Influence of changing drivers on realising the value of sewage sludge as a resource

Sewage sludge production is rising around the world. This is due to population growth, stricter legislation, and – especially in Far East Asia – investment in wastewater infrastructure. Whilst, it is typically considered a nuisance, sludge has numerous benefits which can be exploited, such as the reuse of nutrients or extraction of energy. Previously in Europe, reluctance for land recycling of sludge coupled with cheap energy led to the development of sludge treatment strategies which were heavily reliant on energy intensive processing such as drying. However, increasing energy costs, mounting importance of nutrient (especially phosphorous) recovery and growing influences of sustainability and carbon footprint reduction drivers have led to the development of new sludge treatment strategies. This paper highlights a number of case studies where this has been the case, and also discusses the value of sewage sludge, how this value can be optimised and what the potential barriers are.