SINGLING out coffee capsules or pods as ecologically detrimental is overly simplistic. According to a comparative analysis by Canadian researchers, we need to take into account all the manufacturing and processing steps involved in the preparation of a small-sized coffee, served black, in order to judge what method and format has the least impact on the planet when it comes to its carbon footprint in terms of greenhouse gas emissions. And you may be surprised that their results found soluble coffee to be the best solution.

Single-use materials, aluminum that can only be recycled if collected effectively and the coffee is separated from the packaging -- for years coffee capsules have been criticized for their heavy ecological footprint. Brands are trying to improve the reputation of their capsule products, which remain popular in Europe and North America, with, for instance, 40 percent of households in the US owning a coffee maker that uses pods.

While Nespresso attempts to restore its image by highlighting collection points that enable the aluminum in its pods to be recycled and used in bicycles or cans, as well as other initiatives, some other brands, such as Café Royal, prefer to reinvent the coffee capsule by creating a ball of compressed coffee free from packaging and fully compostable.

But coffee capsules are often characterized as the worst culprit in environmental terms but the situation is more complex when comparing the environmental impact of various methods of coffee preparation.

In a large study that the authors outline in The Conversation, researchers from the University of Quebec at Chicoutimi in Canada have gathered all the scientific data for all stages of coffee production, from manufacturing to consumption, from bean production, roasting and transportation to packaging and energy use in the heating process in order to disentangle the true from the false.

Filter coffee comes with the highest environmental cost

Their findings reveal that while coffee in capsule form can contribute to piling up in landfills if these pods aren't recycled, it's not the preparation method with the highest carbon footprint in terms of greenhouse gas emissions. Filter coffee actually has a greater impact on the planet.

In fact, a key factor is the amount of coffee used, simply because the production phase of the beans is the aspect of the chain responsible for emitting the most greenhouse gases. According to these researchers, it represents 40 to 80% of total emissions, due to the massive use of pesticides, fertilizers and the important need for irrigation systems in expansive modern coffee plantations.

In other words, if you need to use a lot of coffee for a preparation method, it adds to the carbon footprint.

This is notably the case for filter coffee, which uses 25 grams for a 280 ml cup, compared to 14 grams with the capsule method. The carbon footprint of the capsule method is further reduced if consumers use reusable capsules, or return the pods to the collection points.

And that's not all! The use of capsules also allows for an optimization of the amount of water used. However, this only works if you don't up your coffee consumption due to the ease of capsules.

In addition to the amount of coffee and water employed, it is also necessary to analyze the energy used in the process of brewing or heating to get a fair comparison.

The power consumption of a coffee maker is higher than that of a kettle, which reinforces the finding that soluble coffee is the greenest solution. Not only does instant coffee preparation require a smaller amount of coffee, particularly if a larger package is used, there is also no end-of-life waste to deal with, the researchers point out.