Thermal Processing

What are the aims of thermal processing?

• reduction of waste

• stabilising of waste

• recovery of energy

What are the types of thermal processing?

• incineration (combustion)

• gasification

• pyrolysis

What are the advantages and advantages of muncipal solid waste incineration in a modern energy-from-waste (Efw) plant?

Advantages:

• reduces waste to landfill

• financial incentive - landfill tax £80/tonne

• does not preclude materials recovery

• manages waste streams banned from landfill

• prevents methane emissions

Disadvantages:

• poor public perception can hamper implementation especia;;y concern over emssions

• high capital cost

• length timescales for public consultation, planning and permitting

• low efficiency but better if use heat

What are the advantages of advanced thermal technologies (gasification and pyrolysis) over conventional Efw incineration?

• Gasification converts MSW as a feedstock into valuable forms of energy through producing syngas

• Syngas can be turned into higher valuable commercial products e.g. transportation fuels, chemicals and fertiliser. Efw only = heat + electricity

• Gasification operates at higher temperature, completely breaking down larger molecules such as plastics

• Oxygen-deficient atmosphere so no risk of dioxin and furan formation

• Ash flows from gasifier in molten form, where it is quench-cooled, forming a glassy, non-leachable slag that can be used for making cement, roofing shingles, or used as an asphalt filler or for sandblasting

• Some gasifiers are designed to recover melted metals in a separate stream, taking advantage of the ability of gasification technology to enhance recycling.