Don’t Throw That Out! Turning Dairy Waste into Microalgae Products.

Labbé, J.I., et al. 2017. Microalgae growth in polluted effluents from the dairy industry for biomass production and phytoremediation. Journal of Environmental Chemical Engineering 5: 635-643

http://dx.doi.org/10.1016/j.jece.2016.12.040

The Dairy Farm Dilemma.

Did you know that cows poop? Hopefully you did! Perhaps the bigger question is what do farmers do with all that waste? Dairy farms need to frequently clean their facilities, which in turn creates large quantities of wastewater, or dairy effluents. Milking parlors, cattle standing yards, and occasionally leachate from manure heaps all contribute to the wastewater load that farms need to address. Contaminants in wastewater include cleaning and disinfectant chemicals, high ammonia nitrogen, and other animal waste (like poop!) that bacteria will utilize. However, the bacteria can use up all the oxygen in the water, which can severely endanger the aquatic life and impact water quality. If saving the environment isn’t enough, the OECD has shown that overall runoff from agriculture has become one of the most expensive forms of nonpoint source pollution in the United States, costing billions annually to clean up (OECD 2017). That’s why it’s so important that wastewater be treated before it is released back into a larger body of water. While some larger facilities can afford high-tech methods of treating their wastewater, it may be difficult to implement such techniques on small and medium scale farms.

An example of an Algal Production Facility at Iowa State University. Photo Credit: BioCentury Research Farm, Iowa State University.

Turning Waste into Reward.

One possible solution is to use the wastewater to grow microalgae that can be harvested and used in commercial products, such as biofuels, biofertilizers, and animal feed. The process works like this: Microalgae, microscopic photosynthesizing organisms, use sunlight and nutrients (such as nitrogen and phosphorus from wastewater) in the water to grow. Bacteria that are also present in the water are able to break down the waste, and turn it into a nutrient form, which microalgae can use to grow. Reseachers at the ProCycla Laboratory decided to test this high potential method with an experiment aimed to see how well microalgae grew in different types of dairy effluent.

Cattle Standing Yard (above), Milking Parlor (below). Image Credit: dairygood.org

The Setup.

The researchers set up their experiment to investigate how different types of microalgae would grow in different types of wastewater from a dairy farm in Chile. The farm uses well water to clean their milking parlors, and canal water to clean their cattle standing yards. This creates milking parlor wastewater (high in detergent and cleaning chemicals) and cattle standing yard wastewater (high in animal waste). So the research team collected water from the well and canal, in addition to wastewater from the milking parlors and cattle standing yards, to compare how microalgae grew in water before and after waste was added. This created four types of water: 1) well water, 2) canal water, 3) milking parlor wastewater (cleaned by well water), and 4) cattle standing yard wastewater (cleaned by canal water). The research team collected microalgae species Chlorella sp. and Scenedesmus sp. from a pond near the farm to test their growth rate and density among all four water types. They added Chlorella and Scenedesmus separately to each water type, and then ran the 14-day experiment.

Microalgae species used in experiment: Scenedesmus sp. (left) and Chlorella sp. (right). Image Credit: Dos Santos et al. 2013.

Do We Have a Winner?

The study found that the different types of microalgae grew better in different types of wastewater. For Chlorella, the best growth conditions were in the wastewater from the cattle standing yards due to high nitrogen concentrations. For Scenedesmus, the milking parlor wastewater was better suited, which had higher phosphorus concentrations. In addition, Chlorella can better tolerate a high ammonia nitrogen environment than Scenedesmus, whereas Scenedesmus has thick cell walls that can resist detergents and tolerate milking parlor effluent. These results show that dairy effluent can be used to grow microalgae, and their high growth rates and cell concentrations make them viable cultures for biomass production.

Money, Money, Money? Not Yet.

More research still needs to be conducted on microalgae species and wastewater composition, as this study demonstrated that both could be variable and have different results. Chorella stands out because its biomass can be used in a variety of products, whereas Scenedesmus can be more easily harvested because of its capacity of form colonies. In addition, the composition of dairy effluent may vary from dairy farm to dairy farm, which impacts the success of microalgae growth. Another question is whether the microalgae can be grown on the farms, or if wastewater would be transported to microalgae production facilities. Once grown and harvested, prospects for commercial use are very favorable for biofuels, biofertilizers, and other valuable chemical forms. In addition, it also saves billions of dollars annually that would have been spent cleaning the water bodies that receive this pollution. Selecting the proper microalgae that fits the effluent composition will be key in scaling this option up for small and medium dairy farms to use as a means to treat their wastewater.

References.

Dos Santos, M.O, et al., 2013. Rheological behavior of Chlorella sp. E Scenedesmus sp. cultures in different biomass concentrations. Engenharia Agricola 33: 1063-1071.

Labbé, J.I., et al. 2017. Microalgae growth in polluted effluents from the dairy industry for biomass production and phytoremediation. Journal of Environmental Chemical Engineering 5: 635-643

OECD (2017), Diffuse Pollution, Degraded Waters: Emerging Policy Solutions, OECD Studies on Water, OECD Publishing, Paris.

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Nick Iraola

Nick has a Master of Science in Marine Science from UNC Wilmington. His master's thesis research pertained to eutrophication and nutrient cycling within an urban blackwater lake in Wilmington, NC. Currently, Nick works for the Cape Fear Public Utility Authority testing drinking and waste water for safe consumption and discharge. Nick also works as a part-time research assistant at UNCW's Center for Marine Science in the Aquatic Ecology Laboratory and the Nutrient Analysis Core Facility. When he's not sciencing, Nick enjoys running, swimming, cooking, sailing, and catching up with friends and family. His favorite candy is Reese's pb cups, because what is there not to like!?

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