From Jon Gibbins, UKCCSRC Director, Professor of CCS University of Sheffield:
To support the launch of the UK’s hydrogen economy initiative, estimates for GHG emissions from blue hydrogen production were issued by the UK Department for Business, Energy & Industrial Strategy (BEIS) on 17 August in a report ‘Options for a UK low carbon hydrogen standard’ prepared by E4tech (UK) Ltd and Ludwig-Bölkow-Systemtechnik GmbH with assistance from members of the UK’s Hydrogen Advisory Council and its Working Group on Standards and Regulations.
This report, which also covers other hydrogen supply routes, provides estimates for reducing the GHG impact of blue hydrogen over the period 2020-2050, shown above on the left. Autothermal reforming (ATR) is predicted to be able to achieve up to 98% CO2 capture during conversion of natural gas to hydrogen. Upstream methane, CO2, and other GHG emissions for the natural gas are estimated for a range of sources, as shown above on the right. These are mostly assumed to be around 5 gCO2/MJ LHV, just under an extra 10% on top of the CO2 emissions from combustion of the natural gas itself (approximately 56 gCO2/MJ LHV), although higher values may occur.
To get to net zero blue hydrogen, the only option is to compensate for emissions to the atmosphere by a corresponding carbon dioxide removal (CDR) from the atmosphere, with permanent storage – CDR is what puts the ‘net’ into net zero! Given the impermanence of the storage with most nature-based CDR options and potential capacity limits on the available amounts of biomass to use with CCS (i.e. BECCS), it is prudent to assume that net zero hydrogen may have to be achieved using direct air carbon capture and storage. Undertaking DACCS is really just a matter of paying for it – it can be done anywhere in the world, i.e. where there is secure geological storage and other helpful conditions, using renewable or fossil energy, and the timing need not coincide exactly with the emission. The questions at the moment are how much to pay and to whom, but it is clear that oil and gas suppliers are developing DACCS technologies themselves (e.g. Oxy Low Carbon, Northern Lights: Shell, Total and Equinor), as well as many smaller players.
CDR is very definitely not ‘cheating’, provided the polluter pays. It is the only way to get to net zero; all energy supply options involve some GHG emissions, even if only for construction. Not allowing – or indeed not insisting that – CDR with permanent storage is used to deliver net zero hydrogen is very much cheating on future generations, or even on our older selves. All IPCC scenarios that deliver moderate temperature increases show large amounts of global net-negative emissions being needed in the latter half of this century and beyond. Effectively, all of the CO2 emitted from now on probably needs to be removed from the atmosphere, sooner or later, to avoid dangerous climate change; much better to do it sooner and to include the actual cost of cleaning up our activities rather than kid ourselves that we can somehow satisfy the climate on the cheap.
So, the best technology for net zero blue hydrogen production is clear. The starting point is that any GHG emissions to atmosphere will cost whatever is required for DACCS – so on the order of hundreds of dollars per tonne. Upstream methane and CO2 emissions will be reduced as far as possible, with rigorous and independent verification, including remote sensing. With a realistic cost for compensating for methane emissions using DACCS, and proper checking, very significant improvements can obviously be expected. Similarly, very high levels of CO2 capture will be used in hydrogen production once DACCS is the alternative; it is common sense that the gases vented to atmosphere from the hydrogen production facility will have the CO2 in them removed down to around 400 ppm, as present in the atmosphere, because it will usually be cheaper to collect it for permanent storage that way.
And then DACCS needs to be developed as an essential component in net zero blue hydrogen production – and net zero everything else. Oxy and Carbon Engineering are currently working on a 1 MtCO2/yr plant, showing what can be done and how DACCS technology is progressing almost as fast as novel hydrogen production technologies with complementary high CO2 capture levels. In the meantime, assessments of the full cost of net zero hydrogen – whatever colour it is – need to include estimates for all the elements of production, including the DACCS needed to actually make it net zero. Taking a nominal value for blue hydrogen GHG emissions of around 10 gCO2e/MJ LHV, based on the BEIS report, and a fairly high estimated DACCS cost, $500/tCO2, gives an additional cost of 0.5 cents per MJ or, for a lower heating value for hydrogen of 120 MJ/kg, an extra 60 cents per kg of hydrogen. With non-net-zero blue hydrogen reported to cost in the region of $2/kg in the US, it is clear that the cost of doing net zero blue hydrogen properly will be a relatively minor increase, especially when blue hydrogen producers take net zero requirements seriously throughout the full chain and make appropriate adjustments to current practices.