Keep track of what objects your household recycles for a month or longer. At the end of the month, create a human or animal sculpture using one object you found occurring most often. Research this object for your science project, finding out how many tons of it are thrown away per year, how much energy is required to recycle it and what countries handle recycling it.
Cardboard is a renewable material and is readily available at no cost from the stockrooms of department stores and grocery stores. Cardboard can also create very stable, strong structures. Use cardboard to create a bridge, platform or other structure that demonstrates engineering designs and physics principles. Describe how cardboard is both a unique building material and a low-cost ecological alternative to costlier building materials and insulation.
Collect the plastic bags you receive from grocery stores for a month or longer. At the end of your collection period, cut up the plastic bags into 1-inch pieces of plastic. Place the bits in a large, clear plastic bottle for people to shake. You can research how plastic bags degrade in sunlight and describe the Pacific Ocean's "Plastic Vortex" and how discarded plastic bags threaten oceanic ecosystems.
Collect all the paper you would have normally thrown away over the course of a month. Demonstrate the alternative uses for waste paper as a science project by making your own recycled paper. You can research how much paper is thrown away in landfills per year, how much is recycled, how much it costs to recycle paper and alternative uses for recycled paper. You can use the paper pulp from this project to create your own paper or make bricks or a sculpture.