# Reinventing Math: turning negatives to positives

Remember those ridiculous word problems in math class that were laughably convoluted and unrealistic? What if we were to inject a bit of reality combined with some consciousness-raising into word problems. We could get kids motivated to solve real world problems and oh, by the way, learn a little math in the process. Here are some possible word problem examples (which of course involve biochar!) based on a recent New York Times article about air pollution in India.

India produces 34 M tons of crop residues, mostly rice and wheat straw.   Although illegal, most farmers burn the straw as this is the quickest way to clear fields for the next crop. Instead of burning, which contributes significantly to air pollution, farmers could carbonize these residues, creating a valuable nutrient carrier, biochar, which can also sequester carbon in the soil.  Solve the following problems:

1. 800 liters of straw will yield 200 liters of biochar.  What is the yield as a percent?
2. If all farmers in India produced biochar instead of burning crop residues, how many tons of biochar could be produced?
3. If straw char contains 36% carbon, how many tons of carbon could India create from crop residues per year?
4. A typical car emits 4.7 metric tons of greenhouse gases per year.  What is the equivalent in the number of cars, to the amount of carbon which India could create if all crop residues were carbonized?
5. A small farmer with 1 hectare is fined USD\$38 for burning his crops.  Crop residues per hectare vary from .4 tons – 3.0 tons depending on many factors.  Assume Farmer A has 2 tons of crop residues and that one laborer who is paid \$8 per day can harvest and carbonize 800 kg of straw in one day. Will the farmer be better off burning his crops or carbonizing them?
6. How much biochar will Farmer A produce?
7. For every kilo of biochar produced, assume the farmer can reduce purchases of lime for his fields. (Lime is needed for fields that are acidic.) Lime costs \$30 per ton. How much will the farmer save assuming a 1:1 ratio for biochar:lime.
8. What is the effective cost of producing biochar when labor and savings in lime are included?

The list of word problems could go on and on just for this single scenario.  The questions could even get more complicated for older students, but you get the general idea. Math word problems could be customized for different regions or for different problems which resonate with different cultures around the world.

Maybe, just maybe, if we create a math curriculum focused on climate change solving math word problems, we could start turning negatives into positives….in more ways than one!  Kids could educate their parents on this new math, offering new solutions which will not only reduce air pollution and rebalance carbon levels but could also improve farmer livelihoods too!