Waste-to-energy: worldwide - reducing landfill
Rachel Lawler looks at techniques for energy recovery from landfill around the world.
For the significant percentage of waste that cannot be reused or recycled, landfill is the only option. But materials that come to the end of the road at one of these sites will no longer go entirely to waste. Waste-to-energy schemes across the world are capturing the methane gas produced at landfill by decomposing waste or separating and burning residual biomass to create natural gas and electricity. This not only prevents gases from escaping into the environment, but also provides a secondary source of energy.
Renewable energy company ENER-G has launched a £1.5m landfill gas generation project at Tinajitas Landfill in Celaya. The scheme will capture the gas emitted from 1.5Mt of waste and convert it into one megawatt of energy – enough to supply 1,000 homes. The project aims to reduce CO2 emissions by 40,000 tonnes each year and is the third facility of its kind installed in Mexico by the company.
New York City, USA
The Fresh Kills estuary on Staten Island was once a landfill site, but is now being transformed into a park (right). Gas from the remaining rotting waste brings New York City US$12m each year in gas sales and provides 22,000 households on the island with high BTU, pipeline-quality natural gas. Across the country, 31% of landfill sites convert methane into energy, producing enough power to supply around 1,829,000 homes.
By 2014, the Power Generation Facility in southern-central Saskatoon aims to reduce the city’s greenhouse gas emissions by at least 45,000t each year while producing enough energy to power 1,300 homes. Landfill will be capped with clay, and gas retrieved through small wells and pipes. The gas will be combusted in engine generators to produce electricity and heat. The city also hopes to bring in an extra US$1.3m of revenue annually from the project’s partnership with SaskPower’s electrical grid.
Advanced Plasma Power and Group Machiels are working at a landfill site in Remo Milieubeheer in the city to process 16Mt of waste over 20 years. The project aims to salvage recyclable materials from the waste and produce energy for the local community, using the remaining, unusable material to create a fuel to be burnt for heat and electricity.
UK company Energos’ newest facility is located at Borregaard Industries in southeast Norway. The plant uses the company’s patented gasification technology to convert non-recyclable waste into gas using partial combustion heat to free the hydrogen and carbon in the waste and processes 78,000t a year. The new facility will help reduce CO2 emissions by 50,000t each year.
A pilot plant for producing high-quality fertilisers is due to open in the northern province of Alava. Organic waste from biogas plants will be decomposed in oxygen-free conditions to create a material called digestate. This will be marketed as an organic fertiliser for sports lawns and delicate agricultural crops, and will be up to 10 times more effective than conventionally produced alternatives. The facility could produce up to 9,200t of fertiliser each year from 28,000t of waste.
Lake Naivasha, Kenya
Food processing waste from farms near this Kenyan lake 100km north of Nairobi is to be used to produce biogas in two Jenbacher biogas engines from GE Power and Water. The engines are configured for co-generation, with surplus heat recovered for use in heating adjacent greenhouses.