What is Waste? – Part 2: Where Did Muda, Muri and Mura Come From?

What is Waste? – Part 2: Where Did Muda, Muri and Mura Come From?

In the last post “What is Waste – Part 1: Why Waste Energy?” we covered the origin and meaning of “waste” in the Toyota Production System and I made some assumptions as to the thinking of the Toyota engineers (including Ohno) when they came up with the idea of “waste” and “work”. I even brought in the ideas and principles of “thermodynamics” to explain their thinking and rational.

Let’s dig a little deeper! (But you may want to review that last post if you have not yet read it).

Remember that Ohno’s equation:

Present capacity = waste + work

is equivalent to the first law of thermodynamics:

E = Q + W

If we break the heat term Q down further within thermodynamics, in its simplest form, we get the equation:

Q = TS

Where T is the “temperature” of the system and S is the “entropy” of the system. I’m sure everyone is pretty conversant with temperature and some may be familiar with the concept of entropy. But I’m not sure how many are comfortable with the concept that these two entities, when combined, constitute heat. Or how these two entities can help us better understand the inner workings of what we are calling system “waste” in TPS/Lean. But I’m pretty sure the Toyota engineers knew.

Let’s start with the more straightforward variable, temperature (T). To quote Oxford Professor Peter Atkins:

Temperature is just a parameter that summarizes the relative population of energy levels in a system”.

He goes on:

That states of higher energy are progressively populated as the temperature is raised means that more and more molecules are moving (including rotating and vibrating) more vigorously about their average position. Turmoil and temperature go hand in hand” [Emphasis mine]

Just keep that last sentence in mind as I go through this analysis.

Now let’s consider one of the more obtuse of all thermodynamic parameters, entropy (S). I’ll quote Dr. Atkins once again:

“Whereas E is a measure of the quantity of energy that a system possesses [Present Capacity], S is a measure of the quality of that energy: low entropy means high quality; high entropy means low quality” [Emphasis and bracket mine]

Entropy is usually associated with disorder. The higher the entropy of a system, the more disordered it is; the lower the entropy of a system, the more ordered it is. For our purposes, I think an even better description of entropy is this:

Entropy is an indicator or measure of the effectiveness or usefulness of a particular quantity of energy

The higher the entropy of a system, the less effective and useful it becomes. One last definition:

Entropy is a thermodynamic property that can be used to determine the energy not available for work

I think you can see where we are going with this.

So temperature is a reflection of the turmoil existing in a system and entropy is a reflection of the effectiveness and usefulness (quality) of the energy within the system. If I were operating a system (my business?), I would want both parameters to be as low as possible.

Which brings us to the title of this post: “Where Did Muda, Muri and Mura Come From?”. Mr. Ohno only mentioned these three Japanese terms once in his book Toyota Production System and not at all in Workplace Management. But over the years many consultants (Shingo being one of the most notable) have emerged from Toyota, most if not all being engineers, and have freely used these words to describe process waste. So it seems pretty clear that these three terms were widely used within Toyota itself and have then spread throughout the TPS/Lean community outside of Toyota. But no one outside Toyota seems very comfortable with these terms. What is their origin?

Based on what you have read so far, anybody want to make a guess?

Here are the most common Japanese-to-English translations for the three words. (By the way, in Japan these words are plain everyday words – they are not technical terms):

Muda: unnecessary, waste

Muri: unreasonable, impossible, overburden, overwork

Mura: uneven, inconsistent, unwanted variation, unwanted fluctuation

I think that about nails it.

Muda: heat (Q)

Muri: temperature (T)

Mura: entropy (S)


Muda = Muri x Mura

So Muda is heat: energy expended for non-work (waste). And Muda can be broken down into Muri and Mura: turmoil and disorder. (I personally like to think of Muri as intensity because it starts with the letter “i” and Muri ends with “i” and I can remember it versus Mura).

Another key thing to remember is that Muda (waste/heat) is the product of Mura and Muri, not their sum. Muda = (Muri x Mura) not (Muri + Mura). Thus things (waste energy) can heat up very quickly (pun intended) if both Muri and Mura are increasing at the same time – which is very likely. Consider a workplace that is very disordered (Mura). What usually happens? People have to work harder (Muri) to get things done. And people working harder usually leads to more disorder, which leads to….you know the drill. We have a word for that too – it’s called “firefighting”.

So why have I gone to all this trouble to explain these concepts? I hope these concepts can be useful to help us identify waste in our businesses, work places, supply chains, etc. if we are relying on the “seven wastes” alone, seeing the waste in our value streams can be difficult at times, particularly if we are working with non-manufacturing systems. The 3M’s give us another vantage point and another set of eyes to find that waste.

In watching the evolution of Lean over the years/decades, I have noticed that people are beginning to lose the focus on flow and waste in their systems when applying Lean. All too often, when reading various blogs and forums, I see Lean devolving into “let’s all work together nicely and try to make things a little bit better”. Sounds pretty empty to me. No wonder Lean is said to fail in over 70% of its applications. Lean, at least in the beginning of a launch, should be revolutionary not evolutionary!

In my humble opinion, these concepts – the 3M’s – if understood correctly, give us a key tool to help answer the question about “why Lean works”. I will try to explain this in Part 3 of “What is Waste”.

2 thoughts on “What is Waste? – Part 2: Where Did Muda, Muri and Mura Come From?

  1. Nice further development of the analogy. Is it your idea, if so, congrats on some original thinking — I’ve never heard waste tied to Thermodynamics before. By the way, I suspect Thermodynamics isn’t part of most Industrial Engineering curriculum’s, i.e it wasn’t when I was in school.

    1. Thermodynamics can be used to better understand the transfer of energy in any system, including those created by man. But there is one problem with the “man-caused” systems – man, himself, usually doesn’t usually follow the laws of thermodynamics. Something about “free will”?

      But I realized the applicability of thermodynamic laws to Lean/TPS when I was writing a peer-reviewed research paper on atmospheric thermodynamics a few years ago. (You’ve got to do something to keep busy when you retire – right? You can find a link to the paper in the About page). The first and second laws apply when you take the brain part of human action out of the equation. But it gets a little unpredictable when that pesky human brain keeps forcing itself back in!

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