Even where sewage treatment systems are widespread, human waste still represents a significant environmental threat. Primary and secondary treatment of sewage often fails to treat industrial pollutants or to prevent nitrate and phosphate rich effluent reaching water bodies and causing eutrophication. The dehydrated sludge that results from such processes contains a wide range of toxic materials including heavy metals, organochlorine oestrogen mimickers, radioactive material from hospitals, and phenols

sewage sludge has little nutrient value as most of the nitrogen is lost during sewage treatment and disposed along with the wastewater. By contrast, heavy metal concentrations are very high and sewage sludge also contains complex mixtures of chemicals which have
much greater potential to cause environmental health problems than when present in isolation. But alternative sewage treatment methods are very expensive. A 2001 estimate of the cost of achieving full compliance for sewage in the EU by 2010 was $150e215 billion, while
in the USA, pollution control between 2001 and 2021 is likely to cost $325 billion, with $200 billion for treating sanitary overflows

Are local taboos surrounding excreta change a resource rather than a threat

Sewage as agricultural fertiliser on and off in European history

England- efforts to transform 'filth into food', carting sewage from urban to rural areas to be used as an agricultural fertiliser

However competition made animal manure a more viable option

The adoption of on-site ‘composting’ or ‘ecological sanitation’
(ecosan) systems in different geographical contexts indicates how
positive associations between sanitation and fertilizer production
or income generation can sometimes promote quite significant
changes in attitudes towards (and practices surrounding) human
excreta. In Sweden, for example, composting toilets have become
quite popular as sanitation and waste management systems in
holiday cottages, despite their users being accustomed to conventional ‘flush and discharge’ systems in their main homes

Ecosan systems being developed in the global south to provide sanitation and income generating opportunities. Environmentally or economically appropriate sanitation as it requires neither water for flushing drains nor drains for excrement removal . Remove the need for water collection associated with pour flush toilets

ecosan systems that divert urine provide an important source of free fertilizer as the 4-500 L of urine that each adult produces annually “contains enough plant nutrients to grow 250 kg of grain, enough to feed one person for one year”

the extent to which this is considered acceptable
varies greatly from place to place and between ethnic, socioeconomic and cultural groups: a situation that limits the widespread adoption of ecosan systems where preferences for ‘flush and discharge’ systems are pronounced

biogas digesters are widely used for energy production in many parts of the global South world with China having been a leader in the field since the late nineteenth century

Bio gas methane has a wide variety of uses including the provision of cooking and heating gas, electricity, vehicle fuel when processed and introduced into natural gas pipelines

When combined with China’s annual production of night soil, this ‘waste’ could theoretically generate 130 billion m3 of methane (equivalent to 93 million tonnes of coal) as well as reducing the proportion of waste going to landfill

greenhouse gas emissions from biogas
production are lower than for many competing fuels

the biogas used to fuel vehicles produces 95% less CO2 and 80% less nitrous oxide than diesel as well as having no particulate emissions and there is enough of it available to fuel half the UK’s HGV fleet.

Nepal’s national biogas program supported the construction of 200,000 plants between 1992 and 2009 while Vietnam’s national program promoted the construction of 26,000 plants between 2003 and 2006

Despite the many inter-linkages between excreta, environmental quality and human health plus the fascinating ambiguities and variations over time and space in socio-cultural attitudes towards it, human waste rarely forms a central part of geographical analysis or academic research more generally

Wider taboos associated with human waste often render them culturally unacceptable- ecosan and anaerobic digestion

Social conceptualisations of disgust vary enormously between different places and cultures are rarely static

there is an urgent need to understand how local socio-cultural norms surrounding human excreta interact with
wider political, physical and environmental constraints if appropriate and sustainable excreta management systems are to be developed for over 2.6 billion people

translating such research into policy can be an uphill struggle given the low priority given to sanitation in much of the global South and a general lack of awareness among policy-makers about alternative sanitation systems such as ecosan.