TECHNOLOGIES for removing greenhouse gases from the air will not work effectively enough to allow us to continue using fossil fuels.
A major study by scientists and engineers at Dublin City University and Trinity College found that the main negative emissions technologies (NETs) touted as ways to combat the continued release of carbon (CO2) and other gases will only have a marginal impact.
They warn that Ireland needs to minimise dependence on them as either a substitute or support for eliminating emissions at source.
The 2019 Climate Action Plan and the Programme for Government both set a target for Ireland to be at net zero emissions by 2050 but that presumes some emissions will be offset by emerging NETs.
The joint DCU-Trinity study concludes, however: “While continuing research and development can be expected to progressively improve our understanding of the potential for such CO2 removal and storage, it would be an extremely high-risk policy to base current mitigation action on strong assumptions of future gross removals at significant scale.
“There is no current basis for assuming that large-scale future removals will be possible at significantly less cost than for directly mitigating gross emissions now.
“On the contrary, there is significant risk that future removals at scale will prove to incur substantially greater societal costs or may not be feasible at all.”
Six commonly discussed NETs are examined in the study, including increased afforestation which means the mass planting of trees without later felling them for timber, and soil carbon sequestration which includes preserving and rewetting peatlands and reducing tillage farming to stop the disturbance of soil.
Spreading soils with biochar, a charcoal made from plant materials, or minerals, a process known as enhanced weathering, both of which increase capacity for holding on to CO2, is also considered.
Two forms of carbon capture and storage (CCS) are also examined. The first, bioenergy with CCS, involves burning plant materials or biomass to generate energy while capturing the carbon that would normally be emitted by way of scrubbers or some other method before it gets into the air.
The other, direct-air CCS, relies on the creation of a mechanism for sucking out CO2 already in the air. But CCS methods rely on there being a way of storing the captured CO2 for all time.
All the NETs studied, except for direct-air CCS, would eat into lands currently used for food production and other purposes, the study warns.
Direct-air CCS would create an additional demand for energy, was the least developed idea, was likely to be very costly and the problem of how to store the captured CO2 was not resolved.
The study works from the calculation that even if Ireland is emitting no new CO2 by 2050, we will already have overshot our carbon budget by around 600 million tonnes.
It says the deployment of NETs might remove that volume by the end of the century but a more realistic estimate would be removal of just 200m tonnes.