First, let me clarify that this isn't an attack on the lab-grown diamond industry. Lab-grown diamonds serve a specific market and make diamonds more accessible to a broader audience. This article is directed against those who falsely market these products as ethical and ecological saviors for their own benefit. As a material engineer and diamantaire, let me explain why.

As diamanteers, it's our responsibility to ensure consumers understand what they are buying. This way, they can purchase products confidently, at the right price, and for the right reasons. Our industry is built on trust, and maintaining that trust requires us to inform consumers as best we can. This is why I wrote this article.

So, let's talk about making diamonds artificially. Good news! They only consist of carbon, so making them should be easy, right? Unfortunately, chemistry proves us wrong. There are numerous (useful!) forms of pure carbon, with the easiest being graphite. Graphite is what we find inside a pencil. But, to create a diamond, we need to rearrange the molecular connections, making it a bit tighter to form the same lattice or crystal as in a diamond.

We just need to use chemistry and push it hard together, and heat it up a bit. Again, unfortunately, unless we are 150 km deep in the earth’s crust, this isn't so easy. I wouldn't recommend going there because you'd be pulverized under immense pressure and cooked at 4000 degrees Celsius.

Did you know you can vaporize a diamond? All you need to do is to provide an oxygen rich atmosphere and heat them up to about 700 degrees celcius. Then the following reaction occurs:

C + O2 -> CO2

This unfortunately is an irriversible reaction. This means that we cannot strip the oxygen from a CO2 molecule and arrange the carbon in a diamond crystal structure!

Since the mid-1900s, people have been trying to recreate the conditions from deep below the surfoce in a lab or factory environment. Technological developments throughout the years in process and material science have made it possible. To date, we have two processes:

1. High-pressure high-temperature (HPHT): Recreating the conditions where natural diamonds are formed on a small diamond seed with a carbon source like methane.

2. Chemical vapor deposition (CVD): Using a carbon source like methane (CH4) and energizing this gas with a lot of energy so pure carbon is formed and two molecules of hydrogen (H2) are released. Under the right conditions, the carbon molecule attaches itself to the lonely diamond seed.

A noteworthy remark is that after the CVD process, the grown crystals are commonly treated with HPHT treatment to improve their color and clarity. We won't compare what's better or not; that’s another discussion. But knowing that, we need to also consider the energy of the HPHT treatment afterward because you need a lot of pressure and heat for this. And this energy needs to come from somewhere, preferably at a very low price.

This brings us to the production sites or factories where synthetic diamonds are produced. This is typically done in countries with lower wages and where energy comes from cheap or easy sources like coal-fired plants. Or where it's not possible to find out precisely where this energy is coming from.

Let’s compare the CO2 potential of a mined diamond and a synthetically created diamond. At the time of writing and using the openly available resources, the following estimates will be used. The true potential depends on different mining techniques, where the diamond is used, and which energy source is provided to the mine (coal or natural gas), which fuel trucks use, etc. Considering the above and what was written in a previous research paper, the energy used to make a 1-carat synthetic diamond for each specific process is:

• HPHT: 28 – 245 kWh per carat polished produced.

• CVD: 77 – 145 kWh per carat polished produced.

• Mining: 96 – 150 kWh per carat polished produced.

The preferred process for synthesizing a diamond lies in the quality of the diamonds and cost related to each process to get the desired quality. So ideally from a consumer perspective, we have a big, polished diamond, which is a colorless DEF grade with the highest clarity (IF – internally flawless to VVS – very very slightly included). The last C, the cut, can of course not be controlled while growing the crystal. Based on what we know to date:

• Size: It is easier to grow bigger crystals using the CVD method.

• Clarity: Due to the fast-growing process of the CVD method, generally these crystals are of lesser quality in clarity with regards to HPHT.

• Color: CVD produced crystals often have brown undertones due to carbon not fully arranging or being trapped in the crystal lattice.

One would assume that to have the most beautiful diamond, every company would use the HPHT process, right? Well, sadly not. HPHT is a lengthy and costly process, and this is a profit-driven industry. To maximize profits and have higher output of carats produced, most synthetic diamond producers use the CVD method. So currently, with modern technology, the most current technology for synthetic diamond production is CVD-growing with an HPHT-curing treatment afterward to cure the crystals and improve the color and clarity.

So, an assumption would be that we add the most modern HPHT-installation energy use (the lowest) to the CVD energy use range. So, for a polished synthetic diamond, we consider the following energy usage:

• Synthetic diamond = CVD + HPHT treatment: 105 – 173 kWh per carat polished produced.

Now we need to convert this into CO2 produced per kWh consumed. Considering the following values for CO2 produced per resource:

• 1.1 kg of CO2e produced per kWh for Coal energy.

• 0.6 kg of CO2e produced per kWh for Natural gas.

• 0.8 kg of CO2e produced per kWh for Oil.

Now we will assume that most of the synthetic diamonds are produced in the Asian continent and the energy mix there would be 50/50 Coal and Natural gas, the average CO2e produced per kWh is 0.85 kg per kWh. The next assumption is that on the remote locations of operations of diamond mines most of the energy will come from fuel oil, so 0.8 kg of CO2e produced per kWh.

So, the ranges of CO2 produced based on energy usage will be:

• 1 carat Synthetic polished: (105 – 173 kWh) * 0.85 kg CO2e/kWh = 89 – 147 kg of CO2e produced

• 1 carat Natural polished: (96 – 150 kWh) * 0.8 kg CO2e/kWh = 77 – 120 kg of CO2e produced

However, the impact of mining operations on the environment goes further beyond energy use. Looking at open-source data [1], and leaving out the extreme values, the CO2 produced to mine and bring to market a 1-carat natural diamond is:

• 125 - 400 kg CO2e/carat polished

This range can vary depending on location and energy sources. It has been proven that consumers can change company behaviors when talking about environmental impact. With recent socio-economic developments, traceability plays a big role in the diamond industry and consumers can find out where their diamond comes from, and maybe also link CO2 data per carat produced in this traceability passport!

Lastly, on carbon emissions, diamonds often come from developing nations, which initially have a more carbon-intensive economy to grow and develop their nation. Just as developed nations have gone through this process, it would be, from a certain perspective, unfair to impose carbon emissions restrictions on nations that depend on this important revenue of diamond exports to developed nations.

Let's not forget that energy is not always readily available in the same places where diamond deposits are found. Let alone to install a grid with renewable energy sources in that location. For example, northern territories in Canada, the mountains of Lesotho, huge areas of sand dunes in Namibia, or the widespread distances where alluvial deposits are found.

Back to making the true ecological diamond guarantee of only using renewable energy sources. This means we will also certify this so we can show consumers that we are speaking the truth.

Sidenote: hardly any labgrown producer can provide a certificate that verifies that their process is carbon neutral or ecologic.

Now let’s have a look at our basic materials or chemicals, which need to come from renewable sources as well with the least amount of environmental impact.

In the CVD process, the materials used to feed the reactor are ultra-high pressure H2 (UHP) and high purity CH4 in a ratio of 99:1. This ensures that all the carbon sticks to the diamond crystal and no CH4 is trapped inside the diamond crystal. Several factors need to be considered:

• Energy to produce H2.

• Energy to put it under ultra-high pressure.

• Source of CH4 or natural gas. This plays an important role since many relevant studies have also measured the impact of CH4 leakage into the atmosphere because it is a potent greenhouse gas.

• Purification process to get high-purity CH4. (energy + leakage).

So, let’s say we want to go a step further and create a carbon-negative diamond. There are a few ways to get carbon from chemicals and convert it to pure CH4. But let’s be honest; the easiest and most understandable marketing trick would be to say that we would be removing CO2 out of the air. It is also in line with the narrative of carbon capture and the projects that are set up around the world to either capture emissions from power plants or few projects that intend to harvest carbon out of the air. The goal here is to store it indefinitely in rocks or solid composite materials. But it would be cool if you could store it in a diamond.

Currently, the most common industrial way to capture CO2 is by letting flue gases flow through a MEA mixture (of low concentration). This chemical then binds to and absorbs the CO2 from the air. In the next step, we need to release the CO2 back from the mixture so we can further process it so it doesn’t get released back into the air. Luckily, this is easy, and we ‘just’ need to heat up the mixture to release the CO2. This is where the big challenge of carbon capture lies because the MEA is present in a mixture with water in low concentrations, a lot of heat is wasted heating up the water as well. If you do not get the heat or energy to heat this mixture up from a renewable energy source, then your whole process will become carbon negative. That is also the reason why a carbon capture project in Iceland is a very interesting case because you can utilize geothermal heat from underground there to release the CO2 again and further process it.

As we need methane for our synthetic diamond production and we start with CO2, the Sabatier reaction is needed. The Sabatier reaction or Sabatier process produces methane and water from a reaction of hydrogen with carbon dioxide at elevated temperatures (optimally +300 °C) and pressures in the presence of a nickel catalyst.

CO2 + 4 H2 -> CH4 + 2 H2O

Where we see the remaining water in this gas mixture needs to be removed as well to further use it. This whole process in its turn needs to be performed carbon-neutral to maintain carbon negativity over the whole process. This can be done either by offsetting the energy usage or by processing the CO2 via another biological pathway.

Looking at biological pathways, this allows for more direct methods to create methane from nature. There are two possible ways to create methane from bacteria:

1. There are lots of bacteria in natural mixtures (water – biofilms) that can and will produce methane in atmospheric conditions. However, this metabolic pathway is very slow and thus would only generate low amounts and low concentrations of methane. This is not economical and would be difficult to create the base products for the gas mixture used in diamond synthesis.

2. Biotechnology advancements have led to the discovery of methanogenic bacteria. These are bacteria that can produce methane as a byproduct of their metabolic pathway. Within this group, there is a special type of organism that will metabolize hydrogen, and with the presence of CO2, it can create the CH4 we need for creating our synthetic diamonds. However, these organisms thrive in environments that are low in oxygen and therefore cannot be used to extract carbon dioxide from the atmosphere directly.

If someone really wants to use CO2 from the air to produce a synthetic diamond, the only reasonable way to use bio-organisms to create methane is to capture CO2 directly from the air and then feed it to methanogenic organisms. But it would be a lot easier when an alternative CO2 source is used, e.g. waste water. Adding everything up gives us a very complicated and costly process to capture a negligible amount of carbon dioxide from the air and store it in a diamond you could wear.

Some prices to compare at the time of writing (May 2024) for a 1-carat F-color VVS clarity diamond:

• Natural diamond: 7,500 USD

• Synthetic diamond: 200 USD (wholesale price – production price is around 30 – 50 USD)

• Synthetic diamond (so-called carbon neutral or negative): 4000 USD

Now, let's delve deeper into the amount of carbon stored in a diamond and compare it to real-world examples of carbon emissions. A 1-carat diamond contains approximately 0.2 grams of carbon. However, if the carbon source were carbon dioxide, one could store about 0.734 grams of carbon, accounting for the weight of the two oxygen atoms in the CO2 molecule (which is approximately 0.534 grams). This consideration is crucial as it provides insight into the actual carbon storage potential of diamonds derived from carbon dioxide.

To put this into perspective, let's examine some common items and their carbon footprints:

• 1 cup of tea: emits about 40 grams of CO2.

• 1 glass of wine: contributes approximately 300 grams of CO2.

• 1 plastic bag: releases around 33 grams of CO2.

• 1 hour of mobile phone use: generates about 172 grams of CO2.

• 1-way flight from London to Paris: emits a staggering 40,000 grams of CO2.

• 1 hot shower lasting 10 minutes: produces roughly 2,000 grams of CO2.

These examples highlight the significant variation in carbon emissions associated with everyday activities and products. When juxtaposed with the carbon storage capacity of diamonds, it becomes evident that the impact of a single carbon-negative diamond, while symbolically significant, is relatively small in the grand scheme of carbon emissions.

In conclusion, several key points emerge from this analysis:

• Comparative Environmental Impact: In ideal circumstances, both synthetic and natural diamonds have a comparable environmental impact in terms of CO2 equivalent. However, the impact of mining operations can vary greatly depending on various factors such as deposit type, mining methods, and energy sources used. Therefore, it's reasonable to infer that a synthetic diamond would emit significantly less CO2 per carat produced compared to a natural diamond.

• Challenges of Decarbonization: Decarbonizing the synthetic diamond industry presents challenges due to economic feasibility and the geographical location of current production facilities. Despite advancements in renewable energy technologies, transitioning to fully sustainable practices remains a complex endeavor.

• Ethical Considerations: Ethical considerations are paramount in the diamond industry, with factors such as fair labor practices and environmental stewardship playing pivotal roles. Both natural and synthetic diamond production involve industrial processes, often in developing nations. However, initiatives aimed at providing a view on traceability and ethical sourcing to the consumer are gaining momentum.

• Consumer Choice: As consumers, it's essential to make informed choices that align with our values and priorities. While the allure of a carbon-negative diamond may be enticing, it's crucial to weigh its environmental impact against alternative actions that may yield more significant benefits. This includes supporting initiatives focused on carbon offsetting, ethical sourcing, and sustainable practices within the diamond industry.

In light of these considerations, my advice to consumers is to approach diamond purchasing with a critical eye and a commitment to sustainability. Instead of solely focusing on the carbon neutrality of individual diamonds, consider the broader context of environmental stewardship and social responsibility. By engaging with suppliers, advocating for transparency, and supporting initiatives that prioritize sustainability, consumers can drive positive change within the diamond industry and contribute to a more equitable and environmentally conscious future.

Some additional information to consider:

• You can offset your carbon emissions by buying a carbon offset online at 10 - 50 USD per tonne of CO2. This money is used to fund initiative to fight climate change.

• Mining company Petra Diamonds has recently entered into long-term Power Purchase Agreements for the procurement of renewable energy for its Cullinan and Finsch Diamond Mines in South Africa. This is a great example and I hope more mining companies will follow!

If you have any further questions or comments, please don't hesitate to reach out. I'm here to provide additional insights and assistance as needed.