The results of this study show that the production of renewable hydrogen from cereal straw is both technically and economically feasible.
The RBE ECHO2 technology has been developed over the last 12 years through initial work, testing of a prototype, and leading up to the completion of a first commercial unit. The first system at the Holla Fresh site in Mount Gambier, South Australia, had accumulated 3500 running hours to March 2021 and is the focus of ongoing design improvements and control optimisation. The patented technology has a range of key advantages that include:
• Multiple value streams from; biochar, syngas, electricity and heat and wood vinegar.
• Carbon negative performance via sequestration in stable biochar and further values in soil enhancement and nutrient recycling.
• Simple cost-effective construction.
• Unique counterflow operation that provides self-scrubbing to recycle tar and other condensables.
This study has explored a range of system design options to modify the ECHO2 system to produce high purity hydrogen. Whilst there are a range of early-stage technologies additions that could be applicable in the future, it has been found that there are a range of high TRL and commercially available additions that would allow a proof of concept trail in the near term.
It has been further established that a pilot scale system based on a single ECHO2 unit could produce hydrogen at a rate of 360 kg/day and at a cost of $5.40/kg, cheaper than any electrolysis system at that scale. Building a system at regional scale by using multiple units in parallel has the near-term potential to produce hydrogen at close to or below the national target of $2/kg. Other technologies are not expected to achieve this before 2030. If such a regional scale system were combined with an ammonia synthesis plant, then 20,000 t/year of emissions-free green ammonia could be produced at around $650/tonne, in the range of conventional fossil fuel based ammonia costs.
A regional system of this scale could be provided with sufficient cereal straw from a region of 40 km diameter. The ammonia product could then be used to make urea or other forms of fertiliser and in principle could provide sufficient fertiliser for an area of grain growing land of 59 km diameter. The biochar produced could also be returned to the same land area and in doing so return the bulk of nutrients removed with the straw, improve soil quality, and simultaneously sequester atmospheric CO2 in a long-term stable manner.
These positive results suggest that proceeding to a proof of concept program deserves a high priority.