Turning Waste into a Blessing
Tauhid Nur Azhar
Before attending Friday prayer at a mall I often visit, I took a stroll along the Sky Walk on a legendary street where the mall is located. The pedestrian bridge, which has been vacant for a while due to various reasons, including the pandemic and changes in policy, is starting to come back to life.
It’s understandable that policies and public policies can be difficult to implement consistently, especially when there are still sectoral and personal interests at play. However, it’s not ideal if the inactivity of public facilities or the need for additional funding is a result.
Perhaps the spirit that should be emphasized is optimization and efficiency, so that the direction of development and growth can move forward significantly.
But, I apologize, my enthusiasm was actually sparked when I enjoyed walking and breathing in the fresh air on the pedestrian bridge. Along with a few foreign tourists who seemed to be interested in the concept of walking near the tall trees like Mahoni, which produce a lot of oxygen, I explored the interesting corners and even sat in the shade to finish writing a piece that I would post before the Friday prayer.
It was when I was sitting that my gaze fell upon several piles of plastic waste in one of the planters. Upon closer inspection, I saw that there were also a lot of waste from food and drink packaging and cigarette wrappers scattered around.
Despite the fact that there was a clear sign indicating a temporary waste bin made of black plastic as an anticipation of visitors who might object to throwing their trash in the permanent waste bin, which was actually located a bit far away.
As a result, I took the initiative to collect the waste and put it in the designated bin. Perhaps it’s just a small act, but it’s something that can be done when enforcement of rules requires firmness from the authorities who have the basis of the rules as a guideline for their actions.
Almost all the waste I collected was made of plastic. Plastic is a technological discovery that has made significant contributions to the construction of civilization. It has brought many conveniences and benefits, as well as practicality, but on the other hand, it also brings unwanted consequences.
According to data from the Indonesian Plastic Industry Association (INAPLAS) and the Central Statistics Agency (BPS), Indonesia produces 64 million tons of plastic waste per year. Of this amount, 85,000 tons are plastic bags that are discarded into the environment.
In 2022, Indonesia’s plastic waste production reached 12.54 million tons, an increase from previous years.
Indonesia is one of the largest producers of plastic waste in the world and is the second-largest contributor to marine waste. Of the 3.2 million tons of unmanaged plastic waste produced in Indonesia every year, 1.29 million tons end up in the ocean.
Plastic was first developed around 1855 and was known as Parkesine, named after its inventor, Alexander Parkes, an English chemist. Parkesine is a synthetic plastic made from cellulose, a substance found in plants, which can be shaped when heated. It was one of the first synthetic plastics in the world.
In 1907, Bakelite was discovered by a researcher named Leo Baekeland. Leo was a Belgian chemist who lived and worked in America. Bakelite is the first truly versatile and heat-resistant synthetic plastic, making it very popular for various applications, including electrical appliances and household items.
By the 1930s, synthetic polymers, including polystyrene and polyethylene, were developed. This marked the beginning of mass production of plastics.
In the 1950s, plastics such as polypropylene and polyvinyl chloride (PVC) were introduced. These plastics provided better flexibility and wider applications, including the automotive and construction industries.
Today, several types of plastics derived from synthetic processes have become an integral part of our daily lives, from food packaging to carrying bags or food containers known as kantong keresek.
Some common types of plastics used in daily life include:
Polyethylene (PE): used for plastic bags, bottles, and toys. It comes in various types, such as HDPE (High-Density Polyethylene) and LDPE (Low-Density Polyethylene).
Polypropylene (PP): widely used for food containers, laboratory equipment, and automotive parts.
Polyvinyl Chloride (PVC): widely used for pipes, cable insulation, and other construction materials.
Polystyrene (PS): used for packaging, disposable tableware, and building insulation.
Polyethylene Terephthalate (PET): used for beverage bottles, food containers, and textile fibers.
There is also Acrylonitrile Butadiene Styrene (ABS), widely used for toys like LEGO, household appliances, and automotive parts.
According to data from various institutions responsible for waste management and control, both nationally and globally, it is found that only about 7.5% of waste in Indonesia (in general, not just plastic) can be processed and has economic value.
However, this situation is a challenge and an opportunity that can be utilized as part of a continuous innovation process, right?
Recently, there has been a lot of discussion on social media about the validity of the method of processing plastic waste into fuel through pyrolysis. There are academic skepticism, particularly about the results being overrated, as well as various questions about the technical implementation, how much energy is consumed in the process? Is the economic scale proposed viable? Can it be implemented on a large scale? And so on.
It’s all very good and we hope it will continue to spark development, both academically, which can provide scientific foundations, as well as economically, which is expected to give birth to another line of environmental services that are attractive to investment schemes that usually require proof of concept from systems and market readiness to accept them.
One of the methods that have recently attracted the attention of researchers in waste management and renewable energy is the technique of pyrolysis.
Pyrolysis is a thermal decomposition process of organic materials without the presence of oxygen or with a very small amount of oxygen. In the context of plastic waste, pyrolysis is used to convert plastic into liquid, gas, and solid fuels.
The process of pyrolysis for managing plastic waste to be converted into fuel itself can be done scientifically with the following steps:
- Collection and sorting: Plastics are collected and sorted based on their type, as each type of plastic has different pyrolysis properties.
- Cleaning and crushing: Plastics are cleaned to remove impurities and unwanted materials. After that, plastics are crushed into smaller pieces to facilitate the pyrolysis process.
- Heating (Pyrolysis Reactor): Crushed plastics are then fed into the pyrolysis reactor. The reactor is then heated to a certain temperature without the presence of oxygen.
There are certain requirements and qualifications for the type of plastic waste that can be processed through pyrolysis. The following are types of plastics that can be processed through pyrolysis:
- Polyethylene (PE): Including high-density polyethylene (HDPE) and low-density polyethylene (LDPE).
- Polypropylene (PP): Plastics commonly used in food packaging and other products.
- Polystyrene (PS): Often found in foam form, such as styrofoam.
- Polyethylene terephthalate (PET): Used for beverage bottles.
- Polyvinyl chloride (PVC): Although it can be pyrolyzed, PVC produces corrosive hydrochloric acid, requiring special equipment.
The temperature required for the pyrolysis of plastics to produce fuel (related to the energy consumed during the pyrolysis process) is:
- LDPE, HDPE, PP: 300–500°C
- PS: 400–600°C
- PET: 500–600°C
- PVC: 300–600°C (with special equipment to handle HCl)
In the process of plastic pyrolysis, the main chemical reaction that occurs is the breaking of polymer bonds into smaller molecules, such as monomers, dimers, and trimers. These reactions include:
- Depolymerization: The breaking of polymer chains into smaller molecules (C2H4)n.
- Radical Reactions: Plastic molecules are broken down into free radicals that then react further to form the final product.
- Hydrogen Formation Reactions: Some plastics will produce hydrogen gas as one of the products.
The products of plastic pyrolysis consist of three main fractions:
- Liquid Fuel: Such as gasoline, diesel, and kerosene that can be used as an alternative fuel. The liquid is a mixture of hydrocarbons with different chain lengths (CnH{2n+2}).
- Pyrolysis Gas: The gas produced consists of light hydrocarbons such as methane, ethane, propane, butane, and hydrogen. (CH4, C2H6, C3H8, C4H10, H2)
- Solid Residue: Mainly consisting of solid carbon or char that can be used as a solid fuel or for other applications such as water purification.
With the increasing stability of the technique and the continuous innovation from various laboratory research, it is hoped that there will be continuous improvements in the technique and method of processing plastic waste. Until what was once waste can be transformed into a product that can produce many blessings.
Of course, ongoing education and strengthening of law enforcement in the context of personal, household, and industrial waste management are still necessary to be consistently implemented. Awareness in maintaining the sustainability of environmental functions is our shared responsibility, isn’t it?
