“Four minutes is too long.”

That’s the note undergraduate Chris Zuo sent me along with photos of countless mosquito bites on his bare skin. This full-body massacre wasn’t the result of a camping trip gone awry. He’d spent that limited amount of time in a room with 100 hungry mosquitoes while wearing nothing but a mesh suit we thought would have protected him.

Thus began our three-year journey trying to understand the behavior of a deceivingly simple insect, the mosquito. It may sound like a professor’s sadistic plan, but, really, we did everything by the book. Our university’s institutional review board approved our procedures, making sure Chris was safe and not coerced in any way. The mosquitoes were disease-free and native to our home state of Georgia. And this session resulted in the first and last bites anyone received during the study.

Besides my role as torturer of students, I am an author and professor at Georgia Tech with over 20 years of experience studying the movement of animals.

Mosquitoes are the world’s most dangerous animal. The diseases they carry, from malaria to dengue, cause over 700,000 deaths per year. More people have died from mosquitoes than wars.

The world spends US$22 billion per year on billions of liters of insecticides, millions of pounds of larvicides, and millions of insecticide-treated bed nets – all to fight a tiny insect that weighs 10 times less than a grain of rice and has only 200,000 neurons.

Yet, people are losing the war on mosquitoes. These insects are evolving to thrive in cities and spreading disease more rapidly with climate change. How can such simple animals find us so easily?

Scientists know mosquitoes have terrible eyesight and depend on chemical cues to make up for it. Knowing what attracts a mosquito, though, isn’t enough to predict its behavior. You can know a heat-seeking missile is drawn to heat, but you still won’t know how a missile works.

Enter Chris and his self-sacrifice in the mosquito room. By tracking the flight of many mosquitoes around him, we hoped to determine how they made decisions in response to his presence. Understanding how mosquitoes respond to humans is a first step to controlling them.

How Mosquitoes Zero In On Their Meal

Out of 3,500 species of mosquitoes, over 100 species are classified as anthropophilic, meaning they prefer humans for lunch. Certain species of mosquitoes will find the one person among a whole herd of cattle in order to suck human blood.

This is quite a feat considering mosquitoes are weak flyers. They stop flying in a slight 2-3 mph breeze, the same air speed generated by a horse’s swinging tail. In calmer conditions, mosquitoes use their minuscule brains to follow human heat, moisture and odors that are carried downwind.

Carbon dioxide, the byproduct of respiration of all living animals, is particularly attractive. Mosquitoes notice carbon dioxide as well as you notice the stink of a full dumpster, detecting it up to 30 feet (9 meters) away from a host, where concentrations dip to a few parts per million, like a few cups of dye in an Olympic-size pool.

Mosquitoes’ vision isn’t much help as they hunt for their next blood meal. Their two compound eyes have several hundred individual lenses called ommatidia, each about the width of a human hair. They produce a somewhat blurry mosaic or pixelated image. Due to the laws of optics, mosquitoes can discern an adult-size human only at a few meters away. With their vision alone, they cannot distinguish a human from a small tree. They inspect every dark object.

Gathering the Flight-Path Data

The challenge with studying mosquito flight is that, like trash-talking teenagers, most of what they do is meaningless noise. Mosquitoes flying in an empty room are largely making random changes in flight speed and direction. We needed many flight trajectories to cut through the noise.

One of our collaborators, University of California, Riverside, biologist Ring Cardé, told us that back in the 1980s, scientists conducted “bite studies” by stripping down to their underwear and slapping the mosquitoes that landed on their naked bodies. He said nudity prevented confounding variables, such as the color of a shirt’s fabric.

Chris and I looked at each other. Sit naked and wait to become mosquito prey? Instead, we designed the mesh suit that Chris originally wore into the mosquito room. But after seeing Chris’ bites, we needed a better way.

Instead, Chris washed long-sleeved clothes in unscented detergent and wore gloves and a face mask. Fully protected, Chris only had to stand and wait, while a cloud of mosquitoes swarmed him.

The U.S. Centers for Disease Control and Prevention introduced us to the Photonic Sentry, a camera that simultaneously tracks hundreds of flying insects in a room. It records 100 frames per second at 5 mm resolution for a space like a large studio apartment. In just a few hours, Chris and another graduate student, Soohwan Kim, generated more mosquito flight data than had previously been measured in human history.

Jörn Dunkel, Chenyi Fei and Alex Cohen, our mathematician collaborators at MIT, told us that the geometry of Chris’ body was still too complicated to study the mosquitoes’ reactions. Mathematicians excel at simplifying complex problems to their essence. Chenyi suggested we go easy on Chris – why not replace him with a simple dummy: a black Styrofoam ball on a stick combined with a canister of carbon dioxide.

Over the next two years, Chris filmed the mosquitoes circling the Styrofoam dummies mercilessly. Then he vacuumed up the mosquitoes, trying not to get bitten.

Deciphering the Trajectories

A mosquito flies like you would an airplane: it turns left or right, accelerates or hits the brakes. We determined a mosquito’s flight behavior as a function of its speed, location and direction with respect to the target as the first step in creating our model of their behavior.

Our confidence in our behavioral rules increased as we read more trajectories, ultimately using 20 million mosquito positions and speeds. This idea of incorporating observations to support a mathematical hypothesis is a 200-year-old idea called Bayesian inference. We illustrated the mosquito behavior we’d observed in a web application.

Using our model, we showed how different targets cause mosquitoes to fly differently. Visual targets cause fly-bys, where mosquitoes fly past the target. Carbon dioxide causes double takes, where mosquitoes slow down near the target. The combination of a visual cue and carbon dioxide creates high-speed orbiting patterns.

Up until now, we had used only experiments with Styrofoam spheres to train our model. The true test was whether it could predict mosquito flights around a human. Chris returned to the chamber, this time wearing all white clothes and a black hat, turning himself into a bull’s-eye. Our model successfully predicted the distribution of mosquitoes around him. We identified zones of danger, where there was a high chance of a mosquito circling around him.

Predicting mosquito behavior is a first step toward outsmarting them. In mosquito-prone areas, people design houses with features to prevent mosquitoes from following human cues and entering. Similarly, mosquito traps suck in mosquitoes when they get too close but still allow between 50% and 90% of mosquitoes to escape. Many of these designs are based on trial and error. We hope that our study provides a more precise tool for designing methods for mosquito capture or deterrence.

When Chris’ mother attended his master’s degree defense, I asked her how she felt about her son using himself as bait for mosquitoes. She said she was very proud. So am I – and not just because I’m relieved Chris didn’t ask me to take his place in the mosquito chamber.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Jie Wu, an engineering graduate student, was studying a type of striking white beetle found in Southeast Asia and attempting to figure out how to mimic its brilliant color when an unexpected discovery upended the experiment.

Jie and I had been hoping to identify naturally occurring whitening pigments that could be used in paper and paints. The beetle’s white exoskeleton is made from a compound called chitin, which is a type of carbohydrate – one that is also commonly found in crab and lobster shells.

First, Jie extracted chitin nanofibers from crab shells obtained from food waste that are chemically the same as those found in the white beetles. But instead of creating a white material as intended, Jie produced dense, transparent films. The nanofibers more readily assembled in tightly packed films than in the porous structures Jie desired.

On a whim, Jie measured the rate at which oxygen passed through the film. The result was astonishing: The barrier allowed less oxygen through than many existing packaging plastics.

That serendipitous finding in 2014 shifted my team of engineering students’ focus from color to packaging. We asked whether natural materials could rival the performance of common plastics. In the years since, our team has used this discovery to create biodegradable films that offer a more sustainable and effective alternative to plastic packaging.

Challenges of Plastic Packaging

Plastic packaging is commonly used to protect food, pharmaceuticals and personal care products. These plastics keep out moisture and oxygen from the air, so products stay fresh and safe.

Most packaging has several layers that work together to keep air out, but these layers hinder reuse and recycling efforts. As a result, most of this plastic barrier packaging is discarded to landfills as single-use materials.

Many researchers have sought alternatives that are renewable, biodegradable or recyclable, yet just as effective. At Georgia Tech, my team of students and post-docs has spent more than a decade tackling this problem. This journey began with that beetle.

Building a Better Barrier

Chitin is widely available in food waste and mushrooms, and it is used in products such as water filters and wound dressing. However, our early attempts to scale up the film technology based on the beetle-inspired experiment failed.

In 2018, the team made an important leap forward by using spray coating to create layers of chitin and cellulose nanomaterials. Cellulose, like chitin, is a carbohydrate polymer – a chain of repeating carbohydrate units – and it is obtained from plants. These abundant natural materials have opposite electric charges, which led to better barrier performance when we combined them than either material alone.

In this approach, the team sprayed down a layer of chitin, followed by a layer of cellulose. The opposite charges between the chitin and cellulose created a long-range attraction between them that binds the layers to create a dense interface.

Later, in collaboration with Meisha Shofner, a materials scientist, and Tequila Harris, a mechanical engineer, other students showed these coatings could be applied with scalable, roll-to-roll techniques. Roll-to-roll coating methods are preferred in industry because the coatings are applied continuously to large rolls of a substrate material, such as paper or other biodegradable plastics.

Still, humidity posed a major challenge, limiting any real-world applications. Moisture swelled the film, allowing more oxygen to sneak through.

Then came another breakthrough. In 2024, another collaborator, Natalie Stingelin, and I discovered that two common food components resisted water vapor when combined: carboxymethylcellulose – which is found in ice cream, for example – and citric acid.

The result was a film that hindered the transmission of moisture. The citric acid reacted with the cellulose to form cross-links, which are chemical junctions that bind the cellulose molecules. Once bound, they reduced the film’s moisture uptake.

We integrated this new discovery with the prior work by combining the citric acid and cellulose, and then casting this mixture as a freestanding film by coating it onto a substrate, such as chitin.

However, that formulation did not have strong oxygen barrier properties because it did not contain the highly crystalline cellulose nanomaterials from our first film. Our team’s most recent achievement, from October 2025, combines the above innovations. As a result, we’ve created a bio-based film that is an excellent barrier to both oxygen and moisture.

Scaling Up Production

When cast into thin films, these components self-organize into a dense structure that resists swelling with water vapor. Tests showed that even at 80% humidity the film matched or outperformed common packaging plastics.

The materials are renewable, biodegradable and compostable. Our team has filed several patent applications, and we are working with industry partners to develop specific packaging uses.

One challenge that applications face is a limited supply of the bio-based components compared to the high volume of conventional plastics. Like any new material, it would take time for manufacturers to develop supply chains as the films begin to be used.

For example, the market demand for purified chitin is small right now, as it is used in niche applications, such as wound dressings and water filtration. Due to its variety of uses, packaging could increase that market demand.

The next challenge is scaling up from experimental films to industrial production, which would likely take several years. The team is exploring roll-to-roll coating techniques and working with industry partners to integrate these materials into existing packaging lines.

Policy and consumer demand will also play a role. As governments push for bans on single-use plastics and companies set sustainability targets, bio-based films could become part of the solution.

The story of this breakthrough reminds me that science often advances through unexpected results. From a failed attempt to mimic a beetle’s color to a promising alternative to plastic, this research shows how curiosity can lead to solutions for some of our biggest challenges.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Every day, food scraps disappear into trash bags, are hauled away and forgotten. But that waste could be turned into something productive.

Across the United States, about 97 million metric tons of food waste are discarded each year, of which about 37 million metric tons end up buried in landfills.

Once underground, that organic material breaks down without oxygen and releases methane, a short-lived yet powerful greenhouse gas.

At the same time, the nutrients and energy stored in that food are permanently lost. But there is a better way. Research my colleagues and I conducted found that communities across the country already operate facilities designed to handle organic matter: wastewater treatment plants. Many larger, well-funded plants already have the infrastructure to process food waste, though not every plant is ready to do so today.

Landfills Are Not Designed for Food Waste

Food waste is fundamentally different from plastics, metals or glass. It’s organic and can decompose naturally. But when it’s placed in a landfill, its decomposition emits significant greenhouse gases.

Modern landfills are designed to capture the methane emitted, but even the most efficient systems still allow almost 58% to escape into the atmosphere. That food waste could be turned into energy or fertilizer, but instead it contributes to global warming.

By contrast, wastewater treatment plants process sewage using microbial communities that naturally break down organic matter. Many also capture methane produced during treatment and convert it into usable energy. Others recover nutrients such as phosphorus that can be turned into agricultural fertilizer. Over time, many plants have evolved from simple sanitation systems into resource-recovery facilities that generate power, reclaim materials and reduce environmental pollution.

These existing systems already process organic matter and could handle food waste, too.

What Happens When Food Waste Goes to a Treatment Plant

Our research examined what would happen if food waste were sent to wastewater treatment plants rather than landfills. We used real data from a full-scale plant that handles food waste along with sewage.

When we compared greenhouse gas emissions for the same food waste composition, we found that sending food to a landfill would emit 58.2 kilograms (129 pounds) of carbon dioxide equivalent per ton of food waste.

In comparison, we looked at a conventional wastewater treatment plant, the type of plant most common in the U.S. It achieved net-negative emissions of –0.03 kilograms (about 1 ounce) of carbon dioxide equivalent per ton of food waste treated. The plant captures over 95% of methane, compared to roughly 50% at landfills, saving the atmosphere from additional greenhouse gases.

But we found that the advanced treatment plant we studied reduced emissions further. In our analysis, the advanced facility achieved net-negative emissions of –0.19 kilograms (about 7 ounces) of carbon dioxide equivalent per ton of food waste treated.

Both conventional and advanced plants achieve these benefits in similar ways. Treating food waste at either type of plant prevents the 58.2 kilograms of carbon dioxide equivalent per ton that would otherwise escape from landfills. The plants capture biogas to generate renewable electricity, reducing the need to purchase power from the grid. They also recover enough nutrients to fertilize about 23 acres of farmland annually, reducing the need for synthetic fertilizers, which require energy-intensive mining and processing.

How the Logistics Work

Getting the food waste to a wastewater plant doesn’t mean people put their food scraps in the drain or grind them up with an in-sink disposal. At the plant we studied, food waste was collected separately, much like recycling or yard waste, and transported by truck to treatment plants. Our emissions calculations don’t include truck emissions, because trucks are used in the other methods of food waste disposal as well.

Some cities already collect food waste by truck to go to composting facilities. San Francisco has done so since 1996. And New York City has the nation’s largest curbside organics collection, which composts food waste from 3.4 million households.

At the southeastern U.S. treatment plant we studied, trucks deliver food waste to a receiving station, where it’s processed to remove plastics, metals and other nonorganic materials before being blended into a slurry with the sewage solids. This mixture is then added to anaerobic digesters – sealed tanks where microorganisms break down organic material.

The methane that is produced is captured to generate electricity and heat. The remaining solid material is rich in nutrients and can be used to produce useful material, such as fertilizer.

We also found that adding food waste did not overload the plant or cause problems in its operation. The facility processed all of the county’s landfilled food waste – 107,320 tons annually, representing 38% of the county’s total food waste generation. Because of food waste’s lower density compared to wastewater, this added only 0.43% to the plant’s daily capacity. The plant consistently met effluent water regulatory standards. And at certain points, treatment efficiency improved as a result of the additional organic material, which supported the system’s biological processes.

The Economics May Surprise Cities

Local officials, as well as taxpayers, are often worried about the potential costs of a project like this. Wastewater treatment is already expensive, and communities’ existing plants may be nearing capacity.

But the economic results from our analysis suggest that handling food waste in wastewater treatment plants can be financially viable. Towns already pay landfills and incinerators what are called “tipping fees,” based on the weight of the waste delivered. Wastewater treatment plants can also charge these fees.

They can also sell, or use themselves, the methane produced and sell the fertilizer. That additional income means plants can make money even if they charge lower tipping fees than landfills.

Not every wastewater plant is ready to accept food waste immediately. The facility we analyzed is large and well equipped. Smaller operations would likely require new or upgraded equipment, which would involve planning and local investment.

The overall finding of our research is that the limitation isn’t technological or financial. The core systems already exist to transform food waste into a recoverable resource: Cities already handle organic material every day. And they operate complex biological treatment systems. Our evidence suggests these facilities could, in fact, handle food waste in ways that are environmentally beneficial and economically realistic.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

The high cost of renting and buying homes in U.S. cities is no secret. But this affordability problem isn’t limited to urban regions – it affects rural areas as well.

Rural areas, home to about 25% of Americans, benefit from federally supported rental housing programs – particularly a U.S. Department of Agriculture program to provide affordable homes for low-income residents.

The USDA’s Section 515 program is the primary way that the U.S. government finances affordable rental homes in rural communities. Since its inception in 1963, the program has supported the construction of over 533,000 apartments, townhouses and other small, multifamily rental homes.

The program offers below-market-rate loans to private and nonprofit developers who build and manage residential housing for low-income residents in small towns and rural counties. The terms of the deal between property owners and the government obliges these landlords to keep rents affordable for their occupants for decades, generally restricting rent to about 30% of tenants’ income.

Last New Loans Were in 2011

People who live in Section 515 housing typically pay around US$325 per month. That’s much less than rural market-rate rents, which typically run $800-$1,100 per month for modest homes.

Because the USDA stopped issuing new Section 515 loans in 2011, this arrangement is phasing out now as existing loans mature.

Loans for about 90% of all remaining Section 515 homes will mature by 2045, according to the Housing Assistance Council, a national nonprofit that supports affordable housing efforts throughout rural America. By 2050, the owners of nearly all properties currently in the program’s portfolio are projected to have paid off their mortgages.

And once most of the owners of these homes exit the Section 515 program, it will have been fully phased out.

An Often-Overlooked Housing Program

As a public policy professor who studies housing, I wanted to understand what happens when Section 515 loans mature. I also was interested in what determines whether properties remain affordable or leave the program after the loans are paid off.

To find out, I worked with three other housing policy researchers on a national study that was peer-reviewed and published in Housing Policy Debate in September 2025.

As of 2024, these loans were still supporting some 400,000 homes on almost 13,000 properties across 87% of all U.S. counties.

The roughly 750,000 Americans in those homes are among the nation’s poorest. The average household income of someone living in Section 515 housing in 2023 was just about $16,000 per year, which was only about one-fifth of the national median household income, which hovered around $76,600 during the same period in inflation-adjusted 2023 dollars.

In addition to having a very low income, more than 60% of the people enrolled in the program are over 62, have disabilities, or fall into both of those categories.

Market-Rate Options After Maturity

The vast majority of these affordable rental homes were built in the 1970s through the 1990s and financed with USDA loans that last between 30 and 50 years.

By 2050, there will be no Section 515 housing left.

The owners of these rental properties no longer have to keep rents affordable once they have paid off their loans. And their owners and tenants may also lose access to a USDA rental assistance program, which helps keep tenants’ housing costs low.

They can refinance the homes or sell the properties. They also can continue to charge affordable rents to occupants or convert those units to market rate. Because of this flexibility, a large share of rural affordable housing units could soon be converted to properties rented at market rates.

What the Data Shows So Far

For this study, our research team analyzed data from nearly 15,000 of the Section 515 properties throughout the country, which have been placed in service since 1963 – including many that are no longer providing rural affordable housing.

We found that the largest factors determining whether a building remains affordable after a Section 515 loan matures are who owns and manages that property. Buildings owned by for-profit companies are far more likely to leave the program than those that belong to nonprofit housing organizations.

Nonprofit-owned buildings, after accounting for building age and local market conditions, are 30% to 40% less likely to convert formerly Section 515 affordable housing into market-rate properties after the owners pay off their loans.

After analyzing this data, we also concluded that buildings run by small property management companies are more likely to leave the program than those managed by larger ones. Properties where the owner manages the homes are also more likely to exit.

Landlords owning more residential properties were also more likely to exit the program. This indicates that larger landlords may be able to afford the renovations and upgrades required to turn their buildings into market-rate housing once restrictions end.

Why Subsidies and Local Markets Matter

Having subsidies through other government programs can help keep affordable housing units from being converted to market-rate housing.

One-third of Section 515 properties also get support from other programs, including Section 8 vouchers and low-income housing tax credits. Those tax credits are another federal incentive that’s provided to developers who build and rehabilitate affordable rental housing while allowing lower rents for low-income tenants.

Those properties are more likely to remain affordable, even years after some of these tax incentives expire.

Local economic conditions can play a role too. In areas with high unemployment rates, large military populations and low housing inventory, properties are also more likely to exit the program.

That means the same rural counties experiencing economic or demographic pressures are often the most likely to have a decline in affordable housing units when owners pay off their Section 515 loans.

Steps That Can Be Taken

Congress and the USDA have taken some steps to slow the loss of affordable housing in rural areas.

For example, the USDA has funded preservation efforts such as the Multifamily Housing Preservation and Revitalization pilot program, which provides grants, loan restructuring and other financing tools to help repair aging Section 515 properties and extend their affordability.

These efforts have helped preserve some buildings and support ownership transfers from private sector landlords to nonprofit housing groups. But they spend only tens of millions of dollars per year and focus mainly on maintaining existing properties rather than building new housing.

Researchers estimate that about $5.6 billion in repairs would be needed to preserve the affordable housing currently tied to the Section 515 program.

Some lawmakers have proposed reforms aimed at doing more than chipping away at the loss of this kind of affordable housing. The bipartisan Rural Housing Service Reform Act, first introduced in 2023 and reintroduced in 2025, would modernize USDA rural housing programs and allow certain rental assistance contracts to continue after mortgages mature. As of early 2026, the bill remains under consideration.

Over the next two decades, most of these landlords will pay off their Section 515 loans. Unless the government reinvigorates the program or replaces it with something else, much of rural America’s affordable rental housing could gradually disappear as owners convert all Section 515 properties to market-rate housing.

Whether rural communities retain affordable housing will depend not only on what the federal government does, but also on the properties’ owners.

This article is republished from The Conversation under a Creative Commons license. Read the original article.