Pissing in the Wind: Stupid Idea of the Week

Spanish scientists propose to use urea to absorb CO2 from power plants:

Absorbing the large quantities of carbon dioxide and other greenhouse gases present in cities would require millions of tonnes of some naturally occurring substance. A study published in the Journal of Hazardous Materials suggests urine as a reactive. As a resource available across all human societies, it is produced in large quantities and is close to the pollution hubs of large cities.

“For every molecule of urea in urine, one mole (a chemical unit used to measure the quantity of a substance) of ammonium bicarbonate is produced along with one mole of ammonia, which could be used to absorb one mole of atmospheric CO2,” as explained to SINC by the author of the study, Manuel Jiménez Aguilar of the Institute of Agricultural and Fisheries Research and Training of the Regional Government of Andalusia.

After absorbing the CO2 another unit of ammonium bicarbonate is produced, which is used in China as a nitrogen fertilizer for 30 years. Jiménez Aguilar points out that “if applied to basic-calcium rich soils this would produce calcium carbonate thus encouraging gas-fixation in the ground.

To avoid the urine from decomposing, the researcher suggests the possibility of including a small proportion of olive waste water (a black, foul-smelling liquid obtained from spinning the ground olive paste). This acts as a preservative. The researcher confirms that “the urine-CO2-olive waste water could be considered an NPK fertilizer (ammonia-nitrate-phosphorous-potassium).”

In the US CO2 annual production is estimated at about 5.5 metric tonnes per capita, or 5,500 kg.  On the other hand, urine production is estimated to be about 2.5 L/day, or 912 Liters per year, with a liter of urine having about 9.3 g of urea, for a total of about 8.5 kg of urea per annum. So, at best, if we captured every drop of piss, we could capture about 0.1% of CO2 emitted by the US.  Truly a drop in the bucket. And is there enough olive waste water to serve the job?  That's a lot of urine to stabilize.

Then, we would be left with ammonium bicarbonate, which would either need to be stored indefinitely (like power plants need another waste product) or used a fertilizer (which is just another environmental problem we are trying to ameliorate).