Hythane in India: A bridge to nowhere?
India’s Minister for Petroleum & Natural Gas and Steel recently announced plans to expand the use of hythane beyond a 50-bus pilot project in New Delhi into other major cities. Hythane is a blend of 18% hydrogen and 82% compressed natural gas (CNG), and it has emerged as an intermittent technology in India because it can leverage existing CNG combustion engines and natural gas pipelines to introduce hydrogen for transport. Hythane is also viewed as a means to reduce tailpipe air pollution and greenhouse gas (GHG) emissions from CNG vehicles.
At the same time, it’s been more than a year since India adopted Bharat Stage VI emission standards (BS VI), which place world-class regulations on tailpipe emissions from new vehicles nationwide. There are also ambitious national policies for the deployment of battery electric and hydrogen fuel cell vehicles that have zero harmful tailpipe emissions. So, is hythane a bridge to realizing the full potential of hydrogen for transport or a detour with uncertain tailpipe emissions that prolongs the use of CNG?
For one thing, it’s not clear that hythane is able to reduce tailpipe air pollution. Pilot studies conducted on BS IV CNG light-duty vehicles and buses using hythane in India found reduced emissions of carbon monoxide and total hydrocarbons, but the change in nitrogen oxide (NOx) emissions was inconclusive. The variability in direction and magnitude of change for NOx is reflective of the broader literature, which finds that NOx emissions are sensitive to CNG engine specifications and settings. NOx is a precursor to ambient fine particulate matter and ozone, air pollutants with particularly deleterious health effects. In 2015 alone, 11% of premature deaths from air pollution in New Delhi were attributable to transportation emissions of these pollutants. Battery electric and hydrogen fuel cell vehicles, meanwhile, have no tailpipe pollutant emissions, and the replacement of BS IV standards with BS VI will bring significant reductions in NOx and particulate matter, among other pollutants.
Hythane also doesn’t significantly reduce the life-cycle GHG emissions of CNG vehicles. First, in order to reduce GHG emissions, the hydrogen must come from a low-GHG source. Currently, most hydrogen in India is produced from natural gas via steam methane reforming; when compared to using solely natural gas in CNG vehicles, this is an additional, GHG emitting step. While India has expressed intent to deploy carbon capture and storage (CCS) technology to hydrogen production, this would reduce, but not eliminate, the GHG emissions generated when hydrogen is produced from fossil fuels. Another hydrogen production process gaining increased political and private-sector interest in India is electrolysis, an electrochemical process that splits water to produce hydrogen, powered directly by renewably generated electricity. This is known as green hydrogen and it’s considered a zero-GHG fuel. Importantly, it could capitalize on India’s abundant solar generation potential and record low price of solar generation achieved in recent years. Still, even if the hydrogen is low- or zero-GHG, at best hythane can only slightly reduce the climate impact of CNG vehicles; this is because hythane is still mostly natural gas, and increasing the hydrogen content in the blend wouldn’t help because it would decrease hythane’s compatibility with CNG vehicles.
It’s also important to note that existing CNG vehicles and natural gas infrastructure won’t directly enable the transition to 100% hydrogen for fuel cell vehicles. While small quantities of hydrogen can be blended with natural gas and transported through existing natural gas pipeline networks, increasing blending levels introduces risk to the integrity of the pipeline due to differences in physical characteristics between hydrogen and natural gas. In addition, fuel cell vehicles have hydrogen purity requirements that will necessitate the installation of separation and purification technology at hydrogen fueling stations. The limitations of leveraging natural gas infrastructure for hydrogen demonstrates the value of conducting pilot projects that would establish infrastructure that supports long-term decarbonization solutions like hydrogen fuel cell or battery electric vehicles.
Fuel cell vehicles running on hydrogen emit no harmful pollutants, only water and air, and when run on green hydrogen have zero climate impact from upstream fuel. Battery electric vehicles have no tailpipe emissions and will have an increasingly positive impact on air quality and climate change mitigation as India continues to green its electricity grid through stricter power plant emission controls and increasing share of renewable generation. Additionally, both technologies can run solely on domestically generated renewable electricity—in the form of green hydrogen for fuel cell vehicles—and this would enable India to decarbonize its transport sector and reduce reliance on oil and gas imports.
The forthcoming National Hydrogen Energy Mission is expected to kick-start development of the hydrogen ecosystem. Rather than investing in the limited benefits of hythane, doubling-down on that policy would enable India to more directly pursue transport decarbonization.