GeoFood: An example of circular economy by using geothermal heat, RAS and horticulture to produce fish and vegetables

by LandIng Aquaculture, Netherlands

As the world moves away from fossil fuels, we keep on the lookout for alternative ways to supply our countries with electricity and heat. Geothermal energy is still a largely untapped renewable resource and offers great potential. For instance, the European ERANET project GeoThermal estimated that Europe produces 1.5GW of electricity from geothermal sources. However, they estimate Europe’s capacity could be equivalent to 80-100GW of electricity.

Different countries offer different possibilities. Areas with active volcanism such as Iceland and Italy have high-temperature, shallow sources of heat which can be used to create steam and with it, electricity. Other countries, such as the Netherlands, sit over deep regions of lower temperatures, which can be used directly for district heating and industry. In the Netherlands, some horticultural greenhouse companies have made it an objective to operate their facilities with a minimum use of fossil fuels - both for heating and providing CO2 for their crops.
 

The Dutch geothermal growers, however, face a substantial challenge. Deep geothermal wells are large investments in the order of several millions of euros and. once running, they may not be utilised to their full capacity. As other utilities, geothermal wells have large fixed costs which must be spread over as many users as possible to guarantee profitability. This is a problem when most users prefer higher temperature heat, and when the demand disappears during summers. Today, geothermal wells are still eligible for subsidies that aim to support the transition towards sustainable energy sources.

We at the GeoFood project introduced the idea of RAS farms as heat sinks for geothermal heat and waste heat – this is, the lower temperature heat users generally do not want. Our rationale was that RAS farms 1) require a constant input of water and, if they grow a warm water species, heat, 2) they tend to use underground water sources which are colder than rearing temperature and 3) their water and sludge emissions can be used to fertigate greenhouses. Some preliminary modelling, in which a tomato greenhouse and pikeperch RAS are considered, showed us that, if RAS farms can be used as a heat sink for geothermal greenhouses heat extraction can be increased by 31 percent.

Read more, HERE.

The Aquaculturists

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