WOW! What a hard question! First, if soybean to water ratio is 1:1, soybean to water to wheat ratio is 3:3:2. If salt is 18%, 82% is in the 3:3:2 ratio. We are lucky that 3+3+2 is 8, and 82 is close to 80. 80/8 = 10 so the 3:3:2 ratio would be 3/10 of bottle: 3/10 of bottle : 2/10 of bottle. If we put the 18% of salt (let's round to 20%) at the end of the ratio, the ratio would be 3/10 of bottle: 3/10 of bottle : 2/10 of bottle : 2/10 of bottle. It is represented in a cleaner way below.
Soybeans : Water : Wheat : Salt 30% : 30% : 20% : 20% Now, let's focus on the soybeans. One liter of soybeans is about 1/35th of a bushel. 300 ml of soybeans, the amount in a one liter bottle, is 3/350 of a bushel. This is also 0.86% of a bushel. The amount of greenhouse gases that it takes to produce one bushel of soybeans is 6.5 pounds (In 2011). 0.86% of that is 0.05571428 pounds of GHGs. (Lets just say 0.056 pounds) Then there is the wheat. Since one bushel of wheat weighs 60 pounds, just like soybeans. That means that one liter of wheat is 1/35 of of a bushel. 200 ml of wheat, the amount in a bottle of soy sauce, is 1/175 of a bushel. 12 pounds of greenhouse gases are emitted per bushel of wheat made. If that is multiplied by 1/175, we get 0.068571428 pounds of GHGs. (Let's just say 0.069 pounds) Water has a small carbon footprint because it doesn't need as much care as a plant. It is 4.1 metric tons per million gallons. This means that 0.0000041 metric tons per gallon. Metric tons of greenhouse gases per milliliter would be 1.08310593e-9 per milliliter. The GHG emissions for a liter of soy sauce, 300ml, would be 3.24931779e-7 metric tons. The last step is to convert 3.24931779e-7 metric tons. With a calculator, we can find out that 3.24931779e-7 metric tons is approximately 0.00072 pounds. Salt has a surprisingly high carbon footprint. It is 1 tonne (metric ton) of carbon dioxide for every 4 tonnes of salt used. The ratio is clearly 1:4, so that means that if I used one gram of salt in my lunch of tomato soup, the carbon dioxide emissions for only the salt would be 1/4 gram! In one liter of soy sauce, there is approximately 200 ml of salt the carbon dioxide emissions from that is approximately 50 ml. When we convert that to pounds, 50 ml turns out to be 0.1102 pounds. |
After all the carbon footprints of ingredients own paths to the soy sauce factory, we need to add them up. 0.056 pounds + 0.069 pounds + 0.00072 pounds + 0.1102 pounds = 0.23592 pounds. Are we done calculating? No, we are not.
At the factory, there are emissions too! for these last few calculations, we will use Kikkoman soy sauce factories. First, all of Kikkoman's factories produce 146669 tons of CO2 per year, for all of their seven factories. That means about 20952 tons for one year and factory. It also means 57 tons a day. We can convert that to 51699 liters of CO2 a day for efficiency. Next, all Kikkoman factories produce 400 million liters of soy sauce in a year. That is approximately 57142857 liters for one factory in a year. To get down to liters of soy sauce in one day, we divide 57142857 by 365 to get about 156555 liters of soy sauce produced in a day at one Kikkoman factory. Now, if they emit 51699 liters of CO2 in a day, and they make 156555 liters of soy sauce a day, we can divide those to get (drum roll please)... 51699 / 156555 = approximately 0.33 liters of CO2 per 1 liter of soy sauce The final step is to add the factory emissions to the farming emissions. 0.33 liters + 0.23592 pounds = 0.33 liters + 0.107 liters = 0.3407 liters of CO2 for 1 liter of soy sauce. |