What Is Sumatran Coffee?

Sumatran coffees have been gaining popularity around the world. But what is it about them that makes them so unique?

They are known for their bold, earthy flavors, full body, and surprisingly low acidity, which is shaped at least in part by their distinctive processing methods.

Grab a mug and explore the world of Sumatran coffees with us, and learn where they’re grown, what wet hulling is, what flavors you can expect, how to brew a fantastic cup, and how our long-term partnership with the KGLA cooperative helps protect Sumatran rainforests. 

What Makes Sumatran Coffee Different?

Some people think coffee is coffee no matter where it comes from, but that’s not at all the case. Every coffee is distinct because of the variety being grown, how it’s cultivated, and where it grows. Terroir, or the taste of place, is the unique combination of environmental conditions like elevation, climate, and soils that also affect the flavors in your mug.

Processing methods also play a crucial role. What’s so unique about Sumatra is the tropical climate with high humidity, heavy rain, and frequent cloud cover that slows the drying process.

As a result, the natural sun-dried method is especially challenging, and even the washed process still requires 1-2 weeks of dry weather. Sumatra seldom sees dry weather that long. In the mountains where coffee grows, the annual rainfall can reach 6,100mm (240.2”). To put that in perspective, Hawaii, the USA’s wettest state, receives an average annual rainfall of just 1,618mm (63.7”).

This is why Sumatran coffees are typically processed using a method unique to Indonesia and especially Sumatra, called wet-hulling. 

What Is Wet-Hulling (Giling Basah)?

Wet-hulling, sometimes called the Sumatra process or giling basah, starts out similar to the more common washed method but finishes with some significant differences.

At first, just like with the washed method, the freshly picked coffee cherries are mechanically depulped to remove the fruit from the seeds, which we commonly call coffee “beans.”

The beans are then fermented while still wet in their parchment layer (the seed coat), which may be done in various ways in Sumatra but generally involves submerging them in water for a few days. Fermentation helps remove any mucilage that remains on the seeds after depulping. After fermentation, the beans are washed to remove the mucilage.

Then the method diverges from the fully washed method to its Sumatran specialty—the wet hull method. It’s called “wet-hulling” because unlike other processing methods, the parchment layer is removed from the beans while they are still wet. Removing that protective layer lets the beans inside dry out much more quickly, eliminating the need for weeks of dry weather that is so hard to find in Sumatra.

Once hulled, the beans (now free of their protective parchment layer) are spread out to dry in the open air, usually on raised beds or patios. Because the parchment is already gone, this final drying stage takes just a day or two instead of the one to two weeks required by fully washed processing, which is what makes wet-hulling so well-suited to Sumatra's unpredictable, rain-heavy climate. 

Where Is Sumatran Coffee Grown?

Dutch colonists brought coffee cultivation to Indonesia generations before it reached the Aceh highlands around Lake Tawar until the early 1900s. Today, farmers still widely grow mostly Arabica beans in northern Sumatra in the Aceh (Takengon, Bener Mariah) and Lake Toba regions (Lintong Nihuta, Dairi-Sidikalang, Siborongborong, Dolok Sanggul, and Seribu Dolok).

Robusta is also grown on the island, primarily at lower elevations in the south, but Dean's Beans' Sumatran coffees are all Arabica.

The coffee-growing regions of northern Sumatra are at high elevation in rugged volcanic terrains with rich, permeable, volcanic soils, which are well-suited for growing coffee. With the island sitting directly on the equator, it also offers mild temperatures and abundant rain.

Our certified organic, Fair Trade, shade-grown Sumatran coffees are grown in the Takengon Highlands of Aceh Province, North Sumatra, where lush tropical forest cover and the rich volcanic soils produce delicious coffees with hints of dark chocolate, spice, and herbal depth with full body and low acidity.

Our Partnership With KGLA in Sumatra 

Over the years we have partnered with different Sumatran cooperatives, including KKGO, Ketiara, and more recently the Gayo Lauser Antara cooperative (KGLA). KGLA is a relatively small cooperative of over 700 farmers who grow coffee in rich volcanic soils in the shade of the lush forest canopies of the Aceh region. As a worker-owned cooperative ourselves, we know what it takes to build something that lasts.

Our relationship with KGLA is a true partnership rooted in pride and care for growing quality coffee, sustainable farming practices, and local well-being. We maintain this relationship by traveling to meet the farmers regularly, and by acting on what we hear – like helping fund the nursery program below.

Through our People-Centered Development model, local leaders direct and lead the projects we assist with. This approach puts decision-making in the hands of the communities, supporting long-term, locally led sustainable development.

We have contributed to several farmer-led projects, including supplying laptops, printers, and software to improve traceability, which will help KGLA enhance their infrastructure and continue achieving certifications in organic agriculture and Fair Trade.

Our partners at KGLA have created their own nurseries where they cultivate shade trees and climate-resilient coffee varieties, helping protect farms and biodiversity. They also participate in reforestation efforts, and their organic weed control is a great example of that same resourcefulness: KGLA's farmers didn't wait for someone else to solve their weed problem—they came up with their own solution.

Instead of turning to herbicides, they clear weeds by hand with weed whackers, then carry the cuttings back to the village to feed their goats. The manure the goats produce is used to fertilize the coffee plants, keeping the whole cycle organic, from field to fertilizer. It's the kind of practical, farmer-led thinking that defines KGLA's approach, and it's exactly why we're proud to call them partners.

Between the shade-grown canopy that shelters their coffee, the nurseries growing climate-resilient trees, and their reforestation and organic weed control efforts, KGLA's farmers are actively protecting the same rainforests their coffee depends on.

What Does Sumatran Coffee Taste Like?

The flavor of Sumatran coffees varies with the combination of terroir, coffee variety, and growing methods. Wet-hulling processing, distinctive to this region, adds another layer of complexity compared to other processing methods.

Wet hulling produces raw beans that are often more bluish-gray or brownish than the typical green or yellow-green we see in other coffees. Wet hulling also tends to mute the acidity and draw out more earthy, savory, or herbal flavors and a heavy body.

Our Sumatran coffees offer bold and earthy cups with notes of dark chocolate, spice, and herbal depth, with a full body and pleasant, low acidity. 

How to Brew Sumatran Coffee 

Brewing exceptional Sumatran coffee starts with a few key variables.

First, we recommend grinding freshly roasted whole beans for the freshest flavors and aromas in your cup. Then, if your water has any unpleasant tastes like chlorine, iron, or sulfur, try filtering it first to improve the flavor. 

Next, start with the recommended amount of ground coffee for your brew method—note that weighing instead of scooping will give you better consistency. After you’ve tested it, we encourage you to adjust your coffee-to-water ratio until you find the balance that best suits your tastes.

Finally, how you brew usually depends on the roast level. Although you can use any brew method for any roast, some methods are better at highlighting certain roasts.

For instance, if you enjoy a light or medium roast with subtle flavors from the origin, try a pour-over method with a paper filter. Using paper filters removes some of the natural oils, which allows the nuanced flavors of the origin to shine through.

Medium roasts like our certified organic, Fair Trade Moka Java – a smooth, syrupy blend of Sumatran and fruity fragrant Ethiopian coffees – also brew very well in the AeroPress, which is a versatile compact brew method that you can use for any roast. 

Or, if you prefer a classic dark roast like our certified organic, Fair Trade Sumatran French Roast, try using the French Press. Its immersion brewing and the lack of a paper filter leave more natural oils in your cup and produce robust flavors, a fuller body, and a creamier mouthfeel.

Frequently Asked Questions

Why Is Sumatra Coffee So Special?

Sumatran coffees are grown in lush, mountainous forests with rich volcanic soils and mild temperatures, which are well-suited for cultivating quality coffees. Since Sumatra lies on the equator, the abundant rain makes wet-hulling processing methods common, which produces unique earthy, herbal flavor notes with a full body and low acidity. 

Is Sumatran Coffee Arabica?

Most of the specialty coffees grown in Sumatra are Arabica, especially in the northern highlands where Dean’s Beans sources its coffee. Robusta is also grown on the island, mainly at lower elevations in the south, and is typically sold to commercial buyers for instant coffee and blends. It’s not something we source, though; our Robusta comes from India.

Discover Sumatran Coffee That's as Bold as the Rainforests It Comes From

Sumatran coffees are grown in the rich mountain forests on this tropical island. The result is a full-bodied coffee as bold as the rainforests it comes from, with unique flavor profiles hinting at earthy and herbal notes with dark chocolate and baking spices and low acidity.

Our certified organic, Fair Trade, shade-grown Sumatran coffees are grown with care by the KGLA cooperative, which focuses on reforestation and organic farming practices, helping preserve their native rainforests and biodiversity while bringing delicious flavors to our morning mug.