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Cogeneration is the simultaneous production of electricity and heat using a single primary fuel. Biomass cogeneration uses waste wood and horticultural materials as fuel. These are plants that derived their growth and energy from the sun, converting carbon dioxide into oxygen. This biomass green energy reduces use of fossil fuels. The electricity and steam generated are used to leverage in recycling and energy related business activities. Cogeneration results in higher thermal efficiencies as it uses heat that would otherwise be wasted. At the same time, carbon dioxide emissions are also reduced. |
What is the difference in using fossil fuel and biomass as a fuel?
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Fossil fuels are hydrocarbons and are not renewable. Fossil fuels when combusted is converted into energy and gasses such as carbon dioxide. Carbon dioxide is a green house gas that traps heat and a contributor to global warming and climate change. Biomass is a renewable fuel and is carbon neutral. In their life cycle, plants covert carbon dioxide into oxygen. Biomass can be used as an alternative energy source to fossil fuels in generating energy. |
How long has ecoWise biomass cogeneration plant been operating?
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The plant has been operating since April 2005. Apart from the energy generated and the tipping fee revenues, the plant has also created new employment and upgrading opportunities for its staff. |
What other advantages does the biomass plant bring?
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In the past, biomass waste would have been sent to the incineration plants and burnt resulting in lost energy. Now such biomass can now be turned into useful energy. The cost of disposal at waste to energy plants is also lower, benefiting waste service providers. |
What are the key features of the plant?
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The plant has a net steam output of 15 tonnes per hour and superheated steam enters the turbine at 260 degrees Centigrade at a pressure of 22 bar. Its biomass fuel consumption is up to 5 tonnes per hour. A moving floor silo with an unloading system conveyors the crushed biomass to the boiler. The boiler is designed with a water cooled stepgrate. Particulates are captured in a mullticyclone dust collector and removed through an automatic fly ash evacuation system. Control is provided using a programmable logic control system such that the plant operates with minimum manpower and supervision. Operational performance is captured and stored electronically. A steam turbine with turbo generator generates the electricity. |
What type of biomass fuels are used?
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The plant uses a mixture of horticulture and wood wastes. These are sent to the plant where they are sorted, shredded and fed into the fuel feeding system. The biomass needs to be prepared in the correct sizes for conveyance and proper combustion. |
How much energy can be expected from using such biomass?
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The biomass varies in its energy values. Typically, base on a maximum moisture content, on wet base of 45%, the caloric value can range from 1900 kcal/kg to 3000 kcal/kg. |
What factors affect the plant design and performance?
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| • | thermal energy (MWt) required | |
| • | electric power (MWe) required | |
| • | fuel mix available ie calorific values of biomass fuels | |
| • | pollutant emission standards | |
| • | type of turbine selected | |
| • | stack temperature | |
Other factors include the electrical and the mechanical efficiency of the system and the electrical generator efficiency.
How is the plant controlled?
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The plant has a programmable logic control system that uses sensors throughout the plant. These will monitor parameters such as fuel intake, combustion process, steam characteristics, flue gases etc and adjustments are made automatically to obtain the required output energy. The plant can run for long periods on automatic mode but the operators are able to change such settings to suit fuel and energy consumption conditions. |
How is the ash and flue gases handled or monitored?
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Fly ash is removed using a mullticyclone dust collector with an automatic fly ash evacuation system. Flue gases are continuous monitored as they exit through the chimney. Such electronic records are submitted regularly to the environmental authority. |
How does having a biomass cogeneration plant impact ecoWise?
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The biomass plant provides green power to run industrial operations thereby reducing costs. Apart from making our own electricity, the excess steam is used to provide heating and drying services for ISO containers and spent grains. This generates more revenues streams from different sources of materials. The use of biomass as fuel and to provide heating services reduces use of non renewable fossil fuel while generating revenue. With biomass as a carbon neutral fuel, the company’s carbon footprint is also reduced. The provision of such services and the setting of such facilities has also increased our technical strengths in projects assessment, design and engineering, operations and maintenance. |
Can such a biomass plant be replicated elsewhere?
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The biomass plant can be replicated and upscaled to larger generating capacities even with different fuels and in different operating environments. Having such an operating biomass plant with over four years operating experience means that ecoWise can also add value by providing ‘on the job’ training to operators in its investments. Such integration between energy production and uses is gained through experiences of owing and operating industrial plants. |
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