Sustainable Engineering Principles & Life Cycle Assessment

Posted on Jul 9, 2025 in Business Administration and Innovation Management

Understanding Sustainability & Sustainable Engineering

Sustainability, as defined by Merriam-Webster, refers to (1) a method of harvesting or using a resource so that it is not depleted or permanently damaged, and (2) a lifestyle involving the use of sustainable methods.

Sustainable development, according to the Brundtland Commission, is “development which meets the needs of the present without compromising the ability of the future to meet its needs.”

Sustainable engineering is defined as the design of human and industrial systems to ensure that humankind’s use of natural resources and cycles does not lead to a diminished quality of life due to losses in future economic opportunities or adverse impacts on social conditions, human health, and the environment (Mihelcic et al., 2003).

The Three Pillars of Sustainability

  • People: Fair practices for all people, ensuring no exploitation of the interests of separate parties based on money, status, or growth.
  • Planet: Responsible management of renewable and non-renewable resources while actively reducing waste.
  • Profit: Financial benefit enjoyed by the majority of society.

Demands for Sustainable Engineering

  • Society requires infrastructure that supports economic, environmental, and societal sustainability.
  • The ASCE Code of Ethics states that engineers “shall strive to comply with principles of sustainable development.”
  • Sustainability calls for mastery of knowledge beyond that required for professional licensure.

Engineering Design Criteria

Traditional Engineering Design Criteria:

  • Function
  • Cost
  • Safety

Sustainable Engineering Design Criteria:

These include the traditional criteria plus:

  • Impact on people (society)
  • Impact on the planet (environment)

Life Cycle Assessment (LCA)

Life Cycle Assessment (LCA) is a technique used to quantify the environmental impact of a product from raw material acquisition through end-of-life disposition (cradle-to-grave). Life Cycle Thinking supports recognizing and understanding how both consuming products and engaging in activities impact the environment from a holistic perspective. This means life cycle considerations take into account the environmental performance of a product, process, or system from the acquisition of raw materials to refining those materials, manufacturing, use, and end-of-life management.

Four Phases of a Life Cycle Assessment (ISO 14040, 14044)

  1. Step 1: Goal Definition and Scoping. Identify the LCA’s purpose, the products of the study, and determine the boundaries (what is and is not included in the study).
  2. Step 2: Life Cycle Inventory. Quantify the energy and raw material inputs and environmental releases associated with each life cycle phase.
  3. Step 3: Impact Analysis. Assess the impacts on human health and the environment.
  4. Step 4: Report Results. Evaluate opportunities to reduce energy, material inputs, or environmental impacts at each stage of the product life cycle.

LCA Phase Details

Goal Definition:

  • Intended application of the study
  • Intended audience

Scope Definition:

  • Identify the product system to be studied
  • Define the functional unit
  • Define the boundaries of the product system
  • Identify assumptions and limitations of the study
  • Select impact categories to be included.

Functional Unit:

  • The functional unit is a measure of the function of the studied system.
  • It provides a reference to which the inputs and outputs can be related.
  • It enables comparison of two essentially different systems.

Step 2: Life Cycle Inventory

  • Highly data-intensive.
  • Detailed mass and energy balances are performed over the life cycle.
  • Advantages: Measures data and defines baseline metrics of life cycle processes.
  • Challenges: Assumptions are made when data is unavailable.

Step 3: Impact Assessment

  • Converts the inventory into impact categories or mid/end points which explain the environmental effect.
  • Impact categories may include: carcinogens, respiratory organics and inorganics, climate change, radiation, ozone layer depletion, ecotoxicity, acidification/eutrophication, land use, mineral resource depletion, and fossil fuel depletion.
  • Weights can be applied to impact categories.

Step 4: Report Results

Life cycle interpretation involves evaluating the findings of the inventory analysis or impact assessment in relation to the goal and scope of the study to reach conclusions and recommendations.

  1. Identify significant issues.
  2. Evaluate results for completeness, consistency, and sensitivity of the data.
  3. Draw conclusions and make recommendations consistent with the goal and scope of the study.