A fundamental element of implementing lean is the ability to recognise and eliminate (or at least reduce) all forms of waste within the value stream. Often in practice, most activities create waste. Waste is anything which does not add value to a product or service, in any office or manufacturing activity, eg : sitting in storage, being moved around, queuing awaiting processing, being inspected, etc.

Taiichi Ohno (of Toyota) defined 7 categories of "Muda" (waste):

Ohno's 7 Wastes :

1. Transport : Movement of materials is a waste. Minimise the amount of movement by arranging processes in close proximity to each other.
2. Inventory : Too little inventory can lose sales, too much inventory can hide problems. Aim for "Just in Time" (JIT) manufacturing to expose problems to be eliminated and reduce cost.
3. Motion : Remove unnecessary motion of the operations and improve the ergonomics of the workplace.
4. Waiting : Minimise waiting time and maximise "value adding" time. Aim for a smooth flow.
5. Overproduction : Always aim to make exactly what the customer orders, just in time, to the correct quality standard.
6. OverProcessing : Use machines which are of an appropriate capacity and capable of achieving the required quality standard.
7. Defects : Reducing the number of defects directly reduces the amount of waste. Aim for zero defects.

These can be remembered easily by using the acronym "TIM WOOD".

The New Wastes

In addition to Ohno's original seven wastes, seven "new" wastes have been added to the list :

1. The Waste of Untapped Human Potential
2. The Waste of Inappropriate Systems
3. Wasted Energy and Water
4. Wasted Materials
5. Service and Office Wastes
6. Waste of Customer Time
7. Waste of Defecting Customers