The researchers fed the computer for six months using only algae.

Perspective: With soaring energy prices and an expected next generation of graphics cards that will be power-hungry monsters, what’s the solution to tomorrow’s PCs hurting the planet and the wallet? Maybe it’s algae?
New scientist reports that Howe Lab’s photosynthesis research group from Cambridge university was able to power a computer for six months using a colony of non-toxic photosynthetic algae called Synechocystis sealed in a small container the size of an AA battery.
The computer in question was clearly not a high-end game console or even a budget machine; it was an Arm Cortex-M0+ processor commonly used in IoT devices. However, the device was able to supply power from February to August 2021 as it was placed on a windowsill, providing continuous current through its anode and cathode.
Researchers in @CJHoweLab under the supervision of Professor Corpus Chris Howe, including a PhD student @scaralbi – have used widespread blue-green algae species to continuously power the microprocessor for a year – and this number is growing. https://t.co/ygU4u6QKPX
— Corpus Christi (@CorpusCambridge) May 13, 2022
The Arm processor performed continuous calculations to simulate real workloads and measured the device’s output current. There were no power outages during the six months of operation, and the cyanobacteria have continued to generate energy since the end of the experiment. The device can produce energy even in the dark, perhaps because the cyanobacteria continue to process excess food.
The team believes the energy either comes from the electron-producing cyanobacteria that create the current, or they create conditions in which the aluminum anode in the container is corroded by the electron-producing chemical reaction.
While the experiment may not ultimately lead to algae-powered gaming PCs, it could have applications in the world of low-powered IoT devices – there are expected to be one trillion IoT devices by 2035, and they will be charged with lithium-ion. ion batteries would be impractical. This method can also be used to power environmental sensors or phone chargers. The researchers say the algae’s power is likely to be most useful in off-grid situations or in remote locations.