Green and Sustainable Manufacturing of Advanced Materials—Progress and Prospects

Mrityunjay Singh1; Tatsuki Ohji2; R. Asthana3    1 Ohio Aerospace Institute, Cleveland, OH, USA,
2 National Institute of Advanced Industrial Science and Technology (AIST), Nagoya, Japan,
3 University of Wisconsin-Stout, Menomonie, WI, USA

1 Introduction

Manufacturing is a substantial part of global economy, and manufacturing practices play a critical role in all aspects of modern life. Green and sustainable manufacturing has emerged as a globally recognized mandate. Sustainable manufacturing is defined by the U.S. Department of Commerce as “the creating of manufactured products that use processes that are nonpolluting, conserve energy and natural resources, and are economically sound and safe for employees, communities, and consumers” (http://www.nacfam.org/PolicyInitiatives/SustainableManufacturing/tabid/64/Default.aspx). It has given impetus to development of green materials and technologies that orchestrate with self-healing and replenishing capability of natural ecosystems. It has focused attention on conservation of energy and precious materials, and recovery, recycling, and reuse in virtually all industrial sectors including but not limited to transportation, agriculture, construction, aerospace, energy, nuclear power, and many others.

Historically, industry and governments have been responsive to environmental issues even before sustainability became a recognized global movement. For example, in the United States, a number of acts and Codes of Federal Regulations (CFR) have addressed key environmental issues for several decades. Examples included the Water Pollution Control Act (amended 1987 Clean Water Act), Clean Air Act (amended 1990), Resource Conservation and Recovery Act (amended 1984), Comprehensive Environmental Response, Compensation and Liability Act (1980), and many others. These regulations provided “cradle-to-grave” programs for protecting human health and the environment from the improper management of hazardous materials including toxic effluents. Other CFRs specifically addressed the health and environmental effects of specific chemicals and materials such as the known carcinogens formaldehyde (29 CFR 1910.1048) and cadmium (29 CFR 19190.1027).

Although a focus on sustainable technologies in various forms has been around for a long time in part due to government regulations and sporadic public support for isolated cases that impacted regional concerns, a paradigm shift toward and awareness of the importance of transformative green and sustainable materials and manufacturing has only recently begun to gain momentum. As a field of academic enquiry and discussion, green manufacturing is relatively young. As an emerging global movement, it has gained considerable traction as part of the broader goals of sustainable development. It is now being increasingly recognized that the integration of green practices is crucial to sustainable technological development and the economic competitiveness of current society as well as that of future generations.

A number of important and widely practiced industrial processes such as case hardening, plating, casting, brazing, soldering, chemical vapor deposition, organic coatings, and numerous others involve consumption or release of harmful ingredients that are injurious to both human health and the environment. All such processes and technologies are candidates for a careful reassessment of the efficiencies and structural changes that could potentially make such processes sustainable. A classic example of sustainable practices is the abolition of lead in electrical and electronic assemblies and in public utility systems owing to the possibility of water and food contamination with extremely serious consequences to human health and the environment. Major initiatives in Europe, North America, China, Korea, and elsewhere have either banned or strictly limited lead use. Major global initiatives are currently in progress to develop green substitute materials for lead and similar hazardous and/or scarce metals and materials. Critical materials including rare earths have a major economic and strategic importance, but they are limited in supply. New materials need to be developed in an environmentally conscientious manner to offset the dependence of naturally occurring critical and strategic materials.

Another focus area of sustainable development involves component weight reduction by use of light materials (foams, magnesium, and titanium) with high specific strength and other key properties. This is being vigorously pursued for reducing fuel consumption and waste emissions mainly in the transportation sector (automotive and aerospace). This also offers additional benefits of lower losses, higher operating temperatures, and higher engine efficiency. Environmentally friendly materials such as ecoceramics, ecobrass, ecosolders, and ecocoatings, as well as energy-efficient light materials such as foamed metals and ceramics and composites have gained phenomenal ascendency in research and technology. Additionally, energy and emission reduction with the aid of established and novel technology such as microwaves, lasers, and biofuels has become increasingly important.

New materials developed from natural and renewable arboreal and biological resources should continue to gain importance into the future. Ceramics such as silicon carbide developed from such resources consume less energy for their production and less waste for disposal. Environmentally conscious ceramics (ecoceramics) are produced out of renewable resources such as wood. For example, biomorphic silicon carbide is obtained by pyrolysis and infiltration of natural wood-derived preforms. It reduces energy consumption and chemical by-products of conventional ceramic production methods such as hot pressing, sintering, reaction bonding, and chemical vapor deposition (CVD). Other methods include freeze casting of ceramics and microwave sintering that are devoid of binders and fugitive chemicals. Through conscious intervention, materials and products can be designed and manufactured in a more environmentally friendly manner to facilitate assembly, recycling, and reuse with reduced waste emission and energy consumption.

A large proportion of the world’s energy originates from fossil fuels while greener technologies such as nuclear, wind, and hydroelectrics generate the remaining share of total energy. The wide variety of materials used in these technologies—mainly metals, ceramics, and their composites—critically affect the performance of such technologies. Materials are enablers of advanced technology, and their properties and performance determine the system function and efficiency. Conversely, efficient development and production of current and emerging materials depends on the availability of innovative technologies for their production and fabrication. A competitive advantage in technology development can be accelerated through the development and application of new materials and processes. This complementary symbiotic relationship can help promote and advance sustainable practices with the materials producer, product designer, and manufacturer working in concert on shared concerns about environmental impact and sustainability while pushing the boundaries of the technology.

Over the next several decades, global demand for materials and energy is projected to sharply rise. This inevitably will impact the environment via increased carbon emission and energy consumption. In this context, an important goal of sustainability is the training and educational needs of a new generation of workforce that can think and act holistically about “cradle-to-grave” and “cradle-to-cradle” progression of materials and technologies. Many major industrial mishaps in the past have been linked to mistakes that could have been avoided with proper training and awareness. Examples include the mercury accumulated in fish originating from a fertilizer plant in Japan in the 1960s and leakage of toxic methyl isocyanate (MIC) gas from a former Union Carbide plant in India in the 1980s.

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