Coffee Waste: Where Does it Come From, Where Does it Go?

Another thing you probably never think about while drinking your cup-o-joe (I hate that term), is all of the coffee byproducts and waste that gets created during processing. These organic waste products can have great environmental impact in some coffee producing regions. Let’s look at the typical waste products created by processing, and where they typically end up. Then we’ll take a look at what practices Cuatro M use to decrease environmental impact, and increase sustainability.


We can’t get to the byproducts before talking about the number one most important resource in processing coffee: WATER. We all know water is becoming an ever-increasingly scarce resource all across the world, and in growing regions were very little water is to be found is were you’ll find coffees being processed in the natural (traditional) dry method. Remember from my  earlier blog post , this method is where you dry the cherry directly on the beans, without pulping it first. The problem is natural coffees only make up a small percentage of coffee produced in the world. The majority is processed using water.

Where Does it Come From and What Role Does it Play?

Growing coffee, as with most agricultural products, relies heavily on rainfall. Luckily in most of the best coffee producing regions there is a naturally occurring, and somewhat predictable, wet season. It is this precipitation that feeds the coffee trees, allowing them to blossom, and produce fruit. Just as important as the wet season, is the dry season. It is during this period of time when coffee is typically processed, since there is more sun and heat available to properly dry the coffees. Now you may be asking, if coffees are processed during the dry season, where do they get the water? If you’re super duper lucky, you may have a well located on your property, but this usually isn’t the case. Most mills get their water trucked in from surrounding areas. That water may be coming from a river (though rivers are getting increasingly polluted), a lake, or most likely a well.

There are two major functions of water during processing: de-pulping and washing. The depulper machine uses water to break up and flush away the pulp from the seeds, while mechanical washers and traditional fermentation tanks use water to wash or ferment mucilage off the seeds. Trucking in water can be expensive, and there’s not always enough to go around. In countries like El Salvador, where most coffee is traditionally fully washed (fermentation tanks), there is a growing trend away from fully washed methods to new mechanically washed processing (which uses less water).

So What is Cuatro M Doing to Reduce the Amount of Water They Consume?

  1. They no longer use traditional wet fermentation methods, except for small custom orders. Instead, most of the coffee they process is washed by state-of-the-art mechanical washers, which use a fraction of the water used in fermentation tanks.
  2. 60% of the water they use, comes from rain collection tanks on their property. The rest gets trucked in from the city.
  3. Over the past 6 years, Cuarto M has continually increased it’s “natural” production. This year, 30% of what they produce will be natural processed coffees.
  4. Emilio Lopez, the owner of Cuatro M, is currently running trial experiments in processing coffee using enzymes similarly used in wine production. If this method is successful, he will be using a only a fraction of the water he currently uses with the machine washers. Not only that, but the end result should be cleaner product.

*On a side note: it should be said that water quality has a large impact on coffee quality. The cleaner, the water the cleaner the coffee. This is why Cuatro M filters all of the water they use for processing. In addition to filters, Emilio recently installed ultraviolet lights inside the depulper, to further sterilize the water.

Water Collection Tank #1

Water Collection Tank #2

The Byproducts At The Plantation

Let’s start at the plantation level, were the biggest environmental impact is made. The bigest problem in  agriculture is eutrophication, and coffee plantations are no exception. Eutrophication is what happens when bodies of water become over-saturated with organic nutrients (such as nitrogen and phosphorus found in most fertilizers). These nutrients, while healthy for plants, are hazardous to watershed ecosystems when they build up too quickly. Since these nutrients are food for plant life, organisms such as algae and plankton start to grow at an unsustainable rate. These organisms need lots of oxygen to live, so they end up suffocating out all the other living creatures in the watershed. This type of oxygen starvation is called hypoxia, and it eventually creates an uninhabitable environment.

How Do Topeca’s Farms Stack Up?

Luckily for Topeca’s farms, eutrophication in not a big problem. Even though we use fertilizers on our trees, there exist no natural watersheds in any of the surrounding areas to the farm. No streams, no rivers, no lakes. That means no fertilizers running off into watershed systems. Instead they are only being absorbed through the soil, which will filter out much of the added nutrients before reaching well sources. Actually, much of El Salvador benefits from this fact. The biggest impact on rivers in El Salvador is not agriculture but lack of regulation, and the increase in poor community development along them. The rivers end up becoming landfills and sewage receptacles. (Not a good place to get your water for de-pulping)

At The Mill

There are three main waste products at the mill; Coffee PulpMucilage Water, and Parchment

Coffee Pulp

This is the product you end up with after you’ve de-pulped the coffee: the skin of the cherry. Where does all of it go you ask? Well, many mills sell it off as compost for fertilizers and mulches. Some dump it and let it pollute ecosystems. A growing trend in the coffee culture is using dried pulp to brew a coffee tea: called Cascara. Emilio disagrees with this last usage. He feels since there is no regulation in the processing of cascara, it could potentially be a hazardous product to people’s health. Pulp is by no means a clean product; it’s full of bacteria. Emilio fears that someone is going to get sick very soon from drinking this tea. But each to their own.

What Does Quatro M Do With Their Pulp?

They recycle. All of the pulp created by each harvest gets used as mulch for new trees. No one is drinking it…yet.

Mucilage Water

This is the water left over after de-pulping and washing coffee at the wet mill. Some people reuse it for processing, but that is a most  unsavory  method, as it is super dirty at that point. So most people just get rid of it. Here again we run into the problem of  eutrophication , since this water is dense with organic solids and nutrients. Before regulation, a lot of mills in El Salvador were dumping this water into lakes. This is not the case today, as lakes are protected by the government.

So What Does Quatro M Do With Their Waste Water?

First thing is first, they filter out solid matter and sediments with a sieve. Then the water gets transported to one of two mucilage pits. When the water soaks into the soil at these pits, they can then use the soil as a natural fertilizer. Pretty cool huh?


Remember from my earlier post that parchment is the layer between the mucilage and the seed. Once dried, the parchment is then hulled from the seeds (beans) at the dry mill. The parchment accounts for about a fifth of the coffees weight when it comes off the patio. After hulling the coffees, you are left with a lot of parchment. So what do you do with it? Some mills sell theirs to chicken farms, where it is used as bedding for the chicken pens. And then sometimes the mills will buy it back, once it has been efficiently pooped on, and use it as fertilizer.

How About Quatro M?

Would you be surprised if I told you they repurpose it? That’s right all of the  parchment created gets used as fuel for their mechanical dryers. That’s a pretty sustainable system if you ask me.Don’t let the picture I’ve painted above fool you into thinking this is how all coffee producers take care of their waste. Cuatro M is a best case scenario (and getting better all the time).

Many producing regions, especially those in less developed places such as Africa or Indonesia, still face big problems when it comes to environmental responsibility. My hope is that with increasing coffee prices, the growing shift from commercial to specialty markets, and consumer/producer education, more steps will be taken in instituting sustainable practices in coffee around the world.

*For more reading about recent water quality research in coffee producing regions of Ethiopia, read Lili Kubota’s article in The Specialty Coffee Chronicle HERE.

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