The largest project we undertook in Costa Rica caused us to deal with a lot of crap--literally--because we built a biodigester. But what is a biodigester, exactly? Also known as anaerobic digestion, a biodigester is a collection of processes in which organic waste--or biodegradable material--is broken down in the absence of oxygen. It is a system that manages waste and also acts as a source of renewable energy, as it produces methane gas that can be filtered out and reused for alternate purposes such as cooking. The final product of the biodigester system is water, which goes through a series of purification processes to ensure that it is as clean as possible. You're probably thinking, "Why on earth would someone want to drink water that came from poop!?" Well, you wouldn't. But that's only because the water at the very end of the processes is only roughly 95-96% purified, which isn't considered drinking water. This water can instead be recycled for other things such as laundry or irrigation purposes.
Let's walk through the steps of anaerobic digestion, told in simple, straightforward terms so you can make sense of this whole crazy thing.
Let's walk through the steps of anaerobic digestion, told in simple, straightforward terms so you can make sense of this whole crazy thing.
- Organic waste (fecal matter, green products, etc.) is put in the first separation tank and solids separate from liquids. Here, the sediments sink to the bottom.
- Gate is lifted and contents from tank 1 move into tank 2, where they continue the liquefying process so that even more solids are broken down and separated.
- The next gate is lifted and contents from tank 2 move into tank 3. This is the final step where contents are compressed and liquefied before moving into the biodigester bag.
- Contents progress through pipe into the biodigester bag.
- While inside the biodigester bag, the anaerobic process causes the separation of solids and liquids, and as a result, gas is produced. As the solid matter is decomposing, methane is produced, inflating the biodigester bag.
- Methane gas is filtered out through PVC pipe to another source where it can be used, such as for cooking in the kitchen (All the gas used in the kitchen at Buena Vista lodge comes from their biodigester!).
- Water exits the biodigester bag and is 84-85% purified at this point.
- This water moves into lily pond rows where it cycles through and is purified by the plants.
- After completely cycling through the rows in the lily ponds, the water is 94-96% pure.
- This water then runs off into a pasture (at least at Buena Vista Lodge it does) and is used for irrigation, laundry, etc.