Monday, 02 July 2012
Our biogas digester at the Johannesburg Zoo is fed with elephant and buffalo dung and kitchen waste water. The gas it generates is piped into the kitchen of the zoo's restaurant and used for cooking.
In theory it could be fed elephant dung or manure from any of the many animals that call the Johannesburg Zoo home.
We were so excited when our distributor in Gauteng, David Light of Biobox, installed the digester at the zoo because we figured it would be fun to be the first organisation that calculated the gas generating potential of elephant poo, hippo poo, chimpanzee poo...
However, the digester has to be easily, practically manageable, and the zoo staff have found using buffalo dung - practically identical to cow dung - - to be the most sensible option. The digester sits near the restaurant so the gas can be easily piped to the kitchen. The dung is collected from the buffalo enclosure as it normally would be and then transported by bakkie, in wheelie bins to the digester where it is loaded once daily (60 kg per day). The gas generated is piped to the restaurant kitchen where it feeds a dedicated biogas cooker.
It doesn't supply all the gas needs of the kitchen - they would need about 4 digesters to achieve that - but it processes some of the dung and the brown liquid which leaves the digester makes for fantastic fertiliser.