One of the unexpected paths I went down over the course of the last two weeks was to judge the success of a current experiment by smell. A bit over a week ago, I started my bio-cementation experiment using a bacterium that can synthesise urea and calcium ions into calcites – a natural cementation material. It was only today, that I had a first visual confirmation that the process was (probably) working. Up until now I only had smell to go by: the distinct odour of bacteria in growth media, when I opened my moulds in the morning (meaning they were alive and well) was replaced by the smell of ammonia, when I added the chemical ingredients (meaning the biochemical reaction took place exactly as intended).
There are of course assays (methods to quantify a reaction), but they can be a bit of a drag and don’t necessarily capture my imagination. So science by smell works to some extent and having the visual confirmation today was great. We will run the assays eventually, of course, otherwise it wouldn’t be proper science.
The experiment on the left shows the current status: the completely wet sand looks lighter and there is evidence of calcite deposits (light patches) compared to last week (on the right).