Participants will have the technical capacity to fabricate CBS units, including the cutting of digester and gas holder tanksand the installation of fittings. They will also know how to install the system and ensure the proper amounts of inputs are added, how to trouble shoot common problems, and the daily feeding and maintenance of the system.Training
Fabrication – 1 Day
Installation – 1/2 Day
Feeding & Trouble Shooting 1/2 Day
Introduction to tools, parts and process
Each training is started with an introduction to the tools required to fabricate a compact biogas system, as well as the parts and an overview of the process of completing each task.
The tools and parts are displayed and demonstrated by the trainer’s one by who give an explanation as to its purpose. Participants are encouraged to follow along with their training manuals, which would help them to identify the parts on their own.
Trainers then ask participants to introduce the parts on their own. An outline of the gas holder and the digester are drawn on the ground and each of the participants are asked to identify a part, explain what its name was, its size and purpose. The participant is then asked to demonstrate where the part fits on the CBS using the drawing on the ground. This enables participants to visualize the tasks at hand before they actually began the physical fabrication.
Cutting of the Tanks
The first step of the training is cutting down the tanks to size and drilling the necessary holes to match the fittings.
First the gas holder is cut down. The slots at the top of the tank are cut out in order to allow the gas to pass into the gas holder once it is inverted in the digester.
Participants are walked through the process of measuring the diameter of both the digester and the gas holder in order to cut the digester to the right size to accommodate the gas holder…with a little space for movement on both sides.
Finally, the trainers instruct the participants on how to cut the holes for the feed pipe, emergency drain and overflow.
Assembly of the CBS plant
Using the tools, parts, glues and training manuals the participants work with the trainers to assemble the compact biogas plant. The assembly is completed in the following order:
1. Installation of the gas valve on the gas holder.
2. Installation of the feed pipe tank connectors
3. Installation of the emergency drain tank connectors
4. Installation of the overflow tank connector and back nut
5. Gluing of feed pipe inflow inside of the digester
6. Gluing of 3” feed pipe to elbow and tank connector
7. Gluing of the end plug on the emergency drain.
8. Gluing of the 2 1/2” overflow pipe and elbow.
9. Reinforcing the seal using m-seal and Araldite.
Special attention is given to preparing the pipes for gluing, which includes scratching the surface to ensure the glue attaches better and choosing the right glue for each application.
Choosing the right location
While the glue is drying the participants were instructed on how to prepare the right location for their CBS unit. The main factors to consider are:
- Proximity to the kitchen – it should be within 10 meters but the closer is better.
- Exposure to the sun – the more sun the warmer the digester and the better it works
- Level – the ground has to be level and if it isn’t it must be leveled with hand hoes
- Secure – a place where it cannot be damaged or vandalized.
Once the right location is selected and the glues have dried the participants were instructed on how to safely move the biogas digester into location and how to place it properly with the feed pipe and overflow position for ease of access.
Checking for leaks
Once the digester is moved to its location approximately 200 liters of water is poured into it. This is water that has not been mixed with slurry as it is used for checking leaks. Emphasis is put on leaks around the feed pipe and emergency
drain where the most pressure will be exerted on the joints. Usually there are minor leaks around the screw cap of the emergency drain, which will seal once the slurry is introduced. If there are larger leaks then we instruct the participants to remove the water, dry the joint and reapply the adhesives.
Filling the slurry
Once the trainers were confident the seals were secure the participants are instructed on how to fill the biogas digester.
Inserting the gas holder
The final task was to place the gas holder tank into its inverted position so that it could sink down into the digester.Several participants were required to work in unison to complete this task. Once the tank had fully entered the digester the valve was closed and the system was left for the bacteria to populate.
The last stage of the installation, once the digester was filled and the gas holder inserted is to secure the feed and overflow pipes. Participants were instructed that this was a critical aspect that should not be overlooked as it helped protect the CBS.
Teaching how to Feed the CBS
Feeding the CBS is one of the most important aspects of the training because it must be done on a daily basis and the person feeding must understand if the digester needs to be fed more or less depending on weather, temperature and level of acidity.
Participants were instructed on the initial steps of feeding, starting with ½ a kilo and then gradually building up to 6kg per day over a period of one month.This is to allow for the bacteria to multiply and prevent acid build up in the tanks.
In order to better explain what foods could fed into the digester each of the participants were asked to bring a sample of food waste at their homes. The trainers also go around and collected samples from the local environment. A mixture of fruit and vegetable peelings, leftover food (ugali, rice), some seeds and flowers from plants, centers of the banana plant and water hyacinth were collected. The trainers also bring examples of what not to put in the biogas; chili, soap, plastics, bottles, bones, etc. The group slowly goes through the collection of food items and discussed whether or not it was good or not good and the caloric value.
Participants are also instructed on how to cut the food waste into a size the size of a thumbnail to ensure it can pass smoothly in the feed pipe and into the digester as well as how to let the food waste cure in a bucket for a day in advance so the waste softens for faster digestion.
Using the training manual the participants are instructed through the major challenges they may face in the operation of the CBS. The three most common problems being: moisture blocking the gas hose, blockage of the feed pipe, gas leaking from the valve seal. Each of the participants were given a scenario afterwards and asked to trouble shoot it so the biogas was working normally again.
Installation of the Cook stove
Participants are instructed on how to modify a normal LPG stove so that it could work with biogas.
Questions & Answers
After each session the group pauses for a period of questions and answers to review the process and ensure all the participants understand the task they just completed. This includes having the participants help each other answer the questions and the use of an extra set of spare parts to demonstrate the process of required.