Human urine can now be used to reduce pollution by absorbing greenhouse gases, especially carbon dioxide. Researcher Manuel Jimenez Aguilar of the Institute of Agricultural and Fisheries Research and Training of the regional government of Andalusia observed that absorbing large quantities of carbon dioxide and other greenhouse gases present in cities would require millions of tonnes of some naturally occurring substance. The ocean, the ground, rocks and trees act as carbon drains but are far from places where greenhouses gases are concentrated, so urine can be used as a reactive. To avoid the urine from decomposing, the researcher suggested the possibility of including a small proportion of olive waste water (a black, foul-smelling liquid obtained from spinning the ground olive paste).