Mad About Science: Garbage science

By Brenden Bobby
Reader Columnist

It’s not much of a secret that 21st century humans have a garbage problem. We generate huge amounts of waste — a problem that’s compounded by our pursuit of increasing efficiency. A new toy comes out and the old one joins its packaging in the trash bin, never to be seen again.

Unfortunately for us, there is no [destroyObject] function in the real world. Due to the law of conservation of mass, matter cannot be created or destroyed; it simply changes shape. This means that every time an item lands in the waste bin, it has to travel somewhere.

Fortunately for us, we can utilize the law of conservation of mass to our benefit. The item might take up space, but it’s not going anywhere. Why not use it a little bit longer and learn something from it?

Soda bottle transportation

Two-liter soda bottles are the definition of modern human wastefulness. Wooden buckets, clay carafes and corked glass bottles performed this job for millennia before plastic bottles started floating around our oceans. Fortunately for us, they’re designed to be aerodynamic and perfectly suited to move with a little help.

There are countless ways to build an efficient bottle rocket, and a number of ways you can fuel them to achieve lift. The most basic design is to take an empty bottle, flip it upside down and stuff a bike pump with an airtight seal in the spout. Pump that bad boy to maximum, and let the sudden release of air pressure carry the bottle skyward.

If you’re really feeling adventurous, see what additions to your rocket could make it more efficient. Add fins, a nose cone or different fuel types like baking soda and vinegar — really make it your own. Just be sure to wear safety goggles when handling projectiles, and use common sense: Do this in a lonely section of the park, not in the middle of your neighborhood where it could hit a house or a car.

Plastic bottles can also be used to make race cars instead of rockets. See what other objects destined for the trash bin might make for effective axles and wheels. You can power your garbage racer the same way you power your rocket.

Just be sure to never use flammable liquids to power your vehicle. The plastic is not designed to withstand those kinds of forces.

Vertical garden greenhouse

Have you ever wanted your own greenhouse, only to be smacked in the face by the absurd cost of glass, wood and contractor fees? Those $2 bottles of soda or $9 bottles of wine your family tosses in the trash every week are ready-made greenhouses that were built for verticality.

Fill the bottom fifth of the bottle with small rocks, then pour some garden soil over top until about a quarter of the bottle is filled. Sprinkle your seeds in and then add water. You can seal the top to create a terrarium, or simply put the cap back on so you can water as necessary.

You can use a length of twine or burlap garden rope to hang these from a frame or porch railing to create a layered vertical greenhouse garden. Wrap the twine around the spout of the bottle, or create a more secure fisherman’s style netting around the bottom.

While you might not be able to grow a prize-winning pumpkin in one of these, you might be surprised at the number of vegetables you can produce with this method. Experiment with different levels of dirt, try jabbing some holes through the base to let water escape, or even see if you can figure out how to construct a condensation catcher inside of the bottle to create a self-watering device.

Biofuel and heat

This experiment has some practical applications but requires more specialized technology to be really useful. However, it’s an interesting way to watch the entire decomposition process from start to finish, and also record the amount of waste it generates.

If you have bits left over from dinner that you couldn’t eat, cram them into a bottle and seal the top with a balloon. Be sure to tie the base of the balloon to the spout of the bottle. Let nature take its course and you should see the balloon begin to inflate over a period of days as the leftovers begin to rot. Additionally, you might notice the bottle begin to heat up.

The bacteria inside are breaking down and composting the materials, and they’re generating methane gas as waste. Methane, as you might know, is at least 28 times more potent as a greenhouse gas than carbon dioxide.

See how much the balloon inflates and use a measuring tape to see how much area the gas has taken up. Now try to imagine 7.9 billion people doing this, and the amount of gas produced becomes startling. This experiment is a good way to quantify food waste and the unseen effects it has on our environment.

Methane isn’t all bad news. It can actually be burned as a fuel source to power things like factories or even heat a home. When methane is burned, it produces carbon dioxide and water as waste products, while also producing heat energy that can then be transferred to water tanks that pump into a coil that radiates the heat, which is then blown through the house’s ductwork to warm the air. 

You definitely don’t want to do this with your balloon full of methane. In fact, you may want to plug your nose when you break down this experiment, as it’s bound to stink.

If you’re using vegetable scraps, you can compost them and put them into your garden. If you decide to use something fatty like meat to produce more methane, you will want to keep the bottle sealed once you’ve thrown it away. Your nostrils will thank you for it.

Stay curious, 7B.