Landfill organic stability
The DNR, in consultation with external partners, is exploring ways to reduce the long-term risk of landfilling by reducing the time it takes for the waste in municipal solid waste landfills to become stable — that is, to reach the point when engineering and maintenance efforts are no longer necessary to control the potential environmental effects of decomposing organic materials in the waste.
Modern landfills contain significant amounts of organic wastes (such as food scraps, paper, wood and other degradable organic compounds). The decomposable organic materials degrade within the landfill environment at varying rates depending on material and environmental characteristics. The degradation of organic wastes within modern landfills produces methane and other organic and inorganic gases, leachate containing harmful organic and inorganic compounds, and settlement within the waste mass. Failure to adequately manage these products imposes an economic burden and an environmental risk on future generations. By managing organics properly over the short term, we place the responsibility for costs and risks on the generation that created the wastes
As landfill facilities grow larger and more complex, the need to find waste disposal methods that reduce the impacts of organic matter degradation becomes more important. Larger landfills are generally believed to be more difficult to repair, and present more significant potential costs and risks.
Landfill organic stability plan rule
An administrative rule promoting landfill organic stability has been in effect since 2006. The rule, s. NR 514.07(9), Wis. Adm. Code, requires owners and operators of municipal solid waste landfills to incorporate landfill organic stability strategies into the plans of operation for their facilities. The rule required existing landfills that had not filled 50% or more of their approved capacity by Jan. 1, 2012, to submit a plan modification by that date to implement organic stability measures. The rule also required that plans of operation for all new landfills or landfill expansions that were submitted for review after Jan. 1, 2007, to include organic stability plans. All landfills subject to the rule have approved plans to meet the organic stability rule.
- Guidance for Landfill Organic Stability Plans (WA-1125)
- NR 514.07(9), Wis. Adm. Code
- Strategies for Reducing Degradable Organic Wastes in Landfills
Retrospective analysis of the landfill organic stability rule
When the Natural Resources Board approved the organic stability rule, it requested a periodic review of the performance of municipal solid waste landfills that implemented practices intended to meet the goals in the rule. The Waste and Materials Management Program used both internal and external resources for the initial review. External review was conducted by contracting with a panel of four engineering professors with known experience and credentials in research on solid waste landfills and waste decomposition processes. Department staff conducted the internal review by collecting essential information about the landfills and annual reports submitted by landfill operators. Staff also served as a sounding board for the panel of professors and reviewed the final report.
The panel found that available information varied considerably, due to the some landfill operators having more time to start operations and data collection than others. The panel expanded the scope of its review by conducting interviews of landfill operators to obtain more detailed feedback and supplemented its information base using members’ experience with other research.
Most landfill operators chose to meet organic stability goals through leachate recirculation, as amended by implementing approved research, development and demonstration plans that allowed use of additional liquids. The panel reviewed choices operators made about relative use of leachate recirculation vs. additional liquids in terms of meeting organic stability goals.
The panel's final report, issued in May 2014, states that the goals of the organic stability rule coincide with general knowledge in industry and the research community regarding stabilization of decomposable organic waste in landfills. Individual goals in the rule may not be met at the same time, but likely can be achieved by the end of the 40-year long-term care period. Leachate recirculation and use of additional liquids appear to enhance gas generation at the landfills studied, but the extent of use of either or both activities varied considerably. The panel report concludes with a list of recommendations from the collective experience of its members.
The DNR greatly appreciates the review performed by the panel. It does not object to the recommendations, but some require additional authority and/or resources to implement.
- Retrospective Analysis of Wisconsin's Landfill Organic Stability Rule: Is the Rule Meeting Its Objectives?
The appendix to the final report reproduces some of the graphical depictions of landfill gas generation rates that owners used in organic stability plans. In some cases, data from gas extraction systems are overlaid on the graphs. Department staff performed their own comparison between predicted gas generation rates vs. gas extraction data for all active municipal solid waste landfills and some closed ones.