TECHNICAL FIELD

The invention relates to a method and a device for controlling pests in goods.

PRIOR ART

With the constant increase of imported goods such as foodstuffs, the demand for effective methods and devices for controlling pests in these goods is also increasing. Products such as rice, but also legumes and seeds are sensitive to the presence of stored product insects such as rice weevils or flour moths. These pests cause damage to the product and indirectly (through their excrement) there is contamination of the product, overheating and the growth of fungi. It is therefore evident that their presence in foodstuffs is absolutely undesirable. Transport containers with non-food related goods can also contain pests and controlling them is also essential for the quality and appearance of these goods.

While there are many different ways to control pests, most of the current control processes are based on the use of chemicals, such as methyl bromide (described in US6047496A) for example. Pest control methods used can be effective in destroying or limiting pest infestations, but they often have significant drawbacks. Most of the chemicals used today are toxic to humans. Goods exposed to such toxic pesticides may therefore contain potentially hazardous chemical residues, requiring further processing to remove these residues.

As an alternative to these toxic chemicals, there are also CO2 pressure treatment processes for pest control in goods. An enclosed space is used to which CO2 is added at a high pressure (at least 10 bar). Such a high pressure causes, for example, the imploding of insect eggs. However, these pressure treatment processes have the disadvantage that the goods can be damaged by the high pressure. In addition, the dimensions of the space used for this purpose are limited and certain goods with larger dimensions (e.g. sea containers) cannot be treated with these pressure treatment processes.

Moreover, such CO2-based processes are often performed on site (in situ), wherein CO2 is administered on the spot to the receptacle in which the infested goods are located, such receptacles are for example: a silo (EP1698353A1), big-bags and/or bags surrounded by a wrapper (EP3127432A1), a container (EP3127432A1) or buildings such as mills (EP0416255B) and greenhouses (US2014317996A1). This means that the effectiveness of the treatment is highly dependent on the gas and heat permeability of the receptacle in which the goods are located and/or the size of the goods is limited due to the use of a wrapper that has to be placed over the goods/receptacle on site

In addition to the correct concentration of CO2 the temperature and treatment time of the control process is also important for effective pest control. Insects are killed more efficiently when they show a sufficiently high activity. Many known control techniques (e.g. as discussed in US4989363A, JP2015057960A and JP2014117275A) do not take this into account and therefore show limited effectiveness.

There is a need for an environmentally friendly method and device for combating pests in goods, which moreover does not cause damage to the goods.

The present invention aims to find a solution for at least some of the above problems.

SUMMARY OF THE INVENTION

The invention relates to a method and a device for controlling pests such as insects and mites in goods such as food products.

In a first aspect, the invention relates to a method according to claim 1. More particularly, the present invention describes a method for controlling pests such as insects and mites in goods such as food products, wherein the goods are placed in a closed system and wherein the closed system and the goods placed therein are exposed to a CO2 concentration of at least 60 volume % and a temperature of at least 20°C for a certain treatment period. Preferred embodiments of this method are set forth in claims 2-8.

In a second aspect, the invention relates to a device according to claim 9. More particularly, the present invention describes a device for controlling pests in goods, the device comprising a gas-tight treatment chamber for placing goods; a CO2 injection system; sensors for measuring the CO2 concentration, temperature and pressure in the treatment chamber; supply and discharge pipes controlled by valves to regulate the CO2 concentration, the temperature and the pressure in the treatment chamber and one or more heating elements positioned on one or more side walls of the treatment chamber. A preferred embodiment of this device is shown in claim 10. In a final aspect, the invention relates to a method according to claim 11, wherein said method is performed by means of said device.

The use of the method and device of the present invention is entirely biological and has far fewer safety limitations than methods and devices using the traditional toxic pest control agents. Moreover, the method and device according to the present invention does not require the use of a high pressure, thereby limiting any damage to the goods.

DESCRIPTION OF THE FIGURES

Figure 1 shows a device according to an embodiment of the present invention.

DETAILED DESCRIPTION

The invention relates to a method and a device for controlling pests such as insects and mites in goods such as food products. The goods are placed in a closed system and exposed to a CO2 concentration of at least 60 volume % and a temperature of at least 20°C. The use of the method and device of the present invention is entirely biological and has far fewer safety limitations than methods and devices using the traditional toxic pest control agents. Moreover, the method and device according to the present invention does not require the use of a high pressure, thereby limiting any damage to the goods. Unless otherwise defined, all terms used in the description of the invention, including technical and scientific terms, have the meaning generally understood by those skilled in the technical field of the invention. For a better understanding of the description of the invention, the following terms are explained explicitly.

In this document, "a" and "the" refer to both the singular and the plural, unless the context presupposes otherwise. For example, "a segment" means one or more segments.

The terms "comprise," "comprising," "consist of," "consisting of," "provided with," "have," "having," "include," "including," "contain," "containing" are synonyms and are inclusive or open terms that indicate the presence of what follows, and which do not exclude or prevent the presence of other components, characteristics, elements, members, steps, as known from or disclosed in the prior art.

Quoting numerical ranges by endpoints includes all integers, fractions and/or real numbers between the endpoints, these endpoints included. With the constant increase of imported goods such as foodstuffs, the demand for effective methods and devices for controlling pests in these goods is also increasing.

In a first aspect, the invention relates to a method for controlling pests such as insects and mites in goods such as food products, wherein the goods are placed in a closed system and wherein the closed system and the goods placed therein are exposed to a CO2 concentration of at least 60 volume % and a temperature of at least 20°C, preferably at least 21°C, more preferably at least 22°C, more preferably at least 23°C, more preferably at least 24°C, more preferably at least 25°C, more preferably at least 26°C, more preferably at least 27°C, more preferably at least 28°C, more preferably at least 29°C, more preferably at least 30°C, for a certain treatment period.

In one embodiment, these goods comprise products for human and/or animal consumption such as foodstuffs, animal feeds and food products such as seeds (both for human and animal consumption). In another embodiment, these goods comprise non-food related natural products, such as tobacco, natural fibers, wool, animal skins, feathers, etc.

The goods can be packed in any packaging known in the art, such as big bags or packaging made of jute or cardboard.

Preferably, the temperature in the closed system is between 25°C and 35°C, more preferably between 28°C and 32°C, such as for example 30°C.

By placing the goods in a closed system at a temperature of at least 20°C, the pests present in the goods show the highest activity and the high CO2 concentration will be able to do its job optimally. Experiments have shown that a concentration of at least 60% by volume of CO2 (measured at atmospheric pressure or at a pressure that deviates from atmospheric pressure by a maximum of 0.5 bar) is necessary in the closed system to kill a sufficiently high percentage of pests within an acceptable period of time. In a preferred embodiment, at least 99%, more preferably at least 99.5% of the pests in the closed system are killed.

The duration of the necessary treatment period depends on the temperature in the closed system. The higher the temperature, the shorter the necessary treatment period.

In a preferred embodiment, the temperature in the closed system during the treatment is between 20°C and 42°C and the duration of the treatment period is between 24 hours and 336 hours. Experiments have shown that exposure to a concentration of at least 60% by volume of CO2 is capable of killing a sufficiently high percentage of pests for at least 24 hours at a temperature of 40°C in the closed system. However, this temperature is too high for many goods.

In a preferred embodiment, the goods are exposed for a treatment period of at least 72 hours to a concentration of at least 60% by volume of CO2 at a temperature between 28°C and 32°C, such as 30°C.

In another embodiment, the goods are exposed to a concentration of at least 60% by volume of CO2 at a temperature of 25°C for a treatment period of at least 120 hours. A longer treatment period is often undesirable from an economic point of view.

In another embodiment, the goods are exposed to a concentration of at least 60% by volume of CO2 at a temperature of 20°C for a treatment period of at least 336 hours.

Because the goods are placed at a temperature of at least 20°C, preferably a temperature between 25°C and 35°C, the pests present in the goods show the highest activity and the high CO2 concentration will be able to do its job optimally. As a result, it is not necessary to combat the pests present on the basis of high pressure. Indeed, the pressure in the closed system is preferably lower than 2 bar, more preferably between atmospheric pressure and 2 bar, more preferably equal to the atmospheric pressure or a pressure that deviates from this by a maximum of 0.5 bar. Such a pressure in the closed system is optimal, since no damage occurs to the goods at this pressure range.

In one embodiment, CO2 in liquid form is evaporated by means of a heat exchanger and the gaseous CO2 thus obtained is supplied to the closed system by means of pipes.

The liquid CO2 is delivered refrigerated in special tankers and pumped into and stored in a tank that is suitable for this purpose. The pressure in the tank remains constant, so that gas can be taken off without any problems, even during topping up.

The liquid gas is then returned to gaseous form through a heat exchanger and conveyed to the closed system via a gas distribution system.

The heat exchanger may be any suitable heat exchanger known in the art. In one embodiment, the heat exchanger is an evaporator, such as an atmospheric evaporator or an electric evaporator. For example, an atmospheric evaporator consists of aluminum tubes with longitudinal fins and works by heat exchange with the ambient air. In this way, the liquid gas evaporates and is brought almost to ambient temperature.

In an electric evaporator, the gas passes through tubes and these tubes are heated by a liquid that is electrically heated.

In one embodiment, a plurality of evaporators are connected in a group. In one embodiment, an atmospheric evaporator and an electric evaporator are combined. This is advantageous, for example, in the winter period, when the capacity of the atmospheric evaporator can fall sharply, and an additional electric evaporator can be used.

In a preferred embodiment of the method, the temperature in the closed system is increased to at least 20°C, preferably at least 25°C, before the CO2 concentration is increased to at least 60% by volume. In this way, the pests already show an optimally high activity when the CO2 concentration is increased. As a result, the pests are killed faster, and CO2 consumption is optimized.

In a preferred embodiment, the CO2 concentration, temperature and pressure in the closed system are controlled via a central control mechanism. This control mechanism may comprise, for example, a local computer, a local server, a remote computer, a remote server or a network.

In a preferred embodiment, the CO2 concentration, temperature and pressure in the closed system are measured by means of sensors. These sensors may be any suitable sensors known in the art. In one embodiment, CO2 is measured by means of a chemical sensor. In another embodiment, CO2 is measured by means of an infrared (IR) sensor. Pressure gauges, also called manometers, are instruments to measure the pressure of a gas or liquid in a system. Measuring pressure is important to monitor the quality of the process, but also to be able to see leaks or pressure build-up. In one embodiment, the manometer is an analog manometer. In another embodiment, the manometer is a digital manometer. Digital pressure gauges use pressure sensors to convert the pressure into an electronic signal. There are different types of pressure sensors, but the most commonly used is a piezoresistive pressure sensor. This sensor consists of a diaphragm provided with piezoresistive elements. The medium pressure causes the diaphragm to deflect, this deflection causes a change in the cross section of the piezoresistive elements which are directly coupled to the electrical resistor. In a preferred embodiment, the signals from the sensors are used to monitor and adjust the conditions in the closed system by the central control mechanism. For example, when the concentration of CO2 decreases in the closed system, the central control mechanism can increase the CO2 supply until it is again the desired percentage. The same applies to the regulation of temperature and pressure in the closed system. In one embodiment, the supply and discharge of CO2, pressure and heat is regulated via supply and discharge pipes controlled by valves. In one embodiment, the valves of these pipes are controlled by the central control mechanism. In one embodiment, CO2 is introduced into the closed system via a CO2 injection system. This injection system can be any system known in the prior art and can be placed at any position in the closed system. In one embodiment, the injection system consists of several injection units that are positioned at different positions along the walls of the closed system. In one embodiment, hot water is supplied through a conduit controlled by a valve. In one embodiment, the hot water then ends up in one or more heating elements positioned in the closed system. In one embodiment, the one or more heating elements are located on a side wall of the closed system. These heating elements can be any heating elements known from the prior art. In one embodiment, the heating element consists of one or more heat exchangers with tubes through which heated water flows and of one or more fans that blow the ambient air in the closed system along the warm tubes and ensure heat exchange. These one or more heat exchangers and one or more fans can be positioned anywhere in the closed system, such as for instance at the level of the side walls of the closed system.

When the gaseous CO2 is introduced into the closed system or by the expansion of the air in the closed system by heating, overpressure may arise in the closed system. However, this is undesirable as it may cause damage to the goods. In one embodiment, the overpressure in the closed system is discharged. This can be done via any discharge system known in the prior art. In a preferred embodiment, the discharge system consists of a mechanical and a pneumatic component, in particular a mechanical overpressure-relief valve positioned at the top of the closed system and a pneumatic valve. In case of overpressure in the closed system, the overpressure-relief valve will open first. This valve will automatically close again by means of gravity when the closed system is depressurized again. If the overpressure in the closed system cannot be removed sufficiently by the overpressure-relief valve, the overpressure will be registered by the manometer present, and the pneumatic valve will be opened in order to eliminate the overpressure.

In a preferred embodiment, the closed system is degassed after the treatment period. After degassing of the closed system, the goods can be removed safely. In a preferred embodiment, the goods are subsequently cleaned in order to remove the dead pests from the goods. The method of the present invention kills, but does not remove, the pests. That is why a so-called cleaning step follows after the treatment. In one embodiment, a specialized machine line is used for this purpose, which can remove the remnants of the killed pests. In a further embodiment, the cleanness of the goods can be increased. For example, if a batch of goods is also contaminated with twigs, stones, glass or soil, these can also be cleaned out.

In a preferred embodiment, the pests are arthropods, also known as Arthropoda. Arthropods are cold-blooded, invertebrates with an exoskeleton and jointed legs. Arthropods include various groups such as insects, arachnids, centipedes, and crustaceans. In a preferred embodiment, the pests are insects (class Insecta) and/or arachnids (class Arachnida), such as mites. These pests can cause damage to the goods and indirectly (through their excrement) there can be contamination of the product, overheating and the growth of fungi. This can lead, among other things, to damage to the goods and loss of value thereof. In addition, these pests can transmit and spread diseases.

In a preferred embodiment, the method is specifically suitable for controlling stored product pests. Stored product pests live on stored food supplies. These can be adult animals, but it can also happen that it is the larvae that affect the stocks. Stored product pests can include cockroaches, beetles, mites, moths and flies. Stored-product pest beetles include, for example, the bread beetle, the spider beetle, the broad-horned flour beetle, the sawtoothed grain beetle and merchant grain beetle, the khapra beetle, weevils, the yellow mealworm beetle, the red flour beetle, the bean weevil, the cigarette beetle, the foreign grain beetle. Stored-product pest mites include, for example, flour mite, cheese mite, forage mite, dried fruit mite, straw itch mite. Stored-product pest moths include, for example, the cacao moth, the Indianmeal moth or the Mediterranean flour moth. Stored-product pest flies include, for example, the fruit fly, the flesh fly, the blue bottle fly, the common green bottle fly. A characteristic feature of these pests in general is their being bound to products. Despite the fact that their names refer to specific products such as cacao, rice and corn, they often find several products attractive. The Mediterranean flour moth, for example, is not only found in flour, but also in other products such as buckwheat, oatmeal and all kinds of other grains.

In a preferred embodiment, the method of the present invention is capable of killing all life stages of the arthropods. In a following aspect the invention relates to a device for controlling pests in goods, the device comprising a gas-tight treatment chamber for placing goods; a CO2 injection system; sensors for measuring the CO2 concentration, temperature and pressure in the treatment chamber; supply and discharge pipes controlled by valves to regulate the CO2 concentration, the temperature and the pressure in the treatment chamber and one or more heating elements positioned on a side wall of the treatment chamber.

The gas-tight treatment chamber can be of any size. The dimensions of the treatment chamber depend, among other things, on the type of goods, the size and volume of the goods and the desired duration of the treatment period. In one embodiment, the surface of the treatment chamber is sufficiently large to place and treat a sea container (12m x 2.3m x 2.4m) with goods therein.

To guarantee a CO2 concentration of at least 60% by volume, it is essential that the treatment chamber is gas-tight. The CO2 concentration, temperature and pressure in the treatment chamber are measured by means of sensors. These sensors may be any suitable sensors known in the art. In one embodiment, the CO2 [sensor] is a chemical sensor. In another embodiment, the CO2 sensor is an infrared (IR) sensor. In one embodiment, the manometer is an analog manometer. In another embodiment, the manometer is a digital manometer. In one embodiment, the temperature is measured with one or more temperature sensors. These temperature sensors can be, for example, separately wired sensors that are placed in the goods or a thermometer that measures the ambient air.

In a preferred embodiment, the device is further provided with a central control mechanism for monitoring and adjusting the conditions in the treatment chamber. In one embodiment, the supply and discharge of CO2, pressure and heat is regulated via supply and discharge pipes controlled by valves. In one embodiment, the valves of these pipes are controlled by the central control mechanism. CO2 is introduced into the treatment chamber via a CO2 injection system. This injection system can be any system known from the prior art. In one embodiment, the injection system consists of several injection units that are positioned at different positions along the walls of the treatment chamber. In one embodiment, CO2 and O2 are discharged through a conduit controlled by a valve. In one embodiment, hot water is supplied through a conduit controlled by a valve and this hot water subsequently ends up in one or more heating elements positioned on a side wall of the treatment chamber. These heating elements can be any heating elements known from the prior art. In one embodiment, the overpressure in the treatment chamber is discharged. This can be done via any discharge system known in the prior art. In one embodiment, the pressure in the treatment chamber is mechanically regulated by means of an overpressure-relief valve. In one embodiment, the pressure in the treatment chamber is pneumatically regulated by means of a pneumatic valve. In one embodiment, the pressure in the treatment chamber is regulated by means of a mechanical and a pneumatic component, such as an overpressure-relief valve and a pneumatic valve.

In a preferred embodiment, the device further comprises a tank for the storage of liquid CO2 and a heat exchanger for converting the liquid CO2 to gaseous CO2. In a preferred embodiment, the tank is located outside the treatment chamber. In a preferred embodiment, the heat exchanger is located outside the treatment chamber.

The liquid CO2 is delivered refrigerated in special tankers and pumped into and stored in a tank that is suitable for this purpose. The liquid gas is then returned to gaseous form by a heat exchanger and conveyed to the treatment chamber by means of a gas distribution system.

The heat exchanger may be any suitable heat exchanger known in the art. In one embodiment, the heat exchanger is an evaporator, such as an atmospheric evaporator or electric evaporator. In one embodiment, a plurality of evaporators are connected in a group. In one embodiment, an atmospheric evaporator and an electric evaporator are combined.

In a preferred embodiment, the wall of the treatment chamber is fire resistant for at least 60 minutes.

In a preferred embodiment, the treatment chamber is provided with one or more access options, such as a door or a gate or roller shutter. In one embodiment, the treatment chamber can be locked by means of a lock on the one or more access options of the treatment chamber. In one embodiment, this lock is operated manually. In another embodiment, this lock is electrically operated. In a preferred embodiment, the lock consists of clamps. In a preferred embodiment, the treatment chamber is provided with one or more doors that can be locked by means of clamps. These clamps ensure that the treatment chamber is securely closed and locked. In order to make the treatment chamber gas-tight, in a preferred embodiment the entire circumference of the door is provided with an inflatable rubber device. This rubber device is inflated when the treatment chamber is locked and ensures that the treatment chamber is gas-tight. In a preferred embodiment, the treatment chamber is provided with a light indicator on the outside. In a preferred embodiment, the light indicator gives a signal when the treatment is in progress. In a final aspect, the invention relates to a method as described above, which is carried out by means of the aforementioned device.

In what follows, the invention is described by way of non-limiting figures illustrating the invention, and which are not intended to and should not be interpreted as limiting the scope of the invention.

DESCRIPTION OF THE FIGURE

FIGURE 1 : shows a device 10 according to an embodiment of the present invention. The internal dimensions of the gas-tight treatment chamber 1 are: 16,200 meters in length; 4,610 meters wide and 4,700 meters high.

The CO2 concentration, temperature and pressure in the treatment chamber are measured by means of sensors, namely an infrared (IR) CO2 sensor 2, temperature sensors 3 a,b and a manometer 4. These temperature sensors consist of separately wired sensors 3a that can be placed in the goods (not shown) and a thermometer 3b that measures the ambient air in the treatment chamber. The humidity in the treatment chamber is also measured by means of a sensor 5. The device is further provided with a central control mechanism (not shown) to monitor and adjust the conditions in the treatment chamber. The supply of CO2 is regulated via supply pipes 6 controlled by valves 7. The valves 7 of these pipes are controlled by the central control mechanism. CO2 is introduced into the treatment chamber via a CO2 injection system (not shown). Hot water is supplied through a conduit 12 controlled by a valve 7 and then enters a heat exchanger 13 positioned on a side wall 10a of the treatment chamber 1. A discharge pipe 11 discharges the water from the heat exchanger 13. Four fans 8a, 8b, 8c, 8d positioned at different positions along the walls 10a, 10b of the treatment chamber 1 set the heated air in motion, so that a rapid and correct heat exchange with the goods to be treated occurs. As a result, the goods to be treated will quickly get the right temperature and the pests present will be activated, so that the pests can be eliminated quickly and efficiently. The overpressure in the treatment chamber 1 can be discharged pneumatically by means of a pneumatic valve 14 and mechanically by means of an overpressure-relief valve 15. The treatment chamber is closed by means of a lock based on clamps 16. When the treatment is in progress, this is indicated by means of light indicator 17 on the outside of the treatment chamber 1.