Full footprint, not one number

Carbon, water, land, materials, toxicity and duration within the same framework.

CO2 is vital, but it's not alone

A single figure never tells the whole story

Carbon dioxide is, rightly, the most cited measure when evaluating an energy technology's environmental impact, because climate change is one of the largest-scale, most urgent environmental problems on the planet. But reducing a product's or technology's entire environmental evaluation to that single carbon figure systematically leaves out other impact dimensions that can turn out to be decisive depending on the specific context: freshwater consumption, physical land occupation and transformation, particle emissions affecting local air quality, the toxicity of certain substances to aquatic or terrestrial life, soil and water acidification, eutrophication of water bodies from excess nutrients, consumption of scarce minerals, and the generation of waste that requires its own subsequent management. A complete environmental evaluation follows all these dimensions at once, not just the most publicised one.

Improving one dimension can worsen another

One of the most important lessons of looking beyond CO2 is that different environmental-impact dimensions do not always improve together: a technology can substantially reduce its carbon emissions and, at the same time, increase its water consumption, its land occupation, or its dependence on minerals whose extraction carries its own specific environmental and social cost. This does not mean all options are equivalent to each other, nor that genuine improvements don't exist: it means no real energy decision can be responsibly evaluated by looking at a single isolated figure, however important that specific figure may be.

Lifecycle analysis organizes the comparison, it doesn't automatically resolve it

Lifecycle analysis is the standard methodological tool for systematically tracking every material and energy input, and every emission and waste output, across a product's or technology's entire journey: from extracting the original raw materials to the end of its service life. This tool helps enormously in organizing a comparison that would otherwise be impossible to structure rigorously. But it does not, on its own, produce an automatic truth or an objective figure free of any assumption: the final result depends critically on exactly where the analysis boundaries are drawn, on the quality and source of the data used, on the assumed service life of the equipment analyzed, on the specific geographic location considered, on how impact is allocated between different co-products when a single process generates several at once, and on the end-of-life recycling scenario assumed for the calculation. Two technically correct lifecycle analyses can reach different conclusions about the same product simply by having chosen different methodological assumptions at any of these points.

Four phrases that should spark curiosity, not automatic trust

Several common expressions in environmental marketing for products and technologies, while they may be literally true within a specific analysis boundary, frequently hide important assumptions worth making explicit before accepting them without question. "Zero emissions" should always specify whether it refers only to the product's use phase or to its entire lifecycle. "Biodegradable" depends critically on the specific decomposition conditions and on exactly what happens to the chemical additives incorporated into the material. "100% recyclable" describes a technical possibility of the material, it does not guarantee that a collection system and industrial recovery capacity actually exist at the necessary scale. And "carbon neutral" can mean very different things depending on whether it is achieved through a real physical reduction in emissions, through purchasing electricity certified as renewable, or through offsetting emissions somewhere else entirely on the planet — three mechanisms with very different implications that the same label can be hiding. A specific label can be perfectly true within a very narrow analysis boundary; the job of whoever reads it is precisely to open up that boundary before accepting the full claim.

How to read a green claim

Look for the exact functional unit being compared — for example, passenger-kilometer or kilowatt-hour delivered —, the assumed service life, the geographic location, the date of the analysis, the electricity mix considered, and the specific alternative it is being compared against. Check whether the calculation includes the product's infrastructure, maintenance and end of life, or only its operating phase. Be wary of results presented with many decimal places of precision but no uncertainty range around them.

Then ask about the specific case's local priorities. In an already water-scarce river basin, water consumption may dominate the right decision; next to an especially vulnerable population, airborne particles or noise may be the priority; on a grid still heavily dependent on fossil fuels, carbon may be the deciding factor. Sustainability does not consist of adding up harms of different, incomparable natures into a single magic final figure: it consists of making them visible separately so a decision can be made with informed judgment.

Don't accept any label without opening up its boundary

"Zero emissions," "biodegradable," "100% recyclable" and "carbon neutral" can all be true within a very narrow analysis boundary. Asking what is left outside that boundary is always the step to take before accepting the claim as a complete description.

The numbers, with their source

Sixteen impact categories, not just one

The European Commission's Product Environmental Footprint (PEF) method, the European reference framework for measuring a product's full environmental impact, defines 16 distinct impact categories that must be evaluated together: climate change, ozone depletion, human toxicity (cancer and non-cancer), particulate matter formation, ionizing radiation, photochemical ozone formation, acidification, eutrophication (terrestrial, freshwater and marine), land use, water resource depletion, and mineral and fossil resource depletion, among others. None of these 16 categories replaces the others: a product can score excellently on climate change and, at the same time, score poorly on water resource depletion or toxicity.

Source: European Commission — Product Environmental Footprint method.

Two ISO standards underpin the global methodological framework

Lifecycle analysis as a discipline is formalized internationally by the ISO 14040 (principles and general framework) and ISO 14044 (specific requirements and guidelines) standards, which explicitly require defining the study's goal and scope, including the system boundaries analyzed, before collecting any data — precisely because, as the standards themselves acknowledge, a lifecycle analysis's final result depends critically on those initial methodological decisions.

Source: ISO — 14040 and 14044.

What this table is missing

No methodological standard, however rigorous, removes the need to compare two studies' specific assumptions before directly comparing their numerical results: two lifecycle analyses that equally comply with ISO 14040/44 can reach different conclusions about the same product if they differ in system boundaries, assumed service life, or the end-of-life scenario considered.

Sources