Dit rapport bevat een beschrijving van het aquaponics model dat is ontwikkeld binnen het EU-project GEOFOOD.Energiemodellen voor de productie in kassen en recirculerende aquacultuur systemen zijn gecombineerd om te evalueren hoe er optimaal gebruik kan worden gemaakt van een geothermische bron. Het model kan worden ingezet als een ontwikkelingstool om het directe gebruik van geothermische warmte binnen aquaponics, en daarmee de agri-food sector te stimuleren.
In high tech greenhouse cultivation like in The Netherlands, large amounts of fossil energy are used to optimize climate conditions like temperature and humidity. To achieve a more sustainable greenhouse horticulture, a considerable reduction in energy use is needed, but tradeoffs with production and quality are not acceptable. Therefore, we developed a novel cultivation system for tomato to meet the goal: reduction of the energy input by 40% from 1.3 to 0.75 GJ.m-2 .y-1 , maintaining a production level of 60 kg.m-2 .y-1. This concept, the Next Generation Greenhouse Cultivation, is based on the intensified use of thermal screens combined with control of humidity, maximizing the use of the integration capacity of the crop, growing at high humidity, improved efficiency of CO 2 supply by reduction of ventilation and the use of cooling combined with a heat pump and an aquifer. In this approach, the main element is the prolonged use of screens with a high insulating value (>70%) to reduce the energy demand, combined with a forced ventilation system that injects relatively dry outside air into the greenhouse. The maximal use of the integration capacity of the crop implies a strong relation between daily radiation sum and diurnal mean temperatures, and a large difference between night and day temperatures on sunny days. This reduces the energy input and ventilation rate. Growing at increased humidity, achieved by misting, reduces ventilation rates because of the increased enthalpy of the greenhouse air. When supplying CO 2 , reduced ventilation results in higher CO 2 concentrations and hence a higher energy efficiency. Cooling can be used in combination with a heat pump and an aquifer to reduce the need for fossil fuel. This approach, in which proven technologies are combined, enables growers to implement the elements step by step, leading to an easy acceptance.
The Mobale gold mine (Kivu, Zaire) has been worked since 1923, but the presence of aurostibite in the ore was recognized only very recently. The discovery of the mineral has also led to the recognition of its heretofore unsuspected reactivity during the amalgamation ore dressing operations. At the surface of aurostibite a layer of up to 30 ~tm thickness forms which has an overall brown colour and a low reflectivity, and is composed of several variegated, concentric zones. These zones contain gold, mercury, antimony and oxygen, with traces of iron and arsenic. Oxygen is present with a concentration range of 2-4 wt.% (20-30 at.%). The zones form at the expense of aurostibite, according to micrographical criteria. In complex grains formed of gold-arsenopyrite-galena-aurostibite, only aurostibite is affected by the formation of the external brown zones. Later pure gold veneers are deposited on the outermost surface of the brown layers during the processing of the ore. The newly discovered features of processed aurostibite could explain some of the difficulties met with during the dressing of antirnonian gold ores.
Voor het EU-project GEOFOOD is een aquaponics model ontwikkeld dat gericht is op gebruik van geothermische energie. Om de functionaliteit en toepasbaarheid van het model te demonstreren bevat dit rapport de resultaten van twee scenario studies die productie van groenten in kassen aan de hand van aardwarmte in Nederland als uitgangspunt hebben. In deze scenario's worden een tomaten-en slateelt in de kas gecombineerd met een recirculerende aquacultuur faciliteit waarin snoekbaars wordt geproduceerd. De resultaten omvatten warmtevraagprofielen van de kas-en aquacultuurproductie, evenals een indicatie van de mate waarin een aquaponics systeem geothermische warmte kan benutten.
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