The pandemic situation has generated a lot of interest and activity in UV disinfection, which has been keeping me busy. Whether it’s for masks, air, surfaces or whatever, there are lots of things getting posted and promoted for using UV. There seem to be an overwhelming number of devices and designs being suggested or sold online. Unfortunately there are also a lot of misconceptions, errors and possibly fraudulent claims being promoted. I’m not going to try and address each and every device (there are too many!), but I can provide some basic ideas that one should know or ask about when considering UV devices. If the supplier can’t readily provide answers or details, then something is possibly wrong. Here are a few key confusing points:Continue reading
Schools of all sorts are looking for ways to re-open while minimizing coronavirus transmission risks. Harvard University’s School of Public Health recently issued a downloadable document on “Schools for Health”. In it they suggest a number of administrative and engineering approaches for reducing virus transmission in a classroom and school setting. It’s interesting and worth a look.
Since I teach and do research in some aspects of HVAC (Heating Ventilation and Air Conditioning) and indoor air quality, those parts of the report caught my attention. They are suggesting that people consider using portable air cleaners in the classroom, especially in situations where the HVAC is non-existent or poor. They don’t give a lot of numerical detail behind that recommendation, but it’s fairly easy to work it out. So I’ve done some quick calculations to see where air cleaners might be useful from a more quantitative perspective.Continue reading
Here’s a nice summary article about aerosol viral transmission, by a mechanical engineering professor. The physics of aerosols is a foundational concept in air pollution control.
Recent pandemic developments have strained the supply of N95 filtering facepiece respirators (FFRs), which protect users from particles and aerosols in the air that they breathe. Technically, they must filter out at least 95% of 0.3 micrometre particles.
Normally these are meant to be single-use devices, and are removed and disposed of in a secure way to prevent infection transmission. However, with supply shortages people are considering or resorting to re-using these FFRs, possibly with some sort of chemical or physical disinfection process. Disinfection processes are never 100% effective, so this is not a great option, but I guess it’s better than having no protection.
One disinfection method that I’m very familiar with is UV-C disinfection, having done research in the area of photochemical processes for several decades. There is published literature available demonstrating reasonable disinfection success for UV when applied to N95 FFRs, so this may be an approach to consider if necessary.
I’m working on an overview of this literature (draft version now available at this link), but I’m happy to consult (pro bono) with health care institutions that are considering UV applications to deal with their situations (firstname.lastname@example.org).
With the recent development of a viral pandemic, people are being reminded about the importance of handwashing for infection prevention. Coincidentally, in 2019 my colleague Prof. Marc Aucoin and I supervised a research study on handwashing for the CSA Group, a product standards organization. Specifically, our study aimed to determine if the faucet water flow rate had a significant effect on the ability of handwashing to remove bacteria from the skin.
You can access and read the full report on their website. The bottom line is that no, the water flow rate from the faucet didn’t have a significant effect over the range we tested, from 0.5 to 2.2 gallons per minute (about 2 to 8 litres per minute). Under all of those flow rates, on average about 99.3% of E. coli bacteria would be removed from the hands, which is good to know.
To do this study, we had to control all the other variables as much as possible, including the water temperature, and the amount and type of hand soap used by each person. The other big factor is the way that the hands were washed, including the length of time. For this study, we used a certain protocol from Public Health, and everyone involved in the study learned how to properly wash their hands. This was a good learning opportunity for people, including me, and so I reproduce the protocol that we used below. It’s a useful skill to know how to thoroughly wash your hands these days.
For the sixth year, I’ve been helping organize the “Resource Recovery Partnership” conference in collaboration with industry, government, and academic colleagues. This year’s event is on Thursday September 19, 2019, and registration is free for either in-person or webcast attendance. The final agenda is available, and anyone interested in the ideas behind sustainable materials, recycling, circular economy, zero waste, or materials and energy recovery might want to attend some of the webcast sessions. There are a range of speakers and panelists covering various aspects of policy development, technologies, and current statistics and trends. The talks are not highly technical, and anyone could benefit from some of the insights available here.
As our landfills (and oceans) fill with wastes, it has become clear to most people that solutions are needed to reduce wastes and to recover some value from the remaining waste materials. This is easier said than done, and requires a comprehensive approach incorporating technology, smart policies, economic drivers, and societal buy-in. These conferences have tried to bring together people from a wide range of backgrounds and interests, to try to advance progress in waste reduction. It’s a long and slow progress, but momentum seems to be building around the globe.
Autism, or more accurately Autism Spectrum Disorder (ASD), is in the news and public view a lot in recent years. According to some recent reports, it is now diagnosed in 1 out of 68 children (1.47%) in the U.S. Reasons for the apparent increase in diagnoses over recent decades are complex, but they lead us to wonder what is happening and what are the causes?
Recent scientific literature suggests that the specific causes are largely unknown, but there is a very strong genetic component (heritability of 80%). Unfortunately, even the genetic aspects are very uncertain and probably highly complex, not just a simple set of genes like the ones that determine your eye colour. Although genetics may play a large role, there are also indications that environmental factors are involved, perhaps in some sort of interaction with the genetic factors.
The popular and social media keep going in circles about vaccines, a factor for which there is no reliable scientific evidence at all. At the same time, there seems to be complete ignorance of a growing body of scientific literature linking ASD with air quality. A quick search through peer-reviewed scientific literature using the Scopus database shows at least 160 papers that mention “autism and ‘air pollution'” somewhere in the publication over the past 20 years.
I don’t know a lot about ASD, but I can comment on air pollution and so here I’ll discuss what I see from some of this literature. Much of the research literature is only fully available if you have access to a university library (like me), but I’ll try to provide some links to at least the summary or abstract of the studies. Much of this literature is highly technical however, so don’t worry if it’s not so easy to digest.
An interesting news story about the measurement of air quality on cruise ships appeared recently. Specifically, it dealt with the concentration of ultrafine particulate (UFP) matter in the air on four cruise ships, measured by a researcher from Johns Hopkins University. UFP is invisible matter with diameters of around 100 nanometres (nm), which is about 1,000 times smaller than a human hair, and it is implicated in airway inflammation and effects on other organs in the human body. Being interested in air quality, I looked up the actual study report which you can also read here. Here is my take on the work and meaning… Continue reading
With recent moves to permit sales of cannabis in Canada and some U.S. states, commercial operations are popping up in various locations. Whenever new industries emerge, there are often new environmental impacts to consider and air pollution seems to be an increasingly common problem with cannabis too. Not from smoking, but rather from the greenhouse operations where it is grown under lights in high-density conditions to save space. It turns out that these intensive grow operations can have vented air emissions that are rather smelly, as this one news item describes.
Like all plants, cannabis emits volatile chemical compounds at various stages in its growth. Some work has been reported in research literature, identifying over 200 chemicals in the air, although I suspect that paper missed a lot of odorous sulfur compounds that are often associated with “skunky” smells. A lot of the odor compounds are terpenes or their relatives (e.g. limonene, pinene, linalool), and the paper mentions cymene, benzaldehyde, nonanal, and decanol as key odor chemicals. None of these compounds are particularly hazardous (at least at the normally low concentrations found around plants). None of them are specific to cannabis either. Lots of them are produced by various plants, in varying amounts and combinations. A lot of plant-based essential oils that you can buy contain similar chemicals.
The environmental issue arises if the odor interferes with the neighbouring property and their ability to use and enjoy their property. The Ontario government website has some information about odors and property-owner rights . Under Ontario’s Environmental Protection Act (Section 14) odor-emitting industries can get into legal trouble because they are emitting a “contaminant” that causes an “adverse effect”.
From an engineering point of view, the control of odorous emissions like this is not unlike many other industries with odour concerns, like sewage treatment plants, rendering plants, some food manufacturers, and some chemical manufacturers. The first step is containment, so that odor emissions are not just leaking out of the buildings from a multitude of locations. If everything can be efficiently captured in one or two well-controlled ventilation systems, then emissions controls can be applied to those vent streams before they discharge into the environment.
It’s not clear at this point what type of emission controls are best for both efficiency and cost points of view. Usually there are several possible solutions, so engineers have to figure out which one is the most cost-effective. Standard approaches to odor control run a range of technologies from wet scrubbing to activated carbon capture, to biofiltration and possibly photochemical oxidation. High temperature thermal oxidation is another option, but probably overkill and too expensive for this application. One solution may not fit all commercial operations either. Each location would need a thorough engineering analysis and assessment for a good recommendation, which is something done by chemical and environmental engineers (and some mechanical engineers too). Companies that rushed into production without doing these assessments may get stuck with expensive retro-fits once the Ministry of Environment comes knocking.
So, with every new “industry” there are issues that come up that may or may not have been anticipated by the business people. Those issues will keep regulators and engineering consultants busy for a while.
Some interesting results from my colleague’s research group. I add some further context below the link…
Researchers at Waterloo Engineering have created a powder that could be used to reduce greenhouse gases at factories and power plants that burn fossil fuels. The advanced carbon powder, developed using a novel process in the lab of chemical engineering professor Zhongwei Chen, could filter and remove carbon dioxide (CO2) from emissions with almost twice the efficiency of conventional materials.
My Context/Analysis: Some interesting work in materials science and chemistry. From the published paper (sorry it’s behind a paywall, but I can read it through the university’s subscription), I can see that the amount of CO2 captured is about 1.6 mmole of CO2 per gram of powder, or about 70 mg/g, at flue gas conditions. As the paper points out, this is pretty good for CO2 adsorption, but it is not a miracle cure for all of our problems. To put it in context, in 2016 the U.S. electricity sector emitted something like 1,800,000,000,000 kg of CO2 (from the EPA website). So, if the powder can capture 70 mg per g it would take about 26,000,000,000,000 kg of powder for one year of capture. That’s a lot of powder!! And that’s only for one sector in the U.S. alone (representing about 28% of U.S. CO2 emissions). So, it’s important to continue doing research, find new things and look at potential applications in a wide range of fields. But carbon emissions and climate change is a huge problem and there aren’t any easy answers. Reducing CO2 emissions will generally be better than trying to capture them afterwards, like the three R’s hierarchy (reduce, reuse, recycle).