Landfill bioreactors are gaining increased attention as an alternative to the conventional Subtitle D landfill. Both public and private sector landfill operators, as well as regulatory agencies including the U.S. Environmental Protection Agency, are actively supporting the development of this new landfill technology. This document gives an overview of what a landfill bioreactor is, what its potential benefits are, and what unique design, operational, and regulatory issues are associated with a bioreactor project. We also describe the services that SCS Engineers and SCS Field Services can provide to help you develop a successful landfill bioreactor project.
What is a landfill bioreactor?
A landfill bioreactor is a landfill designed and operated to accelerate the decomposition and stabilization of solid waste, usually under anaerobic conditions. Unlike Subtitle D landfills that are designed and operated to minimize contact between water and solid waste, the operation of a bioreactor relies on the addition of liquids to increase the moisture content of the solid waste to the optimum level for decomposition. The typical bioreactor will recirculate all of its leachate and may still require the addition of supplemental liquids for its operation.
What are the potential benefits of a landfill bioreactor?
Increased Landfill Capacity – One significant result of the more rapid and complete decomposition of solid waste in a bioreactor is additional disposal capacity that can be utilized during the active lifetime of the landfill. This additional capacity will generate additional revenue for the landfill operator and will help defer the need for developing additional landfill capacity.
Reduced Leachate Management Costs – Leachate recirculation in a bioreactor can substantially reduce leachate management costs and off-site treatment or disposal of leachate. The need for supplemental liquid addition may create opportunities for utilization of other liquid wastes such as sewage sludge.
Improved Landfill Gas Management – Landfill gas (LFG) generation from a bioreactor is also accelerated. This means a higher peak LFG generation rate, which increases the potential for beneficial use of the gas, and a shorter LFG generation period, which reduces the requirement for long-term LFG management.
Reduced Long-Term Liabilities – The more rapid and complete decomposition of solid waste in a bioreactor will potentially reduce the period during which long-term care and environmental monitoring must occur after closure. The more completely stabilized waste mass of the closed bioreactor is less likely than a conventionally closed landfill to create environmental liabilities in the future.
What are the unique design, operational, and regulatory issues associated with bioreactors?
Leachate Recirculation – A bioreactor requires a large amount of leachate and supplemental liquid to be distributed evenly throughout the waste mass. The design and operation of leachate recirculation systems require careful attention so that the system can meet this operational requirement without disrupting landfill operations or causing other leachate management problems.
Landfill Gas Management – The increased LFG generation over a reduced time period that comes with a bioreactor presents both opportunities and challenges. Design, installation, and operation of an active LFG collection system will be an essential component of any bioreactor operation. Successful operation of an LFG collection system under wet landfill conditions is difficult, particularly with the potential odor and Clean Air Act compliance issues at stake.
Geotechnical Stability – The addition of large amounts of liquid in a landfill bioreactor changes the geotechnical characteristics of the waste mass and requires special attention. Virtually every documented landfill stability problem has had wet conditions of the waste as one of the factors that contributed to the failure.
Regulatory Approval – While regulatory agencies are generally supportive of the landfill bioreactor concept due to its many benefits, existing landfill regulations do not always accommodate all the features required for a bioreactor. Regulatory waivers or approval of alternate procedures may need to be pursued as part of the permitting of a landfill bioreactor.
Economic Feasibility – There are both additional costs and additional revenues associated with landfill bioreactors. Whether or not the additional revenues exceed the additional costs is dependent on a number of design and operational factors that must be carefully evaluated.
How can SCS help you with your bioreactor project?
SCS is one of the nation’s oldest privately-held firms specializing in landfill engineering and construction, and in O&M of landfill support facilities. Since our founding in 1970, SCS has established itself as a leader and innovator in the solid waste industry. SCS today has more than 350 employee-owners in two dozen locations throughout the U.S. and overseas.
We have completed over 500 landfill investigation, siting, design, permitting, and construction projects and over 2,000 landfill gas projects. Our annual revenues are over $45 million, of which 75 percent are for landfill and landfill gas services.
Due to our widely recognized capability, particularly in the specialty areas of landfill gas and leachate management, SCS has established itself as one of the leaders in the emerging field of landfill bioreactors. We are currently involved in several of the first generation of landfill bioreactor projects being developed across the U.S. SCS can offer a full range of services in support of your bioreactor project including feasibility studies; design of all components of landfill bioreactors; local, state, and federal permitting; and installation and O&M services for bioreactor systems for LFG and leachate management
SCS is an employee-owned environmental consulting firm specializing in solid waste management. SCS has offices nationwide providing services to clients across the country.