Brewing a Greener Cup: Environmental Footprints of Coffee Processing

Question: What are the environmental considerations of different coffee processing methods?

The journey from cherry to cup involves a variety of processing methods, each with its own set of environmental considerations. These methods not only shape the final flavor profile of the coffee but also leave distinct ecological footprints that are increasingly under scrutiny as the global demand for coffee continues to rise [6].

The Spectrum of Processing: From Dry to Washed

The dry (natural) processing method, one of the oldest techniques, involves drying the entire coffee cherry in the sun. This method generally requires less water compared to other processes, making it attractive in regions where water is scarce. However, it can lead to higher risks of spoilage and requires careful management of drying conditions to ensure quality and prevent microbial contamination. Conversely, the washed (wet) process involves pulping the cherries to remove the fruit pulp, fermenting them to break down the mucilage, and then washing away the remaining sticky layer [6]. This method typically uses significant amounts of water, raising concerns about water consumption and wastewater management. The fermentation step itself can also be a point of environmental interest, with studies showing that aerobic and anaerobic treatments can positively influence parameters like pH and acidity, contrasting with inhibitory effects observed in CO₂ treatments [2]. This suggests that controlled fermentation can be optimized to mitigate negative impacts and even enhance coffee quality.

Beyond the Bean: Co-products and Waste Valorization

Coffee processing generates substantial amounts of by-products, such as coffee pulp and silverskin, which have historically been considered waste. However, research is increasingly focusing on the valorization of these materials into valuable co-products [3, 6]. For instance, coffee pulp has been used to create wines, contributing unique flavor notes like honey, spice, fruit, and smoke, as well as more specific aromatic compounds [5]. Silverskin, a thin layer removed during roasting, exhibits significantly lower water activity (0.18-0.28) compared to cascara (0.39-0.64), indicating differences in their stability and potential applications [3]. Furthermore, spent coffee grounds (SCG) are being explored as a source for compounds like chlorogenic acid, a valuable antioxidant [7], and for the production of biopolymers and biocatalysts [7]. This shift towards valorization not only reduces waste but also creates new revenue streams and can offset some of the environmental burdens associated with coffee production.

Processing Parameters and Their Ecological Implications

Specific parameters within processing methods also carry environmental weight. For example, the washing process, which often involves pulping, fermentation, and washing, can lead to a lively tartness and aromatic notes in the coffee [6]. However, the efficiency of water usage and the treatment of wastewater are critical environmental considerations. Different fermentation protocols, whether aerobic or anaerobic, can impact pH and acidity [2]. Studies on coffee pulp wines show that fermentation can influence various flavor compounds [5]. Moreover, the choice of botanical material also plays a role; for instance, Coffea canephora co-products tend to have higher pH values (5.90-5.97) compared to Coffea arabica (4.22-4.something), which could influence wastewater characteristics [3]. Understanding these nuances allows for more sustainable choices in processing.

In conclusion, the environmental impact of coffee processing is multifaceted, spanning water usage, waste generation, and the potential for resource recovery. While traditional methods like the washed process present challenges in water consumption, innovative approaches to co-product valorization and optimized fermentation techniques offer promising avenues for a more sustainable coffee industry. Continuing research into these areas is vital for ensuring that our beloved cup of coffee can be enjoyed with a lighter ecological conscience.

References

[1] — Ernesto Illy, Luciano Navarini — Neglected Food Bubbles: The Espresso Coffee Foam. — 2011-Sep — https://pubmed.ncbi.nlm.nih.gov/21892345/ [2] — Gustavo Galarza, Jorge G Figueroa — Volatile Compound Characterization of Coffee ( — 2022-Mar-21 — https://pubmed.ncbi.nlm.nih.gov/35335365/ [3] — Katarína Poláková, Alica Bobková, Alžbeta Demianová, Marek Bobko, Judita Lidiková, Lukáš Jurčaga, Ľubomír Belej, Andrea Mesárošová, Melina Korčok, Tomáš Tóth — Quality Attributes and Sensory Acceptance of Different Botanical Coffee Co-Products. — 2023-Jul-11 — https://pubmed.ncbi.nlm.nih.gov/37509767/ [4] — Rongsuo Hu, Fei Xu, Xiao Chen, Qinrui Kuang, Xingyuan Xiao, Wenjiang Dong — The Growing Altitude Influences the Flavor Precursors, Sensory Characteristics and Cupping Quality of the Pu’er Coffee Bean. — 2024-Nov-28 — https://pubmed.ncbi.nlm.nih.gov/39682914/ [5] — Rongsuo Hu, Fei Xu, Liyan Zhao, Wenjiang Dong, Xingyuan Xiao, Xiao Chen — Comparative Evaluation of Flavor and Sensory Quality of Coffee Pulp Wines. — 2024-Jun-27 — https://pubmed.ncbi.nlm.nih.gov/38999011/ [6] — Shawn Gouws, Michael Muller — Valorization of products from grounded-coffee beans. — 2021-Oct-14 — https://pubmed.ncbi.nlm.nih.gov/34650157/ [7] — Krystyna Pyrzynska — Spent Coffee Grounds as a Source of Chlorogenic Acid. — 2025-Jan-30 — https://pubmed.ncbi.nlm.nih.gov/39942717/