In 2015, the United States got about 14 billion kilowatt-hours of electricity from burning municipal solid waste, or MSW. Seventy-one waste-to-energy plants and four additional power plants burned around 29 million tons of MSW in the U.S. that year. However, just 13 percent of the country’s waste becomes energy. Around 35 percent is recycled or composted, and the rest ends up in landfills.

Recovering Energy Through Incineration

The predominant technology for MSW-to-energy plants is incineration, which involves burning the trash at high temperatures. Similarly to how some facilities use coal or natural gas as fuel sources, power plants can also burn MSW as fuel to heat water, which creates steam, turns a turbine and produces electricity.

Several methods and technologies can play a role in burning trash to create electricity. The most common type of incineration plant is what’s called a mass-burn facility. These units burn the trash in one large chamber. The facility might sort the MSW before sending it to the combustion chamber to remove non-combustible materials and recyclables.

These mass-burn incineration systems use excess air to facilitate mixing, and ensure air gets to all the waste. Many of these units also burn the fuel on a sloped, moving grate to mix the waste even further. These steps are vital because solid waste is inconsistent, and its content varies. Some facilities also shred the MSW before moving it to the combustion chamber.

Gasification Plants

Another method for converting trash into electricity is gasification. This type of waste-to-energy plant doesn’t burn MSW directly, but instead uses it as feedstock for reactions that produce a fuel gas known as synthesis gas, or syngas. This gas typically contains carbon monoxide, carbon dioxide, methane, hydrogen and water vapor.

Approaches to gasification vary, but typically include high temperatures, high-pressure environments, very little oxygen and shredding MSW before the process begins. Common MSW gasification methods include:

• Pyrolysis, which involves little to no oxygen, partial pressure and temperatures between approximately 600 and 800 degrees Celsius.
• Air-fed systems, which use air instead of pure oxygen and temperatures between 800 and 1,800 degrees Celsius.
• Plasma or plasma arc gasification, which uses plasma torches to increase temperatures to 2,000 to 2,800 degrees Celsius.

Syngas can be burned to create electricity, but it can also be a component in the production of transportation fuels, fertilizers and chemicals. Proponents of gasification report that it is a more efficient waste-to-energy method than incineration, and can produce around 1,000 kilowatt-hours of electricity from one ton of MSW. Incineration, on average, produces 550 kilowatt-hours.

Also Read: The Role of an Electrician in a Waste-to-Energy Plant

Challenges of MSW-to-Energy

Turning trash into energy seems like an ideal solution. We have a lot of trash to deal with, and we need to produce energy. MSW-to-energy plants solve both of those problems. However, a relatively small amount of waste becomes energy, especially in the U.S.

This lack may be due largely to the upfront costs of building a waste-to-energy plant. It is much cheaper in the short term to send trash straight to a landfill. Some people believe these energy production processes are just too complicated and expensive. Gasification, especially, has a reputation for being too complex.

Environmental concerns also play a role, since burning waste can release greenhouse gases. Although modern technologies can make burning waste a cleaner process, its proponents still complain it is too dirty.

Despite these challenges, as trash piles up and we continue to look for new sources of energy, waste-to-energy plants may begin to play a more integral role in our energy production and waste management processes. If we handle it responsibly and efficiently, it could become a very viable solution to several of the issues our society faces.

The post Everything You Should Know About MSW-to-Energy first appeared on BioEnergy Consult.

Understanding the function of compressed air in biogas production highlights its importance in ensuring efficient, reliable and safe renewable energy generation, even for readers without a technical background.

How Biogas Is Made From Waste to Energy

Biogas is a renewable energy source produced when organic materials such as animal waste, food scraps or wastewater solids break down in environments devoid of free oxygen. This process is called anaerobic digestion. During this biochemical conversion, naturally occurring bacteria ferment the organic matter and emit a mixture of mostly methane and carbon dioxide, known as biogas. This gas can then be used for heating, electricity generation or fuel applications.

The use of organic waste for power has a long history. For example, biomass such as wood once supplied as much as 70% of the United States’ energy in the late 19th century, demonstrating the enduring potential of biological materials as reliable sources. Today, biogas represents a modern, controlled application of this principle, harnessing waste streams to produce sustainable energy.

In industrial facilities, producing biogas involves several coordinated steps that systematically transform organic waste into usable energy:

• Feedstock collection: Organic materials are gathered and prepared — often blended with water to form a slurry that is easier to process. This preparation ensures a consistent mixture for efficient digestion in the tanks.
• Anaerobic digestion tank: The slurry enters a sealed tank called a digester, where microbes break down the waste without oxygen. This produces biogas while stabilizing the organic material.
• Biogas capture: The gas rises to the top of the digester and is collected through piping systems. This collected gas is then ready for treatment or direct use in energy applications.
• Treatment and conditioning: Raw biogas often contains water vapor, hydrogen sulfide and carbon dioxide, which may be removed through scrubbing, drying or pressure swing adsorption (PSA). It’s used to improve methane concentration for energy use or pipeline injection.
• Utilization: Cleaned biogas can power generators to produce electricity, heat buildings or be further compressed for use as vehicle fuel or for distribution via pipelines. This versatility makes biogas a valuable and flexible renewable energy source.

This sequence relies on mechanical systems, including compressors, blowers and a network of instrumentation, to manage gas flows, material movement and process conditions.

Where Compressed Air Fits Into Biogas Production

Compressed air systems play several essential roles in a biogas facility’s operations.

Pneumatic Conveying of Materials

Within the plant, compressed air can be used to move organic feedstock or processed residues — called digestate — between stages without manual handling. This pneumatic conveying system efficiently transfers solids and liquids, reducing labor and improving uptime.

Treatment and Upgrading Processes

Compressed air supports gas conditioning steps. For example, technologies like PSA depend on alternating pressurization and depressurization to remove impurities such as carbon dioxide and water, enriching the biogas’s methane content. This makes it suitable for high-value applications like vehicle fueling or pipeline injection.

Storage and Distribution

Once biogas has been conditioned and upgraded into a higher-quality product, sometimes called renewable natural gas, it must be compressed for storage or transport. Compression increases its energy density, enabling effective storage in tanks, integration into pipelines or use in compressed natural gas vehicles.

Equipment Maintenance

Compressed air systems also support maintenance activities. Clean, dry compressed air helps purge lines, clear dust or debris from equipment housings, and maintain vacuum systems. This extends operating life and reduces unscheduled downtime.

Why Compressed Air Design Matters

Biogas production environments contain flammable and potentially hazardous gases, especially methane and hydrogen sulfide. These compounds pose a risk if they accumulate in the presence of ignition sources. Compressing any gas, including biogas, inherently raises both pressure and the potential consequences of a leak or equipment failure. Therefore, air compression equipment must be designed to handle these conditions safely.

Specialized compressors and blowers used in biogas facilities must meet stringent standards for:

• Gas compatibility: Components and seals must withstand biogas composition without corrosion or degradation.
• Pressure handling: Systems must be able to elevate biogas or air to the desired levels without overpressurizing downstream equipment.
• Intrinsic safety: Design features must prevent sparks or hot surfaces that could ignite a flammable gas mixture.

The Importance of Safety

Safety is a top priority in biogas facilities because the gases produced can be flammable and toxic. Careful management of methane, hydrogen sulfide, and system pressures ensures both personnel and equipment remain protected. Safety systems are an essential part of daily operations.

Methane Flammability

Methane, the primary component of biogas, is flammable over a broad range of concentrations when mixed with air. This means that any leak in a compression line or equipment housing that allows air ingress can create an explosive atmosphere. Proper monitoring and pressure control are essential to prevent such dangerous conditions.

Pressure and Fire Safety Interlocks

In biogas production, compressed air moves feedstock, aids gas treatment, and compresses biogas for storage or distribution. Because the gas is flammable, safety is critical. Digital pressure switches monitor pressure, display readings, record run hours, monitor motor amps and cycles, and actuate drain valves. They allow easy adjustment and provide reliable protection against overpressure or fire, keeping operations safe and efficient.

Hydrogen Sulfide Toxicity and Corrosion

Hydrogen sulfide, often present in raw biogas, is both toxic and corrosive. Even at low concentrations, it can harm human health and degrade system components, increasing the likelihood of leaks or equipment failure if not properly managed.

Best Practices in Compressed Air Integration

To ensure compressed air systems operate reliably and safely in biogas facilities, plant designers and operators follow several best practices:

• Regular calibration and inspection: Gauges, pressure switches, and relief valves must be calibrated and tested frequently to ensure accuracy and responsiveness.
• Flame and explosion arrestors: Installing devices that prevent flames from propagating back through piping reduces fire hazards, especially at gas line interfaces with compressors.
• Redundant safety systems: Multiple independent sensing and shutdown mechanisms provide layers of protection in case one system fails.
• Operator training: Skilled personnel who understand gas properties, compressor operation and emergency procedures greatly enhance facility safety.
• Routine maintenance and leak detection: Proactive inspection and maintenance of compressors, seals, and lines help prevent leaks and mechanical failures.

Ensuring Efficiency and Safety Through Compressed Air in Biogas Production

Compressed air systems are a vital part of modern biogas production facilities. They support material transport, gas treatment and upgrading, storage and maintenance operations from beginning to end. Because biogas contains flammable and potentially hazardous gases, compressed air systems must be engineered and operated with robust safety practices, including the use of pressure switches to help manage fire and explosion risk.

When well-designed and carefully maintained, these systems make biogas production safer, more efficient and more scalable — further advancing this renewable energy pathway toward a sustainable future.

The post Critical Role of Compressed Air Systems in Biogas Production Facilities first appeared on BioEnergy Consult.

Advantages of Biomethane

The key advantage of biomethane is that it is less corrosive than biogas which makes it more flexible in its application than raw biogas. It can be injected directly into the existing natural gas grid leading to energy-efficient and cost-effective transport, besides allowing natural gas grid operators to persuade consumers to make a smooth transition to a renewable source of natural gas.

Biogas can be upgraded to biomethane and injected into the natural gas grid to substitute natural gas or can be compressed and fuelled via a pumping station at the place of production. Biomethane can be injected and distributed through the natural gas grid, after it has been compressed to the pipeline pressure.

The injected biomethane can be used at any ratio with natural gas as vehicle fuel. In many EU countries, the access to the gas grid is guaranteed for all biogas suppliers.

A major advantage of using natural gas grid for biomethane distribution is that the grid connects the production site of biomethane, which is usually in rural areas, with more densely populated areas. This enables biogas to reach new customers.

Storage of Biomethane

Biomethane can be converted either into liquefied biomethane (LBM) or compressed biomethane (CBM) in order to facilitate its long-term storage and transportation. LBM can be transported relatively easily and can be dispensed through LNG vehicles or CNG vehicles. Liquid biomethane is transported in the same manner as LNG, that is, via insulated tanker trucks designed for transportation of cryogenic liquids.

Biomethane can be stored as CBM to save space. The gas is stored in steel cylinders such as those typically used for storage of other commercial gases.

Applications of Biomethane

Biomethane can be used to generate electricity and heating from within smaller decentralized, or large centrally-located combined heat and power plants. It can be used by heating systems with a highly efficient fuel value, and employed as a regenerative power source in gas-powered vehicles.

Biomethane, as a transportation fuel, is most suitable for vehicles having engines that are based on natural gas (CNG or LNG). Once biogas is cleaned and upgraded to biomethane, it is virtually the same as natural gas.

Because biomethane has a lower energy density than NG, due to the high CO₂ content, in some circumstances, changes to natural gas-based vehicle’s fuel injection system are required to use the biomethane effectively.

The post Biomethane – The Green Gas first appeared on BioEnergy Consult.

Historically, burying the wastes is the most preferred method for waste management in many countries. This method is still used in many more countries. Tackling environmental issues has become more important and more preferred than pollution and consumption of unsustainable utilization of resources. Most importantly, the primary objective of waste management is to put emphasis on protecting the people and environment from potentially harmful effects of waste.

Methods of Solid Waste Management

Depending on the types of wastes generated, four methods of solid waste management has been used throughout the history, i.e. dumping, incineration, recycling and waste prevention. Waste generated from household is much different from industrial waste, agricultural waste, medical waste or mining wastes.

When wastes contain any hazardous component, or it has capability to become hazardous with time, poses very serious threat to environment and health. Hazardous wastes generated needs to be handled very carefully, with special techniques. This is one of the major reasons of open landfills are getting replaced with sanitary landfills.

At a landfill, wastes are covered with thick layer of soil. By the late 1950, this practice was very common for waste management across the world. Earlier landfills had considerable sludge and methane emissions, which were harmful to the environment as well as animal and human health. But these issues have been resolved largely by modern disposal methods, which were developed around 20 years ago. Modern landfills are equipped with thick layer of clay followed by plastic sheets. This method was practiced by some nations and still going on.

In 1930-1940, many cities in USA adopted new technology to curb waste issues by burning at high temperature, this method is known as incineration. During initial years, this method was not very efficient and emit very large amount of poisonous gasses, this is the major reason of incinerators shut down during that period. During mid-1970s, scientists modified incinerators to generate energy, which are known as waste to energy plants. But after around a decade, it has become major issue to build these plants, again because of emission issues.

With development of technology, waste burning in advanced form of incinerators became common in 1970s, researchers across the world bet on incinerators or waste to energy plants for solution to energy crisis in 1973. However, with realisation of impact on environment and air quality, it become very difficult to find location to build any waste to energy plants, mainly because of public opposition. Another issue with incinerator is production of ashes, which contain huge amount of heavy metals, toxic and inorganic compounds.

Future of Solid Waste Management

The overall concept of wastes needs to be considered economically, it will be more considered as economically viable product if waste is considered as an inefficiency of the production process not as rejected residue of waste product. A permanent rejection or heavy restriction into products which produces waste that cannot be accumulated back into the environment safely.

The major challenge in waste management is to persuade people/community to consider waste as a resource, rather than a liability on society, which can be created with more innovation and technological development of manufacturing industry, waste processing industry and new business model and plans.

This planning system will create circular economy where product value created by inputs (e.g. energy, materials, labour etc.) is extended by enabling a material that goes into circular economy, beyond product life. We go from mineral to metals to product then back to minerals/metals. By understanding economic cycle of waste, people will understand the creation of opportunities to more sustainable product in future with limited resources.

The post Solid Waste Management – History and Future Outlook first appeared on BioEnergy Consult.

What is Food Recycling?

Food recycling is the process of taking food waste and turning it into a useful resource. This can be done through a variety of methods, including composting, anaerobic digestion, and fermentation. The result is a valuable product that can be used as a fertilizer or as a source of energy.

Generating Bioenergy from Food Waste

One of the most promising applications of food waste recycling is the generation of bioenergy. Bioenergy is a form of renewable energy that is derived from organic matter, such as food waste. By using food waste to generate bioenergy, we can reduce our dependence on fossil fuels and decrease our carbon footprint.

1. Anaerobic Digestion

Anaerobic digestion is one of the most common methods of generating bioenergy from food waste. This process involves breaking down organic matter in the absence of oxygen, producing biogas as a by-product. Biogas is a mixture of methane and carbon dioxide that can be burned to generate electricity or heat.

The process of anaerobic digestion starts with the collection of food waste. This can be done at a household level, with individuals separating their food waste from other types of waste. Alternatively, food waste can be collected from commercial and industrial sources, such as restaurants and food processing plants.

Once collected, the food waste is transported to an anaerobic digestion facility, where it is mixed with water and placed in a sealed tank called a digester. Inside the digester, bacteria break down the organic matter in the absence of oxygen, producing biogas as a by-product. The biogas is then collected and used to generate electricity or heat.

Advantages of Anaerobic Digestion

One of the advantages of anaerobic digestion is that it can be done on a small scale, making it a viable option for households and small businesses. In fact, many households in rural areas use small-scale anaerobic digesters to generate their own electricity and heat.

Another advantage of anaerobic digestion is that it produces a valuable fertilizer as a by-product. The residue left over from the process, known as digestate, is a nutrient-rich material that can be used as a fertilizer for crops.

2. Fermentation

Fermentation is another method of generating bioenergy from food waste. This process involves breaking down organic matter using microorganisms, such as yeast or bacteria. The result is a product such as ethanol or biobutanol, which can be used as a fuel for vehicles or as a source of energy.

The process of fermentation starts with the collection of food waste, which is then mixed with water and enzymes to break down the organic matter. Microorganisms are then added to the mixture, which ferment the organic matter and produce ethanol or biobutanol as a by-product.

Advantages of Fermentation 

Like anaerobic digestion, fermentation can be done on a small scale, making it a viable option for households and small businesses. However, it is not as common as anaerobic digestion, as it requires more specialized equipment and expertise.

The post How Food Waste and Recycling Could Generate Bioenergy first appeared on BioEnergy Consult.

An advocate of public understanding of science, Shawn Lawrence Otto regrets that the facts are not able to hold the same sway. Some US liberal groups such as the Center for American Progress are beginning to realize that the times and science have changed. It will take more consensus on the science and the go ahead from environmental groups before the conversation moves forward, seemingly improbable but not without precedent.

Spittelau Waste-to-Energy Plant

Polarized Discussion

Waste-to-Energy or recycling has kept public discourse from questioning whether there may not be intermediate or case specific solutions. This polarization serves to move the conversation nowhere. For now it can be agreed that landfills are devastating in their contribution to Climate Change and must be done away with.

The choice then, of treatment processes for municipal solid waste are plentiful. If after recovery of recyclable materials there remains a sizeable waste stream the option of waste-to-energy can be explored.

Primary Considerations in WTE Projects

The post Key Challenges in the Implementation of Waste-to-Energy first appeared on BioEnergy Consult.

The Problem of Waste

Municipal waste generation in Saudi Arabia is increasing at an unprecedented rate. Due to high population growth rate, rapid urbanization and fast-paced economic development, MSW generation is expected to cross 30 million tons per year by 2033. More than 75 percent of Kingdom’s population is concentrated in urban areas, and collected garbage is thrown in landfills or dumpsites without any processing or treatment.

Most of the landfills in Saudi Arabia are non-sanitary and prone to problems like leachate, vermin, flies and spontaneous fires, apart from greenhouse gas emissions.  It has become necessary for the Saudi government to devise an integrated waste management strategy, using international best practices and modern technologies, to tackle heaps of garbage accumulating across the country.

Promise of Waste-to-Energy

Waste-to-energy provides a cost-effective and eco-friendly solution to both energy demand and MSW disposal problems in Saudi Arabia. Increasing waste generation, inability of existing solutions to tackle waste and expansion of cities into ex-dump sites are strong drivers for large-scale deployment of WTE systems in the Kingdom.

Saudi Arabia has tremendous waste-to-energy potential due to plentiful availability of good quality municipal waste. Modern waste-to-energy technologies, such as RDF-based incineration, gasification, pyrolysis and anaerobic digestion have the ability to transform power demand and waste management scenario in the country.

A typical 250 – 300 tons per day garbage-to-energy plant can produce around 3 – 4 MW of electricity and a network of such plants in cities around the country can make a real difference in waste management as well as energy sectors.  In fact, such plants also produce tremendous about of heat energy which can be utilized in process industries and district cooling systems, further maximizing their usefulness.

Key Challenges

Around the world, waste-to-energy finds wide acceptance as a tool to manage urban wastes, with more than 1,000 waste-to-energy plants in operation globally, especially in Europe, China and the Asia-Pacific. However, waste-to-energy is struggling to get off-the-ground in Saudi Arabia due to several issues, the main reason being the cheap and plentiful availability of oil which prevents decision-makers to set effective regulations for waste-to-energy development in the country.

Policy-makers in KSA should consider waste-to-energy as a sustainable waste management solution, rather than as a power-producing industry. Unlike Western countries, waste management services are practically free-of-cost for the waste generators which act as a deterrent for governmental investment in new waste management solutions and technologies, such as waste-to-energy. Infact, waste collection, transport and disposal methods in Saudi Arabia do not match the standards of a developed country.

Future Outlook

Vision 2030, touted as most comprehensive economic reform package in Saudi history, puts forward a strong regulatory and investment framework to develop Saudi waste-to-energy sector. An ambitious target of 3GW of energy from waste is to be achieved by 2025.  A methodical introduction of modern waste management techniques like material recovery facilities, waste-to-energy systems and recycling infrastructure can significantly improve waste management scenario and can also generate good business opportunities.

To sum up, environmental issues associated with non-sanitary landfills, ineffectiveness of prevalent waste management model and rising energy demand are key drivers for development of waste-to-energy sector in Saudi Arabia.

The post Waste-to-Energy in Saudi Arabia first appeared on BioEnergy Consult.

What is Biomass

Biomass comes from a variety of sources which include:

• Wood from natural forests and woodlands
• Forestry plantations
• Forestry residues
• Agricultural residues such as straw, stover, cane trash and green agricultural wastes
• Agro-industrial wastes, such as sugarcane bagasse and rice husk
• Animal wastes (cow manure, poultry litter etc)
• Industrial wastes, such as black liquor from paper manufacturing
• Sewage
• Municipal solid wastes (MSW)
• Food processing wastes

Biomass energy projects provide major business opportunities, environmental benefits, and rural development.  Feedstocks for biomass energy project can be obtained from a wide array of sources without jeopardizing the food and feed supply, forests, and biodiversity in the world.

1. Agricultural Residues

Crop residues encompasses all agricultural wastes such as bagasse, straw, stem, stalk, leaves, husk, shell, peel, pulp, stubble, etc. Large quantities of crop residues are produced annually worldwide, and are vastly underutilised. Rice produces both straw and rice husks at the processing plant which can be conveniently and easily converted into energy.

Significant quantities of biomass remain in the fields in the form of cob when maize is harvested which can be converted into energy. Sugar cane harvesting leads to harvest residues in the fields while processing produces fibrous bagasse, both of which are good sources of energy. Harvesting and processing of coconuts produces quantities of shell and fibre that can be utilized.

Current farming practice is usually to plough these residues back into the soil, or they are burnt, left to decompose, or grazed by cattle. These residues could be processed into liquid fuels or thermochemically processed to produce electricity and heat. Agricultural residues are characterized by seasonal availability and have characteristics that differ from other solid fuels such as wood, charcoal, char briquette. The main differences are the high content of volatile matter and lower density and burning time.

2. Animal Waste

There are a wide range of animal wastes that can be used as sources of biomass energy. The most common sources are animal and poultry manure. In the past this waste was recovered and sold as a fertilizer or simply spread onto agricultural land, but the introduction of tighter environmental controls on odour and water pollution means that some form of waste management is now required, which provides further incentives for waste-to-energy conversion.

The most attractive method of converting these organic waste materials to useful form is anaerobic digestion which gives biogas that can be used as a fuel for internal combustion engines, to generate electricity from small gas turbines, burnt directly for cooking, or for space and water heating.

3. Forestry Residues

Forestry residues are generated by operations such as thinning of plantations, clearing for logging roads, extracting stem-wood for pulp and timber, and natural attrition. Harvesting may occur as thinning in young stands, or cutting in older stands for timber or pulp that also yields tops and branches usable for biomass energy. Harvesting operations usually remove only 25 to 50 percent of the volume, leaving the residues available as biomass for energy.

Stands damaged by insects, disease or fire are additional sources of biomass. Forest residues normally have low density and fuel values that keep transport costs high, and so it is economical to reduce the biomass density in the forest itself.

4. Wood Wastes

Wood processing industries primarily include sawmilling, plywood, wood panel, furniture, building component, flooring, particle board, moulding, jointing and craft industries. Wood wastes generally are concentrated at the processing factories, e.g. plywood mills and sawmills. The amount of waste generated from wood processing industries varies from one type industry to another depending on the form of raw material and finished product.

Generally, the waste from wood industries such as saw millings and plywood, veneer and others are sawdust, off-cuts, trims and shavings. Sawdust arise from cutting, sizing, re-sawing, edging, while trims and shaving are the consequence of trimming and smoothing of wood. In general, processing of 1,000 kg of wood in the furniture industries will lead to waste generation of almost half (45 %), i.e. 450 kg of wood. Similarly, when processing 1,000 kg of wood in sawmill, the waste will amount to more than half (52 %), i.e. 520 kg wood.

5. Industrial Wastes

The food industry produces a large number of residues and by-products that can be used as biomass energy sources. These waste materials are generated from all sectors of the food industry with everything from meat production to confectionery producing waste that can be utilised as an energy source.

Solid wastes include peelings and scraps from fruit and vegetables, food that does not meet quality control standards, pulp and fibre from sugar and starch extraction, filter sludges and coffee grounds. These wastes are usually disposed of in landfill dumps.

Liquid wastes are generated by washing meat, fruit and vegetables, blanching fruit and vegetables, pre-cooking meats, poultry and fish, cleaning and processing operations as well as wine making.

These waste waters contain sugars, starches and other dissolved and solid organic matter. The potential exists for these industrial wastes to be anaerobically digested to produce biogas, or fermented to produce ethanol, and several commercial examples of waste-to-energy conversion already exist.

Pulp and paper industry is considered to be one of the highly polluting industries and consumes large amount of energy and water in various unit operations. The wastewater discharged by this industry is highly heterogeneous as it contains compounds from wood or other raw materials, processed chemicals as well as compound formed during processing.  Black liquor can be judiciously utilized for production of biogas using anaerobic UASB technology.

6. Municipal Solid Wastes and Sewage

Millions of tonnes of household waste are collected each year with the vast majority disposed of in open fields. The biomass resource in MSW comprises the putrescibles, paper and plastic and averages 80% of the total MSW collected. Municipal solid waste can be converted into energy by direct combustion, or by natural anaerobic digestion in the engineered landfill.

At the landfill sites, the gas produced, known as landfill gas or LFG, by the natural decomposition of MSW (approximately 50% methane and 50% carbon dioxide) is collected from the stored material and scrubbed and cleaned before feeding into internal combustion engines or gas turbines to generate heat and power. The organic fraction of MSW can be anaerobically stabilized in a high-rate digester to obtain biogas for electricity or steam generation.

Sewage is a source of biomass energy that is very similar to the other animal wastes. Energy can be extracted from sewage using anaerobic digestion to produce biogas. The sewage sludge that remains can be incinerated or undergo pyrolysis to produce more biogas.

The post Biomass as Renewable Energy Resource first appeared on BioEnergy Consult.

Power Today: What are the challenges that the Waste to Energy sector faces in the current scenario where there is a rejuvenated interest in clean energy? Do you think the buzz around solar and wind power has relegated the Waste to Energy sector to the back benches?

Salman Zafar: India’s experience with waste-to-energy has been lackluster until now. The progress of waste-to-energy sector in India is hampered by multiples issues including

1. poor quality of municipal waste,
2. high capital and O&M costs of waste-to-energy systems,
3. lack of indigenous technology,
4. lack of successful projects and failure of several ambitious projects,
5. lack of coordination between municipalities, state and central governments,
6. heavy reliance on government subsidies,
7. difficulties in obtaining long-term Power Purchase Agreements (PPAs) with state electricity boards (SEBs)
8. lukewarm response of banks and financial institutions and (9) weak supply chain.

Waste-to-energy is different from solar (or wind) as it essentially aims to reduce the colossal amount of solid wastes accumulating in cities and towns all over India. In addition to managing wastes, waste-to-energy has the added advantage of producing power which can be used to meet rapidly increasing energy requirements of urban India.

In my opinion, waste-to-energy sector has attracted renewed interest in the last couple of years due to Swachch Bharat Mission, though government’s heavy focus on solar power has impacted the development of waste-to-energy as well as biomass energy sectors.

Power Today: India has a Waste to Energy potential of 17,000 MW, of which only around 1,365 MW has been realised so far. How much growth do you expect in the sector?

Salman Zafar: As per Energy Statistics 2015 (refer to http://mospi.nic.in/Mospi_New/upload/Energy_stats_2015_26mar15.pdf), waste-to-energy potential in India is estimated to be 2,556 MW, of which approximately 150 MW (around 6%) has been harnessed till March 2016.

The progress of waste-to-energy sector in India is dependent on resolution of MSW supply chain issues, better understanding of waste management practices, lowering of technology costs and flexible financial model. For the next two years, I am anticipating an increase of around 75-100 MW of installed capacity across India.

Power Today: On the technological front, what kinds of advancements are happening in the sector?

Salman Zafar: Nowadays, advanced thermal technologies like MBT, thermal depolymerisation, gasification, pyrolysis and plasma gasification are hogging limelight, mainly due to better energy efficiency, high conversion rates and less emissions. Incineration is still the most popular waste-to-energy technology, though there are serious emission concerns in developing countries as many project developers try to cut down costs by going for less efficient air pollution control system.

Power Today: What according to you, is the general sentiment towards setting up of Waste to Energy plants? Do you get enough cooperation from municipal bodies, since setting up of plants involves land acquisition and capital expenditure?

Salman Zafar: MSW-to-energy projects, be it in India or any other developing country, is plagued by NIMBY (not-in-my-backyard) effect. The general attitude towards waste-to-energy is that of indifference resulting in lukewarm public participation and community engagement in such projects.

Lack of cooperation from municipalities is a major factor in sluggish growth of waste-to-energy sector in India. It has been observed that sometimes municipal officials connive with local politicians and ‘garbage mafia’ to create hurdles in waste collection and waste transport.

Supply of poor quality feedstock to waste-to-energy plants by municipal bodies has led to failure of several high-profile projects, such as 6 MW MSW-to-biogas project in Lucknow, which was shut down within a year of commissioning due to waste quality issues.

Power Today: Do you think that government policies are in tandem when it comes to enabling this segment? What policies need to be changed, evolved or adopted to boost this sector?

Salman Zafar: A successful waste management strategy demands an integrated approach where recycling and waste-to-energy are given due importance in government policies. Government should strive to setup a dedicated waste-to-energy research centre to develop a lost-cost and low-tech solution to harness clean energy from millions of tons of waste generated in India.

The government is planning many waste-to-energy projects in different cities in the coming years which may help in easing the waste situation to a certain extent. However, government policies should be inclined towards inclusive waste management, whereby the informal recycling community is not robbed of its livelihood due to waste-to-energy projects.

Government should also try to create favourable policies for establishment of decentralized waste-to-energy plants as big projects are a logistical nightmare and more prone to failure than small-to-medium scale venture.

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There are more than 1500 Waste-to-Energy plants (among 40 different countries) there is no pre-treatment of the MSW before it is combusted using a moving grate. The hot combustion gases are commonly used in boilers to create steam that can be utilized for electricity production. The excess energy that can’t be used for electricity can possibly be used for industrial purposes, such as desalination or district heating/cooling.

Benefits of Moving Grate Incineration

The moving grate incineration technology is lenient in that it doesn’t need prior MSW sorting or shredding and can accommodate large quantities and variations of MSW composition and calorific value. With over 100 years of operation experience, the moving grate incineration system has a long track record of operation for mixed MSW treatment. Between 2003 and 2020, it was reported that at least 200 moving grate incineration plants were built worldwide for MSW treatment. Currently, it is the main thermal treatment used for mixed MSW.

Compared to other thermal treatment technologies, the unit capacity and plant capacity of the moving grate incineration system is the highest, ranging from 10 to 920 tpd and 20 to 4,300 tpd. This system is able to operate 8,000 hours per year with one scheduled stop for inspection and maintenance of a duration of roughly one month.

Today, the moving grate incineration system is the only treatment type which has been proven to be capable of treating over 3,000 tpd of mixed MSW without requiring any pretreatment steps. Being composed of six lines of furnace, one of the world’s largest moving grate incineration plants has a capacity of 4,300 tpd and was installed in Singapore by Mitsubishi in 2000

Working Principle

Moving grate incineration requires that the grate be able to move the waste from the combustion chamber to allow for an effective and complete combustion. A single incineration plant is able to process thirty-five metric tons of waste per hour of treatment.

The MSW for a moving grate incinerator does not require pretreatment. For this reason, it is easier to process large variations and quantities. Most of these incineration plants have hydraulic feeders to feed as-received MSW to the combustion chamber (a moving grate that burns the material), a boiler to recover heat, an air pollution control system to clean toxins in the flus gas, and discharge units for the fly ash. The air or water-cooled moving grate is the central piece of the process and is made of special alloys that resist the high temperature and avoid erosion and corrosion.

The waste is first dried on the grate and then burnt at a high temperature (850 to 950 degrees C) accompanied with a supply of air. With a crane, the waste itself is emptied into an opening in the grate. The waste then moves towards the ash pit and it is then treated with water, cleaning the ash out. Air then flows through the waste, cooling the grate. Sometimes grates can also be cooled with water instead. Air gets blown through the boiler once more (but faster this time) to complete the burning of the flue gases to improve the mixing and excess of oxygen.

Suitability for Developing Nations

For lower income and developing countries with overflowing landfills, the moving grate incinerator seems suitable and efficient. Moving grate incineration is the most efficient technology for a large-scale mixed MSW treatment because it is the only thermal technology that has been able to treat over 3,000 tons of mixed MSW per day. It also seems to be considerably cheaper than conventional technologies.

Compared to other types of Waste-to-Energy technologies, this type of system also shows the highest ability to handle variation of MSW characteristics. As for the other incineration technologies like gasification and pyrolysis technologies, these are either limited in small-scale, limited in material for industrial/hazardous waste treatment, requiring preprocessing of mixed MSW before feeding, which make them not suitable for large-scale mixed MSW treatment.

Conclusion

For the reduction of significant waste volume, treatment using a moving grate incinerator with energy recovery is the most common waste-to-energy technology. The moving grate’s ability to treat significant volumes of waste efficiently, while not requiring pre-treatment or sorting is a major advantage that makes this suitable for developing countries.

This technology could provide many other benefits to such nations. Implementing moving grate incinerators is most suitable for developing nations because not only will it reduce waste volume, but it would also reduce the demand for landfills, and could recover energy for electricity.

References

 “A Rapidly Emerging WTE Technology: Circulating Fluid Bed Combustion”. Huang, Qunxing, Yong Chi1, and Nickolas J. Themelis. Proceedings of International Thermal Treatment Technologies (IT3), San Antonio, TX, October 2013. Columbia University. Available: http://www.seas.columbia.edu/earth/wtert/sofos/Rapid_Emerging_Tech_CFB.pdf accessed on 29 March 2016.

Kamuk, Bettina, and Jørgen Haukohl. ISWA Guidelines: Waste to Energy in Low and Middle Income Countries. Rep. International Solid Waste Association, 2013. Print.

“Municipal Solid Waste Management and Waste-to-Energy in the United States, China and Japan.” Themelis, Nickolas J., and Charles Mussche. 2^nd International Academic Symposium on Enhanced Landfill Mining, Houthalen and Helchteren, Belgium, 4-16 October 2013.  Enhanced Landfill Mining. Columbia University.

“Review of MSW Thermal Treatment Tecnologies.” Lai, K.C.K., I.M.C. Lo, and T.T.Z. Liu. Proceedings of the International Conference on Solid Waste 2011- Moving Towards Sustainable Resource Management, Hong Kong SAR, P.R. China, 2 – 6 May 2011. Hong Kong SAR, P.R. China. 2011. 317-321. Available: http://www.iswa.org/uploads/tx_iswaknowledgebase/10_Thermal_Technology.pdf. accessed on 14 April 2016.

UN-HABITAT, 2010. Collection of Municipal Solid Waste in Developing Countries. United Nations Human Settlements Programme (UN-HABITAT), Nairobi. Available:

http://www.eawag.ch/fileadmin/Domain1/Abteilungen/sandec/E-Learning/Moocs/Solid_Waste/W1/Collection_MSW_2010.pdf.

World Bank, 2012. What a Waste: A Global Review of Solid Waste Management. Urban Development Series Knowledge Papers.

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