Silicon Valley’s smell problem is forcing cities to treat odour like a measurable pollutant
Milpitas, California, is better known for semiconductor campuses and high property values than for the smell drifting in from a nearby landfill. Yet for years, residents living close to Newby Island landfill have complained of a persistent stench that can linger for hours each day. One resident, Chia-Ling Kong, said she could not open her window for more than 10 years after moving there, a reminder that environmental exposure is not limited to smoke, soot or water contamination. Odour can alter how people use their homes, how they sleep and how they judge the safety of their neighbourhood.
Local authorities have ordered the landfill operators to deploy drones, install monitors and automate the capture of landfill gases linked to the smell. The move reflects a broader shift in how communities are trying to manage nuisance odours: less by relying on complaint logs and subjective impressions, more by using real-time chemical data. For residents, the appeal is straightforward. If the nuisance can be measured, it can be tracked. If it can be tracked, it may be harder to dismiss.
The challenge is bigger than one landfill. Across cities and industrial corridors, complaints often center on waste sites, sewage treatment plants and food-processing facilities. These are not abstract irritants. They are daily exposures that can shape quality of life, spark conflict between residents and operators, and trigger repeated calls to local agencies. In places where national rules are thin or absent, the problem falls to state and municipal authorities, which have to decide how to investigate a smell that may have no visible plume and no single obvious source.
Real-time sensors are replacing nose-by-nose inspections
Des Moines, Iowa, offers one of the clearest examples of how the response is changing. Residents there have long complained about the so-called Eastside Funk, a foul odour drifting over parts of the city. A study commissioned by city authorities linked a cluster of industrial meat companies to the problem. The city now spends about $240,000 a year on technology to track the smell, using a ring of odour monitors around the facilities believed to be involved.
The system combines air monitors with a weather station, allowing officials to match chemical readings with wind direction and estimate which facility is responsible for a given odour event. In practical terms, this matters because it moves the argument away from anecdote. Complaints no longer depend solely on when an inspector arrives or whether a municipal worker happens to catch the smell on the right street. The data can show whether emissions are coming from a specific site and whether atmospheric conditions are carrying them toward nearby homes.
A single wind shift can push an odour plume across a large part of a city.
For a public nuisance that has been notoriously difficult to localize, that kind of attribution is powerful. It can also change the conversation with operators, some of whom have invested heavily in control systems of their own. Smithfield Foods, which operates a meat processing site in Des Moines, says it has spent $2 million on a regenerative thermal oxidiser, a system designed to destroy odour-causing chemicals. Even with those upgrades, the company says it does not believe it is the source of the complaints. The gap between corporate claims and community experience is exactly where environmental monitoring becomes valuable.
Why odour is so hard to control at landfills and waste sites
Experts interviewed for the article describe three broad approaches to industrial odour control: absorbing compounds, converting them through chemical reactions or burning them away. When these methods are applied correctly, the best systems can remove 90% or more of the target compounds responsible for bad smells. But effective treatment is not cheap, and landfill operators often choose lower-cost measures instead. One common shortcut is masking, in which large quantities of deodorising spray are released to cover up the smell.
That strategy is met with deep skepticism from specialists. Micheal Bull, an odour consultant, compared such sprays to fabric conditioner, arguing they are unlikely to change the underlying odour problem. Carlos Diaz, an environmental consultant in Spain, called landfill one of the most difficult sources to treat because of the sheer size of the surface area involved. Unlike a factory stack or a single vent, a landfill can emit from multiple points across a broad expanse, making capture and treatment technically and financially demanding.
The biology of smell helps explain why these disputes become so heated. Odour is not just about concentration; it is also about how a mixture of compounds is perceived by the human nose. Some compounds may be faint at one level but intensely offensive at another, and repeated exposure can sharpen public sensitivity. Johan Lundström, a professor at the Karolinska Institute, pointed out that the more unpleasant people perceive an odour to be, the more sensitive they may become to it. In other words, annoyance and perception can intensify one another, which is one reason complaints often persist even when operators insist conditions have improved.
Electronic noses are giving cities a more objective tool
In Des Moines, the monitoring program now relies on devices described as electronic noses, supplied by the company Kunak. These sensors measure the levels of chemical compounds in the air and can be paired with weather data to build a time-stamped picture of what is happening around a site. Claudia Barrios Obregón of Kunak said many cities still rely on olfactometry, where a human panel judges an odour and assigns an opinion to it, but she argued that this approach is limited. Human perception is variable, and a panel can only sample a fraction of the moments when residents are actually exposed.
Electronic monitoring does not eliminate uncertainty, but it narrows it. It gives city officials a way to investigate complaints with more precision, and it gives operators a clearer target when they are asked to fix emissions. That can reduce the cycle of denial and frustration that often defines odour disputes. It also creates a record that can support enforcement action when a facility repeatedly produces measurable emissions tied to nearby complaints.
Milpitas is now trying to follow that logic. The landfill there has been ordered to use drones and automated gas collection systems, with the goal of identifying odour sources more quickly and reducing the releases that reach surrounding homes. The operators say they are committed to safe operations and protecting air quality. For residents, the real test will be whether the data translate into fewer days when windows stay shut and outdoor life is disrupted.
What is still unresolved is how many communities will get access to this kind of monitoring, and how many will continue to live beside odour sources that are regulated only loosely, if at all. In the absence of stronger rules, the fight against stench may depend less on broad environmental policy than on whether local governments can afford the sensors, the staff and the enforcement tools to act on what the monitors reveal.