Cutting Carbon Emissions with Coal Ash

Around the world the problem of continued methane emissions from historic landfill sites is a common one. However one UK company is well on the way to realising a novel approach to capping such sites that would make use of coal ash, an abundant industrial waste, generate heat and electricity, treat biowaste and cut green house gas emissions. Ben Messenger finds out more. PFA used as structural Fill material at Celtic Manor golf coarse in preparation for the Ryder Cup Image Credit: UK Quality Ash Association The potency of methane as a greenhouse gas (GHG) is well known, especially by the waste industry, which in many countries has taken significant steps to mitigate its impact over recent years. Composting, anaerobic digestion, mechanical biological treatment, landfill bans and gas collection systems are all on the rise. However, with many decades of waste disposal behind us, it's not just the vast and increasing quantities waste that societies dispose of today that's contributing to the cocktail GHG emissions. Around the world there is a legacy of old, closed and often forgotten landfill sites quietly emitting millions of tonnes of methane every year. Gas collection systems at such sites have traditionally been seen as too costly and inefficient to implement. However, one Cheltenham, Gloucestershire based company is proposing a holistic approach, able to absorb the costs of development and management from local authorities and landowners while harnessing energy and reducing GHG emissions. The concept Lichen Renewal's approach would see suitable historic sites capped, with gas collection and energy recovery systems installed. Nothing unusual about that you might say, but the novelty of the company's approach lies in the materials used, and the integration of waste strategy, energy production and GHG reductions. The company's proposals would make use of an abundant by-product of the UK's extensive coal fired power industry - redundant Pulverised Fuel Ash (PFA) - to cap suitable historic landfill sites. Speaking to Waste Management World, Quinton Richards, director of planning and communications at Lichen Renewal explains that while half of the approximately six million tonnes of PFA produced in the UK every year is used in the manufacture of concrete blocks, the remainder is sent to landfill due to insufficient demand, or too high a carbonaceous content. According to Richards the low permeability and pozzolanic properties (i.e. with the addition of free lime it can be turned into a cement-like material) of PFA make it an excellent material to cap landfill sites. Once capped it will be a relatively simple matter to effectively extract the methane. Nothing too out of the ordinary so far. The landfill is capped, all-be-it with an unusual material, and the gas is captured. If this was a run-of-the-mill landfill gas project you'd probably be expecting the gas to fuel a generator set, be upgraded for grid injection or be utilised by a local industry such as a brick kiln. However, if the landfill site is to be truly restored the cap needs a biotic skin, and for that Richards is talking in circles. Energy and waste circles that is. Lichen Renewal's concept would see the gas being burned onsite in a drying kiln to pre-dry locally sourced biowaste, ready to fuel a biomass pyrolysis gasification system. According to the company the upsides to such a system are many; significant greenhouse gas emissions are prevented, organic biowaste is diverted from landfill and syngas from the gasification process can be utilised to produce both electricity and heat. Furthermore, the biochar remnants of the biowaste lock in carbon for hundreds of years and can be used to create the fertile soil layer, or biotic skin on top of the PFA cap. Realising the dream The company itself was founded in 2009 as a progression of a landscaping exercise carried out by Richards - a planning barrister and environmental scientist - and his business partner. That project had intended to landscape Hampstead Heath and bring a public resource back into use, and while it never reached fruition it did put PFA firmly on Richards' radar. To date Lichen Renewal has focused its efforts on the potential development of two sites, one around 10 hectares and the other closer to 20 hectares. Negotiations are underway to secure both planning permission and finance for a facility that would supply energy to a proposed nearby housing development. According to Richards these negotiations are at an advanced stage, with a few issues left to iron out such as demonstrating that the proposals make the best possible use of the gas. International ambition The problems associated with organic waste generation, coal ash disposal, historic landfills and carbon emissions are common to most of the developed and developing world, and that's something the company says gives it international appeal. According to Richards, Lichen Renewal has met with members of the International Energy Agency's Clean Coal Centre, who were interested in its concept. "Because it's effectively based on previous urban development, it's something that's ubiquitous across developed and developing nations. These landfills are in Eastern Europe, Western Europe, America, China and India, and this is a way to integrate two major industries that are involved with carbon production - the energy industry and the municipal human waste industry," explains Richards. Conclusion While the company certainly seems to have some hoops left to jump through before its plans reach fruition, the proposed concepts appear sound. There's nothing particularly revolutionary about any aspect of its proposals, indeed it relies heavily on proven technologies. It's the configuration of those technologies to create an integrated and multi-faceted solution to a number of the energy and waste problems present in modern societies thats different. Historic landfills are restored, industrial waste is put to good use, fresh organic waste is treated and energy is generated. More Waste Management World Articles Waste Management World Issue Archives