Coco coir substrate basics
December 6, 2021
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July 20, 2022
Introduction
A few posts ago we discussed different properties of coconut coir, Rockwool, and peat moss, as well as what these properties mean for plant growth. However, we have not compared yet how sustainable it is to use each of the growing media.
Agricultural industry is impacting the environment just like any other. Because of the large production scopes, almost every choice in vegetable, berry, and fruit production can make a significant difference. For many crops, growing media makes up not only a large part of the costs, but also a large part of the waste.
We are here to investigate environmental sustainability of each substrate and find the most optimal solution for your plants.
Peat moss
Mining of peat moss is extremely harmful for the environment. Peat bogs (or peatlands) are formed over thousands of years and regenerate very slowly. They store around a third of all soil carbon, which got locked up inside them after the plant structure of mosses turned into peat. These bogs are likely to have captured more carbon dioxide than all the world’s rainforests. When they are disturbed, big quantities of carbon dioxide are released into the atmosphere, significantly contributing to greenhouse emissions.
Water has to be drained away from a bog in order to extract peat moss, which dries a bog out and it eventually dies. After that, all surface vegetation is removed and the surface layer is dried in the sun. Dry layer on top is then harvested and sold all over the world. Peatlands are crucial and fragile ecosystems that are seriously disturbed by peat moss extraction. They are not only home to many unique plant species and wildlife, but also nature’s water purifiers and flood preventers.
There is a very high chance that peat moss will not be used in agriculture in the future. The UK government is planning to completely forbid use of peat among amateur gardeners by 2024 and we believe that many other countries will follow their example, extending the ban to professional agriculture too.
Rockwool
Rockwool is one of the most popular growing media but it comes with major environmental concerns. Production of rockwool creates irreversible chemical bonds, which makes it extremely durable. Even if broken down into individual fiber strains, rockwool is not biodegradable and will probably never decompose. Huge amounts of used rockwool is disposed of into landfills every year, creating an ecological problem for many countries.
Similarly to microplastics, it is eventually harmful to the health of both humans and animals. Some studies reported that rockwool is the most harmful growing media to human health.
Apart from that, production of rockwool is very energy-intensive, making the carbon footprint of the industry very large.
Coconut coir
Coconut coir is often regarded as one of the most sustainable growing media out there. It is manufactured from coconut husk, which is a waste product of many coconut-based products. Coconut industry does not cause deforestation like, for example, palm oil cultivation. Water for coconut growth and washing of the raw material comes mainly from natural precipitation, and drying of coir is done open air in the sun without using other energy sources.
Dry coconut coir is also commonly compressed into blocks and slabs, which expand 3-5 times upon addition of water. This allows transportation of large volumes of growing media in just a fraction of the space, therefore reducing its carbon footprint. However, transportation to some locations can take quite long since coconut coir production is mostly limited to just a few countries, mainly Sri Lanka, India, and Indonesia.
Sources
QUANTIS. Comparative Life Cycle Assessment of Horticultural Growing Media Based on Peat andOther Growing Media Constituents 2012. Available online: http://epagma.eu/evidence-based.
D. Bek, M. L. Turner (May 19, 2021) Peat compost to be banned – luckily, green alternatives are just as good for your garden. https://theconversation.com/peat-compost-to-be-banned-luckily-green-alternatives-are-just-as-good-for-your-garden-160315
Gruda, Nazim. (2019). Increasing Sustainability of Growing Media Constituents and Stand-Alone Substrates in Soilless Culture Systems. Agronomy. 9. 298. 10.3390/agronomy9060298.
A. Higgins, The Washington Post (May 11, 2017) Is this popular gardening material bad for the planet? https://www.washingtonpost.com/lifestyle/home/should-sustainable-gardeners-use-peat-moss/2017/05/09/1fc746f0-3118-11e7-9534-00e4656c22aa_story.html
