Plant Compost: Taking Sustainability and Environmental Impact into Account

The Importance of Quality Compost

When it comes to houseplant care there are several different factors to take into consideration. We often place heavy emphasis on light requirements, watering frequency, feeding and fertilizing, among plenty of other things. Yet there is one other component that is often mentioned only as an afterthought, or even overlooked entirely: compost.

A good quality compost is the foundation that supports the healthy growth of your plants. It is the substance within which moisture is retained for future absorption and can also be a nutrient-rich medium that can help promote healthy root, foliage, and flower production.

When it comes to selecting the right compost for your plants the choice can often seem difficult. Many suppliers offer several different varieties with various compositions, amendments, and specializations. One aspect of the selection process that is becoming more and more of a focus is the sustainability and environmental impacts of your chosen compost, with moss peat coming under scrutiny and, as a result a desire from environmentally conscious consumers to seek alternatives.

The Transition from Moss Peat

Sphagnum moss peat, or moss peat is the most widely used and heavily researched growing medium and has been used within Irish horticulture for hundreds of years. However, in 2019 the practise of peat harvesting in Ireland was suspended due to the Irish Government’s desire to switch the national focus towards bog rehabilitation, restoration, and to help tackle the mounting issue of climate change. And with good reason.

Peatlands can be found in almost every country on earth and constitute roughly 3% of the global land surface. Damage to these lands’ accounts for 5.6% of greenhouse gas emissions originating from human activity. On top of this, peatlands are the largest natural store of CO2 globally, exceeding all other vegetation types, including the world’s forests.


The Rise of Coco Coir

The search for a more sustainable, and environmentally friendly alternative has brought the use of coco coir to the table. A bi-product of the coconut farming industry, coco coir is the ‘in-vogue’ growing medium.


After coconuts are harvested, the husks are removed and the long strands from those husks are extracted for use in manufacturing, leaving the unused coco coir as a biproduct of the process. On the surface the use of a manufacturing biproduct seems like the perfect solution as it makes use of a waste product. Unfortunately, it’s not that simple.


To make coco coir suitable for use as a growing medium it must undergo a thorough washing process to remove the high salt content of the husks. In many cases this process is not complete by the time the product reaches the consumer. The excess salts within the coir, comprised mainly of potassium, can inhibit the absorption of calcium by plants leading to complications related to calcium deficiencies.


On top of this the majority of coconut farming occurs in countries such as the Philippines and Indonesia meaning that it must be transported overseas before entering the consumer market, begging the question whether the environmental impact of transportation negates the benefits.


It’s not all bad, however. Coco coir can be dried and compacted making transport easier. A dried 5kg brick of coir can be rehydrated using roughly 18ltrs of water to produce 70ltrs of compost. It also has a very balanced pH making it a good option for plants that prefer neutral soil conditions.

Green composts can vary significantly in quality depending on the producer.

Organic, peat free potting soil

An Organic Opportunity  

This then brings us to another possible alternative, green compost. This growing medium can be produced both domestically, using cold techniques such as those used in household compost bins, or on a larger scale using ‘hot-composting’ techniques, where the decomposition process is accelerated using heat. The compost is comprised of decomposed organic matter such as food waste, wood shavings, bark and other green waste making it sustainable and environmentally friendly.


Like everything, it isn’t perfect. Green composts can vary significantly in quality depending on the producer. Poorer quality green composts can contain pests, seeds from food waste, roots from weeds and can vary significantly in pH. Because of this it is vital to choose producers that specifically state that they screen their compost to remove as much of the roots and seeds as possible, heat-treat their compost to kill any unwanted pests and continuously test the pH of the compost to ensure it is as close to neutral as possible.

The jury is still out in regard to what is the best option as a growing medium. Ultimately we feel that locally sourced organic compost is the most environmentally friendly option.  

Here at Clay we're always trying to reduce our impact on the environment. If you have any suggestions on how we can improve, we'd love to hear your thoughts.

Words by Cian Funge.

Clay: The Contemporary Botany Company, 2021



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