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Do water-efficient irrigation systems work against low-carbon goals?





The carbon footprint of any given material is not necessarily obvious or even intuitive.

This brief intro should help you begin to wrap your mind around it.


First, we need to simplify our understanding of what causes a material to have a high carbon footprint.


There are two main areas that drive extremely high carbon footprints for materials.


1.   Does the base material require a blast furnace to create it?

2.   Is the primary feedstock for the material oil?


 

1. Does the base material require a blast furnace to create it?   


Steel and cement (the key ingredient in concrete) both require incredibly

high temperatures to create.

These high-heat production systems use enormous amounts of energy, usually derived from burning coal. In addition, the end product is heavy, so shipping it around the world takes even more carbon.  


High heat = high carbon footprint

 


2. Is the primary feedstock for the material oil?


Basically, is it plastic?


The carbon footprints of plastic and steel are not that far apart when compared pound for pound.


Plastic = high carbon footprint

 

End Weight Matters in this equation  


When considering carbon, the physical weight of something and what we get for that weight should be considered.


This means that we ultimately measure your material's carbon footprint based on its total weight, which is measured across the entire project.

Weight is not distributed equally throughout the length of different materials and, therefore, not equally distributed throughout your projects.


Let's look at 1 linear foot of 1/4" steel edging and 1 linear ft. of 1/2" drip line.


1/4" steel edging= 14.9 pounds of Co2/ft

1/2" drip line= .09 pounds of co2/ft.


As you see, the carbon footprints of these two products per linear foot are very different, even though the base materials have a similar carbon footprint. This is due to the end weight of the material and the amount we need to use to meet our goals.


Given the dramatic difference in per-pound weight, 10 pounds of plastic pipe can go much further on a project than 10 pounds of steel.


(Create an image of linear feet covered by each)

Now, the point of this is not to suggest that we need to stop using plastic or steel.

The goal is to help you contextualize carbon footprints and how the product weight and footprints are spread throughout a project. There are not equal outcomes just because they have similar carbon footprints per pound of raw material. It comes down to the total pounds used and the X footprint per pound of the end product you are using.


 

Water-efficient irrigation systems and low-carbon goals


And now, we can more clearly discuss how water efficiency and low-carbon landscapes are currently at odds with each other.


We all know by now that drip irrigation is up to 90% effective. That is a fantastic number!


This efficiency does come at a cost.


On medium to large gardens, We can literally use MILES of drip tubing when designing an inline system laid out on a grid.


So, using Bond, I have calculated the footprint of the drip system and tallied the sequestration rates of the associated plants it will irrigate to determine how long the plants will need to sequester enough CO2 to offset the drip tubing emissions.


Sample Study


Let's have a look at a 6,400-square-foot mixed perennial garden.

Let's assume a high valve count for a well-managed and flexible system.


Our total irrigation system costs approx. 7,695 pounds of CO2 (without final transportation to the site)


That garden is going to sequester approximately 1,777 pounds of CO2 per year.


Given these numbers, the garden will take 4.3 years to sequester the irrigation system's carbon emissions.


But what else is this garden expected to offset?


4.3 years doesn't sound too bad. But that same garden needs to absorb all of the hardscape, grading, transportation, etc.- everything that is part of the project's landscape/hardscape.


When I add in all the hardscape, lighting, transportation, and construction impacts, The entire project referenced above takes 23.2 years to sequester the carbon emitted to build it.

 

There is no silver bullet to carbon-literate landscapes, but there is a path through


There is no one thing. Each project needs to be looked at to see where and if we have leverage points. Some projects have many, others very few. The carbon issue will not be solved easily. That is the hard truth here. deep down, we all know this.

We are working within an economic and social system that is built upon carbon illiteracy.

We must continue to use our creativity to find viable solutions based on your project's requirements. They are there, we just have to find them.


There is no advancement too small at this stage.


It provides a much more effective view of landscape-based solutions. I think it will help you advance your work more easily.


For a more in-depth look, please click here for a long-format podcast discussing the Three Pillars approach and its associated software.


 

rick

Founding Principal, Elder Creek Design Studio


To further his commitment to ecoliteracy in the landscape, Rick has founded Sandbox, a software company providing ecoiliteracy tools for Landscape professionals. Sandbox's first product is Bond, the world's first and only landscape carbon calculator that includes the full carbon impacts for both material choices and construction activity.


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