As a gemologist, I’m regularly asked whether a lab-grown diamond is more sustainable than a natural one. But the answer is complex, and can’t be captured in terms like “eco-friendly” or “sustainable.”
From 27 September, the European EmpCo Directive will prohibit companies from making generic sustainability claims without substantiation, an important step against greenwashing. But for anyone looking to buy a diamond, little will actually change: the key information is still missing.
It isn’t the diamond’s origin that has the greatest climate impact, but the energy used to produce it. And that is almost never measured.
Lab-grown and natural diamonds are chemically, physically and optically identical. The difference lies in how they form: one grows in a reactor over a matter of weeks, the other in the earth’s mantle, over a span that can reach billions of years. Lab-grown is supposed to be sustainable, mining is not. But the numbers don’t hold up that contrast.
A large share of lab-grown diamonds are produced using the Chemical Vapour Deposition process: a crystal grows in a reactor that draws power continuously. On a grid running mainly on coal, emissions can rise to several times what natural diamonds produce. On a grid powered by renewable energy, that same diamond can, according to the Trucost report, drop to roughly 17 kilograms of CO2-equivalent per polished carat.
Mines also vary considerably, depending on the energy used, ore quality and mine size. A mine in an accessible area with access to the local electricity grid has a lower per-carat consumption than a remote mine.
The previously mentioned Trucost/S&P Global study is frequently cited and was commissioned by the Diamond Producers Association. For 2019, it calculated emissions of 511 kilograms of CO2-equivalent per polished carat for lab-grown diamonds, compared with 160 kilograms for natural diamonds. But the commissioning party has a vested interest, and independent data on the lab-grown sector remains scarce. The figures are therefore difficult to read as plain fact.
Major mining companies such as De Beers and Rio Tinto acknowledge that climate impact varies by mine and energy source, and have set their own decarbonization targets for 2030 and 2050. Emissions from heavy machinery can’t simply be reduced by switching to green electricity, whereas that is possible with a CVD reactor.
That transparency about the origin of energy is not a utopian idea became clear to me during a visit to the German producer Nevermined. There, I was able to follow the production process from seed crystal to rough end product, including the source of the electricity used (solar, wind and hydro power). The diamonds produced are certified under SCS-007-1, which sets requirements for sustainability disclosure. So this kind of information can, in fact, be made available.
Calling all natural diamonds unsustainable is just as much of a simplification as calling every lab-grown diamond sustainable. Manufacturers on the lab-grown side readily use terms like “small footprint,” usually without any verifiable figures to back them up. After 27 September, little will change: the EmpCo Directive mainly targets vague claims, not the absence of data. A producer who stays silent rather than making a hollow claim is technically compliant with the law. That does nothing to help the consumer, and transparency remains a matter of choice.
It’s time for retailers to ask different questions. Not: is this diamond lab-grown or natural? But: how was it made, and with what energy? Only then will sustainability in the diamond sector start to mean something.
Laetitia Ruchtie is a gemologist and lab-grown diamond specialist.
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