LAWR

LANDFILL MANAGEMENT The golden landfill site? Are we ignoring the energy that we can obtain from closed landfill sites? Liz Gyekye visited Norfolk's Docking site to hear the debate there and witness a unique trial that is taking landfill gas and turning it into electricity and heat. echnology, love it or hate it, has the power to radically change the way we do things. Just think back to life before mobile phones, the internet and broadband. So does technology have the power to change the way we deal with closed landfill sites? Norfolk County Council (NCC) thinks it does. Of all the greenhouse gases, methane is one the most damaging. But it is produced by thousands of old landfill sites all over the world. Active and closed landfill sites have to have measures in place to capture the gas, as stated in the EU Landfill Directive. If the gas cannot be used, it must be flared. There are a myriad of combined heat and power systems available for generating energy from newer landfill sites. However, as sites move towards closure, the landfill gas generated decreases in quality and quantity making it more difficult to utilise and flare. It is estimated that there are around 20,000 landfill sites in the UK which are more than ten years old. Landfill sites can generate gas for more than 20 years. Innovation Norfolk closed its Docking landfill site, based near King's Lynn, in 2000. Before its closure, it accepted around 500,000t of household wastes from 1986. Previously, methane was burnt at the site to prevent it from entering the atmosphere. Now, it is employing an innovation called the GasBox to generate electricity from the low- concentration methane gas produced at its Docking site. In fact, NCC has been using two GasBoxes since January 2014. This new kit is produced by Swedish technology firm Cleanergy and it is the first time the firm has brought this technology into the UK. T April 2015 Local Authority Waste & Recycling 23 The GasBoxes utilise approximately 25m³/hr of the gas. Installed inside a modular container, Cleanergy's GasBox is an autonomous and flexible Stirling engine unit (small-scale combustion engines – invented originally by Scottish clergyman Robert Stirling in 1816). Also inside the container is a real-time power management system with remote access; a fuel pipe; plus a heat and electricity connection to a house, factory or warehouse with optional grid functionality. The landfill at Docking has been capped – using protective layers of sand and bentonite clay or LLDPE plastic to stop water and oxygen from getting in and methane out, allowing methane to be extracted. The landfill site has a multitude of boreholes which are approximately 15m deep. The bottom 12m of the pipe has slots into which the gas passes. It is transported to the GasBoxes through gas pipes with condensate liquid being removed through standard dewatering chambers along the pipe route. The technology then enables the gas to be turned into electricity which goes straight to the National Grid. It also uses surplus heat to dry wood chip on site. Since February 2014, the GasBoxes generated more than 70,000kWh of electricity which is now being used to meet the power requirements of the landfill site as well as generating a surplus for export to the grid. The introduction of the Stirling engines to Docking forms part of a trial. It is part of a ACUMEN (Assessing, Capturing and Utilising Methane from Expired and Non-operational landfill) project which is led by the Environment Agency (EA) and is part funded by the EU LIFE + environment programme, Defra, DECC and other landfill gas management specialists. The project ends this September. ACUMEN project advisor Shaun Robinson says: "We have regulatory responsibility for managing all aspects of environmental impacts from permitted landfill sites and many of our permitted landfill sites are closed or are closing." Robinson says that his team is very interested in "better managing gas from closed and older landfill sites" that are "perhaps generating a little gas than normal" adding: "We wanted to do that through demonstrating innovative technologies and techniques." "Innovative technology such as the Sterling engine can be applied to manage that gas in an efficient way." For the Council, the project has two positive outcomes – a reduction in carbon emissions and a new revenue stream. Norfolk County Council landfill strategy manager Charles Wright says: "The engines bring in income by selling electricity in to the National Grid. This can be sold to a standard supplier of electricity." All in all, taking an old invention and turning it into something new to produce renewable energy is an important step. Taking an old landfill site and rejuvenating it, is also an important step. What's not to love about technology? Norfolk's closed landfill site in Docking. Methane gas is extracted via pipes (see left pic) from the ground

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