Energy

ENERGY FROM WASTE

Recovered paper cups have a significant energy value with one tonne of paper producing (approximately) as much energy as four or five barrels of oil!

Many countries are advocating the use of 'biomass' (typically wood) as a short loop/low carbon source of energy and we feel that it is even more environmentally responsible if that wood has been previously used, possibly as a paper cup. Adding to the environmental benefit, would be to then recycle the used paper cup into a useful product such as toilet paper, household kitchen towels, cereal boxes or packaging. Once these products have reached the end of their useful life, they can be processed to generate electricity or heat rather than being tossed out into the landfill.

Waste-to-Energy (WTE) or Energy-From-Waste (EFW) is the process of creating energy in the form of electricity or heat from the incineration of the waste source. This process reduces or eliminates waste that otherwise would be collected and retained at a landfill site. Most waste-to-energy plants produce electricity directly through combustion, or produce a combustible fuel commodity such as methane, methanol, ethanol or synthetic fuels.

In November 2008, the UK Institute of Mechanical Engineers (IMechE) published an informative report on Energy from Waste (for a pdf copy click here). The report outlines a number of different systems that can be used to convert solid waste to energy. Each system employs a different technology and process to use the solid waste, but they can be broadly divided into two major categories - thermal and non-thermal treatments. A brief description is provided below on the more common thermal and non-thermal processess used for energy prodcution from waste. This is not a complete list, but a simple introduction to some of the commonly encountered technologies.

GEM Converter

Thermal Treatment: Gasification - this involves the use of high current electricity passed between two different electrodes creating an electrical arc that canreach 1,100 C. this high temperature breaks down waste in the absence of oxygen into synthetic gas and other by-products such as slag, carbon dioxide, sulphur, water and salts. The synthetic gas is used to genertate electricity. Heat energy can also be captured as part of the process.

WTE InEnTec

Thermal Treatment: Incineration - this process involves the combustion ofwaste at high temperatures generating heat, bottom ash, flue gases and particulatels. The heat produced in this process is used to generate electrical power. Heat energy can also be captured. Incineration is the most common means of using paper cups in the WTE process.

Thermal Treatment: Pyrolysis - this process uses the chemical decomposition of organic materials through the use of heat in the absence of oxygen to generate a synthetic gas.

Anaerobic Digestion - This process uses micro-organisms to breakdown organic material in the absence of oxygen to generate a biogas (methane) that can be used to generate electricity. the residual solids of this process can be used as fertilizer.

Mechanical Biological Treatment - is a form of waste treatment facility that combines a sorting facility to recover metals, plastics and glass with a bioogical treatment such as compositing, anaerobic digestion or bio-drying.

In the ideal circumstance, where regulations and facilities permit, the used paper cup should be recycled into a usable product such as tissue and towelling. In circumstances where no other option is viable or available, we recommend that used paper cups be incorporated into a waste stream intended for use in an energy from waste plant and the energy value realised.