Effects of Compost Material on Various Degradable Lawn Bags Joe Mautino 9 th Grade Central Catholic High School

Problem Plastic bags are used frequently and add to pollution problems Plastic bags are not thought to readily decompose Composting has been implied as an effective means of recycling organic materials Can composting degrade plastic bags as readily as paper?

Background (Composting) Composting is the transformation of organic waste into compost Main components of composting –Organic matter Brown (leaves, twigs, manure) supply Carbon Green (grass, fruit rinds) supply Nitrogen –Bacteria Mesophilic Bacteria Range (10 C° - 40 C° ) Thermophilic Bacteria Range (40 C° - 65 C°) most desirable –Oxygen Oxygen is used up quickly by the microbes as they metabolize the organic matter Less oxygen, slower composting –Moisture Ideal range is 40% to 60% moisture High moisture causes anaerobic conditions, low moisture inhibits activity

Background (Plastic) Americans throw away approximately 100 billion polyethylene plastic bags a year Made from crude oil –Accounts for 4% of the worlds total oil usage The process of making plastic bags requires large amounts of electricity Does not readily decompose

Background (Paper) Paper production impacts the environment in many ways Collection of timber for production is long and environmentally taxing Water usage –Thousands of gallons of clean H 2 O used to wash and bleach pulp –Paper = 1 part pulp to 400 part H 2 O Disposition of used paper Landfills –Takes many years to decompose Recycle –Requires extensive process to return to pulp

Background (BioPlastic) New biodegradable & compostable plastics derived from cornstarch, Mater-Bi –Made from starch, biodegradable polyester, other natural plasticizers –Claim to biodegrade in days –Biodegradable: degrade from composting into carbon dioxide, water, and inorganic biomass Compostable: Meets ASTM –Biodegradable –Disintegrate –Low eco-toxicity

Purpose To determine the garbage bag that will decompose the most rapidly in a compost pile.

Hypothesis In the test compost, Mater-Bi plastic bags will decompose more than polyethylene plastic bags. The paper bags will undergo the greatest degree of decomposition. Null: No significant variation in decomposition rate will be composted between Mater-Bi, polyethylene plastic and paper.

Materials 10 Mater-Bi plastic 127 mm * 127 mm bag pieces 10 polyethylene plastic 127 mm * 127 mm bag pieces 10 paper 127 mm * 127 mm bag pieces Digital scale (.000) grams 5 L of organic potting mix 15 L of cut grass 900 ml of cheese 500 ml of yogurt 500 ml of cucumber 700 ml of green pepper 400 ml of broccoli 1 22 L metal bucket A small electric heater L insulated bucket 1 measuring cup Appropriate PPE

Procedure Collected and used appropriate PPE Cut mm * 127 mm pieces of each bag (Polyethylene plastic, Paper, and Mater-Bi plastic bags) Weighed each sample and recorded initial mass of each piece Created compost mixture with the organic materials (Approximately 20 L) Placed the compost into a 22L bucket. Mixed all 30 samples (Plastic, paper, and Mater- Bi plastic) into the compost mixture Used a small heater under the bucket and set to 25°C

Procedure Covered the small bucket with the 155L insulated can to keep a constant temperature Used a small shovel to mix compost weekly After 4 weeks removed sample bags from the compost Cleaned bag samples by brushing all excess dirt from bags Let the samples dry overnight Weighed final mass

Polyethylene Plastic Experiment Samples (Control) BeforeAfter

Paper Experiment Samples BeforeAfter

Mater-Bi Plastic Experiment Samples BeforeAfter

Data Average Polyethylene Plastic Bag Average Paper Bag Average Mater-Bi Plastic Bag Initial Weight (grams) Finial Weight (grams) Weight Loss (grams) Percentage of Weight Loss1.47%92.26%4.46%

Anova Single Factor calculations for the Average Weight Loss For the 3 Bag Types Anova: Single Factor SUMMARY GroupsCountSumAverageVariance Mater-Bi Plastic Polyethylene Plastic Paper ANOVA Source of VariationSSdfMSFP-valueF crit Between Groups E Within Groups Total

Percentage Weight Loss for the Average of Each Sample Bag

Observations All elements in the compost biodegraded to rich black soil Mater-Bi plastic showed indications that decomposition had started The Polyethylene plastic did not show any signs of biodegradation Only little pieces of the paper bags were left

Future Improvements Fill actual bags with organic material Improve final cleaning to reduce residual compost on the samples Add additional composting bacteria to accelerate decomposition

Conclusion My alternate hypothesis was proven correct, that in the test compost, Mater-Bi plastic bags will decompose more than polyethylene plastic bags. The paper bags will undergo the greatest degree of decomposition. My null hypothesis was rejected, shown by the P value stated in the Anova calculations.