Zero waste: What is chaff & how can specialty roasters reuse it?

Jane Merchant
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June 16, 2021
coffee chaff byproduct

As concerns grow over the sustainability of the coffee supply chain, specialty roasters are increasingly looking for ways of limiting their impact on the environment and reducing the amount of waste produced during roasting.

An estimated two billion tonnes of coffee byproducts are produced every year and one of the largest contributors is chaff (or husk). Chaff is the dried skin surrounding coffee beans that falls off when exposed to high temperatures. Although most roasters have chaff collectors, the contents often end up being mixed in with general waste, which then goes to landfill where it breaks down.

However, a developing body of research into the reuse of chaff has produced some interesting results. Today, it can be reused for a range of purposes, from compost to the manufacture of car parts. Not only is this helping promote a circular economy, it’s also protecting the long-term future of coffee production.

Read next: How can specialty coffee roasters promote a circular economy?

coffee roasting chaff

How is chaff produced and what happens to it after roasting?

Chaff (also known as silverskins or husk) is the epidermis of coffee beans that falls off during roasting due to the application of heat. Light and fluffy in texture, chaff is usually collected in a bucket (called a chaff collector), while the rest collects on the inside of the roaster from where it must be cleaned to eliminate the risk of fire.

Because chaff does not taste pleasant when brewed, it must be thoroughly sifted from the coffee before it’s packaged. 

The amount of chaff produced by each bean depends on a number of factors, including the coffee variety and processing methods. Some medium-sized roasters produce more than 400 pounds a week, while global chains such as McDonald’s can produce in excess of 62 million pounds a year. In general, it’s estimated that for each tonne of coffee produced, half a tonne of coffee husk is generated.

Many roasters dispose of chaff along with general waste or burn it. Although it’s organic and biodegradable, when chaff breaks down in landfill it emits methane. Methane is a powerful greenhouse gas (GHG) thought to be 80 times more damaging to the environment than carbon dioxide over a 20-year period.

Therefore, it’s crucial that specialty roasters do everything they can to reduce the impact of coffee chaff by exploring ways of repurposing it.

ford motors chaff car parts

How can roasters repurpose and reuse it?

Coffee chaff has a number of properties that make it useful when repurposed for other products. 

Compost & fertiliser

The easiest and most practical way to reuse chaff is to repurpose it as compost or fertiliser. Chaff is organic, light, and airy, which means it mixes well with other compostable contents. 

It is also rich in nitrogen, an element that plants rely on to create their core components. Fast-growing vegetables in particular, such as tomatoes, benefit from the soil-enriching properties that chaff offers, while its ability to naturally repel pests does away with the need for additional pesticides.

Specialty roasters can easily sell or give away the chaff collected during a roast, either to customers or to garden centres. This is a cost-effective and efficient way of repurposing chaff.

Recent research from the Texas A&M Department of Soil and Crop Sciences suggests that chaff could potentially rival peat moss (a nonrenewable resource) as a root zone mix, too. Root zone mix is a product popularly used on turfs and landscapes.

Car parts

In 2019, Ford Motors and McDonald’s announced a partnership to reuse chaff collected from a McDonald’s roasted coffee supplier to make car parts, such as headlamp components.

A biomaterial technology company uses a patented process to combine the chaff with resins, plastics, and additives in a high-temperature, low-oxygen environment. This produces pellets that can be shaped into lightweight components that have better heat properties than plastic ones. Not only does this reuse chaff that might otherwise go to landfill, it also helps reduce the energy involved in producing brand new plastic products.

ice cream chaff

Food stuffs

While chaff left on roast coffee doesn’t taste good, it’s been repurposed into edible products by a number of roasters. For example, New Zealand coffee company Kōkako uses it as an ice cream topping, while instant coffee company Waka uses it to make cascara syrup.

While only a small number of roasters currently reuse chaff this way, it could all soon change. One study suggests that it may hold significant value as a health supplement.

Research carried out by the University of Illinois College of Agricultural, Consumer and Environmental Sciences suggests that two of chaff’s phenolic compounds (gallic and protocatechuic acid) could reduce glucose absorption and insulin sensitivity in type-2 diabetes sufferers. 

Fuel

The heating of homes and buildings consumes a significant amount of energy. However, chaff is a good alternative to nonrenewable fuel sources like wood and petrol. Rounton Coffee Roasters, for example, collect it and compact it into briquettes that can be used to fuel fires.

Because of its high calorie content it will burn for longer, producing less toxic fumes while it does so. It will also produce less ash and create a pleasant aroma while burning.

Some companies have experimented compacting chaff into pellets and using it to smoke foods or as smoker fuel for beekeepers.

For specialty roasters, repurposing chaff is an important part of working towards a circular economy and reducing the environmental impact of the coffee supply chain. What would otherwise go to landfill and emit methane gas can instead be put to use for a range of other products, from compost to car parts.

At MTPak Coffee, one of our central aims is to help specialty roasters operate more sustainably. That’s why we offer a selection of fully recyclable, biodegradable, and compostable coffee pouches that can be customised with recyclable components and low VOC water-based inks.

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

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