Today, people and companies are more aware and concerned about the environment than ever before. Everyone is looking for ways to reduce waste or convert organic waste into something more useful. The Federal Government has introduced a renewable energy policy and is continuing to fund for new waste conversion technology. It is now important for local governments to portray their cities and towns as green cities and they do not want all the waste to end up in landfills. Hence, there is more interest in waste conversion technologies than there was a few years ago.
Today, there are many waste conversion technologies and most of them hold tons of potential. These technologies are as follows:
These include an array of processes that either use or produce high amounts of heat when the municipal sold waste (MSW) is treated. Some of the technologies used are gasification, plasma, cracking, and pyrolysis. These technologies change the composition of organic MSW. Usually the process of conversion takes place inside a reaction vessel and may use oxygen. At times the inorganic portion of the MSW is treated with the organic part, but most of the time it is sorted out before the treatment.
Thermal waste conversion technologies are used to make products such as syngas, char, and organic liquids like light hydrocarbons.
Anaerobic or Aerobic Digestion
The solid organic waste is decomposed using microbes and this decomposition results in the formation of gases and liquids. Anaerobic digestion is usually employed in landfills, but can also occur in controlled reactors and digesters. During the process, microorganisms feed on organic matter without the presence of oxygen and produce gas and solid byproduct. Anaerobic digestion is used for sewage sludge, but it has been altered to decompose the organic portion of MSW. The biogas produced during the process is primarily used to generate electricity, but it has many other potential uses. If the biogas is cleaned of carbon dioxide, water and hydrogen sulfide, the resultant methane can be used to run heavy and light vehicles.
Aerobic digestion takes place in the presence of oxygen and can be wet or dry, just like anaerobic digestion. In dry aerobic digestion, the waste is first separated into organic and inorganic waste and then placed into an enclosed reactor for the microbes to feed on. This method of waste conversion has been around for many years. That is why wet aerobic digestion is considered a new and emerging waste conversion technology. In this process, the organic part of MSW is pulped, mixed, heated, and aerated. Thereafter, the microbes are introduced and they help to separate the waste into solid and liquid fertilizers.
In this process, the cellulose part of the waste (paper, yard waste, and food waste) is treated with acid (which works as a catalyst) and water while producing sugars. Usually, hydrolysis is one of the many steps in the waste conversion process. The sugars are then converted into ethanol and levulinic acid. The latter is used as chemical feedstock for other chemicals, such as succinic acid, diphenolic acid, and tetrahydrofuran.
In this waste conversion technology chemicals are used to convert MSW into usable products. It can involve pyrolysis, depolymerization, hydrolysis, or even gasification. Out of these, depolymerization is one of the newer technologies where large molecular compounds are permanently broken down into simple compounds. There are many steps involved in depolymerization, which is similar to refining petroleum and the organic waste is converted into steam, electricity, oil, and specialty chemicals. The process also produces carbon solids, which can be activated and used for soil amendment.
These are some of the waste conversion technologies that are being used to treat waste and make it into usable products. They are becoming the new forms of recycling !