AskPablo: Cold Storage

freezer.jpgAccording to Supercomputing Online ” in 2005, total data center electricity consumption in the U.S., including servers, cooling and auxiliary equipment, was approximately 45 billion kWh, resulting in total utility bills amounting to $2.7 billion.” The average emissions per MWh in the US are 0.61 metric tons (mT), so US data center electricity use amounts to 27.45 million tons of CO2 emissions annually. With 200,000,000 internet users in the US (2005), that is 137 mT for each one of us. But this is a whole other topic…

This week’s topic comes to us from Rolf Muller, Ph.D. who is the Founder and Chief Scientific Officer of Biomatrica Inc. Rolf pointed out to me in a recent conversation that there is another type of storage that uses massive amount of energy, cold storage of tissue and DNA samples. Apparently this cold storage occurs in massive “refrigerator farms,” much like the server farms that Google and Yahoo operate. Like data storage, cold storage is experiencing rapid growth. But unlike large-scale data storage, cold storage has not received much press, and refrigerator companies don’t seem to be working on anything similar to Sun Microsystem’s Eco-Responsibility Initiative. Rolf asked me to explore just how massive the energy use by tissue sample storage is. To do this he provided me with some data on the market as well as some assumptions.
According to a RAND study by Elisa Eiseman and Jasen J. Castillo “307 million specimens from more than 178 million cases are stored in the United States, accumulating at a rate of more than 20 million per year.” 50% of global tissue storage is in the US. Rolf estimates that there are 467,500 labs worldwide that use cold storage. On average they have one -80 freezer, two -20 freezers, and three refrigerators. Each lab also receives delivery of two 100-liter liquid nitrogen tanks every month. I’ll go through these one-by-one to find the total global energy used for cold storage of tissue samples and the corresponding GHG emissions.
A -80 freezer uses 21 kWh per day, or 7665 kWh per year. If there are roughly 467,500 of them, this adds up to 3,853,387,500 kWh, or 3.85 million MWh per year.
A -20 freezer uses 14 kWh per day, or 5110 kWh per year. If there are roughly 935,000 of them, this adds up to 4,777,850,000 kWh, or 4.78 million MWh per year.
A lab refrigerator uses 9 kWh per day, or 3285 kWh per year. If there are about 1,400,000 of them, this adds up to 4,599,000,000 kWh, or 4.6 million MWh per year.
The total energy used for these freezers and refrigerators is 13.2 million MWh per year (compared to 45 million MWh for data storage in the US)! This energy use is responsible for 8,052,000 mT of CO2 released by power plants each year.
The liquid nitrogen tanks add even more to this. 200 liters per lab, per month, equals 2400 liters per lab per year. With 467,500 labs globally, this amounts to 1,122,000,000 liters per year. The density of liquid nitrogen at -320F, 1 atmosphere is 0.808 kg/liter, so this can be converted to 906,576,000 kg of liquid nitrogen. According to the Wuppertal Institute’s MIPS data tables liquid nitrogen cause 0.441 kg of GHG to be release per kg produced. So 400,000 mT of CO2 are released in the manufacture of the liquid nitrogen used by these labs.
This brings the total carbon footprint of global tissue sample storage to 8,452,000 mT. If you are a tissue lab owner and are feeling guilty remember that this amount can be offset for around $63,390,000, or roughly $136 for the average lab. Keep in mind that, while this is for the average lab, some are much, much bigger.
Pablo Päster
Sustainability Engineer
Next week Hoff Stauffer will be answering questions about global climate change and what we, as a global community, can do about it. Please submit your burning questions to pablo.paster(at) or in the AskPablo comment section.
Hoff, who has done research and consulting on energy and environmental issues for many years and was the first Director of Economic Analysis at the US EPA, is focusing on Global Warming. Since the science is clear, he believes: “The debate in the United States on global climate change is shifting from whether to do something about the problem to what to do.” But he is concerned that inflexible conventional wisdom and misperceptions are inhibiting progress. “Given the irreconcilable problems with cap and trade, we need to transcend the conventional wisdom and shift the debate to a more viable strategy….[that] relies on performance standards for new sources of GHG emissions.” “The notion that ‘draconian measures’ would be required [to mitigate global warming] is an unfortunate misperception that has inhibited meaningful action.” See some of his recent articles in Foreign Policy in Focus: A New Standard, Climate Change: Is It Prudent to Wait?, and Climate Change Roundtable.

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