Waste Treatment and Recycling: Methods and Technologies
Methods of Treatment
Incineration
It’s a garbage collection method that involves combustion of waste at high temperatures. Incineration and other treatment systems at high temperatures are described as heat treatment. Thus, the incineration of waste materials becomes waste heat, gaseous emissions and residual solid ash. Other types of heat treatment include gasification and pyrolysis. Incineration is applied fairly in countries like Japan where land is a scarce resource. Sweden has been a leader in using energy generated by burning since 1985. Denmark also makes extensive use of incineration, producing heat and electricity used for heating.
Zero Waste Technology
This consists of the construction, commissioning and management or audit of a Processing Plant for final disposal of Municipal Solid Waste (MSW). Municipal Solid Waste is used as inputs in a production process, in this case, building materials, paving, infrastructure, etc. MSW at the plant is preselected according to its composition. On one side, materials like metals, aluminum, glass, paper, cardboard, and plastics are separated for recycling. On the other hand, the remaining MSW capable of being transformed into construction materials (organic debris, wood, rubber, etc.) is processed through solidification and stabilization.
Solidification and Stabilization of Waste
This is achieved by applying a system called microcapsules. The latter consists of mixing, kneading, molding and shaping the non-recyclable MSW with a binder which acts as a confinement through a proper process. The product thus obtained is called “Compound”. This compound has better characteristics than its peers to obtain “building materials” and at a significantly lower cost.
Composting and Anaerobic Digestion
Waste materials that are organic in nature like plants, debris and products’ derivatives are increasingly being recycled. These materials are put in a compost and/or digestion system to control the biological process of decomposition of organic matter and kill pathogens. The resulting organic material is then recycled as straw or compost for agriculture.
There are a variety of methods of composting and digestion technologies, ranging from simple compost to automated digestion crushed in a trash container. These methods of biological decomposition are distinguished as aerobic composting methods or anaerobic digestion methods, although there are hybrids that use both methods.
In Anaerobic Digestion
Compost is not the only product; the main ones are carbon dioxide and methane. These gases, when released into the atmosphere, are known to be producers of greenhouse gases that affect ozone.
Treatment Biological Mechanisms
Pyrolysis and Gasification
These are forms of heat treatment in which waste is heated to high temperatures with limited oxygen. The process takes place in a sealed container at high pressure. Converting material to energy is more efficient than direct incineration because it generates energy that can be recovered and used, much more than simple combustion.
Pyrolysis of solid waste converts the material into solids, liquids, and gases. The liquid oil and gas may be burned for energy or converted into other products. The solid residue can be transformed into other products such as activated charcoal.
Gasification is used to convert organic materials directly into a synthetic gas composed of carbon monoxide and hydrogen. The gas can be burned directly to produce steam or used in a motor to produce electricity. Gasification is used in biomass power stations to produce renewable energy and heat.
Utilization of Sewage Sludge in Agriculture
The European Union regulates the utilization of sewage sludge in agriculture in order to prevent harmful effects on soils, vegetation, animals and humans. In particular, it sets limits on concentrations of certain substances in sludge, prohibits the use of them in some cases and regulates sewage treatment. The sludge has valuable agronomic properties in the area of agriculture. The use of sewage sludge must take into account the needs of plant nutrients but should not impair soil quality and agricultural production. In fact, some heavy metals in sludge can be toxic to plants and humans. The directive defines it as follows:
Sludge, treated side, agriculture and use Member States must prohibit the use of sludge when the concentration of one or more heavy metals in the soil exceeds the limit values laid down in accordance with Annex 1 A.
- On pasture or crops to feed itself. It is to be grazed or harvested for feed crops on the land before the expiration of a given time (in no case less than three weeks)
- Vegetable and fruit crops during the growing period with the exception of fruit trees.
- On soil in fruit and vegetable crops which are normally in direct contact with the soil and normally eaten in raw state for a period of ten months before harvest and during the harvest itself.
Member States must establish each year, for the first time five years after notification of this Directive, a summary report on the use of agriculture sludge, in particular the quantities of sludge used, the criteria followed and any difficulties encountered, and proceeds to the Commission to publish the information contained therein.