By Peter Amos, YPN Chair
Imagine if we could just turn domestic rubbish into gas using a little bit of electricity and capture the carbon dioxide at the same time. That would be a biosynthetic natural gas with a negative carbon footprint! Could this be the answer to the low cost decarbonisation of heat puzzle, or a flight of fancy? Well, it may sound like a pipedream (sorry!) but try telling that to the 20 members of the Young Persons Network who visited Advanced Plasma Power (APP) in Swindon to see for themselves how this dream is becoming a reality.
Gogreengas, a forward-thinking group of gas industry companies that includes Advanced Plasma Power (APP), is building a full-scale gas plant that will prove this technology is commercially viable in a UK and world first venture. Biosynthetic natural gas (BioSNG) can be produced from specially prepared domestic rubbish by a three stage process: gasification to syngas, tar removal and methanation of the syngas.
Despite recycling efforts, the UK produces millions of tons of rubbish each year, a large chunk of which goes to methane-releasing landfill. Gasification and methanation are well understood processes, but the middle step (tar removal) has until recently proved the barrier to success for domestic rubbish. This is because the biomass in domestic rubbish can only be gasified at low temperatures, but this in turn creates tars and waxes that stifle the process.
However, it turns out that these tars and waxes are no match for an 8000K (7,727°C) plasma arc which, through a combination of heat and UV light, can break them down efficiently. The refinement of the process around the plasma conversion step started with two pilot plants: the first, to test the gasification and plasma conversion; the second, to test the methanation process (where it turns out the process can be tuned to make either methane or hydrogen, or a blend of both, by choice of catalyst). Liquid carbon dioxide is also produced by the process, this is sold to industry but in future could be fed directly into a carbon capture and storage system.
The success of these pilots led directly to the demonstration plant we were visiting that will show that BioSNG can be produced in significant quantities on a continual basis, de-risking the technology for wide scale deployment. The optimal size of plant appears to have around a 100MW syngas output to make the most efficient use of the plasma arc in the gas flow.
Andy Cornell and Kevin Griggs, of APP, gave a detailed technical overview of the technology and its potential role in the future of gas and the decarbonisation of heat. Next, they gave us extensive guided tours of the pilot plants and the demonstration plant under construction. A certain amount of imagination was required at the demonstration plant as certain key components (such as the plasma converter) had not yet arrived for installation, but the impressive scale compared to the pilot plants was evident.
The YPN members asked plenty of questions of Andy and Kevin to further their understanding of what looks to be a promising new technology, and we are grateful to them for their time and enthusiasm in hosting our visit.