Are Pyrolysis Plants Harmful?

Before we discuss more on pyrolysis and its impact on the environment, among other aspects, let’s go through the following!

What Is Pyrolysis?

As the name implies, there is heat involved (I.e. Pyro means fire in Greek).

Pyrolysis is the process of turning organic matter into several different end materials that include tar, syngas, ash, and charcoal (also known as biochar or char) by burning them in a controlled anaerobic environment, i.e. no oxygen present (Environmental Materials and Waste, 2016).

Extremely high temperatures (300°C to 800°C) are necessary for this process. Especially if you want less liquids (tar) and more gasses as your end products. However, lower temperatures will also result in more char (Erdogan, 2020).

 Note: If the input (known as feedstock) for the plant is plastics, there will be hardly any char or ash produced (Rollinson, 2018).

Limitations Of Pyrolysis Plants

Energy Use (And Loss)

As you can imagine, getting to such high temperatures takes a lot of energy. And where the energy is derived from is another matter. Also, there will be inevitable energy loss (I.e. heat).

Note: Based on the Primary Energy Supply statistic report (1978 to 2019) by Malaysia Energy Information Hub, the main energy source in Malayisa is natural gas, followed by crude oil and coal and coke (MEIH, n.d.). So we’re still relying heavily on fossil fuels to produce electricity.

 In fact (and according to a 2019 article by Conservation Law Foundation, USA), pyrolysis plants can use up to ~87 times more energy than the energy they can store in the end products (Budris, 2019). We are not even talking about the initial build up and what it takes to operate the plants (I.e. maintain the right environment for the process).

The same article writes that other countries (Germany, Scotland, Australia) have already closed down pyrolysis plants after ~3 years due to operational issues, non compliance with pollution limits, or a net energy loss.

However based on a 2020 article by Melissa Leung (Canada), countries like Canada have been able to implement pyrolysis plants successfully with minimal impact to the environment (Leung, 2020).

Feedstock Restriction

A single pyrolysis plant cannot handle different types of waste:-

Because of the specialized equipment and process (e.g., temperature, pressure, or duration, etc), the plant may only take tires, biomass or plastic as feedstock (Leung, 2020).

Is It Worth It (How Useful Are The End Products)?

Environmental Aspect

 Syngas

The problem with this process is that several pollutants can be released into the environment if they are not properly treated first:

Hydrogen sulfide (H2S), Sulphur oxides (SOx), Nitrogen oxides (NOx), Ammonia (NH3) 

(Ghosh et. al., 2020)

Ideally, a plant should reuse (I.e. burn) these syngases to fuel the pyrolysis process and cut operating costs. An additional benefit of burning the syngases at the plant itself is to remove particles from the gases before they can threaten human health and the environment (Leung, 2020).

By-products like ash (loaded with heavy metals and dioxins), can find their way into waterways too (Budris, 2019).

There may be contamination to crops and plants, which was a concern brought up by scientists over the set up of a pyrolysis plant in New Zealand (Gill, 2021).

Biofuel 

Pyrolytic oil from pyrolysis requires decontamination (itself an extensive and expensive process) before it can be used as biofuel; with a similar but inferior performance to diesel (Recycling Magazine, 2020).

And afterwards, you still need to burn them. Which will release the carbon back into the atmosphere (Rollinson, 2018).

One would argue that with all the wasted energy to turn plastic waste into the end products, you might as well be burning the plastic directly then. 

Health Risks

 There are different types of pyrolysis techniques that cater to different feedstock.

If we consider just a plant that does catalytic pyrolysis of waste plastics, there is a possible risk for VOC (and other hazardous chemicals) inhalation for those that stay near the plant (Paladino & Moranda, 2021)

Not to mention the risk to those who work at the plant. Without proper waste and contamination management, they can be exposed to the hazardous chemicals (Leung, 2020).

Taking The Easy Way Out

If pyrolysis were to become the main way we deal with our trash, what would happen to the existing recycling facilities?

Burning mixed trash (I.e. with food waste) is a potential loss when they could be composted too (Budris, 2019).

And with pyrolysis plants around to “get rid” of the existing plastic, it’s a convenient excuse to produce even more plastic (Recycling Magazine, 2020).

Risk Of Explosion

If a lot of oxygen were to enter a plant without the right safety measures (e.g., fire detection) in place, there is the possibility of an explosion.

 Furthermore, if the char or biochar is not stored or transported properly, they could easily catch fire (Leung, 2020).

Conclusion

In a nutshell, there are benefits to having pyrolysis plants – mainly to take something unwanted (domestic refuse including more complex plastics and turn it into something useful (e.g., biofuel) (Loughborough University, 2019).

“ …more than 75% of the initial weight can be obtained as pyrolytic oil” according to an article by Erdogan (2020).

But the plants must meet stringent requirements (e.g., how they store the solid, gaseous, and liquid by products, safety measures in case of an explosion, etc).

And be able to recycle their gaseous by-products (and at high temperatures) in order to be self-sustainable. Furthermore, the pyrolysis process must be as efficient as possible (Loughborough University, 2019). Otherwise, the benefits will be outweighed by the disadvantages!

What do you think? 

Is it better just to incinerate trash rather than relying on pyrolysis plants? Are there better ways to solve the problem of Malaysia’s overflowing landfills? Let us know your perspective!

Article by Travel with Sun (2022)

Edited by KC