IRA FLATOW: This is Science Friday. I’m Ira Flatow. Today is Earth Day, where many people around the world are taking time to think about their relationship with the environment and focus on activities aimed at solving the existential problems our planet faces. And we will be doing the same. Devoting our program to Earth Day stories, ideas, and issues.

First up this hour, our news roundup. Joining me is Sara Kiley Watson, assistant editor at Popular Science, where she’s in charge of their sustainability coverage. And she’s collected an assortment of Earth-focused stories and some do-it-yourself solutions. Welcome to Science Friday.

SARA KILEY WATSON: Thank you so much. I’m so happy to be here.

IRA FLATOW: Nice to have you. I want to start off with an issue that, I recall, we were talking about on the first Earth Day five decades ago, and still talking about it today. And I’m talking about the problems with big cities of the future. Many visions of the future involve big megacities in places like India and China, where the density of the population can lead to air quality problems in these mega metropolises. Right?

SARA KILEY WATSON: Right. So I think when you have the combination of industrialization and more people coming into the same square footage, you can have more factories and things producing carbon emissions. You can have more people with their cars and with their houses and using energy. And basically, that all kind of piles up on top of each other. And if there aren’t regulations in place to keep pollution under control, it can kind of get a little bit out of control.

IRA FLATOW: Let’s talk about the study you looked at. In that study, they worked through what pollution might be like in these megacities down the road. What did they find?

SARA KILEY WATSON: So right now, a megacity is defined as a city with a population of more than 10 million people. And currently, according to the UN, there’s about 30. And from this study and science advances, a group of international researchers examined satellite air pollution data across 13 years,– between 2005 and 2018– across 46 projected future megacity locations throughout the tropical regions of Asia, Africa, and the Middle East. Basically, over these 13 years, where these cities aren’t even really megacities yet, we’re seeing a lot more pollution just as they’re starting to grow.

IRA FLATOW: Well, have we formulated what the ideal city of the future should look like?

SARA KILEY WATSON: I think we’re definitely working on it. We’ve got to figure out a way to make industries that are polluting less polluting instead of just copy and pasting them into other parts of the world, I think is the gist here. I think some of the easy things that we can learn from are lowering the dependence on cars in these major cities. Lowering the sprawl that we’ve had experiences with in places in the United States where there are a lot of pollution problems. Making sure that pollution is strictly regulated so that we aren’t just taking one problem with industrialization and moving it elsewhere, because these are cities where millions of people will be living.

IRA FLATOW: Yeah. Yeah, these are all issues we talked about five decades ago. It’s amazing how these have just continued to be main issues. And one of the issues we talked about years ago, and one that we’re talking about again, is stretching out the gasoline supply by adding ethanol to the gasoline blend. We’re seeing that being replayed now with a call to increase ethanol from 10% from the early 1970s to 15% now of the blend. But you say that adding this extra ethanol has a downside.

SARA KILEY WATSON: Yes. There’s this really interesting story in Canary Media from Michael Grunwald basically about how biofuels are both making the food crisis a bigger problem and also the climate crisis. So, there’s a lot going on in the world right now. Of course, we all know there’s a war going on, and there’s basically what Grunwald called a– we’re on the brink of unprecedented, catastrophic levels of food insecurity. So he says, it’s a weird time to divert more grain from the food supply to fuel tanks. The amount of corn that it takes to fill an SUV with ethanol could feed a person for an entire year. Basically, when you’re growing food to be put in a fuel tank, it’s not as efficient of fuel as it is efficient for feeding people.

IRA FLATOW: Could we not try to make biofuels from things that are not corn? Other wastes?

SARA KILEY WATSON: Yeah. I think when you’re thinking about the options of getting into a more environmentally-friendly energy world, you have to think about all of the things that we have to offer. And you can make biofuel from seaweed and certain agricultural wastes and things. So I think there’s definitely a space for figuring out a way to make biofuel actually friendlier than just replacing it with corn, which is this intensive crop that we rely on to feed people.

IRA FLATOW: Let’s turn to some more positive food news, something each of us can do. A change we can make. So let’s say, our food takeout orders are more sustainable. I know you have some suggestions for that.

SARA KILEY WATSON: Yeah so at Pop Sci we’ve been doing a couple of pieces, basically looking at little things that we can all do to make all of the things that we do in our day to day life a little bit greener. And so, I live in New York, I love takeout, I love eating. So this one was a big one for me. There’s only, like, one thing really not to love about takeout, and it’s the waste. Packaging products like plastic containers, cutlery, drinking cups, and straws make up about 269,000 tons of plastic found in the oceans right now.

On top of that, food waste is also a huge problem. When we put food into landfills, it leaches methane, which is an even ickier greenhouse gas in the short term run than carbon dioxide. And there’s been a couple of studies over COVID, looking at how people tend to panic order or over order when they get food delivery, which can lead to this food waste.

But luckily, there’s a lot we can do. The first step is super easy, and there’s a lot of options. I feel like you can just see it on Uber Eats or whatever. But to turn down extra napkins, sauce packets, plastic knives, all of that. If there’s not an option to leave it, like, literally in the app, then you can call the restaurant or leave a note. And that will automatically just slim down what ends up in the garbage can.

IRA FLATOW: Yeah. Yeah, you could also order less energy-intensive food, like less red meat.

SARA KILEY WATSON: Oh, yeah. I mean, I think if we’re going to eat meat, it needs to be a little bit of it, not the whole shebang. So switching to more whole grains and things like vegetables, fruits, all of that is going to help a lot when it comes to the carbon intensity of our diets.

IRA FLATOW: I’m going for my tofu curry on this one.

SARA KILEY WATSON: That sounds really good.

IRA FLATOW: I’m getting hungry. A few weeks ago, we talked about steps you could take to make your home more energy efficient, but a lot of solutions and incentives worked best for people who own their homes. But you have some suggestions for renters as well. Tell us about those, please.

SARA KILEY WATSON: Yeah, sure. So I’m a renter, so these are things that come to mind. The first one is weatherize and energy efficient proof your apartment or house as much as you can. Get those LED light bulbs. Get little pieces of weatherization strips, so if there’s a draft, where you’re like, OK, my air conditioning is running away through there. So find ways to fix that where you can even take it out and take it to your next place. Even things like blackout curtains can sometimes be helpful in lowering your energy bill.

And another thing that you can do– so certain utilities across the US have these programs where they can let you know when there’s about to be a peak energy hike. So do a little research, and just figure out what time of the day are people using a lot of energy in my community. And when you know that’s happening, then you know it’s not time to run your dishwasher or it’s not time to run your dryer, it’s not time to plug all of your laptops into the charger.

So just being a little bit aware of, OK, we’re on the border of needing a lot of energy at this time. So if it’s a really hot day, it’s when everybody’s in front of their air conditioning, all of that. So just being aware of what everybody else is doing, and some utilities will set up a way for you to know that. There’s also a couple of programs where you can pay a little bit extra and have your utility bill come from renewable energy. So checking it out, seeing what your options are, like, that’s something that you can do without getting your landlord involved.

IRA FLATOW: Going back to the bigger scale for homeowners, like myself. I installed solar panels and battery storage. And I became part of a small electric grid in the Northeast, where we actually share electricity when we need it. When there’s a storm out or power is down in one part of the region, and that was set up by my electric utility. You suggest going one step further. Starting or joining your own microgrid. Talk about that, if you will.

SARA KILEY WATSON: Yeah. So this is something that you can do in correlation with the utility. You can do it, you can reach out to a couple of companies. I think Tesla and Sunrun are two that I looked at. So you can put solar panels on your roof and store it yourself and kind of have your own thing going. But you can also expand that to multiple houses. Or even some towns kind of have this thing set up where they’re all sharing this. So not only does this allow you to say, OK, my energy is coming from the solar panels on my roof. Or my energy is coming from, like, the wind turbines that I’m aware of. You’re also able to kind of keep your grid small, so if there’s ever a situation where there’s a wildfire or a snowstorm or anything like that, where you can’t get to those big utilities or the big power plants, you will have some basics to rely on in your own community.

We’ve had these kinds of systems set up forever, in terms of hospitals and some, like, university campuses. But I think there’s now a shift to if you wanted to do this, if you want to say, I know where my energy comes from and I want to be more resilient in that way, homes and communities are able to do that too. Which I think is very, very cool.

IRA FLATOW: Yeah, that is cool. Finally, I love a good construction material story. My staff will tell you that. That’s another topic, because you have one about how someday cement– one of my favorite topics. Cement might be part of a climate solution. Because right now it’s a big source of emissions, is it not?

SARA KILEY WATSON: Oh, yeah. So this one is from The Economist, but I love talking about this. One of the sneakiest ways right now that carbon is emitted is through cement. And according to this story, the five billion metric tons of cement made every year ends up creating a whopping 8% of global emissions annually. So cement, if it was a country, would be just outside of America and China in terms of emissions. But it doesn’t have to be that way.

So basically, when cement is made, it’s dug up in limestone, and then it’s quarried and mixed with clay in a process called calcination, which then emits carbon dioxide. The leftover lumps that are there are cooled and then milled into cement. But The Economist goes through a couple of neat options on how we can kind of combat this. But the one I’m most excited about is capturing the carbon from this process, from this calcinization, and then using it to actually go in and cure the cement. So you can use water to cure cement, but when you use CO2, it actually makes the cement even stronger.

And what excites me about this is that not only is it a way to utilize the CO2 that’s being emitted, but once you have CO2 back in cement, it’s going to stay there. It’s not like putting it back into fuel or putting it under the Earth.

IRA FLATOW: It’s locked in. Wow.

SARA KILEY WATSON: Yeah, it’s locked in there. So that’s very cool.

IRA FLATOW: That’s a great idea. Thank you for telling us about that. Sara Kiley Watson. Thank you very much for taking the time to be with us today.

SARA KILEY WATSON: Thank you so much for having me. This is so great.

IRA FLATOW: Nice to have you. Sarah Kylie Watson is an assistant editor at Popular Science based in New York. And now here’s SciFri’s trivia host, Diana Montano, with some Earth Day meditations.

DIANA MONTANO: Thanks, Ira. Did you know some desert mosses can capture water straight out of the air using specialized semi-transparent hair-like structures at the end of their leaves, called awns. That’s spelled A-W-N-S.

You may picture the Earth’s mantle as brown or orange, but the igneous rock peridotite and mineral olivine, which make up much of the mantle, means it’s really more greenish than brown.

Maleo birds lay their eggs in deep, sandy pits. The eggs are then incubated by the heat of the sun or from geothermal energy from volcanoes.

The Earth is about 5.54 billion years old, give or take a few million years.

IRA FLATOW: Thank you, Diana. That was quite enlightening. Diana will be back with more meditations later in the show.

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