Biogas is one of the most untapped sources of natural and sustainable energy available with the capacity to supply at a domestic as well as commercial level.

Potential in SA for Biogas Digester Market

Although biogas is used all over the world (India for instance has more than 12 million digesters), biogas in South Africa is practically unknown.
Biogas digester. Energyweb Biogas Digester. Microbes and bacteria

Small scale

In comparison, a very a small number of small scale biogas digester (less than 100) have successfully been built and commissioned to date here in South Africa. Most of these were small scale domestic digester, with only a handful of commercial biogas bag digester plants currently in operation in South Africa.
Energyweb - Biogas Digester

Organic waste

Methane anarobic digestion created from a BIOGAS digester uses organic waste like food scraps as well as animal manure that can be used for cooking in houses, guest lodges, and many other applications

SA Biogas Digester Product Offerings

There are two systems available currently:

A 3,500 Litre domestic biogas digester pressurised system called: “The Little Green Monster”

The commercial sized BIOGAS Digester BAG. The domestic unit was featured on the DSTV program “EKOSTYL” and it has the capacity to be retrofit in a normal domestic environment. It produces Biogas with the Biogas digester from effluent and can supply up to 3 hours cooking capacity daily.

In the past ENERGYWEB used to get fresh cow manure in bags from the Irene cow dairy farm. This was then mixed with water as an inoculant to initiate the microbes and bacteria in the bag as digestate, and after a period of about 7 weeks the unit starts producing biogas.

Currently ENERGYWEB has a take-off agreement with an abattoir that has a commercial biogas digester using cow manure and food waste as the feedstock. ENERGYWEB collects digestate using a truck and tank system and utilizes this ready-for-use digestate with the correct balance of microbes and bacteria to inoculate the biogas digesters.

The result is that the digesters can literally start producing biogas within the first week from food waste introduced, as the correct microbes and bacteria are then already established in the biogas digester.

There are three different types of biogas digesters available from energy web. The three types are the following:

  • the “Little Green Monster”
  • the EZ digester and
  • the Biogas bag.

The “Little Green Monster” digester is typically for a household and is installed underground where the visuals of a biogas digester aesthetically should not be seen. The digester can be installed in-line with the sewage connection of a house. Although this complicates the installation in terms of large water volume that flows through the digester flushing out all the microbes and bacteria needed, as well as the risks of pathogens, if the digestate is used for irrigation.

The “Little Green Monster” is most optimal installation is where the digester is used for food waste which gives you a beautiful organic digestate compost material, and has no risks of pathogens, so the digestate can be used to irrigate your garden and vegetables.

The “EZ digester” is an above-ground plug-and-play easy-to-install digester.  The digester has a volume of 1000 l liquid and 500 gas, and is a simple plug-and-play installation unit with primary use being food waste. From time to time additional organic waste like example cow manure, can also be introduced into the digester – but noted that manure has a very low energy content vs Food waste with an exceptionally high energy content and gas production capacity.

The Biogas bag, is the commercial version of the Biogas digesters. The Biogas Bag units are available in sizes ranging from 10,000 litres up to 50,0000 litres. These digesters require excavation and brickwork and is designed for high volumes of organic mass to produce also commercial volumes of bio-gas.

ENERGYWEB gets flooded with calls from people wanting to replace a saturated septic tank system with a biogas system. It is possible to use anaerobic digestion through a biogas system for black water or sewage treatment but, considering the cost of a biogas digesters vs the cost of a septic tank the price difference can be up to 2 to 3 times more expensive.

Human waste is not at all a good feedstock for biogas production, as the energy content in human waste is really low. The alternative risks of human waste are medication, inherently taken at some times of the year like for example antibiotics, which will destroy the microbes in a biogas digester. Another risk is chemicals being flushed down drains and toilets.

The general recommendation from ENERGYWEB is to rather replace a septic system with a new septic tank system of which we have a product Range and pricing available that is very competitive and to rather use to biogas digester as a fit-for-purpose biogas production unit. This will result in the most optimal gas production. It is sensible to rather use a high-quality waste like food waste in biogas production or large quantities of animal manure.

If the digester is installed but not under the right conditions using the right feedstock the system will not meet your expectations and gas production and will only result in frustration. It is recommended to use a septic system for human waste and a biogas system for the breakdown of organic waste. The production of biogas and the digestate which is pathogen free and that can be used to irrigate food and vegetable gardens.

Healthy digesters always have a fresh organic smell. However, under conditions such as a digester that were overfed and cannot handle the volumes of organic waste, the digester will turn sour and the microbes will die off because of the acidic content of the digestate fluid. The only remedy for a sour digester is to start over. A properly processed digestate liquid that is the end result from an anaerobic digestion process, is a beautiful black liquid that is fully organic, with an extremely high nutritional content that can be used for the irrigation of gardens as well as food gardens. It is recommended that digestate be diluted at the ratio of 1 to 10, because of the very high nutritional value of the digestate.

Chicken manure is not ideal as a biogas feedstock, not because of the manure but because of the bedding that’s used in the chicken runs with the chicken manure. It is not the chicken manure that cannot be digested but the Leinonen in the wood shavings used as bedding material in the chicken runs. The anaerobic process cannot break down the wood shavings and the digester blocks.

A commercial chicken biogas digester study was done by ENERGYWEB for a chicken farmer that used a caged system with clean chicken manure only, transported with conveyor belts to the outside of the building. In this study it was found to be viable given certain conditions with a payback period of just over six years. A copy of the study can be made available, contact us regarding the feasibility on chicken manure as a Biogas feedstock.

Healthy digesters always have a fresh organic smell. However, under conditions such as a digester that were overfed and cannot handle the volumes of organic waste, the digester will turn sour and the microbes will die off because of the acidic content of the digestate fluid. The only remedy for a sour digester is to start over. A properly processed digestate liquid that is the end result from an anaerobic digestion process, is a beautiful black liquid that is fully organic, with an extremely high nutritional content that can be used for the irrigation of gardens as well as food gardens. It is recommended that digestate be diluted at the ratio of 1 to 10, because of the very high nutritional value of the digestate.

ENERGYWEB manufactures, supplies and import largest scale digesters. It is an option for ENERGYWEB to install the digesters however, it is very simple to do a DIY installation on most of these digesters. There is an installation manual that can be downloaded from the website which gives a detailed breakdown of what’s involved to install a I biogas digester. Some of the largest projects include the following:

  1. Agricultural research centre ARC – a total of 36 “Little Green Monster” was installed for rural farmers. A report is available on request on details of this project and the success of the installed units.
  2. SANEDI had a tender for 4 x 15 cubes biogas digester bag units to be installed for government school’s in different areas around Vereeniging Sharpville area. This installation was done very successfully by ENERGYWEB and the results was a viable report showing that Biogas digesters for schools with feeding programs is a very viable alternative to LP gas as well as an excellent showcase for children to learn about sustainable living and renewable energy principles.
  3. Cummins contracted ENERGYWEB to install a biogas system combined with solar plants for 2 schools in the Sandton Kathlehong area as part of their CSI program. These digesters included the use of the digestate which was recovered by a submersible pump and is used for the irrigation of the school’s vegetable gardens where the vegetables are sold as organic produce to local retail outlets in the area.
  4. The “EZ digester” has been successfully installed in more than 12 sites in Johannesburg also for government school food waste processing and disposal. The installation is done in half a day’s time because of the ease of the plug-and-play solution of the “EZ digester”. The schools use the biogas that’s produced for their cooking, and manually use a bucket to distribute the digestate on the food Gardens.

Biogas digesters installed for residential or small applications are typically not heated as this would require additional energy to ensure optimal performance of the digester. On a small scale it is better to rather let the digester produce the biogas under normal temperature conditions.

However, it does imply some inherent risk of less gas production in the winter period. For the 3 digester types, there is an inherent insulation solution provided as example for the “EZ digester” it is installed above ground but with an insulation blanket to retain the heat.

The “Little Green Monster” is installed below ground and is insulated by the temperature of the surrounding soil. The Biogas bags are also installed below ground with insulated lids that assists with biogas production and keeping the temperature inside the digester during winter periods.

ENERGYWEB has a range of Biogas cookers available from single units to multiple burner cooker tables. There is alternative biogas equipment like rice cookers, lights and heating units that can also be imported from our Biogas suppliers.

ENERGYWEB manufactures its own local gas pumps that gives a very good pressurized supply of biogas for cooking ovens. It makes the repairs and Maintenance a lot easier with the local available stock.

There is biogas generators available for small-scale applications, ranging from about 1 to 3 kilowatt units. It was however found that at the small-scale production inconsistency of biogas from the digester, this is not at all a viable solution that would be suggested for small Biogas systems. Even as large as the 20 cube biogas bag, rather find applications where the heat can be used by direct cooking or heating of areas like for instance sheds for baby pigs or chickens.

For commercial generators of a size 200 kilowatts and up, there is local South African companies that have biogas generators available when a commercial volume of methane gas is produced by large-scale digesters. This usually is a secondary option if there is no application where the heat would be more sensible. For waste-to-energy applications on a commercial level contact ENERGYWEB.

ENERGYWEB in principle will not allocate agencies for biogas digesters to specific companies. The reason for this is that to date, many companies were convinced that they would have a large commercial outlet for bio-gas digesters and have sold none. ENERGYWEB’s approach is a strong relationship with our partners that are interested in buying gas units as a potential product line. We supply technical backup on the product. When the first few units are sold and a track record of sustained business is evident retail pricing discounts could be negotiated. Note this is not the standard practice if no digesters have been sold by the prospective partner yet, to prove the capacity to sell digesters. All new customers pay the market list prices.

ENERGYWEB has in the past exported bio-gas digesters to Ireland and African countries. There is however a considerable logistical cost involved in exporting a digester from South Africa, because the digester is a volumetric unit and requires large container spaces for shipment. As a rule, we do not quote on exporting digesters. The client needs to do his own import cost analysis.

This is due to the fact that we have done export quotes on over 100 digesters with only one single confirmed commitment to date. We can provide the volume metric as well as weight requirements for you to establish an import cost for the digester.

A Biogas digester is purchased by an environmentally conscious individual. The digester would typically have a 3 to 7-year Payback. The individual that purchase a digester, is conscious of Environmental and responsible waste principles and not as such a financial investment. As a financial example, solar PV can produce electricity at a cost of R0.70 to R0.90 cents per kilowatt hour. Solar thermal heat can be produced at a cost of R0.30 to R0.50 cents per kilowatt hour. Biogas digester will typically be able to replace LPG gas but as an on-par cost-comparison and not necessarily have a major return on investment.

Our recommendation in a sensible strategic approach towards renewables. For the typical customer a sensible strategic approach would be to first install a solar geyser system, and this after the necessary energy efficiency measures were taken first. The next step would then be considering solar PV for the production of electricity using solar. Biogas would typically be a consideration rank somewhere between 4 and 5th on the list for renewable energy interventions.

The biggest risk, is the accurate management of a biogas digester. The biogas digester is a living organism with microbes and bacteria, and is not a mechanical system like for example a solar or wind farm. This implies that the system needs to be managed and maintained as a full-time involved management practice to ensure the correct feeding, pH levels, temperatures and health of the bio-gas digester.

If this is not done successfully, the digester will turn sour with a high acidic pH value. The result is that all the microbes and bacteria die-off and the system rots. This then requires the digester to be pumped out, cleaned and re-inoculated from scratch.

ENERGYWEB uses lime available from Farm co-ops and is called “Landbou kalk” in Afrikaans. Typical outlets where this could be found would be OBARO or other farm supply companies. The product is sold in 50 kg bags and up to 5 bags can be added to a 10 m3 digestor.

The digesters are manufactured from a UV protected polymer material which will ensure that the digester has a minimum expected life of 10 years. By installing a blanket on the digester this will substantially increase the expected life of the digester. The Biogas bag is produced from a UV resistant tarpaulin cloth product and has an expected life or five years even in direct sunlight.

The Biogas bags are however always installed in a constructed trench and have got lids on it for safety purposes. The lids also increase the insulation, and the production of biogas, which results in a non-UV exposure of the bag that can last a lot longer.

The bigger inherent risk of any digesters would rather be vermin like rats, that chew through the digester material to get to the food waste on inside. A responsible vermin and rat management program is recommended with all digesters.

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