Biochar composition

Abstract

A biochar composition formed from the pyrolysis of a mixture comprising: feedstock (e.g., 50 wt.%); and egg shell particulate (e.g. 50 wt.%) free from egg-membrane. The egg shell particulate may be he

Description

The present invention relates to a biochar composition, a method for producing the biochar feedstock composition, and the use of the biochar feedstock composition for reducing phosphate content. BACKGROUND OF INVENTION Phosphorus is a nutrient that is essential to the development of all life on earth. Phosphorus is one of the key ingredients in agricultural fertilisers for growing food. Phosphate is however a finite resource. In 2022 / 2023, 46 million metric tonnes of phosphate fertiliser were used globally to grow crops. This figure is expected to increase to 52 million metric tonnes by 2025 (IFIA,2021). Excessive levels of phosphate in water are causing eutrophication (i.e. excessive plant / algal growth) which affects the quality of the water and the ecosystem within it. Algal blooms remove oxygen from the water, destroying river life and causing large economic impacts on drinking water. 55% of river water bodies fail to achieve good ecological status in England in relation to Phosphate levels. It has been found that 60%-70% of phosphate in rivers comes from Sewage Treatment Works. There is a need for a method of removing phosphate from water, such as river bodies, which is nontoxic and doesn't produce toxic byproducts. SUMMARY OF INVENTION According to a first aspect of the present invention, there is provided a biochar composition formed from pyrolysis of a mixture comprising a feedstock; and egg shell particulate free from egg membrane. The term "egg shell particulate" is used herein to refer to the cracked outer egg shell portion without the yolk and albumin. The egg membrane is removed from the cracked outer egg shell portion. The cracked outer egg shell portion is preferably dried and the egg membrane removed therefrom. By removing the egg membrane, it has been found that the calcium carbonate content of the egg shell particulate is increased, thereby increasing the adsorption properties of the biochar composition. The egg shell particulate is preferably hen egg shell particulate. It is however to be understood that other egg shell particulate may be present, such as for example duck egg shell particulate. The egg shell particulate preferably comprises at least 90% by weight of calcium carbonate. The egg shell particulate is preferably dried to remove any excess or residual liquid and to reduce the moisture content of the egg shell particulate. The egg shell particulate may be dried by any suitable means, for example by using a rotary drum dryer. The egg shell particulate is preferably dried egg shell particulate. The egg shell particulate preferably comprises powdered, ground, crushed or milled egg shell. The egg shell particulate preferably has a maximum particle size of 2 mm. The mixture preferably comprises at least 40% by weight, preferably at least 50% by weight of feedstock. The mixture preferably comprises no more than 90% by weight, preferably no more than 80% by weight, preferably no more than 70% by weight of feedstock. The mixture preferably comprises between 40% and 90% by weight, preferably between 40% and 80% by weight, preferably between 40% and 70% by weight, for example about 50% by weight of feedstock. The mixture preferably comprises at least 10% by weight, preferably at least 20% by weight, for example 30% by weight of egg shell particulate. The mixture preferably comprises no more than 60% by weight, preferably no more than 50% by weight of egg shell particulate. The mixture preferably comprises between 10% and 60% by weight, preferably between 20% and 60% by weight, preferably between 30% and 60% by weight, for example about 50% by weight of egg shell particulate. In one embodiment, the mixture comprises about 50% by weight of feedstock and about 50% by weight of egg shell particulate. The feedstock is organic material that has been carbonised (e.g. pyrolyzed) under high temperature conditions, for example between 300 °C and 1000 °C, in the presence of little or no oxygen. This process, known as pyrolysis, releases bio-oils, gases and leaves a solid residue of carbon which is termed as biochar. Preferably, the pyrolyzing step heats the feedstock and egg shell particulate (free from egg membrane) to a temperature of at least 300 °C, preferably to a temperature of between 300 °C and 1000 °C, for example about 800 °C. The pyrolyzing step is preferably carried out for at least 6 hours. The pyrolyzing step may be carried out as a continuous process or as a batch process. The feedstock preferably comprises one or more of agricultural waste products (such as for example manure), forestry waste product (such as for example soft plant tissue or woody materials), municipal waste products, green and food waste products, or any combination thereof. According to a second aspect of the present invention, there is provided a method for producing a biochar composition comprising: obtaining a mixture comprising feedstock and egg shell particulate free from egg membrane; and pyrolyzing the mixture to provide a biochar composition. The egg shell particulate is preferably ground or milled or crushed or powdered prior to being mixed with the biochar feedstock. The method may further comprise exposing the biochar composition to ozone treatment to provide a functionalised biochar composition. The biochar composition may be exposed to ozone for a predetermined time period (for example at least 30 minutes, preferably at least 60 minutes, for example about 90 minutes). After ozone treatment, the functionalised biochar composition is preferably dried. According to a further aspect, the present invention provides a functionalised biochar composition comprising a biochar composition as herein described, in which the biochar feedstock composition has been exposed to ozone. The functionalised biochar composition is a surface oxygenated product which has been found to have improved cation exchange properties, and therefore capable of improved phosphate adsorption compared to the biochar composition. In one embodiment, exposure of the biochar composition to ozone results in a functionalised biochar feedstock composition with a cation exchange capacity (CEC) which is at least double the cation exchange capacity of the biochar composition. The cation exchange capacity can be measured using a protocol disclosed in Rippy .IF, Nelson PV (2007) Cation exchange capacity and base saturation variation among Alberta, Canada, moss peats. HortScience 42(2):349-352. The functionalised biochar composition has been found to have a reduced pH (for example approximately pH 5 to 6) compared to the pH of the biochar composition (having a pH of approximately 7). This decrease is pH results from the addition of acidic oxygen functional groups on the surface of the functionalised biochar. The reduction in pH is related to the duration and exposure of the biochar composition to ozone. According to a further aspect of the present invention, there is provided the use of a biochar feedstock composition as herein described to reduce the phosphate content of a liquid. The biochar composition preferably removes, for example adsorbs, phosphate from a liquid. The liquid may be free flowing. The liquid may be non-flowing. In one embodiment, the liquid is water. The water may for example be waste water (for example from a sewage treatment plant). The water may be river water, a lake or a well. According to a further aspect of the present invention, there is provided a method for reducing phosphate content of a liquid, the method comprising: obtaining a biochar composition and / or functionalised biochar composition as herein described; and exposing a liquid to the biochar composition and / or functionalised biochar composition. The method may be a continuous method or a batch-wise method. The liquid may be flowed through the biochar composition and / or functionalised biochar composition. The biochar composition and / or functionalised biochar composition may be provided in the form of a filter configured in use to allow the liquid to flow through. According to a further aspect of the present invention, there is provided a filter for reducing phosphate content of a liquid, in which the filter comprises a biochar composition and / or functionalised biochar composition as herein described. According to a further aspect of the present invention, there is provided the use of a biochar composition and / or functionalised biochar composition as herein described to reduce phosphate content within animal waste. The biochar composition and / or functionalised biochar composition preferably removes, for example adsorbs, phosphate content within animal waste. According to a further aspect of the present invention, there is provided a method for reducing the phosphate content within animal waste, the method comprising: obtaining a biochar composition and / or functionalised biochar composition as herein described; and mixing the biochar composition and / or functionalised biochar composition with animal bedding and / or animal waste. The animal waste may for example be poultry waste, for example chicken waste. The biochar composition and / or functionalised biochar composition may be mixed with animal bedding, for example fresh animal bedding, prior to installation within an animal housing, such as for example a chicken shed. According to a further aspect of the present invention, there is provided animal bedding material configured in use to reduce the phosphate content within animal waste, the animal bedding material comprising: animal bedding; and a biochar composition and / or functionalised biochar composition as herein described. The animal bedding may comprise wood chips, straw, straw pellets, sawdust or any combination thereof. According to a further aspect of the present invention, there is provided fertilizer additive comprising a biochar composition and / or functionalised biochar composition as herein described. According to a further aspect of the present invention, there is provided a fertilizer comprising a fertilizer additive as herein described. The biochar composition and / or functionalised biochar composition of the present invention utilizes a waste product (egg shell) to remove phosphate from areas to be treated, such as water or animal manure. The waste product is non-toxic and has been upcycled and utilised to capture phosphate without producing any toxic byproducts. The biochar composition and / or functionalised biochar composition of the present invention therefore is a circular, upcycled non-toxic phosphate capturing material. Embodiments of the present invention will now be described in further details: DETAILED DESCRIPTION Example 1 - Biochar Composition The hen eggshell is dried and milled to provide hen eggshell particulate such that the maximum particle size is no greater than 2 mm. The membrane is moved using a cyclone after the drying step. The milled hen eggshell particular is mixed with biochar feedstock in a ratio of 1:1 by weight to provide a biochar composition. The biochar may be any suitable feedstock including for example one or more of agricultural waste products (such as for example manure), forestry waste product (such as for example soft plant tissue 5 or woody materials), municipal waste products, green and food waste products, or any combination thereof. Example 2 - Phosphate Adsorption of the Biochar Feedstock Composition 0.03g of the biochar composition was placed in a flask, at room temperature, containing 100 ml KHj. P04(200 mg P / L) and agitated using a stirrer. The supernatant was removed by syringe and filtered, 10 sampled and analyzed. The phosphate concentration of the biochar composition was analyzed by Mo- SB-VC spectrophotometrically method at 700nm. The biochar composition was found to provide for good phosphate adsorption capability of at least 450 mg / g, preferably at least 500 mg / g, for example about 550 mg / g. 15

Claims

19 04 241. A biochar composition formed from the pyrolysis of a mixture comprising: feedstock; and egg shell particulate free from egg-membrane.

2. A biochar composition as claimed in claim 1, in which the egg shell particulate is hen egg shell particulate.

3. A biochar composition as claimed in either of claims 1 and 2, in which the egg shell particulate is dried egg shell particulate.

4. A biochar composition as claimed in any preceding claim, in which the egg shell particulate comprises powdered, ground, crushed or milled egg shell.

5. A biochar composition as claimed in any preceding claim, in which the egg shell particulate has a maximum particle size of 2 mm.

6. A biochar composition as claimed in any preceding claim, comprising 50% by weight of feedstock.

7. A biochar composition as claimed in any preceding claim, comprising 50% by weight of egg shell particulate.

8. A functionalised biochar composition comprising a biochar composition as claimed in any one of claims 1 to 7, in which the biochar feedstock composition has been exposed to ozone.

9. A method for producing a biochar composition comprising:obtaining a mixture comprising: feedstock; and egg shell particulate free from egg membrane; andpyrolyzing the mixture to form a biochar composition.

10. A method as claimed in claim 10, in which the egg shell particulate is ground or milled or crushed or powdered prior to being mixed with the feedstock.

11. A method as claimed in either of claims 9 and 10, further comprising exposing the mixture of biochar and egg shell particulate to ozone treatment to provide a functionalised biochar composition.

12. Use of a biochar composition as claimed in any one of claims 1 to 7 and / or a functionalised biochar composition as claimed in claim 8 to absorb phosphate from a liquid.

13. Use of a biochar composition and / or functionalised biochar composition as claimed in claim 12, in which the liquid is water.

14. Use of a biochar composition and / or functionalised biochar composition as claimed in claim 12, in which the water is waste water.CM15. Use of a biochar composition and / or functionalised composition as claimed in claim 12, in which the water is river water, a lake or a well.

16. Use of a biochar composition and / or functionalised composition as claimed in any one of claims 1 to 8 to absorb phosphate from animal waste.

17. A fertilizer additive comprising a biochar composition and / or functionalised biochar feedstock composition as claimed in any one of claims 1 to 8.

18. A fertilizer comprising a fertilizer additive as claimed in claim 17.

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