Plastic or reusable bag?

February 28th 2014, I posted this on Twitter...

You want to be #GREEN, use #plastic bags... forget about those "green" bags that use resources: http://t.co/Mt7A9d3Xlh
— Simon Filiatrault (@SimonFili) February 28, 2014

And got this response

@SimonFili I'm so confused... next you'll be telling me ethanol is not Green fuel but #nuclear is. #paradigmshifts
— Atomik Rabbit (@Atomikrabbit) March 1, 2014

This warrants a bit more explanation than just 140 chars twitter feeds contains.

The news I linked to is this:

Plastic bags can be recycled into diesel fuel

Here's some excerpt from this new:

• Given that each year an estimated 100 billion shopping bags are thrown away in the US alone, this is great news indeed.
• we can recover almost 80 percent fuel from it through distillation.”
• The process works by heating the plastic bags in an oxygen-free chamber to obtain the oil.
• through pyrolysis into different petroleum products, and have achieved their goal of producing a fuel that meets the standards for ultra-low-sulfur diesel and biodiesel fuels.

So this is indeed great news, we can now recycle those plastic bags and renew them.

One may ask...
Does this become a renewable resource?

This is a complex question... like Atomik Rabbit commented... on Ethanol and Nuclear.

The important concept here to understand is about physical economy. Physical economy has nothing to do with money or maybe a little bit, since money is a mean to exchange work. But let's not get into this now.

Humans consume resources, that we understand.  What is less understood is that for each resources we use and "consume", we need energy to transform it.  I put consume in quote here because we don't really consume resources in the sense that the resources is gone (apart from energy), we only transformed it.

Take for example your toast in the morning.  You used energy to grow, extract, transform wheat in the form of bread, need energy again to cook it.  Then you consume the toast.  Did we loose that resource, the original wheat? No, we simply transformed it.  We did loose part of the energy in the process, because we probably used a mix of energy from fossil fuels, nuclear, hydro to do the transformation.  Part of the energy used was also transformed, like burning fossil, you create CO2 which is used by plants through photo-synthesis to grow.  The more they have the happier they are.

Other source of energy like hydro, you simply moved water around in a endless cycle.  For nuclear, you use the energy stored in unstable atoms by a fission process and created new elements, this is another type of transformation, but the energy used in the process, is lost in a sense, you cannot simply re-used once the work is done.  You may have added energy in form of heat to the system, but in the end, this will be lost in space.

So the question is, what type of energy make sense to use and which process/type is better for the whole physical economy of the planet ?   This seems a complex question, but in the end, you can boil it down to a simple "black box"!  Energy in - Energy out.

Here we see that for any energy system, you will have:

• An input of energy
• To create the system: Metal, concrete and other basic elements
• To feed the system: Wind, Solar, Nuclear, Fossil sources
• And output of energy
• In the form of resources (heat and elements) and electrical energy

The system that make more sense from a physical economy point of view is where the ratio of Out/In is the largest. This equate to energy density. The more dense the energy source, the more OUT you will get for the IN you put in.  This transform in cost, normally cents/kWh.

You also need to take into account the following:

• Availability of the resource to feed the system
• Impact on other system (humans, nature, , etc)

From a physical point of view, Nuclear fission used today in over 450 nuclear power stations, is the most dense form of energy.  Wind and Solar is the less dense. There's a factor of 6 million between Solar and Fission.

So from a physical economy point of view, the more dense you are the better.  This graph tells it all. I needed an exponential Y axis to compare all sources since the difference is so great!

So to get back to the original question, is it good that we can recycle plastic.. I would say, sure it's good, but at what cost.  We have for now plenty of Fossil resources, but for how long?  So from a storage perspective, it's probably better to recycle plastic if the cost is not prohibitive, but it would not make sense to use energy from fossil fuels (low density) to recycle plastic... If we could use the high density electricity from Nuclear to recycle all the world plastic cheaply to use in transportation where we don't have a good solution yet on the electric side... that would make sense. 

There's also the pyrolysis process that can recycle about anything... A plant is in operation in Ottawa, Canada from the company Plasco Energy.

For the question about ethanol... For sure, this has been proven many time that using corn (that uses large amount of fossil) to produce ethanol does not make sense in any way... it's been called a crime against humanity by the UN food program.

You will find on this blog many article about energy, nuclear and other types... Again, we need to have the best ratio of IN/OUT in any human endeavor.  Having a ratio close to 1 for solar/wind, does not make sense.  The ratio is greater for coal and gas, but why would you want to burn a limited resource where you can use a higher density one like nuclear.  Unfortunately, the anti nuclear and all the regulations have push the price point of nuclear over that of cheap shale gas... but this cheap shale gas will not stay cheap and available for ever.  So like any greedy wall street banker can tell you... there's money to be made now on the shale gas, but from a physical economy point of view, we should keep this resources for all other usage outside electricity generation.

About the reusable bag thing...  Here's an interesting information from wikipedia:

One reusable bag requires the same amount of energy as an estimated 28 traditional plastic shopping bags or eight paper bags. "If used once per week, four or five reusable bags will replace 520 plastic bags a year" according to Nick Sterling, research director at Natural Capitalism Solutions. ^[1] A study commissioned by the United Kingdom Environment Agency in 2005 but never published found that the average cotton bag is used only 51 times before being thrown away.^[2]

So you need to use your reusable bag, 28x.  And people use it only 51 times!  So if you recycle those plastic bags and recover 80% of the energy to be re-used in diesels transport, than not sure you save a lot with re-usable bags.... Again, the whole IN/OUT black-box need to be calculated to see what makes more sense... But for sure, I like better the re-usable bags... Can put more stuff in them and better handles!


So here's my quick answer to a simple 140 char comment!

Comments are welcome.

Simon