Green engineering follows nine guiding principles:
#Engineer processes and products holistically, use systems analysis and integrate environmental impact assessment tools.
#Conserve and improve natural ecosystems while protecting human health and well-being.
#Use life-cycle thinking in all engineering activities.
#Ensure that all material and energy inputs and outputs are as inherently safe and benign as possible.
#Minimize the depletion of natural resources.
#Prevent waste.
#Develop and apply engineering solutions while being cognizant of local geography, aspirations, and cultures.
#Create engineering solutions beyond current or dominant technologies; improve, innovate, and invent (technologies) to achieve sustainability.
#Actively engage communities and stakeholders in development of engineering solutions.
In 2003, The American Chemical Society introduced a new list of twelve principles:
# 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 recycling, 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.