What is an Earth Battery?

Among the latest clean energy innovations, the Earth battery is perhaps the most accessible.

It generates electricity from the soil and can be built by anyone using simple electrical components and tools. There’s no need for expensive turbines or complex circuitry that are often required of renewable energy systems. You can build your homemade earth batteries using just a handful of copper spikes, galvanized nails, and copper wire.

If that description makes you doubt the earth battery’s potential, don’t. Earth batteries can produce up to 5 volts - enough to power everyday electronics such as radios, lamps, and mobile phones.

They’re one of the most powerful clean energy systems for off-grid communities and homes. In this article, we explore what an earth battery is and how you can build one yourself. 

What is an Earth battery?

An earth battery is a type of water-activated battery that produces an electrical current using electrochemical reactions in the soil. Made from just four simple components - copper cathodes, zinc anodes, copper wires, and wet earth - an earth battery produces enough energy to power lamps and radios in off-grid locations.

Like all batteries, it relies on the exchange of electrons from zinc and copper electrodes to produce an electrical current. The electrodes are immersed in an ion-rich electrolyte solution where electrons from zinc transfer to copper, generating the electrical charge we use to power our electrical devices.

But unlike other batteries, earth batteries use wet soil or bacteria-rich compost as the electrolyte solution instead of acids. Organic matter releases electrons as it decomposes, which can be captured by the electrodes. Electrons are also discharged when bacteria eat organic matter like they do in compost piles. 

This scientific finding may sound like a recent discovery, but it came about as early as the 1840s by an inventor named Alexander Bain. Bain was looking for a cheap, ubiquitous energy source to power telegraph lines when he hypothesized about the earth’s potential electric energy. 

He put zinc and copper plates in damp soil to test his theory and discovered that the earth produced an electric charge that could be harnessed. Although it wasn’t enough to power telegraph lines, Bain’s discovery was the spark that gave birth to the concept of the earth battery.

Now almost two hundred years later, earth batteries have grown in popularity thanks to increased public demand for off-grid and clean energy technologies. Most people build their own homemade earth batteries just like Bain did, although a few renewable energy startups have tried producing prototypes for commercial distribution. 

Earth batteries can produce a charge of about 1 to 5 volts, depending on the construction and type of soil used. Recent research shows that earth batteries could work as an alternative or complementary source of energy to wind and solar power. 

How much does an Earth battery cost?

Earth batteries can cost anywhere from $10 to more than $500 depending on the amount of energy you want to derive from them. 

You only need to consider the material and equipment costs of earth batteries when installing them. Unlike other clean energy systems, earth batteries are very easy to set up on your own without needing to hire any specialized laborers.  

A small earth battery, for example, can be made from an ice cube tray, galvanized nails, and copper wire that should cost you no more than $20. An earth battery of this size is about the size of your hand and can produce enough energy to light a lamp or run a clock.

If you live in an agricultural area where chicken wire and animal manure are easy to find, you might even be able to build an earth battery for just $10. 

This earth battery requires a paint bucket, a chicken wire cathode, a graphic cloth anode, and mud mixed with manure, saltwater, and some sand. It can provide the same amount of charge as the $20 ice cube tray earth battery. 

For people who want to build an earth battery large enough to power the lights and small electrical appliances in their home, a budget of about $500 should suffice. This will cover the cost of multiple copper spikes, galvanized nails, high-value capacitors, and rolls of copper wire. 

You may also want to consider getting a high-quality voltmeter and a pair of wire strippers to test and assemble your earth battery. A voltmeter costs about $15 while a decent pair of wire strippers should cost no more than $10.

All earth battery components can be easily bought at hardware stores. It’s only the soil that you’ll need to scoop up from your backyard or purchase from a plant nursery. 

How well do Earth batteries work?

Of the various earth battery (ground battery) designs out there, the traditional soil-based earth battery and its newer compost counterpart are the most effective.

They work in the same way, producing electricity from electron exchanges, but have different strengths and weaknesses. 

The soil-based earth battery can produce up to 5 volts per single battery, which is more than enough to power a small electronic device with an LCD screen such as a calculator, clock, or pedometer. 

It relies on moisture in the soil to transport ions between the copper and zinc electrodes. When the soil dries up, usually about 2-3 days after it has been moistened, the battery stops producing a charge. Wetting the soil again helps rekindle the charge.

But once the soil itself has been depleted of all ions and electrolyte properties, the earth battery will go dead. This is when you’ll need to replace the soil with a fresh batch.

On the other hand, compost-based earth batteries, often referred to by researchers as microbial fuel cells (MFC), produce electrical currents when bacteria break down organic matter in the compost and other types of waste.

Researchers discovered that these earth batteries produce about 0.5 to 1 volt per single battery, which is enough to power a microcomputer such as a Gameboy, the handheld gaming device from the 1990s.

The bacteria help release electrons as long as they have food to break down. Replenishing their food supply can keep compost-based earth batteries running for months or years as the bacteria eat and continue multiplying. 

The only problem with microbial fuel cells is that the electrons given off by bacterial activity don’t transfer well to the electrodes. As a result, the electrical current produced is relatively low.

Can I build my own homemade earth battery?

Anyone can build an earth battery on their own.

There are numerous youtube videos and guides online that you can easily follow and use to construct your own earth battery design.

The biggest considerations you would need to make before building an earth battery are the amount of energy you want from it and the amount of soil you can access. To power a few lamps in a small- or medium-sized home, you would need a large surface area of soil to assemble your earth battery system on.

A small earth battery for recharging phones, on the other hand, would just require a handful of soil or compost packed with bacteria. 

It should take you no more than 30 minutes to build a small earth battery. Large earth batteries may take a few hours to build as you’ll need to stake out the locations of the electrodes, plant them, and connect them to copper wires and then to your home.

How to install an Earth battery

To install an earth battery, you have to first decide where you want to place it.

Small earth batteries are portable and work both indoors and outdoors. They can be installed a few feet away from the appliance that will rely on the battery’s power.

Large earth batteries require an expansive area of soil and can therefore only be installed outdoors. The most important factors to determine before installing a large earth battery are the amount of space required and the availability of a water source close to the location you’ve identified.

This is because ground batteries need constantly moist soil to perform well. Runoff from an irrigation system or a septic tank drain field can help provide the water that’s needed.

Once you’ve identified a location for your earth battery, you’ll need to construct it. For large earth battery systems, you might find it useful to install them as line batteries with pairs of zinc and copper spike electrodes planted 5 to 6 feet from each other. This will create a series of ‘batteries’ that draw ions from the earth. It’s best to experiment with what works best on your property.

After you connect the electrodes to a copper wire, you can hook the battery up to your home’s lighting system circuit. 

The same installation process applies to small earth batteries. The only difference is that instead of planting a series of electrodes into the ground, small single-cell earth batteries will usually only require a cathode (such as a galvanized nail or chicken wire), an anode (such as a graphite cloth), and a container full of soil or compost.

An earth battery installation at your home can help you reduce your electricity bill, and maybe even lower your carbon footprint. It’s a free energy source that’s ideal for off-grid living, wherever you may be.

Earth batteries aren’t the only way you can save the environment

Earth batteries are a great tool to use for reducing your impact on the environment, but they’re not the only ones. You can help save the environment by banking ethically with an environmentally-friendly financial platform like GreenFi.

GreenFi offers a checking and savings account that never uses your deposits to fund fossil fuel exploration or production.

We also have our Plant Your Change program that rounds each of your transactions to the nearest whole number and uses the spare change to plant trees for you. 

Try GreenFi today and make your money work for the planet.