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Comparing Degradation Rates of Biodegradable Materials in a Composting Environment

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Composting is the aerobic process of recycling organic materials into usable fertilizer. Polylactic acid (PLA), commonly used in biodegradable utensils, is an organic material continually tested for complete degradation in southern California composting. PLA's ability to decompose can decrease a market for non-biodegradable plastics, decreasing the amount of single-use plastic material in county landfills. The Living Coast Discovery Center (LCDC) in Chula Vista, California regularly uses and composts World Centric biodegradable utensils in their Compost Demonstration Garden. The purpose of this study was to measure and compare the rate of degradation for two types of biodegradable materials: PLA and wood. Cups, forks and spoons in each material were placed on a wire grate inside separate LCDC outdoor compost piles for ten weeks, using labeled strings to locate each item. Once a week, both piles were aerated by transferring compost to new stalls, monitoring temperatures for the microorganism aerobic activity and weighing utensil masses periodically. Grates containing the utensils were also transferred. PLA and wood rates of decay were determined by subtracting initial mass from final mass, weighed on a microbalance to within 0.001g, and divided by the 70-day compost period. PLA and wood cups degraded 100%; PLA utensils lost 0-2% total biomass, decaying daily at a rate of 1.14%. Wood utensils lost 8-52% total biomass, decaying daily at 1.74%. At larger compost facilities, higher degradation rates are expected of both materials; smaller piles limit thermophilic activity. Composting biodegradable materials can decrease long-term landfill waste and promote production of sustainable goods.

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Comparing Degradation Rates of Biodegradable Materials in a Composting Environment

Composting is the aerobic process of recycling organic materials into usable fertilizer. Polylactic acid (PLA), commonly used in biodegradable utensils, is an organic material continually tested for complete degradation in southern California composting. PLA's ability to decompose can decrease a market for non-biodegradable plastics, decreasing the amount of single-use plastic material in county landfills. The Living Coast Discovery Center (LCDC) in Chula Vista, California regularly uses and composts World Centric biodegradable utensils in their Compost Demonstration Garden. The purpose of this study was to measure and compare the rate of degradation for two types of biodegradable materials: PLA and wood. Cups, forks and spoons in each material were placed on a wire grate inside separate LCDC outdoor compost piles for ten weeks, using labeled strings to locate each item. Once a week, both piles were aerated by transferring compost to new stalls, monitoring temperatures for the microorganism aerobic activity and weighing utensil masses periodically. Grates containing the utensils were also transferred. PLA and wood rates of decay were determined by subtracting initial mass from final mass, weighed on a microbalance to within 0.001g, and divided by the 70-day compost period. PLA and wood cups degraded 100%; PLA utensils lost 0-2% total biomass, decaying daily at a rate of 1.14%. Wood utensils lost 8-52% total biomass, decaying daily at 1.74%. At larger compost facilities, higher degradation rates are expected of both materials; smaller piles limit thermophilic activity. Composting biodegradable materials can decrease long-term landfill waste and promote production of sustainable goods.