Upcycling distillers spent grains into biodegradable nursery pots

As the bourbon distilling industry continues to grow, there is also an increase in the amount of waste produced, including distillers' spent grains (DSG). DSG is categorized as hazardous waste due to its negative environmental impacts, including significant nutrient loading and water acidification. Additionally, the agricultural industry produces approximately 500 million plant pots and similar plastic waste annually, with only 10% of this material being recycled. Commonly, these plastic pots – called nursery pots – are used to germinate seeds before planting them into the ground. The goal of this project is to utilize distillers’ spent grains to produce a biodegradable nursery pot with mechanical properties that enable high-quality plant growth, comparable to those of industry-standard plastic pots. Throughout the project, DSG is mixed with alginic acid and calcium sulfate with varying mass ratios. Two drying methods were evaluated: ambient drying and lyophilization. Three-point bend testing was used to evaluate the flexural strength of the samples via Young’s modulus. Nursery pot prototypes were shaped with a 3D-printed mold and a hydraulic press. The prototypes were compared to industry-standard nursery pots through testing mechanical properties, water retention, and a 6–8 week observation of tomato plant growth and leaf production. DSG pots did not perform statistically differently from industry-standard nursery pots during the growth tests, indicating that DSG nursery pots have the characteristics to be a feasible alternative to plastic nursery pots.