How NZ could become a decarbonisation world leader

23 May 2022
Energy is the double-edged sword at the root of the climate crisis. Cheap energy has improved lives and underpinned massive economic growth. But because most of it comes from burning hydrocarbon fuels, we’re now left with a legacy of high atmospheric carbon dioxide (CO2) and an emissions-intensive economy.

But what if we could flip the energy-emissions relationship on its head? We would need a technology that both generates electricity and removes CO2 from the atmosphere. The good news is this technology already exists. What’s more, New Zealand is perfectly positioned to do this “decarbonisation” cheaper than anywhere else on the planet.

And the timing couldn’t be better, with the government’s first Emissions Reduction Plan calling for bold projects and innovative solutions.

We research how to burn forestry waste for electricity while simultaneously capturing the emissions and trapping them in geothermal fields. Since forests remove CO2 from the atmosphere as they grow, this process is emissions negative.

This also means a carbon “tax” can be turned into a revenue. With New Zealand’s CO2 price at an all-time high of NZ$80 per tonne, and overseas companies announcing billion-dollar funds to purchase offsets, now is time for cross-industry collaboration to make New Zealand a world leader in decarbonisation.

Bioenergy with carbon capture and storage

Artificial carbon sinks are engineered systems that permanently remove CO2 from the atmosphere. Bioenergy with carbon capture and storage (BECCS) achieves this by trapping the CO2 from burned organic matter – trees, biowaste – deep underground. An added bonus is that the energy released during combustion can be used as a substitute for hydrocarbon-based energy.

The Intergovernmental Panel on Climate Change (IPCC) has said climate mitigation pathways must include significant amounts of BECCS to limit global warming to 1.5℃. However, the technology is still new, with only a few plants around the world currently operating at scale.

Cost is a major barrier. New projects need expensive pipelines to move the CO2, and deep injection wells to store it underground. Because CO2 is more buoyant than water, there are also concerns that any gas stored underground might leak out over time. This is where geothermal fields can help.

Geothermal systems for BECCS

Geothermal is a reliable source of energy in New Zealand, supplying almost 20% of our electricity. We use deep wells to tap into underground reservoirs of hot water, which then passes through a network of pipes to a steam turbine that generates electricity.

Afterwards, the water is pumped back underground, which prevents the reservoir from “drying out”. New Zealand companies are world leaders at managing geothermal resources, and some are even experimenting with reinjecting the small amounts of CO2 that come up with the geothermal water.

Herein lies the opportunity. Geothermal systems already have the infrastructure needed for a successful BECCS project: pipelines, injection wells and turbines. We just need to figure out how to marry these two renewable technologies.

We propose that by burning forestry waste we can supercharge the geothermal water to higher temperatures, producing even more renewable power. Then, CO2 from the biomass combustion can be dissolved into the geothermal water – like a soda stream – before it is injected back underground.

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Source: theconversation