Coffee processing: Which method is the most sustainable?

TJ Grant
May 20, 2021
coffee processing methods

Washed, natural, honey – there are various ways of processing coffee, each one with the ability to impart distinct flavour characteristics on the beans. Used to remove mucilage and pulp from the cherry in preparation for roasting, processing is a crucial stage in the journey of a coffee from seed to cup.

However, with calls for a more sustainable coffee supply chain growing, the spotlight has increasingly fallen on processing and the impact that each method has on the environment. As such, many farmers have moved away from unsustainable practices and adopted methods more conducive to the long-term future of coffee production.

But which method is the most sustainable? And why does it matter to specialty roasters? To find out, I spoke with three-time Guatemala Cup Tasters Champion and Head of Quality Control at Bella Vista Coffee, Dulce Barrera.

Read next: Coffee Processing: What Is Carbonic Maceration?

washed coffee processing

How can processing be unsustainable?

Coffee processing is a technique that’s been in use among coffee growers for centuries. Put simply, it’s the removal of layers that surround the coffee bean (or seed) typically by either washing or drying or a combination of the two.

The oldest technique is known as natural (or dry) processing. In this method, the coffee cherries are set out to dry with the fruit and skin intact, before being separated after a period of weeks or months. Coffees processed in this way tend to be full bodied with bold flavours and low acidity.

However, the inconsistent results of natural processing has caused its popularity in some coffee-producing countries to fall. In its place has emerged washed processing, a method in which the cherries are sorted in a flotation tank, before having their pulp removed and being left to ferment in water for 18-36 hours.

Compared to natural processed coffee, which often has round, winey fruit notes, washed coffee tends to produce clean, consistent coffees with high acidity and clarity of flavour. For that reason, they tend to be favoured by many specialty coffee roasters. 

However, the water-intensive process has led to question marks over its sustainability, particularly in countries where water is in relatively short supply. Washed coffee typically uses around 10 litres of fresh water per kilogram of dry parchment on coffee seeds, whereas natural processed coffees use less than one.

Dulce Barrera is Head of QC at Bellavista Coffee in Guatemala and was a finalist at the 2019 World Cup Tasters Championship. She tells me that the effects of climate change have made washed processing a less attractive prospect in some coffee-growing areas.

“Washed coffee processing becomes unsustainable when there is limited access to water on the farm,” she says. “While this method helps to reduce coffee moisture content and enable farmers to create deeply complex flavour profiles, certain coffee-growing regions are experiencing droughts due to the effects of climate change, such as Ethiopia.”

There can also be extensive pollution in local water sources when wastewater is not treated correctly. The leftover water after processing often contains high levels of organic matter, such as sacred parchment, and low oxygen levels, which can kill wildlife and create non-potable water. When this is the case, washed processing tends to be viewed as unsustainable.

“All waste water from any kind of processing must be separately contained until its pH level is naturally balanced,” Dulce explains. “If the waste water is used before pH neutralisation, it could disrupt the natural balance of soil pH, further disrupting the farm’s ecosystem.”

sustainable coffee processing

Challenges to economic sustainability

The high volumes of water and incorrect disposal of it to produce washed coffees are undoubtedly environmental concerns. However, sustainability isn’t limited to the environment; Dulce points out that for coffee to be considered wholly sustainable, the processing method also has to work financially for the farmers involved.

“It’s important to remember that sustainability has three pillars: environmental, social, and economic,” she says. “All three must be met to achieve full sustainability.”

This is something that has particularly come up with regards to experimental processing techniques. Rising interest in exclusive and rare coffees in the specialty sector have driven many producers to experiment with newly emerging, highly technical processing methods, such as carbonic maceration and anaerobic fermentation. 

Due to a combination of limited supply and clever marketing, these coffees tend to command significantly higher prices on the market than regular washed or natural processed coffees. Experimental processing like anaerobic fermentation can increase coffee prices up to US $54.10 per pound. But while this may seem like an attractive prospect for producers, it lacks the long-term financial sustainability of traditional processed coffees.

“The more experimental processing – such as carbonic maceration – doesn’t always yield high quality results for farmers,” Dulce tells me. “If they don’t have the skills or knowledge to carry out controlled and well-designed experimental processing, the coffee often tastes over-fermented and highly unpleasant.”

processed beans

Steps to improve sustainability

As consumers demand greater sustainability across all stages of the coffee supply chain, many producers have taken tangible steps to reduce the environmental impact of processing and improve their financial stability. 

One of the most notable changes has involved the repurposing of coffee pulp. Dulce tells me that instead of discarding the pulp, some farmers have started selling it to be used as cascara, a popular coffee cherry tea.

“Farmers have devised innovative ways of making use of waste from coffee processing,” she says. “As well as cascara, discarded coffee pulp can be used as fertiliser. But first, farmers must have suitable infrastructure in place to ensure that the composting of coffee pulp is carried out sustainably and efficiently.”

Sustainably managing wastewater from washed processing can be also achieved by filtering various organic matter or treating with probiotics to increase oxygen levels, allowing it to be added back to local water systems. 

“If farmers take great care in their work, processing can be made sustainable for both the environment and the people involved,” Dulce tells me. “For example, abiding by local, regional, or national environmental guidelines can inform farmers of the importance of well-maintained water treatment and waste management.”

sustainable packaging

Processing is a crucial stage in the journey of a coffee from seed to cup. It’s responsible for imparting a number of characteristics, as well as for transforming it into a green bean ready for roasting. While some processing methods are more sustainable than others, many producers are taking measures to make their practices conducive to the long-term future of the coffee industry.

At MTPak Coffee, we can help to highlight the unique qualities of sustainable coffee processing with our range of compostable, biodegradable and recyclable packaging, that can be fully customised to make your coffees stand out.

For more information on our sustainable coffee packaging, contact our team here.

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