Municipal solid waste (MSW) includes everyday items discarded from homes, businesses, and institutions. Understanding the journey of waste after it leaves our immediate surroundings is important.
Landfills: The Primary Destination
Landfills are engineered facilities designed for waste disposal, differing significantly from older, unregulated dumps. Modern landfills are constructed with systems to minimize environmental harm. They typically feature a liner system, often made of compacted clay and synthetic materials, to prevent leachate—a liquid formed when water filters through waste—from contaminating groundwater.
Leachate collection systems gather this liquid for treatment. Landfills also manage gases produced by decomposing waste, primarily methane and carbon dioxide. Methane, a potent greenhouse gas, is often captured and converted into energy or flared off. Landfills accept various waste types, including household and commercial trash, and construction debris. Waste is compacted daily and covered with soil or other materials to reduce odors and deter pests.
Incineration and Energy Recovery
Incineration is a waste treatment process that involves burning waste at high temperatures. This process significantly reduces the volume of waste. Waste-to-Energy (WtE) facilities utilize the heat generated from incineration to produce electricity. In these plants, waste is combusted to heat water and create steam, which then drives a turbine connected to a generator.
After combustion, an air-pollution control system removes pollutants from the gases before they are released. The remaining material, known as bottom ash, can be used in construction materials or metals can be recovered for recycling. Incineration offers the benefits of waste volume reduction and energy generation, providing an alternative to landfilling.
Recycling and Repurposing
Recycling diverts materials from disposal and gives them a new life, contributing to a more circular economy. The process begins with the collection of recyclable materials, which are then transported to a Material Recovery Facility (MRF) for sorting. At the MRF, non-recyclable items are removed, and materials like plastics, paper, glass, and metals are separated by type using various technologies.
After sorting, materials are cleaned and compressed for transportation. These processed materials become raw materials for manufacturing new products. For example, plastics are shredded and pelletized, paper is pulped, and metals are melted. This cycle helps reduce the need for new raw materials and minimizes waste.
Organic Waste Management
Organic waste, such as food scraps and yard trimmings, can be managed through methods that prevent it from going to landfills. Composting is one such method, involving the aerobic decomposition of organic matter by microorganisms. This process transforms waste into a nutrient-rich soil amendment called compost, which enhances soil fertility and water retention.
Another method is anaerobic digestion, where microorganisms break down organic waste in an oxygen-free environment. This process produces biogas, primarily methane, which can be captured and used as a renewable energy source. Diverting organic waste from landfills through composting or anaerobic digestion helps reduce methane emissions, a significant greenhouse gas produced when organic matter decomposes without oxygen.
Mismanaged Waste and Its Impact
When waste is not properly managed, it can lead to environmental harm, including illegal dumping and marine pollution. Illegal dumping involves discarding waste in unauthorized locations, often due to a lack of convenient disposal options or limited awareness. This practice can contaminate soil and water, harm wildlife, and reduce the quality of affected areas.
A significant portion of marine plastic pollution originates from land-based sources. Plastic waste can be carried by wind or stormwater runoff into rivers and drainage systems, eventually reaching the ocean. Once in marine environments, plastic breaks down slowly into microplastics, which can be ingested by marine life, leading to injury, starvation, or entanglement. These microplastics can also transport pollutants and invasive species, impacting ecosystems and potentially entering the human food chain.