Global Water Intelligence| Beating the Burn Rate for Resource and Energy Recovery from Sludge

Feb 20, 2017

Traditional methods of managing sludge as a waste product are being challenged by technologies carrying the promise of sludge as a resource for energy and nutrients. What is fuelling the interest?

January 2017 – Read original article

It has long been known that sludge is full of valuable commodities and energy potential, however the economics of realizing these benefits has rarely added up. Recovery of biogas for energy generation is the notable exception, while recovery of phosphorus from both wet and dry sludge is an area where the economics are at a tipping point. This may be just the beginning: there is growing interest in turning sludge into a renewable energy source such as renewable natural gas, low-sulphur diesel, biocrude oil, or biocoal (an alternative to fossil coal), through modifications to thermal reduction processes traditionally employed on solid wastes (see chart left). Technologies specifically designed for wet wastes such as hydrothermal processing are also emerging. The interest “began to occur about ten years ago when the price of oil soared above $100 a barrel”, according to Joe Zuback, president of consultancy Global Water Advisors. There is also growing interest from utilities to enhance their sustainability agenda.

Currently, the single most useful and valuable product to come from treating sludge is biogas, which is produced through a treatment process that has been employed at municipal wastewater treatment plants (WWTPs) for several decades – anaerobic digestion (AD). The most common form of recovering energy from sludge is converting the biogas into electricity to power other processes at a treatment facility in order to reduce the plant’s energy footprint. The process can be tweaked and advanced in several ways to recover more biogas, notably with the inclusion of a thermal hydrolysis pretreatment step. Enhancing the AD process will be the subject of a later GWI Market Map.

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