Refuse Derived Fuel: RDF

Refuse Derived Fuel: RDF

Electric power is an essential energy that plays a significant role in human living and acts as a crucial factor in developing new technologies. As is widely known, Thailand has confronted the problem of waste accumulation for many years. This challenge is evident from the report by the Pollution Control Department discussing the issue of waste and pointing out the situation of household waste in 2021. The report indicated that there were 25 million tons of generated waste, of which only 7.89 million tons were recycled. Clearly, Thailand continuously suffers from accumulating waste, and a portion of this waste is disposed of improperly.

Therefore, promoting waste management through the 'Waste to Energy' method is crucial. This includes converting waste into fuel, also known as Refuse-Derived Fuel (RDF).

What is RDF?

Refuse Derived Fuel (RDF) is a type of solid fuel obtained by modifying municipal waste in both its chemical and physical composition. This includes processes such as decomposition, separating combustible waste from organic waste, metal fragments, non-combustible waste, and other types of waste. Other processes involve pelletizing, moisture reduction, etc., to produce quality-modified RDF. This fuel has certain properties, such as calorific value, size, moisture content, and density, that make it suitable for use as a fuel for electricity or heat production. It can also be co-combusted with coal to reduce the amount of coal used in the cement industry, for instance.

Types of Waste Used in RDF Production

The types or categories of waste that can be processed into RDF fall into two groups:

  1. Waste that is difficult to decompose and offers high heat output, such as plastic bags, small packaging boxes like milk cartons and snack boxes, paper scraps, foam, latex, animal skins, etc. This type of waste usually has a high calorific value, but improper incineration control often leads to pollution issues from the resulting combustion gases.
  2. Biomass waste, such as branches, bark, or fruit seeds. This type of waste usually has a low calorific value. However, if it is mixed properly with the first type of waste, it results in high-calorific-value fuel and can reduce the pollution issues caused by combustion gases when the fuel is used. The availability of this type of biomass waste varies and depends on the season.

Types of Refuse-Derived Fuel (RDF)

The types of RDF, based on the ASTM standard, which classifies fuel according to its characteristics and the process used for waste management, can be divided into 7 categories as follows:

  1. RDF-1: Involves the use of collected waste in its original state as fuel, without any transformation process, though large parts might be manually separated.
  2. RDF-2: Entails the sorting of collected waste to exclude non-combustible parts such as metals and glass. Then, the size is reduced through coarse grinding or cutting of the sorted waste.
  3. RDF-3: Similar to RDF-2 but further reduces the size until 95% of the sorted waste has a size smaller than 2 inches.
  4. RDF-4: Dust or powder-formed fuel derived from the combustible parts of waste which measures less than 0.0035 inches in size.
  5. RDF-5: Refers to fuel made from the combustible fraction of waste compressed into pellets with density greater than 600 kg/m3. Other components might be added to achieve the desired properties.
  6. RDF-6: The combustible portion of waste is processed into a liquefied or semi-liquid fuel.
  7. RDF-7: Involves transforming combustible waste into gas through gasification to produce synthesis gas (Syngas), which can be used as a fuel gas.

Utilization of Refuse Derived Fuel (RDF)

RDF is a versatile fuel that can be used in various ways, both for generating electricity and heat, such as:

  • Used on-site for waste-to-fuel conversion, combined with equipment that converts RDF into energy, like grate furnaces or fluidized bed incinerators.
  • Used off-site where transportation is needed, combined with equipment that converts RDF into energy, like grate furnaces or fluidized bed incinerators.
  • Co-combusted with other fuels such as coal or biomass to reduce the use of coal in certain industries.
  • Burned in cement kiln furnaces.
  • Used in conjunction with coal or biomass in the gasification process.