Wet processing began when Arabica coffee started being planted in areas that were hotter or more humid than the highlands of Ethiopia. Recently harvested coffee cherries quickly fermented in these new areas, which had adverse impacts on cup quality. The solution at the time was to remove the sugar-rich, fermentation-prone pulp and mucilage in what was to be called ‘wet milling,’ thus giving birth to washed coffee. It was found that coffee processed using the washed method differed in taste from the more traditional natural process: body and sweetness is stronger in natural coffees as opposed to the aroma and acidity in washed coffees.
Up until very recently, the wet milling of coffee was a very water-intensive process, and there was little concern for water consumption and contamination. The conventional technology at the time and, which is still utilised in many areas today, used water in flotation to separate over-ripe and dry cherries from the ripe ones, and in pulping, to remove the pulp and in mucilage removal and the transport of coffee and by-products (e.g., pulp). The growing concern for the environment in recent times has led to questioning the use and contamination of so much water – often 10,000 m³ per ton of green coffee – in the wet processing method. The pollution load in the wastewater from the wet milling of coffee can be 30 to 40 times greater than the one found in urban sewage.
The problem we face when it comes to changing the current climate is that there is a lesser degree of control over cup profile and flavour when it comes to natural coffee. Whilst it is considerably better for the local ecology, are farmers willing to sacrifice quality (and in turn income) in order to preserve the environment? This question is being asked in developing parts of the coffee producing world and steps are being taken to ensure sustainability is at the forefront of the producers thinking and that cup quality remains high.
Whilst the flavour profile of wet processed coffee is very desirable in the current market, do we really know enough about the impacts this can have at source and what are we doing to combat this?
Kubota, L. (2013, July 8). The use of water in processing: Treatment, conservation, and impacts on quality. Retrieved from www.scaa.org, http://www.scaa.org/chronicle/2013/07/08/the-use-of-water-in-processing-treatment-conservation-and-impacts-on-quality/