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UT ENS 112 - Chapter 17

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Environmental Science 112FALL SEMESTER 2018INSTRUCTOR: DR. Adrienne [email protected] 17Approaches to Waste Management● Waste refers to any unwanted material or substance that results from a human activity or process● Waste is divided into several categories○ Municipal solid waste is non liquid waste that comes from homes, institutions and small businesses○ Industrial solid waste includes waste from production of consumer goods, mining, agriculture, and petroleum extraction and refining○ Hazardous waste refers to solid or liquid waste that is toxic, chemically reactive, flammable, or corrosive○ Wastewater is water we use that we drain or flush● There are three main components of waste we generate○ Minimizing the amount of waste we generate○ Recovering discarded materials and finding ways to recycle them○ Disposing of waste safely and effectively● The waste stream is flow of waste as it moves from its sources toward disposal destinations● Minimizing waste at its source point is called source reduction and is the best way of dealing with the waste stream● The linear movement of products from their manufacture to their disposal is often described as “cradle-to-grave”○ The new cradle-to-cradle approach requires that materials from products 1are recovered and reused to create new productsMunicipal waste● Municipal solid waste is commonly referred to as “trash” or “garbage”○ This includes many different materials, from food scraps to paper, plastic, and glassConsumption leads to waste● Waste generation has nearly tripled in the United States since 1960, reflective of the increase in excess packaging and nondurable goods○ This trend ended around 2005, with source reduction and reuse practices leaving total waste generation flat.● As developing nations become more affluent, waste production and consumption both tend to increase○ Many economically disadvantaged people in these countries support themselves by scavenging and selling items from dumps● Developed countries have improved their waste collection and disposal, and the proportion of waste going to landfills has declined○ This corresponds to an increase in recycling and compostingReducing waste is our best option● Packaging is a major source of waste that can be easily reduced○ Consumers can buy unwrapped produce or buy food in bulk○ Manufacturers can switch to packaging that is recyclable or reduce the size and weight of their containers● Some governments are beginning to tax and restrict the use of plastic shopping bags, because they persist for so long and are often litteredReusing items helps to reduce waste● Consumers have many options for reusing items to further reduce wasteComposting recovers organic waste● Composting is the conversion of organic waste (food scraps, yard debris,etc.) into 2mulch or substrate through the action of bacteria, earthworks, and other detritivores and decomposers○ This compost is used to enrich soil, mimicking natural cycles of matter and preventing waste from reaching a landfill or incineratorRecycling consists of three steps● The first step of recycling is to collect and process used goods and materials○ Materials recovery facilities (MRFs) - facilities that separate items by weight and size using automated processes including magnetic pulleys, optical sensors, water currents, and air classifiers● The second step is for the the materials to be used to manufacture new goods● The last step involves consumers and businesses buying products made from recycled materialsRecycling has grown rapidly● VArious programs and efforts have increased recycling rates in the United States from 6.4% of the waste stream in 1960 to 25.7% in 2014○ One example is “trash audits”, where trash cans are emptied and recyclable materials are removed● Recycling rates vary greatly from one material to another● Low commodity prices can make municipal recycling programs unprofitable○ These market prices do not reflect external costs of not recycling, such as increased greenhouse gas emissionsFinancial incentives help address waste● In “pay-as-you-throw” garbage collection programs, municipalities charge residents for home trash pickup according to the amount of trash they put out● Bottle bills are laws that have consumers pay a 5-10 cent deposit on recyclable containers that is refunded when the containers are returned to the stores○ States with bottle bills have recycling rates about 3.5x higher than states without them3Sanitary landfills are our main disposal method● Sanitary landfills bury waste in the ground or pile it in large mounds engineered toprevent waste from contaminating the environment● Municipal landfills must adhere to standards set by the EPA under the Resource Conservation and Recovery Act of 1976● Waste placed into landfills is partially decomposed by bacteria and compresses under its own weight to take up less space● Soil is layered with the waste to speed decomposition and reduce odor and pests● Liners and collection systems prevent liquid leachate from escaping into the nearby groundwater● Landfills must be located away from wetlands and earthquake-prone faults, and at least 6 meters above the water table● Closed landfills are converted into public parks or other uses such as the freshkills Park in New York CityIncinerating trash reduces pressure on landfills● Incineration, or combustion, is a controlled process in which garbage is burned at very high temperatures○ Incineration reduces the weight of waste up to 85% and volume by up to 90%● Emission fro incinerators must be passed through scrubbers that spray liquid that neutralizes acidic gases and a system of filters called a baghouse that physically filters fly ashWe can recycle materials from landfills● Steel, aluminum, copper, and other metals are abundant enough in some landfills tomake salvage operations profitable when market prices for the metals are high enough● Organic waste from landfills could be mined and composted● Older landfill waste could also be incinerated in waste-to-energy facilities to produceenergy4Industrial Solid WasteRegulation and economies each influence industrial waste generation● The federal government regulates municipal solid waste● State and local governments regulate industrial solid waste, with regulation generally being less strict than municipal solid waste● Industry bases


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