Tag Archives: biogas

The yurt’s biogas unit/biodigestor… for R300!

All the blackwater from the yurt’s toilet goes into the biodigestor.  And so does all the organic waste from the kitchen.  Methane gas output is increased by fats, oils, greases and sugars, and you can use the gas for cooking and heating.  Another byproduct is liquid fertilizer, which you can use in the garden.  You won’t need to buy fertilizer again!

The biodigestor: The bottom tap drains liquid fertilzer, the tap on top is the gas outlet and the blackwater input pipe is lying across the top of the tank, ready to be inserted into the tank.

The biodigestor: The bottom tap drains liquid fertilzer, the tap on top is the gas outlet and the blackwater input pipe is lying across the top of the tank, ready to be inserted into the tank.

The tank cost about R200 from Peninsula Drums and all the other fittings are from Overberg Agri and cost about R100.  So… blackwater sorted for about R300!  And all byproducts can be re-used.  What on earth are we doing pumping all our effluent into expensive reticulation to expensive sewerage treatment works kilometres away?  And unlike septic tanks, there is no danger of polluting groundwater.

In 1980, India had over 9 million biodigestors in operation.  Today the number can’t be counted because they are even found on apartment balconies, primarily for organic waste to provide cooking gas for the inhabitants.

My solution took less than an hour to make.  I cut holes for the liquid fertilizer and gas output pipes, and inserted tank connectors with taps.  How to get the tank connector into the drum?  Take a very thin piece of wire and insert it into the drum and guide it to come out of the hole where the tank connector has to go.  Feed the tank connector onto the wire and pull it into the hole, where it needs to be tightened.

For the blackwater input pipe, I cut a hole into the one screw top, inserted the fittings into it and connected a piece of PVC pipe.

The other screw top remains to be used for organic waste and checking levels inside.  Once the biodigestor starts producing gas, a similar but shorter pipe will be inserted to stop gas escaping when organic matter is added.

The drum should be painted black to prevent algae-producing UV rays penetrating the drum.  (If that happens, your methane will be replaced by carbon dioxide.)  I’m going to wrap the drum in thick black plastic which I already have.  Bear in mind, the biodigestor needs warmth, so it’s located on the sunny side of the yurt.

Here are two videos which will tell you everything you need to know about biogas units:

How to build a biogas unit

You can also buy recycled flowbins from Peninsula Drums – really quite a remarkable award-winning company.

How to build a biodigestor

 

The biodigestor is only possible because of the Saniflo Compact toilet.  Firstly, it macerates and pumps the effluent to the drum.  The drum can be above the ground.  Secondly, the Saniflo unit only uses 3 or 1.8 litres of water per flush, compared to the normal 6–10 litres of conventional loos.  The biodigestor tank can be much smaller and is far more efficient with lower water volumes.

Now, all the unit needs is some blackwater and a bucketload of cow manure to kickstart the anaerobic process.  It takes about a month for gas to be produced, or less since the blackwater is macerated.