River Water in Jimma Officially Effected by Coffee Processing – SCAA
By Emma Bladyka, Coffee Science Manager, SCAA
A new study, published in theJournal ofEnvironmental Monitoring and Assessment, has investigated the specific environmental impact of coffee waste on river water in the Jimma Zone of Ethiopia. This research was undertaken by collaborators from Ethiopian, US and Belgium Universities, as well as the local Jimma Agricultural Research Center. The article was first published online on December 9, 2011, and can be found at the journal website.
Most of us are probably aware that coffee processing can use a lot of water and impact the chemistry of that water, but this has not been quantified extensively in many growing regions. It is especially important to understand this coffee-related pollution as we progress further down the rabbit hole of climate change and dwindling natural resources.
Interesting study! Considering that so many of us in the specialty coffee industry are also concerned about environmental responsibility, I assume this to be worth paying attention to for any buyers of Ethiopian coffee, especially from the Jimma zone. Solid wastes from processing (I assume this is primarily from the wet process mills) are seasonal (obviously), and scientists actually evaluated river water before, during, and after wastes were dumped to see how the normal river ecosystem is effected by coffee. The results are both better and worse that what one might expect.
In this study, the authors found significant reductions in water quality downstream from coffee processing plants during the wet season. During the wet season, they saw a large increase in organic loads, nutrients, and solids, which resulted in dissolved oxygen levels to as little as 0.1 mg/L water. They also found that during the processing peak that the average pH of river waters was lowered from 7 to 6.2. This combination of changes led to a decrease in diversity of macroinvertebrates.
During the dry season, the scientists found that the organic load, dissolved oxygen, solids, and pH had recovered to mostly normal levels. They found that the overall macroinvertebrate diversity was restored during this time period, but that the most sensitive taxa remained at low percentages, indicating a longer-term impact on the ecosystem. Interestingly, since the dissolved oxygen was reduced so drastically, scientists found that the water pollution by nitrogen was unable to recover during the dry season. This is because some oxygen is necessary during the nitrogen cycle in order to transform it to its volatile form and expel it from the river water. With this information, they determined that oxygen levels, organic load, and nitrate were all causal for the shift in invertebrate diversity. The authors considered this a very serious finding and worried that without fast action many of these rivers would pose a risk to not only ecosystem but human health.
I HIGHLY recommend reading the entire article, as it goes into more detail than I feel comfortable re-pasting here. It does take into consideration the idea of filtering the waste water before returning it to the river, as well as composting and fertilizing practices and possibilities with coffee waste. It also mentions that there are farms that do this, however, it does not mention any research into their overall effectiveness in preventing river water contamination. I suspect, however, that it is quite good, considering that the bulk of the problem appears to be solids. It appears that anything preventing solids from ending up in the river is a good thing.