| Selva Negra Coffee Estate Quarterly Newsletter |
| Fall 2006 |
| How Do We Manage Our Coffee Wastewater management |
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| Back in 1990 while looking for a way to alleviate the contamination of the rivers from the waste of the coffee washing cycle, we were approached by Rick Wasser from NOVIB. NOVIB was an organization from Holland, who was also looking for a way to help out the water problems of Matagalpa. We initiated the methane gas production section of this process as a joint venture between Selva Negra and NOVIB. The initial investment was an approximately $30,000. It was an amazing amount to invest at a time when our sales and production were low, but the commitment to the environment won out. The major contributing factor to this investment was the knowledge that the pollution created ended up in Matagalpa's drinking water. |
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| Following is a diagram that attempts to describe of how we manage and treat the wastewater at Selva Negra. |
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 Agua Miel (#4) |
The process starts with the receipt of the coffee. The coffee goes through the depulper (#1), where the outer shell of the coffee is removed, this is the pulp of the coffee. We use this pulp for the production of compost; this pulp is taken daily to the compost area (#2). The coffee is then moved with water to ceramic lined bins where they will ferment (#3). This water not only moves the coffee but also removes most of the sticky substance that surrounds each coffee bean; this water is what is used for the production of methane gas. The water (referred to as "agua miel") is channeled to a separate bin (#4). |
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 The Neutralization tank (#5) |
Once all the water is collected from that day's processing, it will be channeled to a tank, sort of like a pool. This tank is called the Neutralization tank (#5). In this tank Sodium Hydroxide (regulates the pH level of the water) is added. The desired pH is 6-7, which is necessary for an optimal operation of the bacteria inside the (anaerobic) bio-digesters. From here a valve will direct the water to the two bio-digesters. |
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 Bio Digesters (#7) |
The bio digesters (also known as bio reactors) will clean and decontaminate the water (#7), these are the actual tanks where the methane gas is produced. The reason for two tanks is that the flow of water during from the washing process is too great for one tank to hold it all. From these tanks comes out two outcomes: the methane gas that is channeled to a holding tank (#8) and water that is sent to an anaerobic water treatment (#11). The gas in the tanks will be used for two purposes 1- the main kitchen of the workers (#9) and 2- coffee roasting facility (#10). |
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 Anaerobic Water Treatment (#11). |
This is a rather quick process, the water does not sit in the bio-digesters; it goes in and out continuously. It takes only about 12 hours to start producing gas. We produce about 60 cubic meters of gas in the season; this will give us gas for the kitchen and the roaster for the entire 4-month season of coffee picking. Is it worth it? Financially not really, we spend an average of $4,000 on the Sodium Hydroxide for the 4-month period. We could buy butane gas to power the kitchen and the roaster for less than that, but the reason for the process is environmental, not financial. The fact that we get gas at all in a bonus to an environmental investment for the benefit of Matagalpa's drinking water. |
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 Lagoon (#13) |
Although by this stage we have significantly cleaned the water and produced sufficient methane gas to power the kitchen and the roasting facility, we continue to clean the remaining water held in the anaerobic water treatment. The water will continue to a lagoon (#13), overflow of water is channeled to the next lagoon, (#14) which is also a bio filter (a lagoon with shallow water plants where oxidation takes place), since it also receives water from the cleaning of the cow stable and chicken area. The water from both of these lagoons is used to irrigate the pastureland (#18) |
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 Lagoon (#14) |
In addition, we retain some of this water through the use of dams (#15, 16 &17) so we can hold on to the water for most of the season (December-April) and keep all our pastureland moist during this time of the year, as well as fertilized the pastureland with the nutrients from the coffee water. By holding this water we avoid any discharge of wastewater to the river and use it within the estate to irrigate the pasturelands |
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What are other farms doing with their wastewater? Other methods for wastewater management include the most obvious and troublesome, yet most utilized of simply dumping it into the river. Another method is the creation of a holding tank of sorts (pilas). Basically these are large tanks where the wastewater is deposited and treated with talc to reach the desired pH. The major problem with these is that during the coffee season the quantity of water is too great for the size of the tanks, and overflow instantly reaches water sources. |
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