MARIDA S. DE GUZMAN
Parayao National High School

Investigatory Project
TITLE: Effect of the Different Types of Substrates on the Biodegradability of Robinson Plastic Bags
Background of the Study
Official figures show that plastics make up around 25% of the garbage that metro manila churns out, while an independent survey conducted by Eco waste Coalition and Greenpeace on the composition of discards on manila bay in 2006 found that 51% were plastic bags,19% sachets and junk food wrappers, 5% Styrofoam, 1% hard plastics,10% rubber, 13% biodegradable wastes Biodegradable plastics are degradable plastics on which the degradation results from the action of naturally occurring micro-organisms such as bacteria, fungi , and algae. These plastics are broken down into water, carbon dioxide, methane and biomass primarily through enzymatic action on microorganisms. Biodegradable will fully disintegrate in six months or less. It turns into powder and blends with the soil after a few months. Many biodegradable plastics will decompose in industrial plants, backyard compost piles, or open environments. The inherent biodegradability of plastics depend on several environmental factors such as moisture, temperature, surface area, and the manufacturing method of the finished product. Although some brands claim to be biodegradable in open air and saltwater, virtually no decomposition occurs within a closed land fill that has been capped, preventing air circulation. The Robinson mall chain has started shifting biodegradable plastic bags for its supermarkets and department stores. The use of biodegradable plastics help lessen the burden of the ever-growing garbage problem in the Philippines and in the whole world
REVIEW OF RELATED LIRTERATURE This study was conducted to answer the following problem: Will exposing the Robinson plastic bags to different substrates such as compost soil, loam soil, tap water, and seawater over a period of time affect its biodegradability?
Methodology
If Robinson plastic bags will be placed in different substrates over a period of time, then its biodegradability will be affected.

Objectives of the Study A. General Objective: To determine the effect of different substrates on the biodegradability of Robinson plastic bags.
Specific Objectives: To expose Robinson plastic bags to different substrates such as compost soil, loam soil, seawater and tap water for a duration of several months.

To measure the weight of the plastic bags (grams) before and after different exposure periods to the substrates.3.To compare the percent weight loss of the Robinson plastic bags exposed to different substrates after a period of time.
MATERIALS:
6, 1-litre glass jars
6, 7”x9” aluminium trays
12 pcs. 3”x4” SM plastic bags
500g loam soil
500g compost soil
500mL seawater
500mL tap water
Analytical balance
Graduated cylinder

Weighing scale C. Procedures We cut the Robinson plastic bags into 3”x4”sizes strips. We label led the plastic strips into C1, C2, C3 for compost soil, L1, L2, L3 for loam soil, S1, S2, S3 for seawater, and T1, T2, T3 for tap water treatments. We then determined the initial weights of the plastic strips in grams using the analytical balance. The initial weights (W1) of the plastic strips were then recorded in our log book.
RESULTS
On September 24, 2008, 22 days after the plastics were submerged to the different substrates, the plastic strips were harvested to observe any physical change. No physical change was observed in any of the strips. On October 6, 2008, a month after the immersion, the plastic strips were again observed. No physical change was seen in any of the plastic strips. On November 8, 2008, 66 days after the plastic strips were immersed, they were harvested, washed with tap water and air dried for 48 hours. This time, almost all the strips showed physical changes such as the appearance of small holes, thinning in some portion, and discoloration