chapter 8: Waste to energy – Bio gas and Landfill gas from Anaerobic digestion
Waste to energy – Bio gas and Landfill gas from Anaerobic digestion Mauritz Lindeque Researcher Built Environment CSIR
Background
Two of the main problems that the human race is faced with are, 1) waste disposal and 2) energy generation. Energy manifests itself in many forms. This is according to what we require in order to achieve the needs and comforts of life and the quantity of energy it takes to achieve these levels of comfort. With the advent of the industrial revolution the demand for energy has increased dramatically as well as the production of waste. It has become more apparent in the past few decades that the generation of energy from fossil fuels has contributed to the net volume of carbon dioxide (CO2) and other green house gasses (GHG) in the environment, which has detrimental effects on the environment and the general well being of the planet. Furthermore the disposal of organic waste on landfill sites has increased the emissions on GHG such as Methane (CH4). CH4 is seen as a gas that has a detrimental impact on the environment by a factor of 24 times more so than CO2 (NOAA 2008). Apart from the fact that CH4 is emitted from landfill sites (LFG) it also has the added pollution caused by leachates that seep in to the ground water from decomposing organic material on landfill sites (Surry County Council 2011). The South African Government is attempting to address these issues by concentrating on improved waste management plans and furthermore addressing the generation of renewable energies. These strategies such as the Waste Management Act No. 59 of 2008, the National Waste Management strategy 2010 as well as the Renewable Energy Feed In Tariff (REFIT) of 2009 amended 2011 are examples of the implemented changes.
Introduction
The generation of energy in whatever form that we require has allowed humans to settle in some of the most inhospitable places on the planet. The energy required to make our homes and workplaces comfortable include thermal energy as well as electrical energy. Electrical energy makes up 25% of the total energy consumed in South Africa (DME, 2000). Other sources of energy that contribute to the total energy production are from coal and liquid fuels. Coal fired power stations provide 93% of the total electricity generated in South Africa and globally will contribute to 44% of all electricity generated by 2030 (World Coal Association 2006). Coal is a fossil fuel that is seen as a major contributor to the net volume of CO2 and other GHG in the atmosphere. However it is important to sustain our industries and daily activities by using some type of fuel to generate the energy that we require. Moreover the planet cannot sustain the demand on the resources for ever. There will come a point in time where the demand for the resources will exceed the supply and availability of those resources. This is where a resource such as coal will reach a state of “peak coal”. With very insufficient data it is suggested that peak coal might be reached as soon as 2025 (Zittel & Schindler, 2007). It is clear, that if we, the inhabitants of the planet, are to maintain the life style that we have become accustomed to due to the availability of resources, this life style will be under threat not only from the supply of the resources but also the impact that man has on the environment. Even if the impact on the environment is not a high priority it is important that we find alternatives to the decreasing resources. With a global population estimated to reach more than 8.9 billion by the time that we could be reaching the peak of our coal reserves (UN 2004) (World Bank 2011) it therefore has to become a priority that alternatives to present energy resources are investigated the green building HANDBOOK
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