Frequently Asked Questions
Background = Planning = Feeding = Maintaining
AGAMA BiogasPro – a domestic waste to energy solution. The AGAMA BiogasPro is a high-efficiency biogas digester designed by some of SA’s leading biogas experts specifically for domestic- and institutional-scale installations. AGAMA BiogasPro is an underground plastic or fibreglass tank that produces a combustible gas and liquid fertilizer by digesting sewage, kitchen waste, wastewater and similar organic materials.
An AGAMA BiogasPro digester can be installed in two days. Within four to six weeks you will be cooking with your own biogas. Result: on-site energy (gas), irrigation water and fertilizer.
Biogas is a mixture of natural gas (methane CH4) and CO2. It contains about 2/3 methane, 1/3 carbon dioxide and traces of other gases such as hydrogen sulphide.
Biogas is flammable, invisible and lighter than air ( Specific Gravity 0.85 – Air = 1.0). It contains 24 MJ of heating capacity per 1000 litres. It is produced at low pressure, so is relatively safe and only burns well in biogas appliances.
Biogas is not to be confused with Liquified Petroleum Gas (LPG) which is flammable, invisible and heavier than air ( Specific gravity 1.7 – Air = 1.0). LPG contains 107 MJ of heating capacity per 1000 litres.
Biogas and LPG have sufficiently different properties to require different appliances to operate. Biogas however, is compatible with Natural Gas appliances.
A digester needs a healthy population of methane producing bacteria, a stable environment and regular feeding. The bacteria in the system must be kept in an anaerobic (oxygen free) environment and be suitably well fed to thrive at ambient temperatures.
The bacteria are living organisms, so need to be looked after daily and not killed by starvation (erratic or infrequent feeding), overloading (turning the water acidic and killing the bacteria) or poisoning (chemicals put into the digester). They thrive in high temperatures with consistent feeding.
An AGAMA BiogasPro can be fed on organic kitchen waste,animal manures, landscape off cuts (only those that are not woody) and human waste.
The AGAMA BiogasPro enables waste to be broken down by bacteria into gas. Bugs eat waste and turn it into gas!
It is an anaerobic (without oxygen) process digesting organic materials. Anaerobic digestion in the BiogasPro is performed in water by different types of bacteria. Our biogas digester retains all of the incoming nutrients and makes them available in the liquid leaving the system.
Production from the digester is very dependent on what it is fed, how much it is fed, the temperature it is operating at, and other local environmental factors.
Guideline amounts of biogas produced from the feed are: Human waste – 28 l/kg; cow manure – 40 l/kg; Pig manure– 40 l/kg; Chicken manure – 70 l/kg; Food – 100 l/kg; Grass – 15 l/kg.
A cow (non-dairy) produces 10-12 kg per day; pigs produce 4-5 kg per day.
You do need to have a fair amount of wet waste to generate a useful amount of biogas. Adults only make 0.2 kg per day of sewerage, so even a family of 6 only produces 1.2 kg of waste. You can generate 28 litres of biogas per kg of human waste, and 100 litres per kg of kitchen food waste, and 40 litres of biogas per kg of cow manure.
You would expect a single AGAMA BiogasPro digester fed by a family of four adding animal manure from 2 – 3 cows ( because there is a large amount available) and kitchen waste (because it contains a large amount of energy) , to produce between 1 and 2 hours of cooking time per day on a single large ring cooker.
A complete AGAMA BiogasPro installation in good soil conditions (no large rocks), takes only two days (the fastest installation of a biogas system available anywhere).Complicated installations (eg in rocky ground, with lots of subsurface services to be negotiated) can take up to a week to dig the hole, remove the rocks and fill the hole around the AGAMA BiogasPro.
The tank installation is identical to the installation of a septic tank. The gas piping is simple and takes only a few hours. AGAMA Biogas use Ginde Multilayer pipe that is supplied on long rolls, so there are only two connections to be made – one at the digester and one at the kitchen or point of gas use.
No. The AGAMA BiogasPro is an underground tank, with only 2 or 3 manhole covers visible above ground. The standard installation involving a sewer, has the inlet coming in at 380mm below ground level. We recommend that you cordon off the covers and/or ensure they are always locked, for safety reasons. It can in some unusual cases, be installed above ground if required.
The risk of fire is very low, but safety precautions are necessary. Naked flames must not be allowed near the AGAMA BiogasPro. We advise that the area be kept clear of overgrowth and that clear signage is in place indicating flammable gas. This signage is supplied with the AGAMA BiogasPro for placing at the digester and the point of use. For day-to-day operation of the gas appliance, normal health and safety standards apply.
The AGAMA BiogasPro has a large feeding hole for the waste and a large cap for access to the gas section. Children would be able to climb into these holes if they were not secured.
Fencing off the area with a small enclosure reduces the risk of both fire or children falling in. The AGAMA BiogasPro is supplied with lockable manhole covers, which must be kept locked to prevent children from climbing in.
No, but you can have several connected together. The AGAMA BiogasPro has been designed so that it is convenient to transport, bury and operate. It has a 2.2 m diameter and 2.4 m height and 6,000 litre volume.
Several BiogasPro digesters may be connected in groups for larger installations .
You should check this with your municipality, every municipality has a different set of rules, and our determined clients have always received municipal approval. Certain municipalities require council approval where the proposed installation will need to be incorporated into approved house plans. In the rural context there is increasing municipal awareness of the value that a biogas system brings. A number of rural projects have demonstrated these positive impacts to a wider audience.
If YOU can eat it, or you have eaten it, then it is good for the AGAMA BiogasPro.
Any organic matter that is not too large or solid is safe. Good examples include food waste, garden scraps and grass. Avoid feeding wood and bone to the digester as they take far too long to digest.
AVOID POISONS AND DETERGENTS
Plastics, rubbers, glass, stone and metals are non-organic items and block the digester, and contribute no biogas production or fertilizer. They must never be fed into the digester.
The smaller the items fed into the AGAMA BiogasPro, the faster they can be broken down and turned into biogas. Try to reduce the size of feed materials, (about 5cm or less all round).This reduces your chances of blocking up the system. Like us, your digester thrives on a varied diet. If you add grass cuttings, leaves and crop husks, it is best to store them for about a week under a cover to start the breakdown process. Then feed them in small amounts every day to the digester together with other waste.
The maximum amount of water that can go into the BiogasPro BP6 is 1,000 litres per day. The amount of solids depends on the temperature and the feedstock type, and is around 25-35 kg per day. This information is detailed in the AGAMA BiogasPro Product Datasheet for each model.
Gas production will slowly decrease as the bacteria start to die off due to lack of food. Once all the nutrients have been consumed all the bacteria will die and gas production will cease. The AGAMA BiogasPro will have to be restarted. Many current domestic users only throw in their food waste every third day, and have sufficient gas to meet some of their cooking needs.
A minimum daily average of 1kg of waste materials and 5 litres of water (eg: 3 kg waste materials and 15 litres of water every 3 days). This amount is readily available from an average household, and you will find that you have a lot more material, particularly water, that will go into the system.
If used correctly there should only be a need for it to be cleaned out very infrequently. However, this will be necessary more regularly if sand, plastic, sanitary towels and other non-biodegradable items are allowed to clog up the system. Overloading with organic wastes (e.g. more than 35 kg of food waste on a single day) will also necessitate more frequent emptying. To date, AGAMA have not pumped out any well operated BiogasPro digesters.