Living off the landfill for renewables

There are various renewable energy options for operational and closed landfills. Alan Edwards looks at the potential revenue opportunities for a relatively untapped market.

The generation of electricity from landfill gas is well established, but with the gas resource being finite at each site, there is now increasing awareness that landfills also offer opportunities for the on-site generation of renewable energies. This not only provides operators/owners with corporate social responsibility benefits, but also offers additional generation-related income for the site under the renewables obligation (RO) and the forthcoming renewable heat incentive (RHI).

BERR and the EU define renewable energy as energy produced from one of the following five renewable, non-fossil fuel energy sources - wind, solar, geothermal, water and biomass. With the exception of water-related sources, there are possibilities for all of the other types that are worth exploring at both operational and closed landfills.

Where the wind blows
Siting wind turbines at landfills has been considered for a number of years, for example. In 2007 Infinis submitted a planning application for nine turbines at Greengairs landfill in North Lanarkshire and, more recently, the Spanish engineering firm Fomento de Construcciones y Contratas announced plans to install approximately 80 MW of wind energy capacity across its UK landfill sites operated via its UK subsidiary, Waste Recycling Group.

As with any wind energy development, a rigorous assessment of both technical and environmental issues is required. In addition to a high average wind speed, the other necessary attributes of an attractive wind farm site include good site access, good grid connection - often not an issue for landfills owing to the presence of gas engines - insensitive habitats, a landscape that can accommodate the development and a sufficient buffer between the site and surrounding development.

The appropriate location of the individual turbines, particularly with regards to ground conditions, is vital and founding the turbines on municipal wastes can be challenging. Notwithstanding this, it is expected that the trend for further wind energy developments associated with both operating and closed sites will continue. Solar power can be converted to either heat or electricity via photovoltaic systems. Developing solar power PV installations on landfills is an increasing occurrence in the US where the US Environmental Protection Agency has encouraged such moves.

Further impetus has come from the introduction of a new combined synthetic flexible capping membrane with strips of photovoltaic silicon cells attached to its upper side. A recent example of this can be found at the 5.6 acre facility at Tessman Road landfill in Texas. No such facilities exist in the UK, probably because of the historic lack of financial incentive and the less clear-cut case for solar PV power here.

As with wind power, there are also technical and environmental challenges such as settlement, slope stability and planning issues that need to be addressed. But, with more favourable market conditions and advances in PV technology, the possibilities for solar thermal heat generation in the UK are increasing - although it is necessary to have a suitable use for the hot water within close proximity to the site.

Meanwhile ground source heat pumps (GSHP) are a central heating and/or cooling system that pumps heat to or from the ground and uses the ground as a heat source in winter and a heat sink in the summer. There are many different types of system available but, the elevated temperatures associated with landfill wastes and associated leachate, enhance the potential usage of this approach.

While GSHP requires the heat user to be in close proximity to the generated energy, it may also be possible to directly use the landfill's extracted leachate as part of the process rather than a specifically installed system. At present, it is not known whether this has been implemented anywhere in the UK, although a 2400m long horizontal closed loop system has been used for the landfill site office in Kinsale, Cork, Ireland.

Anaerobic alternatives
Landfill gas is also generated by the decomposition of biomass in anaerobic conditions. The utilisation of the gas, via on-site engines, is the renewable energy that is most often associated with landfills. There are three other basic technologies that could be used. For medium-Btu landfill gas, it is possible to transport this to a nearby location for use as fuel for boilers and burners.

Another application would be to generate steam using an on-site boiler and transport the steam off-site. Landfill gas can be upgraded into high-Btu gas and injected into a natural gas pipeline. Although the cost of treatment can be expensive, the advantage of pipeline quality gas technology is that all of the produced gas can be used. It is also possible to convert landfill gas to methanol, ammonia or urea.

Landfill gas has been used for years to generate renewable energy at landfills. Alternative forms are becoming more economically viable. Landfill operators and owners should not ignore the opportunity that they represent for locations where finding productive and profitable land uses is often challenging.

Alan Edwards is a director of SLR Consulting

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