Solid Waste Incineration

It’s common knowledge that the global accumulation of waste is a long-term environmental threat for future generations.  We haven’t found the perfect way to dispose of all of our waste. There are, however, existing technologies that allow us to manage our waste more effectively. One of the best examples of these is responsible solid waste incineration.

This article will discuss the process of incinerating solid waste, how solid waste incinerators work, and how today’s solid waste incineration processes can turn its byproducts into energy.

What is Waste Incineration?

Waste incineration is simply the burning of garbage. The incineration process, often described in the industry as thermal treatment, uses special incinerators that burn waste materials to ash, heat, and flue gas (i.e., gas exiting from a flue, such as a chimney, to the surrounding air). 

The ash, heat, and gas can be dissipated into the surrounding environment without energy or material recovery. This was especially true in older facilities in the US, and in other parts of the world without adequate environmental regulation. These older facilities run the risk of producing hazardous substances due to the unsatisfactory level of combustion process control and gas cleaning as well as untreated disposal.

Conversely, in more modern facilities, the resulting byproducts can be recovered and used for other purposes, recycling them in effect. For example, the heat produced from the burning process can be utilized for generating electricity and solid wastes, such as fly ash can be used as the material for making bricks, shingles, or tiles. 

Incinerating waste is widely practiced, and actually popular, in nations such as Singapore, the Netherlands, and Japan where there is a scarcity of land. Other European countries such as France, Germany, and Luxembourg also use incineration to dispose of municipal waste.

Waste Incineration in the United States

The first incinerator in the US was constructed in 1885 in Governor’s Island, New York. This and later incinerators were seen as an effective way of solving the nation’s trash problem and hundreds of facilities became operational by the end of the mid-20th century.

During the Industrial Age and until the late 1960s, there was virtually no concern about the negative environmental and health impact of the air and water pollution from these facilities. Since then, however, people have become more aware of being proactive in protecting the environment. 

In the US, the Clean Air Act of 1970 (CAA) established strict standards to limit pollution. To continue operating, incineration facilities needed to conform to strict standards that prohibit the uncontrolled burning of trash and that limited pollution.

This led to the closure of many facilities as well as the construction of new CA-compliant facilities in the 80s. 

The CAA requirements are regularly updated.  For example, new more stringent requirements for Maximum Achievable Control Technology (MACT) were adopted in the 1990s as the EPA recognized the hazards of mercury, dioxins, and other hazardous pollutants from incineration.

Waste to Energy

A more recent development is facilities that recover the heat from incineration and use that energy to generate electricity.  These are referred to as “waste to energy” facilities or WTE in short. The terminology refers to the energy recovery process that makes some modern incinerators an electricity-generating utility as well as a waste disposal service.

Benefits of Waste Incineration

Proper and responsible waste incineration provides various benefits:

Some progressive countries use modern waste treatment and incineration facilities to convert heat used in the burning of trash to electric power. The governments of Sweden and Denmark have turned many of their incinerators into energy generators, making them world experts in recycling energy. Waste incineration produced 13.7% of Sweden’s domestic heat consumption and 4.8% of electrical consumption in Denmark. 

The incinerator bottom ash can be used as an aggregate in creating lightweight blocks, pavement concrete, bulk fill, and more. Environment conscious entities are using novel technologies to create bricks, tiles, shingles, and other construction materials from ash.

Incineration can decrease the solid mass of the original waste, which is already compacted by garbage trucks, to a further 80 to 85%. It can also reduce the volume of trash up to 95%. How compacted the mass depends on the composition of the garbage materials.

At present, there are 72 incinerators operating in the US handling a percentage of the nation’s garbage, with the rest of the garbage being composted, recycled, or disposed of in landfills. The reduction of solid waste by incineration drastically reduces the amount of trash that ends up in a landfill. 

Incineration can also be used to treat hazardous waste (such as materials contaminated with hazardous chemicals)  or medical waste (such as hospital waste contaminated with blood or other potentially infectious materials).  The high heat of incineration can destroy these hazards.  Hazardous and medical wastes can only go to special incinerators that are permitted to treat these types of wastes.

Waste Incineration Process

All wastes that are intended to be incinerated undergo a process called “mass burn.” Each facility has different ways to do a mass burn, but each follows a general process outlined below:

Waste sorting and shredding

The waste is first sorted out, both mechanically and manually. Machines and personnel remove oversized items, recyclable items, and metals. The remaining trash is then shredded.

Waste drying and batching

In some facilities, the waste material is processed or dried so that only around 30% moisture remains. After this, the waste is divided into more manageable batches. The volume of each batch is carefully computed and monitored so it can be burned at the lowest cost and in the shortest time possible.

Combustion

The remaining garbage undergoes the combustion processes. For specifics on how waste is burned, check out the earlier section titled “Parts of an incinerator”

Energy recovery

The heat from the combustion process is used to generate steam. The steam is then used to provide energy to run generators that produce electrical power.

Environmental control

The cooled gas is subjected to thorough cleaning in the facility’s flue gas cleaning system. Here, it is treated with filters, precipitators, and scrubbers to ensure that most pollutants are removed before discharge.

Environmental release

Finally, the treated gas is discharged to the atmosphere. Ideally, the gas coming out from the chimney should be transparent with no visible smoke since the discharged gas should be particle-free.

Residuals, or the solids that remain after combusting, are dumped in an ash pit ready to be disposed of in a landfill.

Parts of a Solid Waste Incinerator

While many facilities may differ in processes and technologies, waste incinerators usually have standard parts. 

The most common type of waste incinerators is called a moving grate incinerator, often referred to as a Municipal Solid Waste Incinerator (MSWI). Rubbish is dumped into a moving grate that goes through the different chambers of an incinerator. The constantly moving grate enables a fast, efficient, and complete movement and processing of waste products. A properly maintained moving grate incinerator can handle 35 metric tons of waste per hour at 8,000 hours per year. 

Understanding how a typical moving grate incinerator works is best illustrated by understanding how each of its major parts works:

Waste Crane

A waste crane picks up massive loads of garbage from a sorted mound.

Throat

The throat is a large long tunnel that leads to the primary combustion chamber.

Primary Combustion Chamber

Waste from the throat goes to the main combustion chamber where the material is burned. Most often, this chamber is already hot thanks to the high ambient temperature that is constantly controlled and retained.

Secondary Chamber

The secondary chamber is often called the “afterburner.” Facilities in Europe, Australia, Canada, and the US are required by law to have an afterburner. This chamber helps reduce or prevent harmful particulates from forming by burning them off.

Many countries have laws that require all flue gas remain in the secondary chamber for at least 2 seconds at a temperature of 850 degrees Celsius to break down toxic organic substances.

Superheater

Using superheaters, heat from the flue gasses can be used to convert water to steam. The superheated steam can then be used to drive turbines to generate electric power in WTE facilities. The flue gas is now at 200 degrees Celsius at this point.

Flue Gas Cleaning System

Before exiting the facility, the flue gas goes through the cleaning system to purge acids, heavy metals, and other toxic particulates.

Flue Stack

Once the flue gas is treated, it exists through the flue stack, commonly called a chimney. Laws require a stack height of at least 3 meters for localized incinerators. Bigger ones, however, have multi-story chimneys, especially those that handle the massive trash produced by large cities. Also, chimneys may be built higher or lower than recommended due to various atmospheric conditions.

Burners

The flame coming from the burners ignites the garbage. The majority of the incinerators are equipped with low nitrous oxide burners or modulated gas flow burners. The intensity of the flames is carefully controlled.

Fuel tanks

Fuel tanks are used to store fuel. Fuel tanks must be carefully insulated for safety.

Ash pit

After incineration, the remnant ash is then collected in an ash pit for disposal. Some entities purchase the ash for their own use.

Incineration Waste Disposal

Waste from solid waste incineration includes flue gas, heat, and ash.

Harmful particles and substances are filtered through the flue gas cleaning system. At a prescribed time, the filters and scrubbers of the systems are replaced or cleaned. Facility operators always keep a close watch of the system. That’s because clogged systems make the gas treatment less efficient. This material may be combined with ash for recycling or disposal or sent to landfill. 

The heat from combustion converts water to steam, which is then sent into turbines to produce electrical power. This electricity is used to power the other electrical systems of the facility. In some countries in Europe, excess electricity is released into the grid to power nearby communities.

Proper disposal of waste incineration ash constitutes its own special process. The ash is run through a baghouse filtering system that captures particulates. Minute amounts of ash that escape the system, called fly ash particles, are captured via funnels called hoppers.

All resulting ash is dumped into an ash pit. Water is poured on the ash pit to prevent ash dust from escaping. The moist residue is then transported into a building where it is loaded to leak-proof disposal trucks.

Finally, the trucks transport the remaining ash to a designated landfill. That landfill must be certified and designed to prevent groundwater contamination; ash particles are so tiny that it might seep into the groundwater beneath the bedrock.

Alternatively, incinerator ash may be recycled to manufacture, bricks, tile, or other items.

Conclusion

As you can see, there is a lot more to solid waste incineration than simply burning garbage. There are complex processes involved. Whether a community resorts to waste incineration or dumping their garbage in a landfill depends on a variety of factors including resources, amount of land, and eco-vulnerabilities of that community.

When done and managed right, waste incineration is a cleaner, more efficient, and one of the most efficient modern waste management systems. 

Still, whatever waste management process is used, in the end, producing less waste is the best and most effective way to reduce the environmental, health, and social impacts of garbage.

A Quick Guide for Selection and Use of Approved Covid-19/Coronavirus Disinfectants

As we discussed previously, routine or periodic cleaning and disinfection are an important part of an overall workplace Coronavirus safety program, along with hand washing, social distancing and source control measures such as mask use. Additional cleaning and disinfection can be considered in work areas if one or more workers contract Coronavirus.

According to guidelines from the Centers for Disease Control (CDC) at https://www.cdc.gov/coronavirus/2019-ncov/community/reopen-guidance.html, the first step to disinfect a surface is cleaning with soap and water to remove dirt and dust and reduce the amount of virus on the surface followed by application of application of approved disinfectant.

No matter how they are applied, Covid disinfection requires use of approved disinfectants, including 0.1% sodium hypochlorite (bleach) or 70% alcohol (Ethanol or Isopropyl Alcohol)

To prepare a 0.1% bleach solution, mix:

Make sure to check the expiration date on your bleach container. Also, the bleach solution degrades over time so ACTenviro recommends making new solution every 24 hours as needed. Finally, pay attention to safety. Bleach is corrosive so wear appropriate PPE, including gloves, eye/face protection, mix outsider or in areas that have good ventilation, have spill supplies available and never mix bleach with ammonia or anything other than water!

For surfaces or locations where bleach is not suitable, 70% alcohol (ethanol or isopropyl alcohol) may be used, although these flammable liquids have their own set of safety issues.

The EPA also maintains a list of disinfectants that are anticipated to be effective against Covid/Coronavirus – EPA List N – Approved for “Emerging Viral Pathogens”

Specific products are shown on List N, however other products with the same active ingredient (based on the product’s EPA registration number) can also be used.

Keep in mind though that Manufacturer’s instructions must be followed and use of any of these materials should be reviewed to determine if additional PPE (including respiratory protection) is required.

Still have questions? See our previous post that looked at cleaning and disinfection requirements or stay tuned for our next post where we will talk about at validation and how to make sure that your cleaning and decontamination process is effective.

Medical Waste Disposal Guide

Overview

Medical waste can come from multiple facilities, especially in the health sector. Since it contains harmful and infectious components, it is certainly one of the more challenging types of waste to dispose of. That is why you can use this medical waste disposal guide, to stay on top of medical waste disposal management, and not be hit by HIPAA regulations or lawsuits.

Medical Waste

Before we discuss how to dispose of medical waste properly, let us first define what it is, and the types of medical waste that hospitals, pharmacies, dental clinics, doctor’s offices, etc. dispose of daily. Knowing what medical waste is and how to categorize it accordingly is one of the first few crucial steps to its proper disposal.

What is Medical Waste?

Medical waste is a type of waste produced from the medical or science sector. According to a 2018 study, the US alone produces more than 5.9 million tons of medical waste every year, and that only constitutes the medical waste from hospitals. That does not yet include medical waste produced from dental practices, home care, vets, and pharmacies.

There are various kinds of waste being produced each day. So, how is this segregated? Waste only becomes classified as “medical waste” when it contains or is from at least one of the following:

Types of Medical Waste

Where to Dispose of Medical Waste

Now that you have a clearer picture of what medical waste is, let us now move on to where it should be disposed of.

On-Premises vs Off-Premises

Should medical wastes be taken care of within the health facility itself or should it be dumped off at other facilities? The answer to that question is largely based on what the hospital can afford. Usually, it is only larger hospitals that feature state-of-the-art waste disposal equipment to take care of their medical wastes. That is because it is expensive to buy and maintain all the equipment that a hospital needs to get rid of all its waste properly.

So, for the smaller medical facilities, they typically utilize waste transport services. These services can help them transport their waste to a licensed facility that can properly destroy their waste. Usually, they come in the form of truck services.

Another type of transport service is the Postal Service. Small clinics, hospitals, centers, and nursing homes can safely use mail or boxes to transport their waste to facilities that can permanently get rid of the waste. This is said to be the most affordable way that a smaller health center can manage their medical waste.

However, these cover most of the types of medical waste except one, which are sharps and needles. They require a more delicate approach when it comes to getting rid of them. That is because if handled wrong, they are health risks to not only health workers, but also to the general public. We will talk about that in the next section.

Sharps/Needles Disposal

As stated earlier, disposal of sharps and needles should be handled with utmost care and importance. Since, they can pierce the skin, health workers can accidentally prick themselves from mishandling these “dirty” needles, which can potentially infect them with serious diseases. Aside from medical staff, pretty much anyone who comes in contact with improperly disposed sharps and needles can fall victim to this type of injury. Fair warning is advised when disposing of sharps and needles. 

Here is a guide to the process of correctly disposing of these high-risk medical waste:

Usually, sharps and needles come in a container where you can dispose of used needles. Take note that these containers are puncture-resistant, providing that extra layer of protection. Plus, these containers are also labeled to make all people aware that what is inside is extremely dangerous.

When you the container is already piling up, note that it should only be filled to about ¾ full, and not all the way to the brim of the container. Once that is done, you need to follow these next few steps, so that you can be sure of what to do:

  1. Seal the container tightly.
  2. Put the container on the red liner (the box that the container was shipped in).
  3. There should be a twist and tie attachment on the cover, tie it securely.
  4. Place the red bag into its postage storage box.
  5. Follow the box’s instructions on how to close it.
  6. Write down your return address on the label of the box.
  7. Now that you have sealed the box securely, you can now give it to your local mail carrier, so that they can ship it to the right medical waste facility.

That is the gist of how to stay on top of handling these risky types of medical waste. Again, use caution when it comes to disposing of these sharps and needles, as they can potentially contain life-threatening diseases, such as Hepatitis or the Human Immunodeficiency Virus or HIV.

Quick But Important Tips/Reminders

Other Medical Waste Disposal

So, a quick recap; we have already discussed medical waste, the disposal of medical waste, and how to handle the disposal of sharps and needles. Now, let us discuss the other ways that you can dispose of your medical waste. There are quite a few of them; mainly:

Autoclaving

Basically, the autoclaving method is sterilization by the use of steam. This process renders the hazardous waste as non-infectious, making it possible to throw away in solid waste landfills. They can also be incinerated afterwards.

Biological

Before we discuss what this method does, you should note that this process is not yet widely accepted as a proper way to dispose of waste. This is still under its development phase. Having said that, the biological method enables the use of enzymes to counterbalance the harmful organisms in those medical waste.

Chemical

This type of waste disposal method centers around taking care of chemical-related waste. Simply put, reactive chemicals are applied onto these chemical waste to neutralize it, and make it inactive.

Incineration

Did you know that incineration was used to destroy more than 90% of medical waste before August of 1997? Well because in that year, the US Environmental Protection Agency or US EPA disseminated regulations on emission standards. That is due to the growing concern of the quality of the air, which may affect the overall health of a person. This led to other means of disposal. However, for pathological waste, this is still the only method to properly destroy it.

Microwaving

This method also makes medical waste non-hazardous. Thus, making it safe to be thrown away to landfills. As the name of this method implies, healthcare waste is microwaved using powerful equipment to destroy harmful bacteria and viruses.

Disposal of Medical Waste - Best Practices

The medical industry is currently the third biggest industry in the US in 2020, according to a study by IBISWorld. That could mean multiple things, but it also means that there is a ton of waste produced by the health sector every month. So, what would be the first thing to do when it comes to this?

Firstly, healthcare facilities must be registered with the government as a“Medical Waste Generator”. This step is quite crucial as all medical facilities are regulated by state law and must adhere to it. The next step is to always segregate waste, which is usually required by each state.

On top of that, you can also observe a few guidelines below, so that you can always stay on top of your medical waste disposal practice:

FAQs:

Upon the expiry of the 1988 Medical Waste Tracking Act in 1991, the EPA has not had any authority over regulation of medical waste, specifically. These are now mostly regulated by environmental and health dpeartments per state. It's best to contact your local agencies for assistance in these maters. 

It's also good to that that federal agencies such as (but not limited to the) Centers for Disease Control (CDC), Occupational Safety and Health Administration (OSHA), U.S. Food and Drug Administration (FDA) have their own regulations covering medical waste disposal.

Normally, you can visit your local hospital, clinic, or doctor’s office, since they can help you dispose of it, especially sharp waste. It is vital that you do not throw away sharps and needles in the recyclable bin as these cannot be recycled anymore.

A few examples of medical waste include culture dishes, glassware, bandages, gloves, tissue, and discarded sharps such as needles and scalpels.

Conclusion

Disposing of medical waste is easier said than done. That is why it is vital that you stick to the implemented laws and guidelines to help you dispose of it in the right way. Doing so in an unseemly manner can lead to harmful effects and could lead to a public safety hazard. So, it is always best to stay extra careful, for your sake and those around you – whether you work in the health care sector or not.