Anaerobic digestion technology has been available in the US for many years – it’s a tried and true technology. However, in the early days, most digesters were built on livestock farms or attached to sewage treatment plants. Since livestock and sewage treatment plants typically are known for having their one particular odor issues, early digesters didn’t worry about odor control.
In fact, if you look at most digesters in Ohio and surrounding states today, you’ll see that many have open lagoons that they dump waste materials and sewage into – in fact, the technology at these plants simply is not designed and cannot handle odor issues.
At Synthica Energy, we do not believe this is a sustainable approach. In any community, be it near a sewage plant or even on a farm, the anaerobic digestion process has too many potentials for odor creation to simply ignore and leave open lagoons full of feedstock. In fact, there have been some cases where a poorly designed digester led to complaints from neighboring livestock farmers – the businesses with several hundred thousand head of hogs were complaining that the digester smelled worse!
Instead of ignoring the issue and trying to pinch pennies on digester design, Synthica Energy’s facilities are designed with advanced odor management in mind. We know that when locating a digester in any community, odor management is going to be the number one issue that all regulators and municipalities will want to watch.
Therefore, there are several critical odor control components that all of our digesters utilize.
First and foremost, our digesters are completely sealed vessels – it’s critical to our process that the bacterial process takes place in an oxygen-free environment, so at no time are the digesters themselves open to the environment.
Secondly, we do not use open lagoons to hold our feedstocks, and we do not process any human wastes from sewage treatment plants. Instead, all of our feedstocks come from food and organic product manufacturing.
Instead of receiving wastes in a lagoon, we have two primary methods for waste offloading: indoor tipping and liquid pump stations.
For organic liquids (such as spent brewer’s yeast), 5,500 gallon tanker trucks pull into our driveway, attach to our piping infrastructure, and pump their liquids directly into our cold digester. This is a digester that is “dead” and is merely used to bring the materials up or down to the proper temperature. Our hauling partners’ drivers will undergo training and digester offloading certification, and have experience at preventing spills as the connect, pump out, and disconnect.
For materials that are more solid and cannot be pumped (such as expired vegetables), our hauling partners will enter our enclosed tipping building. Once their entire vehicle is in the building, the doors to the building will be completely closed and high powered fans will create a negative air pressure environment so that air from the outside is actually pulled into the building (which means no odors can escape).
The truck will then dump it’s material into a grinder and receipt hopper, which will be pumped into the digester.
Outside the building, the negative air pressure fans will push their volume of air through a biofilter, which is a filter that uses carbon to trap any odors or volatile chemicals and prevent their release into the environment. Even when you are standing right next to the biofilter, odors will hardly be noticeable, and will only be an earthy smell, similar to mulch.
Lastly, to make sure that we are being good neighbors, all of our facilities will have odor measurement equipment installed onsite that samples air from the environment and provides us with data to trace and provide evidence of our good practices.
By using these advanced odor management technologies, Synthica Energy’s digesters will be a reliable, non-invasive part of the regional energy and disposal infrastructure for years to come.