

Is one of the most energy-intensive drying methods; it is nevertheless necessary for the manufacturing of dairy and food product powders. Spray drying works by atomising the input liquid into small droplets, which are then subjected to a stream of hot air and converted into powder particles. Atomisation is a distinguishing feature of the spray drying process and is crucial in determining the finished product’s quality. It involves creating a large number of droplets from a liquid stream, greatly increasing the liquid’s surface area and allowing for a faster drying rate. A variety of simultaneous heat and mass transfer processes occur when the atomised droplets come into contact with the heated air currents entering the chamber. Heat is transferred to the product in order to evaporate moisture, and mass is transferred to the surrounding gas as a vapour.

Sun Drying

Is the process to leave material outside in the sun and wind for approximately 7–10 days, depending on the temperature and humidity for good dehydration. In terms of drying temperature, the most important thing is to dry the material in bright, sunny and dry weather. The greatest part about sun drying is that it is a low-cost and low-investment process. However, there are a few drawbacks to sun drying; for example, the temperature cannot be controlled and may occasionally become overheated. Furthermore, sun drying is a labour-intensive method that involves a large number of people in the process. Furthermore, the sun drying process is slightly risky due to its reliance on the unpredictability of weather conditions.

The Bulking Agent

Is a carbon-based substance that gives your compost pile structure (or bulk). Wood chips, wood shavings, sawdust, dry leaves, shredded landscape waste, shredded paper, shredded cardboard and animal bedding are all common examples. Inside the compost heap, a good bulking agent provides free air space. This traps air and oxygen, allowing the microorganisms in compost to work without having to introduce extra air on a frequent basis. A good bulking agent is a dry material that effectively balances the high moisture content of the food waste.

Thermophilic Bacteria

Thrive at higher temperatures, while mesophilic bacteria thrive at lower temperatures. This means that thermophilic bacteria thrive at temperatures ranging from 45 to 122 °C, while mesophilic bacteria thrive at temperatures ranging from 20 to 45 °C. Mesophilic bacteria are thought to be the best soil decomposers. In addition, they contribute to food contamination and degradation. Thermophiles can be found in a variety of harsh environments, including direct sunlight-exposed soil, silage, compost heaps, volcanic environments, hot springs, deep-sea hydrothermal vents and so on. Thermophiles include archaea and bacteria. These organisms have strong structures that can withstand high temperatures.

Waste

Is defined as any substance that is discarded after its primary use or that is worthless, defective and useless. The primary aim of waste management is to reduce the harmful effects of hazardous waste on the environment and human health. If waste is harmful or toxic, it could potentially be a source of disease and death, not just for humans, but for everything that supports life, such as water, air, soil and food.