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Milk’s environmental impact

October 13, 2020

     A big misconception is that milk is taken directly from a cow and put in a bottle.  But this is not entirely true as the process of turning raw milk into consumer milk is much more complicated than that. The process has an enormous environmental impact.  In recent years there has been a rise in popularity of plant-based milks because of its taste and health benefits, but are these new substitutes better for the environment?  The food sector has the highest consumption of water, and in fact, 86% of all the water in the world is used to grow food. The process of producing each type of milk generates their own water footprint.  A water footprint is an indicator of how much water both directly and indirectly is used by a customer or producer.  So you and I both have water footprints from eating food, driving our cars, taking showers, and many more things in our daily life.  The water footprint for milk is calculated by the total volume of freshwater that is, directly and indirectly, used to produce it.  The three main types of milk I am going to talk about will be cow milk, soy milk, and almond milk, and the water waste that is accumulated as part of the production process for these types of milk. 

     Growing up I always believed like many other people that milk came directly from a cow straight into the container.  But that is a huge misconception about the milk industry.  In reality, the milk needs to be processed multiple times before it can be packaged and shipped out.  Each year the milk industry generates 3.739 to 11.217 million m^3 of water waste. This amount of water is 1 to 3 times the volume of milk that is processed and packaged each year.  That means that for every 1L of cow milk 1,050L of water waste is generated.  Because of the lack of interest and knowledge in this topic from general people, many do not know the environmental impact that happens because of all the waste.  Some of this water waste accumulates during various systems of milk production in the factories, such as cleaning systems, cooling systems, and steam generators.  This cleaning system results in the clean water waste mixing with the cleaning solutions that are pumped through the unit.  This chemical mixture is still in the water when it is disposed of into the nearby river, land, and fields.  This chemical mixture is a highly odorous black sludge that can cause destructive environmental impacts.  

     Recently there has been a rise in the demand for milk alternatives that provide better health benefits.  Because of this, there has also been a rise in many misconceptions about the environmental impact of these alterations.  I know when I first learned about alternatives like soy milk and almond milk, I believed that while they had great health benefits they also had positive environmental benefits along with it.  While they do have the least water waste with the processing of the milk; other areas of the production process also accumulate water waste.  With all three milk substitutes, there is an increase in water waste from the crop production of these products.  For soy milk, every 1 L generates 297 L of water waste.  

     Sadly out of the three milk options I looked at, there truly is no winner when it comes to lessening the environmental impact just based on picking a new milk substitute.  In the image, you can see the simplified engineering diagram for the production of milk.  In two of the stages for all types of milk, water is entering the system for crop production and the processing of milk.  While the amount of water that is used for each step is different depending on the milk, there still is an amount of wastewater that exists for each milk type.  But there are some ways production companies can adopt to decrease their water waste.  One way for almond milk would be to shift the sourcing and production of almonds to locations that have a more efficient irrigation system.  For cow milk, research might find a better way to streamline the process and to lessen the amount of chemicals introduced to water waste. 

References: 

Boguniewicz-Zablocka, J., Klosok-Bazan, I. & Naddeo, V. Water quality and resource management in the dairy industry. Environ Sci Pollut Res 26, 1208–1216 (2019). https://doi.org/10.1007/s11356-017-0608-8

Courtney A. Grant and Andrea L. Hicks.Environmental Engineering Science.Nov 2018.1235-1247.http://doi.org/10.1089/ees.2018.0233

Ercin, A., Aldaya, M., & Hoekstra, A. (2012, February 28). The water footprint of soy milk and soy burger and equivalent animal products. Retrieved October 08, 2020, from https://www.sciencedirect.com/science/article/abs/pii/S1470160X11004110?casa_token=e3EkrZ26r6IAAAAA%3Ad8BXC4T7XhPCDuL0uNN61qzA0XOht6XXqBIRrM1SH7_nN77SA7FbNk8jDSXLtqZUB29NnRasDXU

Tikariha, A. , & Sahu, O. (2014). Study of Characteristics and Treatments of Dairy Industry Waste Water. Journal of Applied & Environmental Microbiology, 2(1), 16-22.

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  Timothy Durham was convicted of rape when a test showed his DNA genotype matched the DNA recovered from the crime scene. Eye witnesses testified that Durham was in a different state at the time of the incident, but he wasn’t exonerated from his 3000 year sentence until follow up DNA analysis showed that the preliminary forensic analysis used in the trial was misinterpreted (Thomas et al.). DNA testing serves an invaluable part in our criminal justice system, but it comes with complications and bias that can lead to wrongful convictions and misinformed juries.  

Background:

Forensic genetics aims to identify the origin of a biological sample. It can be traced back to Karl Landsteiner who discovered human ABO blood groups. With blood groups, suspects could be eliminated based on their blood type. For example, if a suspect had type A blood and there was type B blood left at the scene by the perpetrator, the investigators could rule out the suspect. Unfortunately, the reverse didn’t work. If the suspect and perpetrator both had the same blood type, it can’t be concluded that the suspect was guilty. Blood identifiers evolved into 8 distinct categories which improved the ability to eliminate suspects, but could only conclude that (if the system matched) it might be the perpetrator or this person might be related to the perpetrator (Jobling and Gill). The field evolved in the 1980s with the discovery of Minisatellites, lines of repetitive DNA that don’t encode proteins. Minisatellite patterns in DNA create what we know today as the DNA fingerprint, and it has a much higher accuracy rate than previous methods (Augustyn et al.). Around the same time, a breakthrough for victims of sexual assault was discovered. In the case of assault, bodily fluids of both the victim and the assaulter can get mixed. A process called differential lysis was created which could selectively increase the concentration of sperm in a fluid sample thereby allowing for accurate DNA testing (Jobling and Gill). Forensics evolved to use single-locus probe testing after several years because of its ease of interpretation. It looked at specific minisatellites that had high variability between subjects. This was the first DNA-based method to be used in a criminal investigation. Two murder homicides from several years apart were connected using DNA evidence. The evidence was then used to exonerate an innocent man, and the guilty party was found when he tried to evade mandatory DNA testing for all men in the small town. His guilt was then reinforced when the DNA profiles matched, and he gave a confession (Jobling and Gill). Finding DNA at a crime scene doesn’t guarantee that you’ll find a murderer. There are issues with non-pure samples and limited samples that make DNA work difficult, and accreditation of facilities and new techniques and take time (Jobling and Gill).  

Subjectivity of DNA Interpretation:

In a 2009 publication, the National Academy of Science discusses the possibility for subjective influence in lab based forensics. The interpretation bias happens in complex cases where, for example, there could be a mixture of DNA. A study published in 2011 looked specifically at this issue. A gang rape happened in Georgia, and the mixture in DNA from the case was used to prosecute one suspect after another suspect took a plea bargain to testify against him. With DNA mixtures, there are three possible conclusions: suspect excluded, suspect cannot be excluded, and inconclusive. If the suspect is excluded, it means that there’s little to no possibility that his DNA is part of the sample. If the suspect cannot be excluded, it means that there’s a possibility that his DNA is part of the sample. In the trial, the DNA examiners who knew the context of the case concluded that the suspect being prosecuted could not be excluded. The 2011 study gave the DNA evidence from this case and the DNA profiles of the suspects to 17 forensic examiners. These examiners had no context of the case, and they all worked independently. Of the 17, only 1 came to the same conclusion (suspect cannot be excluded) as the examiners who knew the context of the case. Twelve of the 17 concluded that the suspect who was prosecuted and convicted had no relation to the DNA found in the sample. Not only does this show that subjectivity occurs due to the context of the case, but the 17 examiners came up with different findings based on their past experiences meaning that not all DNA analysis is objective. Some organizations like the Scientific Working Group on DNA Analysis Methods say that quantitative statistical evidence should be presented with every categorical conclusion, but the US doesn’t require this (Dror and Hampikian).

False Positives:

There are two categories that cause wrongful identification in a DNA report: coincidental matches and false positives. Coincidental matches are DNA matches between two unrelated people. The probability of these matches is about 1 to 500,000 for white individuals and about 1 to 350,000 for black individuals. This small probability of coincidental matches makes people feel confident in DNA evidence. False positives, on the other hand, are matches between DNA and test DNA that result from issues in the forensics lab. There have been multiple cases of forensics labs accidentally switching victim and suspected rapist DNA which lead to convictions that were later overturned when the lab realized the error. There are also cases of misreading or misunderstanding a sample. In a case from 1993, a man was convicted of rape because someone interpreted a mixed sample of victim and perpetrator DNA as an individual sample. The conviction was again overturned. To prevent false convictions, retesting DNA is allowed, but it’s not an efficient solution. Many people are pushing for statistical information on the probability of false positives, so that the jurors can make accurate judgements based on DNA evidence (Thomas et al.).  

Conclusion:

DNA analysis is a useful tool for the criminal justice system, but subjectivity can be an issue in forensic testing. To combat wrongful convictions, there are organizations like The Innocence Project who use DNA testing to free the innocent, but reformed forensic testing standards should be put in place to prevent subjectivity and to ensure juries are correctly informed during trials. https://www.innocenceproject.org/    

Citation:

Augustyn , Adam, et al. “DNA Finerprinting.” Encyclopedia Britannica , 26 Apr. 2018, www.britannica.com/science/DNA-fingerprinting#ref153186. Dror, Itiel E., and Greg Hampikian. “Subjectivity and Bias in Forensic DNA Mixture Interpretation.” Science & Justice, vol. 51, no. 4, 2011, pp. 204–208., doi:10.1016/j.scijus.2011.08.004. Jobling, Mark A., and Peter Gill. “Encoded Evidence: DNA in Forensic Analysis.” Nature Reviews: Genetics, vol. 5, no. 10, Oct. 2004, pp. 739–751., doi:10.1038/nrg1455. Thompson, William C, et al. “How the Probability of a False Positive Affects the Value of DNA Evidence.” Journal of Forensic Sciences, vol. 48, no. 1, Jan. 2003, pp. 1–8., doi:10.1520/jfs2001171.