N. S. MASTRUP (1), N. Coote (2); (1) EP Minerals, LLC, Reno, NV, U.S.A.; (2) Filtencia, Paris, France
Filtration with diatomaceous earth (DE) is getting some bad press of late as being old-fashioned and environmentally unfriendly. But is this really deserved? Probably not. DE filtration is more subtle than the purely mechanical process provided by crossflow microfiltration. DE works more like isinglass finings than filtration when one analyzes what is removed. Both eliminate haze-inducing species while leaving similarly sized components in the beer that are responsible for foam retention, color, and mouthfeel. Although crossflow filtration costs are decreasing, membrane life and cleaning complexity are still uncertainties that plague even the most well-established sectors where the technology has already taken hold. A good example is fruit juice filtration. Much of the world’s apple juice has been filtered on crossflow membranes since the 1980s, and the industry has been fighting with Alicyclobacillus infections ever since. The wine industry is a more recent adopter of crossflow filters and arguably has an easier time dealing with the infection risk of unsterilizable polymeric membranes—alcohol and anaerobic conditions help—but the move to crossflow has been more inspired by a need to automate qualitative environmental arguments (“green image”) than a desire to reduce production costs. Trying to make a cost comparison between DE filtration and crossflow is like picking your way through a minefield. The only certainties are that some brewers have deliberately chosen crossflow even with the knowledge that it is not the most cost-effective filtration method, basing their decision largely on environmental concerns about filter powder handling and spent cake. At the same time, they play down the fact that the cleaning of a crossflow membrane requires more chemicals than those employed for a DE filter and that the membranes are composed of plastic parts that ultimately need to be disposed of. In any case, with the movement of bottles and cans across continents from production to sale, “green image” arguments such as these pale into insignificance given the global nature of beer branding and sales. The packaging itself carries its own huge environmental burden. The CO2 footprint of any filtration step is dwarfed by such issues. The resurgence of local microbreweries is a healthy sign for the environment, but perhaps we should go “whole hog” and back to a time when beverages (beer, wine, milk) were collected from the point of production by consumers. Don’t forget to bring your growlers.
Niels Mastrup has worked in the field of mineral precoat filtration for nearly 25 years in a variety of capacities, including total quality management, sales, technical services, and marketing. He is currently working for EP Minerals as director of filtration technology and is based at their global headquarters in Reno, NV.