Waste-to-energy
Waste-to-energy (WtE) or energy-from-waste (EfW) refers to a series of processes designed to convert waste materials into usable forms of energy, typically electricity or heat.
The most common method of WtE is direct combustion of waste to produce heat, which can then be used to generate electricity via steam turbines.
Furthermore, anaerobic digestion, a biological process, converts organic waste into biogas (mainly methane and carbon dioxide) through microbial action.
The WtE process contributes to circular economy principles by transforming waste products into valuable resources, reducing dependency on fossil fuels, and mitigating greenhouse gas emissions.
However, challenges remain, particularly in ensuring that emissions from WtE plants, such as dioxins and furans, are properly managed to minimize environmental impact.
Advanced pollution control technologies are essential to address these concerns and ensure WtE remains a viable, environmentally sound solution.
WtE technologies present a significant opportunity to manage waste sustainably while contributing to global energy demands.
As technology advances, WtE may play an increasingly critical role in both reducing landfill use and enhancing energy security.
All new WtE plants in OECD countries incinerating waste (residual MSW, commercial, industrial or RDF) must meet strict emission standards, including those on nitrogen oxides (NOx), sulphur dioxide (SO2), heavy metals and dioxins.
Modern incinerators reduce the volume of the original waste by 95-96 percent, depending upon composition and degree of recovery of materials such as metals from the ash for recycling.
[12] According to the German Environmental Ministry, "because of stringent regulations, waste incineration plants are no longer significant in terms of emissions of dioxins, dust, and heavy metals".
[14] One process that is used to convert plastic into fuel is pyrolysis, the thermal decomposition of materials at high temperatures in an inert atmosphere.
Japan and China each built several plants based on direct smelting or on fluidized bed combustion of solid waste.
[citation needed] Fulcrum BioEnergy, which started in 2007 in Pleasanton, California, built a WtE plant near Reno, NV to convert waste to sustainable aviation fuel (SAF).
[21] The total exported product amounted to just 350 gallons of syncrude which were transported to Marathon Petroleum's refinery for conversion into jet fuel.
[20][22] The plant had issues including damage from unexpected generation of nitric acid and deposits of a concrete-like substance up to 10 feet thick in its gasification system.
[20][23] Waste-to-energy technology includes fermentation, which can take biomass and create ethanol, using waste cellulosic or organic material.
Such considerations are the main reason why several countries administrate WtE of the biomass part of waste as renewable energy.
[27] MSW to a large extent is of biological origin (biogenic), e.g. paper, cardboard, wood, cloth, food scraps.
Several research papers, including the one commissioned by the Renewable Energy Association in the UK, have been published that demonstrate how the carbon 14 result can be used to calculate the biomass calorific value.
The UK gas and electricity markets authority, Ofgem, released a statement in 2011 accepting the use of Carbon 14 as a way to determine the biomass energy content of waste feedstock under their administration of the Renewables Obligation.
No industrial liquid fuel producing gasification plants are currently operational, but two are under erection/commissioning in Varennes (CA) and Swindon (UK).
The US Air Force once tested a Transportable Plasma Waste to Energy System (TPWES) facility (PyroGenesis technology) at Hurlburt Field, Florida.
[44][45] Renergi will scale up their system of converting waste organic materials into liquid fuels using a thermal treatment process in Collie, Western Australia.
Renergi’s patented “grinding pyrolysis” process aims to converts organic materials into biochar, bio-gases and bio-oil by applying heat in an environment with limited oxygen.
As well as supplying electricity to the South West Interconnected System, 25 MW of the plant’s output has already been committed under a power purchase agreement.
