Ways to reduce coffee pollution: Common wastewater treatment methods

Wastewater generated coffee processing plants contain high amounts of organic matter and dark coloured pigments that are toxic to aquatic and human lives. While biological treatment types are typically used to treat wastewaters, non-biodegradables in coffee effluents may still hinder the water quality of treated water (Tomizawa et al., 2016). As such, researchers look into combining biological with physicochemical methods to improve the water quality derived from wastewater treatment (Mohamed, 2015; Blanco et al., 2014).

The most common biological method would be the anerobic/aerobic wastewater treatment. Both of which requires bacteria or other micro-organisms to breakdown the organic compound from the wastewater via biological oxidation to form sediments, which can then be removed (Mohamed, 2015). However, it is noted that the process is too time consuming, and requires the effluents to be of a consistent condition for the process to be efficient (Ijanu et al., 2020). Hence, scientists and engineers have explored the possibilities to improve wastewater treatment effectiveness via pairing up with physicochemical methods.

A common physicochemical method is the photon-Fenton process. Based on Dong et al. (2020), a photo-Fenton reaction is a kind of advanced oxidation process, which conventionally combines  Fe2+ ions with H2O2. It was found that this reaction generates a strongly oxiding radical species that can degrade organic pollutants into non-toxic materials, without the need for a harsh environment and special equipment. Notably, this reaction requires a low pH of 2.8 to reach maximum efficiency (O'dowd et al., 2020), making it a less desirable choice for wastewater treaters.

Above are common biological and physicochemical methods to treat coffee wastewater, and of course, the list of effective treatment methods are not limited to these. As each methods have its pros and cons, it is up to the wastewater treatment facility to decide which method best fit the situation they face (e.g. cost of operation, efficiency in removing pollutants).

Bean on a Journey: Turning over a new leaf?

With the enlightenment on the possible pollution that coffee wastewater can do to the environment in recent decades, there is a greater sense of urgency to mitigate the pollution. Hence, it is apt to introduce some wastewater treatment techniques that help reduce pollution derived from wet processing to conclude the Bean on a Journey series. Further discussions about the effectiveness of techniques will be discussed in the next series.

1. Physiochemical treatment

In recent years, physicochemical treatment has garnered popular votes from wastewater treaters, as it is efficient and effective in breaking down complex compounds in the wastewaters (Ijanu et al., 2020). Some examples of physicochemical treatment include:

- zero-valent iron treatment
- photo-fenton method
- ultraviolet radiation catalysis
- electro-oxidation

2. Biological treatment

Biological treatment has been widely practised, as it is effective in removing biological oxygen demand (BOD) in wastewaters (Ijanu et al., 2020), and cheaper to implement on a large scale (Muthukumar et al., 2021). Some examples of biological treatment methods include:

- expanded granular sludge bed bioreactor
- chemical coagulation and flocculation
- adsorption

 3. Ion-exchange 

While the ion-exchange technique is not foreign to the wastewater treatment industry, it does not seem to be a widely adopted technique to treat coffee effluent. Ijanu et al. (2020) and Campos et al. (2021) briefly mentioned the technique in relation to coffee effluent and recognised the method as cheap and environmentally friendly.

4. Membrane filtration

Membrane filtration is commonly used to complement the other methods mentioned above. As per its name, membrane filtration filters sediments and large bacteria from the wastewaters (Pamula, 2018). Following this train of thought, the membrane is rendered useless when faced with chemical compounds that need to be separated (Ijanu et al., 2020).

While there seem to be many options for wastewater treatment, many such techniques are still not frequently employed in coffee plants. To increase the uptake of these pollution reduction methods, instead of purely educating the types of techniques available, it would be wiser to recommend a method that is most desirable to their circumstance.

Bean on a Journey: Wet processing

Specialty grade arabica beans are typically produced via wet processing as it is said to produce a cleaner taste and brighter acidity, which improves the flavour profile of coffee. While wet processing increases the desirability factor of coffee in terms of taste, it certainly does not do the same for sustainability. In this instalment of Bean on a Journey, we explore how depulping, fermentation and washing of coffee cherries contribute to water pollution.

Coffee cherries are first depulped, and the pulps are washed away, exposing the seeds that is wrapped in a layer of mucilage. The mucilage is then gotten rid of through a long fermentation process and intensive washing. 

Figure 1: Coffee cherry anatomy. Image from: https://ulinzi-conservation-coffee.com/blogs/coffee/the-coffee-cherry

The first and major pollutant is the coffee pulps, as a series of damages occur after its introduction into a water system. According to Ratten et al., 2015, coffee pulps contain large amounts of organic matter that require high amounts of oxygen to decompose. Their "oxygen-loving" tendencies causes waters to become anaerobic, leading to fishkills and bacteria growth that threaten human and aquatic health (Ijanu et al., 2020; Ratten et al., 2015).

As a result of anaerobic water conditions, mucilage (another pollutant), which is soluble and largely made up of proteins and sugars, becomes tougher to decompose. While Tosif et al (2021) suggested the usefulness of muscilages for humans, the muscilage that get precipitated out in rivers can clog up waterways and worsen anaerobic conditions of the waters (Ratten et al., 2015).

Besides pulps and mucilages, a large amount of phosphorus have been found in coffee effluents. Coffee effluents refer to the wastewater discharged into water systems when the beans are washed. A study by Genanaw et al. (2021) found that phosphate contents in rivers near coffee processing plants be more than 5 times the amount under normal conditions. Such high amounts of phosphate encourages algae growth, which may lead to eutrophication (O'Niell et al., 2011).

Based on the pollutants released from wet processing, it seems that specialty coffees are not sustainable for the environment. However, the coffee industry does not back down from such set backs. Instead, wastewater treatment and other sustainable practices have been developed to reduce pollution during the processing phase. Next in the series, we will be exploring some mitigation strategies to manage these pollutants.

Bean on a Journey: An overview

From a farm to a cup, coffee beans undergo different processes before they are ready for consumption. Throughout these processes, conventional methods of production account for about 15.33kg of carbon dioxide per 1kg of green coffee (from Nab and Maslin, 2020), which is equivalent to the mass of 750 sushis! With more than 100 million bags of 60kg coffee being produced annually, one can only imagine the amount of carbon footprint produced. In this week's series of Bean on a Journey, we start by understanding the flow of coffee production. In the next two parts of the series, we will focus on the wet processing phase, which has recently gained more attention among the coffee community.

Generally, an avid consumer of coffee would understand the flow of production similar to what is shown in figure 1. Based on this knowledge, farming seemed to be understood as the most notorious for pollution due to the chain impacts caused by deforestation and farming processes (from Varcho, n.d.). Such impacts include water pollution from soil erosion and overfertilization, and air pollution from releasing sequestered carbon during deforestation. 

Figure 1: Coffee production process. Adapted from: https://ecoffee.vn/hanh-trinh-ki-dieu-mang-ten-from-farm-to-cup/

Other commonly known processes that contribute to pollution are roasting and brewing. During both processes, coffee grounds are usually disposed of as waste. As coffee grounds are organic, they release carbon dioxide and methane when they decompose in landfills, polluting the air, and contributing to global warming.

In between the mentioned processes, is the often-neglected coffee processing phase (refer to figure 2), which has recently risen in prominence due to sustainability efforts. Wet processing, in particular, is subjected to hot debates as it is water-intensive, and accounts for 54% of the water required in the entire production process (from Giraldi-Diaz et al., 2018). This suggests that a high magnitude of pollutants is being released during this process, and as such, garnering more attention to itself over the past few years.

Figure 2: Detailed flow of coffee production. The red box indicates the processes in question. Adapted from: Giraldi-Diaz et al., 2018

In this first instalment of Bean on a Journey, we explored the general flow of coffee production and briefly understood the impacts of the commonly known production processes. While lesser-known, coffee processing is gradually gaining prominence in its role in contributing to pollution. Hence, in the next instalment, we will ride the trend to explore the impacts of coffee processing in our environment.

Coffee Farming: Strategies in progress

Through proper management of coffee farms, production costs and fertilizer use can be lowered by 36.8% (from Thong et al., 2021). This suggests that the previously explored impacts associated with pollution can be alleviated with appropriate strategies in place. Here, we explore the effectiveness of one such strategy - sustainable certificates (SC) - in combatting the impacts of coffee farming that are associated with pollution.

Similar to our previous findings, Thong cited that environmental pollution is mainly caused by the overuse of chemicals, and the farmers were unwilling to decrease their usage as they believe that it negatively affects their yield and profits (from Thong et al., 2021). A solution devised was the introduction of SCs (from Thong et al., 2018), as such certificates entail useful programmes that educate farmers on sustainable ways of coffee cultivation to employ in their individual farms. For example, 4C's training taught farmers about reducing excessive fertilizer use via irrigation techniques, thereby reducing nutrient pollution to the soils and waters (from 4C). Hence, the incentives gained from achieving the SCs seem to be useful in reducing environmental pollution locally.

Besides environmental pollution, SCs are desirable as they help farmers increase their profits. As mentioned, with training from the different certification organizations, the cost of production of coffee is likely to decrease. Furthermore, as consumers are willing to pay more for sustainable products (from Thong et al. 2018), it suggests that if ceteris paribus holds true, a decrease in production cost and an increase in selling price equates to higher profits. This hence benefits the farmers' livelihoods and the economy.

While beneficial, SCs does have their disadvantages. The World Bank, for instance, observed a slow uptake of the certificates among the farmers, with only 25% coffee certified, compared to other major coffee producers like Brazil (41%) and Columbia (60%) (from the World Bank). The effectiveness of SCs in combatting deforestation is also not well-researched (from Baker, 2012; Gaitán-Cremaschi et al., 2018). Hence, suggesting that refinements need to be done to the SC programmes to produce better results.

In this series of Coffee Farming, we briefly answered how coffee farms in Vietnam causes pollution locally and globally, and we wrapped it up by discussing the SC programmes as a strategy to reduce the effects of coffee farming pollution. This series offers only a glimpse into the primary production of coffee. There are still more to be uncovered in the next weeks.

Coffee Farming: A global concern

Will more be merrier? Not in the case of Vietnam's coffee plantations. Smallholders in Vietnam have been expanding their plantations for higher profits since the coffee commodity boom in the 1990s (from Hall et al., 2011). Such expansion constituting mega-projects has impacts on the global scale. Hence, we will be broadening our lenses to understand the global impacts of Vietnam's coffee mega-plantations.

Mega-plantations (from Miles and Noboru, 2019) is a concept involving the conversion of large acres of land for the farming of cash crops. This concept (according to Hall et al.) is demonstrated in Vietnam, as smallholders were eager to reap the high profits tagged to the coffee beans. Besides profits, the expansion of farmlands were also driven by unsuitable soil conditions as mentioned in the previous post. Consequently, large-scale deforestation took place, replacing 19% of  Vietnam's forest (from D’haeze et al, 2005), and releasing tonnes of sequestered carbon into the atmosphere as carbon dioxide, causing air pollution globally.

Over 1.1 million hectares of degraded agricultural land in Central Highlands, Vietnam. Image by: Nongnghiep, 2020

In addition to mega-plantations, the productivity levels of coffee trees play a subsidary role in contributing to the abovementionned air pollution. Typically, coffee trees only maintain their productivity for 15 to 25 years. Within this timeframe, factors like deteriorating soil conditions and  water availability concerns may force smallholders to replant their farmlands or abandon it (from Scherr et al., 2015), resulting in the release of carbon, polluting the atmosphere.

Farmer struggling with drought conditions. Image by: Communicaffe, 2016

While skeptics may claim that carbon dioxide is not a pollutant, they are partially right. Carbon dioxide can be categorised as naturally occuring or man-made. Only the carbon dioxide that exist as a result of human activities is considered a pollutant, as it negatively affects the environment and humans via the global warming phenomenon, resulting in undesirable circumstances like extreme weather conditions and impairment of human respiratory health (from Sciencing, 2021).

This second part of the Coffee Farming series explored how the conversion of coffee farms to mega-plantations in Vietnam, and the productivity cycle of coffee trees can cause air pollution, which contributes to the global warming effect. In the last Coffee Farming installment, we will explore the existing measures in place to reduce pollution in coffee plantations.

Coffee Farming: Problems stemming from localized pollution

Coffee is one of the most consumed drinks in the world. According to Statista, there is a 13% increase in coffee consumed worldwide in the past five years, and just last year, more than 9 billion kilograms of coffee had been consumed. While consumers mostly benefit from the coffee industry, producers of coffee beans are often at the losing end, as they suffer different damages that accompany coffee production (from Chanakya and Alwis, 2004; UNEP, 2021). Hence in this first installment of the Coffee Farming series, I would be investigating the damages experienced by the local coffee plantation workers in Vietnam, as a result of pollution during farming.

 

This week, we will be discussing the origins of kopi - a traditional cup of coffee that many Singaporeans recognize. As such, we will focus on Vietnam's coffee plantations, which is the largest producer of robusta beans that is essential to a cup of kopi. 

According to the United Nations Environment Programme (UNEP), about 80-90% of the robusta beans are produced by multiple smallholders, with the main goal of turning high yields of coffee cherries into profits. The prevalence of unfavourable soil conditions, however, inhibited the smallholders from achieving their goals. While the article aptly identified several causes for the poor soil conditions, emphasis ought to be placed on the smallholders’ lack of agricultural knowledge, which resulted in overfertilization of soils, and hence the low cherry yields. Fertilizers mainly consist of nitrogen and phosphorus, which are known to promote plant growth. As such, it seems justified that farmers associate more fertilizers with higher cherry yields. However, overfertilization causes these nutrients to leach into and pollute the soils, causing the land to be less fertile. This kickstarts a negative feedback loop, as unknowing farmers continue fertilizing the lands in hopes of higher yield. Besides soil pollution, excess nutrients may dissolve and contaminate the waters, endangering people's health and contributing to the 150 million USD damage to the economy. Hence, education on agricultural techniques is essential to prevent further damages on the regional scale.

 

This first of the Coffee Farming series briefly explored how ignorance towards farming techniques can lead to regional soil and water pollution, which negatively affects the farmers, the people, and the economy in Vietnam. In the next post, we will explore how the farms cause pollution on a global scale, so stay tuned!