Get to know the Landfill Method in the Waste Management System

Definition of Landfill – Based on Law Number 18 of 2008 concerning Waste Management, the final processing site (TPA) or landfill is the last place for waste management. TPA is a place where trash is isolated safely so as not to cause disturbance to the surrounding environment. This is why it is necessary to provide proper facilities and treatment so that security can be achieved properly.

Table of Contents

Based on data from the 2007 Indonesian Environmental Status (SLHI) regarding the condition of landfills in Indonesia, most of the landfills in Indonesia are open dumping or open landfill sites, giving rise to environmental pollution problems. Data states that 90% of landfills are operated by open dumping and only 9% are operated by controlled landfills and sanitary landfills . Improving the condition of the TPA is very much needed in city-scale waste management.

Definition of Landfills

TPA or landfill is a place to dispose of garbage and other waste materials. This site is designed to minimize the impact of waste on human health and the environment. Quoting an explanation on the National Geographic website, the TPA is covered with layers of clay and thin plastic, then backfilled with several meters of soil so that plants can grow on it.

Some landfills will decompose over time, even if they are designed only to contain waste. The decomposition process in the landfill will produce methane, which is a dangerous and flammable gas. Several studies have found that methane has a negative impact on the environment and health.

TPA is an important subsystem in waste management. TPA is the place where the process of
collection, transportation, sorting, recycling and disposal ends. This phase can use a variety of methods, ranging from a simple level to a high-tech level (Wahyono, 2012). TPA is very much needed. If TPA does not exist, waste will accumulate in various places and cause various environmental pollution.

According to the Indonesian National Standard (SNI) 19-2454-2000, there are several methods of final disposal of waste, namely:

1. Open Dumping

This method is considered the simplest final disposal method because there is no special treatment for waste, and the operation is very easy. Garbage that comes in is just piled up without any further processing. This can result in environmental pollution, such as air pollution due to odors, water pollution due to leachate , aesthetics, and others.

2. Controlled Landfills

In contrast to the open dumping method , the operations used in this method are slightly more complicated and the operational costs are also quite large. This waste management method includes stockpiling, leveling, and compaction. After the capacity of the land used to accommodate waste is full, the waste pile is covered with a layer of cover for a predetermined period of time.

3. Sanitary Landfill

This method is the most complicated method compared to the previous two methods. The costs used are also relatively high, but have a positive impact on the people living around the TPA. In this method, waste is piled up to a certain thickness, compacted, covered with soil, and compacted again. Furthermore, trash can be spread again on the top layer of soil, and so on.

4. Landfill Mining

Land disposal or disposal of waste into the ground is the most common method found in waste management. This method of removing waste into the ground is carried out by backfilling or landfilling known as landfilling , which was first applied to municipal waste (Damanhuri, 2010 ) .

At this time, landfill mining is a new strategy that can be used to recover resources and materials that can be reused. The enhanced landfill mining (ELFM) concept is an updated landfill mining concept , which means extended landfill mining .

The ELFM concept can be defined as safe and integrated conditioning, excavation and valorization of stockpiled waste, which can be used as waste to material or waste to energy by using innovative technology with due regard to social and environmental criteria (Wahyono, 2012 ).

Gas Formation in Landfills

Landfill gas is produced from the decomposition process of waste buried in landfills by the activity of microorganisms. The decomposition process takes place anaerobically through several stages, namely:

Hydrolysis , namely the breakdown of long carbon chains into simpler carbon chains in the waste degradation process by microorganisms.
Acidogenesis , namely compounds with shorter carbon chains are converted into organic acids due to the activity of acidogen microorganisms .
Methanogenesis , namely the degradation stage that produces methane gas and other gases due to the activity of methane-forming microorganisms (CH ₄ ).

In general, waste decomposition in landfills takes place anaerobically. Anerobic decomposition process of waste will form gas. The composition of the gas produced is strongly influenced by the microorganisms that decompose the waste and in general the gas produced is closely related to the anerobic decomposition phases of the waste.

The initial stage of waste decomposition is called the aerobic phase, which occurs at the beginning of landfill waste and oxygen is still in the waste pile. The second and third phases are called the acid transition phase which is closely related to the process of acidogenesis and begins to form carbon dioxide gas (CO2 ₎ . Furthermore, gas begins to form at the stage of metagonesis, namely the fourth phase which produces CH ₄ and CO ₂ . The fifth phase is the ripening phase when waste has become a more stable product.

The characteristics of the gas produced from the waste decomposition process is determined by the characteristics of the waste being stockpiled. The largest composition of the gas produced is methane CH ₄ and CO ₂ . These gases can be used as a very potential source of energy and if not managed properly will also cause pollution.

CH ₄ and CO ₂ are gases that contribute to greenhouse gases (GHG). Based on research data that has been widely carried out, CH ₄ has a power 21 times stronger in storing heat compared to CO ₂ gas . This condition causes waste management in landfills to be one of the contributors to global warming.

Based on SLHI data for 2007, it is known that waste management in landfills that do not manage gas properly contributes 3% to the effect of global warming in Indonesia. Related to this, the National Action Plan (RAN) on Climate Change on a national scale includes efforts to manage gas in landfills as one of the mitigation efforts to reduce global warming. Methane gas produced must be managed properly and can be used as an energy source.

Theoretically based on this chemical reaction, CH ₄ and CO ₂ are the most dominant gases produced from the anerobic waste degradation process. The amount or production of gas produced depends on several factors, namely:

Elements of waste formation such as carbon, hydrogen, nitrogen, and oxygen obtained from waste characteristic analysis, namely ultimate analysis .
The speed of waste degradation is divided into waste that decomposes quickly and slowly decomposes. The time for decomposition of easily decomposed organic matter is 5 years, while the time for decomposition of slowly decomposing organic matter is 15 years.

When gas begins to be produced, the pressure inside the landfill will increase, thus allowing gas movement within the landfill . Gas movement can occur vertically and horizontally if the pressure outside (barometric) is less than the pressure inside. The gas will tend to move vertically and escape, whereas if the outside pressure is greater, the gas tends to stay in the landfill until it reaches pressure balance.

Gas movement is very difficult to predict. Based on several studies that have been conducted, it is known that the movement of methane gas in a horizontal direction can reach a distance of more than 1,500 feet. The gas produced during the decomposition process must not just escape into the air. This is because the methane gas produced when in contact with air > 5% will cause an explosion, so that control and monitoring of landfill gas is necessary.

Gas control in general can be done by burning gas or using it as an energy source, especially for methane gas which can be used as a very potential energy source. In general, gas control systems can be distinguished between active and passive.

Leachate Formation

Waste that is disposed of in landfills undergoes several physical, chemical and biological changes. Simultaneously, these wastes will produce a liquid called leachate . Leachate is a liquid that is produced from exposure to rainwater in landfills. This liquid is very dangerous and toxic because it contains high concentrations of organic compounds and inorganic compounds, which are formed in landfills due to rainwater that enters them. In addition, the liquid may also contain metal elements, namely zinc (Zn) and mercury (Hg).

Leachate in everyday life can be analogous to brewing tea which carries suspended and dissolved matter from waste degradation products. The liquid can be processed into biogas and liquid fertilizer. This is because the water contains various kinds of organic matter, namely nitrates and minerals.

Impact of the Landfill Method

At first glance, the landfill method is relatively easy to implement and can accommodate large amounts of waste. However, this assumption is not correct because landfills can cause problems related to health and the environment. The main problem that often arises is the smell and contamination of leachate. In addition, methane gas from landfills that is not utilized properly will cause a global warming effect, and can even explode if it is compressed in the ground. This is why it is necessary to have a good leachate and biogas treatment unit in a landfill system .

Sembiring and Muntalif added that another impact caused by these liquids is contamination of surface water and groundwater in the vicinity, because generally these liquids contain BOD values of 2,000–30,000 mg/L and COD of 3,000–60,000 mg/L. Several cases of leachate pollution in Indonesia that were successfully recorded by Usman and Santosa are dozens of shrimp ponds that failed to harvest in the Cilincing area, North Jakarta, pollution of residents’ wells around the Bantar Gebang TPA, and pollution of the Asem River flow.

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