To be considered “clean”, greenhouse gas emissions over the entire production cycle must not exceed these limits. Currently, the UK’s standards are the most ambitious in the world, according to a report by Big Four consultancy Deloitte.

Green hydrogen – hydrogen fuel produced exclusively through electrolysis using renewable energy sources – is an emerging solution, gaining increasing popularity as a key factor contributing to the decarbonisation of hard-to-abate sectors.

The World Economic Forum report highlighted this as an important consideration for industrialised Asian countries, which face the dilemma of meeting growing energy demands while transitioning to cleaner, more sustainable energy sources.

Published in the journal Nature, the study looked at more than 1,000 planned hydrogen plants in 72 countries. The researchers also included national grid mixes in 2030, modeled for a policy scenario limiting warming to 2°C.

Under the most optimistic production configuration, the median greenhouse gas emissions from all projects were 2.9 kg CO2e/kgH2, which is just below the EU standard but still above the UK standard.

This figure does not include transport-related emissions, which would increase emissions by a further 1.5-1.8 kg CO2e/H2, depending on whether the fuel was transported as liquid hydrogen or sent by pipeline to its destination.

Emissions from solar-powered generation only partially stayed below the U.S. limit, driven by higher emissions over the full life cycle of photovoltaic panels.

By comparison, wind power emits about 34 grams of CO2 equivalent per kilowatt-hour (g CO2e/kWh) of electricity, while solar panels generate almost 50 g CO2e/kWh.

However, by 2050, the majority of hydrogen production is expected to come from solar energy, with its share rising to over 60% from a projected 40% in 2030.

Optimal power configuration

Production models were another concern. The researchers who conducted the study found that the “connected to the grid: energy export” production configuration emitted the least greenhouse gases, regardless of the energy source used.

In the above configuration, excess energy generated from renewable sources was exported to the grid for use by other consumers and was therefore not included in the emission calculations for hydrogen production.

When different power configurations were considered, renewable energy use in the “grid-connected: energy export” configuration resulted in the lowest greenhouse gas emissions. The use of nuclear, excess renewable energy and hydropower also generate significantly lower emissions compared to using only grid electricity. Photo: Nature Energy

By comparison, the additional power generated in the “off-grid: curtailment” model was not exported and emissions were entirely attributed to hydrogen production.

The worst performing configuration with the highest greenhouse gas emissions was the ‘grid-connected: energy import’ model, which relied largely on grid electricity from fossil fuel sources to supplement intermittent renewable energy production.

China, the world’s largest hydrogen producer in 2023 and expected to remain so for the next two decades, currently relies on fossil fuels for production. The country has committed to generating about 70 percent of its hydrogen from renewable energy by 2050.

However, this means that one third of the electricity needed will still come from high-emission sources.

“Until electricity grids are fully decarbonised, using electricity from the grid, even if only to supplement intermittent renewable energy sources, could result in emissions exceeding those resulting from grey hydrogen production, thereby undermining the potential of (green hydrogen) projects to mitigate climate change,” the document emphasises.

Green hydrogen is considered a more sustainable alternative to its grey counterpart, the production of which relies on polluting coal or natural gas.

Clean hydrogen is expected to be a key part of the global transition to net zero emissions. However, it currently cannot compete economically with fossil fuels. Expanding production and plugging the renewable energy supply gap of around 100 gigawatts (GW) will be necessary to help meet projected demand by 2030.

Amid growing investment in green hydrogen and related infrastructure, the study authors called for greater clarity on sustainability standards.

They added that current regulations, which assume zero emissions for renewable energy use and equipment production, risk hiding the true environmental impact of green hydrogen production.

SOURCE: New study shows wind and hydropower lead in clean hydrogen, while solar lags behind

New Study Shows Wind and Hydropower Lead in Clean Hydrogen, While Solar Lags Behind