Did you know? Part 5.

A friend of mine asked me this question: "“how many days of US energy consumption could we replace if we liposuctioned all body-fat over 10% for men and 18% from women in the US?" I'm sure you've all been asking yourself the same question so here's my attempt at an answer. This article says that “By 2002, average weight for men was almost 191 pounds; for women, average weight was 163 pounds”. And this page says that “The average adult body fat is closer to 15%-18% for men and 22%-25% for women”. So let’s assume 16.5% for men and 23.5% for women. That would mean the average man is 31.5 pounds of fat and 159.5 pounds of muscle; 38.3 pounds of fat and 124.7 pounds of muscle for women. So, if men got down to 10% body fat, they’d keep their 159.5 pounds of muscle but only have 17.7 pounds of fat (a reduction of 13.8 pounds of fat). For women, to get to 18% body fat, they’d keep their 124.7 pounds of muscle and have only 27.4 pounds of fat (a 10.9 pound reduction). According to Wikipedia, there are 105.74 million adult men and 112.81 million adult women in the US. So, if each one of those men had 13.8 pounds of fat liposuctioned out and each woman had 10.9 pounds removed, that would be a total of 2,688.84 million pounds of liposuction fat. Per the numbers in my earlier post, the density of liposuction fat is 7.66 pounds per gallon. So 2,688.84 pounds of fat would be 351.02 million gallons. One gallon of fat yields 0.867 gallons of biodiesel. So 351.02 million gallons of fat would become 304.22 million gallons of biodiesel. Biodiesel has about 10% less energy content than regular diesel so 304.22 million gallons of biodiesel would offset the use of 273.8 million gallons of diesel. And, according to EIA, the US uses 64 billion gallons of diesel per year. So 273.8 million gallons would be 0.428% of that or about 1.56 days or about 37.5 hours. Now, note that diesel usage accounts for only 20.4% of overall petroleum usage in the US. And petroleum only accounts for 39.8% of overall energy consumption in the US (source). So, the real answer to your this question is 0.127 days or about 3 hours. Not much of a renewable energy source. The more interesting question from my perspective is "if people in the US consumed less food such that they were at their ideal weight and body fat percentage, how much energy would be saved in terms of farming, packaging, transportation, preparation, etc and how much biofuel could be generated from the equivalent amount of farm land without triggering all these food vs fuel debates?" Don't have time to try to figure that one out but perhaps someone else can take up the challenge. =)