Waste to Energy Technologies – The Benefits and Challenges
Waste to energy technologies are processes designed to convert waste materials to useable energy in the form of electricity, heat, or both. The energy is generated in most cases directly from combustion or through the production of combustible fuels, including synthetic fuels, methanol and ethanol. Incineration, which involves the combustion or organic materials, is the most common waste to energy technology. However, alternative technologies such as pyrolysis, gasification and anaerobic digestion, have also been successfully implemented. Following is a brief rundown of the benefits and challenges of each of these waste to energy technologies.
In most cases, generating energy from waste via incineration is done by burning waste to boil water, creating high-pressure steam to turn generators and create electricity.
Modern incinerators can slash waste volume by more than 95 percent, dramatically reducing the amount of land needed for landfills.
Incineration plants can be expensive, both to purchase and to operate.
Incinerators produce smoke and ash that may contain dangerous compounds, including nitrous oxide, dioxin, and heavy metals. While modern technology eliminates much of these of pollutants, some may still be released into the atmosphere.
Pyrolysis produces energy from waste through an oxygen-controlled, thermo-chemical process. This results in a combustion-free decomposition of all organic materials.
Pyrolytic systems have a wide variety of uses, including using residue from plastic materials, electronic scrap and unsorted waste for energy production as well as the creation of oils & solvents, certain gases, charcoal and electricity.
Pyrolysis reduces the emission of greenhouse gases.
Potentially hazardous emissions, which are problematic with incineration, are virtually eliminated with pyrolysis.
Pyrolysis is a complex process that can be expensive to implement and maintain.
A still-emerging technology, pyrolysis has yet to maximize its commercial potential.
Gasification is a technology used to convert organic or fossil fuel-based materials into hydrogen, carbon dioxide and carbon monoxide. These materials are processed using high temperatures through the controlled use of oxygen, steam or both; combustion does not occur in gasification. The primary application of gasification is in the production of syngas, which can be used as fuel and in the production of consumer products, fertilizers, transportation fuels, power, chemicals, and many other applications.
A large variety of feedstock can be gasified, including sewage sludge, plastics, wood, agricultural and industrial waste, and plastics.
Gasification plants produce mush lower amounts of air pollutants than incinerators.
It’s significantly more expensive to operate a gasification plant than an incinerator; however, proponents of gasification believe that advancement in technology will narrow the cost gap between the two waste-to-energy processes.
Anaerobic digestion is a process that breaks down biodegradable material without the use of oxygen. A chief byproduct of anaerobic digestion is biogas (methane). Through combustion, biogas can produce electricity and heat.
Anaerobic digestion reduces the emission of greenhouse gases to the atmosphere.
It produces renewable energy that can directly replace fossil fuels.
The process of anaerobic digestion can produce unpleasant odors if the plant is not managed properly.
Not all waste materials can be effectively treated using anaerobic digestion. The process is restricted to organic materials.