When analyzing pros and cons of substrates with a wider perspective, we should also consider the carbon footprint. Substrates produced far away have to be transported over long distances, which is costly for the environment. A typical example is coconut fiber, that is produced mainly in India or Sri Lanka and then shipped to America and Europe. Other materials, require high temperatures for their manufacture, and thus consume a lot of energy. Rockwool and perlite share this problem.
Many materials can potentially be used as horticultural substrates. We already said that the ideal substrate for you is the most accessible, cheap, that covers your needs. If you care for the environment, there are benefits in choosing local and recycled materials. These sometimes come from unexpected sources.
Some years ago we got to evaluate a volcanic material extracted from a quarry at the geographic center of Spain. The company which owns the quarry (Lafarge Company) makes cement, but wanted to know if their surplus could be used as a substratum for agriculture. They were wondering if the greenhouse industry in nearby Almería could become a new market.
We studied the physical and chemical characteristics of the material to determine if it would allow to fit the fertigation to the needs of the crop. Our results showed that the volcanic rock is a fine horticultural substrate, capable of producing crops as successfully as other commercial substrates.
- The texture remains homogeneous after several cycles of culture, unlike other materials that degrade or decompose (rind of almond or rice, for instance).
- The production does not need a lot of energy. The material is obtained through direct extraction from a quarry and subsequent controlled grinding and sieving, without high temperatures.
- The quarry is near the zone of greenhouses (less than 400 km), so transportation costs are low.
The principal disadvantages of the volcanic rock are similar to those of the sand.
- It retains little water so it requires frequent watering.
- It is heavy.
Often there are different solutions to the same problem. We need to think out of the box in order to find the ones that are better. Thanks for taking the time to think about the environment.
All physical, physical–chemical, and chemical parameters of the volcanic rock were determined using European standard analytical procedures.
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The complete study is published here: