WO2010003255A1 - Process for continual multiphase recycling of solid and liquid organic waste for a greenhouse culture - Google Patents

Abstract

The invention provides a process for continual multiphase recycling of solid and liquid organic waste for a greenhouse culture comprising recovering the solid and liquid organic waste; pre-treating the solid waste to produce a digestable mixture; anaerobically digesting the mixture to produce a digested solution, biogas and a fertilising sludge; filtering the liquid organic waste through a filtering marsh to produce a marsh effluent and marsh biomass; subjecting the digested solution to nitrification to produce an organic liquid fertiliser; and reintroducing the fertilising sludge, the marsh effluent and the organic liquid fertiliser into the greenhouse culture for biomass production. This integrated process recycles both solid and liquid organic waste and converts the waste into nutritive inputs for the greenhouse culture thus providing recycled fertilisers for efficient biomass production.

Description

PROCESS FOR CONTINUAL MULTIPHASE RECYCLING OF SOLID AND LIQUID ORGANIC WASTE FOR A GREENHOUSE CULTURE

FIELD OF THE INVENTION The present invention generally relates to the field of greenhouse cultures and more particularly relates to a process for continual multiphase recycling of solid and liquid organic waste for a greenhouse culture.

BACKGROUND

Greenhouse cultures represent a significant source of biomass production in a wide variety of industries. Greenhouses can enable year-round and high-yield production.

However, greenhouse culture production uses a significant quantity of fossil fuel energy, in the form of fertilisers, CGvenrichment, lighting and heat. For instance, fossil fuel input represents about 10-35% of production costs for heating and CO₂- enrichment of greenhouse cultures.

Due to the increasing cost of conventional fertilisers, governmental regulations, environmental concerns and consumer demand for organic food products, some biomass producers have converted their production systems to be more sustainable and organic. Such biological systems are generally challenging in terms of energy consumption since consideration must be given to appropriate water supply, source of fertiliser, source Of CO₂, treatment of wastewater and other wastes whether organic or inorganic.

Organic waste emitted by greenhouse cultures is a major challenge to the industry. It is usually discarded in sanitary landfills or directed to other waste management sites such as composting sites. Greenhouse effluents are generally released into the environment or treated by costly methods such as ozonation, ultra-violet (UV), heat (thermic) or chlorination. Some of these treatments such as chlorination, can be particularly dangerous to human health. The organic waste discarded from greenhouse cultures contains compounds that are not only lost as nutritive elements but in many cases degrade to form harmful compounds such as greenhouse gases. In Canada, vegetable greenhouse culture activity results in wasted nutritive solution that has been estimated at about 8,400 to 62,000 IJha per day. In addition, 3,000 m³ of greenhouse effluents contain more than 0.8 tons of nitrogen, 0.15 tons of phosphorus, 0.9 tons of potassium, 0.7 tons of calcium and 0.2 tons of magnesium. The management of the significant quantities of organic waste produced by greenhouse cultures constitutes a challenge and frustration not only for the greenhouse industry but for society at large.

There are some processes that attempt to treat organic waste such as anaerobic digestion, nitrification and wetland treatments. These processes operate independently, generally treat either solid or liquid waste, generate outputs that are simply disseminated onto fields or are unrecyclable, cannot adequately deal with elevated quantities chemical fertilisers used in the culture, and do not provide a sustainable resolution of the organic waste problem in greenhouse cultures.

There is indeed a need for a technology that overcomes at least some of the disadvantages of what is known in the field of greenhouse culture organic waste management. SUMMARY OF THE INVENTION

In response to the above-mentioned need, the present invention provides a process for continual multiphase recycling of solid and liquid organic waste for a greenhouse culture.

Accordingly, the process of the present invention comprises: recovering the solid organic waste and the liquid organic waste from the greenhouse culture; pre-treating the solid organic waste to produce a pre-treated digestable mixture; anaerobically digesting the pre-treated digestable mixture to produce a digested solution, biogas and a fertilising sludge; filtering the liquid organic waste through a filtering marsh to produce a marsh effluent and marsh biomass; subjecting the digested solution to nitrification to produce an organic liquid fertiliser; and reintroducing the fertilising sludge, the marsh effluent and the organic liquid fertiliser into the greenhouse culture for biomass production.

This integrated process recycles both solid and liquid organic waste and converts the waste into nutritive inputs for the greenhouse culture thus providing recycled fertilisers for efficient biomass production.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a block diagram schematic of an embodiment of the process of the present invention.

Figure 2 is a block diagram schematic of another embodiment of the process of the present invention.

Figures 3a-3d are graphs that left-to-right respectively represent the concentration of nitrogen (NO₃) in the effluent and three marsh cells in summer and winter; the concentration of phosphorus (PO₄) in the effluent and three marsh cells in summer and winter; the concentration of sulphate (SO₄) in the effluent and three marsh cells in summer and winter; and the concentration of chlorine (Cl) in the effluent and three marsh cells in summer and winter.

Figure 4a is a graph that represents the variation of nitrogen concentration (NO₃) in the filtering marshes as a function of time and the marsh vegetation.

Figure 4b is a graph that represents the variation of phosphorus concentration (PO₄) in the filtering marshes as a function of time and the marsh vegetation.

Figure 4c is a graph that represents the variation of nitrogen concentration (NO₃) in the filtering marshes for various treatments. Figures 5a-5d are graphs that represent the variation of NO₃ reduction (%) or P reduction (%) as a function of electric conductivity (EC) for different marsh vegetation. Figure 6 is a graph that represents the variation of NO₂ flow gas according to the use of different plants in horizontal subsurface flow wetland and does of sucrose as a function of time.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

The process of the present invention is for continual multiphase recycling of solid and liquid organic waste for a greenhouse culture. An example process block diagram is illustrated in Figure 1 and the various steps of this embodiment will be explained.

It should be understood that Figure 1 shows many possible streams and unit operations that may be performed for the recycling process and many of the outputs, inputs, unit operations, recycle streams, divided streams and other illustrated elements are optional depending on the conditions of a particular greenhouse culture recycling process. Embodiments of the process of the present invention enable a reduction in lost fertiliser of approximately 40-60% adding significant value to the system. Referring to Figure 1 , the process comprises recovering solid A1 and liquid A2 organic waste from the greenhouse culture A, pre-treating C the solid organic waste A1 , anaerobically digesting E the resulting pre-treated digestable mixture, marsh filtering B the liquid organic waste A2, nitrifying J the digested solution emitted from the anaerobic digestion E, and reintroducing various resulting products back into the greenhouse. In particular, fertilising sludge from the anaerobic digestion B, marsh effluent from the marsh filtering B and organic liquid fertiliser produced by nitrification J, are recycled back into the greenhouse culture for biomass production.

The process of the present invention has closed-loop characteristics allowing multiphase recycling. Not only are multiple phases of waste recovered from the greenhouse culture, but multiple phases of fertilising material are reintroduced into the greenhouse culture.

Recovering solid and liquid organic waste More particularly, the organic waste is emitted by the greenhouse culture as solid biomass (also called "solid organic waste") and liquid effluents (also called "liquid organic waste"). The liquid effluents may be collected and stored for later use when needed, for instance as process liquid for the anaerobic digestion.

In one embodiment of the process, the greenhouse culture comprises a vegetable culture such as tomato plants. The waste from a greenhouse tomato culture comprises the solid stems and leaves and the liquid drainage, runoff and other discharges. The process avoids disposal of such organic waste into a field or dump which would result in substantial fertiliser and mineral losses, but rather enables a contained recycling of the waste outputs. The "greenhouse culture" may be one or more vegetal cultures, ornamental cultures, medicinal cultures, algal cultures and aquacultures.

P re-treatment of the organic waste

Both the solid and liquid organic wastes are preferably pre-treated in preparation for subsequent processing. The liquid waste A2 may be pre-treated by filtration to remove crude particles to facilitate treatment by filtering marshes B prior to digestion E The liquid waste A2 may also undergo a sulphate-reducing treatment S3 prior to marsh filtering B or may be used in the making of the downstream nutrient-based solution N.

The liquid organic waste A2 often has a high sulphate concentration, for instance from .5 mM to 20 mM, and it is thus preferably treated by a sulphate bioreactor S3 which reduces the sulphate ions (SO₄^") in a passive or active fashion. This treatment may use anaerobic microflora including sulphate reducing bacteria (SRB). The sulphate bioreactor may resemble constructed marsh filtering and include a cell containing a solid support comprising peat, compost, bark, gravel, sand and/or volcanic rock According to the DOM, DCO and BDO₅ analysis, a mixed source of carbon is introduced into the sulphate bioreactor in order to obtain a ratio of CDO/ SO₄ of around 5 to 1 7 A neutral pH is preferably maintained and redox potential is less than -100 mV A pH varying from 5 to 8 may be tolerated by the sulphate bioreactor The hydraulic retention time may be from around 3 to 5 days or less

The solid organic waste A1 is pre-treated C to produce a digestible mixture ready for anaerobic digestion The pre-treatment may be tailored to the particular characteristics of the given solid waste For instance, in some cases the solid waste is ground up and acidified to transform it into slurry-like consistency Some pre-treatments may also be referred to as "liquification" The type of pre-treatment is based on the characteristics of the solid organic waste, e g physiochemical properties, preconditioning status, anaerobic digester conditions, etc , in order to facilitate loading of the organic waste into a digestion bioreactor and the digestion reaction The solid organic waste may be washed, ground, homogenized, acidified, sterilized, and/or diluted Of course, a person skilled in the art will understand that depending on the physiochemical characteristics of the organic waste, different pre-treatment C technique can be used

Once the solid and liquid organic wastes A1 ,A2 are pre-treated, they are subjected to separate process steps to begin converting them into greenhouse-recyclable mixtures

Marsh filtering

The pre-treated liquid organic waste A2 is sent for marsh filtering B The filtering marsh B may operate in vertical and/or horizontal flow and enables the use of irrigation water drawn in and contained in the marsh In the filtering marsh B, the liquid waste A2 is physically and chemically filtered by the marsh media and microflora to produce a filtered marsh effluent Many contaminant compounds and pathogens contained in the liquid waste are filtered, precipitated, degraded converted and/or deposited out as it seeps through the marsh, while nutritive elements become available to nourish marsh biomass In this manner, the liquid waste undergoes conversion into a liquid marsh effluent and solid plant biomass. The marsh effluent has reduced ammonium,

In a preferred embodiment of the process, there are multiple marsh cells that may be arranged in a network. The marsh cells are preferably arranged in series. The marsh cells are operated according to various thresholds such as final compositions of ions or pathogens.

In the case where the organic volume of incoming liquid organic waste is high, a pre-treatment will be preferred. A high volume or liquid organic waste may be treated in one or more treatment cells of the filtering marsh (B) which may be made of different types of materials such as sand, gravel, volcanic rush rock, peat, bark, and the like. It should also be understood that the marshes may be naturally occurring or constructed. The filtering marshes B are preferably located on land adjacent or proximate to greenhouses which produce cultures. For constructed marshes, an impermeable membrane on the inside of marsh cells may prevent the influx of effluents from diverging from their path within the marsh. Each marsh cell may be constructed with an impermeable membrane defining a bottom and side walls thereof. The marsh cells may also be designed to each have an air-exposed surface area sized to reduce formation of nitrogen-oxygen-based greenhouse gases from the marsh cell. Furthermore, the marsh cells are preferably subsurface-flow marshes. As such, the marshes each have an upper non- immersed layer and a subterranean immersed filtering layer. In subsurface-flow marshes, there is reduced nitrogen-loss and an advantageous combination of anaerobic and aerobic biological activity in the marsh strata.

The multiple marsh cells may include a pre-treatment marsh cell containing sulphate-reducing microflora, an ammonium-reducing marsh cell and a phosphorus-capturing marsh cell. It should be understood that each cell can be specifically designed to promote the reduction, extraction or generation of one or more specific contaminants or nutrients. Oxygen may be injected into one or more marsh cells at specific levels to favour the activity of certain micro-organisms, chemical reactions, or the absorption of nutrients by plants. In one preferred aspect of the process, at least a portion of the marsh biomass is recovered and anaerobically digested. The marsh biomass is preferably digested with the pre-treated digestable mixture for recycling therewith. The marsh biomass also undergoes pre-treatment, which may occur with the solid organic waste. The type of selected marsh biomass will depend on the geography, climate, humidity, liquid waste properties and the desired filtering treatment to effect. For instance, when a given type of marsh biomass is to be recovered, digested and recycled into the greenhouse culture, it is preferably selected to have a rapid early growth cycle. On the other hand, when a given type of marsh biomass is left untouched or allowed to grow substantially before harvesting, it is preferably selected to facilitate the desired filtering functionality of the marsh cell. It should also be understood that multiple types of marsh biomass may be selected alternated over time for a single marsh cell and one or more of the types may be recycled back in to the greenhouse culture. The farming of the marsh biomass may also be managed in connection with batches of recovered liquid organic waste to be treated or the marsh cell network arrangement.

For each cell of the filtering marsh, different macrophytic plants such as, phragmite, cattail, versicolor iris, typha, carex, spartine and water hyacinth, may be used according to the volume of liquid organic waste to be treated and in terms of its ionic charge, salinity as well as the climatic conditions. The marsh plants may be selected according to climate and competition between plants. Preferably, multiple filtering marshes are used in series with micro-organisms adapted to high ion content and plants which fix sodium. The use of the cells in sequence allows the efficient treatment of each volume and flexibility of the system. In the case where the cells do not comprise any physical support such as, in lagoons or basins, aquatic plants and invertebrates may constitute the main fixing means for nutrients. The surface aquatic plants such as the water hyacinth which grow rapidly are collected on a regular basis and are treated for reintroduction in the culture A. In the case where the aquatic species are used for entrapping or accumulating nutrients in the production of organic waste for anaerobic digestion, materials such as polystyrene rafts are left on the surface of the basins to support the plants on the surface, and these plants are tethered with the help of a support cord, if need be.

In the case where the filtering marsh has multiple cells, the greenhouse effluents are preferably first collected in an initial basin. The filtering marsh advantageously comprises three units for independent filtration. Each unit measure will depend of the effluent characteristics (biological, physical and chemical properties) and the treated volume, which will vary with the greenhouse area, plant population and crop irrigation management. The bottom of each unit is preferably covered in plastic. A central drain covers the entire surface of each unit, is installed at the bottom of the unit and is connected to a drum which is used as a pumping unit. Two effluent delivery systems in the marsh are also installed. The first system which will be used, mainly during cold weather, is installed at a depth of about 0.6 meters and comprises a polyvinyl chloride plastic pipe of about 2.5 cm in diameter and has holes about every 30 cm. This first pipe is then surrounded with another pipe of about 8 cm in depth which has holes also about every 30 cm. This first distribution system is covered with about 0.6 meters of additional sand. A second distribution system can then be installed on top of the marsh. The water collected in the pumping station of the first unit is then pumped into the following cell. A pump is connected to the distribution system of the adjacent cell and filters the liquid going through it.

In one preferred aspect of the process, a carbon nutrient source is added to the marsh to promote the purification, filtering and biochemical conversion activity. The carbon nutrient source is preferably a simple sugar and still preferably sucrose. It has been observed that addition of sucrose improves the filtering ability of the marsh. Sucrose has improved the biological activity of the microflora to metabolise the nitrogen-based wastes and enabled a short retention time of the effluents in the marsh, while being available, economic, and easily metabolised by a broad spectrum of micro-organisms. It has also been found that adding a simple sugar like sucrose enables elimination of sulphates more efficiently than when complex sugars are added. This improvement is even more striking when sulphate levels are high, e.g. around 500 ppm as compared to 250 ppm.

The filtering marshes B facilitate reducing the ionic charge of the liquid waste, eliminating pathogenic agents which can be found in effluents, accelerating the evaporation of the greenhouse effluent and the reintroduction of resulting marsh outputs (liquid effluent and biomass) into the process. The filtering marshes B also reduce the total suspended solids, total nitrogen and phosphorous contained in the liquid effluent.

The filtering marsh generates a marsh effluent that is recycled back into the system. In one optional embodiment, the marsh effluent is reintroduced directly into the greenhouse culture. Such embodiments are particularly suitable when the filtering marsh has a significant aerobic activity which reduces the ammonia content of the marsh effluent. In another optional embodiment, the marsh effluent is mixed with the liquid organic fertiliser emitted from the nitrification unit, as will be further described herein below. In yet another optional embodiment, the marsh effluent is nitrified alone or with the digested solution emitted by the anaerobic digesters, to produce the liquid organic fertiliser.

The marsh effluent may be reintroduced into the identical type of greenhouse culture from which the original liquid organic waste came. Alternatively, the marsh effluent may be reintroduced into another greenhouse that is part of an overall greenhouse culture network. For example, a first greenhouse may contain a tomato culture from which solid and liquid organic waste is produced and treated. The marsh effluent from that batch of liquid organic waste may be reintroduced into a tomato culture or a different greenhouse containing other vegetal cultures, ornamental cultures, medicinal cultures, algal cultures or aquacultures. Thus, a multi-culture network may be used to obtain organic waste and reintroduce the recycled elements.

It should also be understood that the recycling does not need to be exhaustive, but preferably includes recycling multiple streams back into the greenhouse culture to increase efficiency and reduce the ecological impact not only on local land and water but also on general greenhouse gas emissions. In one embodiment of the process, the greenhouse culture may be an aquaculture that includes aquafauna and aquaflora. Such cultures generate liquid organic waste rich ammonium, which must be subjected to nitrification.

In another embodiment of the process, the greenhouse culture unit into which the recycled streams are reintroduced is tolerant to a certain concentration of ammonium. In this case, the effluents from aquaculture may be treated and reintroduced directly to the irrigation system of such greenhouses. As such, the solid and liquid organic matter from these effluents is reintroduced to the greenhouse culture. In yet another embodiment of the process, the greenhouse culture may be a dual- culture. For instance, it may comprise a hydroponic culture using floating rafts (e.g. Hydronov™ rafts) coexisting with an aquafauna culture in the water basin. The aquafauna culture may comprise species of fish selected according to the markets and to the adaptability to temperate temperatures. The water of the fish farming basins T may be constantly oxygenated, treated by a nitrification system, balanced on a cationic and anionic ratio, diluted and/or re-circulated in order to provide reusable components to the culture. The temperature of the water of the fish farming basin, its pH and its salinity may be adapted to the plant culture and to the farming of fish. The fish may be fed with a biological diet which does not negatively affect the growth of the culture.

Anaerobic digestion

Referring still to Figure 1 , the pre-treated digestable mixture 14 is sent to at least one anaerobic digester E. It should also be understood that the anaerobic digestion may also be performed on the marsh effluent. As noted above, the solid organic waste is pre-treated before entering the anaerobic digesters. In fact, any solid matter to be introduced into the anaerobic digesters is preferably pre-treated.

Anaerobic digestion may occur, for instance, in psychrophilic, mesophilic or thermophilic bioreactors E. The may be multiple reactors which are preferably sequentially fed. It should be understood that thermophilic and mesophilic bioreactors may be preferably used under particular conditions such as the proximity of considerable residual biomass, mixed production (energy, greenhouse products, aquafauna cultures) and in hot climates.

In one embodiment of the process, the greenhouse cultures generate waste comprising ligneous biomass and/or high organic content and the anaerobic digesters are specifically designed for loading and digesting such waste.

The anaerobic digestion allows the degradation or elimination of pathogenic and toxic agents including pesticides, pollutants, fungi and unwanted bacteria, which are of concern both to greenhouse culture production and human health. Preferably, the digestion is designed and controlled to produce a biogas having weak NOx and SOx content and a minimal energetic potential. It is also preferable to minimise the release of streams and by-products that may contain pollutants into the environment.

In one embodiment of the process, the digestion includes sequential bioreactors being outfitted with the necessary outlets, valves, controls and reservoirs to recuperate carbon species (CH₄ and CO₂) as well as the macro- and microelements necessary for culture growth while eliminating the pathogenic and toxic agents contained in the input.

The anaerobic digestion E generates in digestion products including biogas E2, a digested solution E3 and a fertilising sludge E4.

The biogas E2 contains a considerable amount of methane. In some embodiments the biogas is on the order of less than 0.3 LCH₄/g COD. The biogas may be stocked and/or cleaned for future use F1. Once it has been cleaned, the biogas E2 can be combusted to produce energy F2, e.g. in the form of heat and/or electricity. This combustion energy may then be stored for future use F3 and/or may be reintroduced into the greenhouse culture A as lighting, electricity for liquid or gas circulation, heat, etc. The combustion biogas E2 also produces an important quantity of CO₂ G1 which may be stocked for future use G2 and may be reintroduced into the greenhouse culture G3. The well-timed enrichment of the greenhouse cultures A with CO₂ under conditions of active growth, such as a summer climate or a high soil radiation, allows an increase in the productivity of the cultures on the order of 10 to 20% compared to a conventional enrichment of CO₂ during periods when CO₂ is not being reintroduced into the greenhouse cultures A. By way of example, anaerobic digestion of tomato leaves has generated between 0.13 and 0.26 L CH₄/g COD of biomass.

In some embodiments of the process, the fertilising sludge E4 may have a high- quality balance of nutritive elements and minerals and may be directly reintroduced into the greenhouse culture. In other embodiments, the fertilising sludge is preferably treated in order to balance, reduce or convert certain of its components. In one aspect, the fertilising sludge is subjected to aerobic treatment S1 prior the reintroduction into the greenhouse. Aerobic treatment generates humic compounds and the fertilising sludge so treated may also be referred to as a "humic composition" S4. It should also be understood that heavy metals should be separated from the sludge E4 when their maximum concentration is achieved. The fertilizing sludge E4 may also be recuperated by a waste management system and stocked before its reintroduction into the greenhouse culture A.

The digested solution E3 (also be referred to as "digestion effluents") is preferably sampled at different levels and intervals, as a function of its ionic composition. The digested solution is eventually filtered H1 to remove particles in suspension. In some cases, certain ions can be separated by membrane filtration, SO₄/NH₄ precipitation or fixation. This helps to provide an adequate equilibrium of the nutritious fertilizing effluents E3 and to avoid the physiological disorders due to competition between the absorption of ions by the plants. The digestion effluents E3 are stabilized and may be stocked H2 in reservoirs in order to limit the losses of nitrogen by denitrification and ammonia volatilization. Alternatively, when the certain environmental standards apply, the digestion effluents may be dumped or discharged into oxygenated ponds in order to reduce the ammonium nitrogen levels to be treated. The digestion effluents E3 may then be pre-treated I prior to undergoing nitrification J, which will be further described below. Preferably, this pre-treatment step I allows optimal conditions to be adopted for the nitrifying bacteria active during the nitrification step. These optimal conditions may be for pH, alkalinity, NH₃, HNO₂, NO₂, NH₄ organic load, temperature, oxygen demand, toxic components, such as heavy metals amine proteins, tannins, phenolic compounds, etc.

Nitrification

Still referring to Figure 1 , various process streams may be subjected to nitrification J. In one embodiment of the process, only the digested solution undergoes nitrification to produce an organic liquid fertiliser R. In another embodiment of the process, the digested solution and the marsh effluent both undergo nitrification J.

Nitrification enables the biological oxidation of ammonia contained in the digested solution and other input effluents into nitrites followed by oxidation of the nitrites into nitrates. As mentioned above, the digested solution E3 may undergo pre-treatment steps such as filtration, stocking, and removal of certain unwanted components, to prepare it for nitrification J. It should be understood that the digested solution E3 may be combined with other streams such as drainage water, marsh effluent, aquafauna effluents, dilution water, chemical additives, etc., to produce a mixture for nitrification. It should also be understood that nitrification may occur in a single nitrification unit J, multiple units in series or multiple units for treating different input effluents.

Greenhouse organic waste that has been anaerobically digested contains a high quantity of ammonia and thus the nitrification is performed so as to address this challenge. In one embodiment of the process, the nitrification treats an input mixture having nitrogen load of 500 mg/L or higher. In some embodiments of the process, the preceding steps including marsh filtering and anaerobic digestion are managed so as to minimise nitrogen loss and while this allows retention of nutritive nitrogen compounds in the process it also results in high concentrations of ammonia which can disrupt or encumber plant growth. The reusable components generated by the nitrification J have a low concentration or are exempt from ammonium, nitrite and pathogens so as to not adversely affect the greenhouse culture upon recycling. In one embodiment of the process, the nitrification is performed so as to limit exposure to atmosphere, such as operating in a closed reactor, so as to minimise loss of nitrogen compounds through denitrification or ammonia volitisation. The nitrification may also benefit from pre-treatment steps of dilution to adjust the ammonia concentration to the optimum level or proportion. The reactor is preferably a suspended-carrier biofilm reactor or moving-bed biofilm reactor, having inert media and nitrifying bacteria forming a biofilm on the media. The nitrification generates solid matter such as sloughed biofilms that are recovered by filtration or decantation for reintroduction into the greenhouse culture. The nitrification is managed to withstand ammonia concentrations above 500 mg/L and to produce the organic liquid fertiliser having a nitrate/ammonia ratio above 9/1. Managing the nitrification may be performed based on the carbon/nitrogen ratio, the nitrate/ammonia ratio and/or the pH. Based on such factors, one may adjust the hydraulic residence time, dilution prior to the nitrification, pH and/or the quantity of inert media (% filling) within the nitrification reactor. For instance, the hydraulic residence time is preferably controlled or designed to avoid wash-out of nitrifying bacteria from the system while maintaining optimal and stable nitrification.

In one embodiment of the process, the C/N ratio is managed to improve the performance of the nitrification. In cases of high organic content, aerobic heterophil micro-organisms grow much faster (10 to 20 times) than nitrifying bacteria and occupy the surface available on the media to the detriment of the nitrifying bacteria, which reduces the performance of nitrification. In addition, accumulation of sludge attributable to the rapid growth of heterophiles reduces the active volume of the reactor, results in waste that is undesirable for a stable nitrification unit. The nitrification reactor unit may operate at lower C/N ratios and/or at dilution levels that promote nitrifying over heterophile activity and growth. It should also be understood that high C/N ratios in the reactor may also be appropriate by managing other process conditions.

In one embodiment of the process, the nitrification reaction conditions allow reducing the ammonium content to about 5-20% and increasing the nitrate content to about 80-90%, in relation to total nitrogen content.

In some embodiments of the process, the pH of nitrification reactors is maintained relatively constant (pH about 6 to 7) following the addition of an alkaline substance in order to ensure an optimal activity of the Nitrosomonas and Nitrobacter genus of bacteria and to avoid the precipitation of phosphates. In the case of elevated concentrations of phosphate, the pH may be maintained at a higher level in order to provoke precipitation of these ions, but will be inferior to about 8.5 in order not to impede the process of nitrification.

In one embodiment of the process, the nitrification is operated in continuous mode the facilitate nitrification and reduce denitrification. The overall process may therefore be a hybrid batch-continuous process, with the organic waste recovery and anaerobic digestion occurring in batch mode and the marsh filtration and nitrification occurring in continuous mode. Also preferably, the nitrification is operated to minimise production of sludge in the reactor, which allows improved circulation of the media and convective mass transfer, prolongs the window of continuous operation and generally facilitates management of the process and cost reduction. The temperatures are preferably in the range of about 15-25⁰C, which is the normal night/day range of greenhouse conditions. Keeping the nitrification in this temperature range also reduces the need to cool the resulting liquid organic fertiliser recycled back into the greenhouse culture.

Reintroduction of components into greenhouse culture

After nitrification, the liquid organic fertiliser may undergo finishing treatments before reintroduction into the greenhouse culture.

The organic liquid fertiliser may bedecanted or filtered K1.K2 to collect the crude matter or the susmended matter resulting from nitrification, which may be generally referred to as "sloughed biofilms" These soughed biofilms may be stored K3 and/or used as a source of organic fertilizer For instance, they may be used for soil improvements for the greenhouse cultures A The effluents resulting from the nitrification may also undergo phosphate removal L and/or phosphorus removal The dephosphorised effluents may then undergo membrane filtration M1 (phosphorous/NO₃) It should be understood that the use of selective environments, for example clinkers, can reduce the anionic concentration which is found in excess in the effluents resulting from nitrification The effluents may then be further filtered M1 before their reintroduction into the fertilization solution basin N where they will form part of the liquid organic fertiliser

It should be understood that in this fertilisation solution basin or tank N, the composition of the liquid organic fertiliser may be adjusted by the addition of organic and/or nutritious elements The pH and the salinity are adjusted according to the needs of the culture into which the nitrified liquid fertliser will eventually be introduced The liquid organic fertiliser emitted by the fertilization solution basin may then be balanced and inoculated with beneficial or probiotic agents P for the greenhouse culture A and for the protection against pathogenic agents such as bacteria of the species Trichoderma, Bacillus, Pseudomonas, Streptomyces, and Gliocladium These probiotic agents thus increase the tolerance of the culture A to certain diseases such as phythium As such, the nitrified effluents can be transformed into end-products for recycling as growth enhancers and/or liquid organic fertilizer R in the culture A

The organic liquid fertiliser may be cooled to between about 18⁰C and about 25⁰C (preferably 18-23⁰C) prior to reintroduction into the greenhouse culture A, if need be This allows an optimal temperature of the irrigation water (often 18 to 23⁰C) which flows through the greenhouse, an elevated concentration in oxygen, especially during the summer months The cooling may be performed by a water chiller or a cooling tower, for example In order to avoid insufficient inflow of oxygen at the level of the rhizosphere, which brings about ridiculer asphyxia and consequently limited growth of the plants, the reintroduction should be closely managed. In addition, intense microbial activity in organic environments increases the demand in oxygen in this environment and important CO₂ fluxes are observed. Two factors that indicate or determine the presence of organic stress are air porosity of the culture environment and gas transfer characteristics such as gas diffusivity and trouble, which are specific to each culture environment. In order to favour microbial life and radicular activity, an oxygen injection system Q injects oxygen into the irrigation water and advantageously into the culture A. It should also be understood that other streams from the process may be added to the liquid organic fertiliser, if need be, to prolong, delay or otherwise complement its effect upon reintroduction into the greenhouse culture. Various streams and effluents such as those from an aquafauna culture can undergo filtration U and dephosphoration L before being mixed into the reusable components resulting from the fertilization step N, cooled O, inoculated P, enriched with oxygen Q and reintroduced into the greenhouse culture A as part of the liquid organic fertilizer R.

In one embodiment of the process, the greenhouse culture comprises solid culture media and the organic liquid fertiliser is thus reintroduced by flowing it within channels interfacing with the culture media to allow diffusion into the culture media. This preferred method of reintroduction allows even and efficient addition of the liquid fertiliser into the solid media. The diffusion of the liquid fertiliser into the solid media is substantially radial unlike spraying or surface-addition techniques which are substantially vertical. Liquid fertiliser is readily absorbed by plants and thus presents advantages over solid fertiliser. Greenhouse cultures using solid media may be vegetable, ornamental or medicinal cultures for example.

In another embodiment of the process, the particle size in the organic liquid fertiliser is maintained below about 200 microns prior to reintroduction into the greenhouse culture and reintroducing the organic liquid fertiliser by an irrigation system. Irrigation systems are efficient methods of introducing liquids into greenhouse cultures and may be retrofitted to use the liquid organic fertiliser in connection with the present invention. Thus, the liquid fertiliser may be produced by the process of the present invention and be efficiently introduced into an existing greenhouse infrastructure via an irrigation system that has particle size constraints.

It should also be mentioned that the solid and liquid organic wastes are preferably recovered from a greenhouse culture that used the liquid organic fertiliser. In such continual closed-loop embodiments of the process, the nutritive and fertilising elements are kept in the system. In various embodiments of the process, the process is controlled by monitoring parameters selected from the pH, salinity, turbidity, particle size, and concentration of nitrogen, phosphorus, potassium and sulfur compounds. Based on these parameters, one may manage the various unit operations and temporarily stock at least some process streams selected from the liquid organic waste, the solid organic waste, the digested solution, the biogas, the fertilising sludge, the marsh effluent, the organic liquid fertiliser, the fertilising sludge and/or water effluent streams. The stocked streams may be release when required into corresponding process steps including the anaerobic digestion, the marsh filtration, the nitrification or the greenhouse culture reintroduction. In addition, the biological demand in oxygen (BDO₅), the chemical demand in oxygen (CDO) and nutrient content may also be monitored. A monitoring system may be put into place in order to ensure the optimal performance of the process. The process is operated efficiently from both biological and environmental points of view and achieves minimal loss of nutrients, recycling of carbon and water and increased energy efficiency, for example.

The process streams may be transported via transport systems including pipes and pumps provided with valves, similar to the systems generally used in greenhouse irrigation systems. The solid or non-pumpable mixtures may be transported by known solid transport systems such as conveyors or vehicles, if need be. The process for the recycling of organic waste gives new value to greenhouse production and allows the use of organic waste resulting from this production. In this fashion, the otherwise wasted biomass can be used as a source of energy (methane CH₄) and to enrich the greenhouse culture in CO₂ thereby increasing productivity by surface unit cultivated and, consequently, improving the energy efficiency of the cultures (g/MJ). The process allows reusing components in the greenhouse, production of solid organic amendments for the cultures, recycling the water for irrigation of the cultures, eliminating undesirable pathogens and toxins for the cultures and for human health, eliminating heavy metals and degrading synthetic or organic pesticides and antibiotics, and using the effluents of aquafauna cultures such as fish farming as a source of fertilizers for the greenhouse cultures. The process may be implemented gradually to an existing conventional greenhouse culture to wean it off chemical fertilisers.

Contrary to existing systems, embodiments of the process are adapted to high concentrations of cellulose, lignin, nitrogen and sulphur and include microbiological processes which are anaerobic and aerobic.

Some of the embodiments of the process of the present invention provide advantages as summarised and listed below:

^■ Provide a source of biogas for the heating of the greenhouses, a source of CO₂ for culture growth, a source of fertilizers and soil improvements of organic origin for the cultures.

^■ Allow the recycling of carbon, nutrients and water for irrigation of the cultures.

^■ Allow the elimination of pathogenic agents, and more specifically at the stage of digestion, nitrification and/or filtration by the filtering marshes or other processes of filtration.

^■ Allow the reduction of the incidence of disease as well as physiological disorders in culture.

^■ Produce reusable products which can be used as liquid fertilizer for soil and hydroponic systems or for foliar applications.

^■ Provide easy adaptability to covered culture areas of one hectare and more.

^■ Provide easy adaptability to the various volumes of organic waste to be treated._a ■ Overcome the problems involved in chemical fertiliser having too high concentration of organic matter, as has been encountered in the field.

^■ Avoid wasteful spreading on anaerobic digestion effluents onto fields and allow elimination or adequate reduction of mineral elements present in the treated organic waste. ■ Provide a complete process for generating solid and liquid nutritive components that can be reintroduced into the greenhouse culture, at levels that are adequate for biomass production in greenhouses.

^■ Avoid the addition of calcium nitrate and magnesium to the fertilising solution, but rather achieve adequate nitrate/ammonium ratio without such chemical addition.

■ Provide a low energy intensive process in which the filters and irrigation systems do not tend to clog.

■ Performing anaerobic digestion at stable, cheap, easy conditions, operating at low temperature (5° to 25⁰C), producing a significant quantity of organic fertilizer and biogas (CH₄ and CO₂) and reducing N₂O emission. In addition, after converting the N₂O into NH₄, which may be harmful for vegetable culture, providing nitrification converting and recycling the nitrogen biogas.

^■ Providing efficient dimensions of the equipment and of the basins, volume of the organic waste introduced into the process, residence time in the process. The pre- and post- treatments may be defined in function of the surface area of culture.

■ Providing soil improvements or fertilizers which include humic compounds and organic acids that provide beneficial and antagonistic organisms for the growth of plants (PGPR, PGPF, PGPB, phytostimulators, etc.) and offer the above-ground cultures a balanced environment, one which is favourable to the productivity of cultures and to the quality of products derived therefrom, while avoiding the use of synthetic fertilizers, pesticides, and/or synthetic growth hormones.

^■ Providing a process that can use greenhouse cultures of different types based on local available resources, climatic conditions of the geographical region in which the cultures are grown, the quality of the water and the know-how of the lines of production. The out-of-ground substrates used may have a porosity of approximately 25 to 40%, but can also have a superior porosity when natural local components are used. These local components may include, for instance, sawdust, bark or volcanic rock.

^■ Allowing drainage waters of the process to be brought to a collection basin, treated and reintroduced into the culture. ■ Enriching the rhizosphere with the reusable components and oxygen to allow improved biological activity of the culture and ensure proper growth of the culture following an increase in the level of mineralization and the development of microflora and microfauna.

^■ Managing the irrigation and of fertilization based on tensiometry, soil (including that of out-of-ground culture media), water content, and/or salinity in the mobile and non-mobile phases of the culture media, the need for evapotranspiration of the culture, culture status and the quality of the culture desired.

^■ Avoiding laguna that cause significant loss of nitrogen into the atmosphere and hence loss of fertilizer.

^■ Using of liquid organic fertilizer which is easier to recycle and easily absorbable by the plants, and reducing the cost to produce such liquid fertilizer.

EXAMPLES Example 1

A marsh filterting system was contructed comprising three independent cells inseries. Each unit measured 2.5 m wide, 5 m long and 1.2 m deep. The bottom of each cell was lined with polyethylene. A central drain covering the entire area of each unit was installed at the bottom and connected to a container of 7 m³ serving as a pumping unit and a collection unit of treated effluents. Two systems bringing effluents to the marshes were installed. The first was for winter and was installed at 0.6 m depth and comprised a PVD pipe of 2.5 cm with perforations each 30 cm. This first tube was surrounded by an external tube of 3 inch diameter also having perforations every 30 cm. This first distribution system was covered with 0.6 m of additional sand. A second distribution system was installed on the surface of the marsh for the summer season.

The effluents were derived from a tomato plant culture (69.3 m2 of culture per marsh). The drainage effluents from the tomato culture were gravity fed to a reservoir and then pumped to a collection tank. The effluent was uniformly distributed over the surface of the first marsh cell, percolated therethrough, recuperated at the bottom and then pumped to the surface of the next marsh cell. In summer, 2250 L may be treated by a marsh, resulting in a retention time of about 2 days per marsh cell for a total of 6 days. Example 2

The following is data on tomato leaves that can be the solid organic waste of a tomato greenhouse culture :

On 4500 kg/ha/week, 10% is solid matter and 90% is water, with about 1.2-1.7 g C per leaf.

Example 3 For biogas production from anaerobic digestion of tomato plant waste, there is about 26 ITi³CI-I₄ per ton of leaves, 1 17 m³ CH₄ per week per hectare, which corresponds to 234 kg of CO₂ and 1 ,002,690 Kcal. It should also be noted that the composition of the biogas may vary in CO₂, CH₄ and H₂S content.

Example 4 The following is data on anaerobic digester effluent (digested solution) from a tomato culture waste:

This disgest solution was then nitrified. Example 5

Two constructed marsh systems that were constructed and tested were a three- cell vertical percolation outdoor marsh system having 43 m³ and 2250 L/day capacity, and experimental marshes using phragmite, cattail and non-vegetalised cells having 0.88m³ and 22 L/day capacity. Figures 3a-3d show results for the three-cell marsh system, and Figures 4a-4c show results for the other experimental marshes. Example 6

Figures 5a-5d show the effect of a simple sugar such as sucrose on marsh filtering cells.

Example 7

Figure 6 shows more data regarding sucrose addition. Definitions

"Continual multiphase recycling" means that both solid and liquid waste phases are recovered from the greenhouse culture and both solid and liquid products are recycled back into the greenhouse culture after treatment. It should be understood that the recovered or recycled "liquid" may also contain some amount of solids that may be suspended and that the recovered or recycled "solid" may be in the form of a slurry- or mid-like material containing some liquids.

"Anaerobic digestion" allows the pre-treated digestable mixture to be transformed into a digested solution, biogas and a fertilising sludge. It refers to a process in which micro-organisms break down biodegradable material in the absence of oxygen.

Organic waste" includes all types of organic waste such as biomass, residual biomass, wastewater, non-fossilized organic matter such as living and recently dead biological material and the like. It includes plant and/or animal matter stemming from greenhouse culture environments and effluents thereof, aquafauna farming effluents as well as agrifood biomass such as mud, sludge, algae and other plant-like materials having energetic and fertilizing characteristics and/or agricultural or ligneous biomass. "Marsh filtering" means a process using a natural or constructed formation comprising hydrolic soil capable of producing a marsh effluent and marsh biomass. Such formations may be referred to as marshes, wetlands, swamps and bogs that enable a reducing environment, nutrient cycling, retention of particules, removal of certain elements and compounds, intake and release of organic carbon.

"Nitrification" means a process involving the oxidation of ammonia with oxygen into nitrite, followed by the oxidation of nitrite into nitrate. Nitrification involves bacteria and ammonia oxidizing archaea to produce the organic liquid fertiliser in this process. "Denitrification" refers to the process of converting biologically available nitrogen into nitrogen-based gases. The nitrogen-based is biologically unavailable, except for nitrogen fixing bacteria. Denitrification is also to be understood in the context of the present invention as being a reaction that can tend to occur in filtering marshes because of increased nitrate availability stemming from the use of fertilizers which can cause eutrophication.

Although preferred embodiments of the present invention have been described in detail herein, it is to be understood that the invention is not limited to this embodiment and that various changes and modifications could be made without departing what has actually been invented.

Claims

1. A process for continual multiphase recycling of solid and liquid organic waste for a greenhouse culture, comprising: recovering the solid organic waste and the liquid organic waste from the greenhouse culture; pre-treating the solid organic waste to produce a pre-treated digestable mixture; anaerobically digesting the pre-treated digestable mixture to produce a digested solution, biogas and a fertilising sludge; filtering the liquid organic waste through a filtering marsh to produce a marsh effluent and marsh biomass; subjecting the digested solution to nitrification to produce an organic liquid fertiliser; and reintroducing the fertilising sludge, the marsh effluent and the organic liquid fertiliser into the greenhouse culture for biomass production.

2. The process of claim 1 , wherein a portion of the liquid organic waste is anaerobically digested with the pre-treated digestable mixture.

3. The process of claim 1 or 2, further comprising aerobically treating the fertilising sludge so as to produce humic compounds therein prior to reintroduction into the greenhouse culture.

4. The process of any one of claims 1 to 3, further comprising combusting the biogas to generate energy for the greenhouse culture.

5. The process of claim 4, further comprising recovering carbon dioxide from the combustion and reintroducing the carbon dioxide into the greenhouse culture.

6. The process of any one of claims 1 to 5, wherein filtering through the marsh comprises adding a carbon nutrient source to the marsh.

7. The process of claim 6, wherein the carbon nutrient source is a simple sugar.

8. The process of claim 7, wherein the simple sugar is sucrose.

9. The process of any one of claims 1 to 8, wherein the marsh filtering is performed in at least one marsh cell that has an air-exposed surface area sized to reduce formation of nitrogen-oxygen-based greenhouse gases from the at least one marsh cell.

10. The process of any one of claims 1 to 9, wherein the marsh filtering is performed in at least one marsh cell comprising an upper non-immersed layer and a subterranean immersed filtering layer.

11. The process of any one of claims 1 to 10, further comprising recovering at least a portion of the marsh biomass and anaerobically digesting the portion.

12. The process of claim 11 , wherein the portion of the marsh biomass is anaerobically digested with the pre-treated digestable mixture for recycling therewith.

13. The process of any one of claims 1 to 12, wherein the marsh effluent is subjected to nitrification prior to reintroduction into the greenhouse culture.

14. The process of claim 13, wherein the marsh effluent is subjected to nitrification with the digested solution for recycling therewith as the organic liquid fertiliser.

15. The process of any one of claims 1 to 14, wherein the marsh biomass is selected from the group consisting of phragmite australis reeds and typha plants.

16. The process of any one of claims 1 to 15, wherein the marsh filtering comprises serial filtering in multiple marsh cells.

17. The process of claim 16, wherein each marsh cell is constructed with an impermeable membrane defining a bottom and side walls thereof.

18. The process of claim 16 or 17, wherein the multiple marsh cells comprise a pre-treatment marsh cell containing sulphate-reducing microflora.

19. The process of any one of claims 16 to 18, wherein the multiple marsh cells comprise an ammonium-reducing marsh cell.

20. The process of any one of claims 16 to 19, wherein the multiple marsh cells comprise a phosphorus-capturing marsh cell.

21. The process of any one of claims 1 to 20, further comprising limiting exposure to atmosphere during the nitrification to reduce denitrification and ammonia volatisation.

22. The process of any one of claims 1 to 21 , further comprising diluting the digested solution and/or the marsh effluent to reduce the concentration of ammonium prior to the nitrification.

23. The process of any one of claims 1 to 22, further comprising enclosing the digested solution prior to the nitrification to avoid denitrification and ammonia volatisation.

24. The process of any one of claims 23, wherein the nitrification is performed in a nitrification unit comprising a suspended-carrier biofilm reactor having inert media and nitrifying bacteria forming a biofilm thereon.

25. The process of claim 24, further comprising managing the nitrification to withstand ammonia concentrations above 500 mg/L and to produce the organic liquid fertiliser having a nitrate/ammonia ratio above 9/1.

26. The process of claim 25, wherein managing the nitrification is performed based on the carbon/nitrogen ratio, the nitrate/ammonia ratio and/or the pH, and comprises adjusting hydraulic residence time, dilution prior to the nitrification, pH and/or the quantity of inert media within the nitrification unit.

27. The process of any one of claims 1 to 26, wherein the nitrification generates solid matter that is recovered by filtration or decantation for reintroduction into the greenhouse culture.

28. The process of claim 27, wherein the solid matter comprises sloughed biofilms.

29. The process of any one of claims 1 to 28, further comprising cooling the organic liquid fertiliser to between about 18⁰C and about 25⁰C prior to reintroduction into the greenhouse culture.

30. The process of any one of claims 1 to 29, further comprising inoculating the organic liquid fertiliser using probiotic agents and balancing the organic liquid fertiliser prior to reintroduction into the greenhouse culture.

31. The process of any one of claims 1 to 30, further comprising enriching the organic liquid fertiliser with oxygen prior to reintroduction into the greenhouse culture.

32. The process of any one of claims 1 to 31 , wherein the greenhouse culture comprises solid culture media and reintroducing the organic liquid fertiliser comprises flowing the organic liquid fertiliser within channels interfacing with the culture media to allow diffusion into the culture media.

33. The process of any one of claims 1 to 32, further comprising controlling the process by: monitoring parameters selected from the pH, salinity, turbidity, particle size, and concentration of nitrogen, phosphorus, potassium and sulfur compounds; temporarily stocking at least some process streams selected from the liquid organic waste, the solid organic waste, the digested solution, the biogas, the fertilising sludge, the marsh effluent, the organic liquid fertiliser, the fertilising sludge and/or water effluent streams, based on the parameters; and releasing the stocked streams when required into corresponding process steps including the anaerobic digestion, the marsh filtration, the nitrification or the greenhouse culture reintroduction.

34. The process of any one of claims 1 to 33, further comprising maintaining the particle size in the organic liquid fertiliser below about 200 microns prior to reintroduction into the greenhouse culture and reintroducing the organic liquid fertiliser by an irrigation system.

35. The process of any one of claims 1 to 34, conducted in hybrid batch- continuous mode, wherein recovering the solid and liquid organic waste and anaerobic digestion occur in batch mode while the marsh filtration and nitrification occur in continuous mode.

36. The process of any one of claims 1 to 35, wherein the greenhouse culture is selected from the group consisting of vegetable cultures, ornamental cultures, medicinal cultures, algal cultures and aquacultures.