Waste and Energy Production

Waste-to-energy (WtE) is the process of generating energy in the form of electricity and/or heat from the primary treatment of waste. Energy recovery from waste is the conversion of non-recyclable waste materials into usable heat, electricity, or fuel through multiple processes, including combustion, gasification, pyrolisation, anaerobic digestion and landfill gas recovery.

Energy from waste offers recovery of energy by conversion of non-recyclable materials through various processes including thermal and non-thermal technologies. Energy that is produced in the form of electricity, heat or fuel using combustion, pyrolisation, gasification or anaerobic digestion is clean and renewable, with reduced carbon emissions and minimal environmental impact compared with other forms of energy.

Thermal technologies: Waste treatments that are conducted involving high temperatures.

• Incineration is the most common and popular method for WtE generation. Incineration is also a very highly contested technology, due to concerns it raises regarding safety and environmental impact. In simple terms it refers to a type of waste treatment process, where the organics from the waste collected are burned at high temperatures. The heat generated from this thermal temperature is then used to create energy. Several European countries are experimenting with incineration as an alternate means of energy production, including Sweden, Germany, Luxembourg and Ireland.
  
  Commercial incineration of municipal waste in Ireland commenced in late 2011 at Indaver Ireland’s Carranstown, Co. Meath site. The EPA also granted waste licences for commercial incinerators to Indaver Ireland (Ringaskiddy, Co. Cork) and Dublin City Council (Poolbeg). The Poolbeg incinerator is operating at full capacity and processing approximately 1,800 tonnes of solid waste per day. Construction has not commenced at the Ringaskiddy facility to date (December, 2020) after local objections. Although these kinds of installation appear a ready solution to the waste problem, they often attract opposition because of health and safety fears.
   
• Depolymerisation uses thermal decomposition where in the presence of water, the organic compounds are heated at high temperatures.
   
• Gasification converts carbonaceous substances into CO₂, carbon monoxide and hydrogen. This process, like incineration, employs high temperatures to obtain results. However, the major difference is that combustion does not occur during this process. Steam and/or oxygen is also used in the process instead of fossil fuels or organic substances.
   
• Pyrolysis is another waste to energy process, used majorly in industrial processes. Pyrolysis employs agricultural waste or organic waste from industries to produce energy.
   
• Plasma arc classification uses plasma technologies to obtain syngas or synthesis gas. A plasma torch is used to ionise gas and subsequently obtain synthesis gas. The process generates electricity while compressing waste.

Non-thermal technologies: Waste treatments that are not dependent on high temperatures.

• Anaerobic digestion is a slow process, where micro organisms are used to remove biodegradable content. No oxygen is present during the process. It is used both domestically and commercially to avail of the release of energy during the process and use it. Anaerobic technologies are seen as good agents to reduce greenhouse gases from the atmosphere and also as a means of fossil fuel replacement.