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Innovation: Biofuel derived from coffee processing wastewater


Reg Tucker

Four-year sustainability project reveals that farmers in Central America were able to extract biofuels from the wastewater produced by coffee mills.

Who knew that the process associated with the production of something so sublime as coffee — that essential beverage that helps caffeine lovers around the world jump-start their day each morning — could generate copious streams of wastewater? Seems incongruous, but it’s true. But there is a silver lining: As it turns out, all that aromatic effluent can be utilized as a viable fuel source for energy.

That’s according to UTZ Certified,which recently published the results of a four-year project on coffee wastewater treatment in Latin America.1 According to the company, the region produces around 70 per cent of the world's coffee and is, incidentally, the continent where 31 per cent of the world's freshwater resources are located. Yet, coffee production generates a great amount of wastewater that is regularly released untreated into rivers, affecting aquatic fauna and flora as well as downstream communities. Additionally, coffee wastewater comes along with tons of organic waste and high toxicity, which affects the soil and generates considerable amounts of greenhouse-gas emissions — particularly methane. (As greenhouse gases go, methane is more potent than CO2.) 

The process

Coffee processing is an energy intensive process and a potential source of contamination, according to UTZ Certified. Coffee waste (e.g., pulp, and waste water that leave the coffee processing units) are rich in organic matter, posing a threat to natural water bodies if not treated correctly. During the “wet method” process — which is prevalent among Latin American coffee plants — enormous amounts of waste are generated in the form of pulp and residual water.

According to UTZ, this wastewater boasts a ‘chemical oxygen demand value’ that varies between 18,000 and 30,000 milligrams per liter. Oxidation of the organic matter in the water is done by means of microflora of bacteria that feed on the matter while consuming oxygen. In cases of substantial discharge of wastewater into natural water bodies, the oxygen is significantly depleted (anaerobisis) thereby destroying the aquatic fauna and flora.2

An investigation into using wastewater to produce biogas as an alternative energy was explored as a means to mitigate the aforementioned negative impacts. Specifically, the Energy from Coffee Wastewater project focused on the methane generated by anaerobic methanogenic bacteria as a source to create electrical energy. In application, researched figured that up to 70 per cent of the fuel used by diesel generators in a pulping machine could be substituted with this coffee-based biogas. This energy also generates a substantial amount of the heat needed to dry the processed coffee and, theoretically, could replace other fuels such as those used in kitchen stoves.
     
The participants 

The Energy from Coffee Wastewater project, which began in 2010, entailed the installation of customized coffee wastewater treatment systems and solid-waste treatment mechanisms in eight coffee farms varying in size in Nicaragua, ten in Honduras and one in Guatemala. ‘Pilot’ sites for the first coffee season of this project included: CISA, a large exporter with its own processing plant; CECOCAFEN, a cooperative with a central processing plant; and El Polo, a cooperative where smallholders process their coffee themselves.

CISA and CECOCAFEN focused on the challenges of substantial water usage during the wet method process for extraction and the negative environmental impacts as a result of insufficient treatment of the wastewater. (High energy costs were also addressed). Meanwhile, El Polo focused on environmental impacts created by insufficient treatment of wastewater discharged to the river, deforestation resulting from chopping firewood for preparation of food and the health issue of inhaling the smoke.

The results

At the CISA pilot site, located in Diriamba, Nicaragua, operators were able to
generate an average of 200,000 kW of power using biogas from the coffee wastewater. According to Gilberto Monterrey, technical director of the biogas plant, this represented savings of $40,000 annually. Furthermore, not only is the wastewater management process he adopted more modern, but it also allows more efficient treatment, which ensures less pollution, Monterrey said. And to add the proverbial icing on the crumb cake, the new facility also allows a more optimal use of water to wash coffee, reducing it to less than 66,000 gallons per year.

The benefits didn’t end there. Other tangible results of the Energy from Coffee Wasterwater project ranged from the prevention of local deforestation of native trees to better indoor environments for families who were able to replace firewood with domestic gas stoves — using, of course, the converted coffee wastewater as a fuel for cooking.

According to Han de Groot, executive director at UTZ Certified, the Energy from Coffee Wastewaterproject has proven that is possible to simultaneously generate energy, tackle climate change and protect water resources by treating discharges from coffee mills.

“Coffee production is only environmentally sustainable when water is used efficiently and polluted water from the wet-mill process is treated,” de Groot explained. “Local ecosystems do not have the capacity to clean the large amounts of contaminated fluids. Furthermore, rural communities and coffee production depend intrinsically on a ready supply of fresh water. So, if we want to talk about coffee produced in a sustainable manner, then wastewater must be treated when released into the environment.”

Not only did the four-year project reveal that a significant amount of biogas could be generated and used as an energy source, but it also provided benefits in terms of resource conservation. According to de Groot, the mills that participated in the study were able to ultimately all of the wastewater generated in processing the coffee. Further, the plants found that they were able to reduce water consumption by 50 per cent. These steps, according to UTZ Certified, resulted in the prevention of the release of greenhouse-gas emissions into the atmosphere.

The positive impact of the project on over 5,000 people in the region where the project was conducted has inspired UTZ Certified to replicate the Energy from Coffee Wastewater initiative in other countries. In fact, UTZ Certified is currently introducing the wastewater treatment technology in Peru and Brazil. UTZ hopes to get further funds and industry's support to replicate the initiative in Africa and Asia.

     UTZ Certified stands for sustainable farming and better opportunities for farmers, their families and our planet. The UTZ program enables farmers to learn better farming methods, improve working conditions and take better care of their children and the environment. For more information, please visit www.utzcertified.org.  

 

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