Many of you are aware of the efforts of the Cayuga County Soil and Water Conservation Disttrict to build and run a anaerobic digester. We started this journey way back in 2005, and this year we are bringing the plant on line. So, it seems to be a good time for an update.
One of the reasons the CCSWCD took on such a large project was to offer a platform for new alternative technologies. Mixed into all this was the idea that we could make power for our county buildings and do some good for the environment. In fact, as far as we know, we are the only county facility being powered with cow poo. So what makes our digester different? The design uses gas pressure that comes from the digestion process to mix the contents instead of using traditional mechanical mixers, or the reliable plug-flow style that is often used on farms. This digester is being used in Europe and Asia, but as far as we know, not in the states. We also use a “European style” biological gas scrubber to remove H2S from the gas before it gets used by the power plant. Both of these have been working very well. The bio-gas conditioner manufacturer has now installed two more of his plants on farm operations in Cayuga County to good results.
Our plant is set up to run automatically when there is enough gas and shut down when the gas runs low. The power plant will also adjust to run at various electricity production levels, based on the gas available, with half power being the minimum. At 315 to 625 kw, we are creating enough power for 50 to 100 houses. Or as we are set up, to supply power to the SWCD building, the county jail, the county nursing home, and then sell to the grid.
As with any power plant, power will not be made if there is no fuel to run the generator. Unfortunately, people tend to look at the digester concept and say that it is silly to truck in manure. However, a coal plant has coal trucked in, an oil plant has oil, and so on. So if we stand back and look at the plant as a power plant only, the idea that we are trucking manure as a fuel source is not as far-fetched as one might think. The European model has the farmers trucking in the manure; we decided to keep the operations in house for now. This lets us keep an eye on the manure and what is in it. We still need to see how the trucking works out, but for a simple comparison, our digester will make the equivalent of 50 gallons of gasoline per hour, or 1,200 gallons per day. To make the 1,200 gallons, we use less than 100 gallons of diesel fuel, so we are making 12 gallons of gas for every 1 gallon of diesel used.
Part of the idea behind the CCSWCD project was that digesters can offer a bunch of environmental benefits. Methane gas, which is going to come from the break down of the manure, whether it is in a digester or in a lagoon, has a greenhouse gas warming potential 25 times as great as carbon dioxide. We capture the gas, burn it off, and make power that hopefully is replacing power that is coming from “traditional” sources. Throughout the digestion process, the N-P-K does not change, however the digestion does break down the solids. The manure we bring in is about 7-11 percent solids, and it is returned to the farms at 3-4 percent solids. Our process does add water and elemental sulfur to the effluent. We also use the grease that comes from the wash drains in food production. This grease is not the same as fryer grease that can be used to make bio-diesel, it is a true waste product. Anyone who has worked in a restaurant can tell you what this stuff looks like. Septic tank cleaners take this stuff to sewer treatment plants where it is treated and landfilled. We can use this grease to increase the methane production and safely return it to the environment. So in the end, the farm is getting back a very uniform, cleaned and usable effluent.
Another benefit that is often overlooked is that the power is being produced in Cayuga County. We try to source parts and supplies through local and regional businesses. Our trucks are serviced through local businesses, we use local electricians to service our plant, and so on. So we like to think that we, as well as all the other local digesters, in addition to having an environmental benefit are also having a local economic benefit.
So far, we have just begun to check off some of the goals set out in our business plan, but it is a beginning. One of our goals is education, and we are always open to visits. If you happen to be in the Auburn area, feel free to stop by and see us.