Renewable energy

Engineering

Economics

Sewage treatment

Business

Wastewater

Energy carrier

Nexus (standard)

Water-energy nexus

Electrical engineering

Effluent

Sanitation

Environmental science

Embedded system

Natural resource economics

Zero-energy building

Zero waste

Waste management

Biogas

Environmental engineering

npj Clean Water

The energy-consuming and carbon-intensive wastewater treatment plants could become significant energy producers and recycled organic and metallic material generators, thereby contributing to broad sustainable development goals, the circular economy, and the water-energy-sanitation-food-carbon nexus. This review provides an overview of the waste(water)-based energy-extracting technologies, their engineering performance, techno-economic feasibility, and environmental benefits. Here, we propose four crucial strategies to achieve net-zero carbon along with energy sufficiency in the water sector, including (1) improvement in process energy efficiency; (2) maximizing on-site renewable capacities and biogas upgrading; (3) harvesting energy from treated effluent; (4) a new paradigm for decentralized water-energy supply units.

Pathways to a net-zero-carbon water sector through energy-extracting wastewater technologies