Solar panels yield far more energy per acre than biofuels
Context: A Poland-sized area is dedicated to liquid biofuels. Is there a more efficient way to generate energy?
Electric vehicles might be promoted as the key technological solution for low-carbon transport today, but they were not always the obvious option. Back in the early 2000s, it was biofuels. Rather than extracting and burning oil, we could grow crops like cereals and sugarcane, and turn them into viable fuels.
- While we might expect biofuels to be a solution of the past due to the cost-competitiveness and rise of electric cars, the world produces more biofuels than ever. And this rise is expected to continue.
- In this article, we give a sense of perspective on how much land is used to produce biofuels, and what the potential of that land could be if we used it for other forms of energy. We will focus on what would happen if we used that land for solar panels, and then how many electric vehicles could be powered as a result. We will mostly focus on road transport, as that is where 99% of biofuels are currently used.
- To be clear: we are not proposing that we should replace all biofuel land with solar panels. There are many ways we could utilise this land, whether for food production, some biofuel production, or rewilding. Maybe some combination of all of the above. But to make informed decisions about how to use our land effectively, we need to get a perspective on the potential of each option. That is what we aim to do here for solar power and electrified transport.
Source and impacts
- Most of the world’s biofuels come from sugarcane (mostly grown in Brazil), cereal crops such as corn (mostly grown in the United States and the European Union), and oil crops such as soybean and palm oil (which are grown in the U.S., Brazil, and Indonesia). Collectively, these biofuels produce around 4% of the world’s energy demand for transport. While that does push some oil from the energy mix, the climate benefits of biofuels are not always as clear as people might assume.
- Once we consider the climate impact of growing the food and manufacturing the fuel, the carbon savings relative to petrol can be small for some crops. But more importantly, when the opportunity costs of the land used to grow those crops are taken into account, they might be worse for the climate. That is because agricultural land use is not “free”. If we chose not to use it for agriculture, then it could be rewilded and reforested, which would sequester carbon from the atmosphere.
- From a climate perspective, freeing up that cropland from biofuels would be one alternative. However, another option is to utilise it for another form of energy, which could offer a much greater climate benefit.
- A recent analysis from researchers at Cerulogy estimated that biofuels are grown on 61 million hectares of land. But when they split this allocation between land for biofuels and land for animal feed, the land use for biofuels alone was 32 million hectares. There are much higher published figures too. For this article, we are going to assume a net land use of 32 million hectares. This is conservative, and that is deliberate. For context, that is about the size of Germany, Poland, the Philippines, Finland, or Italy.
Solar power equivalent
- How much solar power could you produce on that land, and how many cars could you run? Could we use those 32 million hectares of land differently to produce even more energy than we currently get from biofuels?
- The answer is yes. If we put solar panels on that land, we could produce roughly 32,000 terawatt-hours of electricity each year. That is 23 times more than the energy that is currently produced in the form of all liquid biofuels. 32,000 terawatt-hours is a big number. The world generated 31,000 TWh of electricity in 2024. So, these new solar panels would produce enough to meet the world’s current electricity demand.
- Again, our proposal is not that we should cover all of this land in solar panels, or that it could easily power the world on its own. We don’t account for the fact that we would need energy storage and other options to make sure that power is available where and when it is needed (not just when the sun is shining). We are just trying to get a sense of perspective for how much electricity could be produced by using that land in more efficient ways.
- These comparisons might seem surprising at first. But they can be explained by the fact that growing crops is a very inefficient process. Plants convert less than 1% of sunlight into biomass through photosynthesis. Even more energy is then lost when we turn those plants into liquid fuels. Crops such as sugarcane tend to perform better than others, like maize, but even they are still inefficient.
- By comparison, solar panels convert 15% to 20% of sunlight into electricity, with some recent designs achieving as much as 25%. That means replacing crops with solar panels will generate a lot more energy.
Solar versus biofuels
- Now, you might think that we are comparing very different things here: energy from liquid biofuels meant to decarbonise transport, and solar, which could decarbonise electricity. But with the rise of affordable and high-quality electric vehicles, solar power can be a way to decarbonise transport, too.
- Run the numbers, and we find that you could power all of the world’s cars and trucks on this solar energy if transport were electrified. Of course, these vehicles would need to be electrified in the first place. This is happening — electric car sales are rising, and electric trucks are now starting to get some attention — but it will take time for most vehicles on the road to be electric. For now, we will imagine that they are.
- We estimate that the total electricity needed to power all cars and trucks is around 7,000 TWh per year, comprising 3,500 TWh for cars and a similar amount for trucks. You could power all of the world’s cars and trucks on this solar energy if transport were electrified.
- That is less than one-quarter of the 32,000 TWh that solar panels could produce on biofuel land. Consider those options. The world could meet 3% or 4% of transport demand with biofuels. Or it could meet all road transport demand on just one-quarter of that land. The other three-quarters could be used for other things, such as food production, biofuels for aviation, or it could be left alone to rewild.
- Land use comes at a cost, so we should think carefully about how to use it well. Our point here is not that we should cover all of our biofuel land in solar panels. What we do want to challenge is how we think and talk about land use. People rightly question the impact of solar or wind farms on landscapes, but rarely consider the land use of existing biofuel crops, which do very little to decarbonise our energy supplies.
