Follow the Carbon

Follow the Carbon A simpler way to think about decarbonisation, defossilisation and the energy transition Climate and energy discussions have developed an increasingly complex vocabulary. Net zero. Decarbonisation. Electrification. Renewable energy. Green hydrogen. Carbon capture. Carbon removal. Carbon credits. Circularity. Each describes something important. But sometimes the terminology can obscure a simpler physical question: Where does the carbon come from, where does it go, and what happens to it next? Perhaps one of the simplest ways to understand the transition is therefore: Follow the carbon. The linear carbon economy Much of the modern energy system was built around a fundamentally linear material flow: geological carbon → extraction → processing → fuel or product → CO₂ Coal, oil and natural gas have accumulated underground over geological timescales. We extract them, use their energy and molecular value, and transfer part of that geological carbon into the active atmosphere–biosphere–ocean system. The problem is therefore not that carbon exists. Carbon is fundamental to life, fuels, chemicals, materials and natural ecosystems. The important question is the flow of additional carbon between reservoirs. For more than a century, industrialisation has continuously moved carbon in predominantly one direction: from geological reservoirs into the active carbon cycle. That is the physical flow we ultimately need to change. Net zero is the destination Net zero defines an atmospheric outcome. Anthropogenic greenhouse-gas emissions must ultimately be balanced by anthropogenic removals so that human activity no longer produces a continuing net increase in atmospheric greenhouse gases. That objective is essential. But net zero does not, by itself, prescribe the engineering architecture required to achieve it. Two systems can both have a net-zero objective while having very different physical energy and carbon flows. This is why we also need to distinguish decarbonisation from defossilisation. Decarbonisation asks: How can we reduce greenhouse-gas emissions? Defossilisation adds another question: How can we progressively reduce the continual introduction of newly extracted geological carbon into our energy and industrial systems? These objectives are related, but they are not identical. Electrification is a pathway, not the destination Electrification is one of the most powerful tools available to us. Electric vehicles can replace internal-combustion engines. Heat pumps can replace combustion heating. Electric industrial processes can replace fossil-fired equipment. But electrification does not make energy demand disappear. It transfers that demand to the electricity system. The complete question therefore becomes: How is the additional electricity generated, transmitted, stored and firmed? The same principle applies to hydrogen. Hydrogen can be enormously valuable in steelmaking, chemicals, heavy transport, energy storage and other applications where direct electrification may be difficult. But hydrogen is an energy carrier and industrial feedstock, not an energy source. Its environmental outcome depends on how it is produced. So rather than asking whether a technology is labelled renewable, hydrogen, electric or low-carbon, we should examine the complete physical system. Follow the energy. Follow the carbon. Carbon avoidance, removal — and circulation Carbon markets commonly distinguish between two important activities. Avoidance prevents emissions that otherwise would have occurred. Removal takes CO₂ already present in the atmosphere and stores it durably. Both have important roles. But increasingly there may be a third carbon-management concept worth considering: circulation. Instead of treating carbon as something that passes through an industrial system once before becoming waste, what if recovered carbon could increasingly be treated as an inventory? The physical architecture could begin moving from: extract → use → emit toward: use → recover → reuse → recover → reuse No engineered system will circulate material perfectly. There will be losses, degradation, energy requirements and make-up inputs. The meaningful question is therefore not whether a system can become literally 100% circular. It is: How much new resource extraction can repeated recovery and reuse displace? That may ultimately be one of the most useful measures of circularity. Carbon as inventory This changes how we think about captured carbon. If CO₂ is simply captured at one location and released somewhere else later, little has been achieved atmospherically. If it is permanently stored, it can represent carbon storage or removal depending on its origin and the applicable accounting framework. But if carbon can be recovered and repeatedly reused within an engineered system, another outcome becomes possible: reduced demand for new geological carbon input. This suggests that future carbon management may need to consider at least three physical pathways: Avoid it. Remove it. Circulate it. And each requires different measurement. For avoidance: What emission genuinely did not occur? For removal: How much atmospheric carbon was removed and durably stored? For circulation: How much new carbon input was displaced through repeated recovery and reuse? These concepts should not be confused or double counted. But neither should physically different carbon-management pathways be forced into the same conceptual category. Measurement must follow the physics This also has implications for carbon accounting. Installing equipment does not guarantee an environmental outcome. A carbon-capture plant does not prove how much carbon was ultimately prevented from reaching the atmosphere. An electrolyser does not automatically prove that hydrogen is low-carbon. A renewable-energy contract does not necessarily describe the instantaneous electricity supplying a facility. And circulating carbon cannot simply be counted repeatedly as carbon removal. The strongest measurement systems should therefore reconcile the actual physical flows across a clearly defined boundary. For carbon, that means understanding: **carbon entering the system • opening carbon inventory − carbon leaving in products − carbon recovered and retained − carbon released = closing carbon inventory** In other words: Where did the carbon actually go? Measurement, reporting and verification should increasingly answer that physical question. The same principle applies to AI Artificial intelligence provides a useful contemporary example. Much of the discussion about AI’s environmental footprint focuses on data-centre electricity consumption, cooling and water. Those are important. But AI is also an optimisation technology. If AI makes fossil-resource extraction more productive, its carbon consequences may extend far beyond the electricity consumed by the servers performing the computation. If AI instead improves renewable integration, industrial efficiency, methane detection, carbon capture, resource recovery or material circulation, its enabled impact may move in the opposite direction. So perhaps the question should not simply be: Is AI sustainable? Instead: What physical energy and material flows does AI cause to change? Again: Follow the energy. Follow the carbon. From carbon accounting to carbon management Carbon accounting remains essential. Organisations need credible inventories, common standards and transparent reporting. But the next stage of the transition must increasingly move from accounting for carbon to engineering carbon flows. That means designing power systems, industrial plants, transport systems, buildings and data centres so that they require progressively less virgin fossil-carbon input for every unit of useful output. It also means recognising that renewable energy, electrification, hydrogen, efficiency, carbon capture, storage, removal and carbon circulation are not necessarily competing philosophies. They are engineering tools. Their value should be judged by measurable system outcomes. A simple test Whenever we encounter a proposed climate solution, perhaps we should ask five questions: Where does the energy come from? Where does the carbon come from? Where does the carbon go? How much new geological carbon does the system require? What changes when the complete system boundary is considered? Those questions cut through many labels. The energy transition is ultimately not a transition between fashionable technologies. It is a transformation of physical systems. Net zero defines the destination. Decarbonisation measures progress toward it. Defossilisation changes the underlying carbon flow. And one of the simplest ways to see whether that transformation is genuinely occurring may be: Follow the carbon.