Addy asked in Science & MathematicsChemistry · 8 months ago

Does adding lime juice lower the pH level of a compost?

I am doing a science fair experiment where we add actual lime juice to compost and see if the pH level lowers because it is acidic. It is hard to research because whenever I search up lime and it's relation to compost or soil, it thinks I'm talking about the limestone powder called "lime" as well. So my final question is if I added lime (the fruit) juice to a compost, will it lower the pH level because it is acidic? Thank you!

2 Answers

  • 8 months ago

    lime juice is acidic (citric acid), so it will likely decrease pH if added. It is possible, on paper at least, that the pH of the compost is so low that the lime juice can't make it go lower (pure citric acid is about pH=3: citric acid is a weak acid). The amount of lime juice that gets added will affect how acidic the compost/lime juice mix would be, of course.

    lime the chemical, refers to calcium hydroxide or oxide (lime or quicklime), which are bases and will raise pH.

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  • 8 months ago

    Compost ....

    You would need a lot of limes, the fruit, to lower the pH of a pile of compost.  Just toss in some old oranges or limes or whatever.

    Limestone is calcium carbonate, and adding it to compost will raise the pH, that is, make it it less acidic.

    CaCO3(s) + H2O --> Ca2+ + HCO3^- + OH-

    Lime is calcium oxide, and it too, will raise the pH of the compost.

    CaO(s) + H2O --> Ca2+ + 2OH-

    So, what is the point of the project?  To see if different pH's affect the compost in some way, or to simply see if citric acid lowers the pH (it does).  It seems to me that this project needs some more thought.

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