Why do you feel that these innovations are coming out of Europe and not out of U.S. companies?
Unit IV Upon completion of this unit, students should be able to:
2. Evaluate the evolution of technologies related to solid waste management.
5. Describe best practices of solid waste management in an urban society.
Reading Assignment Chapter 5: Separation Processes
Unit Lesson The most important guiding principle that affects the effectiveness of a sorting operation is the quality of the recycling program. For example, communities that rely on technology to remove plastics in glass sorting and crushing operations will experience slow throughput, and they will require additional manual labor and costs to watch over the processing. Having a good separation in the home and at the truck is often the difference between making money and having a loss when the recyced product is sold into commerce. It is the increasing costs of refuse collection and disposal that are driving the development of new and more capable separation technologies. The majority of these new processes are being piloted in the European Union (EU) where there is a community-wide commitment to maximize recycle and reuse of waste products. In the U.S., companies tend to recycle with the purpose of deriving economic value, either to recover content for reuse or to avoid the cost of disposal. In the EU, local citizens participate in recycle programs to do their part to save the environment. The waste framework directive requires that by 2020, at least 50% of household waste and 70% of construction debris must be recycled or reused (Council of the European Union, 2008). However, each EU country is responsible for developing its own programs to meet these goals. To achieve the 50-70% levels, it is essential that residential recycling programs provide clean recycle content and that waste is pre-sorted at the point of disposal. Europe routinely uses the following technologies to accomplish its sorting goals. These include building treatment trains that incorporate from one to three of these technologies operating in series.
1. Trommel separators and drum screens separate according to particle size. 2. Eddy current separators separate ferrous and non-ferrous metals. 3. Inductive sorting occurs when metals are separated using fast jets of air on conveyor belts. 4. Near infrared sensors separate materials based on reflection of infrared light. 5. X-ray technology separates waste based on density.
In Denmark, refuse sites shred the waste first and then use manual pickers (hand sorters) to pull out and classify recoverable content. By doing a high-level sort and classification of recycled content, a higher price for recovered materials can be obtained in the marketplace. The higher purity of the recovered content makes it more desirable with increased demand and pricing. European companies are developing innovative separation technologies to save on space and costs and to minimize manpower requirements. One technology recently introduced involves a mobile sorting unit. Since it is not always economical to transport waste to the recovery site, a mobile unit allows the sorting equipment to be brought to the waste. The mobile unit uses a series of drum screens that are kept free of clogging by using rotating brushes in the units. These units work well at construction sites where building materials and soil debris need to be separated. These units can also work well at compost sites where the compost is put
UNIT IV STUDY GUIDE
Unit Operations for Separating Municipal Solid Waste
MEE 5901, Advanced Solid Waste Management 2
UNIT x STUDY GUIDE
through the rotating drums to pull out large pieces and materials undesirable for sale in commerce.Compost is an excellent soil conditioner and fill material at municipal landfill sites. In Norway, waste processors use near-infrared sensor technology to sort refuse according to its spectral properties. These sensors are built on the cyan-magenta-yellow color scales, and they are capable of determining the difference between transparent, opaque, and dense materials. The same treatment train will also incorporate an electromagnetic unit to pull out metals based on their electromagnetic properties. In France, the focus is on spearating paper from cardboard. Waste processors use mid-infrared detectors to accomplish this separation. In Germany, the focus is on recovering specific materials from circuit boards contained in electronic waste. What makes these circuit boards have commercial value is the presence of rare earth metals that need to be recycled. Rare earths metals are utilized in both everyday and sophisticated electronic devices. Australia is one of the few countries where these metals are mined. Besides there being a limited number of mines, the majority are owned and controlled by China, which has signed international agreements to make a percentage of these materials available on the open market. Countries seeking more than their allotment will need to gain access to rare earths by recycling waste electronics. Germany has taken this technology further by utilizing inductive, optical, and near-infrared sensors in their sorting equipment to identify and separate out contaminants from shredded electronic wastes. The equipment is able to evaluate 500,000 shredded parts per second with the ability to remove 500 identified pollutants per second from the refuse. The future is about gaining higher efficiencies and purities of recycled materials and using smaller equipment that is capable of operating at speeds normally seen in high-production manufacturing facilities. The future of development will focus on making these machines more capable of working on a variety of waste types ranging from agricultural wastes to complex electronics being stripped apart for valuable metal fragments. In the future, recovery operations will give a priority to sorting minerals, scrap electronics, food wastes, and metals for recycling. Recently, many of these technologies are being adopted in China. EU companies looking to export their technologies are providing China with disc separators that work on a wide range of mixed wastes. China is starting to reprocess old landfills and recover valuable materials (e.g., brown coal and metals) that were previously disposed of as waste in these sites. In addition to benefitting from the material recovery, landfill cleanup projects are helping to stop the adverse impacts that these poorly designed and operated landfills have on the environment. Food wastes are now being separated out from these dumps, and they are being redirected to compost piles. If the efficiencies of recovering recyclable materials are high, the profits of recycling may fully cover the costs of reconstructing landfills based on current designs standards. Some of the newer technologies in use are now capable of sorting out and separating wet materials. This is important for wastewater treatment plants, where waste sludge can be separated and dewatered for stabilization in a compost pile.
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