An increasing number of South Africans rely on public transport services to get around, from the everyday commute to their employment places to the social visits to the shopping centre, public transport plays a role. A fully functional transport system is what South Africans require as the country moves towards an age of sustained growth and accelerated development.

The recent continuous increases in petrol prices has created a lot of uncertainty for the populace who rely on public transportation. However, the availability of Natural Gas as an alternative fuel source has relieved a significant amount of financial burden for a lot of public transport service providers and their committed commuters. Metrobus and Tshwane’s TRT buses are leading the conversion charts in the public buses sector, the Johannesburg municipal bus operator that has a variety of buses successfully converted to using Compressed Natural Gas (CNG) as an alternative to fuel. In 2015, the City of Johannesburg (CoJ) launched its first batch of approximately 30 dual-fuel CNG buses followed by another 150 buses in 2016, these busses are already in operation boasting their own in-house filling station at their depot in Braamfontein. This marked Johannesburg as one of the first cities in sub-Saharan Africa to operate a fleet on CNG.

Metro bus covers 330 scheduled routes and 128 school routes, transporting thousands of passengers on a daily basis. Undoubtedly, these buses consume a great amount of fuel daily. The recent conversion to Natural Gas, a more economical but efficient fuel alternative has decreased the amount of money invested in operational fuel, this has a direct impact on the budget of the commuters as well.

Why the switch was essential

CNG is much cleaner than petrol and diesel, with up to 27% less CO2, NOX, HC and PM emitted compared to other fossil fuels. This is not just of environmental importance; the cleaner fuel significantly lowers vehicle maintenance and running costs, with less contamination and residue build-up across engine components.

Natural gas vehicles could serve as a better economic alternative for large fleets of vehicles that drive many kilometres a day. Buses are well suited to Natural Gas fuelling. Because these vehicles are centrally maintained and fuelled, it is economical and beneficial to convert to Natural Gas.

NGVs around the Globe

According to the 2017 Natural Gas Vehicles (NGV) Global Report, there are over 24-million vehicles running on natural gas worldwide. In Africa, there were 192 078 vehicles running on natural gas in 2016, and during 2017 the number increased to 193 509 units.

Tanzania plans to shift to natural gas-powered buses on its rapid transit routes in Dar es Salaam, a move that is expected to cut fuel use by up to 50%.

“The entire project will see at least 800 buses switch to natural gas.” Tanzania Petroleum Development Corporation (TPDC) acting director-general, Mr. Kapuulya Musomba

More than 100 trunk buses with a capacity of 140 passengers will provide both normal (stopping at all stations) and express services (stopping only at connector stations).

According to the U.S Department of Energy, more than 160 000 vehicles in the United States run on Natural Gas.

“More than 35% of U.S. Public Transit Buses use alternative fuels or hybrid technology” American Public Transport Association

CNG has been the ideal choice for high mileage vehicles such as buses for many years now, however, South Africa has been in the back-end of the global revolution to find a cleaner, environmentally friendlier, and mostly, a more economical source of fuel in the public transport sector. CNG Holdings, through its division, NGV Gas PTY (Ltd), on realising the gap in the industry, has converted more than 1200 taxis and more than 300 fleet vehicles in Johannesburg to run on CNG. The converted buses are seeing between 20 to 40% reductions in fuel costs.

The conversion

Converting the Metro buses to run on CNG was not particularly challenging. In the case of Metrobus the diesel tanks were retained and the gas cylinders were placed on the roof under a moulded cover. The conversions were done by Mercedes at their factory and the CNG electronic control unit (ECU) was integrated into the bus operating system. The TRT buses in Pretoria are Dedicated Gas Buses and as such operate on 100% gas. Having dedicated gas engines means these buses save substantially in fuel costs. Diesel CNG buses such as those at Metrobus operate on a Diesel Dual Fuel System (DDF) whereby both gas and diesel are injected into the cylinder at an electronically controlled ratio to ensure the best performance while the dedicated gas buses at TRT use gas exclusively. Vehicle conversions kits, consisting of the cylinders, injectors, filling nozzles, regulator and ECU, are installed by SAGA-qualified and SAQCC-certificated NGV Gas engineers.