We first set up a system for aerobic degradation based on ASTM D5338-15. The system includes three bioreactors: the first one for the blank (All Seasons Bokashi™ Compost Starter + Odor Controller), the second one for the blank and cellulose, and the third one for the blank and a pressure sensitive adhesive (PSA). Each bio-reactor was flushed with moisture-saturated air that was free of carbon dioxide. The compressed air first flowed through water and then a 1 N NaOH solution at 30 mL/min for the moisture-saturation and removal of carbon dioxide. The air then flowed to the bottom of a bioreactor. The bioreactor is submerged in a 58 °C water bath. The air from the bioreactor was then dispersed in a 0.25 N NaOH solution for absorption of carbon dioxide in the air. The amount of carbon dioxide was quantified through titration. Two PSAs (PSA1 and PSA2) were investigated for their biodegradability under aerobic conditions. Over 90% of carbons of PSA1 was degraded into carbon dioxide within 45 days. The degradation rate of the PSA1 is comparable to that of cellulose. The degradation rate of PSA2 was much slower than that of PSA1. Two PSAs (PSA1 and PSA2) were investigated for their biodegradability under anaerobic conditions based on ASTM D5511-18. Three bioreactors were run simultaneously: the first reactor contains the blank (sludge from local waste water treatment plant), the second reactor contains the blank and cellulose, and the third reactor contains the blank and a PSA. The reactors were purged with N2, sealed with septum, and then placed in a 35 °C incubator. The total volume of biogas was measured by gas syringes. The biogases from each bioreactor was measured for its volume and analyzed with gas chromatography every 12 h in the first two weeks and then every 24 h. The molar percentage of carbon released was calculated. Biogases (carbon dioxide and methane) slowly released from the anaerobic incubation of PSAs even after 120 days of the incubation. The degradation rate of PSA2 was higher than that of PSA1. The degradation rates of both PSA1 and PSA2 were much lower than that of cellulose. The slow degradation rates under anaerobic conditions are not consistent with the fast degradation rates under aerobic conditions. Further study is needed to figure out the reasons for the slow degradation rates under the anaerobic conditions.

Pressure sensitive adhesives (PSAs) are widely used in tapes, labels, medical field and many other applications. PSAs used in this study were derived from soybean oil and cured under radiation of UV light. These soybean oil-based PSAs represent a new use opportunity that can potentially consume a large amount of soybean oil and add values to the soybean oil. The soybean oil-based PSAs have numerous advantages over traditional petrochemical-based PSAs such as requiring less energy-intensive in their production, being very environmentally friendly and being very cost-competitive. However, the commercialization of the soybean oil-based PSAs has been slow. One of the obstacles is that we don’t have the data to show that the PSAs are truly biodegradable. Results from this study reveal that the soybean oil-based PSAs are biodegradable under aerobic conditions. Results from this will facilitate the commercialization of the PSAs, thus adding values to the soybean oil.