Could bioreactor technology be the innovation that eliminates our current dependence on traditional landfills? That’s a question that all kinds of organizations, from waste management professionals to the Environmental Protection Agency, want to know the answer to.
While there’s certainly no question that bioreactor landfills offer many benefits over conventional ones, they are not without their own unique challenges. Read on to learn more about the pros, cons, and inner workings of bioreactor landfills.
What is a bioreactor landfill?
As defined by the EPA, a bioreactor landfill is a type of landfill for municipal solid waste. Its design and operation allows it to transform and break down organic waste much more quickly than a conventional landfill.
By strategically adding moisture and/or air to the waste, a bioreactor landfill is able to enhance natural microbial processes. The result is a greatly increased rate of waste degradation and stabilization. There are four main types of bioreactor: aerobic, anaerobic, hybrid, and facultative.
What are the benefits of a bioreactor landfill?
When compared with conventional landfills, bioreactor landfills offer a number of potential advantages. These include:
Increased landfill capacity
In some senses, a bioreactor landfill performs something of the same function as a trash compactor. By encouraging organic waste to break down quickly and release its gas, a bioreactor landfill can decrease the overall volume that current waste occupies in the landfill, making more room for additional waste.
Industry experts estimate that anywhere between 15 percent and 35 percent of landfill space can be recovered through the accelerated decomposition process in a bioreactor landfill. This helps prolong the landfill’s functional life span and defers the need to develop extended landfill capacity or to create new landfills.
Accelerated waste stabilization
Waste breaks down faster in a bioreactor landfill. It also reaches stabilization at an accelerated rate.
This means that landfill operators can convert closed landfills to other useful purposes much sooner than was previously possible, but with the same assurance of environmental safety. There is, therefore, a much lower likelihood that a bioreactor landfill will contribute to long-term contamination of the environment.
Reduced leachate management costs
Leachate is a hazardous landfill byproduct. It requires careful – and sometimes costly – management by landfill operators to avoid polluting or damaging the surrounding environment and groundwater.
However, leachate actually takes an active role in a bioreactor system. It is recirculated as the added moisture for both aerobic and anaerobic reactions. This means that the costs typically required for the management and the off-site treatment or disposal of leachate are greatly reduced.
Improved landfill gas management
The gas generated by landfills can be used for energy, either onsite or through municipal power grids, when it is captured. The accelerated rate at which waste decomposes in a bioreactor landfill likewise accelerates the generation of landfill gas.
This increases the potential for beneficial use of the gas and reduces the need for a long-term landfill gas management strategy because the gas can be captured and used right away. Furthermore, recovered bioreactor gas is usually of a very high quality.
What challenges and issues are associated with bioreactor landfills?
Despite their many potential benefits, bioreactor landfills also present a number of drawbacks as well as issues that must be handled carefully. These include:
Because bioreactor landfills are a relatively new technology, public resistance to them may be strong at first. In particular, residents who live near a new or proposed bioreactor landfill may be worried about the potential for groundwater problems or increased odors. Both of these are concerns that landfill operators will need to address.
When conventional landfills encounter stability problems, the wet condition of the waste is typically one of the contributing factors. In a bioreactor landfill, the waste is intended to be much wetter than in a conventional landfill.
The addition of extra liquid can cause changes in the geotechnical characteristics of the waste mass, which could compromise the landfill’s overall stability. This is especially important to address with conventional landfills – not originally designed for such a purpose – that have later been converted to bioreactor landfills.
Again, given how new bioreactor landfills are, regulations around landfill management have yet to address the specific needs of this new technology. Consequently, the features required for a bioreactor may not always be accommodated or approved under current regulations.
For example, many state regulatory agencies do not currently permit the addition of liquids into a landfill. This means that landfill operators must apply for a variance in order to be able to operate the bioreactor properly, though it is worth noting that most regulatory agencies are generally supportive of the landfill bioreactor concept.
There are additional revenues associated with bioreactor landfills, but there are additional costs as well. Unfortunately, it is not guaranteed that the one will outweigh the other. To ensure the economic feasibility of a bioreactor landfill, landfill operators must be sure to carefully evaluate the specific design and operational factors of any proposed project.