One thing is not in doubt; the National University of Lesotho (NUL)’s first biogas plant is an engineering feat! When completed, it will be one of the few, if not the only, of its kind in the Southern Hemisphere!
For nearly half a decade, Dr Sissay Bekele Mekbib and his students were submerged into their Biology labs to experiment with microalgae (bolele) as a means to produce biogas. This platform covered that extraordinary story again and again.
What you don’t know, however, is how Dr Mekbib is now working to do the same thing outside the lab. Behold! We will tell you!
It is one thing to turn micro-algae into a biogas in the lab. It is quite another to do so, at an industrial scale. The aims are the same, but the methods, the expertise, the thinking and even the equipment, are different—very different!
If the former is Thabana-Ntlenyana, the latter is Kilimanjaro.
As Dr Mekbib takes you through the engineering process he and his engineer colleagues have designed, you cannot help but stand in awe at the almost infinite ingenuity, displayed to a superlative degree.
The process starts in two NUL ponds—the green ponds. The ponds are usually green with algae, sitting comfortably on top of the water. The thriving algal blooms can only mean that the waters must be very rich with nutrients. Perhaps they receive quite a dose from the nearby NUL Farm and community residents.
To harvest the algae, plastic pipes are submerged into the ponds to make a catch.
“At this very beginning stage, a real problem surfaced,” Dr Mekbib revealed.
“Since algae are often suspended on top of water in the ponds, our system had a problem of catching only the water, leaving the algae behind. After numerous attempts and thinking, we nailed the problem.”
He and his colleague Mr Anadola T’siu, designed a piston system that would force the water to enter the pipe along with the algae. It was a giant leap!
But the glitch was one in a queue of challenges. Remember the fate of the algae from the ponds is the biogas digester. But how do you get it there? You can use pumps. However, they are expensive and they need expensive energy.
So they came to realize that if their digester were placed at a little lower elevation compared to the ponds, they could use the source of the freest energy possible; gravity!
Then, another mammoth challenge came in the form of the mighty bio-digester. It looks simple, that is, “until you realize that it has to be airtight to provide what biologists like to call “anaerobic conditions” (conditions free of oxygen),” he said.
Microorganisms will do their work best under these conditions as they feed on the algae to produce biogas.
In this one, they didn’t have a free ride as Dr Mekbib unveiled, “at one point, we had to tear down the wall and started all over again. We had to find the right kind of bricks and then put an impervious material trough the digester’s wall.”In the end, that problem too was solved.
At this point, pause and briefly meditate on this observation by the famous Voltaire, “No problem can withstand the assault of constant thought.”
Dr Mekbib and his colleagues never stopped thinking, and the problem gave way—what problem wouldn’t?
Observe the digester and you realize it is circular on the walls and sort of dome-shaped on the top. “This is meant to allow free movement of the contents inside the digester. In fact we are going to periodically stir the mixture to enhance biogas production.”
And what is the fate of the biogas from the digester? Remember, this is not a showoff, it is about making the biogas and actually putting it into the gas cylinders!
But, alas, that is not as easy as it sounds. The devil, they say, is in the details. “You see, the gases produced in the digester are many and varied,” the Dr said.
“They include, but are not limited to, butane, ethane, methane, the infamous hydrogen sulphide (that rotten eggs smell which keeps you away from normal biogas initiatives comes from this culprit), and ammonia.
So you don’t want to pick all of the obnoxious mixture. Rather you want to pick mainly butane, methane and the likes, the “good” smell-free gases.
For the whole process, Dr Mekbib already has two machines, a purifier and a compressor. The former purifies the gas and the latter pressurizes it into gas containers, not different from the ones you use at your home.
In the end, the remains of the algae pass through into a collector dam, for use as green manure, and the cycle is completed and, you can bet, it is very good!
Perhaps, Dr Mekbib’s passion for the work is the reason why UNDP through its Global Environmental Facility Small Grants Program (GEF-SGP) keeps pouring money into this project.
It is one of the most ambitious green projects Lesotho has ever taken
