Silicon sits quietly behind much of the modern world.
Solar photovoltaic cells, semiconductors, power electronics, data centres and artificial intelligence all ultimately depend on highly purified silicon.
Yet producing silicon begins with one of the most abundant materials on Earth — silicon dioxide, or quartz — and requires a substantial amount of energy and a reducing agent to remove its oxygen.
Traditionally, carbon performs that role.
This raises an interesting question:
If silicon is becoming increasingly important to the clean-energy and digital economy, can we rethink what happens to the carbon used in producing it?
Quartz is abundant. Producing silicon is not simple.
At its simplest, silicon production involves removing oxygen from:
SiO₂
to obtain:
Si
That transformation requires considerable energy.
Conventional silicon production uses carbonaceous reducing materials at very high temperatures. Carbon combines with oxygen from the silica and ultimately leaves the process predominantly as carbon-containing gases.
The conventional carbon pathway is therefore largely linear:
Carbon → reduction → carbon-containing gas → atmosphere
But does it always have to remain that way?
What if carbon became part of a cycle?
At Clean Energy and Water Technologies, we have been developing a broader concept called Carbon Recycling Technology (CRT).
The underlying philosophy is straightforward:
Carbon does not necessarily have to be used once and discarded.
If carbon-containing gases can be captured, converted and returned to the process, carbon begins to behave more like a circulating process material.
Renewable energy then supplies the continuing energy required to maintain that circulation.
This distinction is fundamental.
Carbon can circulate. Energy must continually be supplied.
Methane provides an interesting possibility
Methane contains both carbon and hydrogen:
CH₄
With appropriate energy input, methane can be separated conceptually into:
CH₄ → C + 2H₂
This creates two potentially valuable streams:
- carbon that may participate in metallurgical processing; and
- hydrogen that can become part of the wider energy and chemical system.
Now consider the carbon-containing gases produced during silicon manufacture.
Rather than automatically treating captured CO₂ as a waste stream requiring disposal, another pathway becomes possible:
CO₂ + renewable H₂ → CH₄ + H₂O
The methane can potentially return to the process.
The carbon begins to circulate.
The carbon atom has no label
We often distinguish between fossil carbon, biogenic carbon, captured carbon and atmospheric carbon.
Those distinctions are extremely important when accounting for climate impact and determining whether new carbon is being introduced into the active carbon cycle.
But chemically, the carbon atom itself does not carry a label.
The engineering question is therefore:
Where did the carbon come from — and where does it go next?
If fresh fossil carbon continually enters a process and its CO₂ continually leaves for the atmosphere, emissions accumulate.
If instead a defined carbon inventory can be captured and repeatedly circulated within an engineered system, the architecture becomes fundamentally different.
That is the principle we are exploring with CRT.
Silicon presents a particularly interesting opportunity
The silicon value chain brings together several major themes of the energy transition:
renewable electricity, high-temperature processing, hydrogen, carbon, heat recovery and advanced materials.
Rather than optimising each independently, perhaps they can increasingly be considered as one integrated system.
Our engineering sequence is:
Mass balance → Energy balance → Heat integration → Equipment efficiency → Dynamic optimisation
Every carbon atom should have a destination.
Every hydrogen molecule should have a purpose.
And every recoverable unit of thermal energy should be considered before it is rejected as waste heat.
From silicon to the wafer
Producing metallurgical silicon is only the beginning.
Semiconductor and photovoltaic wafers require additional purification, polysilicon production, crystal growth, slicing and finishing. Each stage has its own energy, material and environmental footprint.
Therefore, it would be premature to describe a silicon wafer produced through such a developing pathway as completely “emission-free.”
The more meaningful objective is:
Can we progressively design a silicon value chain in which direct carbon emissions are minimised, process carbon is recycled, and the continuing energy input increasingly comes from renewable sources?
If that can be demonstrated first at silicon-production level, the boundary can subsequently be expanded toward polysilicon, ingots and ultimately wafers.
A different philosophy for industrial decarbonisation
Much of the energy transition understandably focuses on eliminating fossil fuels.
There may be another complementary engineering principle worth considering:
Do not automatically eliminate carbon from every industrial process. Eliminate the need to continuously extract, consume and emit new carbon.
Capture it.
Account for it.
Recycle it.
Supply the required energy renewably.
For silicon — a material that will help build the renewable-energy and AI infrastructure of the future — that seems a question worth investigating.
From quartz to silicon, can carbon become part of the cycle rather than the emission?
That is the question we are beginning to explore through Carbon Recycling Technology.
