Have you ever wondered at what point we will run out of fossil fuels? When that happens, how do you envision the world to look like? Would all civilisation come to a standstill? Will we all have to start living like [we did pre-industrialisation](https://www.bbc.co.uk/bitesize/articles/zm9r4xs#zw9nb7h)? Let's find out. Fossil fuels are in a way quite similar to a carton of milk. There is somehow always a need for us to go on making estimations about when it would run out! Let's assume that I have just walked into my local grocers' and grabbed a litre of milk. If I wanted to understand how long before the carton runs out, there are two variables I would need to know - *how much milk I have to start off with* and *how much I would use everyday*. If I know I use about 200ml everyday for my morning oatmeal; and I have just bought a litre , I can safely assume that I could put away running to the grocery store for 5 days. Extrapolating this idea to fossil fuels, we get the most basic version of the [Reserves/Production ratio (R/P ratio)](https://energyeducation.ca/encyclopedia/Reserves/production_ratio). $R/P\; Ratio = \frac{Amount\;of\;Known\;Resource}{Amount\;Produced\;or\;Used\;in\;One\;Year}$ *The R/P ratio is the remaining amount of time a given reserve would last if production were to continue at the current rate*. In the most basic sense, the numerator is *how much of the resource is remaining* and the denominator is *how much is consumed every year*. For example, an R/P ratio of 8 indicates that the reserve in question would be able to supply resources for 8 more years at the same rate of production. This does not necessarily mean that the reserve would be *empty* after 8 years. It merely means that the reserve would be unable to support the demand it once could after 8 years, unless there are technological interventions that positively (to many, the word is *magically*) increase output. To stakeholders involved such as oil companies and governments, the R/P ratio is one of the metrics they could use to understand the state of fossil fuels. To some, this could also be misinterpreted as a *metric of doom*, leading to callouts such as *Fossil fuels would last us ONLY for the NEXT X years!!!*. We have all seen an article like this at least once. As per the [Statistical Review of World Energy](https://ourworldindata.org/grapher/years-of-fossil-fuel-reserves-left), the R/P ratios for our fossil fuels globally are <iframe src="https://ourworldindata.org/grapher/years-of-fossil-fuel-reserves-left?tab=chart" loading="lazy" style="width: 100%; height: 600px; border: 0px none;" allow="web-share; clipboard-write"></iframe> Looks rather grim no? But, what does this ratio even mean? How accurate is it? Is future really as bleak as this suggests? In the remainder of this article, these are exactly the kind of questions we will answer. ### Exploring the `Reserve` component In the R/P ratio, a `Reserve` references specifically to *proven reserves*. [**Proven reserves** are quantities of fossil fuels—such as oil, natural gas, or coal—that geological and engineering data confirm with reasonable certainty to be recoverable from known reservoirs under existing economic and operational conditions](https://www.spe.org/industry/docs/Definitions-Proved-Reserves-for-Property-Evaluation-1965.pdf). A higher `Reserve` component would indicate a higher R/P ratio. Let's return to our milk analogy. In this scenario, the **Reserve** is the milk carton itself, and the **Production** is how much milk I consume daily. Initially, I knew exactly how much milk I had because I had just bought a full litre. But what happens if I start this _milk estimation exercise_ abruptly one evening when I'm particularly motivated to do some grocery shopping—perhaps on a day when I'm tired of having crisps and nuts for dinner? Now, I have no clue how much milk is left in the carton. The numerator of my R/P ratio is unknown... Turns out, that fossil fuel companies also grapple with this issue. The **R** in the R/P ratio represents the known reserves, but it is often a *best case estimate*, [arrived to at via different methodologies](https://wiki.aapg.org/Reserves_estimation). This lack of standardisation in measurement leads to a [few challenges in obtaining accurate values - the most basic of which are uncertainty and obscurity](http://large.stanford.edu/courses/2013/ph240/zaydullin2/docs/demirmen.pdf). > Amounts of known resource available in a specific reserve are not always measured with a standard methodology across the globe and when they are measured, these are *estimates with varying degrees of accuracy*. Just as not knowing how much milk is left affects my ability to plan for future breakfasts, uncertainty in reserve estimates impacts how accurately we can predict the longevity of fossil fuel supplies. This makes the R/P ratio less of a precise countdown and more of a rough gauge that must be interpreted with caution. ### Exploring the `Production` or `Usage` component Mathematical ratios often come with underlying assumptions, and it's these assumptions that give context and meaning to the numbers. In our case, the phrase _"if production were to continue at the same rate"_ in the definition of the R/P ratio is crucial. Returning to my milk example, what if I decide to skip breakfast tomorrow? Now, I might have an extra day before the milk runs out. Conversely, if I decide to make a milkshake today, I'll use more milk than usual, reducing the time before I need to buy a new carton. Similarly, in the case of fossil fuels, consumption rates are not static—they fluctuate based on various factors. *Consumption* has been on the rise, with the [Statistical Review of World Energy 2023 reporting a global increase in fossil fuel consumption](https://www.energyinst.org/exploring-energy/resources/news-centre/media-releases/a-year-of-record-highs-in-an-energy-hungry-world,-reveals-ei-statistical-review#:~:text=Global%20fossil%20fuel%20consumption%20reached,down%20from%2082%25%20last%20year.). However, this increased rate of consumption is not uniform across the world. Developing countries such as India tend to have much higher rates of increase than their more developed counterparts. India also [imports about 85% of it's crude oil](https://www.thehindu.com/business/Economy/indias-crude-oil-import-bill-falls-but-import-dependency-hits-new-high/article68075642.ece). Like India, there are many more economies that rely on others to get their fossil fuel supplies. This nuance of *global trade* is not immediately clear when one looks at the R/P ratio. In the global scenario, if the R/P ratio for crude oil declines due to increasing consumption, there will be a need for more technological innovations to extract more from existing reserves or discover new ones. Implementing these cutting-edge technologies requires substantial capital investment. Countries that heavily depend on imported fossil fuels, would need significant funds to secure their energy needs. Where would this money come from? Who would bear the cost? What if a country cannot afford it? The more one contemplates this, the harder it becomes to ignore that a future dependent on fossil fuels would exacerbate socio-economic imbalances. > As consumption of fossil fuels increases, the R/P ratio is expected to decrease as **Production** (or usage) goes up. Theoretically, this could lead us closer to a [*Mad Max*](https://www.vulture.com/2015/05/mad-max-review.html) scenario, where resources are scarce and competition is fierce, rather than a society completely devoid of fossil fuels. Another point I would like to make here is about the certainty of production estimates. A reserve is valuable when the resource it contains can be extracted in an economically feasible manner. If oil in a reserve is difficult to access, the production output from it will naturally be low. Even if this reserve has a sizeable estimated resource, it would give us a deceptively large R/P ratio. However, if we reach a point where we can no longer extract the resource due to technological or economic constraints, the large R/P ratio might not hold any real significance. > **Production** estimates, while often accurate, do not always paint the full picture. They are, in a way, best-case scenarios like the **Amount of Resource** estimates. For example, it's challenging to predict unforeseen events such as wars or economic crises that can dramatically increase fuel consumption. ### A crucial limitation of the R/P ratio I'm a big fan of Hans Rosling's approach to debunking myths of the world with data. When I came across an article on fossil fuel depletion by the Gapminder Foundation (co-founded by Rosling), my eyes naturally lit up. As per [the article](https://www.fairplanet.org/story/when-will-we-run-out-of-fossil-fuels/), in the last 40 years, fossil fuel reserves have doubled! The central argument is that as time progresses, technological advancements enhance our ability to discover and extract fossil fuels. The technology now available to companies in the fossil fuel industry is far superior to what was available in earlier decades. Following this pattern, we _could become more adept_ at discovering new reserves and finding better ways to extract fuels from them. I use _could_ rather than _would_ because there's no definitive way to know how much fossil fuel we can continue to extract. This brings us to the concept of [Hubbert's Curve](https://energyeducation.ca/encyclopedia/Hubbert%27s_peak), which suggests the existence of a _peak resource_ threshold. Beyond this peak, the production of a resource would decline even as demand increases. While this theory has been validated to some extent for U.S. crude oil production, [there is little evidence to suggest that the world has reached *peak oil*](https://www.forbes.com/sites/davidblackmon/2024/04/10/a-new-report-tackles-the-myth-of-peak-oil/). Technological innovations and new discoveries have continually pushed this peak further into the future. <iframe src="https://ourworldindata.org/grapher/hubberts-peak-vs-actual-oil-production-in-the-united-states?tab=chart" loading="lazy" style="width: 100%; height: 600px; border: 0px none;" allow="web-share; clipboard-write"></iframe> > R/P ratios do not account for reserves that could be _discovered_ or made economically viable in the future. Unless we can time travel or possess a crystal ball, there's no way to predict these future developments! This limitation highlights a crucial shortcoming of the R/P ratio: it provides a snapshot based on current known reserves and production rates, without factoring in future technological advancements or discoveries. Just as my milk estimation doesn't account for finding another carton hidden in the back of the fridge, the R/P ratio doesn't consider the potential for new reserves to be found or for existing reserves to become accessible through technological progress. ### So, when will we run out of fossil fuels? In 50 years? In a 100 years? In a 1000 years? Who knows - maybe we find a hidden stash on Mars? As we've explored in this article, while the R/P ratio is a widely used metric, it comes with inconsistencies and uncertainties. For the most part, we can probably ignore doomsday articles that treat the R/P ratio as a countdown timer until the world's fossil fuel reserves dry up completely. However, the core message remains highly relevant: fossil fuels are finite, and it's only going to get harder to sustain the demands of an energy-hungry global economy as time passes. The more we consume, the more we need; the more technology we need to discover; the more energy we need to operate that technology—and the cycle continues. Before I sign off, I would like to extend a fun thought experiment to you, the reader. Think about how you would on an individual level attempt to best utilise resources in your pantry. Do you get creative to make ingredients last longer or find clever ways to use leftovers? Maybe it's time we apply that same ingenuity to how we use energy. After all, everything we consume has a direct or indirect impact on nature's resources. Starting small might just be the start of having a big impact! Fin.