CA2092963A1

CA2092963A1 - Ground cover sheet formed of variable biodegradable cellulosic fiber composition and method of making same

Info

Publication number: CA2092963A1
Application number: CA002092963A
Authority: CA
Inventors: Camille Desmarais
Original assignee: Individual
Current assignee: Individual
Priority date: 1993-04-07
Filing date: 1993-04-07
Publication date: 1994-10-08

Abstract

GROUND COVER SHEET FORMED OF VARIABLE
BIODEGRADABLE CELLULOSIC FIBER
COMPOSITION AND METHOD OF MAKING SAME
Abstract of the Disclosure A biodegradable ground cover sheet formed from a mulch which comprised of cellulosic fibers in the amount of 25-95% and in admixture with 10-40%
residual sludge from a paper making process and 10-40% peat moss. Additives are also added to the mixture in the amounts of 5-25% and these are formed from a mixture of ingredients including styrene butadiene base latex and cellophane or colophane. A
mineral compound in the amount of 10-50% is also added to the mixture and is selected from clay, calcium carbonate or talc. A predetermined quantity of selected biodegradable additives are also added.
The mixture has a preselected quantity of the above-mentioned compounds depending on its intended use and desired biodegradable time. The sheet outer surfaces may also be coated with a wax to adjust the biodegradable time.

Description

2~92963 Background of Invention Field of the Invention The present invention relates to a biodegradable ground cover sheet formed from a mulch of cellulosic fibers and compounds which are preselected whereby to adjust the biodegradable time of the sheet and is comprised of cellulosic fibers in predetermined quantities, residual sludge from paper, peat moss and minerals as well as biodegradable additives including adhesives.
The variable biodegradable mulch of this invention is formed from cellulosic fibers and is for use in agriculture and in forestry conservation in order to eliminate undesirable weeds and plants, to reduce the evapotranspiration of the soil, to increase the percentage of organic matter in the soil and to create a micro environment which is conducive to the growth of plants. The composition and method of fabrication of the mulch permits fertilizers, fungicides, herbicides and insecticides to be added either in the mulch or on the surface of the mulch.
Presently, there is a need for a mulch in a paper or cardboard form having an adjustable biodegradable time which is a function of specific needs of agricultural or forestry products.
Description of Prior Art In the prior art, various ground cover sheets or discs have been provided and these are fabricated from various materials to which has been added seeds, fertilizers or fungicides. Such products date back to at least 1894, as disclosed in U.S.
Patent No. 526,512. In 1935, a Kraft paper was utilized and including a superficial nitrogen coating which, however, was not impregnated into the paper. This material could be used as a mulch or ~ "~. ~",,~ "~ ., ",, ~ , " , ,, ., ", ~ ,., , , "~ ~, "

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2~929~3 placed inside plant containers, as is disclosed in U.S. Patent 2,038,019. Later on, mulches made of straw were introduced in the marketplace and to which fertilizers, fungicides or bacteria were added.
U.S. Patent No. 3,998,006 discloses the use of a sheet of cellulosic fibers of approximately ~"
in thickness and to which is added fertilizers. The sheet is also provided with a perforated plastic coating. More recently, in Sweden there was developed a mulch formed from peat moss and to which fertilizers and seeds were added, as disclosed in U.S. Patent 4,283,880.
It is pointed out that none of the mulches known in the prior art can be adapted to plant cultures of different types, nor are they suitable for use in climates which experience a broad range of temperatures and sunshine. Various plants require protection for a short duration, as is the case with tomato plants, while other plants need longer protection, such as the blueberry plant or the apple tree. Presently, polyethylene film is widely used in agriculture and, more particularly, in the production of vegetables and small fruits.
The durability of the plastic sheets vary in accordance with its thickness, and it is not biodegradable, which is one of its greatest disadvantages in agricultural use. It is possible to add to the plastic substances which are biodegradable, but the plastic particles will not biodegrade over a long period of time. Accordingly, when such material is used in agriculture, the user must remove the plastic sheets and dispose of them due to its non-biodegradable nature. These operations are expensive and regulatory agencies are very much concerned with the manner in which these plastics are disposed. Currently, there is a need to reduce such pollutants from the soils or even to burn them. A still further disadvantage of using polyethylene sheets is that it is impossible to add to the sheet fertilizers, fungicides or biological insecticides such B.T. The only practical use of the plastic sheet is to control weeds and reduce evaporation.
SUMMARY OF INVENTION
It is a feature of the present invention to provide a biodegradable mulch for the fabrication of biodegradable ground cover sheets and which substantially overcomes the above-mentioned disadvantages of the prior art.
Another feature of the present invention is to provide a biodegradable ground cover sheet which is biodegradable in its entirety.
Another feature of the present invention is to provide a biodegradable ground cover sheet formed of a mulch of which the composition can be ad~usted so that the cover sheet will biodegrade over a desired time period.
Another feature of the present invention is to provide a biodegradable mulch to which we can incorporate fertilizers and fungicides as well as insecticides which may also be biological, such that these are impregnated in a ground cover sheet.
Another feature of the present invention is to provide a biodegradable ground cover sheet having a desired tone or color dependent on the intended use of the ground cover sheet as dictated by climatic conditions and the type of plants it is intended to be used with.
According to the above features, from a broad aspect, the present invention provides a biodegradable ground cover sheet formed from a mulch ` :~ . .. : ' . : .

: ' . .:,: ' , ~ ` ` ...................... . ...... -... . ~ .. ,.. '. ~ . -- 2~929~3 which is comprised of a cellulosic fiber mixture having been treated to destroy microorganisms therein, said mixture having 25-95% wood fibers, 10-40~ residual sludge from a paper making process and 10-40% peat moss, and additives in the amounts of 5-25%. The additives are from a mixture of ingredients including styrene butadiene base latex and cellophane or colophane. A mineral compound in the amount of 10-50~ is also added to the mixture and is selected from clay, calcium carbonate or talc. A predetermined quantity of selected biodegradable additives are also added. The mixture has a preselected quantity of the above-mentioned compounds depending on its intended use.
DESCRIPTION OF PREFERRED EMBODIM~NTS
A preferred embodiment of the present invention will now be described with reference to the accompanying drawings in which:
FIGURE 1 is a simplified block diagram illustrating the method of manufacture of the biodegradable ground cover sheet of the present invention;
FIGURiES 2A and 2B are perspective views showing the biodegradable ground cover sheet in the form of a circular or square disc positioned about the trunk of a plant or a tree;
FIGURE 3A is a plan view showing a biodegradable ground cover sheet which has been perforated such as by a planting machine or other means;
FIGURE 3B is a cross-section view showing the ground cover sheet when installed with a plant protected thereby; and FIGURES 4A and 4B are cross-section views through a biodegradable ground cover sheet of the types having a short and long biodegradable life.

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:~ æ~9~3 DESCRIPTION OF PREFERRED EMBODIMENTS
Referring now to the drawings, and more particularly to Figure 1, there will be described the construction of the biodegradable ground cover sheet of the present invention. It is pointed out that all of the products utilized in the fabrication of the mulch which is used to form the ground cover sheet are all biodegradable. An important characteristic of the mulch of the present invention is that its biodegradability is variable and adjusted depending on the biodegradable time required of the ground cover sheet. This time is predetermined in accordance with the intended use of the cover sheet. The mixture of the various biodegradable products utilized in the mulch may be adjusted in quantities to provide the required biodegradable time and the outer surfaces of the sheet may also be coated. The biodegradable time of the cover sheet of the present invention can vary between one month to seven years depending on the mixture of the compounds. Figure 4A illustrates a biodegradable sheet of the type that can biodegrade from 1 to 24 months. As shown in Figure 4B, by coating the exterior surface 30 of the sheet 35 with a wax coating 31, the biodegradable time can be adjusted from about 12 to 84 months. This feature of the present invention is obtained by fabricating a mulch having the compounds described below.
The basic ingredients of the mulch are comprised of cellulosic fibers, additives and minerals. The cellulosic fibers 32 consist of a mixture of about 25-95~ wood fibers, 10-40% of residual sludge from a paper-making process, and 10-40% of peat moss, all of which are treated with ultra-violet radiation. The additives 33 are provided in quantities of 5-25% and may consist of a ~ . . . . - . , ........ . ~ , .. .

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styrene butadiene latex base and cellophane or colophane or a mixture of two or more of these ingredients. Other suitable protective biodegradable agents may also be substituted.
Minerals are added in quantities of between 10-50%
and they comprise any one of or a mixture of clay, calcium carbonate or talc or other suitable minerals. Wax additives also provide for the surface coating 31.
The cellulosic fibers utilized may comprise chemical pulp, thermo-mechanical pulp or pulp from de-inking or recycling plants. The chemical pulps may be bisulphite, Kraft, sulphate or sodium carbonate. The thermo-mechanical pulps may be thermo-mechanical, chemico-thermo-mechanical, or semi-chemico-thermo-mechanical.
As shown in Figure 1, these cellulosic fibers, peat moss, sludge and mineral powders may be contained in reservoirs 10 and are automatically dispensed by an automatic control system 11 which may be computer-controlled whereby the end product characteristics may be selected from a control unit 11 which automatically controls valves 12 to dispense appropriate mixtures of wood fibers, mineral powders, moss and sludge as well as protective additives 33. The control unit 11 controls the dispensing valves 12 of the reservoirs and these are dispensed in a mulch mixing reservoir 13. The coatings are added at the outlet of the reservoir 13.
To this compound mixture is added a predetermined quantity of selected biodegradable additives and these may be added to the surface of the mulch in a sheet former 14 or else directly within the mixing reservoir 13, as shown. The additives may also be retained in containers 15 ~29~3 having automatic dispensing valves 16 which are also controlled by the control unit 11. The additives are added at an appropriate time whereby the cellulose fibers are protected against attack by micro-organisms. This protection varies as a function of the type of additives utilized and their quantities. This characteristic of the mulch permits the adjustability of its biodegradable time depending on the intended use of the ground cover sheet and the need of protection. No one has heretofore utilized biologic fertilizers of nitrogen formed from a flour of fish (10-6-0), blood (12-1-3) or feathers (12-0-0); or phosphates formed of bone flour (3-20-0), rock phosphates (0-27-0) or super-phosphate (0-20-O)i or potassium formed from sul-po-mag (0-0-22) or wood ashes (0-0-10). It is also possible to add oligo elements when the intended use is for very specific plants or for regions where the soil is lacking in oligo elements. Insecticides and fungicides may also be added where the intended use is for areas where there is an infestation or a persistence of unwanted insects or pests.
Another advantage of the mulch of the present invention is that the color of the mulch forming the ground cover sheet can be adjusted. Natural colorants may be added to the mulch in the mixing reservoir 13 or on the sheet former 14 in order to vary the albedo of the material as a function of the calorific (heat) needs of various plants. If the mulch is made to be very dark, preferably black, it will absorb the sun's rays and prevent the rays from being reflected. If the mulch is clear or white, the reverse phenomenon occurs, wherein the sun's rays will be mostly all reflected with very weak absorption taking place. The variation of color permits the use of the biodegradable ground cover i : . . , - . ,: .- - . " : ..... . , ............ ~ . , :. ! - ' '~ . : , .

29~3 sheet of the present invention in various climatic regions as demonstrated by Table I hereinbelow.

.
CLIM~TE WINTER SPRING SUMMER AUTUMN
Equatorial Black Black White White Tropical Black Black White White Subtropical Black Black Black __ ¦
Temperate __ Black Black __ Furthermore, the color of the ground cover ~ -sheet will provide benefits to various fruit or vegetable plants growing in the same climate but having different calorific requirements. In other words, it is preferable with certain plants to have a white cover sheet, whereas with others, it is preferable to have a black one. If black cover sheets are utilized, for example, in the growth of celery, this will not benefit the plant as would a white cover sheet due to the ideal soil characteristics for celeries. The following table illustrates a group of vegetable plants and their required cover sheet color to achieve maximum benefits.

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2~63 . .
E'RUITS AND VEGETABLES COYER SHEET ¦
Artichokes White Celery White Cabbage White Strawberries White l I
Melons Black Peppers Black Lettuce _ White Tomatoes Black Etc.
Table 2 As previously described, the fibers are treated with ultraviolet radiation prior to being added to the mixing reservoir and this is in order to destroy the microorganisms present in these fibers.
As shown in Figure 1, the ground cover sheet material at the outlet of the sheet forming machine 14 may be in rolled form 20 or fed to a sheet cutter 28 to form stacks of sheets 19.
Discs 18, as shown in Figures 2A and 2B, may be cut from the sheets 19 to a convenient shape and provided with a central cavity 17 and slit at 17' to provide access to the cavity 17 to permit positioning of the disc 18 about the trunk 21 of a plant or tree. These discs 18 may be of various sizes and configurations for use around plants and as a ground cover, and small ones may be used in pots containing decorative plants. The sheet may also be sold in roll form 20 and the user may cut the sheet 22 to any desired shape. As shown in Figures 3A and 3B, holes 23 may be formed in a long sheet for ease of proper positioning of small plants or seeds in the soil. The holes 23 are made at ~; : : : : . .
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~ 9 ~ 3 precise intervals. Accordingly, the sheet can also act as an aid in planting vegetable plants.
Alternatively, the holes 23 can be formed by a mechanical or automatic planter. As shown in Figure 3B, the sheet 23 may be embedded at the opposed side edges 24 in the soil 25 to provide retention of the sheet. Plants such as shown at 26 will then grow above the sheet 22 with their roots 27, as well as the plant, protected from weed growth.
It is within the ambit of the present invention to cover any obvious modifications of the preferred embodiment described herein, provided such modifications fall within the scope of the appended claims.

Claims

1. A biodegradable ground cover sheet formed from a mulch comprised of a cellulosic fiber mixture having been treated to destroy microorganisms therein, said mixture having 25 to 95% wood fibers, to 40% residual sludge from a paper-making process and 10 to 40% peat moss; 5 to 25% adhesives formed from a mixture of ingredients including styrene butadiene base latex, and cellophane or colophane; and 10 to 50% mineral compound selected from clay, calcium carbonate or talc; a predetermined quantity of selected biodegradable additives; said mixture having preselected quantities of compounds to adjust the biodegradable time of said sheet.

2. A biodegradable ground cover sheet as claimed in claim 1 wherein there is further provided a wax coating on one or both exterior surfaces of said ground cover sheet.

3. A biodegradable ground cover sheet as claimed in claim 1 wherein said additives include biological fertilizers selected from nitrogen, phosphate and potassium.

4. A biodegradable ground cover sheet as claimed in claim 3 wherein said mulch further includes natural coloring substances to obtain a cover sheet of a desired tone dependent on the desired quantity of sun ray absorption or reflection characteristic required.

5. A biodegradable ground cover sheet as claimed in claim 4 wherein said cellulosic fibers are selected from chemical pulp, thermo-mechanical pulp or de-inked or recycled pulp or a mixture of some or all of these.

6. A biodegradable ground cover sheet as claimed in claim 5 wherein said chemical pulp is selected from the group of bi-sulphate, Kraft, sulphate or sodium carbonate pulps.

7. A biodegradable ground cover sheet as claimed in claim 5 wherein said thermo-mechanical pulp is selected from the group of chemico-thermo-mechanical, semi-chemico-thermo-mechanical or thermo-mechanical pulps.

8. A biodegradable ground cover sheet as claimed in claim 3 wherein said nitrogen additive is selected from a flour of fish, blood or feathers or a mixture of two or more of these.

9. A biodegradable ground cover sheet as claimed in claim 3 wherein said phosphate additive is selected from bone flour, rock phosphate or super-phosphate or a mixture of two or more of these.

10. A biodegradable ground cover sheet as claimed in claim 3 wherein said potassium is selected from wood ashes or sul-po-mag or a mixture of these.

11. A method of manufacture of a biodegradable ground cover sheet comprising the steps of:
i) forming a mulch in a mixing reservoir by mixing (a) a cellulosic mixture having been treated to destroy microorganisms therein, said mixture having 25% to 95% wood fibers, 10% to 40% residual sludge from a paper-making process, 10% to 40% peat moss; (b) 5% to 25% adhesives formed from a mixture of in-gredients including styrene butadiene base latex and cellophane or colophane;
and (c) a mineral compound in the amount of 10% to 15% and selected from clay, calcium carbonate or talc;
ii) depositing said mulch on a sheet forming machine, and iii) depositing a predetermined quantity of additives on said mulch on said sheet forming machine.

12. A biodegradable ground cover sheet as claimed in claim 1 wherein there is further provided the step of coating one or both exterior surfaces of said cover sheet in said sheet forming machine.

13. A method as claimed in claim 11 wherein said additives of step (iii) are incorporated with said mulch in said mixing reservoir.

14. A method as claimed in claim 11 wherein there is further provided the step of treating said cellulosic mixutre with ultra-violet radiation to destroy micro-organisms contained therein.

15. A method as claimed in claim 11 wherein there is further provided the step of determining the biodegradable rate of said mulch and selecting said additives in proper quantities to provide said cellulosic fibers a predetermined resistance against deterioration by micro-organisms.

16. A method as claimed in claim 11 wherein there is further provided the step of determining the desired sun ray absorption or reflective characteristics of said mulch and adding natural colorants to said mulch to obtain a required tonality.