Coffee Wastage from Grinder Adjustments: Causes, Impacts and Solutions

Dialling in a coffee grinder is a necessary evil for your baristas, who constantly monitor grind size and make minute adjustments whenever their extraction time falls out side of their target recipe. When extraction times are running high, grinding coarser can help speed things up and improve the flavour whereas fast shots of espresso that taste weak can be fixed by grinding finer. For a more in depth guide on this check out -> How to Slow Down or Speed Up an Espresso with Grind Size.

Unfortunately, the nature of the dialling in process and the design of many commercial coffee grinders can lead to a small amount of coffee being wasted every time the grinder is adjusted. In this article, we’re going to explain why coffee wastage happens, how much this can affect your bottom line through wasted spend on coffee, on what you can do to limit this source of wastage in your coffee shops.

Why Dialling in Grind Size can Waste Coffee

No cafe is going to be completely zero-waste when it comes to their coffee. Not at the time of writing, at least. Avoiding wastage is difficult, but being mindful of how much coffee and milk is being thrown away can be incredibly insightful and save you a lot of money on wasted resources in the long run. So why is avoiding coffee wastage so difficult?

Most Commercial Grinders Retain Coffee (Retention)

Commercial coffee grinders, by design, have typically suffered with a level of retention, meaning a small amount of coffee is retained inside the grinding chamber between doses. During regular service this is not a serious issue – bean doses are fed regularly enough through the chamber so that the small amount of retention has little impact on the flavour or freshness of the coffee.

Issues can arise, however, if the current coffee you are using has fallen out of it’s target extraction time calling for an adjustment to the grind size. Commercial grinders can retain anywhere from 5-10g of coffee inside the chamber at any one time, and this causes a problem when you want to change grind size. That small amount of retained coffee will not all come out of the grinder at the new grind size, so your first should could contain a wide sweep of particle sizes.

Purging Grounds between Adjustments

In order to combat this, baristas are told to purge a small amount of coffee manually through the grinder to clear out any of the previous grind size. This is clearly a wasteful practice, though grinder manufacturers are starting to catch on and producing near zero-retention grinders like the Sanremo X-One which we have reviewed here.

Discarding Coffee for Cleaning

Retention is also a problem any time you want to swap beans, or if you want to remove beans from the chamber for cleaning. With most grind on demand espresso grinders, you’ll have to purge any retained coffee grinds and beans through the grinder before making any change to the coffee or before removing the hopper for cleaning. This can again be wasteful, and is something you can not really avoid with these styles of grinders.

Making the Wrong Adjustment

Dialling in a grinder is inherently a trial-and-error process, whereby a barista can often make too large of an adjustment to their grind before going the other way and finding the sweet spot for their extraction. It’s fairly typical for an experienced barista to use up 2 to 5 shots of coffee dialling in, tasting and fine tuning their grind size and recipe before they are happy with the flavour. Inexperienced baristas, on the other hand, may go through even more than this, especially if they aren’t familiar with the process and aren’t keeping the dose, tamping and brewing consistent.

Though these issues can lead to wasted coffee, the amounts seem small on a day-to-day basis. Next, let’s get into how much money businesses could be wasting on seemingly small amounts of day-to-day wastage.

Potential Financial Impact of Wasted Coffee Grounds

Per kilo of coffee beans, assuming an 18 gram dose for your double espressos, you have enough beans for 55 coffee drinks. Being conservative with levels of wastage, we typically tell customers that each kilo of coffee equates to about 50 drinks. So, with our best guess, coffee shops can expect around 10% of their coffee to go to waste. That’s not just from wasted dialling-in grinds, but also coffee going stale, mess around the ground, espressos laying around for too long and going down the drain, and the occasional staff coffee. Based on this prediction, and taking data from our previous blog post about the typical spend on beans for coffee outlets, we can state that cafès could be losing between £300 to £1,500 per year on wasted coffee depending on their style of grinding, level of training and volume of coffee drinks being served.

What Can Be Done?

Though the problem is widespread, wasting coffee during the dialling in process is not inherent to the craft. The problems lie in the effieincy of the barista, and the design of the machinery. To limit the amount of coffee you waste on a daily basis, there are a number of things you could implement in your coffee shop.

Zero Retention Grinders

The largest cause of coffee wasteage from dialling the grinder is needing to purge a small amount through the burr chamber between adjustments. This can be mitigated completely by investing in a grinder that holds a negligible amount of grounds between doses. These are known as ‘zero retention’ grinders. They have become incredibly popular in the home barista market as users want to switch between coffees and grind sizes on a dially basis to use different brew methods at home, at to limit the amount of wastage on their hard-earned beans. The technology is slowly funnelling into the commercial space, and we’re now seeing a growing list of commercial zero retention grinders like the Sanremo X-One which hold no coffee inside the burr chamber, and therefore waste no grounds during the dialling in process.

Automatic machines with Self-Dialling Capabilities

Investing in modern grinders is a great idea to limit the coffee wastage during dialling in, but it does not remove the scope for human error. Whilst expensive, there are a growing list of coffee machines that, through technological innovation, are now able to fully dial in the coffee and take ownership of the recipe and brew parameters on behalf of the barista. This means grind size can constantly be monitored and tweaked by the machine, always making the correct adjustments when necessary and thereby reducing wasteage through human error.

Just One Coffee Type Per Grinder

Alongside keeping the grind size fine tuned during day-to-day, another main source of wasteage comes from swapping out the coffee for something different. This typically requires purging the remainder of the previous coffee through the grinder, optionally removing the hopper and cleaning out the burrs, then adding the new coffee in and purging a couple of shots to ensure the right dosage is coming through, then dialling in the grind size. This can be a wasteful process and is required every time you swap coffees. To reduce wasteage, keep each grinder dedicated to just one type of coffee. If you want to serve decaf or a single origin coffee, we always recommend running these through their own dedicated grinder. Optionally, you could also invest in a multipurpose grinder like an EK43 that can be used for all of your filter coffees, single origin espresso and decaf coffees alongside your main espresso grinder. If another grinder is out of your budget, consider buying small amounts of pre-ground decaf and filter coffees from your roaster to reduce wasteage from the grinding process.

Helping your Baristas be More Efficient

Investing in additional modern grinders or industry leading automatic machines can be a large upfront cost, but another way of improving your setup to be less wasteful when it comes to coffee is to empower your baristas with experience and knowledge. Knowing exactly what kind of adjustment to make to your machinery, when and why, can help your baristas become more efficient in speed and productivity, and making the correct adjustments first time will massively reduce wasteage in the long run.

Empowering your baristas can take many forms, starting as simple as watching a few youtube videos to learn best practices on grind size and other areas of potential wastage such as milk steaming. A great place to start is a video we put together ourselves, a 3 minute explainer on grind size. You can check that out here -> Grind Size. Unfortunately, getting your baristas to sit down and watch a few training resources can be easier said then done, and the best solution for your staff is to enlist the help of a barista trainer who can visit your site and help your baristas on shift with techniques and best practices. If you’re interested in working with a coffee supplier that helps you get the most out of your coffee through continued support and training, learn more about our barista training here -> SCA Barista Training.