Context
A paradigm shift, and where it came from
Not long ago, engineering design concentrated on in-service requirements — function and strength. Today a design must also satisfy environmental requirements and account for what happens to the product at end of life. Sustainable design is a direct consequence of tighter environmental regulation, pressure on natural resources, limited landfill, hazardous material controls and health concerns.
It addresses two distinct phases. During life, a product must meet environmental and energy constraints: minimising pollution and greenhouse contribution, with measures such as carbon dioxide emission, water pollution and air pollution, while consuming as little energy as possible. After life, the question becomes what happens to the product once its useful life ends.
Engineering design has always tracked societal priorities. When manufacturing cost dominated in the 1980s and 1990s, design for assembly, design for manufacture and concurrent engineering emerged and were widely adopted; six sigma followed as quality became the focus. As environmental awareness rose, the same adaptive move produced design for sustainability. The pattern is consistent: the design process absorbs whichever constraint society has decided matters.
Principles
Design guidelines
Guidelines for sustainable design continue to evolve and remain largely qualitative. The following set is in common use.
A — Minimise energy consumption
Design products that need less energy to operate. Hybrid drivetrains, extended battery life and energy-rated appliances are the visible examples.
B — Use safe materials
Prefer materials with low environmental impact during processing and after disposal: non-toxic, recyclable, low-energy to process, and drawn from recyclable sources where possible.
C — Use efficient processes
Select manufacturing processes that complete quickly, use less equipment energy, and generate minimal pollution.
D — Reduce the carbon footprint
The total greenhouse gas emissions attributable to the product, expressed as carbon dioxide equivalent — the word equivalent covering methane, carbon monoxide and the other greenhouse gases. Footprints can equally be defined for a company, an organisation or a nation.
E — Design for disassembly
A product that cannot be taken apart cannot be repaired, remanufactured or sorted for recycling. Fastener choice and joint design decide this.
F — Design for longevity
Extending service life spreads the embodied impact of manufacture over more years of use, which is frequently the largest single available gain.
Method
Life cycle assessment
LCA is commonly described as cradle-to-grave analysis. Some products are assessed on a narrower basis — cradle-to-gate, for instance — where full coverage is impractical.
- 1 — Raw material extraction Methods differ by material: timber is planted, grown and harvested; metals are mined as ore; plastics begin with drilling and pumping oil.
- 2 — Material processing Conversion of raw materials into engineering materials. Timber is cleaned and sawn into slabs; ore is converted to steel and bauxite to aluminium; oil is converted to polymer feedstock.
- 3 — Part manufacturing Processing into finished parts. Timber becomes furniture; steel becomes columns; aluminium becomes cans; injection moulding and stamping convert plastics into products.
- 4 — Assembly Finished parts combined into the final product.
- 5 — Distribution Packaging and transport to the point of sale.
- 6 — Use The in-service phase, where energy consumption and consumables accumulate.
- 7 — End of life Disposal, recovery or recycling — and recycling feeds material back to stage 2.
Successful products are developed by integrating LCA directly into the engineering design process rather than running it as a compliance exercise after the design is fixed. By the time the geometry is frozen, the material has been chosen and the largest share of the environmental outcome has already been determined.
Quantification
The impact metric
Environmental impact arises from three categories: materials, methods and systems. Materials associate with product design; methods with manufacturing processes; systems with transport and with use during service and at end of life.
Material selection is the decisive factor, because it constrains the other two. Choosing metal or plastic determines whether the part will be machined or moulded. It affects logistics across every phase, from moving raw material to plant, to shipping the finished product to consumers — some materials are lighter or faster to move, and the carbon footprint follows. And it governs the end-of-life fate of the product entirely.
A fifth factor, covering broader human and ecosystem toxicity, appears in fuller assessments. The CAD modules discussed below typically report the first four.
Framework
Standards and implementation
Implementation of LCA is guided by ISO. The 14040 and 14044 pair set out the principles and framework for life cycle assessment; 14062 addresses greenhouse assessment; 14025 covers Type III environmental declarations and national inventory reporting.
The method provides a systematic approach to identifying, quantifying and assessing environmental impacts through the life cycle of a product, process or activity, accounting for material and energy use and for releases to the environment from cradle to grave. Its stated purposes are to identify hot spots of potential impact, to compare aspects of competing products or processes, and to establish a baseline for further comparison.
Life cycle assessment does not embody every approach that environmental decision making calls for, and is normally used alongside other instruments such as risk assessment. Its application also demands substantial effort: understanding the principles, quantifying the impact factors, and collecting data across many materials, processes, transport modes and national regulatory regimes. That data burden is the practical reason the work is usually done with software backed by a commercial database.
Working method
Sustainable design as a design activity
The concepts assemble into an ordered procedure a designer can actually execute.
- Step 1 Create the part design as normal.
- Step 2 Assign a material.
- Step 3 Select the manufacturing processes that follow from that material.
- Step 4 Select the system — transport, and the region of the world where the part will be used.
- Step 5 Calculate the impact factors to establish a baseline.
- Step 6 Repeat steps 2 to 5 with alternative materials and compare against the baseline.
- Step 7 Select the alternative that meets functional requirements at the lowest environmental cost.
Regional selection matters more than it first appears. Different regions operate under different environmental regulations and different energy mixes, so the same manufacturing process carries a different footprint depending on where it is performed. A design decision that looks neutral in one jurisdiction can be significant in another.
Software
Sustainability tools in the CAD environment
Sustainability tools matter most when they are quantitative, because that is what allows practising designers to evaluate real alternatives rather than express preferences. Two families are relevant: modules embedded in the CAD system, and dedicated life cycle software backed by large commercial inventories.
Embedded CAD modules
Typically offered in two tiers. The entry-level module analyses parts only, ships with the core CAD licence, and reports the four principal impact factors. The full module adds assembly analysis, configuration handling, more impact factors and expanded reporting. The relationship mirrors that between the introductory and full finite element modules described in Part 17.
Dedicated LCA software
Specialist packages developed over large numbers of consulting engagements, carrying extensive inventories of materials, processes and transport modes. CAD-embedded modules commonly license their inventory data from these sources.
How the embedded module works
Environmental impact is measured against four inputs: the material used, the manufacturing process and its region, the use region, and the end-of-life disposition. The designer selects from built-in libraries of materials, manufacturing processes and transport modes, plus a library of manufacturing regions. A dashboard displays and compares results, and reports can be generated covering both the impact factor calculations and the resulting design.
The useful output of an in-CAD sustainability study is comparative: this material against that one, this region against another. Treating an absolute number from a simplified module as a certified footprint overstates what the tool can support. Use it to rank alternatives during design, and commission a full assessment when a published claim is required.
Key takeaways
- Sustainable design covers both the in-service and the end-of-life phases, and arrived as design absorbed a societal constraint, exactly as DFM and six sigma did before it.
- Guidelines remain qualitative: less operating energy, safer materials, efficient processes, smaller footprint, disassembly and longevity.
- Impact arises from materials, methods and systems — and material selection constrains the other two.
- The four core impact factors are carbon footprint, energy consumption, air acidification and water eutrophication.
- ISO 14040 and 14044 set the LCA principles and framework; the effort is dominated by data collection.
- Work the seven-step procedure and compare alternatives against a baseline — region of manufacture and use materially changes the result.
- Use embedded CAD modules comparatively during design; commission full assessment for published claims.
Series
Continue the pathway
The SOLIDWORKS Design Approach series works through computer aided design as an engineering discipline, from first principles to manufacture.