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Green Engineering

Green engineering is the design and use of economically feasible products and processes that: 1) reduce the generation of pollution at the source, and 2) minimize the risks posed to human health and the environment. Green engineering incorporates environmental science along with sound engineering design principles to minimize the overall environmental impact of products and services during manufacture, processing, use, and disposal. Like the related field of green chemistry, green engineering operationalizes the philosophy that decisions to protect human health and the environment have the greatest impact and cost effectiveness when applied early in the design phase of a process or product.[175

How can Green Engineering contribute to Sustainability?

Green engineering provides a framework for evaluating, comparing, and minimizing the environmental impact of processes and products. The principles of green engineering can be applied to improve the sustainability of chemicals and products, as well as the processes employed to manufacture them.[177] Some general examples of the use of green engineering in sustainability include:

Green Engineering
  • Application of green engineering techniques, such as heat and mass integration, to more efficiently use energy, water, and materials, thereby reducing resource demands;
  • Application of life-cycle approaches to identify opportunities for environmental improvement and to compare environmental impacts of products;
  • Reducing the throughput of resources necessary to manufacture, distribute, support and service a product through a process known as “dematerialization.” Dematerialization (e.g., reducing the amount of packaging or using renewable or recycled materials) reduces the overall energy and material footprint of a product; and,
  • Recovering value from a product at the end of its useful life: rather than being disposed in landfills, obsolete products and residual materials can be recovered, recycled, and reused.[188]

What are the main steps in Green Engineering?

Because green engineering encompasses a variety of processes, it cannot be summarized by a single methodology. However, a set of twelve principles help guide green engineering.[177, 189] These principles, while not specific steps, describe a set of operational approaches that support greater sustainability in the designs of products and processes.

Twelve principles of green engineering.



Inherent Rather Than Circumstantial

Designers need to strive to ensure that all materials and energy inputs and outputs are as inherently nonhazardous as possible.

Prevention Instead of Treatment

It is better to prevent waste than to treat or clean up waste after it is formed.

Design for Separation

Separation and purification operations should be designed to minimize energy consumption and materials use.

Maximize Efficiency

Products, processes, and systems should be designed to maximize mass, energy, space, and time efficiency.

Output-Pulled Versus Input-Pushed

Products, processes, and systems should be "output pulled" rather than "input pushed" through the use of energy and materials.

Conserve Complexity

Embedded entropy and complexity must be viewed as an investment when making design choices on recycle, reuse, or beneficial disposition.

Durability Rather Than Immortality

Targeted durability, not immortality, should be a design goal.

Meet Need, Minimize Excess

Design for unnecessary capacity or capability (e.g., "one size fits all") solutions should be considered a design flaw.

Minimize Material Diversity

Material diversity in multicomponent products should be minimized to promote disassembly and value retention.

Integrate Material and Energy Flows

Design of products, processes, and systems must include integration and interconnectivity with available energy and materials flows.

Design for Commercial "Afterlife"

Products, processes, and systems should be designed for performance in a commercial "afterlife."

Renewable Rather Than Depleting

Material and energy inputs should be renewable rather than depleting.

Green Engineering also utilizes other tools discussed in this report; including life-cycle analysis and green chemistry. Green Engineering designs consider the entire life-cycle of a product or process in order to better promote sustainability, and inherent property analysis supports the efforts of Green Engineering to incorporate an inherently sustainable foundation in the initial design of a product or process.[177]

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What are the strengths and limits of Green Engineering in a sustainability context?

The principles of green engineering, and its associated tools, address the foundation of sustainability, in that they support designing green processes and products from the outset, rather than mitigating impacts once they occur. Green engineering provides a framework for evaluating and minimizing the environmental impact of the entire life-cycle of a product or process, including initial material and energy inputs.[177] One limitation of green engineering is that it rests on the premise that all environmental problems can be addressed through technology. Because this is not always the case, green engineering may not be appropriate in all circumstances.

In designing and/or improving the environmental performance of processes and products, practitioners of green engineering must take care to balance the appropriate principles against one another in any particular project. Generally, practitioners should ask questions that are relevant both locally and across the life-cycle of the product or process being designed.[190] Moreover, the most benign design or system may not be practicable, due to technological or economic constraints.[177]

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How is Green Engineering used to support EPA decision-making?

EPA’s Office of Chemical Safety and Pollution Prevention makes use of the various tools and approaches associated with green engineering in order to determine whether the manufacture, processing, use, or disposal of products and materials might present future risks to human health or the environment. In addition, EPA identifies opportunities to employ alternative technologies or designs to minimize chemical hazards and exposures. Recent approaches to pollution prevention have sought to minimize hazardous waste and chemicals by design, rather than by mitigating impacts.[175] For example, in July 2011, EPA proposed a revised Definition of Solid Waste Rule that would exclude 18 spent solvents from the definition of “solid waste” if they are remanufactured (re-processed) to commercial grade.[191] In addition, green engineering can be identified as a priority in regional Pollution Prevention and Source Reduction Assistance Grants. In one case, EPA Region 2 is funding a service-learning project led by Rowan University Exit EPA Disclaimer in which faculty and students work with the pharmaceutical industry to develop tools to better manage solvents.

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Where can I find more about Green Engineering?

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Illustrative Approaches Applying Green Engineering

  • Quantifying Economic and Environmental Benefits of Green Planning in Connecticut 

    Source: EPA Office of Sustainable Communities[170]

    Suite of sustainability tools: benefit-cost analysis; environmental footprint analysis; green engineering; collaborative problem-solving

    As more communities pursue sustainable planning and development, determining which approaches offer cost-effective economic, social, and environmental benefits may be part of the process for each community. In weighing options, predicting the value of various plans and approaches informs decision decision-making. However, many communities lack the resources to perform such analyses. The EPA Smart Growth Implementation Assistance (SGIA) Program provides contractor services to communities to facilitate sustainable planning and development. Communities awarded SGIA assistance then partner with teams of multi-disciplinary, national experts to assess the existing community, analyze options, and create plans for sustainable development. Connecticut's Capitol Region Council of Governments (CRCOG) received expert technical support from SGIA and also partnered with town municipalities, the Partnership for Strong Communities, University of Hartford, and American Farmland Trust. Together they developed the Smart Growth Guidelines for Sustainable Development and Design (PDF) (55 pp,29MB) to support community siting, planning, and developing housing strategies that incorporate smart growth approaches and green building techniques.

    The town of Manchester, one community assessed as part of the CRCOG project, developed plans to integrate green infrastructure approaches into the redevelopment of a vacant and blighted 250,000 square foot community shopping center known locally as the Parkade. In partnership with EPA’s Region 1, the town quantified economic and environmental benefits of incorporating green roofs, stormwater retention systems, street trees, constructed wetlands, and parks into a mixed-use, mixed-income housing development slated for the site.

    Quantitative BCA results are provided in the report, “From Grey to Green: Sustainable Practices for Redeveloping a Vacant Shopping Center (PDF)(30 pp, 24MB). It showed, for example, that if 75% of the roofs at Parkade were vegetated, they would absorb over three million gallons of rainwater, reducing the load on existing stormwater runoff sewer systems. Installing solar panels on 14% of commercial buildings at the site would offset all of those buildings’ energy costs. Property values could be 20% higher when located along parks.[248] The results of these and similar analyses help inform decision-making to determine how best to improve residents' quality of life while sustainably protecting nearby waterways.

  • Sustainable Chemistry: An Even Darker Shade of Green

    Source: EPA Office of Research and Development[265]
    Suite of sustainability tools: green chemistry; green engineering
    EPA researcher Dr. Rajender Varma has given new meaning to the phrase “reading the tea leaves” through his visionary development of new, green ways to synthesize chemicals and nanomaterials from things such as microwave ovens, magnets, and natural antioxidants found in coffee, vitamins, grape husks left over from winemaking operations, and, of course—tea.

    Varma and his team have developed dozens of new and patented methods for the chemical industry and others to make compounds in environmentally friendly ways.

    Working at an EPA research laboratory dedicated to tapping the principles of green chemistry and engineering to advance sustainability, Varma’s team is developing benign nanomaterials to replace conventional catalysts, substances that initiate or speed up chemical reactions but do not themselves change during the reaction. Catalysts can be expensive, dangerous if not handled properly, and may end up as waste products that must be treated and/or disposed of carefully. In contrast, Varma has created iron-based magnetic nanomaterial-based catalysts that are easily recycled.

    By building nanomaterial-based catalysts with a core of iron and coating them with other metals, the catalyst can be separated using a simple magnetic field and then re-used, avoiding the use of hazardous substances while creating virtually no waste. “I often feel these methods plagiarize Nature because our approaches mimic what nature does so elegantly in biological systems,” Varma says.

    Varma’s group has also pioneered a new method of synthesizing nanoparticles. Instead of using a typical “top-down” approach that relies on large energy inputs and toxic solvents to break down larger materials, Varma and his colleagues employ a simple “bottom-up” method that assembles nanomaterials at the molecular level. This novel approach avoids the use of hazardous reducing agents, and instead employs benign metallic salts (such as iron salts), water, and polyphenols from plant materials (tea, coffee, and red grapes) to act as reducing or capping agents to prevent nanomaterials from aggregating into larger clumps during the production process.

    Varma’s innovative methods for coating iron nanomaterials are earth-friendly in both their production and degradation processes, allowing them to be used for environmental remediation operations, even to clean up pesticides from soils near crops.

    Working with the Connecticut-based firm VeruTEK, Varma and his EPA colleagues have played an important role in developing and commercializing green remediation technologies Exit EPA Disclaimer. VeruTEK has used this approach for degradation of pollutants in water. The technology can also be applied directly to soil, where it forms nanomaterials that breakdown organic toxicants. The iron-based, phenolic-coated nanomaterials naturally degrade, so they can be left in place once applied, offering an attractive alternative to standard cleanup methods of extracting and hauling away contaminated soils for offsite cleaning before they are trucked back in and replaced.

    Not surprisingly, Varma’s work has attracted significant attention from the scientific community and beyond. He has briefed US Congressional staff and the President of India in addition to lecturing in Chile, China, India, Peru, and Venezuela. He pointed out that developing countries are immensely interested in methods that allow them to “leapfrog” by circumventing older technologies and embracing more efficient ones, such as when governments encourage the establishment of cell phone networks, allowing them to skip costly and disruptive installations of telephone poles and overhead wires in areas that previously had no telecommunications technology.

    The nanocatalysts that Varma’s team produces can be safely recycled and may be used over and over, and can even be utilized for clean-up operations using visible light from the sun. According to Varma, “this process allows for a little darker shade of green” as we transition to practices for more sustainable chemical manufacturing and use. “In addition to its monitoring and compliance efforts, hopefully EPA can be a beacon to others in developing sustainable methods going forward,” Varma says.

  • Economy, Energy, and Environment (E3) Projects in San Antonio, TX

    Source: EPA Office of Chemical Safety and Pollution Prevention[266]
    Sustainability assessment tools and approaches: environmental footprint analysis; green engineering
    In order to promote sustainable manufacturing and economic growth, EPA’s Office of Chemical Safety and Pollution Prevention supported E3: Economy, Energy and the Environment (E3) projects in San Antonio, TX. The E3 projects sought to provide small-to-medium sized American manufacturers with the necessary technical assessments and tools to improve floor processes and minimize waste generation. E3, a framework that evolved from the Green Suppliers Network, is a coordinated federal and local technical assistance program that provides technical assessments of production processes and training in lean manufacturing and energy management.
    The San Antonio E3 projects addressed a goal set by CPS Energy, a local municipally-owned utility, to reduce nine megawatts of electrical demand from San Antonio’s manufacturing sector by 2020. To achieve this goal, the utility collaborated with the Texas Manufacturing Assistance Center (TMAC) to provide training, resources, and tools to help local manufactures increase efficiencies in energy and material use. In these projects, manufacturing personnel participated in customized, hands-on assessments of production processes on the factory floor. The personnel were then trained at TMAC to use “lean and green” manufacturing and energy management tools to improve operations. After completing the training, manufacturers received a list of recommendations for streamlining their industrial processes, increasing profitability, and improving overall environmental performance.
    Other partners in the collaboration included the Department of Commerce’s National Institute of Standards and Technology’s Manufacturing Extension Partnership, EPA’s Green Suppliers Network, and the Department of Energy’s Industrial Technologies Program’s Industrial Assessment Center, based out of Texas A&M University. In 2009 and 2010, ten local companies, including heating, ventilation, and air conditioning manufacturers, bakeries, apparel manufacturers, and aerospace part manufacturers, participated in the program.
    As a result of the program, San Antonio’s manufacturing sector reduced energy demand by an average of 557 kilowatts per customer and energy use by over 2.9 million kilowatt-hours. These energy savings also yielded an annual reduction of 1,744 metric tons of carbon dioxide and annual cost savings of over $360,000. San Antonio’s E3 program has ongoing projects, with additional proposals pending. The program is now self-sustaining, funded by clients who benefited from the services and local utility rebates.

  • Parking Lots: Letting It Soak In

    Source: EPA Office of Research and Development [267]
    Suite of sustainability tools: green engineering
    This past winter brought a thick blanket of snow to much of the country. Big piles lined our driveways. Gigantic, dirty-white mounds claimed parking spaces from lots in New England to the Mid- Atlantic. But things are starting to warm up.

    The big melt is here. 

    When the snow that once covered a parking lot or other paved surface melts, the resulting water flows toward the nearest storm drain, entering the local watershed. And as snowmelt and other runoff flows over paved surfaces, it accumulates contaminants such as leaked motor oil, road salt, and hydrocarbons deposited from motor vehicle exhaust.

    A team of EPA researchers are exploring how parking lots designed with permeable pavements and rain gardens can help.

    To get started, EPA replaced a 43,000-square-foot section of parking lot at the Agency’s research lab and offices in Edison, New Jersey with three different types of permeable pavement, and planted several rain gardens with different types of vegetation.

    Over the next decade, EPA researchers will evaluate the effectiveness of each pavement type and the rain gardens in removing pollutants from stormwater. They will also measure how each type of permeable pavement helps water filter back into the ground.

    Throughout the project, scientists will compare changes in surface performance with standard parking lot maintenance, and track temperatures under each surface to detect patterns. Monitors will measure the water quality for at least ten years, to establish changes associated with time and seasonal patterns.
    The research will be conducted without taking up parking spaces, as the lot will be functional during the study. This way, researchers can accurately evaluate how the different types of pavement handle traffic and vehicle-related pollution.

    This is the first real-world experiment to determine if permeable pavement reduces pollutant runoff. The measurements and analysis EPA scientists make will answer some key questions about how effective permeable pavements are at reducing both the volume of stormwater and the amount of environmental pollutants flowing off parking lots and into nearby streams and rivers. This information will be a big help to municipalities and land managers across the country. 

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