From Cradle to Grave: Life Cycle Insights from California’s Strawberry Fields

Podcast Transcript

[00:00:00] Nataliya Shcherbatyuk: Hello and welcome to the Mulch Matters podcast where we will explore the intriguing world of mulch and its impact on agriculture and the environment, as well as update you on the latest research about soil-biodegradable mulch and recycling options for plastic mulch. I am your host, Dr. Nataliya Shcherbatyuk, and I am a communications specialist for the project, “Improving end-of-life management of plastic mulch in strawberry system”. In each episode, we’ll dive into the latest research, trends, news, and insights on why mulch matters and how we can improve plastic mulch end-of-life options. We’ll also branch out and discuss other plastics as well as talk to researchers, experts, and practitioners in the field who will share their insights and experiences on how to use mulch effectively in different settings.

[00:01:05] Nataliya Shcherbatyuk: Welcome back to another episode of Mulch Matters Podcast, and let’s welcome our guest today, PhD candidate Oluwatunmise Dada. Hi, Dada. How are you?

[00:01:14] Oluwatunmise Dada: I’m very well. Thanks, Nataliya. Thanks for having me.

[00:01:18] Nataliya Shcherbatyuk: Thank you so much for making time to join us here. So, to start, would you mind telling us a little bit about yourself, about your background? What led you to work in the area of your research, like BDMs and California strawberries?

[00:01:35] Oluwatunmise Dada: Actually, currently I’m a PhD candidate here at Washington State University, so I study biological and agricultural engineering. And from that name you know that, yes, I’m particularly interested in agriculture and biosystems. I have a background in environmental and biological engineering.

[00:01:55] Nataliya Shcherbatyuk: So, environment.

[00:01:56] Oluwatunmise Dada: Yeah.

[00:01:56] Nataliya Shcherbatyuk: And where did you get your environmental biological engineering degree?

[00:02:00] Oluwatunmise Dada: I got the degree from University of Ibadan, and the degree is actually Agricultural and Environmental Engineering. Aside from that, I have special interest in sustainable production systems and how we can turn waste to value. In the production system, I look for ways to reduce pollution and waste, and that is the reason why biodegradable mulch film is a special example for this challenge because we promote it as an alternative to conventional plastic. Its sustainability depends on the production, the use, and what happens to it after you use it. So this systems perspective drew me to this work, and that is why I’m here working on biodegradable mulches.

[00:02:47] Nataliya Shcherbatyuk: And why have the strawberries of California been chosen for this?

[00:02:51] Oluwatunmise Dada: California happens to be one of the states in which you have a lot of strawberry production. The capacity also is high, and we have enough data to model the system in California. Life cycle assessment itself requires data to model. If you don’t have data, you won’t be able to get good results. We have the data, and we have our people working in SCR projects in California, so they were able to provide us the data we need to model the system. That is why California strawberries were chosen in particular.

[00:03:30] Nataliya Shcherbatyuk: And you know what? I want to just dive straight into your project, if you don’t mind.

[00:03:43] Oluwatunmise Dada: Yeah.

[00:03:44] Nataliya Shcherbatyuk: And your study uses, and correct me if I’m saying it wrong, cradle-to-grave life cycle assessment.

[00:03:53] Oluwatunmise Dada: Yeah. Grave, yeah.

[00:03:55] Nataliya Shcherbatyuk: Good. And can you tell a little bit more about it? What does it mean in these particular terms?

[00:04:04] Oluwatunmise Dada: When we say “grave,” that means the end. So when you combine those two terms together—cradle-to-grave—that means we are modeling the life cycle of the mulch film from how it was produced, then after you produce it, you transport it to the field to be used by growers. After you use it, what happens to it? Cradle-to-grave life cycle assessment means the assessment of the life cycle from the production to the use and to the end of life. That is what it means. So, we are covering the whole production system to the application, then to what happens to it after.

[00:04:44] Nataliya Shcherbatyuk: That’s interesting. And from what I remember from your studies, you were using two biodegradable mulch formulations, correct? Could you explain those two BDM formulations that you evaluated and why you chose them?

[00:05:06] Oluwatunmise Dada: We have different formulations of biodegradable mulch films, a variety of them, but we chose two formulations: the PBAT and PLA formulation, and the PBAT and TPS formulation. I’m going to explain the terms. In this formulation, we have 70% PBAT and 30% TPS or PLA. ‘PBAT’ stands for polybutylene adipate-co-terephthalate. It’s a biodegradable polyester but it’s produced from fossil resources, so it’s derived from petroleum. ‘PLA’ stands for polylactic acid. It’s a biodegradable polyester also, but this one is produced from fermentation of sugars. When you grow your corn, you ferment it to get sugar, then lactic acid, then polylactic acid. ‘TPS’ stands for thermoplastic starch. It’s a biodegradable polysaccharide produced from starch. These two formulations were chosen because they are the two market-representative biodegradable mulch films available today. It’s very common in the market. Most growers—let me say 6 out of 10—use this formulation of 70% PBAT and 30% TPS or PLA. PLA is strong but brittle. TPS is readily biodegradable because it’s starch, but it’s water-sensitive and lacks strength. PBAT is flexible and strong, with mechanical properties close to conventional polyethylene. When you blend these together, PBAT provides flexibility and toughness, while PLA and TPS provide biodegradability. That is why it’s close to conventional low-density polyethylene but also biodegradable.

[00:07:37] Nataliya Shcherbatyuk: And I found it interesting that you’ve used, as a baseline comparison, PE—polyethylene mulch.

[00:07:49] Oluwatunmise Dada: The reason why we chose PE landfilling—polyethylene landfilling—is because it’s common practice today. Normally, when growers do not have the facility to recycle it, or when the recycling cost is higher than the tipping fee to take it to the landfill, polyethylene mulch ends up in landfills. We chose that comparison because it’s common practice today in the industry. That is why we chose landfilling as the baseline for polyethylene.

[00:08:26] Nataliya Shcherbatyuk: I see. So, could you tell us a little bit more about the end-of-life pathways that you looked at?

[00:08:35] Oluwatunmise Dada: For the end-of-life, we focused more on biodegradable mulch films. We used polyethylene landfilling only as a comparison. For biodegradable mulch films, we chose soil biodegradation, composting, and anaerobic digestion. These are systems that can actually degrade biodegradable plastics. Soil microorganisms degrade biodegradable mulch film and produce water, carbon dioxide, and biomass, which can be used as peat. We chose these three pathways because they are promising for degrading biodegradable mulch film. But in our system, we found the best and the worst pathways. That is the essence of our study—to inform people on the best pathway for biodegradable mulch film waste.

[00:09:54] Nataliya Shcherbatyuk: And which end-of-life pathway performed best overall, and why?

[00:10:03] Oluwatunmise Dada: Overall, soil biodegradation performed best. It avoids waste collection and transport. It reduces fossil fuel use. The carbon component of the biodegradable mulch film is converted by soil microorganisms into biomass, carbon dioxide, and water. The biomass can substitute for soil amendments, like compost or humus. It avoids emissions from transportation because you don’t have to collect it or use heavy equipment. You just till it into the soil. It avoids fossil fuel use because you don’t transport it. The carbon converted into biomass benefits the soil. Following soil biodegradation is anaerobic digestion, then composting. Landfill is the worst. Anaerobic digestion performs well because it produces energy, but not all biodegradable mulch film degrades in anaerobic digestion. So, soil biodegradation remains the most sustainable pathway.

[00:11:57] Nataliya Shcherbatyuk: And can we go back to talk a little bit about TPS and PLA?

[00:12:04] Oluwatunmise Dada: Yeah.

[00:12:05] Nataliya Shcherbatyuk: How are TPS and PLA different in terms of ecosystem and human health impacts? I know human health is not part of the study, but you’ve done a lot of reading.

[00:12:24] Oluwatunmise Dada: TPS and PLA are both produced from starch, but their production processes differ. TPS is produced from pure starch. After you grow the grain—let’s say corn—you harvest it, then process it to extract the starch. That extraction process generates wastewater and potential pollution. PLA uses the grain directly through fermentation, so it avoids the starch extraction step. Fertilizer use during cultivation contributes to eutrophication potential. Wastewater from starch extraction also contributes to eutrophication. For human health, we found that the TPS pathway causes non-carcinogenic human health impacts. These can result from chemical plasticizers required in starch conversion and heavy metals in fertilizers. This is why TPS performed slightly lower than PLA in our study.

[00:14:53] Nataliya Shcherbatyuk: That’s interesting. It’s outside our project scope, but it’s good to know.

[00:15:02] Nataliya Shcherbatyuk: You’ve been using sensitivity analysis. Could you explain what exactly you did?

[00:15:20] Oluwatunmise Dada: Sensitivity analysis helps us understand “what if” scenarios. We focused on degradation rate and transportation distances. When biodegradable mulch degrades faster, it helps convert the carbon component into soil amendment peat. Faster degradation improves environmental performance. Shorter transportation distances improve the performance of anaerobic digestion and composting because they reduce emissions and fossil fuel use. Diesel engines emit particulate matter and nitrogen oxides, so shorter distances reduce pollution.

[00:17:11] Nataliya Shcherbatyuk: I wanted to ask how important local waste management is, but you already answered that.

[00:17:20] Oluwatunmise Dada: It’s very important. We did not assess the waste management facilities themselves, only their distance from the farm. If facilities are far away, transportation burdens increase and environmental benefits are lost. Diesel and gasoline use increases fossil fuel consumption, global warming potential, and ecotoxicity. Waste collected from farms often contains soil impurities. When washed, it releases agrochemicals into the environment, causing ecotoxicity. This is why having waste management infrastructure close to farms is important.

[00:19:17] Nataliya Shcherbatyuk: What do you think are the key limitations of current life cycle assessment methods when it comes to soil-biodegradable materials?

[00:19:38] Oluwatunmise Dada: One major limitation is that current LCA methods do not explicitly capture soil health effects. Biodegradable mulch films do not fully degrade within one growing season. It takes longer for most formulations to reach 90% degradation. This leads to a steady-state condition where the amount applied equals the amount degraded. The question becomes: What happens to the unmineralized biodegradable plastic in the soil before the next growing season? Current LCA methods do not capture this, leaving a gap.

[00:20:55] Nataliya Shcherbatyuk: Based on your work, what would you say to growers deciding whether to use BDMs?

[00:21:00] Oluwatunmise Dada: Biodegradable mulches can provide environmental benefits. But those benefits are not automatic; they are strongest when paired with suitable end-of-life management, especially soil biodegradation. Growers should consider not only field performance but also environmental benefits, cost savings from not removing or transporting mulch, and reduced emissions. Landfilling polyethylene is not sustainable. It adds cost and causes ecotoxicity. Biodegradable mulch is more sustainable from an environmental perspective.

[00:22:53] Nataliya Shcherbatyuk: Landfilling is definitely a challenge. It’s not about PE being bad, but about what we do with it at the end of its life.

[00:23:29] Oluwatunmise Dada: Exactly.

[00:23:30] Nataliya Shcherbatyuk: One more question: What excites you most about the future of sustainable materials in agriculture, and what’s next for you?

[00:23:49] Oluwatunmise Dada: It’s encouraging to see that we are moving closer to solving the problem of plastic pollution on farms. With research and extension outreach, we provide more solutions. Our study helps move the discussion beyond simply asking whether a material is biodegradable. It shifts toward asking whether the whole system—from production to degradation—supports sustainability. This opens the door to better materials and better waste management systems. As for me, I plan to continue working in this area, especially anaerobic digestion and soil biodegradation. This issue is global. With each research effort and outreach program, we get closer to solutions.

[00:25:42] Nataliya Shcherbatyuk: How much longer until your graduation?

[00:25:48] Oluwatunmise Dada: The goal is to graduate this fall, hopefully. I’ve been here since 2022, so this is my fourth year.

[00:26:04] Nataliya Shcherbatyuk: Well, good luck to you with that. Thank you so much for your time and for joining us. We look forward to seeing more results from your studies and having you on our podcast again.

[00:26:23] Oluwatunmise Dada: Thank you very much, Nataliya, and thanks for having me.

[00:26:26] Nataliya Shcherbatyuk: That’s it for today and until the next episode. You can find more information by following us on Instagram and LinkedIn by @mulch_matters and going to our websites (www.smallfruits.wsu.edu) and choose ‘Mulch Technologies’. This work is supported by Specialty Crops Research Initiative Award 2022-51181-38325 from the USDA National Institute of Food and Agriculture. Any opinions, findings, conclusions, or recommendations expressed on this podcast are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.