Advanced Plasma Power and National Grid have joined forces to commercialise the decarbonising potential of energy from waste.
Municipal waste has long been a source of energy, through incineration, for heat. The UK has not historically capitalised on this potential directly, instead choosing to send large quantities of rubbish to countries with high heat needs like Sweden and Denmark. However, in late November, an important milestone was passed in a project that will build the world's first grid-connected bioSNG plant fuelled by waste and run commercially. The pioneering plant is intended to prove the business case for a technique that would let the UK harness the potential of its waste as a homegrown energy feedstock.
National Grid has worked in partnership with Advanced Plasma Power since 2014 to develop a technique for the gasification of municipal waste to produce grid-quality methane. The work has been funded through the network innovation competition.
To date, the process has been trialled at a small-scale pilot plant in Swindon, but in November, National Grid and its project partners hosted a celebratory event to mark the start of construction for a full-scale commercial facility.
The new plant will sit on the same site as the pilot facility but will operate at 10-20 times the scale. It will process 10,000 tonnes of waste a year and have an energy generating capacity of 22GW. It will also create synergies with the low carbon transport sector since the bioSNG produced by the novel waste gasification process is also suitable for use in gas-fuelled heavy goods vehicles.
"BioSNG links together a number of things. It establishes the utilisation of the existing gas network. All of the work that we have been doing around replacing the network - taking out the old cast iron pipes and replacing them with polyethylene - gives you a robust network to build off that whole process of decarbonising heat and transport." Chris Train, chief executive, National Grid Gas Distribution
The process that National Grid and Advanced Plasma Power have trialled takes shredded and dried municipal waste and coverts it to a clean syngas using a close coupled gasifier and plasma converter. The syngas then undergoes further cleaning to reduce contaminants to very low levels and is passed through a series of catalysed reactions to convert it into methane and carbon dioxide. The CO2 is removed to leave a green gas that can be injected into the grid.
As well as extending the life of the gas grid, this new waste to energy process has multiple environmental benefits. It reduces CO2 emissions by up to 80% compared with fossil fuel-derived gas and offers a tidy solution to the perennial issue of how to dispose of waste.
The production of fuels through gasification - from coal, for example - is not new, but, historically, applying the same process to waste produces a gas contaminated with tars. These tars foul catalysts preventing any conversion of the syngas.
In the Swindon pilot plant, this problem was solved by using plasma technology to efficiently crack the tar into syngas, making waste a viable fuel source.
Although the underlying technology is well-proven, the process has evolved as lessons have been learnt at the pilot plant. For example, the process was originally planned to run at atmospheric pressure to minimise risks, but it became clear that the reaction process must be carried out at higher pressure to be effective.
In addition, one of the plant's main objectives is also to produce CO2 of a quality suitable for use in the food industry.
To do that the CO2 must be very clean, and a different technique has been chosen for the commercialisation plant to ensure the gas meets the necessary standards. It will now be processed into a liquid, pushing up the refinement to 99.99%.
With processes and technologies largely proven and construction underway, attention has turned to proving the commercial model for the new plant when it begins operation in 2018.
Local Logistics Company Howard Tenens has agreed to come on board as the "anchor client" to prove the plant's ability to contribute to the decarbonisation of transport - an important goal in meeting the UK's overall decarbonisation targets.
The criticality of this aspect of the plant's potential is emphasized by the £11 million pounds of funding offered up by the Department for Transport. This adds to £6m of Network Innovation Competition support.