10 Unexpected Energy Sources You Didn't Know Could Be Used As Fuel

In a world dominated by talk of solar panels, wind turbines, and nuclear reactors, some of the most fascinating breakthroughs in energy are happening in unexpected places. Scientists are experimenting with everything from using moisture to break down plastic into usable recycled material, to turning seawater into hydrogen, and even converting banana peels into biogas.

The future of energy isn't just about creativity, it's also about accessibility. A clean technology only matters if it's affordable enough to be adopted widely. That's why researchers are increasingly looking at low-cost, everyday materials that most of us see as waste. Imagine if the dredges of your morning coffee or the leftovers from a winery could one day fuel cars, buses, or even planes.

What once seemed useless might just be the key to fueling the world. So, let's take a look at 10 unexpected energy sources you probably never imagined could be turned into fuel.

Your daily caffeine fix might do more than help you live longer — it could literally power the bus you take to work. It sounds unbelievable, but researchers have discovered that used coffee grounds contain oils suitable for biodiesel production. A London-based startup called Bio-Bean, has already partnered with transport authorities to turn discarded coffee grounds into biofuel for buses.

The process is simple but brilliant. The grounds are collected from coffee shops, processed to extract oil, and converted into biodiesel. Remarkably, this new fuel works seamlessly in existing diesel engines, so there's no need for costly modifications. This approach is not only efficient, it's also eco-friendly because it reduces waste, lowers emissions and reduces the need for fossil fuels. 

Billions of cups of coffee are consumed globally each year, producing massive amounts of waste. If even a fraction of that waste were redirected into fuel, the environmental impact would be enormous.

Seawater, which covers more than 70% of our planet, could become a major source of clean energy. At the University of Adelaide, scientists have developed a method to turn seawater into green hydrogen fuel, without the costly removal of the salt content. Traditional electrolysis (splitting water into hydrogen and oxygen) usually requires purified water because salt corrodes the electrodes. By using a specialized non-precious catalyst, the team bypassed this problem.

The benefits are huge. Green hydrogen is a clean fuel, and producing it directly from seawater lowers costs and energy use. Beyond the lab, companies like Equatic are scaling this idea further, with a process that not only extracts hydrogen fuel but also forces seawater to absorb more carbon dioxide from the atmosphere, locking it away as stable minerals. This means the ocean doubles as both a carbon sink and a fuel factory.

While large-scale adoption is still in progress, this discovery could completely transform energy production, offering a pathway to clean fuel and climate action at the same time.

It sounds like a science fair prank, but urine can actually generate electricity. Researchers at the University of Bath have developed miniature fuel cells that harness bacteria to break down compounds in urine. As the microbes digest the waste, they release electrons, which flow through a circuit to produce an electric current. A similar idea was explored at Northwestern University to draw nearly limitless energy from the soil using microbial fuel cells.

This method has been trialed in schools in Kenya and Uganda, where it powers LED lights in bathrooms and even charges small electronics. Beyond the novelty factor, this technology excels in places where grid power is expensive or unreliable, converting waste into a low-cost source of electricity.

While the power output is relatively small, it shows how unexpected bio-resources can help real communities meet basic energy needs. Who knew the restroom could be a mini power plant?

Tofu might be a protein-packed meal on your plate, but its production leaves behind loads of soybean pulp and wastewater. Instead of letting these byproducts go to waste, scientists have found a way to convert them into biogas using anaerobic digestion. In this oxygen-free process, microorganisms break down organic matter, releasing methane-rich gas that can be used for cooking, heating, or generating electricity.

Factories in Indonesia are already tapping into this system. What's clever is that tofu waste can produce the very energy that keeps tofu-producing factories running. It's cost-effective, sustainable, and reduces dependence on fossil fuels. Unlike high-tech innovations, this solution is relatively straightforward and simply repurposes existing waste materials and technology.

By turning food waste into fuel, tofu factories demonstrate how circular economies can reshape industries. Not only are they feeding people, they're also powering themselves and contributing to a greener energy grid.

Air travel is a notorious contributor to carbon emissions, but a slimy green solution could change that. Algae, rich in oils and fast-growing in saltwater, is emerging as a powerful candidate for sustainable aviation fuel (SAF). Unlike crops like corn or soy, algae doesn't compete with food supplies and produces far more oil per acre of land.

What makes algae oil especially exciting is its high calorific value, meaning it releases significant energy when burned. Airlines are under pressure to adopt SAF under the European Union's RefuelEU Aviation regulations, which require 2% SAF use by 2025, rising sharply in future decades. Algae biofuel could help to meet this demand without straining agricultural land or freshwater resources.

This unusual fuel source seems like science fiction, but it's real and faces significant challenges. Large-scale cultivation, affordability, and building supply chains are just some of the hurdles preventing widespread adoption. Still, the vision of planes powered by photosynthetic organisms harvested from the sea is compelling.

Cows aren't just milk and beef machines — they're also renewable energy generators. Their manure, which has always been useful for crops, is now helping to light up houses and run machines. When processed in biogas plants, cow manure breaks down into methane-rich gas that can heat homes, generate electricity, and even fuel vehicles. The leftover material is a nutrient-rich biofertilizer, creating a zero-waste system.

Methane is a potent greenhouse gas, 28 times stronger than carbon dioxide. When released into the atmosphere unchecked, it contributes heavily to global warming. By capturing it for energy, farms prevent harmful emissions while creating usable fuel. For example, in Japan, a biogas facility handles about 250 tons of manure daily, producing 1.2 megawatts of electricity, enough to power 2,200 homes per year.

This approach turns farms into power plants. Instead of contributing to climate problems, livestock operations can become part of the solution. It's dirty work, but the result is a cleaner environment and a steady source of renewable power.

Every bottle of wine we enjoy leaves behind a surprisingly large amount of skins, seeds, and stems that are collectively called grape pomace. Traditionally, wineries either discard this material or use small amounts for livestock feed, but researchers are now turning it into bioethanol. By fermenting the natural sugars found in pomace with yeast, ethanol is produced, which can then be blended into fuel for cars or used as a renewable energy source.

The process has major environmental advantages. Instead of letting grape waste rot in landfills where it would release methane (a powerful greenhouse gas), it's transformed into a clean-burning fuel, helping to reduce reliance on petroleum.

Countries with thriving wine industries such as France, Italy, and Spain are especially well-positioned to scale this technology. With millions of tons of pomace generated annually, the energy potential is vast. What was once winery trash could end up fueling cars, blending sustainability with one of the world's oldest industries.

Slipping on a banana peel is a comedy trope, but in real life those peels can generate energy. When processed in anaerobic digesters, banana waste breaks down to release methane-rich gas, which can be used for cooking and electricity. According to researchers from the Agro-Energy Group at Universidad Politécnica de Madrid (UPM), banana waste can provide up to 55% of the electrical needs of the Ecuadorian province of El Oro.

The potential is massive. A single kilogram of dried banana peels can produce up to 0.3 cubic meters of biogas — enough to run a small generator. With more than 125 million metric tons of bananas produced worldwide each year, the fuel capacity is staggering.

Urban markets and food processors throw away tons of banana waste daily. Instead of leaving it to rot in landfills (where it releases methane anyway), centralized digesters can capture that energy for communities. In some regions, researchers are even producing bioethanol from banana waste for vehicles. That means your fruit snack could one day help fuel cars.

What happens to the truckloads of tomatoes that spoil before reaching supermarket shelves? Instead of being discarded, scientists have discovered that these rotting tomatoes can actually generate electricity using microbial electrochemical cells. In this system, microbes feed on tomato waste and release electrons during digestion. Electrodes capture those electrons, creating an electric current.

Tomatoes are especially useful in this process because they contain lycopene, a natural pigment that improves the transfer of electrons. Even small amounts of waste (just 10 milligrams) can produce about 0.3 watts of power, so imagine the potential in farming regions where tons of produce are often lost due to oversupply or transport issues.

If farms and processing plants harnessed this method, they could generate energy to power their own facilities instead of paying for costly waste disposal. Microbial fuel cells are still in the early stages of development, but they're a great example of turning food loss into useful energy.

Plastic pollution is one of the world's biggest environmental headaches, but what if trash bags and bottles could be transformed back into fuel? Through a process called pyrolysis, non-recyclable plastics are heated in the absence of oxygen. This breaks their long polymer chains into smaller hydrocarbons, producing pyrolysis oil, which is a viable alternative to gasoline.

Unlike traditional recycling processes, pyrolysis can handle dirty or mixed plastics. Startups such as Petgas in Mexico are already proving the concept, converting 1.5 tons of plastic waste into 356 gallons of fuel in a week. The market for this fuel is currently valued at more than $1.4 billion in the U.S. alone, and it's projected to significantly grow in the next decade.

Challenges remain but pyrolysis offers a promising way to turn a waste crisis into an energy opportunity. Instead of piling up in landfills or choking oceans, plastics could literally keep engines running.

The promise of waste-to-energy is exciting, but adoption isn't simple. Many of these technologies struggle with high implementation costs, limited infrastructure, and skepticism from policymakers that favor established fuel sources. However, without supportive policies and public buy-in, many of these ideas may remain trapped in laboratories instead of reaching communities.

The potential payoff of adoption is clear. Diverting food waste into anaerobic digesters would reduce landfill emissions, lower energy costs, and provide decentralized power for small businesses. Plastic-to-fuel plants could reduce both pollution and dependence on imported oil. For rural areas, manure or banana peels could mean reliable electricity without waiting for the grid.

The shift might take time, but it's worth it. Waste doesn't have to be a liability; it can be a lifeline. By tackling adoption challenges head-on, governments, industries, and communities can turn overlooked byproducts into the building blocks of tomorrow's energy system.