Thanksgiving Leftovers? One Student’s Solution to Food Waste

As many people wrap up a Thanksgiving week of hearty eating, those leftovers are stacking up in the fridge. What happens to all the excess food? Often, it ends up in a landfill, producing methane and contributing to the greenhouse gases that are warming our planet.

Kelly Zhang, our latest guest on Future of the Business World, is addressing the problem of food waste through science-driven innovation and entrepreneurship. Be sure to click on the arrow above to learn about her enterprise, Cycle Sustain.  

An edited transcript appears below.

Wharton Global Youth Program: Hello and welcome to Future of the Business World. I’m Diana Drake with the Wharton Global Youth Program at the Wharton School, University of Pennsylvania. Thank you for joining us as we explore and celebrate youth innovation across borders and business sectors. High School innovators often discover purpose at the intersection of their passions and the world’s problems. Today’s guest, our 50th on Future of the Business World, fits that very profile as she tackles the issue of food waste.

Kelly Zhang, welcome to Future of the Business World.

Kelly Zhang: Thank you for having me. Very excited to talk about Cycle Sustain today.

Wharton Global Youth: I am excited to get started too. First, tell us about yourself.

Kelly: I’m a high school student in Pasadena, California. I’m a current junior. And as for my interests, I love animals. Outside of school, I’ve been doing horseback riding for 10 years, and I would say that’s how I started loving the outdoors. During my free time, I would spend it at the barn, grass-grazing my horses. And other than that, I have a dog and two guinea pigs.

Wharton Global Youth: I love it, sounds very peaceful. I’m going to start with a direct quote from you left on a Wharton Global Youth article this past summer during our Comment and Win competition. Your comment began: “Climate change. It’s a phrase that dominates our classrooms and our news broadcasts. We’re always hearing our earth is dying, but what is the majority of the population really doing about it? In reality, nothing.”

You got my attention with this sentiment, and I’m sure that of many of our readers. Let’s unpack parts of your statement. How often do you discuss climate change in school? I’m curious how often this real-world problem makes it into the classroom?

Kelly: I would say that the climate issue has become more prominent in our school, in the sense that we do have new climate clubs coming up, even in our middle school. In our middle school, I would like to highlight that we have our plastic block, which is also led by our sustainability director, Miss Fleming. She has taken really good action for that. [We traditionally had] single-use plastic plates for lunch and single-use utensils. Now that’s all been replaced, and we can reuse it year after year. Another project has been in our gym. We’ve established solar panels. The biggest [project] that I’ve been involved in is our composting project. The composting project is what students have gotten involved with. We do have a lot of announcements at the beginning of every year to make sure that we source-separate. We have different green bins for where to put our organic waste, and then we also have a separate bin just for our other waste. That’s been helpful for the bigger population to participate in.

But I would still say that as an entire group of students, we don’t have enough discussion about climate action and climate change in our classroom. We do have a good climate class, but that’s only available to seniors. And for students who already aren’t as interested in climate change, I feel like they’re not going to be taking this class, and it might take away from what they have in their personal experience [when they are] learning about this in a classroom setting. I do hope in the future that even within our core classes, we can have this more integrated within the classroom setting. So, even people who don’t think they’re interested in sustainability can get introduced to it.

Wharton Global Youth: You have, as you mentioned, this climate club. And I want to go back to composting, because that’s at the heart of what we’ll be talking about today. Tell us about the composting project and how it relates to the problem of food waste, which is something that you are addressing. Tell us about the club activities that you’ve done and how it has deepened your interest in this broader problem?

Kelly: Yes, so we do have a source-separation system. We have our green bin and our other waste bin, if you will. Our school also established a community compost hub. So, for a lot of people, this term is new. I’ll describe briefly what it is. It’s a really big box, if you will, made out of plywood or Cedarwood. So, it’s not going to be degradable. And it has different areas for ventilation.

Inside, there are three sections. In composting, we usually like to say there are three different sections of it. First, it’s going to be growing the bacteria. This bacteria will cause all of the mulch and all the things that we put inside [to break down]. We have our nitrogen from our organic sources, and our carbon from, let’s say, cardboard, or dry leaves, or different sawdust that all gets mixed in, and then the bacteria can feed on this, and they grow and grow, and it causes a temperature rise. This temperature rise is really important, because this shows the increasing metabolic activity of the bacteria.

After that, it gets transferred to the middle bin. In the middle bin, we reach temperatures of 110 degrees Fahrenheit. It gets really hot in there. That’s when microbial activity is at its peak. And then that goes on for another week, and then the third week, assuming that it’s hot composting. The process should take around three weeks.

Then it’s put into the third bin, where it’s let to cool down. That’s the entire process. It’s a really big three-bin process that has a lot of ventilation, so a lot of different microorganisms can get in there and get the process [of breaking down the organic waste] kick-started. As for our school, we have that set up as a volunteer system, both in our middle school and our high school. It’s part of our Integrated Science program. A ninth-grade block can go get volunteer experience there, and then middle school can also handle it.

We do settle some of our organic waste on campus. But because we have quite some waste, we distribute it off to a bigger facility that will take care of the organic waste composting, and then the other waste for us as well.

Wharton Global Youth: When students are accessing this technology, if you will, at school, are they taking their plates of leftover food from the cafeteria, and they’re scraping it into a particular bin and then that gets ultimately into the compost pile? Tell us about you and your classmates and where it impacts you in school? Also, can you tell us a little bit about the end result you mentioned? You send it to another facility. What happens to the compost? How does it benefit society?

Kelly: What we do at our school is exactly as you said. We have different stations set up around the campus. Our Climate Coalition is, in charge of making sure that it’s running smoothly. We have different signs up for what people can and can’t put in there. We have  the green bin, another trash bin, and then our plate bin. We scrape away any leftovers. We still highly encourage people to not have any leftovers. Because even though organic waste is amazing to turn into fertilizer, it’s still best if we don’t have that waste there. We encourage people to try not to have as much food waste. But otherwise, we scrape it into the green bin, then we put our plate and utensils aside, and then that all usually gets sent off to a bigger facility — because we only do have one community composting bin set up for both Middle School and Lower School and our high school.

At that facility, it’s like a big mound of organic waste and mud and  other carbon sources. If you search up an organic waste commercial composting site, it looks like big mounds. What happens is it gets churned every two-to-three days. This churning allows air pockets to be filled in, because probably the most important thing is that you let the bacteria undergo aerobic respiration. If the bacteria gets sent off to landfills, that’s why the methane production gets so big, because the bacteria go through anaerobic restoration and produce methane. By introducing these air pockets, it actually goes through aerobic restoration. And the methane rates are, practically non-existent, which is amazing. Then it gets turned into compost, which is a really, really good fertilizer. When I’m planting stuff in my garden and if the soil isn’t as great, then I use half top soil, half compost, and it’s a really nice organic fertilizer that you won’t find in stores. Sometimes there are chemicals in those, but this is a great organic fertilizer.

Sometimes [the compost] is also turned into a biofuel. I was working with the school, and they had a system where the organic waste would break down, and then it would turn into oil and gasoline, so that it would literally be able to power their kitchen. They had this entire system going on where their food waste could be used to make more food. It was a really, really great system. These are two ways that organic waste gets turned into something that can be used.

“As one person, what I can do is reach people who can reach more people. I like to think of it as a butterfly effect.” –Kelly Zhang, Cycle Sustain

Wharton Global Youth: I would love to know more about the food waste problem. Have you talked a lot about that in your climate club and in other places about why this is even a problem facing our planet?

Kelly: As for the issue of food crisis, I would say that’s because of the difference in food equity between people who have a lot of food — almost have excess food, and then people who barely have any food at all. This is reflected in a book that I read over my outdoor education trip called The Story of More. This story talks about how we do have enough food to feed everyone. We have a sufficient amount of food, and we’re probably never going to run out in the distant future. But it’s the distribution and our idea of sharing resources that [creates the] issue. This idea has created so much food waste, [which is] going to landfills. Even the methane and the greenhouse gas emissions, the climate change caused by this [food waste] affects the people, the groups, who do not have food the most. It’s a perpetual cycle, where the people who don’t have food are getting impacted by the food losses of people who do have food.

How I’ve noticed this in my life is that, I was talking with my sustainability director, Miss Fleming, and she brought up [that] California has a mandate called SB-1383. This mandate says we need to have 75% of our organic waste taken away from landfills by 2025. That’s in less than a year. I saw that number in 2023, but I [still didn’t] think we were that close to that goal. I would look around my neighborhood and there would be dumpsters that were sitting out every Wednesday. I thought, there is no way that this is the system, and we still don’t have source separation for everyone.

I got really curious about that. I went to my local park called Lacey Park. I went there for a month to get some interviews going on, and I did a little survey. I had them fill out some Google Forms, and I took some notes on my pad board. I realized that 61% of people did not even participate in organic recycling and did not follow the mandates that have been set in place. This made me think that we need to take more action, not just for accessibility, but also for awareness. So that’s how I started Cycle Sustain.

Wharton Global Youth: That’s what I want to get into next. You had your work at school, and you had your independent research at the park, and it was time for action, right? Tell us about Cycle Sustain Composting. How does your at-home compost bin works? What’s the science behind it?

In Cycle Sustain, I do both community compost hubs and at-home composting. I’ll start off with the at-home composting. I started designing this last year as well. It started first with the idea that if we can keep everything at home, and we can keep all of our composting local, then we can cut the amount of fuel and gasoline that are used to transport the organic waste to a site that’s far away. And so I was thinking, what if we could just do this at home? Obviously, the main issue is that organic waste, as it decomposes, produces ammonium. There is going to be the risk of smells. I was trying to make sure to cut out that factor. So, through trial and error, I started with resin and began the engineering of this product. It’s a three-box system, stacked. I made sure that all of the gas between [the boxes] was completely sealed. And then I put one-way air valves on each and then I created locks for each bin. That I also had to mold by hand as the shape was not as I wanted to be. I had to make sure that it would fit into every mold, so that the air would not escape and there would not be any odors leaking out. It worked great for preventing smells. I did not smell anything during my trial run, I trialed that two times after, remaking it with different supplies. I was trying resin for its environmental sustainability, and then I found some other products to try it with.

The one-way air valve was great at preventing air from coming out, but I still needed that air flow. There’s the idea that if I make this a bigger size, there will be a pressure buildup inside. Because as the aerobic bacteria break down, they create more air. I was scared it was going to create pressure and pop on someone. So, I went to 3d modeling, which I had explored a little bit, but I hadn’t gone that deep into. This was a great opportunity for me to explore more how 3d designs work and how different materials network. I started off with a material called PLA, which is a corn-based plastic, and this is probably the most sustainable material I have found so far. It’s completely biodegradable. I thought that was amazing.

The bin is a two-bin [design]; it has an outer layer and an inner layer. This is, again, to prevent any smells. Inside the outer layer is a bag held by bamboo fabric that can be completely replaced whenever it needs to be, or you can keep on adding the material inside. Inside, I added sodium bicarbonate or baking soda. This was a really fun experiment for me, because I realized that baking soda changes the pH of the materials inside, so it absorbs all the odors. I tried to make the inner layer more permeable so that if any airflow goes across, it wouldn’t go up. Even though I made the lid sealable, air will still somehow find a way through. And then it’s all wrapped in bamboo fabric, which I’ve discovered is new in the fashion world, which is interesting.

Wharton Global Youth: I love all the detail, and you’re taking me back to putting that box of baking soda in my refrigerator to absorb odors, so I can relate to that. How fascinating that you have created this bin. Tell us what you now do with the product and how it fuels, for lack of a better word, your bigger mission of building awareness around food waste and how to address organic compost?

Kelly: As for the product, because I haven’t completely finished testing yet, right now I distribute it to family, friends and people I know at school. It hasn’t yet been out for sale. But they’ve been using it, and they’ve been saying it’s great. It will probably be out soon. For now, I’ve [found other ways to] get all the funds for establishing the community compost hubs. If you get the idea of my school compost hub, [my plan is to design my compost bin], and contact different product manufacturers and different schools and help establish and set up [composting bins] at those schools. Some schools require extra funding, while some have their own budget. For the schools that require their extra funding, usually these big compost bins take $1,000 to make. So, I do monthly fundraising through bake sales. The hope is to make the at-home compost hub a sellable product on the market, and then once it does, that will be the main source of income to supply the community composting hubs for more schools and the local government at my local park.

Wharton Global Youth: What other countries have you been able to expand into?

Kelly: Rwanda, Uganda, El Salvador, Taiwan, China and Canada.

Wharton Global Youth: Excellent. So, you’ve established relationships with people there, and you’re getting them excited about your idea.

Kelly: Yes. And then, as for Canada, I want to give a shoutout to one of my partners there, Chloe Lee. She runs VitaSciRise. She’s been a great help to more of the educational projects of Cycle Sustain.

Wharton Global Youth: During the Comment and Win — let’s return to that for a minute — you wrote:  “Unfortunately, I can confidently say that for the distant future, the majority of people are still just going to think of climate change as a job for scientists and the government to resolve. In truth, most people will not change their way of life to help others until the repercussions of climate change reach themselves or their loved ones.”

That doesn’t sound very hopeful. Kelly. So tell me, are you more cynical than ever? Or do you feel you can make a difference based on the work you’ve done so far?

Kelly: It does come off as a bit cynical. And I would say that I still do agree that a lot of people won’t take action until it reaches them at a personal level, because it is just so much more convenient for people sometimes to do something that’s not as sustainable. But I would say that as one person, I can’t make the biggest difference. But as one person, what I can do is reach people who can reach more people. I like to think of it as a butterfly effect. If I can reach 10 people through, for example, my ambassadors’ program, then if these 10 students that I’ve trained to become ambassadors can, at their winter event, help to train 100 more students, so they each take on 10 more students, then 100 students have been reached. On a personal level, I think that is what this world is looking for. If everyone can take that action to spread their message to another person, and not just keep it to themselves, but keep on influencing and keep the cycle going, then I would say that’s how we do Cycle Sustain.

Wharton Global Youth: Hopefully the Future of the Business World podcast will also help you get that word out to other high school students around the world. Let’s wrap up with our lightning round. Please answer these questions as quickly as you can.

Something about you that would surprise us?

Kelly: I’m an identical twin, and I do horseback riding.

Wharton Global Youth: What would you be caught binge-watching at midnight?

Kelly: Probably what I’m watching right now. Gossip Girls.

Wharton Global Youth: What  has been your most memorable moment as an entrepreneur

Kelly: Hoping to start a sustainable fashion company.

Wharton Global Youth: Something you would like to learn that you don’t yet know?

Kelly: Probably another language, maybe French. I love learning new languages.

Wharton Global Youth: The last time you felt you truly made a difference, however small?

Kelly: I convinced my dad to get a Walla water bottle, his first reusable water bottle.

Wharton Global Youth: You are starting your own business-themed talk show. Who is your first guest, and why?

Kelly: My first guest would be Rita Doss. She’s an amazing mentor through AWIS, for the sustainable fashion company that I’ve been working on. She’s developed her own sustainability and helping women with their companies. I love her for that, and I would definitely love to have her on the show.

Wharton Global Youth: Kelly, thank you for joining us on Future of the Business World.

Kelly: Thank you so much for having me.

Conversation Starters

Kelly Zhang feels that schools could be doing more to integrate lessons and conversations about sustainability. Do you agree? How is your school addressing climate change? Share your story in the comment section of this article.

How does composting work?

Do you agree that the “butterfly effect” Kelly alludes to will make a difference in this world?