Tag: plastic

Paper Bags Are Not Better Than Plastic Bags

By Anupum Pant

Plastic bags are terrible things. They choke animals, aren’t easy to recycle, do not break down, pollute our oceans, their production adds to our oil demands…and the list goes on. Some time back, we realized their ill effects and started taking steps that would encourage people to use bags made of alternative materials. Furthermore, several cities all over the world have banned the use of plastic bags.

Side Note: Interestingly, plastic bags aren’t actually banned for any of those reasons. They are banned because they tend to fly with the wind and move out of your trash fairly easily. They create a mess at places where they aren’t supposed to. That is the major reason as to why they are being banned.

In 2007, San Francisco banned plastic bags for supermarkets and pharmacies. Last year, it got expanded to all retail stores. Now, they have been banned for restaurant takeaways too. Also, the use of plastic bags at retail stores has been banned in several Indian cities. But the point isn’t to list out all the cities where it has been banned. There are many cities. I hope you get the idea…

When it comes to finding an alternative for plastic bags, paper bags seem to be the first choice. But it turns out, paper bags are not better than plastic bags.  Most of us underestimate their ill effects. Here are a few reasons that will make you realize why paper bags are not so good:

The point isn’t to make paper bags look bad or to make plastic look good or vice versa. It is to dispel the image of “the green paper bag” from our minds.

Reasons

Production: Production of paper bags all over the world involves cutting down 14 million trees every year. It is estimated that the production of paper bags creates 70 % more air pollution than plastic bag production.
Production of paper bags also results in much more water getting polluted when compared to the production of plastic bags. This is because their manufacturing process requires a lot of water.
Almost the same amount of petroleum used for plastic bags (for the material) gets consumed in making of paper bags to fuel the machines plus transportation.

Weight: Paper weighs a lot more than plastic. It is estimated that to carry the same number of paper bags it takes 7 times the transportation it takes to haul plastic bags. More trucks, more pollution, greater greenhouse impact.

Space: Paper bags occupy a lot more space than plastic bags do. This creates a problem at landfills that are getting filled to the brim already.

Recycling: Paper bag activists would say, plastic bags live for ever in the landfills. Yes they do, but there, paper bags do not decompose within a meaningful time period either. In fact, most of the stuff lives on for a long time in landfills. Landfills aren’t meant to make things degrade. With a paucity of oxygen and water in landfills, it is hard for things to decompose there. Even food items thrown away at landfills last for years.
That said, even plastic bags are almost never recycled.

Also they tear easily. As a result, more number of paper bags have to be used.

Solution

Both of them – plastic and paper bags – are equally bad. Recently developed biodegradable plastic bags are not any good either (they have a bigger carbon footprint). Carrying canvas, cloth or jute bags and saving them for future use is probably the best alternative.

If you liked this, you’ll probably also like – Understanding the Impending Helium Crisis

4D Printing is Here

By Anupum Pant

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We had just started getting comfortable with printing objects in 3D, and 4D printing is already here. Early this year, in the month of April, Skylar Tibbits, an architect, designer and computer scientist at MIT, gave a revolutionary demonstration explaining their advances in the field of 4D printing at a TED conference. This was an initial proposal and it got things moving at a rapid pace.

Side note: In the world of 3D printing:

What is 4D printing?

At first 4D printing sounds like a catch phrase, it isn’t really just that. 4D printing is actually 1D better than 3D printing and it aims at making objects out of a 3D printer, that can reconfigure themselves into useful shapes, on their own. For instance, think of a non-living stick changing itself into a 3D cube as time passes. In short, 4D printing will enable us to create living objects without any living cells, micro-processors, chips or batteries involved. Sounds simple enough, but the promises are nothing less than extraordinary.

In the TED talk attached below, Skylar explains how a string of plastic placed in water can turn itself into the letters MIT. But, this was something that happened back in April. Things have moved further.

A few days back, Researchers at the University of Colorado Boulder revealed a successful test of their 4D printing technology. They were able to print out flat objects using normal plastic combined with a smart material which was able to turn into a cube on its own. Cubes are just the start.

According to scientists, in the future, 4D printing will probably churn out smart car bodies that would heal automatically, smart soldier uniforms and advanced building materials. Imagine a camouflage material that changes to match the surroundings, that could be the future. Or a pipe that contracts and expands to move water without pumps. Or a building material that builds itself into a structure. 4D printing could probably best suited for building in an extremely hostile environment like space. The possibilities are endless.

But, let us not get ahead of ourselves. It is almost impossible to predict what we’ll actually see in the future. Things have just started to happen in the field of 4D printing. But, it sure looks amazing. What will you build?

Why is a Metal Plate “Colder” Than a Plastic Plate?

by Anupum Pant

No, it isn’t!

What is Cold?

According to the dictionary, a body at a relatively lower temperature, especially when it is compared to the temperature of a human body is described as a colder one. So, any object below the normal human body temperature – about 37 degrees Celsius – is a cold thing. But wait a minute!

When you touch an object, what does it tell you about the temperature of the object? Can you really judge if it is a cold one or a hot one? Unfortunately, our bodies aren’t thermometers, we are not so smart when it comes to judging the temperature. Consider the following case.

A book and a steel plate kept in the same environment for a long time attain the same temperature eventually (it is called thermal equilibrium). This can be checked by using a thermometer on both the objects. But, when people are asked to touch a metal plate and a book, they find the former to be much cooler. You can try this out yourself by touching different materials around you. You’ll see how some things ‘feel colder’ while the others feel warmer. A YouTube channel Vertasium conducted a social experiment to record this on camera. See the video below:

There is no cold – only heat

So, in the video, ice melts faster, if kept on steel plate than on a plastic plate, even when the steel plate ‘feels colder’. Common sense dictates that the colder thing is supposed to sustain the ice block for a longer time, just like your refrigerator does. So why does the opposite happen?

A better way to understand this ‘contradiction’ (not really a contradiction) can be this:

According to thermodynamics, simply put, everything has heat in it. So, even a cold ice block has some amount of heat stored in it (say, around 273.15 Kelvin or 0 degree Celsius). When one object comes in contact with other object, it loses or gains heat till their temperatures get equal or till they attain ‘thermal equilibrium’. Which object loses heat and which one gains it, is decided by their relative temperatures. In case of ice and steel, ice has a lower temperature than steel (assuming it isn’t already freezing out there). Therefore, here, ice gains heat from steel till they attain the same temperature and ice melts.

Side note: The ice is also in contact with a relatively ‘hotter’ atmosphere. Hence, it gains heat from there also. In this case, we are only concerned about the steel and ice interaction.

Why does it melt faster on steel?

There is a particular property which depends on the kind of material and is called thermal conductivity. This is the parameter which decides which objects lose heat quicker and which ones do it slower.

Here, for instance, steel has a higher thermal conductivity than plastic. Hence, the steel plate gives away heat to the ice block faster than a plastic block does. As a result, ice melts faster on a steel plate than on a plastic one.

Incidentally, this effect can also be used to explain why one plate feels colder than the other, in our hands. Think of it like this, the ice is replaced by our hand. So, a steel plate, due to its better thermal conductivity, draws heat faster from our hand than a plastic plate. This makes us feel that the steel plate is colder than the plastic one.

As checked by a thermometer, both the plates have the same temperature, our bodies are only fooled into believing that the thing we feel is temperature; it isn’t. None of the plates is actually colder than the other (according to the dictionary – see first paragraph). We don’t feel the temperature. What we feel is actually the rate of heat being drawn away from our hand. Faster an object draws heat, the colder it feels.