Summary
Lenersan Poortman bv is located in Dordrecht, the Netherlands. It handles and trades in seeds, cereals, beans, peas etcetera that will be used for human and animal consumption. Raw materials are purchased worldwide and supplied either as sea freight through the port of Rotterdam or by road.
The majority of these commodities is stored for longer periods. The products are infected by insects, their eggs or other vermin originating from the land of origin or means of transport. During storage deterioration or loss of products should be prevented in order to ensure the best quality upon delivery. Until now the products were treated with a poisonous gas (methyl bromide, MeBr) or phosphoric gas, both are toxic and adding to the ozone depletion. Government policy prohibits the use of these gases after the year 2005. An alternative treatment is to store the goods for two weeks at a temperature of -30°C. As well as the increase in transport volume and handling this also requires a lot of electrical energy to drive the cooling installation. This project offers an alternative to deep freeze. The products are treated under pressure by CO2 . Also a higher killing ratio is obtained especially under the normally very resistant larvae. The installation comprises two tanks (autoclaves) and two silos. The product will be loaded into a tank or silo, packed in bags, palletised or delivered in bulk. The tanks and silos are big enough to hold a single truckload. By exposing the product to CO2 under varying pressures the time necessary for treatment can be varied. The system is constructed in such a way that most of the CO2 is reused. When the pressure is released from one tank the gas is captured in another tank with a lower pressure or sucked out by a compressor which stores the CO2 in a temporary storage tank. The company is still investigating ways to use the gas of which the pressure is to low to use it in the tanks. Adding it to the gas-tight wrapping of end-user packaging can be one way of using this gas. Compared to deep freeze storage the CO2 treatment saves approximately 3,220,000 kWh per year, the CO2 being a side product of the fertiliser industry. The extra costs compared to the building of a deep freeze storage (NLG 3,000,000) amount to NLG 600,000. Energy savings add up to NLG 355,000 per year, with extra savings on running and maintenance costs of NLG 50,000 per year. The pay back period is approximately 1.5 years. This project is important to companies that use toxic chemical treatment for the extermination of vermin or when the deep freeze method is used. Industries of particular interest include the food and beverages, textile, leather, wood and furniture industries.