Ryan Joslyn
University of Central Florida, MS
Robert P. Stearns/SCS Engineers Master’s Scholar
Project: Field Investigation of an Elevated Temperature Florida Landfill
For reasons that are not entirely clear, incidents of elevated temperatures in municipal solid waste landfills are occurring at increasing frequency. These landfills present temperatures that well exceed the range tolerable for micro-organisms (~176°F). Given the significance of elevated temperatures at landfills and the growing number of landfills with these issues, the goal of Joslyn’s research is to develop a more complete understanding of elevated temperature landfills using landfill gas and leachate monitoring data, specifically in the state of Florida.
Robert P. Stearns, Chairman and CoFounder of SCS Engineers, joined the EREF Board of Directors in 1999 and served as Chairman from 2004–2005. At SCS, he directed or served in a review capacity on many of the firm’s solid waste management-related projects. In 2007 EREF awarded the first Robert P. Stearns/SCS Engineers Master’s Scholarship, which was established to expand EREF’s successful doctoral-level scholarship program.
Temporary Landfill Caps
Temporarily capping landfill slopes is becoming a common measure for landfill operators. There are many benefits to closing landfill slopes with geomembrane on a temporary basis. One of the benefits is delaying construction of the final cover. Following is a discussion of the steps that should be taken to determine whether temporarily capping the slope with geomembrane and postponing the final cover construction is a better financial/operational decision.
Cost Burden
Constructing the final cover is costly, and it is considered an unavoidable expense that has no return on the money spent. Therefore, some operators perform a financial evaluation to determine whether the final cover construction costs can be delayed (provided, of course, that such delays are acceptable to the regulating agency). When evaluating whether to delay the final cover, the cost of maintaining the slopes during the postponement period should be considered. The operator must look at the financial aspects of either closing the slopes with a temporary geomembrane or of leaving the slopes open during the postponement period.
Temporary Landfill Capping Option
The benefits of temporarily capping the slopes during the postponement period may include:
The other side of the coin is the expense associated with the temporary cap. There may be repair costs associated with the geomembrane every few years in order to ensure that the temporary cap remains intact.
Leaving Slopes Open Option
The option of leaving the slopes open during the postponement period involves maintenance expenses such as:
The benefits of leaving the slopes open are twofold: first, the operator will save the costs of constructing the temporary cap; and second, the operator will gain additional airspace as waste settles during the postponement period.
Experience with the Temporary Capping Option
As discussed above, both options provide the benefit of gaining additional airspace during the postponement period. Constructing a temporary cap involves the costs of materials and installation, including the geomembrane and the ballasting system that keeps the geomembrane in place. Generally, the financial and non-tangible benefits of a temporary cap that remains in place five years or longer are more attractive than leaving the slopes open; therefore, most operators choose to install a temporary cap. The next step in the financial evaluation should be comparing the costs of the temporary cap to permanently closing the slopes without postponement.
Final Step in the Financial Evaluation
The next question is whether it makes financial sense to postpone the construction of the final cover.
Waste settlement during the postponement period and the resulting airspace are considered the determining financial factor in choosing the right option. If the present worth value of the airspace generated from waste settlement during the postponement period is greater than the cost to construct the temporary cap at the present time, then the temporary cap option would make financial sense; otherwise, the final cover should be constructed without postponement.
It should be noted that the length of the postponement period plays a very important role in this financial equation. Longer postponement periods have the potential for a greater gain in airspace. Another incentive that should be factored into the financial evaluation is the potential return on the money set aside for the final cover construction during the postponement period.
To assist with this financial evaluation, landfill operators are encouraged to discuss these options with their landfill engineers. Settlement models can be performed to calculate the amount of airspace that may be generated during the postponement period as well as the present worth value of the generated airspace. The returns on the final cover construction costs during the postponement will just be “icing on the cake.”
Read the related Advice From the Field blogs from the landfill and LFG experts at SCS Engineers:
Contact the author: Ali Khatami or your local SCS Engineers’ office.
Typical Conditions
The organic matter that is placed in landfills goes through a decomposition process that is exothermic and releases heat inside the landfill space. There are also other exothermic processes such as metal corrosion, hydration, carbonation, and acid-base neutralization that contribute to the heat generation phenomenon in landfills. Municipal solid waste has a relatively low heat conductivity characteristic, which means the heat is not as easily conducted through the waste keeping the landfill interior generally warmer than the areas near the landfill exterior.
Landfills expel the heat in different ways; propagating through the waste mass to the air, ground, leachate, and gas heat sinks. The heat escapes the landfill at its boundaries by convection to the air above the landfill surface and by conduction to the ground below the waste. Heat can also escape from landfills through liquids and gases removed from the landfill. For example, by conduction, via leachate that flows through the waste and is removed by leachate sumps and by convection, and via gases generated inside the landfill that are removed through the gas collection system.
Special Conditions
The large majority of landfills in the country show no signs of special conditions indicating too much heat. The characteristics noted in this blog have been observed in a few large, deep, wet landfills. Field investigations at landfills with high temperatures revealed that the highest temperatures are generally located at mid-point to the two-thirds depth of waste from the top surface. Temperatures as high as 250 °F have been recorded by specialized measuring devices.
Under certain conditions, elevated temperatures may occur inside a landfill, and the excess heat changes the character of chemical reactions taking place in the landfill, such as the decomposition process of the organic matter. Other documented changes that may take place in accumulated heat conditions are: leachate becoming stronger with higher BOD, lower pH, higher carboxylic acids and salts; concentrations of certain acids increasing; carbon dioxide and carbon monoxide generation increasing; the ratio of methane to carbon dioxide decreasing; hydrogen generation increasing; landfill odors changing to a significantly pungent character; landfill settlement rates increasing; gas generation and gas pressure increasing; leachate generation increasing; along with other changes.
Research
Heat generation in landfills is studied by researchers, reported in technical literature and scientific papers by academia and the industry. A summary of the findings related to the amount of heat generated from municipal solid waste in landfills is presented in Table 1 of Heat Generation in Municipal Solid Waste Landfills posted on the California Polytechnic State University, Robert E. Kennedy Library website.
Since the issue of high temperatures in landfills is of extreme importance to landfill operators with respect to compliance, operations, and financial aspects of these cases, finding out the cause and sources of excess heat is a hot subject in the field of landfill science. The largest research grant supporting the on-going research in this field was awarded by the Environmental Research & Education Foundation (EREF) in December 2014. So far, three parts of a technical article explaining chemical mechanisms through which organic matter decomposes and generate various types of other chemicals and heat have been published by the researchers of the above grant in Waste360. The research is on-going, and more information will be published in future. Links to the first three parts of the above article are provided here:
Prevention, Diagnosing and Managing ETLFs
SCS was involved in the preparation of standards for large, deep and wet landfills for a major waste operator in 2016. The intent of the standards is to implement measures to prevent elevated temperature conditions in large, deep, and wet landfills. SCS’s experience at such landfills and its in-depth knowledge can be valuable to those waste operators who are either experiencing elevated temperature conditions in their landfills or want to prevent conditions forming in their landfills proactively.
About the Author: Dr. Ali Khatami
Join SCS Engineers at the Global Waste Management Symposium to learn more, or click these links read about our landfill and landfill gas to energy services, clients, and articles.
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Discovering unexpected pockets of soft soils at the time of construction can delay your project and drive up costs for landfills, support features, and many other types of construction. If you don’t find them, building over them can result in unexpected settlement affecting a structure or building, or cause a slope stability problem for a berm or stockpile. You can avoid both of these scenarios with early investigation and appropriate construction planning.
While landfill development investigations typically require numerous soil borings within the proposed waste limits of the landfill, it’s common to overlook perimeter areas. Pockets of soft soil deposits can be associated with nearby existing wetlands, lakes, or rivers; with wind-blown silt or ancient lake deposits from periods of glaciation; or with fill placed during previous site uses.
The landfill perimeter areas may contain tanks for leachate or fuel, buildings, perimeter berms for screening or landscaping, stockpiles, and other features. A tank or building constructed over soft soils could experience unexpected settlement affecting the performance and value of the structure. The potential for a slope stability problem can increase for a large berm or stockpile built on soft soils.
The first step to avoid these problems and identify problem soils is to include perimeter areas in your subsurface investigation. Perform soil borings or test pit excavations at the locations of the proposed perimeter features such as tanks or berms. If you encounter soft soils, address them like this:
Contact SCS’s geotechnical engineers for more information on how to find and test soft soil areas early in a landfill’s project schedule, so you can effectively address associated construction issues in a way that considers cost and minimizes unexpected project delays.
The Association for the Advancement of Sustainability in Higher Education (AASHE) has awarded UNH the STARS Platinum rating in recognition of its sustainability achievements. STARS, the Sustainability Tracking, Assessment & Rating System, measures and encourages sustainability in all aspects of higher education. The Platinum STAR is the highest possible rating and held by only a handful of higher education institutions in the world.
Some highlights of UNH’s sustainability achievements:
“UNH committed to use renewable energy and move toward a sustainable energy economy early,” said Steve Hamilton, Sr. Vice President of SCS Engineers – Energy Division. “The decision to convert landfill gases to renewable energy kick-started a very successful program which is paying off for the University and in the surrounding community.”
Benefits include:
They all use permitted grain elevators. According to Reuters, in 2017, the United States had 25 billion US bushels of storage capacity, a growth of 25% in the previous decade. Reuters Business News, April 11, 2017. There are a myriad of safety and permitting requirements for grain elevators; this article lists a few in Wisconsin.
Securing the proper air permits helps safeguard these facilities against the legal, financial, and reputational risks of non-compliance. The air permitting process can be complicated, but there are tools and people that can help.
Environmental engineering firms help guide companies through the process and offer direct support. States provide tools and support such as the self-serve tools on the WDNR website, for example, to help determine what level of permitting is applicable too. These State environmental sites provide the necessary permitting forms and backup calculations specific to the type of permit your facility may need to apply for. You may be able to submit an application online, and a certified engineer can do that for you as part of a permitting plan.
If you find the sites and requirements perplexing, ask a qualified environmental engineer to help. SCS Engineers professionals are recognized for their environmental permitting knowledge and are available to answer questions.
Learn more about air-permitting in Wisconsin or contact one of SCS Engineers’ local offices in a region near your facility.
These grants often target rural areas that don’t necessarily have the support needed to catch up in today’s world of rapid technological advances. A quick Google search shows that at the national level, the USDA offers a Solid Waste Management Grant which may be applied to the cost of program improvements such as landfill evaluations, technical assistance, or training. For this particular grant, any local government, academic institution, or nonprofit servicing an area with fewer than 10,000 people may apply.
This type of funding presents an opportunity for SCS to help address clients’ financial burdens. Awareness of the grants available is a common obstacle, but with some region-specific research, potential project identification, guidance and assistance with grant funding SCS can enhance your arsenal of services.
Here are some places to look for funding:
Contact the authors if you have questions: Ryan Duckett and Quinn Albertson, we’re always happy to help.
Pat Sullivan discusses two case studies that provide examples of two different approaches to odor management. The proactive approach resulted in a more positive outcome than the reactive approach. Although the odor issues never go away completely, the proactive facility has avoided lawsuits and regulatory enforcement and continues to have a positive working relationship with the community.
SCS Engineers freely shares our articles and white papers without imposing on your privacy.
Click to read Part I of this two part series. We’ll let you know when Part II is published soon.
The authors of this article in Renewable News thought it would be interesting
to readers who are in the recycling industry to see the kind of commodity pricing issues that were discussed in a recent analysis for a large recycling project study.
The data on price variability and waste composition were used to prepare several scenarios in Pro Forma modeling to predict the “downside” of market shifts in project performance. In our experience, this provides stakeholders with good ideas of potential market risks and the potential sharing of anticipated revenues with high, medium, and low-end pricing of recyclables.
The U.S. is heavily dependent on the Chinese market for absorbing a major percentage of
recyclable paper and plastics we generate. So, potential changes to that market initiated by the Chinese is a cause for concern and for assessing contingencies. Officials for the Scrap Recycling Industries, China Scrap Plastics Association, and Bureau of International Recycling all indicated that China may be rolling out a new policy for expanding the list of banned materials and tightening the quality standards of recyclables coming into their country. Increasing knowledge of the markets and the impact on your program is a good way to get ahead of the potential impact of China’s new restrictions.
Increasing knowledge of the markets and the impact on your program is a good way to start getting ahead of the potential impact of China’s new restrictions.
Recycling and sustainable services including waste and financial analyses
Similar processing sites could be sited and operated across New York City. Organics comprise 31% of New York City’s waste stream, and a significant portion can be composted locally and returned to the environment to support green spaces. Decentralized community compost operations are part of the solution to recycling food scraps and diverting this material from landfills. Medium-sized community composting sites can exist in dense urban settings because they are neighborhood assets, as education centers, green spaces, and compost sources for community greening projects. With well-designed systems and appropriately-scaled equipment, they can be managed so that no odor or pest issues are created. These sites reduce carting distances and serve as an impetus for changing local land management practices by making high quality compost abundantly available.
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