When compressing loose plant material into solid blocks, this is called “briquetting”. That way, agricultural byproducts, also known as biomass, which otherwise would be rotting waste, is turned into high quality fuel.
These briquets – also known as green coal – are used for cooking or in industrial production. Here, they replace fossile fuels (like brown or black coal or Diesel), fuelwood or charcoal.
In comparison to these fuels, briquetts are clean and easy to handle. Due to their cylindric form they can be easily packed and stored. In addition, they also help reducing greenhouse gases.
Biomass is a renewable raw material. Very important: The way it is “produced” must not invict conflict with growing food plants. While in Europe, energy plants like canola or corn have to specifically grown on agricultural land, in Ethiopia we are using agricultural waste which is created anyway by the agroproduction businesses.
Ethiopia’s economy is dominated by agriculture. Hence there is an abundance of sources for biomass. Below a short selection:
- the shell around coffee beans, so called coffee parchments
- cotton or mustard stalk
- sugar cane after having been pressed , so called bagasse
- rice, sesame or groundnut hulls
- miscanthus (elephant grass)
- and many more
Turning Biomass into Briquets
At first, humidity of the raw materials needs to be measured. In case it is too wet, it has to be dried. Biomass that comes in fairly big “chunks” needs to be grinded before it can be processed.
Next, the biomass is being mixed and shoveled onto a conveyor screw which transports the material into the briqueting machine. Here a piston presses the biomass into a cylindric die.
The compression heats the biomass (200 degrees C), which basically seals the briquet from outside, increasing the stability of the briquet. After the briquets leave the machine they have to be cooled down, passing a long pipe, and afterwards are packed into bags by workers.
Briquetting is a technology that is not new at all – it has been practiced in many countries over decades already – with big success. In India alone, there are more than 1,500 machines operating (2014). Also Kenia, Tansania, Uganda, China, Bangladesh and Brazil are part of the premier league of “biomass briquetting”.