Ms.Gutberlet ,We can to some extent reduce the human  interference in nitrogen and phosphorus cycles by recover,recycle and reuse approach in agriculture. It is not sufficient simply to collect and compost the urban household waste and use the same compost in agriculture.The small quantity generated can be used in urban and peri-agriculture.Vegetable and flower waste,and prunnigs from trees in urban areas can be collected and composted.To substantially reduce the fertilizer N and P requirement we have to compost the dung of animals and bedding( straw material )in dairy farm and farm waste with dung and straw mulching  in fields .We should think in terms of recovery and use of N and P in human urine and excreta. Agroindustry processing waste can also be composted and used.To increase the value of compost it can be fortified with inorganic fertilizers,minerals or byproduct sources like rock phosphate,mica waste,gypsum etc and also microbial cultures/biofertilizers.

I endorse Subba's response.  If we do not recycle nutrients from human excreta we are failing.  However the risk of recycling undesireable contaminants is also considerable 

I agree with both answers above.  I believe that in many industrialized countries municipal waste is already being recycled into crop production (after standard sewage treatment).  In Ontario (where I live) recycling bio-solids in to crop land as fertilizer is being regulated by the Government. As an example, please see in the link below:

http://www.omafra.gov.on.ca/english/nm/nasm/info/brochure.htm

When any type of organic source (bio solids and livestock manure) is used as fertilizer, farmers are advised to perform soil testing before supplemental inorganic fertilizer are applied.  In this way we can make sure we do not over-apply N and P to the same land.

I am sure we are avoiding the need for significant quantity of inorganic N and P fertilizer, by using these bio-solids as fertilizer.

 Now P is being recovered as Magnesium ammonium phosphate   from urine /sewage water in Japan and some European countries.Necessary formalities are being being followed to declare it as fertilizer.At least some small quantities are being marketed.

Thank you for all of your valuable responses which confirm my own understanding of the importance and gains from recovering organic waste. Of course, it is not enough to just recover the organic part of household waste. You are right that wastes produced by humans need to be tackled (reduced or recycled). My research is primarily on resource recovery in developing countries. Unfortunately in many countries in the global south most of the organic household waste is still landfilled. However, change is coming. It is becoming very expensive for governments to maintain landfills and there is more interest in different forms of waste recovery. Here, collecting organic waste for compost or energy production creates many jobs, which is yet another concern in these economies.

My overall concerns are embedded in global environmental concerns. Reducing human interferences in the global phosphor and nitrogen cycle are key challenges. So it is correct to say that organic household waste recovery makes a small contribution to that reduction.