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Waste-to-energy – the best of both worlds for African cities

With Turboden’s Organic Rankine Cycle (ORC) waste-to-energy (WtE) technology, available locally from Energas Technologies, southern African countries can efficiently produce electric and thermal power from waste, thus dealing with their mounting landfill problems and reducing environmental and health risks, all while generating sustainable energy.

With most cities and towns running out of landfill sites, waste management has become an imperative. WtE technology provides a workable solution, not only to deal with waste management issues, but also to help generate the much-needed energy for power-constrained regions such as southern Africa.

Globally, human activities generate about 1,3-million tonnes of waste daily. According to the World Bank, waste generated globally will increase by 70% to about 3,4-billion tonnes by 2050. At the same time, waste generation in sub-Saharan Africa is expected to more than triple. 

As cities account for 75% of energy generated globally and simultaneously produce 80% of carbon (CO2) emissions, it makes sense to reduce their emission levels from landfills by using them to generate energy. With WtE technology, Municipal Solid Waste (MSW) can now be regarded as a resource, rather than a problem.  

“With Turboden’s ORC waste-to-energy solution, both old and existing landfill sites can be mined, and the waste can be used for power generation,” says Laetitia Jansen van Vuuren, product manager at Energas. “This is an interesting proposition for many cities in southern Africa where landfill sites are fast reaching their maximum capacity and are occupying valuable land that could be made available for other, more financially and socially beneficial purposes.”

With over 40 years of experience, a global presence, over 750 MWe installations, and more than 400 plants in 50 countries, Turboden is a market leader in the proprietary design and manufacturing of ORC optimised turbines.

Designed according to specific client requirements, the ORC-based WtE plant can produce electric power only with an electrical efficiency of up to 30% or Combined Heat & Power (CHP). Depending on specific characteristics of the waste, various waste combustion technologies and heat recovery exchangers may be employed.

The ORC turbogenerator makes use of a closed thermodynamic cycle to convert heat into electricity. The thermal power recovered from waste combustion vaporises a suitable organic working fluid, which then expands through the turbine and produces clean and reliable electric power through the alternator. Thanks to the regenerator, internal heat recovery takes place, thus improving the cycle efficiency.

Downstream from the regenerator, the organic vapour is condensed and pumped back to start the cycle again. The heat from condensation can either be used by the heat users or dissipated. The heat from waste combustion is transferred to the ORC working fluid by means of an intermediate circuit or directly via the combustion gases in direct exchange systems. The media used in the intermediate circuits are thermal oil, saturated steam or superheated water.

A key advantage of Turboden’s WtE concept is its ability to mix different fuels such as MSW, chicken manure, biomass, waste and/or waste heat from industrial production processes, heat recovery from gas turbines and engines, natural gas and water sludge.

“With Turboden’s closed circuit ORC technology, no water is required in the process. This is especially beneficial for water-stressed regions such as southern Africa,” concludes Jansen van Vuuren.