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Hydrogen to Convert Sewage into Fertiliser in New Zealand

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Because hydrogen produces only water when burned, it is regarded as a potentially game-changing fuel for the clean energy transition. When combined with emerging technologies such as fuel cells, hydrogen is clean, efficient, and energy-dense enough to replace traditional liquid fuels such as gasoline and diesel.

Consequently, the search is on for cheaper and cleaner ways to produce hydrogen and water treatment is a potential source of green hydrogen that is attracting growing interest. Excitingly, New Zealand has invented a multi million-dollar machine that will turn New Plymouth’s sewage into fertiliser which is set to be powered by hydrogen.

New Plymouth District in north Taranaki is one of three districts in the region and home of the region’s largest city. The strategic priorities of the New Plymouth NPDC centre on creating a lifestyle capital through an approach that prioritises people, place and prosperity.

The $37 million project to upgrade the thermal dryer at the New Plymouth District Council Wastewater Treatment Plant is expected to take two and a half to three years to complete, councillors were told last week during a strategic projects committee meeting.

Infrastructure Minister announced the hi-tech investment this morning which will see New Plymouth-based energy supply hydrogen, so the thermal dryer runs on a hydrogen/natural gas blend, servicing some 27,000 properties across the district. The new thermal dryer will significantly reduce the carbon footprint of running the facility by between 25% to 40%, cutting emissions.

Currently, sewage is pumped in and goes through several steps before the solid matter is separated out to the thermal dryer, which dries it out for use as fertiliser. The remaining treated liquid is then discharged into the sea, but with an electrolyser, it could be used to produce hydrogen, a cleaner fuel, by separating it from its oxygen components.

Hydrogen could be blended into existing natural gas networks, with the greatest potential in multifamily and commercial buildings, particularly in densely populated areas, while longer-term prospects could include direct hydrogen use in hydrogen boilers or fuel cells.

When hydrogen is produced using renewable electricity, it has a high potential for medium- to long-term energy storage. This green hydrogen can then be captured, stored, and used to generate electricity as needed in a fuel. Moreover, hydrogen can be used as a vehicle fuel. Hydrogen-powered vehicles have a range comparable to current petrol or diesel-powered vehicles and can be refuelled quickly, allowing for efficient fleet optimisation.

Contracts for much of this project are already in place, and a contractor has prioritised Taranaki and then New Zealand-based supply chains over its usual international channels. The total cost of the project, which includes addressing earthquake-prone buildings, employee welfare, and expanding the compliance testing laboratory, is estimated to be $43 million, with a $6 million contingency fund. However, the latest decision by the government indicates that the project can now proceed sooner, without costing ratepayers.

The wastewater treatment facility treats between 7.9 and 10.8 million cubic metres of wastewater per year and produces approximately 1,600t of organic fertiliser. New Plymouth is the only council that produces and sells fertiliser as a by-product of wastewater treatment, preventing sludge from being disposed of in landfills, protecting its beautiful natural environment, and generating revenue from what would otherwise be a cost.

In contrast, hydrogen is already widely used in some industries, but its potential to support clean energy transitions has yet to be realised. To overcome additional barriers and reduce costs, ambitious, targeted, and near-term action is required.

Undoubtedly, numerous approaches are being researched and developed to reduce the environmental impact of water treatment while increasing hydrogen production. Perhaps more importantly, wastewater could eventually prove to be the clean fuel of the future.

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