Method for producing biomass

Abstract

The invention relates to a method for producing biomass, comprising: planting rows of black poplar (or European mountain poplar tree seedlings or cuttings in ridges at a density greater than 40000 units / hectare; the method is characterized in that the plantation is cut at the level of the ridges every year for 15 to 20 years, poplar stalks having a length of less than 7 meters and a diameter of less than 6 centimeters are obtained during the cutting every year, and the poplar stalks are transversely cut into substantially cylindrical biomass blocks having an adjustable length and a variable diameter consistent with the diameter of the poplar stalks in the cut area.

Description

Technical Field

[0001] The invention is applicable in the field dedicated to the production of biomass, which can be used as fuel in factories for the production of electricity, heat or any other type of energy. Background Art

[0002] Currently, there are a variety of installations that use biomass as a fuel to generate heat or electricity.

[0003] This biomass comes primarily from trees that have been felled in a controlled manner, or from the waste that remains after the wood from said trees has been used for other purposes.

[0004] Typically, this biomass is in the form of pellets or bricks made from a mixture of ground wood and glue or a binder, which, when properly pressed, form small cylinders.

[0005] One of the fundamental drawbacks of preparing this biomass is the high cost of wood grinding, adhesives and pressing processes to obtain the final product in pellet form.

[0006] Another disadvantage is the low yield of tree plantations used to obtain biomass.

[0007] For example, patent ES2 383 337 B1, which claims priority to patent US 8 839 554 B2, describes a method for producing biomass fuel using upright Tamarix (Tamarix Erect) trees. The upright Tamarix trees are planted and / or cultivated on a piece of land. After the biomass of the upright Tamarix trees grows, at least a portion of the biomass is harvested for biomass fuel. The planting density can be greater than 6,000 upright Tamarix trees per hectare.

[0008] Due to the growth rate and morphology of the upright Tamarix tree, its space requirements limit the density of trees per hectare and the production period is relatively short.

[0009] The technical problem under consideration therefore concerns the development of a process for the production of biomass which allows obtaining high yields in plantations and minimizing the costs of obtaining biomass suitable for consumption. Summary of the invention

[0010] The proposed objectives can be achieved by developing a method for producing biomass, the purpose of the present invention being to cultivate Populus nigra or Populus tremula trees under specific conditions, which, due to their slender morphology and rapid growth rate, obtain a high biomass yield per hectare and obtain biomass pieces or parts of a size suitable for use directly by cutting, thereby eliminating the need to grind the biomass, mix it with a binder, and form biomass pieces of a size suitable for consumption by pressing; thereby significantly limiting the reduction of the costs of obtaining biomass.

[0011] The method for producing biomass, object of the present invention, comprises the following steps:

[0012] - Create parallel rows in the field:

[0013] - Planting rows of seedlings or cuttings of a given poplar species in said ridges at a density greater than 40,000 units / hectare.

[0014] - The plantations are cut annually at ridge level for 15 to 20 years, obtaining in each year's cutting poplar stems less than 7 meters in length and less than 6 centimeters in diameter, using only stems meeting said dimensions as biomass.

[0015] - Cut the stems transversely into biomass pieces or blocks, the length of which can be adjusted according to the boiler type and the diameter of which corresponds to the diameter of the poplar stems in the cutting area.

[0016] The poplar species (Populus nigra or Populus tremula) used in the present method for producing biomass is selected based on a number of parameters, as follows:

[0017] - This species is a deciduous tree with strong growth ability. In the first year of growth of seedlings or cuttings, during the annual vegetative period, a stem of 5 to 6 meters with a base diameter of 4 to 6 cm is formed. In subsequent years, multiple cuttings, usually 1 to 5, sprout from the trunk cut in the first year. Among them, during the annual vegetative period, the size of the regenerated stem is similar to that of the first year because the roots of the initial seedlings and cuttings are also increased in the first year.

[0018] - In addition, this species is a tree with an elongated morphology that does not develop a wide crown, allowing the planting of cuttings or seedlings at smaller spacings and, therefore, plantations with a high density of trees per hectare, greater than the above-mentioned 40,000 units per hectare, even reaching the above-mentioned 65,000 trees.

[0019] The maximum diameter of the poplar stems harvested each year reaches 4 cm to 6 cm, and the poplar stems are cut transversely, for example by a disc cutter, and biomass blocks or pieces of a size suitable for consumption are obtained directly from the stems without grinding the biomass, mixing it with a binder, and pressing it to obtain the biomass portion in the form of pellets.

[0020] According to the present invention, the ridges formed on the ground are arranged in pairs with a height of 10 cm to 15 cm, since the length of the cuttings to be planted in the first year is 20 cm to 30 cm, the interval between each pair of ridges is 70 cm to 80 cm, and the interval between ridge pairs is 100 cm to 150 cm.

[0021] Planting cuttings or saplings on ridges allows the poplar stems to be cut annually by machine just above the ridge so that the machine's blades do not hit any stones or irregularities in the ground and break or become damaged, thus increasing production costs.

[0022] The spacing between each pair of ridges is 70 cm to 80 cm, allowing the trees to fully widen laterally, thereby significantly shortening the planting distance between consecutive poplar (black poplar or European poplar) cuttings or seedlings on the same ridge.

[0023] The spacing between pairs of ridges is calculated to be between 100 cm and 150 cm, allowing the passage of machines that carry out the annual cutting and harvesting of poplar stems.

[0024] In a specific embodiment, in a preferred manner, in order to optimize the production capacity per hectare of the poplar plantation, the spacing between each pair of ridges is 75 cm, and the spacing between ridge pairs is 125 cm to allow cutting and harvesting machines to have sufficient clearance to pass.

[0025] According to the invention, taking into account the above-mentioned spacing distances between each pair of ridges and between ridge pairs, the distance between consecutive seedlings or cuttings on the same ridge is 15 cm to 25 cm, thereby achieving the mentioned density of 65,000 trees per hectare in the plantation.

[0026] The growth of poplar (Populus nigra or Populus tremula) seedlings or cuttings in initial plantings may be affected by uncontrolled growth of weeds, therefore this approach involves covering the area between the seedlings with weed-proof sheets or netting during the first year.

[0027] Poplars of the species mentioned grow in very wet or flooded lands, therefore plantations consisting of these poplar species are usually irrigated using flood irrigation, which consumes about 18,000 to 20,000 cubic meters of water per hectare per year, greatly limiting the area in which plantations can be distributed due to lack of water resources.

[0028] According to the present invention, in order to avoid this disadvantage, the plantations are irrigated by drip irrigation with an annual water consumption of 2300 to 2800 m3 / hectare / year, which means that the required amount of irrigation water is greatly reduced, thereby significantly widening the area where plantations for obtaining biomass can be distributed.

[0029] The invention also contemplates the use of wastewater for irrigation after a first dilution of said wastewater (removal of heavy and floating solids), so that fertilizers will not be needed.

[0030] Additionally, to reduce the amount of water needed to irrigate the plantations and facilitate nutrient uptake by the tree roots, mycorrhizae were incorporated into the irrigation water at 0.8 to 1.2 l / ha during the first year of cultivation.

Claims

1. A method for producing biomass, wherein include: - planting rows of Populus nigra or Populus tremula seedlings or cuttings in ridges at a density of more than 40,000 units per hectare, - annual felling of the plantations at the level of ridges for 15 to 20 years, obtaining in annual felling poplar stems less than 7 meters in length and less than 6 centimeters in diameter, - Transversely cutting the poplar stems into substantially cylindrical biomass pieces having an adjustable length and a variable diameter, corresponding to the diameter of the poplar stems in the cutting area.

2. The method according to claim 1, in, The pieces or chunks of poplar biomass are dried at room temperature before being used as fuel.

3. The method according to claim 1, in, The ridges are 10 to 15 centimeters high and are arranged in pairs, with the interval between each pair of ridges being 70 to 80 centimeters.

4. The method according to claim 3, in, The spacing between ridge pairs is 100 cm to 150 cm.

5. The method according to claim 1, in, The spacing between poplar saplings or cuttings in the same row along the corresponding ridges is 15 cm to 25 cm.

6. The method of claim 1, comprising covering the area between the seedlings with weed-proof sheets or nets during the first year of cultivation.

7. The method according to claim 1, in, The plantations are irrigated by drip irrigation with a water consumption of 2300 to 2800 m3 / ha / year.

8. The method according to claim 7, in, During the first year of cultivation, mycorrhizae were incorporated into irrigation water at a rate of 0.8 l / ha to 1.2 l / ha.