Small Scale Waste-To-Energy (WTE)

Sustainability problem

Landfill sites in cities are filling up quickly. The quantity of waste is ever-growing with the increase of population, industrial and commercial activities. Energy prices are on the other hand going skyward. Many regions have additionally begun introducing ambitious renewable energy targets.Technologies to deal with waste that have by-products of energy, hence, are highly sought after.  The currently dominant waste-to-energy (WTE) technology is operated at a large scale. Images  of mass incinerators exerting gasses from large chimneys and traffic from convoys of wagons transporting waste does little to the industry’s reputation with the prevalent Not-In-My-Backyard (NIMBY) attitude.

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Areas of sustainability

Waste, Energy, Pollution, Health.

Technology

Small-scale WTE plants tend to occupy 4 acres, in contrast to the average 20 acres required by mass burn incinerators. They are more affordable, have low profile construction and minimal emissions. They can thus be more easily integrated and presents a sustainable solution.  Although technological operators have varying small-scale WTE plant designs, the simplified explanation below will use that of ENERGOS ASA’s (a company based in Norway):

Picture1

(1) Fuel preparation process – municipal waste is pre-treated through shredding and magnetically separating recyclable ferrous material.

(2) Thermal conversion process (from waste to energy) – First, fuel enters the primary chamber where it is gasified and syngas is created. Second, the syngas is transported to the secondary chamber for high temperature oxidation.

(3) Steam generation – Hot flue gas from the secondary chamber then gets recovered in the Heat Recovery Steam Generator, which consists of a smoke-tube boiler, water-tube boiler and economizer. The boiler system can be designated to deliver saturated steam (for heat) or superheat (for electricity production).

The system comes with a dry flue-gas cleaning system where lime and activated carbon are injected downstream from the economizer, separating ash from flue gas hence controlling air pollution. 

Stakeholders

Municipalities, Citizens, Technology Operators, Environmental NGOs, Investors

Deployment

  • Municipalities need to be lobbied for the installation of small-scale WTE plants.They need to be exposed to successful implementation case studies.  NGOs may play a large part in providing assistance for such lobbying efforts.
  • Local communities in areas with potential installation of small-scale WTE plants need to be educated regarding its benefits (especially in comparison to the larger scale WTEs) in order to change their perspective.
  • Proponents of the technology needs to network and maintain good relations with investors in order to derive more funds for research and development to refine the existing small-scale WTE technologies.
  • As the technology can be useful not only by municipalities but also companies with large production of waste, governments should also provide market incentives.
  • Technology owners are expected to come up with financing options for municipalities that are interested in applying the technology.

Sources

http://www.energ-group.com/energy-from-waste/

http://www.seas.columbia.edu/earth/wtert/sofos/Ellyin_Thesis.pdf

http://www.ieabioenergytask36.org/Publications/2001-2003/Publications/Review_of_Small_Scale_Waste_Conversion_Systems.pdf

http://www.energ-group.com/energy-from-waste/the-process/

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