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Using Waste Heat From a Refuse Incinerator to Grow 5,000 Tons of Tomatoes

Mayor Jean-Luc Raysseguier at the site of the refuse incinerator and greenhouses in Bessieres, France

Mayor Jean-Luc Raysseguier at the site of the refuse incinerator (left) and greenhouses in Bessières, France.

Ten hectares (108,000ft2), thousands of cubic meters of displaced earth, enormous engines, intense activity. We are at the construction site of greenhouses in Bessières, France, where an exciting and widely replicable project will use waste heat from the incineration of unrecyclable municipal waste in a cogeneration plant to heat nearby greenhouses that will produce 5,000 tons of tomatoes a year, as well as saving greenhouse gas emissions.

The incinerator and cogeneration

Unrecyclable municipal waste represents an important source of energy. Indeed, the carbon content of a tonne of waste is equivalent to that of 1.5 barrels of oil, or 330 kilograms of coal. France produces 20 million tonnes of residual household waste per year, which represents an energy potential of four million tons of oil equivalent.

With energy prices weighing heavily on the household economy and the country's trade balance, Suez Environmental, which designed the incineration process, strongly believes in this energy source.

When incinerated, two different types of energy can be generated: thermal heat to heat homes, and injectable electricity for the national grid. This is known as Combined Heat and Power (CHP) or cogeneration. Moreover, energy recovery from waste is a genuine carbon sink: if the residual thermal heat is recovered, all of the emissions from the incineration can be compensated for.

Suez has developed a technique to increase the energy efficiency of waste recovery units and export the maximum heat available through cooling and condensation of the electricity-generating turbine exhaust fumes in hot water at 48°C. This water can then flow to customers located within two kilometers of the site. In this case the customer is a greenhouse.

The incinerator

The incinerator.

The implementation of this process is being done by Econotre, the local subsidiary of the Group dedicated to the recovery of waste.

All this has been made possible by the long-term collaboration between Suez and the joint association DECOSER, which includes the small town of Bessières and 158 surrounding municipalities.

In 1995, the union told Econotre to do something about the treatment and recovery of its municipal waste. It foresaw the establishment of a single platform of a recyclable waste sorting center from selective collection of waste, and an energy plant waste.

In ten years, energy recovery from waste treated by Econotre in Bessières generated the equivalent of the annual energy consumption of a population of 570,000 inhabitants.

The greenhouses

Soon, the seven-meter-high (roughly 23 feet) glass greenhouses will emerge from the ground. A first module will be built, then a second, and finally a third. The project, carried out privately by Gilles Brifaud, is financially supported by Ademe, the Mid-Pyrenees regionEconotre and Suez Environmental.

It stands on land sold by the city "at a special price for an exceptional project," assures Mayor Jean-Luc Raysseguier.

Tomato greenhouse in the Netherlands

A similar tomato greenhouse in the Netherlands.

When completed, over 100,000 square meters (roughly 25 acres) of greenhouses will stand behind the incinerator.  Econotre has committed to 2.5 million euros in project work to the greenhouse, and in total, 18 million euros will have been invested in this large site. It has an annual turnover of more than seven million euros. 

"It will generate an estimated 28,350 megawatt-hours per year, displacing around 2,835,000 liters of fuel and 6,350 tons of carbon dioxide, which will not be emitted every year. There are zero emissions and the output will be recycled into green waste. We are already imagining a contiguous structure for this," the Mayor announced.

Hydroponic Tomatoes

5,000 Tons of Tomatoes Per Year

Food production will begin in January 2016 and the Mayor says the greenhouses will provide 5,000 tons of tomatoes per year. "At a time when we import 558,000 tons of tomatoes per year to France, and when the MIN (train station market) of Toulouse also displays a need, we can say that we have invested properly in doing everything to make this installation possible," he said. 

Original article, published in French on La Depeche, here. Additional material about the incinerator and the CHP process has been added by Sustainable Cities Collective editor David Thorpe.

Credits: Data and images linked to sources.

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