Biogas Blog

BoigasSA Blog

BiogasSA specialises in the design, specification and implementation biogas plants. Biogas plants employs anaerobic digestion of organic waste in order to produce biogas, a flexible fuel which may be used for numerous applications.

  • BiogasSA offers the following technologies
  • Domestic digesters - cast, in-situ type (Puxin) and the DIY Biobag
  • Small to Medium scale digesters - Biobag or an engineered solution.
  • Dairies - Our plugflow digester has a small footprint, is easy to install and requires very little maintenance.

New industry group bullish on SA’s biogas growth prospects.
"The rebates currently on offer from Eskom, together with incentives being extended by the Department of Trade and Industry (DTI) are creating the conditions for a possible biogas “golden age” in South Africa, the head of the nascent Southern African Biogas Industry Association (SABIA) asserts.Chairperson Mark Tiepelt tells Engineering News Online that particular opportunities are arising in off-grid applications, particularly in the farming, food processing and municipal waste sectors."

In theory any type of organic material that can decompose can potentially be fed into a digester.  Practically, however, there are a few basic types of organic material that are commonly used in digesters of which by far the most common type is manure.  Cow manure spicifically is very suitable since cows have 4 stomachs which means that by the time the manure is produced, the microbial action is already well on its way.  Most of the large digesters around the world use either cow or pig manure and the biogas produced is used to generate electricity.  Other types of feed material includes blood from abbotoirs, wey from cheese factories, yeast waste in breweries and much more.

A floating dome digester is designed in such a way that it has a dome (normally made of steel) that fits in the neck of the digester and basically floats on the gas produced in the belly of the digester below. As gas is produced in the digester it collects in the dome, eventually creating enough pressure for the dome to in effect "float" on the gas.

As the name implies, this type of digester has a gas-collecting dome that is fixed. The digester is normally constructed using bricks and mortar and ends with a solid fixed dome in the shape of an igloo. Although this is the most well known digester design and the most widely used, it has a number of inherent disadvantages.

The main disadvantage is the fact that it can only ever produce gas of variable pressure. As the biogas is generated it rises and accumulates in the brick dome from where it is piped to point of use. The volume and rate of gas production is dependent on the type and frequency of material fed into the digester as well as on the temperature. This means that the amount and pressure of gas available will continuously vary, making it less efficient to run any type of biogas equipment such as gas water heaters, lights and generators.

The 10m3 Puxin Biogas Digester

Biogas SA is the sole licensee for South Africa of the Shenzhen Puxin Science and Technology Company (Puxin) of China. Puxin has developed over a period of 20 years a unique, patented hydraulic biogas digester that has eliminated all the disadvantages and enhanced the advantages of the more traditional fixed and floating dome type digester designs. As acknowledgement of its technology and contribution to promoting efficient alternative energy resources, Puxin was awarded the prestigious Global Top Ten Investment Scenarios to Apply New Technologies for Renewable Energy Utilization BlueSky Award in 2006, initiated by the United Nations Industrial Development Organisation.

The use of biogas is practically limitless.

As a combination sewerage management/biogas producing system any new house, guest house, lodge, development, golf estate, clinic, hotel, etc can install a biogas digester system as their primary sewerage system, source of alternative and sustainable energy in the form of biogas and apply the digestate directly as organic compost or recycle the water through a wetland.

Commercially biogas digester systems can be installed at dairies, piggeries, chicken farms, abbotoirs or any other type of industry where waste containing organic material is produced, to generate green sustainable electricity.

Biogas is naturally produced when any organic matter decomposes under anaerobic conditions (in the absence of oxygen). The gas consists mainly of methane (CH4) and carbon dioxide (CO2) in approximately 3:2 ratio. Methane is the important component as it is a highly flammable gas that can be utilized as fuel for cooking, lighting, water heaters and, if the sulphur is removed, it can be used to run biogas-fuelled generators to produce electricity.