Background information
Waste-to-Energy (WTE) or Energy-from-Waste (EfW) is the process of generating energy in the form of electricity and/or heat from the primary treatment of waste. Most WTE processes produce electricity and/or heat directly through combustion or produce a combustible fuel commodity, such as methane, methanol, ethanol or other synthetic fuels. Sources of waste feedstock include bio-sludge, industrial waste, Municipal Solid Waste (MSW), medical waste, and agricultural waste. WTE plants offer a sustainable source of renewable energy with significant positive environmental and economic impacts, including the elimination of landfilling and the reduction of Green House Gas (GHG)Emissions. WTE plants fall into two main categories: thermal treatment and biological processing of organic waste. These processes use a range of technologies including gasification, plasma-arc gasification, pyrolysis, anaerobic digestion, and combustion (incineration). The type of technology utilised in any project is dependent on the characteristics of the feedstock waste material. Similarly, the outputs and residues from WTE processes also vary, depending on the nature of the feedstock and the technology used
Technology
There are three (3) main types of thermal conversion Waste-to-Energy (WTE) technologies; Gasification (including Plasma-arc Gasification), Combustion (incineration), and Pyrolysis (including High-Temperature Pyrolysis).
Combustion
Combustion (Incineration) Combustion (incineration) of waste is achieved by heating waste in an excess of oxygen. ‘Mass burn’ refers to a process that accepts raw or post recycling municipal solid waste (MSW) without any additional pre-treatment (e.g., no shredding or refuse derived fuel (RDF) production). The process can best be explained by examination of the combustion of waste in grate furnaces, where the fuel forms a bed on top of the grate and the combustion air is injected through the grate. The different local temperatures and oxygen concentrations cause a succession of reactions from drying through pyrolysis and gasification to final combustion.
Combustion is a sequence of close-coupled physical and chemical reactions; initially the waste dries, then reactions occur as volatile compounds are heated and de-volatilise from the solid phase into the gaseous phase and are then combusted. As this process occurs an ash comprised mainly of inorganic components is left behind. Combustion usually takes place with an excess of air (which is provided from below the grate as under fire air and via secondary and tertiary injection as overfire air), in order to ensure the proportion of fuel reacting with the oxygen is maximised.
Combustion of MSW is a very well-established technology with many hundreds of operational plants worldwide. Energy recovery is invariably in the form of a steam boiler which recovers heat from the hot flue gases to generate superheated steam. A steam turbine is used to generate electricity, except in cases where the steam can be used directly in a co-located industrial process for district heating or desalination. The net electrical efficiency of a WTE combustion plant generally varies from 15 – 25% depending on the size of the plant and steam conditions. Efficiencies are relatively low compared to fossil fuel plant because of the lower calorific value of the fuel and limitations on steam temperatures to avoid excessive corrosion caused by acid gases and other compounds produced by the combustion of MSW. However, efficiencies of up to 30% (electricity only) are achievable using more advanced energy recovery techniques, and there are also a couple of examples of WTE combustion plants which are 26 integrated with Combined Cycle Gas Turbine plants to boost the electrical efficiency considerably. However, technical challenges and economics often limit the efficiency in practice, and such advanced techniques are normally only possible where financial support is available (such as a premium on the electricity price from WTE or other government subsidies). In order to exceed an overall efficiency of 30% without the input of an external heat source, plants generally need to export heat as well as, or instead of, electricity.
Thermal efficiencies above 30% are possible in combined heat & power configurations, where a proportion of the heat which is rejected to atmosphere in plants that produce only electricity is recovered for process use. The highest levels of energy recovery are achieved in heat-only configurations where thermal efficiencies can exceed 80%. Mass burn combustion only converts the organic content of the MSW to energy and leaves behind the inert content which is called ash comprised of inorganic material mixed with post combustion residues of ferrous/non-ferrous metals. The amount of ash varies with the demographics of the communities being served by the facility and the extent of recycling that is undertaken. However, typical thermal processing facilities produce ash in the range of 20% to 30% by weight of the total waste feed. However, since ash is relatively dense, on a volume basis, the waste is reduced in volume by about 90%. Depending on the regulatory framework and treatment process, ash from the combustion grate (bottom ash) can be treated and reused as construction material after further treatment, such as weathering (carbonation) or melting via plasma or slagging processes. Ash collected from the flue gases (including ash particulates arising from the boiler and air pollution control residues from bag filters) will contain hazardous compounds and generally requires pre-treatment, stabilisation and careful disposal in fully engineered landfills.
The hot flue gases produced in the combustion furnace pass into a water tube boiler where the energy is recovered via heat transfer to form superheated steam inside the tubes. The gases then pass through the Air Pollution Control (APC) system to be cleaned where pollutants such as acid gases, oxides of nitrogen (Nox), heavy metals and dioxins/furans are removed before the cooled flue gas is emitted to atmosphere via a chimney. The superheated steam is used within a steam turbine to generate electrical power. Two types of solid residues are generated by the combustion process; Incinerator Bottom Ash (IBA) and Air Pollution Control (APC) residues incorporating fly ash from the abatement equipment.
Benefits of WTE
Waste-to-Energy has multiple benefits compared to MSW landfill
– Reduces landfill waste.
Waste is reduced in volume by about 90% by combustion, so significantly less landfill space is needed.
– Creates a Significant Amount of Energy.
27.5MW is enough to power more than 86.400 households in Egypt for a year. With an average of 3.59 people per household, the WTE plant in Abu Rawash will generate enough energy for more than 310.000 people for a year!
– Recycles Excess Waste.
Before the waste is incinerated, metals (e.g. steel and aluminium) are removed from the MSW. These metals are recycled, which further shrinks the amount of unusable waste.
– Sustainable process.
By applying traditional emission control equipment such as Selective NonCatalytic Reduction (SNCR) Semi-wet + Dry + Powdered Activated Carbon (PAC) injection + Baghouse Filter, harmful gasses are prevented be released into the environment.
- Consortium partners
Green Tech Egypt (GTE) – Project Owner (Renergy LLC) Green Tech Egypt LLC (GTE) was established in 2017 and focuses on renewable, sustainable, and innovative solutions to improve Egypt’s environmental and energy sector using the latest European technology and to follow European Environmental Standards.
Green Tech Egypt (GTE) – Project owner (Renergy LLC) GTE is passionate about Egypt and the environment, so Green Tech Egypt LLC (GTE) was established in 2017. GTE focuses on renewable, sustainable, and innovative solutions to improve Egypt’s environmental and energy sector and uses the latest European technology and align with European Environmental Standards. Due to the increase in waste and rising energy demand, GTE is working on Egypt’s first Waste-to-Energy (WTE) plant. Moreover, GTE works on waste sorting/ processing, sustainable energy, aquaculture development and construction residue related projects. GTE is committed to giving the best satisfying solutions for environmental issues with Egyptian society’s benefit to preserve historical and natural beauty.
OAK Group Holdings (OAK) – Project Owner (Renergy LLC) OAK Group Holdings (OAK) is an international conglomerate of specialist services companies delivering pioneering renewable energy and infrastructure solutions to both the Public and Private sectors. Headquartered in the Kingdom of Bahrain with other global offices, OAK is a technology driven owner, developer and investor with particular focus on stepchange technologies delivering innovative solutions for enhanced business performance and productivity for its clients. As a group, OAK is structured around a unique integrated business model built on four core business lines; power and water; energy from waste; project management and infrastructure solutions and services. OAK is able to leverage its resources and expertise across each of its business lines in order to provide its clients with a comprehensive range of intelligently assessed, innovative and proven turn-key service solutions, tailored to meet the specific needs of each client, delivered by its highly skilled in-house chartered engineers and certified project managers. OAK’s track record boasts the delivery of specialist solutions to majors within the oil & gas and petrochemical industries, working directly with governments under Public-Private-Partnership (PPP) schemes and bringing together its unique capabilities alongside strategic alliances with specialist international technologists and Original Equipment Manufacturers (OEM), offering unrivalled top tier professionalism, experience and expertise. OAK’s strategy brings together upstream, midstream, and downstream capabilities throughout the Oil & Gas and Energy Industries allowing OAK to create new sources of value, improving productivity and project economics through integrated technology and service offerings. Generating electricity from renewable energy technologies, OAK builds, owns and operates Waste-to-Energy (WTE) assets, which convert solid waste into gas, generating electricity, providing governments with a sustainable source of gas and/or electricity whilst disposing of unwanted waste, which is usually landfilled. OAK’s WTE solution utilises leading High Temperature Pyrolysis (HTP) technology which effectively converts both organic and inorganic waste materials into a high Calorific Value (CV) synthetic gas through thermochemical decomposition, which can be used to power gas generators and/or steam turbines for sustainable generation. HTP is a close loop process which has been developed to operate at high elevate temperatures (>700˚C) allowing for a more thorough chemical breakdown, improving production yield and minimising emissions. OAK’s WTE solution offers a sustainable source of renewable energy with significant positive environmental impacts, including the elimination of landfilling and the reduction of Green House Gas (GHG) emission.
Waste to Energy International OÜ (WTEI) – Technical Partner Waste to Energy International OÜ (WTEI) are developers in waste-to-energy, solar and wind sector. Unlike to many other development companies on the market, WTEI have strong experience in construction of real waste-to-energy and waste utilization objects. WTEI provide the full development cycle of an alternative energy facility: from the green grass to commissioning. This includes technical feasibility study, procurement, construction supervision, commissioning and personnel training. Project calculations are conducted by the proprietary, fully parametric financial model, which has been accepted a number of times by financial advisors in Switzerland, UK and Sri Lanka. WTEI is a company of international environmentalists, highly qualified engineers, experienced economists and waste-to- energy project developers. WTEI have strong relationships with a number of world leader technology providers, including producers of reciprocating grates and fluidized bed incineration equipment, pyrolysis, sorting, packing, and waste processing equipment.
Chinese Machinery Engineering Corporation (CMEC) – EPC Partner China Machinery Engineering Corporation (CMEC) was built on its predecessor China National Machinery & Equipment Import & Export Corporation, which was set up in 1978 and in 2012, CMEC was listed on the Hong Kong Stock Exchange. Its controlling stake is now owned by China National Machinery Industry Corporation. The core business of CMEC is 12 Engineering Contracting but as a large international conglomerate, it also extends into Trade, Investment, R&D and international Services. With EPC at its core and more than 30 years of experience in the engineering industry, CMEC has developed the capacity to provide ‘one-stop’, customized, complete plant solutions spanning preliminary planning, EPC, Financing and Operation and Maintenance. It has expanded its business presence to 47 countries and regions in Asia, Africa, Europe and South America, forming a Project Contracting System with Electric Power Energy at the core and covering Transportation, Telecommunications, Waterworks, Building Materials and Cement.
Ministry of Military Production (NOMP) – Local/Ministerial Partner The National Organization for Military Production (NOMP) within the Ministry of Military Production is a major industrial facility with vast industrial and technological capabilities and is involved in the implementation of major national projects across the country as part of its comprehensive development plan for 2030 NOMP, supervises sixteen military factories of which fourteen are producing civilian goods and military products. Military production plants are not planned for privatisation however there is interest in licensing arrangements with foreign firms to enhance their production mix and improve quality. NOMP are looking to expand into new, productive product lines for domestic and export sales, and are open to foreign licensing/joint venture proposals. “Defence conversion” (reinvestment) in the sense of making productive use of surplus military capacity is under intense discussion within the Egyptian military