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Waste-to-energy (WtE) or energy-from-waste (EfW) is an advanced waste disposal process that generates electricity from non-hazardous waste. Why is WtE important? Dumping tons of waste in landfills compounds the climate crisis and jeopardizes the safety of people, animals, and natural resources.
The growing demand for waste management and increasing focus on non-fossil fuel sources of energy are primarily driving the rise of the global WtE market.
Waste is generated on a regular basis from agricultural facilities, homes, businesses, industries, and so on. A waste-to-energy plant (or WtE facility) helps in turning waste into energy (heat or electricity). Waste-to-energy technology (WtE technology) has evolved to include breakthrough processes in environmentally friendly organic waste disposal and solid waste management.
Although waste minimization and waste recycling remain the top priorities of waste management policies, waste facilities are rising in prominence as sustainable waste disposal mechanisms. In the coming years, modern WtE technologies are expected to play a key role in producing usable energy by burning waste while mitigating climate change.
Do you want to explore waste-to-energy and related technologies in detail? Keep reading to learn more.
What is Waste-to-Energy?
Waste-to-energy (WtE) is a process of energy recovery from waste material. Except for hazardous waste, various waste materials are transported to WtE facilities to produce clean energy. For example, the US has 75 facilities that combust municipal solid waste for energy recovery. A typical WtE plant generates around 550 kilowatt hours (kWh) of energy per ton of waste.
Contrary to landfills, which have been the standard repositories of waste over the years, a waste-to-energy facility aids in efficient waste management, reduces pollutants, generates usable energy, and reduces waste transportation.
The main types of waste include:
- Agricultural waste
- Food waste (commercial, institutional, and residential)
- Household waste
- Manure slurries (from livestock operations)
- Medical waste
- Municipal solid waste (MSW)
- Process waste (such as biosolids and sludges from municipal wastewater treatment processes)
- Residual waste (waste material generated by agricultural, mining, and industrial operations)
Waste-to-Energy (WtE) Technologies
Most waste-to-energy processes typically produce electricity or heat directly through combustion. Various thermal and non-thermal processes are used for energy recovery from treating and processing municipal waste and other types of waste. Also known as “waste-to-energy management methods,” the most popular waste-to-energy (WtE) technologies are:
Physical
Waste is processed mechanically into a more durable and suitable form for further processing (examples include pellets, wood briquettes, and wood chips).
Biological
This method uses microbes (micro-organisms) to break down waste in the absence of oxygen for fuel generation. Biological waste treatment methods include:
Fermentation: This metabolic process converts solid waste into ethanol, acids, and traces of gases in the presence of yeast and bacteria. The resulting biogas from waste is used directly as a fuel.
Biogas formation: In this process (anaerobic digestion or AD), micro-organisms break down biodegradable material in the absence of oxygen to produce gases, such as carbon dioxide and methane that constitute “biogas.” Biogas is used for heating and electricity generation and as a vehicle fuel.
Thermal
The thermal treatment of waste is divided into the following:
Direct combustion: In this process, waste is dried and burned to produce heat from the combustion of solid waste. The heat generated changes water into steam that runs a turbine for power generation.
Plasma arc gasification: This process uses plasma arc torch (at 2,200-13,900°C) to produce an electric arc that breaks down waste for conversion into synthetic gas (syngas) and slag. The syngas is used for heat generation or as a fuel in internal combustion engines.
Thermal gasification: This process converts an organic or fossil-fuel-based hydrocarbon material into carbon monoxide, carbon dioxide, and hydrogen at a very high temperature (> 700°C) with a limited oxygen supply. The resulting gas fuel mixture is known as “syngas,” “synthetic gas,” or “producer gas” and is used for power generation.
Pyrolysis: Also known as “dry distillation,” “destructive distillation,” or “cracking,” pyrolysis is a thermo-chemical method that involves heating waste at an elevated temperature in the absence of oxygen to produce combustible gases as well as liquid and solid residues.
Apart from the conventional WtE technologies, new WtE technologies like Hydrothermal Carbonization (HTC) are gaining recognition for lowering the processing time and simulating operating conditions required to generate the same amount of energy as the geothermal conversion of wet waste.
Another promising technology is a nearly “zero-waste” Dendro Liquid Energy (DLE) WtE technology that is believed to be less expensive and four times more efficient than anaerobic digestion.
Furthermore, the WtE company—Sierra Energy—has developed the FastOx® gasification technology that turns trash (construction and demolition materials, household waste, medical waste, tires, etc.) into energy without burning.
The FastOx system uses heat, oxygen, and steam to break down waste at the molecular level and facilitate complete conversion with no toxic by-products.
The high-value end products of the FastOx waste gasification comprise:
- Electricity (generated with lower specific emissions than natural gas)
- Hydrogen (used in a pipeline or a hydrogen fuel cell)
- Diesel (aromatic-free and sulfur-free diesel)
- Ammonia (used as a feedstock for chemical fertilizers)
Advantages of WtE
Let us look at WtE’s primary advantages:
Decreases unusable waste
The WtE process recycles excess waste, including metal waste (such as steel and aluminum) and decreases the amount of unusable waste.
Meets heating demand
Combined heat and power (CHP) WtE plants are quite effective in providing heating for residential areas and industrial sites. Countries with cold weather conditions can especially benefit from CHP district heating.
Provides clean power
A ton of waste can yield sufficient energy to power an individual housing unit for a month. Putting garbage to good use is pivotal to environmental protection and energy production.
Reduces landfill burden
Converting waste into energy greatly reduces landfill waste and, subsequently, landfill gases. WtE can significantly reduce greenhouse gas emissions, such as methane and CO2 emissions. For example, processing every ton of municipal solid waste reduces greenhouse gases by up to one ton.
Disadvantages of WtE
Despite its key benefits, WtE has some limitations, such as the following:
Burning waste is potentially harmful
Burning waste or waste incineration is viewed as harmful to the environment because plastics and other oil-based products burned in WtE can emit damaging greenhouse gas emissions. However, advancements in WtE technology have led to the use of filters to trap unsafe gases and particulate dioxin.
A risk of disincentivizing recycling
A major risk of WtE is the possibility of disincentivizing other impactful waste management solutions of reduction, reuse, and recycling.
WtE cannot be considered a one-stop waste management technique. Rather, WtE should be part of a responsible waste management framework.
Loss of recoverable materials
WtE does provide the opportunity to recover some resources, but it has the potential to destroy other recoverable resources like minerals and wood. For example, the “mass burn” incineration process burns MSW wholesale rather than separating the waste before incineration.
Unregulated waste trade
Improper waste disposal and unregulated waste trade in the name of WtE are dangerous and nullify the purpose of a waste management plan. For example, shipping hazardous waste not meant for incineration and burning it before landfilled increases environmental risk.
Waste incineration is expensive
Securing finance for a WtE plant operation and maintenance is an ongoing challenge in waste management. In addition, a WtE plant requires regular maintenance and trained personnel for day-to-day management.
Leading WtE Companies
WtE companies are actively involved in energy generation through waste treatment. Some of the leading WtE companies in the world are listed below:
Babcock & Wilcox Enterprises, Inc.
Babcock & Wilcox (B&W) is a leading company in energy and environmental technologies. B&W’s expertise ranges from providing efficiency-maximizing boiler designs for mass burning to highly advanced combustion grates for WtE applications.
B&W’s renewable, environmental, and thermal solutions include, but are not limited to the following:
- A-S-H® material and ash handling
- DynaGrate® combustion grate
- Energy recovery by flue gas condensation
- Heat recovery steam generators
- Multiple pass furnace with vertical convection pass
- Pulverizers
- Single pass furnace
- Sootblowers
- SPIG™ cooling systems
- Waste incineration by emissions control
Covanta Holding Corporation
Covanta is a leading WtE company with the following specialties:
- Electronic waste recycling
- Liquid waste management
- Metals recycling
- Plastic and packaged goods recycling
- Secure product destruction
- Total ash processing
- Total waste and materials management
- Waste-to-energy
- Zero waste-to-landfill
According to Covanta, the company’s WtE facilities reduce several million tons of greenhouse gas emissions and power 1 million homes annually. Moreover, Covanta’s WtE process recycles 600,000 tons of metal each year.
Hitachi Zosen Inova AG
Hitachi Zosen Inova (HZI) is a global cleantech company with expertise in energy-from-waste (EfW) and renewable gas. With a 90-year history of building and maintaining plants, HZI specializes in:
- Plant engineering and construction (project development, engineering & construction, technology provider)
- Service (Service agreements and products, plant performance upgrades)
- Energy-from-waste (combustion, flue gas treatment, energy recovery, residue treatment)
- Renewable gas (Kompogas® anaerobic digestion, BioMethan gas upgrading, EtoGas power-to-gas)
Ramboll Group A/S
Ramboll is a global engineering, design, and consultancy company that provides a wide variety of services across disciplines, such as architecture & landscape, buildings, energy, environment & health, management consulting, and transport.
Ramboll’s water and wastewater treatment services support public and industrial clients with all aspects of wastewater treatment. With 50+ years of experience in water and wastewater treatment, Ramboll’s expertise encompasses process design, layout and detailed design in addition to new waterworks and modernization of existing facilities.
Other prominent players in the WtE space include Abu Dhabi National Energy Company PJSC (TAQA), China Everbright International Co., Ltd., Veolia Environnement S.A. (Veolia), Wheelabrator Technologies Inc. (WIN Waste Innovations), Xcel Energy Inc., and more.
WtE Market Outlook
The global WtE market has shown a remarkable increase over the years. According to Blackridge Research & Consulting’s global WtE market report, the WtE market is estimated to reach a market size of over USD 70 billion by 2027 at a CAGR of 7.35%.
The report identifies the Middle East and Africa as the fastest-growing markets and the Asia Pacific (significant expansions in India and China) as the largest market in the WtE industry.
How feasible is the “gold-from-garbage” concept? Although WtE is a suitable solution in the context of the circular economy and waste hierarchy, waste incinerators have been drawing criticism for releasing harmful pollutants, including dioxins and heavy metals and impacting air quality.
An incinerator is the most commonly used waste disposal unit. However, the growing concern over incineration plants located in low-income areas, producing toxic ash, and violating emission regulations, is shifting the renewable energy debate toward more upstream waste management solutions.
Public demand and government efforts are also focusing on:
- Reducing waste generation in the first place
- Preparing for reuse
- Encouraging waste recycling and
- Promoting a less consumptive lifestyle (compatible with zero-waste goals)
Notwithstanding the challenges of WtE, modern WtE facilities are equipped with advanced technology to manage waste efficiently, produce clean energy, and reduce the risk of greenhouse gas emissions. For example, methane and carbon dioxide comprise 90-98% of landfill gas (LFG), with methane (a greenhouse gas) considered 84 times more potent as a climate-warming gas than carbon dioxide.
Moreover, WtE technology changes life-risking garbage into life-enhancing energy. Responsible waste management plans are replacing wasteful incineration practices of the previous decades for a clean, sustainable future.
For example, the US WtE industry is known for developing one of the cleanest forms of energy generation and meeting or exceeding standards set by the US Environmental Protection Agency (EPA).
Conclusion
Gone are the days of trash burners that emitted toxins into the air. The new-age WtE facilities are equipped with advanced pollution control features to ensure safety for human and animal health and ecological stability.
As the global demand for economically and environmentally sustainable WtE solutions rises rapidly, it is essential to:
- Identify barriers to WtE adoption
- Encourage new projects in emerging and established markets
- Establish a structured network of WtE facilities
Successful development of WtE initiatives necessitates collaboration between governments, manufacturers, owners, planners, and more to convert waste into energy. For example, the European Union’s efforts to replace the existing landfills with WtE facilities signifies an exponential growth rate for the European WtE market.
Furthermore, active private sector participation in contrast to traditional public sector monopoly is bound to accelerate the development of large-scale WtE projects and, consequently, decrease WtE prices in the future.
The world is looking toward a sustainable and safe energy transition. In this effort to deliver clean energy, waste-to-energy (WtE) is the catalyst that can transform waste into a wonderful source of energy.