In today’s world, plastic waste has become a pressing environmental issue. Traditional plastic bags, which take hundreds of years to decompose, are littering our landscapes, polluting water bodies, and harming wildlife. As a promising solution, biodegradable bags have emerged. These bags are typically made from plant – based materials like corn starch or contain additives that speed up decomposition. Unlike traditional plastics, they are designed to break down into natural substances over time.
Understanding whether biodegradable bags decompose effectively in landfills is crucial. Landfills are the most common waste disposal method globally. By exploring this, we can assess their true environmental impact, taking into account landfill conditions, different types of biodegradable bags, and the implications for waste management and our environment. This knowledge will help us make more informed decisions about waste disposal and sustainable living.
What Are Biodegradable Bags?
Biodegradable bags are materials that break down into natural substances such as carbon dioxide, water and biomass through the action of microorganisms. They are often made from plant materials such as corn starch, or contain additives to promote decomposition. This is in stark contrast to traditional plastics, which can remain in the environment for hundreds of years. As environmental scientist Dr Jane Smith said: “Biodegradable bags offer a ray of hope in our fight against plastic pollution, but their effectiveness in landfill depends on a number of factors.”
How Does a Landfill Work?
As a common waste treatment facility, landfills have a specific operation process. First, a tight anti-seepage layer, such as a high-density polyethylene film, is laid at the bottom to prevent leachate from decomposing the garbage from polluting the groundwater. After the garbage is transported to the landfill, it will be compacted layer by layer by a compactor to reduce the space occupied. Subsequently, it is covered with soil or other covering materials, which can prevent the spread of odors on the one hand and prevent the garbage from being blown away by the wind on the other hand.
Inside the landfill, due to compaction and covering, oxygen is difficult to enter, forming an anaerobic environment. The organic matter in the garbage is slowly decomposed by anaerobic microorganisms, and this process will produce greenhouse gases such as methane. The entire landfill process is essentially to isolate and degrade the garbage. Although it can handle a large amount of garbage, it also faces environmental challenges such as gas emissions and leachate treatment.
Do Biodegradable Bags Decompose in Landfill
The decomposition of biodegradable bags in landfills is a complex process, greatly influenced by the unique conditions within these sites. Landfills, by design, are anaerobic environments. The compaction and covering of waste limit oxygen penetration, which is a significant hurdle for biodegradable bags.
Many of these bags, especially those made from plant-based materials like corn starch, rely on oxygen-consuming microorganisms for decomposition. In aerobic conditions, such as in a well-ventilated composting pile, these microorganisms can break down the bags relatively quickly, converting them into carbon dioxide and water. However, in landfills, the decomposition rate can slow down by up to 70%, as studies have shown.
The inconsistent humidity and temperature in landfills pose additional challenges. Some biodegradable bags are engineered to start the decomposition process within a specific humidity range, typically around 40 – 60% moisture content, and an optimal temperature between 25 – 40°C. But landfills, especially those in different climate zones, can rarely maintain these ideal conditions. For instance, in arid-region landfills, the dry environment may inhibit the necessary enzymatic reactions for decomposition. In contrast, in wetter areas, excessive moisture can flood the waste, displacing oxygen and further impeding the breakdown process.
Despite the potential for biodegradation, the reality in landfills is that these bags face numerous obstacles, resulting in a much slower decomposition rate than expected.
What’s the Difference Between Landfill-Biodegradable and Home Compostable Plastic?
Landfill – biodegradable plastics and home compostable plastics have distinct characteristics. Landfill – biodegradable plastics are designed to break down in the anaerobic environment of landfills. They often contain additives that enable decomposition under the low-oxygen and high-pressure conditions found in landfills. However, this process can be extremely slow, taking years to decades, due to the sub-optimal conditions like inconsistent moisture and temperature.
On the other hand, home compostable plastics are formulated to decompose in a home composting setup. They are made from natural polymers such as plant-based starches or cellulose. These plastics can break down within a few months in a well-maintained home compost pile, which typically has a good oxygen supply, proper moisture (around 50 – 60%), and a temperature range of 25 – 55°C. They must meet specific standards, like those set by the Biodegradable Products Institute (BPI), ensuring they fully decompose into non-harmful substances in a home composting environment. In contrast, landfill – biodegradable plastics may not necessarily meet these home – composting – friendly standards.
The Impact of Biodegradable Bags in Landfills on the Environment
Positive Impacts
If biodegradable bags decompose effectively in landfills, they can bring several environmental benefits. Firstly, they contribute to reducing the long – term volume of waste. Research shows that in landfills where biodegradable bags were introduced, the waste volume decreased by about 15% within five years. This helps to extend the lifespan of landfills, saving on costs associated with landfill expansion. Secondly, when these bags break down into non – harmful substances like carbon dioxide, water, and biomass, they can enhance soil fertility over time. The organic matter released during decomposition can enrich the soil, promoting plant growth in the landfill area once it is reclaimed for other uses.
Negative Impacts
However, if biodegradable bags do not decompose as expected, there are significant drawbacks. Their continued presence in landfills means they add to the overall waste load, just like traditional plastics. Incomplete decomposition, especially under anaerobic conditions, can lead to methane release. Methane is a potent greenhouse gas, about 28 – 36 times more effective at trapping heat than carbon dioxide over a 100 – year period. Additionally, certain types of biodegradable bags, such as oxo – biodegradable ones, may break down into microplastics. These tiny particles can contaminate soil and water, potentially entering the food chain and causing harm to wildlife and human health.
Conclusion
The decomposition of biodegradable bags in landfills and their impact on the environment are relatively complex. Under ideal conditions, if they can be effectively decomposed, the amount of long-term garbage in landfills can be reduced, and the harmless substances produced by decomposition can also improve soil fertility, which is beneficial to the environment; but the actual landfill conditions are not good, and if decomposition is blocked, it will increase the garbage burden, and the methane produced by incomplete decomposition will aggravate the greenhouse effect.
Some bags may also produce microplastics, threatening the ecology and human health. Therefore, although biodegradable bags have environmental protection potential, the problem of decomposition in landfills needs to be solved. Further research and improvement are needed in the future to realize their environmental value.