Input-Output Analysis
Posted on di 09 september 2025 in tools
This analysis is a way to track different flows across our systems and how the output flow of one element can be used as the input flow to another element in our system.
Every output stream that is not matched to an input is a waste stream. And for every input stream that is not provided for by an output of our system, we need to bring this into the system from outside.
Example
Consider a system with the following elements and a number of their inputs and outputs:
| Element | Input(s) | Output(s) |
|---|---|---|
| compost bin | scraps | compost |
| kitchen | food stuff, fruits/vegetables | scraps, food, packaging |
| chickens | feed, scraps | eggs, manure |
| garden | compost, manure, seeds, fertilizer | food |
| human | food | human manure |
In this example, we can match the following outputs to inputs: the output of the compost bin can go into the garden, the fruits and vegetables from the garden into the kitchen and the food scraps from the kitchen are for the chickens and the compost bin. Manure from the chickens can also go into the garden. The human eats the food from the kitchen.
Here's a graph showing all the input and outputs mentioned as well as the external inputs and the waste. Just in this small example, we can already see a high degree of inter-dependency.
Input-Output Analysis from our example system
If our aim is to become more self-sufficient we need to find ways to source seeds, fertilizer, food stuff and feed from within our own system. In addition we need to find ways to use the waste streams of human manure and packaging.
Some proposed changes to our system could include a composting toilet, turning human manure into compost. We could try reusing packaging for long term food preservation, reducing the amount of packaging that leaves our system as well as the amount of food stuff we need to source from the shop. If we save our seeds from the garden, we reduce the need to go seed shopping.
This analysis is far from complete. There's the tools we use in the kitchen and the garden. The garden needs a steady supply of water. We're also missing the construction materials for the compost bin and the chicken coop. We're missing the house the kitchen is located in and its demands for maintenance (that is, materials, tools and energy). The energy used in the kitchen for cooking also comes from outside, unless we're using wood we've collected from our property.
An Input-Output Analysis give us a way to visualize and appreciate the complexity of our system and its connections to the larger systems it is a part of. It can show us where we need to focus our efforts to reduce our dependency on Industrial Civilization.
How to begin
We need a list of elements that make up the system and the different flows between them.
First make a survey of the system using Nine Ways of Observing and maybe do a Flow Survey next. These two tools will give you a comprehensive list of elements and flows to use as inputs to the Input-Output Analysis.
As you do this analysis, you may discover new flows or new elements that you may have missed the first time. It is good to go back to the surveys and add these flows and elements to them.