Friday, 18 January 2008
EcoSan in periurban areas?
The Stockholm Environment Institute (a very well regarded institute), in its 2005 report Sustainable pathways to attain the Millennium Development Goals − Assessing the role of water, energy and sanitation (Table 4-5, p. 50), reports extraordinarily high costs for urban EcoSan systems (in contrast rural EcoSan costs seem affordable). They range from USD 350 per household in sub-Saharan Africa to USD 1200 per household in West Asia. Without subsidies, who’s likely to be able to afford these costs? Not the periurban poor, that’s for sure. In the paper EU demonstration project for separate discharge and treatment of urine, faeces and greywater – Part II: Cost comparison of different sanitation systems (Water Science and Technology, 2007), basically a cost comparison between urban EcoSan and conventional sewerage, German EcoSan researchers reported that “the multiple sewer systems resulting from the separation of urine, brown [and] greywater are responsible for higher investment costs”. So urban EcoSan costs more than conventional sewerage, at least in this demonstration project in Germany. Personally I can’t imagine it would be much different in developing countries. Multiple sewer systems? Three actually: one for ‘yellow water’ (urine), one for ‘brown water’ (faeces + flush water), and one for ‘greywater’ (all non-toilet wastewater). No wonder it’s more expensive! In developing countries we know that simplified sewerage is much cheaper than conventional sewerage, so it has to be a whole lot cheaper than urban EcoSan with its multiple sewers. In any case simplified sewerage + treatment in waste stabilization ponds (including biogas recovery from anaerobic ponds) + effluent use in aquaculture and/or agriculture is as ‘ecological’ as EcoSan. My view is we should only consider EcoSan in rural areas − horses for courses!