Landfills are one of the most under-appreciated yet important pieces of American infrastructure. The current method employed in most states, Dry Tomb landfills, is outdated for today’s world. Rather than continue this technique, modernized options like bioreactor landfills may be a more cost-effective and sustainable solution. This switch would turn waste into a resource. Rather than a long-term liability that burdens our future generations and wastes massive amounts of energy, while entombing it for centuries, we can do more.
Dry-Tomb landfills are the most common method for waste disposal in the United States. These isolate waste from the surrounding environment, which creates a long-term waste burden, in which a day’s worth of waste is tossed and then covered by a few inches of soil. Liners, covers, and drainage systems are used to prevent water and air from entering the waste, aiming to minimize liquid runoff, and thereby slow the waste’s decomposition to a snail’s pace. This, in theory, reduces short-term risks to the local environment. However, the likelihood of failure and subsequent contamination is high, and within the timeframe of operability. Dry-tomb facilities do have advantages, especially in the short term; the initial containment and groundwater supplies are well protected.
Bioreactor landfills represent the opposite picture; where liquids are used to break down waste. This liquid circulation increases degradation, and air is then added to enhance microbial processes. Further, three types of bioreactor landfills exist: aerobic, anaerobic, and hybrid. Of these, anaerobic bioreactor are the most used. Unlike dry-tomb landfills, which can take decades to decompose waste, bioreactors can do in a matter of years. Waste toxicity and mobility is also limited; disposal costs are reduced as are post-closure and maintenance costs. This method also generates more methane gases, which can be used to generate electricity and heat that can be used onsite or sold regionally to further offset costs.
There are disadvantages to this method, including gas emissions that can occur when it is not properly captured and utilized. A foul odor around the site, higher possibility of landfill fires, and overall structural stability problems also exist. Bioreactor landfills have higher upfront costs associated with them than dry tomb, and there are higher monitoring costs.
We can transition from the dry tomb method in many ways. The EPA offers a Landfill Methane Outreach Program (LMOP) to provide technical assistance and information funding resources for landfill gas energy projects, such as bioreactors. States can offer incentives, grants, tax credits, and other benefits. Furthermore, the federal government can work to de-incentivize ‘dry tomb’ use by ending protection of a dated practice (for new landfills), directing resources towards upgrading these methods for the current century. Redirecting those funds towards the implementation of bioreactor landfill designs and innovation.
How can we balance the tradeoff of high upfront maintenance costs associated with bioreactors? A solution is selling the energy generated through the capture of the methane emissions associated with these landfills, which would inherently recoup initial loss. Through the use of the LMOP program, these projects can break even within roughly five to eight years, some projects as short as three years. This can provide valuable incentive over the dry tomb method which, in comparison, is limited in its ability to be a revenue-generating investment. With owner liability, the economic impact is greater when considering the land remains unusable for decades for other commercial or recreational purposes.
Dry tomb landfills carry construction costs that amount to between 500,000 and 1 million dollars per acre (the range accounting for site-specific factors and requirements). Closing these landfills also has a wide range of estimated costs, between $80,000 and $500,000 per acre post-closure expenses. Furthermore, over a 30-year period, maintenance and monitoring costs can range between $64,000 and $88,000 per acre. Over the long term, there are costs that extend to the environment and local health, including groundwater contamination and methane emissions.
Whereas dry tombs generate emissions and burdens, bioreactors create opportunities: they decompose waste quickly within a five- to 10-year timeframe, reduce long-term maintenance problems, and produce methane that can be captured and utilized generating heat, electricity, and renewable natural gas. This creates revenue that allow these systems to pay for themselves, utilizing renewable hydrocarbons.
With bioreactors, the overall risks to the environment are mitigated, reducing the risk of a ‘delayed disaster’ (i.e., inevitable failure) that comes with landfills. Transition to bioreactor landfills could be expedited by upgrading existing dry tomb landfills to bioreactors, avoiding the need for new waste sites, while improving existing sites.
Current laws/ regulations, notably Subtitle D of the Resource Conservation and Recovery Act (RCRA), put requirements on landfills, such as minimizing leachate, preventing the addition of water, and employing specific liner, capping, and monitoring systems. This regulation largely allows for dry tombs to flourish in the United States and, bioreactors fall outside the scope of this regulation, the addition of moisture, makes them, by this standard, non-compliant. Shifting to more performance oriented policy that incentivizes innovation with the goal of the most contained, most efficient, and sustainable operation would level the playing field and bring about more competition that further lowers costs.
Further complicating the policy picture, states have varying regulations, some have even stricter practices than the EPA. All together, there is a complex permitting process. With this in mind, bioreactors require leachate management approvals, methane capture usage permits, air/ water quality testing, and more, with violations potentially triggering critical reviews. These can be overcome mainly by expanding Research, Development, and Demonstration permits (RD&D). These landfill permits allow facilities to test innovative landfill designs and operations that do not align with regulations.
Bioreactor landfill technology may still be an emerging technology, with developed nations rolling these out in some capacity, revisiting Subtitle D to allow bioreactors and for state-level reforms that can establish permitting framework tailored to bioreactors. Public-private partnerships could also prove useful. While bioreactors are not the perfect answer to waste management, they can offer a scalable bridge between where we are and where we can be. These represent decisive steps towards making waste management and infrastructure more efficient, cleaner, and sustainable.
Written by Trevor Mathia, Public Policy Intern
The Alliance for Innovation and Infrastructure (Aii) is an independent, national research and educational organization working to advance innovation across industry and public policy. The only nationwide public policy think tank dedicated to infrastructure, Aii explores the intersection of economics, law, and public policy in the areas of climate, damage prevention, eminent domain, energy, infrastructure, innovation, technology, and transportation.