Field of the invention

The present invention relates to a method of treating biomass with laser light intended for biomass production and apparatus for performing the method.

Prior art

Nowadays processing of biomass in fermenters where biomass is decomposed into biogas as a result of anaerobic effect of microorganisms has been known. Biogas is a mixture of gases that consists mainly of methane and carbon dioxide. Biogas is released during the anaerobic digestion of organic material which is a substance of biomass.

A fermenter is an air-tight sealed container used for storing biomass. Biomass is prepared mechanically to the form a homogenous substrate which facilitates the process of anaerobic digestion of organic material. Mechanical preparation consists of crushing, stirring, milling and pushing through sieves. The purpose of mechanical preparation is disintegration of biomass into small particles which can be decomposed by microorganisms more easily. Mechanical operations contain as well stirring of digestate (biomass prepared to be decomposed inside the fermenter).

In addition to it, biological and chemical methods of treatment of biomass delivered to the fermenter have been known. They contain mixing additives into biomass to facilitate propagation of microorganisms, chemical substances for reducing the aggressiveness of external environment, for cleaving of fats, sugars, and proteins and deiivered biomass against microorganisms, and inserting appropriate mother cultures for quick propagation in the fermented volume etc.

Disadvantages of the above solutions lie in the fact that a big proportion of organic material, especially macromolecular substances (cellulose and hemicellulose), is not decomposed into biogas, and a large percentage of organic waste is produced that has to be removed from the fermenter again and stored in the waste dump or terminal pits according to its consistency. Using chemical substances is not safe for the operators during delivering biomass and at the same time chemical substances present a burden for the environment, they are expensive in relation to acquisition costs, and biomass fermentation process in the fermenter is not accelerated in a safe way.

The invention is directed to providing a method of treating biomass that would reach a higher level of biomass decomposition during anaerobic digestion using microorganisms, limit utilization of chemical substances, accelerate the process of biomass production in fermenters, be friendly to the environment and safe both from operational and economical aspects.

Summary of the invention

The above aim is reached by means of the method of treating biomass with laser light according to the present invention.

According to the method of treating biomass with laser light biomass is firstly disintegrated mechanically and stirred to form a homogenous substrate, and then biomass is transported to the fermenter, after which it is stirred in the fermenter during its anaerobic digestion.

The invention is characterized in that biomass is irradiated with laser light before being transported to the fermenter and/or biomass is irradiated with laser light inside the fermenter concurrently with stirring.

Laser light contributes to the biophysical degradation of biomass which is required for a better process of anaerobic digestion by means of microorganisms. Incident laser light disturbs the iignocellulose structure of cell walls of plant biomass. That supports higher activity of microorganisms and enzymes in the fermenter which leads to increasing the production of biogas up to 18% compared to standard methods. Moreover, laser light has a biostimuiating effect on microorganisms, especially on their cell organs. It results in increasing their reproductive abilities, especially of microorganisms involved in the fermentation process (hydrolytic, acetogenic, homoacetogenic and methanogenic bacteria).

Wavelength range of laser light in the preferred embodiment is from 350 nm to 1 ,000 nm while the wavelength range of laser light used for treating biomass before its transporting to fermenter is from of 690 nm to 1 ,000 nm, and the wavelength range of laser light used for treating biomass during anaerobic digestion is from 400 nm to 840 nm. Higher wavelengths of laser light are more suitable for a physical decomposition of the lignocellulose structure while laser light with lower wavelengths, i. e. low-power lasers, are more suitable for a stimulation of microorganisms during anaerobic digestion.

Laser light in a preferred embodiment is scattered across the area. Duration of irradiating the biomass and/or laser light intensity is proportional to the composition and amount of biomass. Irradiation of the surface results in a transfer of sufficient quantity of energy to lignocellulose structures of biomass cells transported to the fermenter. The intensity of laser light and duration of irradiation corresponds to the quantity of transported biomass so that maximum disturbing of ceil walls in the transported volume could be achieved.

In another preferred embodiment of the invention laser light turns on during anaerobic digestion concurrently at the beginning of stirring of biomass in the fermenter and laser light turns off 5 minutes after stopping stirring in the fermenter. By means of stirring also microorganisms from greater depth, which are necessary to be stimulated by laser light, get on the surface easily. After finishing stirring such microorganisms float on the surface for sufficient time and are treated by incident laser light. After the expiration of specified time further treatment would not bring the required effect because it does not pass through the layer of microorganisms at the surface that has been treated, so laser light will turn off until further stirring. An apparatus for performing the method of treating biomass with laser light is a part of the invention.

The invention is characterized in that it consists of a laser expander with at least one integrated source of laser beam and at least one polygon that sweeps laser light to adjust laser beam to appropriate intensity and optimum exposition.

Biomass in the laser expander is transirradiated intensively by laser light focused on a small area using a polygon (system of mirrors) that sweeps laser light. In that way a large amount of energy is transferred to biomass which will disturb a lignocellulose structure of cell walls. The wavelength range of emitted radiation is preferably from 690 nm to 1 ,000 nm and the apparatus is located between the transport paths of homogenous biomass substrate and the filling opening of the fermenter.

A stimulating apparatus for treating biomass with laser light is a part of the invention as well.

The invention is characterized in that it includes at least one low-power source of laser light arranged inside the fermenter above the surface of stored biomass and at least one scattering means for scattering laser light on the surface area of the stored biomass. Incident laser light has a biostimulation effect on the microorganisms involved in an anaerobic fermentation of biomass. The source of laser light is arranged above the surface inside the fermenter so that the light could spread well, and light beam is scattered across the area so that a maximum part of the fermenter surface could be covered.

The advantages of the application of the invention consist in a non-toxic treatment of biomass, low operational costs, safety of operation, a high effectiveness and a profitability of biogas. As for the fermentation procedure it is appreciated that cell walls of biomass are broken, which can be hardly achievable by mechanical means, and that it is possible to stimulate cells and activate microorganisms while both methods of treatment of biomass can be combined. Exemplary embodiments of the invention

It should be understood that hereinafter described and illustrated particular cases of embodiments of the invention are shown for illustration and do not present any limitation of the invention to the examples shown here. A person skilled in the art will discover or will be able to provide by means of a routine experimentation more or less number of equivalents to the specific implementations of the invention that are described here in the text. Even these equivalents will be included in the scope of the following claims.

Solid state lasers of wavelengths from 690 to 1 ,000 nm, dye lasers of wavelengths from 504 to 650 nm, or gas lasers of various wavelengths are utilized during treating of biomass. The beam of these lasers is scattered across the area using a polygon that sweeps laser light (a mirror system) so that an appropriate energetic distribution of laser radiation across the effective area could be reached at a high coherence and a monochromatic character of laser light which provides for a maximum coverage of biomass.

Biomass, especially that of a plant origin, intended for a degradation to produce biomass as a fuel for a cogenerating unit is delivered to the batching apparatus. A laser expander is connected between the screw conveyor or tubing or other transport paths and the input opening of the fermenter. During the operation of the stirring cones in the batching apparatus the laser expander is triggered which controls passing biomass that is transferred in 1- to 2-hour periods to a BGS (biogas station) of the fermenter wherein the timing is specific according to the type of BGS and the type of the batching apparatus. The exposure (duration x intensity of radiation) of biomass to the laser radiation can be adjusted according to the amount of biomass passing through the laser expander or by changing the parameters of laser radiation.

Connecting the laser expander to the batching paths of biomass significantly shortens the decomposition of the lignocellulose structure because it has caused disturbing or breaking cell wails. Such a condition will enable a more intensive effect of microorganisms and enzymes in the fermenter, and therefore an increased production of biomass by 4 - 18%, according to the type and quality of biomass. For different types of BGS connecting the laser expander will be carried out in different segments of transport paths for biomass (dry, wet-dry, wet), but always so that irradiated biomass could immediately reach the fermenter.

The apparatus for treating biomass with laser light especially for stimulating microorganisms is based on a capability of laser radiation to change cell functions, i. e. bio stimulation. It utilizes the phenomena of stimulation of cell organs, above all mitochondrions for producing ATP (adenosine phosphate). ATP energizes the ceil which accelerates its reproduction. Photochemical effects of laser radiation on the activity of microorganisms that participate in the fermentation process (hydrolytic, acetogenic, homoacetogenic and methanogenic bacteria) are based on the principle of absorption of the respective photons that energize their cells and facilitate their fast propagation which positively influences biochemical processes in the fermenter of the biogas station.

A stirring device for digestate (a mixture of biomass and microorganism) is placed inside the fermenter to which a stimulating apparatus is connected for treating biomass with laser light. This is triggered concurrently with starting the stirrers while irradiating the moving digestate. It is turned off after finishing operating the stirrers (approximately 5 minutes) and turned on again in a new mixing cycle (approximately 9 -11 minutes) wherein the timing is individual according to the type of BGS. The stimulating apparatus for treating biomass with laser light uses low-power lasers of wavelengths from 405 nm to 840 nm. By transirradiating the digestate in the fermenter by the stimulating apparatus a stimulation of the respective microorganism groups, accelerated hydrolysis of the substrate, higher production of fermentation products and following increased production or increased speed of the production of methane can be achieved. Industrial applicability

The above methods of treating biomass with laser light and the apparatus for performing the same can be applied in the facilities that produce biomass from renewable sources, and can be used both individually or in a combination. Modifications of such methods are applicable in all cases where a degradation of biomass occurs or is utilized for producing energy (waste biomass and biomass suitable for producing energy, fuel mixtures, sewage sediments) or stimulation of microorganisms (fermentation processes).