Weathering several hurricanes in her career helped Janet Archer, a hog farmer in Goldsboro, North Carolina, prepare for Hurricane Florence.

Archer built her hog farm in Wayne County, North Carolina, in 1992, which means she’s survived a few deadly storms. Before Hurricane Florence hit in September 2018, there was Hurricane Fran in 1996, Hurricane Floyd in 1999 and Hurricane Matthew in 2016. Each time, heavy rains caused a river to flow between her home and farm, stranding Archer, her husband, Jack, and farmhands for days. But according to Archer, living through the storms has taught her and other hog farmers in the area valuable lessons about preserving their properties, which helped minimize the amount of waste and loss this past fall.

Seeing the devastation

Hurricane Florence dumped nearly 9 trillion gallons of water on North Carolina. The National Weather Service reported as much as 40 inches of rainfall along some parts of the coast. When all was said and done, the storm claimed five lives and left 1 million residents without power.

In the eastern part of North Carolina, significant rainfall hit Wayne County, which has a flourishing agricultural and livestock presence. Archer says Hurricane Florence brought 27 inches of rain to her farm alone, but the entire pork industry felt its effects. “Everything was challenged,” she says. “Not just livestock.”

Over the course of four days, 10 swine lagoons full of pig waste flooded, 33 overtopped and 6 suffered structural damage throughout the state, according to the North Carolina Department of Environmental Equality (DEQ).

The storm resulted in the loss of 5,500 hogs. But when framed in relation to the 2,000-plus hog farms that operate in the state, Archer says the loss was “minimal,” in part because farmers were more prepared thanks to their familiarity with storm preparation.

“Every loss is heartbreaking,” Archer says. “We had a generator fail. We’ve lost some animals. There was a barn roof that collapsed. We had much worse in Hurricane Floyd because we were not as prepared. One of the reasons farms did so well this time is because we learned some hard lessons from past hurricanes.”

Precautionary planning

On the state level, North Carolina preemptively closed some hog farms that reside in low-lying, flood-prone areas to mitigate damage. But on a local level, Archer says the community had to take it upon itself to plan and strategize before the storm.

“We’ve been through a lot of storms,” Archer says. “You always have to prepare. You always have to understand what’s going on. The advantage of a hurricane is you know it’s coming.”

By the time Hurricane Florence made landfall in mid-September, area hog farmers had already moved more than 20,000 pigs to higher, safer ground.

Days before the storm, Archer filled feed carts to the brim. She stocked up on enough fuel for the generator to power the farm for a week, and she made sure there was enough food and water for everyone on the farm.

“Somebody has to live on the farm with the animals,” Archer says. “We have a pull-out couch on the farm. Whoever stays has hot coffee, a hot shower and a bed. No cell service, but they can survive.”

Archer’s farm uses a manure lagoon as a waste management system. Despite their negative reputation in the national media, lagoons are a central part of sustainability at hog farms. With a 19-inch border around the edge in case of flooding, the lagoons hold and treat waste. Naturally occurring anaerobic bacteria in the lagoons breaks down solid waste into fertilizer, which farmers use to grow crops.

“Sustainability is a buzzword now, but it has been how we’ve survived for centuries,” Archer says. “Agriculture has a very low margin, and income has declined for 12 consecutive years, so we’re always looking for ways to turn a waste product into something to use. Even with manure, it may be defined as waste, but to us, it’s a nutrient.”

Archer says there are two “action points” hog farmers use to manage the lagoons before hurricanes. One way to prevent flooding is to drain the lagoon days before heavy rainfall is expected, she says. Hog farmers also keep extensive records on the lagoons along with soil samples to monitor phosphorous, potassium and nitrogen levels, which are inspected by the state.

“There can’t be any runoff,” Archer says. “It can’t leak through the soil. Municipalities can dump raw sewage in a creek or river and pay a fine. We have a zero-discharge requirement. Nothing we produce can leave our farm.”

When there is an issue with a lagoon, the DEQ investigates and then follows up to ensure the farm falls back into compliance with its permit, which is specific to each farm.

After the storm, farmers are responsible for their own cleanup. When her neighborhood experiences mass flooding and animal mortalities, Archer says the community pulls its resources together to clear debris and roadways so feed trucks and residents have access.

“All the farms stay in contact with each other to see who needs what,” Archer says. “We had caravans to help people get feed and supplies to areas. Farmers have equipment that general homeowners don’t have, and everyone works together.”

Waste to resources

Over the years, the pork industry has found solutions and created plans for mass animal mortalities after hurricanes.

Mark Rice, the director of North Carolina State University’s Animal and Poultry Management Center, says the center was founded in the 1990s to explore alternative uses of byproducts from animal waste and mortalities following natural disasters.

The purpose was to create value from the byproducts “that could help the farm income, so you weren’t just disposing of the mortality,” Rice says. “You could actually take that, process it and create something that can be used in another industry.”

Once approved by the state, the center started using hog and poultry carcasses as compost and blending it with soybeans to produce carp feed for the commercial fishing industry, Rice says.

In the early 2000s, the center also started to explore alternative uses for swine waste and treatment technologies, such as those used in manure lagoons.

“The focus was to offset costs and add value to that waste stream,” Rice says.

Because of the center’s leading research, hog farms today are able to convert captured methane gas from waste into renewable energy.

Smithfield Foods, one of the country’s largest meat-processing companies based in Smithfield, Virginia, announced plans in October 2018 to implement “manure-to-energy” projects across 90 percent of its hog spaces in North Carolina and Utah. As part of evolving sustainability efforts, Smithfield plans on converting existing anaerobic treatment lagoons to “new covered digesters to capture biogas,” which will be transported to central processing facilities and converted into renewable natural gas in North Carolina, Missouri and Utah.

Protecting pork

Archer has been a hog farmer for more than 40 years. In fact, she met her husband on a pig farm. Together, they’ve raised hogs in four different countries and four different states.

Archer is originally from upper Michigan, where farmers can’t rely on treatment lagoons to manage waste because of the colder temperatures. She says in the Midwest, farmers can’t manage and treat waste outside away from the animals, and she’s grateful to be in a more temperate climate that permits it.

Despite the benefits of anaerobic treatment lagoons, North Carolina’s pork industry faced scrutiny from media organizations after Hurricane Florence, in part because of the environmental impacts linked to overflowing lagoons.

Andy Curliss, CEO at the North Carolina Pork Council, which advocates on behalf of the state’s pork industry, recently wrote a blog about the real “threat” of Hurricane Florence, pointing to misleading headlines about the damage caused by these waste sources.

Curliss says hog farms are inevitably going to flood when affected by hurricanes, but he echoes Archer by highlighting the industry’s “significant steps” taken since Hurricane Floyd to lessen environmental impacts, including closing farms and lagoons in most flood-prone areas.

After Hurricane Florence, the DEQ’s incident tracker painted a real picture of the storm’s damage. While the department reported 1,957 incidents on farms across the state, only six needed “urgent action.” Farmers at the state’s 2,000 hog farms, meanwhile, took action to resolve prospective issues before they became critical.

In the aftermath of the storm, hog farmers in Wayne County eventually returned to their daily operations. Despite the unpredictability of when the next hurricane might impact the area, Archer says she is sure the community will be prepared.

“Our job is taking care of those animals,” Archer says. “It doesn’t matter what the weather is doing.”

The author is a digital editor for Waste Today and can be contacted at kmaile@gie.net.

Regardless of how long a driver has been on the road, unexpected issues are sure to arise. Even drivers with the most experience may not be fully equipped to handle split-second decision-making, from maneuvering a truck with a blown-out tire to dodging a child who darts into the street. But thanks to steadily advancing training technologies, drivers can now get those critical experiences without ever having to step foot out of the station.

Commercial driving simulators, now available for a range of truck types, can put a driver in nearly any road situation to provide both real-time feedback and data for ongoing improvement. It’s a piece of technology waste fleets are beginning to put to use, and for a good reason—it has the potential to save not just time and money, but also lives.

“Some of our customers have seen anywhere from a 30 to 60 percent crash rate reduction with the simulator training,” says Matt Derby, the marketing manager for L3 Driver Training Solutions, a branch of the New York-based L3 Technologies that supplies driving simulators and training to haulers. “I’d rather have somebody fail and learn 100 times in here and get it right than even one time out on the road with an actual vehicle where people are getting hurt or equipment’s getting damaged.”

In 2017, the fatal incident rate for waste collection workers was 10 times higher than the industry average, according to the Bureau of Labor Statistics (BLS). In an industry that remains the fifth deadliest in the U.S., fleet managers looking to train drivers efficiently while minimizing damages and injuries may find a solution in simulation.

Custom training

Modern driving simulators are stunningly realistic, some comparable to an amped-up, immersive version of Grand Theft Auto complete with hypersensitive reactions to every movement. The latest simulators mirror nearly every piece of equipment present in a truck cab, including a driving seat, force-loaded steering wheel, brake and accelerator pedals, a clutch and shifter for multi-geared transmissions, various gauges, and even heating and air conditioning controls. Some include three-panel setups with a screen on each to give drivers a 180-degree field of vision not only of the road in front of them, but also of their peripheral views through two door windows and simulated side mirrors. In addition to the realistic cab, managers can program specific truck specs, like height and weight, into the simulators so they react to each movement the same way a real truck would.

The technical setup prepares drivers for the seemingly infinite number of scenarios they can encounter during the simulation. Those in charge of the training can integrate a number of challenges into the course: navigating a steep, gravelly hill in a downpour without tipping the truck; moving through crowded city streets on a snowy evening; steering around people that dash into the street; even maneuvering a fully loaded truck with a popped tire quickly off the highway. Fleet managers can program every detail into the course, down to the individuals standing on street corners. Drivers feel every bump, curb and puddle along the way.

“It’s about building up those positive habits behind the wheel and really providing an experiential training environment,” Derby says.

The mighty customization potential results in a targeted training tool that can improve both skill and efficiency. Fleet managers who conduct regular safety training can use simulators to home in on specific skills or route challenges. One session, for example, may focus on space and speed management, while another may focus on defensive driving. Most simulators offer a wealth of data, allowing managers to monitor speed, stopping distances, performance in key areas and more, which can help them target and improve on problem areas for individual employees.

Simulators also offer a consistent training option that doesn’t require having to pull every driver into a room at once. “Obviously most of your fleet, they need to be out on the road doing routes ... and you don’t want to take up too much of their time. So it’s a great tool for being able to rotate through training throughout the year, and it’s a lot more effective at assessing how safe drivers are out there,” Derby says.

Training for all skill sets

Simulators can be an effective training tool for all employees, no matter their experience level. Fleet managers can use the simulator to screen new drivers for a baseline measurement of their driving capabilities. They can also use it as a pre-screening tool when conducting interviews and deciding who to hire.

Along with regular targeted training for employees, the technology can even be used to turn negative situations into learning experiences. If a driver gets into an accident on the road, fleet managers can completely recreate the scenario in the simulator to go over best practices and how the incident could have been avoided. The course can become a teaching tool not just for the driver involved, but also for the entire fleet, Derby says.

Even veteran drivers can benefit from regular training with a simulator. Derby says when L3 representatives conduct training sessions at customer facilities, drivers of all abilities walk away learning something, from new hires to seasoned drivers. “You may have a veteran driver out there that’s been on the road for 30 years. They may think they’re hot stuff ... but I guarantee you there’s always something that we can throw at million-mile drivers that they haven’t [seen yet]” Derby says.

Safety pays

Regular training with the simulator can result in major safety improvements. The technology exposes drivers to a string of dangerous situations that would be near impossible to stage in real life without putting them in harm’s way. Repeat exposure to these situations can help the driver internalize and better handle them out on the road, leading to a reduction in incidents. Even for those uncontrollable situations, Derby says simulation training can often help lessen the impact.

“There’re situations out there where the driver won’t have complete control. But the big thing is, can you minimize it? Can you bring down the severity of it so it doesn’t cost as much?” Derby says.

While the technology isn’t cheap—L3’s simulators, for example, start at more than $100,000 a piece to purchase without any additional add-ons—the resulting safety improvements could reap major financial savings. Beyond the savings earned by maintaining safe employees and minimizing their downtime, training on simulators can also be easier on equipment. Fewer accidents mean fewer repairs for trucks. Training on the simulator can even result in employees driving more fuel-consciously if efficiency in that area is emphasized during training.

If an employee is involved in an accident that results in litigation, simulation training can even be a major benefit in court. Derby says companies can use the simulator’s training records in their defense to point to the measures they’ve taken to avoid collisions, which could potentially help diminish sanctions.

As simulation technology becomes more mainstream and developed for niche markets, its presence in the waste management sphere is sure to pick up. When used in combination with in-person training sessions and on-the-road experience, driving simulators can take collection safety to the next level.

The author is the assistant editor for Waste Today magazine and can be contacted at tcottom@gie.net.

Sixty-two percent of states, as well as the District of Columbia, Puerto Rico and Guam, have legalized medical marijuana use. In conjunction, the number of people using marijuana in the United States is rising rapidly. As a Schedule I narcotic under the federal Controlled Substances Act, marijuana is still illegal, but its widespread use by workers and potential employees poses significant legal and practical issues for employers.

In addition to its increased use and acceptance, the drug has become more potent (almost double the active ingredient THC, or tetrahydrocannabinol, is present in today’s strains than was found in the drug decades ago), resulting in stronger effects that last longer. No reliable metric is available for determining when a particular level of THC impairs the user and for how long, but studies show that it stays in the body much longer than alcohol.

Waste and recycling companies have always made safety a priority. With marijuana legalization spreading, they face new concerns on how employees’ use of marijuana impacts the workplace and whether the effects are linked to job accidents and injuries. Short-term effects of the drug can include impaired body movement, difficulty thinking and problem-solving, memory issues and an altered sense of time, all of which could be detrimental to workplace safety.

Legal implications

The legal landscape is hard to define because most states are still determining regulations regarding marijuana sales, production and use. In states where the consumption of cannabis is legal, the courts’ opinion of applicable employment law and the responsibilities of employers related to workers’ marijuana use vary greatly. For waste and recycling company owners and managers, it is a confusing landscape indeed, but one that cannot be ignored.

Previously, the courts typically agreed with employers that didn’t want to hire marijuana users, citing that it was illegal under federal law. As of late October 2018, however, nine states specifically ban employment discrimination against medical pot users. Other state courts have ruled that employers may take action against an employee who has tested positive under the employers’ substance abuse policy. However, in three states, a positive drug test alone does not indicate impairment and cannot be used as the sole reason for disciplinary action.

While companies may use the federal Drug-Free Workplace Act (DFWA) as guidance for pre- and postemployment drug testing, DFWA does not require employers to conduct drug testing or to fire employees who test positive for marijuana. DFWA doesn’t provide meaningful guidance on medical marijuana use, and clarity is lacking around the use of drug test results.

To further the confusion, the U.S. Department of Justice allows states to enforce narcotics laws that are considered “outside federal priorities.” This allows states to enforce marijuana laws as they wish. While the drug is not considered for accommodation under the federal Americans with Disabilities Act, controversy surrounds the issue of accommodation for employees who are prescribed medical marijuana.

Because of the variances among the states and few standards for enforcement, waste and recycling companies in states with medical marijuana laws should be familiar with protections for employees and potential hires.

Whether to drug test

Companies that use drug testing services are likely reporting higher numbers of positive tests for marijuana in pre- and postemployment drug screens.

State laws legalizing marijuana do not completely protect employees who are under the influence while at work. The type of work being performed is an important factor. Equally important are state laws that affect how and when drug tests are conducted, the use of the test to determine impairment and the actions an employer can take. Owners and managers should consider these questions when determining their drug testing policies:

What is state employment law concerning current and potential employees who have a medical marijuana prescription?

You do not want to appear discriminatory by denying a job to someone who may be protected in states that have legalized marijuana. However, because legislation regarding employer policies varies from state to state, there is no one-size-fits-all rule. Company owners, managers and HR staff must be aware of changes to employment law.

Are your company’s jobs safety-sensitive? Are positions federally regulated?

If your business uses truck drivers who are regulated by the U.S. Department of Transportation, you are likely required to test for all illegal drugs. If the job requires working around balers or shredders or operating mobile material handling equipment, it would be in your best interest to test for impairment, even if marijuana is legal within the state.

Do you want to continue to perform drug tests?

Recently, employers have moved to exclude marijuana from mandatory drug testing because of tight applicant pools and the lack of clear guidelines on what constitutes impairment. Employers should determine if a given job requires drug testing. Companies should review their procedures and determine which approach is best under their states’ laws.

Has your substance abuse policy been reviewed to ensure it is still appropriate for your business and employment situation?

State laws legalizing marijuana use do not require employers to compromise workplace safety. Employers should make sure their policies reflect the steps that need to be taken to meet their obligations to consider employee rights while guarding workplace safety. Your guidelines, stated in the employee handbook and in the company’s substance abuse policy, will help employees and supervisors understand that state law might not protect them from consequences of being impaired on the job.

This article ran in the January issue of Recycling Today, a sister publication of Waste Today. The author is a certified executive coach who also has held HR and management roles. She can be contacted at mbd1945@aol.com.

Landfill gas (LFG) is typically about 50 percent methane, making it the chief component present in emissions. This gas can be monitored and used to determine how much LFG a site is emitting, both directly as methane and as a surrogate for total emissions.

Methane can be monitored above the surface of the landfill as a gauge of potential emissions or can be directly measured using techniques that test for the rate or flux of emissions.

The above-surface monitoring techniques for gauging potential emissions include surface emission monitoring, ground-based or low-altitude imaging and satellite and aerial imaging.

Surface emission monitoring

Surface emission monitoring (SEM) is a technique that involves using a portable methane meter near the landfill’s surface to measure concentrations while traversing the site.

SEM is a requirement under the federal New Source Performance Standards (NSPS) for landfills generating more than 50 megagrams per year of non-methane organic compound (NMOC) emissions; however, the U.S. Environmental Protection Agency (EPA) recently changed the NSPS regulation to require monitoring for facilities generating 34 megagrams per year. California also has SEM requirements for landfills, which are more stringent than the EPA’s. The California regulation requires more extensive monitoring and a lower methane concentration limit.

The EPA and California regulations set standards for how the monitoring must be performed. Critical factors in determining the requirements are the spacing of the pathway used in the monitoring, the inclusion of integrated (average concentration across a grid) monitoring in addition to instantaneous monitoring, the action level for emission reductions, the monitoring of cover penetrations (e.g., gas well locations) and the frequency of monitoring.

The EPA requires monitoring using a serpentine pathway with 30-meter intervals. California requires much tighter spacing of 7.6 meters (25 feet).

Instantaneous monitoring is monitoring of the methane concentration at the landfill surface at a single point and time. Instantaneous monitoring provides a picture of localized methane emission locations. Integrated monitoring, on the other hand, is the aggregation of the methane readings for a specific area of the landfill. Instantaneous and integrated monitoring can be performed simultaneously, though it requires additional data processing.

The new NSPS and the California regulation both require monitoring cover penetrations such as wellheads, vents and posts that pass through the cover of the landfill (the older NSPS rule does not require this). These penetrations are potential points where LFG can flow to the surface with less resistance than passing through other areas of the cover.

Finally, both the EPA and California regulations require monitoring on a quarterly basis. The California regulation allows less frequent monitoring if several conditions are met, but the NSPS does not allow less frequent monitoring except for closed landfills that meet certain criteria.

The cost of implementing the California requirements is roughly three times higher than implementing EPA requirements due to the tighter path spacing, additional equipment and processing requirements and the need to monitor cover penetrations. The costs for large sites scale roughly proportionately with the site’s area, and costs for small sites (smaller than 50 acres) are driven by fixed costs such as mobilization, equipment and reporting rather than the size of the site. Costs can range from several thousand dollars to more than $10,000 per event.

Ground-based or low-altitude imaging

Infrared (IR) cameras let you see frequencies that the human eye cannot, including frequencies where methane is visible. IR cameras are already used by the oil and gas industry to look for leaks along pipelines and at facilities, but they are not commonly used in the solid waste industry where there may be application-specific challenges. Other imaging technologies, including hyperspectral imaging and thermal imaging, are also available, but IR imaging is the most prevalent.

Methane can be emitted by a landfill both from the landfill surface and from the LFG collection and control system (GCCS) components. Methane leaks from oil and gas facilities tend to be localized hot spots, like seams and holes in equipment, and leaks from the landfill GCCS would be comparable. Methane from the landfill surface would be emitted from a larger area and would not necessarily have the same contrast with the surrounding methane concentration as a pipeline leak.

IR cameras could be used by landfill personnel to look for large methane sources. Adapting the technology and techniques used in the oil and gas industry to landfill GCCS systems seems straightforward, but it remains unclear whether the technology can be adapted to look for surface emissions in a way that is less expensive or more effective than SEM.

IR cameras can be mounted, handheld or drone-mounted, which allows for versatility and widespread use. Drone-mounted IR cameras have the potential to monitor areas where personnel are not available or that cannot be safely accessed; however, IR cameras may not be good at pinpointing methane emission sources, and personnel will be required to have access to the location to remediate emissions in question.

Equipment and monitoring costs can range from the high thousands of dollars range to tens of thousands of dollars per event. As technology improves, IR technologies may be able to see and accurately quantify low concentration leaks as these tools become more cost-effective.

Satellite and aerial imaging

Satellite and aerial imaging require using imaging technology similar to IR cameras or spectrometry to detect methane from a much higher elevation than commercial drones can. Satellite or aerial imaging can provide a measurement of methane emissions from very large sites or for entire regions.

In 2016, satellites were able to detect emissions of the methane gas leak from the SoCalGas Aliso Canyon facility, which is a large natural gas facility in Los Angeles County. Those images were gathered by both aircraft and satellites. Similar high-altitude imaging could be used to get a picture of the methane emissions at landfills. Some studies in Southern California have detected large landfills via emissions with this high-altitude imaging. However, due to the distance and scale of the imaging, it is not suitable for finding point emission sources at landfills at this point. This remote imaging does not currently provide a reliable quantitative estimation of methane emissions or concentrations, but research and methodologies are being developed to establish quantitative measurements.

Additionally, high-altitude imaging is too expensive to be used for regular monitoring of individual sites, with costs ranging from the high tens of thousands to mid hundreds of thousands of dollars per event. This technology is primarily useful as a research tool to determine methane emissions from a region with a number of methane sources. It is not as practical as and is much more expensive than using a handheld or drone-mounted IR camera for the monitoring of individual sites.

Recommended approach for landfill monitoring

With the number of monitoring technologies out there, it can be difficult for operators to distinguish which is best.

SEM is a well-demonstrated and proven monitoring strategy for assessing landfill emissions. SEM requirements can be balanced to achieve cost-effective monitoring by adjusting the monitoring path spacing and the action level for required remedial action.

IR imaging is a promising technology. Although it is not as robustly demonstrated for landfill application, it should be considered an alternative or complement to SEM. IR imaging has the potential to quickly identify high-methane emission points on landfills that could potentially be missed by SEM, while SEM has the ability to quantify the concentration of methane accurately at such hot spots. These technologies work well in concert, but the combined costs may make them prohibitive for individual sites.

Although satellite and aerial imaging offer promising data, they aren’t comprehensive enough yet for practical use. These limitations, in addition to cost, disqualify satellite and aerial imaging methods in favor of more traditional LFG monitoring technologies.

Direct methane measurement

Landfill methane measurement is the direct measurement of methane emissions from landfills. Direct measurement of methane is much more expensive than SEM. Four ways to measure landfill methane directly are flux chamber testing, plume measurement, micrometeorological methods and dispersion modeling

Flux chamber testing

Flux chamber testing measures methane flux (mass emissions per area) at points on the landfill surface using flux chambers. Flux chambers are small (typically around 1 square meter or less) half-open chambers that are placed on the surface being sampled. The total area sampled by flux chambers is only a small fraction of the overall landfill area, so flux chamber testing must include a method to extrapolate isolated flux measurements to site-wide emission rates. Flux sampling methods are generally standardized, but there are no industry-accepted standardized methods for the extrapolation of site-wide emissions.

The EPA published a method for determining the number of required samples and sample locations (Radian 1986), but the number of samples required for even a small landfill is impractical.

Plume measurement

Plume measurement methods use ground-based optical sensors to measure the methane plume coming from the landfill. Those plume measurements are then used to calculate the landfill’s methane emission rate. There is currently no widely used standardized optical sensor method. The EPA has published Other Test Method 10 (OTM 10), but the method has been found to be unreliable, with poor accuracy and poor repeatability. Over the last several years, the EPA has moved away from the use of OTM 10 for determining methane emissions from landfills.

Due to the high cost ranging from the high tens of thousands of dollars to mid hundreds of thousands of dollars per event, specialized requirements, poor accuracy, poor consistency and poor repeatability of results in studies done to date, plume measurement methods like OTM 10 are not recommended for quantification of methane emissions from landfills at this time.

Micrometeorology methods

Eddy covariance and similar methods are emerging as the current practice for measuring methane plumes. While eddy covariance appears to be the most common practice, similar methods, such as eddy accumulation and the Bowen ratio, may find similar application.

In eddy covariance, the concentration of methane is measured using an infrared laser at multiple elevations above the landfill surface while collocated meteorology data are collected. The measurements are used to calculate the methane emission rate from the source. Micrometeorological methods are generally superior to plume measurements because some equipment packages can remain in place and provide regular monitoring over extended periods with more consistent results. Commercial sensor and software packages are available for turnkey micrometeorological monitoring installations.

Eddy covariance is well demonstrated in applications outside the landfill industry, but costs for this method are in the low to mid-hundreds of thousands of dollars per site, which make it impractical for most sites. However, this may be practical for research purposes or other special cases.

Air dispersion modeling

Air dispersion modeling can be used to determine emission rates from landfills. This method monitors on-site and/or downwind methane concentrations using a dispersion model to calculate methane emissions from the landfill.

The methane monitoring must be contemporaneous with the collection of modeling-quality meteorology data. The methane monitoring is typically more expensive than a typical SEM event due to the collection of meteorology and location data during the monitoring event. Ongoing, near-real-time monitoring requires advanced monitors for methane and meteorology, significant automated data management and sophisticated data processing to quickly process meteorology.

Calculation of methane emissions using dispersion modeling is not required by regulation, though it has been used to demonstrate regulatory compliance in California. No standard method for reverse modeling has been developed, but methods have been proposed (Huitric and Kong, 2006). Air dispersion models generally provide conservative downwind concentrations, which are necessary when using the models to demonstrate compliance with air quality standards; however, the conservative results could lead to an underestimation of methane emission rates.

Dispersion models, and AERMOD in particular, can be inaccurate when modeling impacts very close to area sources, such as landfills. Air dispersion modeling costs will be in the high tens of thousands of dollars to low hundreds of thousands of dollars per event.

Recommended approach for landfill measurements

The cost of directly measuring methane emissions from landfills does not justify widespread adoption of any of the methods discussed for regular use. The direct measurement methods cost two to three orders of magnitude more than typical SEM events. However, the methane measurement methods are useful in research applications or on a case-by-case basis to demonstrate site-specific emissions.

Pat Sullivan is the senior vice president of SCS Engineers and can be reached at PSullivan@SCSEngineers.com. John Henkelman is a senior engineer at SCS Engineers and can be reached at JHenkelman@SCSEngineers.com.