"Prickly paddy melon weed enzymes show potential as sustainable cement alternative." "An invasive weed that has long plagued the Australian agricultural industry could become a game-changing economic crop due to its potential to produce a cement alternative. Prickly paddy melon costs the agricultural industry around $100 million a year in lost grain yields, cattle deaths and control measures."
"But now researchers say enzymes produced by the paddy melon could be used to create a more sustainable form of cement and prevent soil erosion."
It took me a while to figure out what this was about. What it's about is a type of enzymes called urease enzymes. The reaction urease enzymes catalyze is urea + water = ammonia + carbon dioxide. What this has to do with concrete is there's this concept in concrete of "self healing" concrete, which works (to a limited extent) by having enzymes in the concrete that, when combined with water, precipitate calcium carbonate. Astute observers amoung you will at this point point out that calcium carbonate is not part of the chemical reaction that urease enzymes catalyze. Obviously you also need calcium present to precipitate calcium carbonate, but the real key is that the ph level is changed (more specifically increased, more specifically by the ammonia) such that dissolved calcium ions in the concrete will react with the carbon dioxide to precipitate calcium carbonate.
For those of you who like chemical formulas (helps me understand what's going on but I hear some people are scared off by formulas) , the reaction that the urease enzymes catalyze is:
(NH2)2CO + H2O -> 2NH3 + CO2
(that is, two of the (NH2) groups -- the lack of subscripts can be confusing).
And the formula for calcium carbonate is CaCO3.
What does all this have to do with the Australian weed prickly paddy melon? Apparently it's possible to produce these urease enzymes in massive quantities by extracting them from this plant.
I was disappointed by this as we humans consume crazy amounts of sand and are depleting the planet of sand for use in concrete, and I was hoping this would help with that. But no. In fact if you chase down the actual research paper (or the abstract, the full paper is paywalled), you'll find the researchers were primarily interested in urease enzymes for soil. Since ammonia increases pH, if a soil is acidic (remember, pH numbers under 7.0 are acidic, the lower the more acidic, while pH numbers above 7.0 are basic/alkaline, the higher the more basic/alkaline), adding these enzymes can reduce the acidity. Since ammonia is a nitrogen compound, it also helps to make nitrogen available for crops.
So, this won't help with concrete production from sand, and the article doesn't even try but instead talks about carbon footprint. Might be useful for limited "self-healing" concrete, and probably most useful for agricultural crop soil.
Prickly paddy melon weed enzymes show potential as sustainable cement alternative
