At the Munich Zoo, visitors have the opportunity to observe the courtship behaviors of the banded mongoose, listen to the morning calls of the scarlet ibis, or meet the Indian elephants, who contribute to the zoo’s energy needs by generating electricity from their dung.
This is possible because Munich Zoo has tapped into “poo power,” a source of energy derived from animal waste that can be transformed into a fuel called “biogas.”
Here’s how it works: The zoo has constructed three large containers, each with a capacity of around 100 cubic meters of animal waste—equivalent to about a week’s worth of dung collected from all the herbivorous animals present in the zoo.
Inside these containers, the waste is combined with warm water, allowing the bacteria in the dung to decompose in an oxygen-free setting for 30 days.
The byproduct, biogas—which consists primarily of methane and carbon dioxide—naturally rises through vents in the ceiling to a corrugated hut located on the roof, where it’s collected in what park supervisor Dominik Forster refers to as a “big balloon.”
This biogas is then utilized in a gas-powered engine to produce electricity. According to Forster, the balloon, which resembles a small Zeppelin more than anything else, can hold sufficient biogas to satisfy 5% of the zoo’s energy requirements.
Dr. Geraint Evans from the National Centre for Biorenewable Energy explains, “When you convert the biogas into electricity, it generates heat that we also retain.” Forster mentions this heat is used to warm the gorilla enclosure, “but could easily heat about 25 homes,” he adds.
Following the conclusion of the fermentation process that produces methane, the leftover solid material—or “digestate”—is repurposed as organic fertilizer for crops, which will later serve as feed for the animals.
“We don’t waste anything,” Forster declares, noting that he believes his zoo is the sole one in Germany employing this method of electricity generation.
A fully grown elephant has the capability to consume approximately 100 kilograms of fruits, vegetables, and pretzels each day, resulting in a substantial amount of dung; Forster notes that collectively, all the zoo animals produce around 2,000 tons of dung annually.
