Phosphorus (P) is one of the three major plant nutrients but it is the scarcest on the planet; at the current rate of exploitation, today's resources will be exhausted in about 70 years; 80% of the extracted P is used as fertiliser. Additional reserves might last another 200 years; when they are exhausted, crop yields will decline rapidly. All living cells require P; it cannot be substituted, unlike fossil fuel. The world's human population was 1bn in 1800, 1.6bn in 1900, today it is 6bn, by 2050 it will be 9bn and is then predicted to stabilise at about that number. For the first time in history more people now live in towns than in the countryside. Food, with its embodied phosphorus flows from farms to towns. Adults excrete 98% of the P in their diets because they are turning over cells rather than increasing their number. This excreted P and other P ends up in municipal wastewater and is concentrated in biosolids; the amount that escapes in effluent (where it can cause eutrophication) depends on the wastewater treatment. This paper will discuss the dynamics of P, the options for capturing P and the CSR (corporate social responsibility] imperative of not impeding this vital resource conservation.