NL1037223C2

NL1037223C2 - Method for treating vegetable, fruit and garden waste.

Info

Publication number: NL1037223C2
Application number: NL1037223A
Authority: NL
Inventors: Willem Elsinga; Gerrit Jacobus Jong
Original assignee: Elsinga Beleidsplanning En Innovatie B V; Jonger Man B V
Priority date: 2009-08-24
Filing date: 2009-08-24
Publication date: 2011-02-28

Description

Method for treating vegetable, fruit and garden waste

The present invention relates to a method and waste treatment facility for treating vegetable, fruit and 5 garden waste. Furthermore, the invention relates to a method of providing a greenhouse with carbon dioxide and/or heat obtainable from fermenting and composting vegetable, fruit and garden waste.

At present, vegetable, fruit and garden waste, 10 herein VFG waste, can be recycled into useful products by at least two distinct industrially applied biological degradation processes, being anaerobic fermentation and composting.

Anaerobic fermentation as used in the organic 15 waste-treatment industry is a biological process mediated by micro-organisms, primarily bacteria, which is used to produce biogas as a source of energy. This anaerobic fermentation process comprises several stages of decomposition of organic matter including hydrolysis, 20 acidogenesis, acetogenesis and methanogenesis. During this fermentation process, biogas, primarily methane and carbon dioxide, is produced as well as a rather liquid residue, termed digestate. The fermentation process can, depending on the temperature at which fermentation takes place, be 25 divided into thermophylic, mesophylic and phychrophylic fermentation.

The second process suitable for treating VFG waste is composting which is a degradation process by which organic matter is partly decomposed into smaller organic 30 molecules. On an industrial scale, this aerobic process is performed by micro-organisms, primarily bacteria and fungi. During the course of this process heat, water, carbon dioxide and a rather dry residue, termed compost is 1037223 2 obtained.

Although both processes are applied in the waste processing industry as a means to treat organic waste, the actual implementation, application and/or optimisation on an 5 industrial scale of the two technologies as a combination cannot be accomplished in a straight-forward manner. There are many aspects that need to be considered when attempting to optimize the treatment of VFG waste in order to achieve an economically and industrial applicable technology which 10 is suitable for the treatment of organic waste. Such aspects to consider include the type, size, amount or nature of the organic waste which is offered or supplied to the treatment facility. Moreover, seasonal changes in the type, size, amount and nature of organic waste which is supplied add 15 another layer of complexity which treatment facilities face. Furthermore, fermentation and composting are naturally occurring processes, as such applied on a very heterogeneous and variable source of solid organic waste which makes it unclear at times how certain aspects of the treatment 20 process can be optimised. Consequently, it is technically challenging to design a treatment facility which allows year-round predictable processing of a highly variable and seasonally fluctuating supply of raw organic matter which can be operated at economically competitive rates.

25 Another problem which the VFG waste treatment industry currently faces is that during the treatment of said municipal organic waste, especially due the pretreatment of digestate to make it suitable for composting, an undesired wet fraction is obtained, the disposal of which 30 is. costly and generally restricted by local jurisdiction. Furthermore, the presently practiced pre-treatment of digestate brings along high investments, high running costs and high maintenance costs which are all critical points of 3 concern in this sensitive, vulnerable process for which downtime needs to be avoided.

Therefore, it is an object of the present invention to provide a method for treating vegetable, fruit 5 and garden waste. Furthermore, an object of the invention is to provide a treatment facility for the treatment of vegetable, fruit and garden waste. Also, an object of the present invention is to provide a method for providing a greenhouse with carbon dioxide and/or heat.

10 The above object, amongst others, is achieved by a method and installation as defined in the appended claims.

Specifically, the present invention relates to a method for treating vegetable, fruit and garden waste, comprising the steps of: 15 a) fermenting vegetable, fruit and garden waste, b) adding compost and/or vegetable, fruit and garden waste to the at least partially fermented waste, c) composting the thus obtained mixture to obtain compost.

20 An advantage of the present invention is that it is now possible to compost at least partially fermented VFG waste without the requirement to pre-treat the at least partially fermented VFG waste prior to composting thereof.

Present day treatment of VFG waste comprising 25 fermentation and subsequent composting, generally results in the formation of a fermentation-derived digestate which is not suitable yet for composting thereof. In order for this digestate to become suitable for composting, it needs to be treated such that a dry fraction is obtained which is 30 suitable for subsequent composting thereof.

The pre-treatment as presently practiced is generally achieved by applying pressure on the digestate, for example by using a screw press, as a consequence of 4 which water drains from the digestate resulting in the provision of what is commonly termed as a dry fraction and a wet fraction. This dry fraction is suitable for composting. The wet fraction is a highly undesirable by-product, the 5 disposal of which is a major debit for the organic waste treatment industry. Besides being costly, disposal of this wet fraction, e.g. as fertilizer or landfiller, is not always allowed as local prevailing jurisdiction may prevent or restrict such disposal.

10 As the digestate obtained from fermentation of VFG

waste can be composted without pre-treatment, the method according to the present invention is more cost-effective and efficient than methods which do require such pretreatment of digestate.

15 Another advantage of the present invention is that in essence only compost, biogas, heat and water is obtained from the treatment of VFG waste. The present invention thus allows for the treatment of VFG waste without the generation of from digestate-derived wet fraction. The digestate-20 derived wet fraction concerns a major debit for the organic waste-treatment industry as this undesired by-product cannot be disposed of at economically favourable rates. Therefore, as the method according to the present invention only results in the production of heat, water, compost and 25 biogas, problems related to the disposal of digestate-derived wet fraction are prevented.

VFG waste herein comprises organic, biodegradable waste from domestic, municipal and/or industrial origin, such as from the food industry, catering industry, 30 industrial scale greenhouses, not excuding privately-owned greenhouses. VGF waste herein includes fruits, vegetables, kitchen waste, leftovers from meals, coffee grounds, paper, cardboard, eggshells, garden waste such as plants, flowers, 5 wood, leaves, grass, animal faeces, or other animal-derived waste such as meat, animal fat and the like. Although the VFG waste comprises primarily of organic matter, it generally also comprises, to a lesser extent, inorganic 5 matter, such as soil, sand, stones and the like.

VFG waste herein includes both VFG waste which is source-separated or non-source-separated. VFG waste not separated at the source is generally referred to as Organic Wet Fraction, or OWF. Even though differences may exist 10 between the presence of pollutants in compost derived from source-separated or non-source-separated VFG waste (or OWF), the method according to the present invention provides a solution to the treatment of VFG waste in general. Consequently, VFG waste herein is meant to include OWF.

15 Production of compost derived from source- separated VFG waste has an advantage for the organic waste treatment industry as this compost is of high quality and can readily be used in applications like agriculture. Separation of organic waste after collection at the source 20 results in organic waste which can readily be composted, but compost derived from such waste is generally polluted with compounds such as heavy metals or other impurities, resulting in compost of lower quality. Generally such compost needs to be disposed of, contained or dumped, at 25 high costs, in such a manner that it is not exposed to the environment. Irrespective of such differences, any VFG waste can be treated and composted according to the present invention.

In a preferred embodiment, the at least partially 30 fermented waste according to step b) is digestate obtained from fermenting VFG waste.

According to the present invention, the fermentation of VFG waste will proceed such that 6 considerable amounts of biogas (primarily methane and C02) are produced and that a fermented residue, or digestate, is produced. Preferably, such a digestate as meant herein is a residue which is derived from the, in essence, complete 5 fermentation of VFG waste. Such fermentation is preferably thermophylic fermentation but can also be mesophylic or psychrophylic fermentation. Suitable thermophylic fermentation conditions include, but are not limited to: continuous and/or evenly spread, batch-wise feeding of the 10 fermentation tank, or digester; maintaining the fermentation process at a temperature of 50-60°C, preferably approximately 55°C; maintaining the humidity of the content of the fermentation tank between 60-80%, preferably approximately 70%; and fermenting for a period of between 8 15 to 30 days, preferably approximately 14 days. A digestate as meant herein may comprise any amount of dry matter of between 15 to 40, preferably 20 to 30 percent by weight of the digestate.

Besides the use of digestate for composting, it is 20 also possible to use VFG waste for composting which is at least partially fermented. As the invention relates to composting of digestate but also allows for at least partially fermented VFG waste to be composted, these two terms herein can be interchanged, unless specifically stated 25 otherwise.

In another preferred embodiment, the mixture comprising compost and/or VFG waste comprises, prior to composting, from 35% to 55%, preferably from 40% to 50%, more preferably from 42% to 48%, most preferably from 44% to 30 46% dry matter by weight of said mixture. At these ranges of dry matter, the composting of said mixture proceeds in a suitable manner resulting in the production of compost, heat and water in a preferred period of time.

7

Technically however, there appears to be no upper limit to the percentage dry weight of the mixture.

Therefore, in a suitable embodiment, mixtures comprising compost and/or VFG waste comprising, prior to composting, of 5 at least 35%, preferably at least 40%, more preferably at least 42%, most preferably at least 44% dry matter by weight of said mixture are used. An advantage of using the herein disclosed ranges or lower limits of dry matter is that the mixtures can comprise higher amounts of digestate, in 10 particular when the fraction compost and/or VFG waste comprises a high dry matter content. In this way, more digestate can be composted by the same composting facility, thus increasing the overall throughput of the composting process .

15 In yet another preferred embodiment, the weight of digestate divided by the weight of compost and/or vegetable, fruit and garden waste of said mixture is, prior to composting, between 0.3 to 2.0, preferably 0.4 to 1.5, more preferably 0.5 to 1.5, most preferably 0.6 to 1.2 or about 20 0.7. Composting of mixtures comprising digestate, compost and/or vegetable, fruit and garden waste at these ranges allow for mixtures to be processed comprising higher amounts of digestate, in particular when the fraction compost and/or VFG waste comprises a high dry matter content. In this way, 25 more digestate can be composted by the same composting facility, thus increasing the overall throughput of the composting process.

Another advantage of the present invention is the flexibility of the treatment process which allows varying 30 the amounts and nature of the VFG waste as supplied to the waste treatment facility. For example, the mixture which can be composted in step c) can comprise a wide range of percentages dry matter of the organic material to be 8 composted. This allows to compost digestate without separating it into a wet and dry fraction. It also allows flexibility in the amounts of compost and/or VFG waste to be added to the fermented waste of step a) for composting.

5 Another advantage of this flexibility is that the treatment process, and thereby the treatment facility, as a whole can deal with seasonal changes in the supply of VFG waste. When the fermentation installation, or digester, would be used at maximal capacity, the system allows surplus 10 VFG waste to be composted without prior fermentation. This flexibility also allows for the implementation of a fermentation installation which is designed to process the lowest seasonal supply of VFG waste instead of the highest seasonal supply thereof. As a fermentation installation is 15 one of most expensive parts of such a treatment facility, it is advantageous to use the method according the present invention which provides such flexibility.

In yet another preferred embodiment, the mixture of step c) is mixed prior to composting thereof. A suitable 20 mixing means for mixing thereof is a compost mixer. Mixing of the compost and/or vegetable, fruit and garden waste with the at least partially fermented waste increases the homogeneity of the mixture before composting. Mixing thus supports an evenly and homogenous composting process. During 25 the test as described in Example 2 it was surprisingly found that the use of mixing equipment increased the bulk density of the mixture, which was premixed with a shovel, from about 700 kg/m3 to about 8 50 kg/m3. This increases the capacity of the available space in the composting facility with at least 30 20%.

In a preferred embodiment, the composting of the mixture of step c) is for a period of 4 to 40 days, preferably 14-16 days.

9

In yet another preferred embodiment, the compost from step c) is added in step b). An advantage of using the compost of step c) in step b) is that compost from step c) is allowed to compost further leading to a higher stability 5 of the resulting compost and to optimal use of the available material in the treatment facility.

As the processing of VFG waste preferably occurs in a single waste treatment facility, the at least partially fermented waste or digestate according to step b) is 10 preferably fermented VFG waste from step a).

In yet another preferred embodiment, the at least partially fermented waste or digestate comprises 20 to 38, preferably 24 to 34, more preferably 26 to 32 percent by weight dry matter.

15 In yet another preferred embodiment the compost comprises 40 to 90, preferably 50 to 80, more preferably 60 to 70 percent by weight dry matter. Said compost can be the compost added in step b) and/or the compost from step c).

In yet another preferred embodiment, the VFG waste 20 comprises 25 to 60, preferably 30 to 50 percent by weight dry matter.

In yet another preferred embodiment, the VFG waste of step b) is in essence fresh or unfermented VFG waste. Fresh or unfermented VGF waste herein means VFG waste which 25 has not been subjected to an industrial fermentation and/or composting process. As fermentation and composting are naturally occurring processes and as the VFG waste is generally disposed of several weeks prior to collection at the waste treatment facility, the VFG waste may show signs 30 of fermentation or perhaps composting. Despite such signs, such VFG waste is considered herein as fresh, unfermented VFG waste .

In yet another preferred embodiment, the VFG waste 10 of step a) is sieved and/or shredded prior to fermentation thereof. Sieving and/or shredding of VFG waste has the advantage that in essence the entire flow of VFG waste can be treated and/or handled by the VFG waste treatment 5 facility. Sieving of VFG waste has an additional advantage that the surface area of the fraction which is to be fermented is sufficient large to enable a suitable and in essence complete fermentation of the fermentable matter thereof.

10 In yet another preferred embodiment, the compost from step c) is size fractioned, preferably by sieving, into size fractions of <15 mm, 15-40 mm and >40 mm. Generally, fractions of <15 mm are considered as the end-product of the treatment of VFG and suitable for being marketed as compost.

15 When such compost would be unsuitable for marketing, for example as there would be too much toxic compounds or too many impurities comprised by the compost, such compost needs to be disposed of in such a way as to prevent it from being exposed to the environment.

20 In yet another preferred embodiment, the non- fractioned compost is added to the at least partially fermented waste or digestate of step b). Even though from a financial point of view non-sieved compost may be the preferred choice of compost for circulation thereof, sieved 25 compost can also be used for circulation. Circulation of non-fractioned, but also sieved or fractioned compost, is advantageous as such compost can be composted more efficiently and effectively. Additionally or alternatively, the digestate can also be sieved prior to mixing with 30 compost and/or VFG waste.

It is preferred to use non-fractioned compost or compost of larger size (>15 mm) for mixing with digestate. Such larger sized compost improves the aeration of the 11 mixture to be composted. Also, larger sized matter may compost into smaller parts by (re)circulation thereof into the composting treatment.

In another suitable embodiment, composting the 5 mixture of step c) is by aeration with air of ambient temperature to 70°C, preferably ambient temperature to 65°C. Additionally or alternatively, such air may be of ambient temperature prior to aeration and become heated to 30 to 70°C, preferably 40 to 65°C by its use for aeration.

10 Additionally or alternatively, such air is of ambient temperature prior to aeration and becomes heated to from 30 to 70°C, preferably 40 to 65°C, before use thereof in aeration of the compost. This air used for aeration can be heated by use of a heat exchanger using heat from the air 15 before passage thereof through the bio-filter.

In yet another preferred embodiment, the fermenting the VFG waste of step a) is thermophylic fermentation. Mesophylic and psychrophylic fermentation may also be suitable for use according to the invention.

20 Thermophylic fermentation proceeds faster than mesophylic or psychrophylic fermentation.

In yet another preferred embodiment, C02, produced in the fermentation of step a), is collected. Subsequently, the C02 is preferably supplied to a greenhouse. Besides 25 collection of C02 for supply to a greenhouse, C02 may be supplied to any interested third party. An advantage of supplying C02 to a greenhouse is the generation of a short-cycle of C02. Short-cycle C02 means that C02 which was fixed by plants, is released by the biological fermentation after 30 which the released C02 is supplied to a greenhouse where it can be fixed by a plant again to sustain its growth and development.

Generally, in order to obtain purer or even high 12 grade C02, it will be necessary to separate or upgrade the C02 from the biogas mixture which is collected during the fermentation process according to the invention. Next, the produced C02 can be further process or marketed.

5 In a final preferred embodiment, energy, preferably in the form of water of 30°C to 60°C, produced in the composting of step c) is collected, preferably for supply to a greenhouse. However, the energy or heated water can be supplied to any third party. An advantage of 10 supplying warm water to a greenhouse is that the energy derived from the composting process can be used to heat a greenhouse. Such a supply of energy contributes to an environmentally friendly operational management of a greenhouse or any other business. Such supply of heat to a 15 greenhouse, or any other business or consumer, can be through a geothermal installation which allows supply of heat to the greenhouse upon demand.

Another aspect of the invention relates to a method for providing a greenhouse with carbon dioxide and/or 20 heat comprising the steps of: a) fermenting vegetable, fruit and garden waste to obtain biogas, b) adding compost and/or vegetable, fruit and garden waste to the at least partially fermented waste, 25 c) composting the thus obtained mixture to obtain heat and compost, d) separating C02 from the biogas from step a) and supplying the C02 to a greenhouse, e) supplying heat produced in step c) to a greenhouse, 30 preferably in the form of water of 30°C to 60°C.

A final aspect of the invention relates to a waste treatment facility for the treatment of vegetable, fruit and garden waste, comprising a fermentor (2) suitable for 13 fermenting vegetable, fruit and garden waste into a digestate; means for adding, and optionally mixing of, compost and/or vegetable, fruit and garden waste to the digestate; means (3) for composting the mixture of digestate 5 and compost and/or vegetable, fruit and garden waste.

Means for mixing digestate with compost and/or vegetable, fruit and garden waste can for example be a McLanahan mixer, but it will be clear for the skilled person that any suitable or comparable mixer will suffice.

10 In preferred embodiments, the waste treatment facility further comprises means (1) for shredding of vegetable, fruit and garden waste; and/or means (4) for sieving compost and/or vegetable, fruit and garden waste,-and/or means (6) for receiving and/or storing biogas; and/or 15 means (7) for receiving and/or storing C02, preferably upgraded C02, from the biogas; and/or means (8) for receiving and/or storing upgraded gas, preferably methane or upgraded methane, from the biogas; and/or means (5) for storing compost; and/or means (9) for treating humid, heated air 20 derived from the composting means (3); means (10) for treating air derived from the means (9); means (11) for obtaining heat or energy from the humid, heated air from means (9), means (12) for receiving/storing water from means (9) .

25 When operational, VFG waste is received by the waste treatment facility through means (20). VFG waste can be supplied to fermentor (2) by means (34) and/or pre-treated, such as shredded by means (1) and/or sieved into suitably smaller pieces by means (4) prior to fermentation.

30 Additionally or alternatively, the VFG waste is composted by composting means (3) without prior fermentation (means 35). Additionally or alternatively, the VFG waste is pre-treated, such as shredded and/or sieved into suitably smaller pieces 14 by means (1) and subsequently composted in composting means (3) without fermentation using means (50 or 52).

After fermentation by fermentor (2), biogas is collected (6) and optionally by via means (45) supplied to 5 separating and/or upgrading means (13). Separated or upgraded C02 can be supplied via means (30) to collector (7) and supplied to a greenhouse via means (32). Also upgraded biogas, comprising methane, can also be obtained from means (6) and supplied, preferably as upgraded methane, via (31) 10 to storage means (8) for storage and further supply via (33) to third parties, such as the transportation industry.

The fermentor (2) can be any fermentor, also termed digester or fermentation reactor, suitable for fermenting VFG waste. Such fermentor is preferably suitable 15 for thermophylic fermentation, or any other suitable fermentation process .

Composting means (3) can be any suitable means for composting of VFG waste. Composting means (3) is provided with means for aeration thereof to ensure suitable 20 composting can take place in means (3). Composting means (3) is a tunnel, chamber, room or space, preferably of elongated shape, with one or two openings at the ends for supply and removal of the content of the composting means. Preferably, composting means (3) is a tunnel which can be opened and 25 closed from either side. The heated, humid air derived from composting means (3) is supplied by means (36) to means (9) which is intended for treatment of exhaust gas. Means (9) ensures warm water, air and cold water can be obtained. Via means (39) warm water is lead to a heat-exchanger (11) for 30 exchange of heat or energy. Subsequently, heat or energy can be supplied to third parties by means (43), such as a greenhouse. Cooled water is supplied by means (40) back to means (9). Excess water can be supplied by means (41) to 15 means (12) for treatment and final disposal via means (42) to third parties, and for example used for irrigation purposes. Ambient air can be supplied by means (46) to means (9) to obtain preheated air which can be used via means (47) 5 in composting means (3). Exhaust gas can be supplied via (37) to treatment device (10), e.g. a biofilter, which treatment allows the discharge of air in the environment.

The present invention is further illustrated by the following figure and examples. These examples are not 10 intended to limit the scope of the invention in any way.

Figure 1 shows a facility for treating vegetable, fruit and garden waste.

Example 1 15 Several mixtures of digestate, VFG waste and compost were made and examined for their suitability for composting thereof.

Digestate was mixed with VFG waste and compost.

The amounts of the different components were determined, as 20 well as the amount dry matter as a percentage by weigh and the amount of organic matter comprised by the dry matter as a percentage by weight. Tables 1 and 2 show the specifications of the different mixtures as used in the experimentation phase.

25

Table 1

Mixture 1 Digestate VFG waste Compost Total

Amount (kg) 17.370 4.937 11.213 33.520

Mixture composition (% w/w) 52 15 34 100

Dry Matter content (% w/w) 26 38 65 40

Organic Matter of DM (% w/w) 34 52 35 37

Table 1: Analysis of Mixture 1

Table 2 16

Mixture 2 Digestate VFG waste Compost Total

Amount (kg) 17.370 8.055 18.295 43.720

Mixture composition (% w/w) 40 18 42 100

Dry Matter content (% w/w) 26 38 65 44

Organic Matter of DM (% w/w) 34 52 35 37

Table 2: Analysis of Mixture 2

After visual inspection of the mixtures as obtained it was decided to compost mixture 2 as this mixture 5 appeared to be more suitable for research purposes.

Composting of mixture 2 was for about 28 days in an open air windrow composting facility without additional turning and aerated by sucking air through the windrow by a perforated pipe under the windrow in which the pressure is 10 maintained. Before the start the windrow was covered with a small layer of overscreen material from composting. The starting temperature of the compost, as measured inside a heap of compost, was about 30°C. The temperature increased to about 60 to 70 degrees within 1-4 days, indicating the 15 composting proceeded in a suitable manner. The temperature was quite stable at around 70°C for a period of roughly 10 days .

The compost as obtained from mixture 2 was sieved and analysed for dry matter content.

20 Table 3

Fraction DM (g/kg) DM (% w/w) <15 629 63 15-40 568 57 >40 604 60

Table 3: Analysis of sieved fractions obtained from composting mixture 2.

17

Results demonstrate that it is possible to treat VFG waste by a method using fermentation and composting according to the present invention. Moreover, the non-fractioned compost as obtained appeared to be very suitable 5 for sieving and yielded compost of good quality.

Example 2

Two mixtures were obtained using a shovel to mix the mixture. After mixing with the shovel the mixtures were 10 mixed with a compost mixer. Table 4 shows the results on bulk density:

Table 4 mixture After mixing with After mixing with shovel compost mixer "Ï ± 700 kg/m3 850-900 kg/m3 ~2 600-700 kg/m3 ± 850 kg/m3

Table 4: Bulk density of mixtures 1 and 2.

Results demonstrate that in both cases mixing with a compost 15 mixer increased the bulk density dramatically. Until now there is no clear explanation for that.

1037223

Claims

Method for treating vegetable, garden and fruit waste, comprising the steps of: a) fermenting vegetable, garden and fruit waste, b) adding compost and / or vegetable, garden and fruit waste to the at least partially fermented waste, c) composting the mixture thus obtained to obtain compost, wherein the percentage of dry matter of the mixture, prior to composting, is 35 - 55 weight percent, preferably 40 - 50 weight percent, more preferably 42 - 48 weight percent, most preferably 44-46 weight percent.

2. Method according to claim 1, wherein the at least partially fermented waste according to step b) is digestate obtained from the fermentation of vegetable, garden and fruit waste.

3. Method according to claim 2, wherein the weight of the digestate divided by the weight of the compost and / or vegetable, garden and fruit waste from the mixture, prior to composting, between 0.3 - 2.0, preferably 0.4 - 1.5, more preferably 0.5 - 1.5, most preferably 0.5 - 1.0 or about 0.7.

4. Method according to any of claims 1-3, wherein the compost from step c) is added in step b).

The method of any one of claims 1-4, wherein the at least partially fermented waste or digestate according to step b) is at least partially fermented waste or digestate from step a).

The method according to any of claims 1-5, wherein the at least partially fermented waste or digestate comprises 20 - 38, preferably 24 - 34, more preferably 26 - 32 weight percent dry matter.

The method of any one of claims 1-6, wherein the compost comprises 40 - 90, preferably 50 - 80, more preferably 60 - 70 weight percent dry matter.

A method according to any one of claims 1-7, wherein the vegetable, fruit and garden waste comprises 25 - 60, preferably 30 - 50, weight percent dry matter.

9. Method according to any of claims 1-8, wherein the vegetable, fruit and garden waste from step b) is substantially fresh or non-fermented vegetable, fruit and garden waste.

A method according to any one of claims 1-9, wherein the vegetable, fruit and garden waste from step a), prior to fermentation thereof, is sieved and / or ground.

A method according to any of claims 1-10, wherein the compost of step c) is fractionated by size, preferably by sieving it, into size fractions of <15 mm, 15-40 mm and> 40 mm.

The method of any one of claims 1 to 11, wherein unfractionated compost is added to the at least partially fermented waste or digestate from step b).

13. Method according to any of claims 1-12, wherein the mixture of step c) is mixed prior to composting thereof.

A method according to any one of claims 1-13, wherein composting the mixture of step c) takes place with aeration with air from ambient temperature to 70 ° C, preferably ambient temperature to 65 ° C.

The method of any one of claims 1-14, wherein the fermenting of the vegetable, fruit and garden waste from step a) is thermophilic fermentation.

A method according to any of claims 1-15, wherein CO2 produced in the fermentation of step a) is supplied to a greenhouse.

A method according to any one of claims 1-16, wherein energy, preferably in the form of hot water of 30-60 ° C, produced during the composting of step c) is supplied to a greenhouse.

18. Method for providing carbon dioxide and / or heat to a greenhouse comprising the following steps: a) fermenting vegetable, fruit and garden waste to obtain biogas, b) adding compost and / or vegetable, fruit and garden waste to the at least partially fermented waste, c) composting the resulting mixture to obtain heat and compost, d) separating CO2 from the biogas from step a), and optionally providing the CO2 to a greenhouse, e) providing heat produced in step c), preferably to a greenhouse, preferably in the form of water from 30 ° C to 60 ° C.

19. Waste treatment installation for the treatment of vegetable, fruit and garden waste, comprising a digester (2) suitable for fermenting vegetable, fruit and garden waste into a digestate; means for adding, and optionally mixing, compost and / or vegetable, fruit, and garden waste to the digestate; a device (3) for composting the mixture of digestate and compost and / or vegetable, fruit and garden waste.

The waste processing plant according to claim 19, further comprising device (1) for grinding vegetable, fruit and garden waste; and / or device (4) for sieving compost and / or vegetable, fruit and garden waste; and / or means (6) for receiving and / or storing biogas; and / or means (13) for biogas reprocessing; and / or means (7) for receiving and / or storing CO2 from the biogas; and / or means (8) for receiving and / or storing 5 processed biogas; and / or means (5) for storing compost; and / or means (9) for treating moist, heated air from the composting device (3); device (10) for treating air from device (9); device (11) for obtaining heat or energy from the moist, heated air originating from device (9); device (12) for receiving / storing water from device (9).