Image source, The Mercury News via Getty Images Image caption, The operators of Newby Island landfill have been ordered to take action over odours
Milpitas, an affluent city in California's Silicon Valley tech hub, has an odour problem.
For decades, residents have had to endure rank smells wafting from industrial sites, among them a 342-acre landfill.
"When I first moved here, I could not open my window for over 10 years," says Chia-Ling Kong, an engineer for a tech firm who lives around half a mile from the dump.
While things have got better in recent years, Kong says she and her neighbours must still contend with around "two or three hours of bad smells a day".
Perhaps befitting Silicon Valley, the community is putting its hopes in technology.
The operators of Newby Island landfill have been ordered by local authorities to use drones and install monitors to systematically track and measure the chemicals responsible for bad odours. They have also been told to automate the collection of landfill gases responsible for smells.
Kong is optimistic a data-driven approach will make a difference. "Hopefully with this continuous monitoring, it makes it easier to pinpoint problems at the moment it starts."
The operators of the landfill say they are committed to operating it safely and protecting air quality.
Just like in Milpitas, where Kong is part of a citizen's campaign against the odours, communities around the world are raising a stink about bad smells making day-to-day life miserable. Sometimes a rubbish dump is to blame, or it might be a sewage treatment works, or a reeking factory.
When the complaints start stacking up, resolving them is not always simple. Many countries have no regulations in place dictating how to manage smells.
In the US, for example, the Environmental Protection Agency does not regulate environmental odours as a pollutant. This leaves states and local governments to take charge of the issue.
Urban sprawl is often part of the problem, bringing communities closer to stinky facilities that may historically have been kept at a distance.
This is creating more demand for technologies to monitor and prevent smells. Odour consultant Micheal Bull says people are increasingly concerned about neighbourhood stinks.
"You're getting developments being built nearer to odorous processes… as land has become more valuable, there is also infilling," Bull says. He is speaking about his experiences in the UK, but it's a similar story in many parts of the world.
Image source, Getty Images Image caption, Bad smells from waste sites are among the most difficult to resolve
The technologies used to tackle industrial pongs generally fall into three categories: they absorb odours; convert them into something less smelly through a chemical reaction; or burn them away.
Experts on fixing industrial odours say that the best technologies, when used correctly, can remove 90% or more of the target compounds responsible for smells.
But this can be expensive and some operators opt for simpler and cheaper solutions. These include masking odours from landfill or sewage processing by spraying giant quantities of deodorisers.
Odour experts contacted for this article were dubious about the effectiveness of such industrial scale air fresheners. "In my view they're not likely to change the odours," says Bull, who likens them to fabric conditioner.
Bad smells from waste sites – a common cause of complaints – are amon…