Some of the major technologies and services are described in more detail below.
Fluidized–bed combustion system (incineration)
Originally patented in 1879 for an ore
– roasting furnace, fluidized–bed technology has since evolved and is now
used extensively in a wide variety of industries, including hazardous waste treatment. Energy-recovery systems, in the
form of a steam generator or air pre–heater, are often added when this is justified financially.
The technique uses a heated bed of sand–like material which is suspended or fluidized (hence the name) within a rising column of air. Fuels sources – such as agricultural waste, municipal solid waste, wood wastes, industrial and municipal sludges, plastic, tires and coal – are added to the process where the scrubbing action of the bed material enhances the combustion process by stripping away the carbon dioxide and char layers that normally form around the fuel particles. This allows oxygen to reach the combustible material much more readily and increases the rate and efficiency of the combustion process.
Fluidized–bed incineration is extensively used in the treatment of certain types of hazardous wastes although there are physical limitations regarding the size and dimensions of solid wastes. Air emissions are controlled using standard gas clean–up systems employed by other thermal treatment systems. The solid residue is sampled and analyzed for suitability for disposal and can be reprocessed or treated by a secondary technology until the disposal requirements are met.
Bio–digesters
Bio–digesters are systems that
process organic waste through anaerobic digestion. Anaerobic digestion refers to the
natural decomposition of waste in the absence of oxygen. Important by–product of this process are purification
of water and the production of biogas which can be used to power electricity generators, provide heat and produce soil
improving material.
Recovering biogas for energy generation helps reduce the harm caused by greenhouse gas emissions which are often simply released into the atmosphere. Bio–digesters are very successful in this respect as they turn organic solid waste liabilities into value–added products and income, helping to reduce pollution levels and combat global climate changes by recycling methane in an entirely closed system.
Almost any organic material can be processed in this manner. This includes biodegradable waste materials such as waste paper, grass clippings, leftover food, sewage and animal waste. Anaerobic digesters can also be fed with specially grown energy crops to boost biodegradable content and hence increase biogas production.
Bio–digesters are used in large scale industrial processes as well as in smaller scale domestic residences. Examples of these include sewer and grey water disinfectant systems that filter the household water to acceptable agricultural standards. In housing projects it is neither expensive nor difficult to polish the water further to drinking standards.
Micro hydropower
Large scale hydroelectric power has
been used worldwide for a long time to generate huge amounts of power from water
stored behind massive dams. Small scale hydropower has been used for hundreds of years for manufacturing, including
milling grain, sawing logs and manufacturing cloth. The difference is that it can be used without a dam to generate
electricity for home scale remote power systems.
Commercial micro hydro generators use a small turbines connected to an electrical generator or alternator. Water is collected in an intake pipe upstream, travels down to the turbine in plastic pipe, and is forced through one or more nozzles by its own gravity pressure. Power is generated by a generator or alternator directly connected to the turbine wheel.
No dam is needed although a drop of 3 feet of or more and at least 20 gallons per minute of flow are necessary. As the height of the drop increases, the gallons of water needed are decreased. The amount of potential power created increases the higher the drop and the stronger the flow.
Energy efficiency – going green
Sustainable, environmentally friendly
processes and facilities do not necessarily have to entail massive scientific
innovations or the budget of a major developer. Small, smart amendments to the materials and methods currently used in
commercial and domestic residences and developments can provide surprisingly impressive results.
Take for instance the example of the development in Kuyasa in Khayelitsha, Cape Town. This small project is recognised by the United Nations as a gold standard clean development mechanism project. It involved retrofitting eight low –cost houses and two crèches with simple energy–saving devices such as insulated ceilings, low–watt bulbs and solar water heaters.
This has saved some 2.85 tons of carbon dioxide (CO2) per building every year. This may not sound so impressive at first glance however the reality is that developed countries are prepared to pay lots of money for CO2 reductions and considering that the trade of Certified Emissions Reductions is dependent on the US dollar exchange rate, South African developers stand to make a substantial profit.
