Follow the Carbon, Data Centres, The Digital Economy Still Runs on Physical Energy

Artificial intelligence may operate in the digital world, but the infrastructure supporting it is intensely physical. Every query, model-training run and cloud service ultimately requires electricity. That electricity becomes computation, heat, cooling demand and, depending on the cooling system and electricity source, water consumption and carbon emissions. As data-centre capacity expands, perhaps we should stop looking at the data centre simply as an electricity consumer and start looking at the complete physical system. Follow the Energy The conventional boundary is often: Grid → Data Centre → Computing But the physical pathway is considerably longer: Primary energy → electricity generation → transmission → data centre → IT equipment → heat → cooling → surroundings At every stage there are conversion losses, infrastructure requirements and opportunities for energy recovery. This is why renewable electricity is important, but the percentage of renewable electricity contracted by a data centre does not by itself describe the performance of the complete energy system. We should also ask: How much primary energy was required? When was the electricity generated relative to when it was consumed? What firming, storage and network infrastructure was required? What happens to the heat produced by the servers? How much water is consumed? And what happens when renewable generation is unavailable? Now Follow the Carbon Carbon accounting requires a parallel pathway. Where electricity is generated from fossil fuels, the carbon pathway may be: Geological carbon → extraction → fuel → power generation → CO₂ → atmosphere Renewable generation changes that pathway substantially because there is no continuous fossil-carbon feedstock entering the generation process. But when gas engines, turbines or other combustion technologies provide backup or firm power, we should continue following the carbon. Was the carbon newly extracted from geological reserves? Was the CO₂ captured? Was it permanently stored? Was the carbon recovered and reused? Or was it released to the atmosphere? These are materially different carbon pathways even when they ultimately deliver the same unit of electricity to a server. Net Zero, Decarbonisation and Defossilisation Are Not Identical These terms are often used interchangeably, but they describe different questions. Net zero asks about the balance between emissions and removals within a defined boundary. Decarbonisation measures the reduction of emissions associated with an activity or economy. Defossilisation asks a more fundamental material-flow question: How much newly extracted fossil carbon continues to enter the system? A data centre could therefore reduce its carbon intensity substantially while still depending indirectly on fossil carbon during particular hours. Conversely, a future energy system could potentially use carbon-containing molecules without continually extracting new geological carbon, provided the carbon itself were recovered and managed within a sufficiently controlled cycle. The distinction is not semantic. It changes what we measure. The Data Centre Could Become Part of the Energy System There is another opportunity. Data centres do not necessarily have to remain passive loads. Integrated correctly, they could combine: Firm generation + renewable electricity + storage + flexible computing loads + thermal storage + heat recovery + cooling + water management Some workloads can potentially respond to electricity-system conditions. Cooling systems can incorporate thermal inertia or storage. Waste heat may have productive uses where suitable heat sinks exist. On-site generation can improve resilience and reduce dependence on constrained networks, although its complete fuel and carbon pathway must still be accounted for. The design question therefore becomes larger than: How do we supply enough electricity to the data centre? It becomes: How do we design the data centre and its energy infrastructure as one integrated system? A Better Measure of Sustainable Compute PUE remains useful for measuring data-centre energy efficiency, but the transition may eventually require broader system metrics. Alongside PUE, we may need to understand: • primary energy consumed per unit of useful computation; • carbon introduced and released; • water consumed and recovered; • heat rejected and productively reused; • firm capacity required from the wider electricity system; • and flexibility supplied back to that system. This is particularly important as AI infrastructure grows from individual facilities into energy-intensive industrial clusters. The digital economy cannot escape thermodynamics. Every computation requires physical energy. Every energy conversion has consequences. And every carbon atom has an origin and a destination. So when assessing whether the next generation of data centres is truly sustainable, perhaps we should look beyond the server rack and ask two simple questions: Where did the energy come from? Where did the carbon go? Follow the Energy. Follow the Carbon. #FollowTheCarbon #DataCentres #ArtificialIntelligence #EnergyTransition #Decarbonisation #Defossilisation #EnergyEfficiency #SustainableCompute #NetZero

Follow the Carbon: Carbon Credits — Accounting for Carbon Is Not the Same as Controlling Carbon

Follow the Carbon: Carbon Credits — Accounting for Carbon Is Not the Same as Controlling Carbon Carbon credits have become an important part of the global response to climate change. They can create a financial value for reducing, avoiding or removing greenhouse-gas emissions. They can also help direct capital toward projects that might otherwise struggle to attract investment. But there is a fundamental distinction that is sometimes lost in the discussion: A carbon credit is an accounting instrument. Carbon itself is a physical material. Understanding the difference requires us to follow the carbon. Consider a facility consuming natural gas. Carbon enters the system physically as hydrocarbons. Combustion converts that carbon primarily into CO₂. The CO₂ then crosses the plant boundary and enters the atmosphere unless it is captured. A carbon credit may change the facility’s reported or compensated emissions position. It does not, by itself, change that physical carbon pathway. That distinction does not make carbon credits meaningless. It simply tells us what they can—and cannot—do. Three different questions When evaluating any climate strategy, it is useful to separate three questions. Net zero asks: What is the balance between greenhouse-gas emissions and removals across a defined accounting boundary and period? Decarbonisation asks: How are we reducing the carbon intensity or greenhouse-gas emissions associated with an activity? Defossilisation asks: Are we reducing and ultimately ending the transfer of additional geological carbon into the active atmosphere–biosphere–ocean system? These questions overlap, but they are not identical. A company may improve its reported net emissions through high-quality credits while continuing to consume fossil carbon. It may decarbonise a process substantially without completely eliminating fossil feedstock. And a system may pursue defossilisation by changing where its carbon originates and how carbon physically circulates through the system. The terminology matters because each describes a different aspect of the problem. Follow the physical carbon first Before discussing credits, certificates or offsets, draw the system boundary. Then ask: Where does the carbon enter? Is it geological, biogenic, atmospheric or recycled? Where does it go? How much becomes product? How much is captured? How much is recycled? How much is permanently stored? And how much ultimately reaches the atmosphere? Those are physical questions. They require mass balances, measurement and clearly defined boundaries. Only after establishing that physical carbon inventory should we apply the accounting framework. This is particularly important because one tonne of CO₂ represented in an accounting system and one tonne of CO₂ physically moving through an industrial process are related concepts—but they are not the same thing. Measurement strengthens carbon accounting For industrial systems, the strongest carbon accounting begins with physical measurement wherever practical. Gas flow can be measured. Gas composition can be measured. Carbon entering and leaving a process can therefore be calculated from actual operating data. For example, where natural gas, hydrogen-rich synthetic gas or recycled gas streams are involved, composition matters. Methane, carbon monoxide, carbon dioxide and hydrogen contribute differently to the carbon and energy balances. This is why instrumentation such as flow measurement and gas chromatography can become important not only for process control, but also for carbon accounting. The objective should increasingly be: Follow the carbon physically, reconcile the mass balance, and then apply the accounting rules. Carbon credits still have a role High-integrity carbon credits can support activities such as verified carbon removal, methane abatement, ecosystem restoration and other genuine emissions-reduction projects. But their role should be clearly understood. They are mechanisms for assigning economic and accounting value to defined climate outcomes. They should not become a substitute for understanding the physical system producing the emissions in the first place. For industrial decarbonisation, the hierarchy therefore matters: Measure the physical flows. Reduce avoidable emissions. Change the underlying carbon pathway where technically and economically possible. Use credible accounting mechanisms for what remains. The climate challenge ultimately exists in the physical world, not in the ledger. Carbon accounting is essential for measuring responsibility and progress. But if we want to understand whether an energy system is genuinely changing, there is an even simpler question to begin with: Where did the carbon come from, where did it go, and will we need to extract more geological carbon to run the system again? Follow the carbon, and the distinction becomes much clearer. #FollowTheCarbon #CarbonCredits #CarbonAccounting #NetZero #Decarbonisation #Defossilisation #EnergyTransition #CarbonManagement

How to Deal with Carbon Emissions Using Holistic Process Engineering Principles

How to Deal with Carbon Emissions Using Holistic Process Engineering Principles A framework for following carbon, energy, and consequences across the whole system 1. Start with the fundamental physical reality Carbon is matter. In ordinary industrial chemical processes, carbon atoms are neither created nor destroyed. They are transformed from one chemical form to another and transferred from one location or reservoir to another. Combustion illustrates this clearly: CH₄ + 2O₂ → CO₂ + 2H₂O The carbon contained in methane has not disappeared. It has simply moved into CO₂. Methanation demonstrates another transformation: CO₂ + 4H₂ → CH₄ + 2H₂O Again, the carbon remains. Carbon does not disappear when it crosses an engineering, corporate, geographical or regulatory boundary. We must continue following it. 2. The system boundary is necessary - but it can also mislead us Engineers need boundaries. Without them, mass balances, energy balances and process calculations would be impossible. But nature does not recognise the boundaries we draw on process-flow diagrams. A power station may reduce its stack emissions by capturing CO₂. From the plant boundary, this appears to solve the emissions problem. Holistic Process Engineering asks the next question: Where did the carbon go? If it was compressed, transported, and injected underground, the carbon has not disappeared. Its location and physical state have changed. Properly designed geological storage is intended to retain CO₂ for very long periods, and monitoring technologies exist to evaluate containment. The holistic point is that moving a material beyond the visible boundary of one process cannot, by itself, be considered the end of our responsibility for that material. 3. Follow the Carbon rather than only Follow the Emission Instead of asking only, “How much CO₂ came out of the stack?”, ask: “Where did the carbon originate, where is it now, and where will it ultimately reside?” Conventional fossil-energy pathway: Geological carbon → extraction → processing → fuel → combustion → CO₂ → atmosphere/ocean/biosphere The climate problem arises fundamentally from continually transferring carbon from a geological reservoir into the active carbon cycle. Reducing emissions is necessary, but the deeper destination should be defossilisation: progressively ending the requirement for continual extraction of additional geological carbon. 4. CCS changes the destination, but does not eliminate the carbon Conventional CCS creates another pathway: Geological carbon → extraction → fuel → combustion → CO₂ capture → conditioning → compression → transport → geological injection → long-term geological inventory This can substantially reduce atmospheric emissions when it operates successfully. Holistic Process Engineering, however, requires assessment of the entire chain: capture efficiency, energy penalty, compression, transportation, injection, reservoir behaviour, monitoring, leakage risk and long-term responsibility. Design performance should never be confused with demonstrated sustained operating performance. A FEED study specifying a high capture percentage is an engineering design objective; it is not equivalent to a facility demonstrating that performance continuously for 10 or 20 years. The same standard must ultimately apply to CRT. 5. History tells us that the carbon question is not new The scientific foundations extend back well over a century. Eunice Newton Foote demonstrated the heat-retaining behaviour of CO₂-rich air in 1856. Svante Arrhenius quantitatively investigated the relationship between atmospheric CO₂ and temperature in 1896. In 1912, the now-famous “Coal Consumption Affecting Climate” item publicly explained that burning enormous quantities of coal was adding CO₂ to the atmosphere and could increase Earth's temperature. In 1985, Carl Sagan testified before the United States Senate about fossil-fuel CO₂ and greenhouse warming. The important lesson is not that humanity suddenly discovered the carbon problem recently. Our understanding has progressively strengthened over more than a century. The engineering question now is: What are we going to do differently with the carbon? 6. Separation is useful - but separation does not terminate responsibility Process engineering depends on separation. We separate CO₂ from flue gas, hydrogen from mixtures, water from process streams, and contaminants from products. There is nothing inherently wrong with separation. The problem arises when separation is mistaken for resolution. Separation can be a process operation, but it cannot be the boundary of our responsibility. What we separate conceptually remains connected physically. 7. There is another possible carbon pathway: circulation Methanation itself is not a new experimental chemistry. Industrial methanation and synthetic natural gas production have decades of experience, including large coal-to-SNG installations. A simplified coal-to-SNG pathway is: Coal → gasification → syngas → gas treatment → methanation → SNG The fundamental carbon issue remains the continuing introduction of new geological carbon and the eventual release or disposal of carbon from the process. This raises a logical engineering question: If CO₂ can be captured, and captured carbon can be converted with hydrogen into methane, why must disposal necessarily be the final destination of the captured carbon? 8. CRT changes carbon from a waste stream into a circulating inventory Conceptually, the proposed Carbon Recycling Technology (CRT) pathway is: Managed carbon inventory → RSNG → power + heat → CO₂ → capture → conditioning → methanation + H₂ → RSNG → repeat The intention is not to destroy carbon. Instead, the objective is to manage carbon as an inventory. Once the circulating inventory has been established, additional carbon should ideally be required primarily to replace measurable carbon losses rather than continually supplying the gross quantity circulating through the system. 9. CRT must be subjected to exactly the same standard Holistic thinking cannot be used to criticise CCS while giving CRT an exemption from rigorous measurement. If CEWT claims high carbon circulation, a demonstration plant must prove it through a whole-system carbon balance: Carbon input = Carbon products + Carbon emissions + Carbon waste + Change in carbon inventory Every significant pathway should be instrumented. The system should measure carbon entering, carbon converted, carbon combusted, carbon captured, carbon recycled, carbon lost and carbon make-up required. A Carbon Recirculation Ratio may ultimately become an important CRT performance indicator, but its precise definition should be established rigorously during engineering and demonstration. 10. Technology readiness must distinguish components from architecture The relevant question is not simply, “Has CRT operated commercially for 20 years?” It has not. Instead, each element should be assessed independently. Methanation, syngas production, hydrogen production, CO₂ separation, CO₂ compression, gas turbines or engines, and heat recovery are established industrial operations at varying levels of commercial maturity. The novel element is primarily the integration of these operations into sustained carbon recirculation, carbon-inventory management, and dynamic plant operation. A technically defensible description is: CRT is a novel system architecture integrating predominantly established industrial unit operations, with sustained closed-loop carbon recirculation and integrated system performance requiring demonstration. 11. Data, logic, intuition and engineering each have a role Data tells us what has happened. Logic asks whether our explanation is internally consistent. Scientific knowledge establishes the governing physical laws. Engineering determines whether an alternative can actually operate. Within Holistic Process Engineering, spiritual intuition provides another perspective: intuition sees the whole before we divide it into individual analytical pieces. These do not have to compete. A holistic engineering process can move through: Intuition → question → logic → scientific analysis → engineering → measurement → demonstration The intuition may originate the idea. Ultimately, nature determines whether the engineering works. 12. Follow both carbon and energy Carbon cannot be considered independently of energy. Converting CO₂ back into methane requires hydrogen and therefore substantial energy. Consequently, circulating carbon is environmentally meaningful only if the energy required to maintain that circulation is simultaneously accounted for. This leads to the broader principle: Follow the Carbon and Follow the Energy simultaneously. A solution that closes one material loop while creating an unsustainable energy requirement somewhere outside the selected boundary would not satisfy Holistic Process Engineering. The central proposition We create boundaries to understand nature. Nature does not obey the boundaries we create. Carbon does not know whether it has crossed a power-station fence. It does not recognise corporate ownership or national borders. It does not disappear because it has moved beyond human sight. Dealing with carbon emissions holistically therefore means continuing to follow the carbon - and the energy associated with it - until the consequences across the whole system are understood. This provides the philosophical and scientific foundation for Follow the Carbon, defossilisation, and the continuing development and demonstration of CRT.

Follow the Carbon — Carbon Capture Is Not the Destination

Carbon capture is becoming an increasingly important part of the climate and industrial-policy conversation. Capture rates. Tonnes captured. CO₂ pipelines. Storage hubs. Carbon utilisation. Carbon removals. These are all useful discussions. But there is a simple physical question that should come before almost all of them: What happens to the carbon after we capture it? Because capture itself is not a destination. It is a separation step. First, follow the carbon into the process Consider a conventional fossil-fuel system. The simplified carbon pathway is: geological carbon → extraction → fuel → conversion → CO₂ → atmosphere Carbon capture intervenes near the end of that chain. Instead of allowing all of the CO₂ to enter the atmosphere, part of it is separated from the exhaust or process stream. The pathway may then become: geological carbon → extraction → fuel → conversion → CO₂ → capture → ? That question mark matters. Until we know the next destination, we do not yet know the complete carbon outcome. Capture and storage One pathway is geological storage: CO₂ → conditioning → compression → transport → injection → geological formation Here the objective is to prevent captured carbon from entering the atmosphere by isolating it durably underground. The relevant system questions therefore extend beyond capture efficiency. How much CO₂ was actually captured? How much energy was required for capture, compression and transport? What emissions occurred elsewhere in the system? How much CO₂ reached the storage formation? How securely is it retained? How is the stored inventory measured and monitored? The Global CCS Institute reported 77 commercial CCS facilities operating globally and another 47 under construction as of July 2025, while the IEA’s March 2026 database tracks large-scale capture, transport, storage and utilisation projects worldwide. CCS is therefore moving increasingly from concept toward infrastructure. But infrastructure does not remove the need for carbon accounting. It makes accurate physical accounting even more important. Capture and utilisation Another pathway is: CO₂ → capture → conversion → product This is usually described as carbon capture and utilisation, or CCU. But “utilisation” covers very different carbon outcomes. Captured CO₂ might enter a material in which carbon remains bound for a long period. Or it might be converted into a fuel that is subsequently combusted, returning the carbon to the atmosphere. Both pathways use captured CO₂. They do not necessarily provide the same climate service. This is why the word utilised tells us less than it first appears. We have to keep following the carbon. If captured CO₂ becomes a fuel: Where does the carbon go when that fuel is used? If it becomes a material: How long does the carbon remain there? If it is subsequently recovered: Can it enter another useful cycle? The carbon molecule does not know whether we called the process “capture”, “utilisation” or “recycling”. It simply moves from one reservoir to another. Capture is not necessarily carbon removal This distinction is particularly important. Capturing CO₂ from a fossil-fuel process generally prevents some geological carbon from entering the atmosphere. That can substantially reduce emissions. But it is not physically identical to removing carbon that was already present in the atmosphere. Consider two pathways. Fossil carbon capture: geological reservoir → fuel → CO₂ → capture → geological storage Atmospheric carbon removal: atmosphere → capture or biological uptake → durable storage In the first case, the objective is largely to prevent a transfer. In the second, the objective is to reverse a previous transfer from the active carbon system. Both can matter. But they should not be counted or described as though they are the same physical process. The energy must also be followed Capturing carbon requires energy. So carbon analysis alone is insufficient. We must simultaneously ask: Where did the energy for capture come from? Capture systems may require heat, electricity, compression, pumping, refrigeration, regeneration of solvents or sorbents, and downstream CO₂ conditioning. That additional energy has its own physical origin. If supplying it creates additional emissions, those belong inside the system boundary. This does not make carbon capture inherently good or bad. It simply means the meaningful metric is not the gross amount of CO₂ entering the capture equipment. The meaningful result is the net carbon outcome across the complete system. Net zero, decarbonisation and defossilisation Carbon capture also demonstrates why these terms should not be used interchangeably. Net zero describes a balance between greenhouse-gas emissions and removals across a defined boundary. Decarbonisation reduces emissions or emissions intensity. Capturing and permanently storing fossil CO₂ can therefore be an important decarbonisation pathway, particularly for difficult industrial processes. Defossilisation asks a different upstream question: How much newly extracted geological carbon does the system continue to require? A process can become substantially decarbonised through capture while continuing to consume fossil carbon. That is not a contradiction. It simply means decarbonisation and defossilisation are measuring different changes in the physical system. Understanding that distinction can improve both policy and engineering decisions. Perhaps we need to measure carbon pathways, not just captured tonnes The global carbon-management sector is expanding. The IEA reports that more than 30 CCUS projects reached final investment decisions during the past two years and investment exceeded US$5 billion in 2025. Projects currently under construction could nearly double operational capture capacity by 2030. As that infrastructure develops, perhaps our language needs to become more precise too. A tonne of CO₂ captured is an important engineering measurement. But it is not yet the complete carbon story. We should also ask: Where did that carbon originate? How much was actually captured? What energy was required? Where was the carbon transported? Was it stored, converted, released or recirculated? How long did it remain outside the atmosphere? And did the pathway reduce the requirement to extract another unit of geological carbon? Carbon capture gives us control over a carbon stream. What we do with that control determines the outcome. So don’t stop at the capture plant. Follow the energy. Follow the carbon — all the way to its destination.

Hydrogen is increasingly described as one of the building blocks of the energy transition.

Hydrogen is increasingly described as one of the building blocks of the energy transition. Green hydrogen. Blue hydrogen. Renewable hydrogen. Low-carbon hydrogen. Clean hydrogen. These labels can be useful. But from an engineering perspective, perhaps there is an even simpler place to begin: Where did the hydrogen come from? And immediately after that: Where did the energy used to produce it come from? Hydrogen carries energy — it does not create it Hydrogen is an energy carrier and industrial feedstock, not a primary source of energy. To produce hydrogen, energy has to come from somewhere else. Water can be split through electrolysis using electricity. Natural gas can be converted through steam methane reforming. Coal can be gasified. Other chemical and biological pathways are possible. The hydrogen molecule may ultimately be identical. But the physical pathway producing it can be very different. That means evaluating hydrogen solely by the fuel at the point of use can hide much of the system that matters. We have to follow the energy upstream. Follow the energy Consider renewable hydrogen produced by electrolysis. The simplified pathway is: renewable resource → electricity → electrolyser → hydrogen → storage/transport → end use At each conversion and handling step, there can be energy requirements and losses. IRENA notes that electrolysis, and particularly subsequent reconversion of hydrogen into electricity or other energy forms, involves inherent conversion losses. This is one reason direct electrification can be preferable where it is technically and economically practical. That does not make hydrogen inefficient in every application. It means the appropriate question is not: “Is hydrogen good or bad?” It is: “What function are we asking hydrogen to perform?” Hydrogen may be particularly valuable where direct electrification is difficult — including some industrial processes, chemical production, long-duration energy storage and production of hydrogen-derived fuels. The system boundary determines the answer. Then follow the carbon Hydrogen itself contains no carbon. But hydrogen production can have a substantial carbon footprint. The IEA reports that global hydrogen production still remains dominated by unabated fossil fuels. Low-emissions hydrogen production reached almost 1 Mt in 2025, while total hydrogen demand surpassed 100 Mt. So saying simply: “This process uses hydrogen” does not tell us its carbon impact. We need to know how that hydrogen was produced. For fossil-derived hydrogen, follow the geological carbon entering the production system. For hydrogen produced with carbon capture, follow both the captured carbon and the residual emissions across the defined boundary. For electrolytic hydrogen, follow the electricity. Then follow the carbon associated with producing that electricity. The colour assigned to hydrogen is secondary to the physical flows underneath it. Hydrogen can move carbon as well as energy There is another dimension that receives less attention. Hydrogen can react with carbon-containing molecules to produce fuels and chemicals. For example: CO₂ + 4H₂ → CH₄ + 2H₂O Here hydrogen becomes part of a carbon-management pathway. The important questions then become: Where did the CO₂ originate? Where did the hydrogen originate? Where did the energy originate? What happens to the carbon in the methane after use? Does it enter the atmosphere? Is it captured? Is it stored? Is it reused? And does the overall system require another unit of geological carbon to replace it? Now we are no longer simply discussing hydrogen. We are examining a carbon-and-energy system. Why low-emissions hydrogen is struggling to scale The physical system also helps explain some of today’s commercial difficulties. The IEA reports that low-emissions hydrogen production grew by about 20% in 2025, but persistent barriers remain: high costs, uncertain demand, regulation and insufficient infrastructure. Only around 20% of newly signed low-emissions hydrogen offtake volumes in 2025 were backed by firm contractual commitments. This should not necessarily be interpreted as hydrogen failing. It may instead indicate that hydrogen needs to be deployed where its system value justifies the additional conversion steps and infrastructure. The objective should not be to maximise hydrogen production. The objective should be to use hydrogen intelligently where it helps transform the underlying energy and material system. Net zero, decarbonisation and defossilisation Hydrogen also demonstrates why these three concepts should not be treated as synonyms. Net zero describes a balance between greenhouse-gas emissions and removals across a defined boundary. Decarbonisation describes measures that reduce emissions or emissions intensity. Defossilisation asks a different upstream question: Can we progressively reduce the requirement for newly extracted geological carbon? Renewable hydrogen can contribute to decarbonisation and defossilisation when it replaces fossil-derived hydrogen or enables industrial pathways that require less new fossil carbon. But simply introducing hydrogen into a system does not automatically accomplish either. The complete material and energy flows have to be examined. Beyond the colour of hydrogen Perhaps the hydrogen debate has become too focused on colours. Green. Blue. Grey. Pink. Turquoise. Those classifications can help describe production pathways, but they should not replace physical analysis. Instead, ask: Where did the hydrogen come from? Where did the energy come from? Where did the carbon come from? Where did the carbon end up? And finally: Did this system reduce the amount of new geological carbon that had to enter the economy? Hydrogen may become extremely important in the energy transition. But its value will ultimately be determined not by its colour, nor by the molecule alone. It will be determined by the system in which we use it. Follow the energy. Follow the carbon. Because molecules do not carry labels. They carry atoms.