Your household garbage may soon help electrify your suburb, fuel your car or do both.
South African technology, already demonstrated in Australia and China, is being used to generate liquid fuel from coal and gas but can also be used to make fuel from biomass, including municipal waste. In addition, electricity can be generated as a by-product of the process.
Advances in the development of synthetic fuel by the University of the Witwatersrand’s Centre of Materials and Process Synthesis (Comps) mean that smaller modular plants, which can produce both fuel and electricity, can do so while releasing 30% less CO2.
Comps has already helped develop a coal-to-liquid (CTL) fuel demonstration plant in China, in conjunction with Clean Coal Technology (CCT), a firm based in South Africa.
In conjunction with Australia-based Linc Energy, Comps has also assisted in the development of the first underground coal gasification demonstration plant in Chinchilla, Australia.
The Comps team, headed by professors Diane Hildebrandt and David Glasser, wants to develop a biomass-to-liquid demonstration plant to be built in South Africa. Once an investment decision is made, a biomass plant could be up and running in three years.
According to Hildebrandt, data gathered through the Chinese demonstration plant, which is based near Baoji in the province of Shaanxi, show that the establishment of a commercial plant is now feasible.
Depending on how fast CCT can design a commercial plant, construct and commission it, and depending on the fuel used, this could take four to five years to complete, she says.
Grappling with fuel and electricity supply
South Africa is grappling with the issue of both fuel security and electricity supply. It is debating the merits of PetroSA’s proposed giant oil refinery, Mthombo, as well as the potential costs of upgrading older established refineries jointly owned by private sector players such as BP and Shell.
The production of synthetic fuel from coal and gas is not a new idea. Synfuel production is currently embodied in the mammoth multibillion-rand infrastructure of global giant Sasol.
But the trick has always been to create synthetic fuel in ways that are less costly, more energy efficient and produce fewer greenhouse emissions.
The creation of fuel from biomass through a further application of the technology means municipal garbage dumps and landfills could become energy stores instead of expensive problems for future generations.
The process, put simply, works as follows: coal is converted into gas, mainly carbon monoxide and hydrogen, through what is known as gasification. This gas is then converted into liquid fuel through the Fischer-Tropsch process, named after German scientists Franz Fischer and Hans Tropsch, who invented it in the 1920s.
The Fischer-Tropsch process is exothermic and the heat released from this reaction can produce steam, which, in turn, can be used to produce electricity. Other gases or “off-gases” generated can also be used to produce electricity.
Similarly, gas to liquids (GTL) converts natural gas to liquids and biomass to liquids (BTL) sees the gasification of waste, and the resultant gases are then converted to fuel.
Appropriate tech for developing countries
This technology is particularly appropriate for developing countries, says Hildebrandt, where security of fuel supply is often uncertain and electricity shortages are common.
“This is a unique opportunity for South Africa, where many local authorities are not working efficiently and municipal waste management is becoming a cost,” she says.
The plant’s output could also be adjusted to cater for different demand, she says. For example, at peak electricity-demand times it can be geared towards producing more power and, when electricity demand slackens off, it can shift to fuel production.
Depending on the resources available, the desired capacity and potential financing, Comps wants to set up a facility in South Africa that is able to produce 4MW of electricity and 100 barrels of fuel per day, using 100 tonnes a day of dry municipal waste.
This could cost about R150-million, while the estimated cost of a CTL plant using this technology, and producing about 1Â 000 barrels per day of fuel, would cost about R665-million.
By contrast, Sasol’s Mafutha project, which has since been placed on the backburner, would have produced about 80Â 000 barrels per day. Although the cost of the Mafutha project is not clear, one figure bandied about has been roughly R160-billion.
Glasser argues that these costs are estimates and depend on the size of the plant and available resources.
“What we do is different to Sasol,” says Hildebrandt, who compares the team’s work in the language of computers. “Sasol are like the companies who operate large mainframes,” she says, “while what we do [is akin to making] laptops.”
Plant design should be more efficient
Ostensibly, the plants should be faster to design, more efficient, have a lower capital cost and produce a wider range of products, namely fuel and electricity.
Although many synfuel companies globally are looking at building mega-production facilities, this could be seen as a paradigm shift towards smaller plants. They come with the added advantage that they may be located closer to the fuel source and, although the process is not carbon free, less money is spent on technologies such as carbon capture and storage.
Some of the intellectual property resides with CCT, such as the data generated from the demonstration plant.
“All other intellectual property resides within Wits, which allows us to design and build CTL, GTL and biomass-to-liquids plants where there is a market,” says Hildebrandt.
“In addition, new concepts and ideas that have emerged after the building of the demonstration plant form a new generation of intellectual property that gives us a competitive advantage.”