Second energy source
Greenhouse horticulture in the Netherlands has set itself the goal of growing fossil-free (without gas) by 2040. The geothermal energy installation was the first step towards fossil-free cultivation.
The biomass installation is used as a second energy source to produce heat for the greenhouse without using natural gas. This installation will be used in the cold period as a supplement to the geothermal energy.
The biomass installation at Hoogweg consists of 2 boilers, each boiler has a capacity of almost 15 MW. The process is highly automated. Delivered wood chips are stored in a bunker, the unmanned overhead crane ensures a continuous supply of wood chips to the boiler. The process operator ensures the correct settings for optimal combustion.
How does the Biomass installation work?
The wood chips are brought from the bunker by means of a grab to a collection bin “a Hopper”. The wood then ends up in the boiler by means of elevator belts.
The combustion process consists of several variables that are closely related:
• supply of wood chips (type and quantity)
• supply of air (amount of air entering the boiler and the way in which, from above or below).
The better the different variables are geared to each other, the better the combustion is and there will be little residual product.
After combustion, the flue gases are filtered for nitrogen and particulate matter in a large cloth filter.
In order to cool the flue gases to the maximum, the gases pass through a condenser, after which the flue gases are further cooled down by means of heat pumps. The aim is for a temperature of 15-20 degrees, which goes outside through the chimneys of 40 meters high. The heat released from the flue gases is used to heat the greenhouses.
The ash that remains after the combustion process is collected and disposed of.
Better Biomass/ NTA 8080
In the biomass installation at Hoogweg, only wood is burned from residual flows. Local pruning wood is used that is produced during the maintenance of forests, roads and parks. Sustainable cultivation does not involve burning pellets or trees, this would not be financially appropriate either.
The pruning’s used are always certified with the sustainability label NTA8080, which is issued by an independent auditor. An annual check is part of the procedure. The European Union (EU) recognizes this feature and it meets the requirements of the Renewable Energy Directive. This characteristic ensures that the wood is sustainably produced, processed and traded.
The modern installation ensures optimal combustion of wood, the aim is to continuously get the highest yield from the process. An important part of the combustion process is ensuring proper cleaning of the flue gases. Various installations ensure that, for example, the ashes are purified from the smoke before this air goes out through the chimney.