Optimizing Landfills: What can we do until waste is wasted away?
At a glanceLandfills across North America are running out of space. While the current collective focus is on waste minimization and waste utilization, landfills will continue to be used as part of a holistic waste management system. Until the day when we can move closer to zero waste as part of a circular economy, we need to drive solutions that can optimize landfill airspace and overall capacity.
Landfills across North America are running out of space. We all know the solution for less garbage is to reduce, reuse and recycle. While the current collective focus is on waste minimization and waste utilization, landfills will continue to be used as part of a holistic waste management system. Until the day when we can move closer to zero waste as part of a circular economy, we need to drive solutions that can optimize landfill airspace and overall capacity. So, adding sustainably focused design and operations practices becomes critical going forward. Expanding capacity is a sure way to extend life; however, operations play a crucial role in the sustainable management of landfills. It’s not just about where the waste goes to rest but rather how to optimize the space to extend the life of landfills and make sure there is a safe place for managing communities’ solid waste.
Design, divert and assess
There are ways to optimize landfill capacity: implementing the best possible design, including regulatory slope considerations, diverting recyclables, streamlining operations and reducing volume through waste mining are some of them.
Landfill design and slope considerations: Most active landfills across North America have similar designs governed by regulatory slope requirements (most common are 4H:1V and 3H:1V), as verified by geotechnical assessments, to determine the amount of airspace allowed for waste placement. Considering changes in the design of the operating landfill is an option. Still, it takes time and money to prepare the change, submit the application, respond to regulatory questions, finalize the design and complete construction — a process that can take years in some places across the US and Canada. Most US and Canadian regulatory jurisdictions maintain that landfill slopes should not exceed 3H:1V or 4H:1V slope, which is a 33 percent to 25 percent slope. Should common ground be found from jurisdictions where they accept a 3H:1V maximum slope, landfill capacities can be substantially increased within the same permitted limits (footprint) of waste. For landfills in jurisdictions that do not allow for maximum slopes to be more than 4H:1V, there is a crucial loss of airspace resulting in shutting down sooner, which results in loss of revenue.
Diverting recyclables and organics: On the other hand, the impact of diverting recyclables is underestimated. Waste diversion can significantly increase the landfill’s capacity by reducing the amount of material that is disposed, automatically adding valuable years to the site’s lifecycle and making it more sustainable in the process. We all know the classic recyclables: glass, scrap metal, paper/cardboard, plastics and wood, but there are many more items that go into landfills that can be recycled, such as mattresses, drywall and other construction byproducts. “By diverting recyclables and composting organics, the amount of material that goes into landfills can be reduced dramatically,” says David Barton, Sr. Engineer and Project Manager. There are several jurisdictions in Canada and the US that do not yet have recycling programs, and so all this recyclable material goes to the landfill and occupies the airspace. Implementing recycling and organics management programs in these jurisdictions is a fantastic first step to extending the life of landfill through waste reduction.
Streamlining operations: Operational challenges are a common issue across North America. Optimizing the use of airspace through design and operations such as proper compaction of the waste are just some of the ways landfills can be healthier and more efficient, which will also better control the movement of leachate and landfill gas. “Operations not only have a positive impact on reducing costs and increasing revenue but can also help minimize the environmental effects and overall footprint,” adds Barton. Various technologies, such as GPS installed on equipment, can enable landfill operators to monitor and maximize compaction efforts in the active areas of a landfill, and help to streamline operations and increase efficiency. These types of technologies lead to more efficient equipment usage, reduce fuel consumption and thereby associated greenhouse gas emissions.
Waste mining: Waste mining is an ideal option for a site that is running out of airspace/capacity and also aids in reducing the potential liability of an unlined landfill. Waste mining allows for the excavation of existing landfill materials, the recovery and separation of recyclable materials and subsequent re-compaction of the residual waste as it is efficiently placed back into lined portions of a landfill. This results in reduced waste volumes, freeing up more airspace, as well as allowing for placement of the mined waste into lined cells (if excavated from unlined cells) to reduce negative groundwater impacts. Even though waste mining has the potential to be costly, there is an opportunity to recover resources while freeing up airspace. Historically, landfill operators freely placed soils for daily and intermediate cover without removing it before subsequent waste placement. A few feet of soil cover material might not seem like much, but over a large site, those few lifts of material cause an extensive loss of airspace. This layer of cover material, especially when using lower permeability materials like clay, also can cause problems by forming localized perched or mounded leachate pockets that may result in lateral outbreaks and seeps on outer slopes of landfills, while at the same time, limiting landfill gas migration within the waste mass. These operational challenges reduce the effectiveness of leachate and landfill gas collection system, reducing the ability of leachate to migrate down to the leachate collection system and landfill gas from migrating toward, and being collected by, landfill collection system infrastructure, which leads to a reduction or loss of a beneficial resource that can be used to produce electricity or renewable natural gas.
Course of action
Of course, determining which of these actions is best suited for each landfill will depend on a case-by-case assessment. Every site is different. Every landfill owner’s goals for their properties are different. Every province and every state are different. So, every plan and design must be considered differently and aligned with the ultimate goals and unique requirements of each individual site. There is really no one size fits all.
A site-specific assessment is the best place to start, and the perfect addition is to pair it with a review of local and the most recently revised regulations. “If some regulators were to allow going up to a 3H:1V slope (33%) instead of 4H:1V (25%), that could give the landfill enough to extend airspace life,” says Dave Engstrom, Landfill Engineer. This extension can be significant in a number of cases.
We look at a landfill holistically, as an entire system to integrate planning, design and operations principles that extend their lifecycle and improve efficiencies. Looking at individual systems or individual components may be short-sighted as there are many interconnected opportunities and challenges. There are mounting pressures as landfill capacities are nearing their threshold and communities are searching for waste solutions that will limit the amount of landfilled waste and move to a model where all manufactured products can be reused and recycled as part of a circular economy. In a perfect world, we would implement infrastructure solutions that can treat waste. Until that day, we can implement solutions that optimize the landfill space available through expansion and diversion tactics.
Contact us to discuss landfill engineering solutions or to conduct a holistic evaluation to identify opportunities to optimize landfill space.