Energy demand for phosphorus recovery from municipal wastewater

• Phosphorus (P) is one of the essential nutrients for production of food. In modern agriculture, a large part of P comes from finite sources. There are several suggested processes for reuse of P from wastewater. In this paper, the energy use of direct reuse of sludge in agriculture is compared to the energy demand connected to use of mineral P and to reuse of P after thermal processing of sludge. The study is based on literature data from life cycle analysis (LCA). In the case of direct sludge reuse the sludge stabilization processes applied and the system boundaries of the LCA has a large impact on the calculated energy demand. The results though indicate that direct reuse of sludge in agriculture is the reuse scenario that potentially has the lowest energy demand (3-71 kWh/kg P), compared to incineration and extraction of P from sludge ashes (45-70 kWh/kg P) or pyrolysis of sludge (46-235 kWh/kg P). The competitiveness compared to mineral P (-4-22 kWh/kg P) depends on the mineral P source and production. For thermal processing, the energy demand derives mainly from energy needed to dry sludge and supplement fuel used during sludge incineration together with chemicals required to extract P. Local conditions, such as available waste heat for drying, can make one of these scenarios preferable. 

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Miljöbioteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Environmental Biotechnology (hsv//eng)

Nyckelord

Combustion

Incineration

Nutrient reuse

Pyrolysis

Wastewater sludge

Agriculture

Energy management

Heat treatment

Life cycle

Minerals

Nutrients

Phosphorus

Waste heat

Waste incineration

Essential nutrients

Life cycle analysis

Local conditions

Modern agricultures

Municipal wastewaters

Phosphorus recovery

Sludge stabilization

Wastewater reclamation

Biotechnology/Chemical Engineering

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