The developing value of sewage sludge and how to exploit it

Nair, A. and Palmer, S.J., MWH (UK) Ltd, UK



From now, over forty year average asset life of a typical wastewater treatment facility to 2050,  our water industry faces a period in which there will be sustained upward pressure on most of its operating costs (including electricity, fuel, chemicals and even salaries), resulting from long term global demographic and macroeconomic trends.  In the U.K. these price risks will translate into increased costs for customers and suppliers of water and wastewater treatment, through any temptation of privatised utilities to hedge against reduced margin and shareholder returns for water and wastewater treatment.

The recent reviews of competition within the water industry, including competition for sewage sludge processing and disposal by the LSE (2010) and OFT (2011) commissioned by OFWAT do not take full account of these factors- but should. Sewage sludge provides water and sewage treatment utilities with a resource that will allow them to hedge against operating cost risk rather than pass increased operating cost onto their customer base.

The alternative to continued vulnerability to operating cost increases for the water industry is to invest in wastewater treatment that provides for resource recovery, as renewable energy and material resources that command a profitable market value.

This approach allows the water industry to better control its operating costs in future through reducing energy costs and using any revenue stream from recovered materials to offset operating costs. This paper demonstrates that the principal indigenous resource for energy and material resource recovery is sewage sludge. We describe the combination of technologies currently operating at full scale that can provide maximum renewable energy recovery and facilitate material resource recovery. The first material for which recovery is likely to be the subject of future legislation is identified (Phosphorus) and its potential future value is projected.

Key words:

Renewable energy recovery, sewage sludge value, carbon footprint , OFWAT sludge service competition review, increased customer billing risk, reducing operating costs, strategic resources, climate change and economics.


The U.K. water industry is now beginning to experience the effects of global macroeconomic trends that will increase its operating costs for a prolonged period, from now to 2050. The risks that are now rendering our current business-as-usual approach to wastewater and sludge treatment asset design redundant include:

Increased operating costs; arising principally from energy cost risk but exacerbated by amount of electricity consumed by conventional modern wastewater treatment

Climate change and the need for the water industry to reduce Greenhouse gas (GHG) emissions (carbon footprint) now becoming the subject of legislation and regulation (especially in the UK.)

Global pressures such as population increasing by 50% by 2050 (6) placing a huge burden on agriculture, to increase its production by 70% by 2050.

The food issue presents one example of how these global factors are interlinked and how complex the various feedbacks associated with it are. Significant Global increases in food production needed to ward off large increases in starvation; especially as the 50% increase in global population originally expected by 2050 may now be an underestimate of global population. Efforts to increase food production to the required level rely on intensive agricultural but are undermined even at this stage by the global demand for energy stimulating competition for agricultural land use for food with biofuels which in turn increases upward pressures on food prices.

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