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Life-cycle GHG emissions of biomethane and hydrogen pathways in the EU

Friday, 15 October 2021

Earlier this week (10 Oct 2021), a study commissioned by the ICCT (International Council on Clean Transportation) was released which performed Life Cycle Analysis (LCA) for various low-carbon routes for producing hydrogen and biomethane - two gases with an important role in the green transition. The results of such a study are likely to influence which gases and production methods are considered sustainable in EU policy.

According to the REDII (recast Renewable Energy Directive), a gas can qualify as low carbon provided it meets certain minimum GHG (Greenhouse Gas) reduction thresholds. Depending on the application, fuel type and production plant commissioning date this can be anywhere between 50% and 80%.

The emissions should consider the entire life cycle of the fuel, including production as well as usage. To achieve this, the study performed LCA with sensitivity analysis on the candidate gases and their production methods.

The four biomethane production pathways considered were biomethane produced from:

  • wastewater
  • manure
  • landfill gas
  • silage maize (crop).

For hydrogen, the pathways included eight different sources:

  • Blue hydrogen - Natural gas or coal with carbon capture and storage (two different pathways)
  • Biomass gasification (one)
  • Electrolysis hydrogen - using renewable electricity, electricity using the forecast 2030 EU grid mix (two)
  • Hydrogen from biomethane (three).

A minimum threshold emissions savings of 65% or higher is required for biomethane in transport applications, rising to 70% for hydrogen as per the REDII. For electricity applications, this threshold is 70% increasing to 80% after 2025. The fossil fuel comparator in REDII is 94 g CO2 equivalent per MJ of fuel. Thus the 65% reduction threshold corresponds to emissions of 32.9 gCO2eq/MJ (or less) and an 70% threshold, 28.2 gCO2eq/MJ.

Results and conclusions from the report

As far as biomethane GHG intensity is concerned, gaseous biomethane from waste sources (wastewater, landfill, manure) were evaluated to have negative emissions using the adopted LCA approach. A high variance was noted for manure and sludge-based biomethane while crop biomethane did not meet the required reduction threshold.

For hydrogen, even fewer selected candidates met the threshold - only hydrogen from biomethane sludge, renewable electricity and biomass gasification had sufficiently low emission intensities. Carbon Capture and Storage (CCS) solutions, as well as hydrogen from manure and wastewater biomethane, showed high variance. The renewable electricity and biomass gasification solutions were acceptable to the limits of the sensitivity analysis and would meet the requirements under the stricter 80% threshold.

Wastewater sludge and manure had high variance mainly due to the risk of methane slip - methane gas is a powerful greenhouse gas, with a weighting 28 times that of carbon dioxide (that is 1 g of methane in the atmosphere is considered the equivalent of 28 g CO2 as far as global warming potential is concerned).

Based on the analysis, the report recommended ruling out incentives for fossil-based hydrogen and crop-based biomethane given that they are unlikely to meet reduction thresholds and provide substantial decarbonisation benefits. While arguments could be made that production facilities should be evaluated on a case by case basis and that even the less optimal production pathways offer some GHG savings, this will need to be balanced with practicality and bureaucratic burden.

When considering incentives for green hydrogen, they recommended claims of sustainability be backed up with the appropriate documentation - either PPAs or Guarantees of Origin. The aim here would be to prevent double-dipping on support payments.

Sources

Techxplore

International Council on Clean Transportation

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