BioCycle July 2016
Combination of food obsession and election obsession is responsible for this column. I have been obsessively reading the 538 Nate Silver website, one devoted primarily to the use of statistics to inform discussions on politics and sports. While checking on my chances of getting Trumped or Berned a month or so ago, I was pleasantly distracted by an article about cheese. In this case my food obsession was an even greater distraction than my political obsession. It turns out that in the U.S., we produce one billion pounds of cheese a month. Mozzarella comes in first with 341 million pounds produced last February; cheddar comes in second at 258 million pounds.
Much of the recent discussion on food waste has focused on making sure you only make enough Mac and Cheese to satisfy yourself and your family. Don’t buy excess cheese so you end up with that green mold coating. It may be appropriate for some of the fancier varietals but not for cheddar. And any scraps should go to an animal, a digester or a compost bin. But what about leftovers when you make the cheese to begin with? Most growing and food processing result in some type of residual material, which is often present in greater quantities than the final product. Almonds and their shells are one example. Cheese and its whey are another.
To make cheese you ferment milk, turning the lactose into lactic acid. At the appropriate stage of fermentation rennet is added to bring the cheese solids together. The leftover liquid is called whey. Different types of cheese generate different quantities of whey with slightly different characteristics — sweet (most hard cheeses), salty (a relatively small fraction of high salt whey from cheese processing) and acid (from Greek yogurts, cream cheese and cottage cheese). When you make cheddar cheese, only about 5 percent of the whey generated is considered salty. Sweet whey is the easiest to derive value from, e.g., it contains the protein and the residuals discussed below.
So Much Whey
Ninety five percent of the water that was in the milk ends up in the whey. You can do the calculation for the billion pounds of cheese a month, and even thinking about that calculation will make it obvious that’s a lot of whey. ‘No whey there could be that much,’ you might even be tempted to say. Whey may be a waste from making cheese but it is much more than dirty water. The chemical oxygen demand in each liter of whey is about 75,000 mg. The lactose concentration is about 40,000 mg (Rajeshwari et al., 2000). The whey also contains significant amounts of NPK: nitrogen (14% crude protein), phosphorus (0.9%) and potassium (1.3%) on a dry weight basis (Beef Magazine, 2011).
Whey also contains minerals from the milk that do not make it to the cheese. If you assume a six percent solids content or dry whey content, that means that each month, each billion pounds of cheese generates about 1,200 million pounds or 600,000 tons of whey, according to the Dairy Processing Handbook (Tetrapak, 2015). While eating whey was fine for Little Miss Muffet, most of us stick with the cheese. For many years whey was a waste.
Whey can be viewed as an environmental disaster waiting to happen or as an opportunity. Traditionally it has been a bit of both. Many producers would spray whey on farmers’ fields where it was an excellent source of recycled nutrients if used at appropriate rates and at appropriate times of the year. That was not always the case, leading to eutrophication of streams. Direct discharge of the whey into water, another common practice, did that only with no pretext of benefit. Another common practice was using the whey for animal feed — not a high return but an excellent option. When you go to Italy and eat pork in Parma, it tastes good in part because the pigs have been eating the whey from Parmesan cheese for centuries. Whey was also used to de-ice roads.
More recently, capturing and using the components of whey has become more common. While these products are not anything that you would spread on a cracker, most end up in foods we eat. Products from whey include: powder, made by separating the solids and removing some of the minerals; protein concentrate, made by separating the proteins; and protein hydrolysates, protein concentrates that have undergone some chemical transformations. Common uses for these materials include baby foods, yogurts, ice creams, power bars and other processed foods. For the one billion pounds of cheese made in March 2016, about 83 million pounds of dry whey protein products were produced, the majority of them destined for human consumption (USDA, 2016). What enabled this transition from waste to whey products are separation technologies that allow for capturing the proteins from the water.
Sounds great, right? What was a waste or underused material is now captured and sold for the big bucks. True in part. The catch is that the protein in the whey is of high enough value that this level of technology for capture is merited. Not so much for the minerals and sugars that remain in the whey. In fact, if whey is dried so that the proteins, sugars and minerals are all together, the resulting material called dry sweet is of relatively low value. Most often, whey proteins are the product and the residual material that contains the sugars and the minerals, called permeate, is fed to animals. Depending on the price of lactose and animal feed, the leftover solution can also be discharged to wastewater treatment plants or fed directly into anaerobic digesters.
The state of Wisconsin is recognized as America’s Dairyland. It is also the #1 producer of cheese in the U.S., with California coming in a close second. Dean Sommer at the Center for Dairy Research at the University of Wisconsin was a great source of information for this column. He also provided data on where the residuals from cheese production go in Wisconsin. Direct landspreading still gets a majority. Municipal treatment plants also get a significant fraction. However some manufacturers have their own digesters, or are being serviced by companies such as GreenWhey Energy in Turtle Lake, Wisconsin, which built a digester and offers residuals transport. Digesters can also accept the salty whey and the acid whey.
While cheese and whey make for an interesting story, the main point of this column is that when we think about food waste, we also have to consider the waste that is generated when the food is being produced. Markets can work to encourage the capture of value added products from these materials. But markets are often not enough. It might be that a combination of markets, regulatory guidelines (to limit land and water disposal) and energy incentives are what is required. Because as we all realize — no way is it a good thing to let whey go to waste.
Sally Brown is a Research Associate Professor at the University of Washington in Seattle and a member of BioCycle’s Editorial Board.