Anaerobic digestion of whey may become routine (but not for Little Miss Muffett!). As the move toward universal adoption of the Anaerobic Digestion process gathers in momentum, one thing is becoming clear. Mix it with slurry.
What is clear is that there are many more anaerobic digestion synergies than were first apparent, and this is one such!
According to the following Dairy Farm biogas article, where they have an excess of whey which is otherwise hard to dispose of, the mixing of this the “Little Miss Muffet” product with the farm manure is the big synergy story.
Some farmers take recycling to the extreme, to the benefit of both the environment and their bottom lines.
They are the often-unheralded pioneers of waste-to-energy technology, sometimes powering entire small towns with their byproducts. The most common waste-to-energy method is to employ methane-excreting bacteria in anaerobic digesters. These turn farm waste like cow manure and rotting vegetables into biogas to heat their property and even sell electricity back to the grid.
For dairy farmers making cheese, however, the process can get tricky. Getting rid of the huge quantities of cheese whey — the byproduct of the cheese-making process — is difficult.
Digester Stability Solution “Mix the whey with cow slurry”
That’s because the whey matrix is rich in fat and tends to rapidly acidify. That makes it unstable in anaerobic digestion reactors.
“It’s a real problem,”
said Elena Comino. She is an applied ecologist at the engineering department of Politecnico di Torino in Italy.
Now Comino and her colleagues have proposed an easy solution in a recent study. That is to just mix the whey with cow slurry, commonly known as liquid cow manure, to get the right pH balance.
Waste to energy
Outside of nursery rhymes, whey doesn’t come up a lot in most people’s daily lives. But it is a plentiful waste product – there are only 100 dairy farms in the U.S. that produce relatively large volumes of cheese but each one can create millions of pounds of whey in a single year.
Figuring out what to do with all of this waste can be a challenge. To figure out the perfect biogas-producing concoction to optimise the anaerobic digestion of whey, the Italian researchers tried mixing different proportions of whey and cow slurry.
Through trial and error, they found that a 50-50 mix of slurry and whey yields a methane concentration of about 55 percent in the biogas.
This figure compares favourably with the energetic potential associated with digestion of high-energy crops like maize.
“We obtained the most convenient mix in order to produce the best biogas in terms of quantity and quality,”
Few experiments have examined the biogas potential of co-digestion of slurry or manure with whey mostly because in the past anaerobic digestion was mainly used for wastewater treatment.
But the technology is becoming more popular in Europe and North America since it benefits the environment and is an additional source of income for farmers. “Cheese whey is a waste, but if you put it in a digester you can produce biogas so it becomes something you can reuse,” the fan of anaerobic digestion of whey, Comino, said.
In the past, standard practice was to keep agricultural waste like cow manure was kept in an open-air lagoon before spreading it on fields as fertilizer. During this process, methane—a potent green house gas—and other pollutants were released into the air, rainfall could cause the manure to run off and contaminate local waterways. On hot days, the manure smelled awful.
With a digester, rather than being left out in the open, the manure and whey is kept in a closed container, preventing green house gases from entering the atmosphere and further exacerbating global warming.
The biogas is instead used as a renewable substitute for natural gas, propane or other fossil fuels. As for the byproduct, it can be used or sold as fertilizer. Though European farms currently leads the way with anaerobic digesters, subsidies from state a local governments in places like Pennsylvania and Vermont are increasing the affordability for U.S. farmers to install digesters. In the U.S., there are around 160 anaerobic digesters on farms. Digesters number into the hundreds of thousands to a million for the rest of the world, according to the American Biogas Council.
Anaerobic Digestion of Whey Can Mean Selling back energy to the grid
Some U.S. farmers are ahead of the curve in their anaerobic digestion of whey. Charley Crave owns Crave Brothers Farm and Farmstead Cheese in Wisconsin and has been recycling cheese whey for years.
He estimates that he produces about 20 million pounds (10,000 tons) of whey a year. He loads both cheese whey and manure into the digester, and says he doesn’t have “a scientific recipe” for the proportions he uses. He added that the types of cheese he produces—like fresh mozzarella he sells to Whole Foods—are naturally lower in acidity.
Crave’s says there’s only a handful of dairy farmers in all of North America who use digesters to process whey.
Small dairy farms usually don’t have a cheese factory on their farm and so would have to transport the whey back to the farm. Perhaps more significantly, installing a digester can cost hundreds of thousands of dollars. After the initial installation cost, however, the digester begins to give back….
Please visit the original website to read more at Paging Little Miss Muffet: Energy from Cheese Waste
Watch the video below, to find out more about opportunities for farm biogas production.