Classification of Waste-to-Energy (WtE) Processing Areas: Based on Waste Type, Technology, and Explosion Risk

What Is a Hazardous Area?

In industrial settings, a hazardous area is any location where flammable gases, vapors, or dust may accumulate in quantities that pose a risk of fire or explosion. These areas are classified using established standards:

• IEC/ATEX (Europe/International):

  • Gas: Zones 0 (continuous), 1 (occasional), 2 (rare)

  • Dust: Zones 20, 21, 22

• NEC (NFPA 70) (USA):

  • Class I: Gases/vapors

  • Class II: Dusts

  • Class III: Fibers

  • Each with Division 1 (likely presence) and Division 2 (less likely presence)

When is WTE considered Hazardous?

YES — WtE becomes hazardous when:

• To begin with, the feedstock contains flammable materials, VOCs, or hazardous waste, which significantly increase explosion risk.
• Furthermore, operators use gasification, pyrolysis, or incineration, which generate or handle combustible gases such as syngas or methane.
• In the same way, dust from solid fuels like RDF suspends in the air and increases the risk of dust explosions. Likewise, facilities store or process solvent-rich waste, which may release flammable vapors and create hazardous conditions.
• Additionally, poor gas control allows hydrogen or carbon monoxide to accumulate, thus forming an explosive atmosphere.

Common hazardous zones in WtE facilities include:

• Fuel feed systems
• Gas storage tanks
• Waste unloading pits
• Dust collection or handling systems
• Flare stacks or combustion chambers

NO — WtE may not be hazardous when:

• Firstly, operators handle only non-combustible MSW in fully enclosed and well-controlled systems.
• Moreover, proper ventilation, gas detection, and control systems remove the risk of explosive atmospheres.
• Finally, continuous monitoring confirms gas or dust levels remain below flammable limits at all times.

What Should You Do in Practice?

To ensure safety and compliance:

• Conduct a Hazardous Area Classification (HAC) study or a DSEAR/ATEX risk assessment.

• Refer to international standards and guidelines, such as:

  • IEC 60079-10-1 / 60079-10-2 (for gases and dusts)

  • NFPA 820 (specific to sludge and wastewater handling)

  • API RP 500 / 505 (hazardous classification in petroleum and chemical industries)

Summary