The triple bottom line (TBL) is a sustainability framework that evaluates a design or business decision using three dimensions: people, profit, and planet. A sustainable solution should create social and environmental value while remaining economically viable.
How the Triple Bottom Line Works
TBL expands evaluation beyond the traditional financial “bottom line.” In C2.1 Design for sustainability, designers use it to examine impacts across a product’s life cycle, including material extraction, manufacture, distribution, use, and disposal.
| Dimension | Meaning in design | Example considerations |
|---|---|---|
| People | The social and ethical effects on users, workers, and communities | Worker safety, fair wages, accessibility, inclusive design, and user well-being |
| Profit | The economic viability of producing and selling the solution | Manufacturing costs, pricing, durability, market demand, and long-term business survival |
| Planet | The effects on natural systems and resources | Energy use, emissions, waste, renewable materials, repairability, and recyclability |
For example, consider a company redesigning an electric kettle. Using recycled metal and making components replaceable may reduce waste and resource consumption, supporting planet. Safe working conditions and an accessible handle support people, while efficient manufacture and a longer-lasting product can reduce costs and strengthen customer loyalty, supporting profit.
The three dimensions are interconnected, but trade-offs can occur. A biodegradable material may reduce environmental impact but cost more than a conventional polymer. The designer must therefore justify whether its environmental and social benefits outweigh the increased cost.
A common misconception is that profit makes TBL purely business-focused. Profit instead recognizes that a design must be economically sustainable: if it cannot be produced, maintained, or sold viably, its social and environmental benefits may not continue.
Exam Technique
When asked to explain or evaluate a sustainable design, address all three TBL dimensions and connect each one to a specific design feature or life-cycle impact. For evaluation, identify trade-offs and reach a justified conclusion rather than simply listing people, profit, and planet.
