Cow Maths
“What is dark matter?”
I never imagined myself as the expert in the room that this question would be hurled at. But life is unpredictable and here I am. Poolside for all of 2 minutes, during which I had actually encouraged people to ask me the hard hitting questions. As most tour guides know, hard hitting questions can come in the form of, “I’m seeing tons of stars right now, but why can’t I see the sun?” or they can come in the form of “What is dark matter?” Whenever a customer opens their mouth, you hope for the best. But sometimes, you are sitting on a rock in the pouring rain and have to come up with an intelligent yet simple explanation of dark matter.
How did I get to this rock? I’ll answer that question with another question: How much time do you have? Because if I go back to the very beginning, I believe toast was involved. But I don’t feel like any of us should really dig deep into that.
Currently I find myself working as a stargazing guide. I’m your source of knowledge when it comes to the cosmos if you’re into that sort of thing and in the Aoraki-Mackenzie Dark Sky Reserve. It’s been weeks of studying (looking up Carl Sagan quotes) writing scripts (listening to Carl Sagan’s voice on NPR) and memorizing every detail of the universe (falling in love with Carl Sagan) in case I get asked about dark matter at 12:45 am in the pouring rain.
“What is dark matter?” threw me for a loop but it was, in a sense, answerable. The next hard-hitter from him took loads of research and time on a calculator, not something I knew for sure I was still capable of.
The man that asked me about dark matter was a 70-year-old dairy farmer. In recent years he’s turned his products into organic ones and sells them using reusable packaging. He still delivers his milk door-to-door. The reason for these large scale changes to his farming practices, was to help the environment. But, cows produce methane, a potent greenhouse gas. A thoughtful conversation about climate change and how to respond to the disbelievers ensued. All of this got him wondering about the environmental impacts of the Falcon Heavy launch (think Elon Musk, the reusable rocket, and the roadster hurtling towards mars that you’ve seen pictures of). How does the launch of one of the world’s biggest rockets compare to cows. To be fair, we are all secretly thinking that as we watched the footage of the historic launch.
My farming guest wanted to know, specifically, how many cows does it take to produce the same amount of greenhouse gas that was released during the launch of the Falcon Heavy. I unfortunately could not divert the question or answer it. So I got his email and promised to send an answer his way.
I’m sharing my response because I realized that there is a HUGE INFORMATION GAP on the internet when it comes to comparing cows to rockets.
Things to know before you dive head first into this awesome math:
*I was specifically asked to use the measurement of “cow-days” in these calculations. A cow-day involves the amount of methane produced by a cow in one day, just in case you haven’t come across that one before.
* There are not very specific numbers about some of the information that I was looking up. Be warned. I’m no expert.
Hello There!
Just wanted to say thank you so much for braving that rain to come on the tour. I won’t soon forget the 70-year-old farmer that has out-bungee jumped me! I really enjoyed getting to know you at the pool and trying to answer your tough and thought-provoking questions. Kept me on my toes!
How many cows (or cow-days) equals the launch of the Falcon Heavy rocket? Even with google at my aid, this was not any easy question to answer. I’ll explain the answer I came up with but I’ll include the math so you can redo it or check it. I haven’t had to dust off the calculator in a while so hopefully this answer accurately reflects the question!
The Falcon Heavy used about 80,000 gallons of fuel. About 20,000 gallons of that fuel was used after launch so it didn’t stay within our atmosphere. I included it in the calculations anyway. One gallon of gas puts about 19.6 pounds of CO2 into the atmosphere.
80,000 gallons of fuel X 19.6 lbs = 1,568,000 lbs of CO2 in the air. That equals 711,2333 kgs of CO2 from the Falcon Heavy launch.
If I remember correctly, you are a dairy farmer? I used dairy cows to complete the calculations. Dairy cows release twice as much methane into the air annually compared to beef cows. Dairy cows produce 110 kg of methane a year while beef cows produce 55 kg of methane a year. If you break that down to how much they emit daily (almost exclusively through burping!) it comes down to 0.3 kg a day of CH4 per dairy cow or 0.15 kg a day per beef cow.
Now things are about to get complicated- the Global Warming Potential (GWP) of both CO2 and methane (or CH4) is drastically different. Methane is much worse for the atmosphere than CO2 is. About 30 times worse if you look at the GWPs. So methane heats the planet a lot faster than CO2 does. However, methane, or CH4, is only going to last for about a decade in the atmosphere whereas CO2 can last a hundred, if not more, years after it is produced. So any reduction in methane emissions will decrease its harmful effects on atmospheric concentrations much, much more quickly than the reduction of CO2. Apparently there are things farmers can do to help reduce how much methane their cows are producing! It has to do with diet! I’ll let you look into that if you’re interested.
So now, how many cow-days does it take to equal the greenhouse gas emission of the Falcon Heavy rocket?
Dairy cows produce 0.3 kg of methane a day. I multiplied that by 30 (to equal the GWP of methane with that of CO2) You get cows producing about 9 kg of greenhouse gas (CO2) a day. I divided 711,2333 kg (that which was produced by the Falcon Heavy launch) by 9 kg of CO2 produced by dairy cows each day and came up with a grand total of 79,026 cow-days to equal one Falcon Heavy launch. Or it would take 1 cow about 216 and a half years to equal the launch. However there are about 1.5 billion cows around currently so, if we counted all the cows together, it would take less than a day for the cows and the rocket to equal out as far as producing greenhouse gases go. In fact in one day all the cows in the world could produce as much greenhouse gas as the Falcon Heavy launch about 1,900 times. This isn’t the most accurate number though because not all 1.5 billion cows are dairy cows. If I don’t equal out the GWPs, then it would take 2,370,777 cows to equal one Falcon Heavy launch. (It’s hard to account for the different lengths of times that the two gases stay in the atmosphere, I couldn’t come up with a calculation to figure that disparity out!)
I tried to do the math as accurately as possible but it’s hard to get exact numbers on some of these statistics. If you come up with a different answer I would love to hear how you came about it!
Again thank you so much for reaching out and getting me to brush up on my math skills. Feel free to send any more questions my way!
Thanks so much, Rayna
Before the email was sent and the cow data acquired, the tour was beginning to come to an end. The rain had not let up the entire time the guests were soaking in the hot pools.
“You know, I’m 70 years-old and I went bungee jumping for the first time here in New Zealand. I wasn’t really scared but when I was standing on top of the platform, I looked down and thought to myself ‘What in the hell am I doing?’ When I walked out here tonight in my swimsuit in the pouring rain, I thought the same thing. But I’ve really enjoyed our conversation here this evening.”
Coming away from that soggy tour, I felt the same way: wet and thankful for the absurdity and heart that life has to offer.
