Materials and Recycling

The United States consumes a third of aU raw materials worldwide and approximately 1000 pounds of metals per capita—despite representing only five percent of the global population. As global economies strengthen (e.g., within developing countries such as China and India), this consumption disparity will inevitably shrink, adding even greater pressure on materials sustainability. 

Applying a systems approach will require that metal alloys be designed to meet performance requirements, while increasing recyclability. Advanced technologies to separate and identify tolerance of scrap metal input also need to be developed. This will require investment in basic science and resource recovery and recycling technologies. 

The following sections examine the two main segments of the material industrial base structural materials and functional materials. 

perfluoro carbon, and carbonyl sulfide into the environment. In contrast, secondary production of aluminum, using scrap input, requires only remelting—a far cleaner process with little or no hazardous waste. 

High value metals, metallic compounds, and intermetaUics are used in functional applications, such as electronic, photovoltaic, magnetic and other electrooptic and electro-mechanical devices. Consumer goods, such as sporting equipment, vehicles, and appliances, employ many valuable metals. Common metals used for these applications include precious metals, copper, silicon, aluminum, magnesium, titanium, refractory metals, lanthanides, rare-earth metals, and alkaline-earths. 

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The increased importance of renewable resources for raw materials and recyclability or biodegradability of the material at the end of its useful life is demanding a shift from petroleum-based synthetics to agro-based materials in industrial applications. Increased social awareness of environmental problems posed by the non-degradable, non-recyclable content of their products is forcing manufacturers to enhance the biodegradable content, which in turn favors a switch to biomaterials [1]. 

Recycle of scrap during manufacturing is conventional practice in the thermoplastics industries. At best it may be blended with virgin material and recycled in the same plant, often in the... 

A membrane-bounded organelle that contains a battery of hydrolytic enzymes that digest ingested material and recycle cell components is a/an... 

Raw materials and recycle (undersized, somewhat predensified material) are made available in day bins. It is essential that at all times enough material is available (controlled by level indicators) for continuous discharge from the silos. Activators and/or mass flow bin designs may be necessary to ensure constant flow. In most cases, the individual components of a mixture will be metered for correct analysis. It is important to take into consideration the recirculating material as it may influence the final analysis and, on the other hand, may be necessary to ensure acceptable densification. 

If the feed is made up of several components or of only one raw material and recycle, a mixer may be installed in front of the roller press. Selection of this piece of equipment plays an important role in pressure agglomeration. In dry, binderless applications, a high intensity mixer may excessively aerate the material and prohibit successful compaction because the roller press is not capable of sufficiently deaerating the blend. A too severe mixing action may also destroy primary agglomerates in the recycle which are necessary to obtain the required product density. 

Eysosomes are the intracellular organelles of digestion enclosed by a single membrane that prevents the release of its digestive enzymes into the cytosol. They are central to a wide variety of body functions that involve elimination of unwanted material and recycling their components, including destruction of... 

Evaluation of RA is of vital importance since it enables the determination of its acceptability and the quantity and type of new material to be added (aggregate material and recycling agents) after performing the appropriate mix design. 

According to the Secondary Materials and Recycled Textiles Association (SMART) and the Council for Textile Recycling [9, 10], more than 1000 businesses and organizations employing many tens of thousands of workers divert some 2 million tons of textile waste from the solid waste stream. Textile waste can be classified as either preconsumer or postconsumer. Preconsumer textile waste consists of by-product materials from the textile, fiber, and cotton industries. Each year 750,000 tons of this waste is recycled into raw materials for the automotive, furniture, mattress, coarse yam, home furnishings, paper, and other industries. Approximately 75% of the preconsumer textile waste is recycled. 

The mechanical properties of recycled PVC are detrimentally affected by the presence of contaminants which act as stress concentrators and so cause premature failure upon loading. Pulverisation of the recyclate to reduce the size of such impurities results in improved properties that compare with those of pure grades. Often contaminants can be other polymers such as PET, PE, paper, and so on [265]. In many countries especially European countries, PVC windows are now the first choice, ahead of those made from conventional materials and recycling is increasing to meet this demand. Thanks to their life span of up to 40 years without necessary maintenance, the qualities of these window frames currently entering the waste stream are modest. This will increase over time as more are used and as the windows, which were installed in the sixties, enter the waste stream. Germany already has automated plants for recycling PVC window frames. 

SMART (2003), Secondary Materials and Recycled Textiles. Retrieved July 28,2003, from http //www.smartasn.org/news.html. 

The Resource Cycle (energy, mineral resources, materials and recycling, linking technologies to resources). 

One of the most crucial aspects of green technology is the sustainable utilization of minerals. In a sense, the concept of sustainable mineral utilization is an oxymoron because minerals removed from the geosphere are not replaced. However, the idea of sustainability can greatly extend supplies of minerals. This section addresses the approach to sustainability in obtaining minerals. The broader questions of green utilization of materials, substitution of materials, and recycling are discussed in more detail in Chapters 14 and 16. 

In cycle I g tons of raw material and recycle material are supplied, and Sri tons of recycle material are produced ... 

Expression (1.1) is an equation describing not only the final stage of a pseudo-continuous process, but also that of a continuous process in the steady state. This means that in the steady state constant amounts of raw material and recycle material are supplied to a continuous system per unit of time, and hence the total reactor charge remains constant. 

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