GB2522835A - Compositions and methods for improving soil quality - Google Patents

Abstract

A method of increasing availability of phosphate (P) in soil comprising applying biodiesel co-product (BCP) to soil. Application of BCP may also be used to increase microbial production of extracellular polymeric substances (EPS) in soil. Preferably one or more nutrients are also added to the soil, preferably a source of nitrogen, and in one embodiment ammonium nitrate is added. In another embodiment, nitrogen is delivered in an insufficient amount such that a non-lethal retardation of weed growth results. Preferably the biodiesel co-product is the co-product formed when alcohol reacts with fatty acids of triglycerides to form alkyl ester and biodiesel co-product. Also claimed is a composition and a fertiliser composition for use in the method of applying BCP to soil.

Description

COMPOSITIONS AND METHODS FOR IMPROVING SOIL QUALITY

the present invention relates to compositions and methods for improving soil quality, in particular to compositions and methods for increasing the hioavailahility of phosphorus (P).

Many different types of fertilizer and soil amendment composition are known. however, they often suffer from drawbacks and opposition is often raised surrounding their effects on thc local environrncnt. The (global) cnvironmcntal cost of thcir production and delivery is invariably large, especially with respect to the requirement for macronutrient' P. Specifically, there is great concern with respect to the remaining inorganic reserves of P for futurc agricultural use. Current approaches to P fcrtilisation arc not sustainable. Thcsc problems mean alternative approaches to deliver the P required for crop growth. and food security, arc required.

the production of biodiesel laces opposition due to inefficiencies in agricultural production systems, especially the use omnon-renewable resources in fertilisers (most notably F). Whilst biodiesel production initially seems to be environmentally friendly, many groups believe that the costs, both economic and environmental, associated with agricultural production make hiodiesel less attractivc. Howcvcr, all agricultural products (whether food, clothing, or fuel) suffer similar problems related to fcrtiliser USC.

It is, therefore, an object of the present invention to seek to alleviate the above identified p rob I ems.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, there is provided a method of increasing availability of phosphorus (P) in soil, comprising applying biodiesel co-product (BCP) to soil.

Preferably, the method comprises applying appropriate formulations containing BCP to soil.

Preferably, thc BCP modifies functioning of the native soil microbial community towards providing bioavailable P. According to another aspect of the present invention, there is provided a method of increasing microbial production of extracellular polymeric substances (EPS) in soil, comprising applying hiodiesel co-product to soil.

Preferably, the method comprises increasing microbial production of soluble microbial products (SMP).

Preferably, the methods comprise improving soil structure and moisture retention, for example by increasing microbial production of extracellular polymeric substances (EPS).

Preferably, the methods comprise applying biodiesel co-product and one or more nutrients to soil. Preferably, the one or more nutrients arc selected from one or more of N, P, K, Ca, S, Mg, Mn, Si, B, Cl, Mn, Fe, Zn, Cu, Co, Mo, Ni, Se and Na, or a salt, complex or chelate thereof.

Preferably, the one or more nutrients are from an inorganic source of one or more of said nutrients or an organic molecule containing derivatives of one or more of said nutrients.

Preferably, thc one or morc nutricnts cornprisc a sourcc of nitrogcn.

Preferably, thc one or morc nutrients cornprisc NO3 or NH4 salts of nftrogen, acids containing nitrogen (e.g. nitric acid), urea. amino acids, peptides, or N rich wastes.

Preferably, the source of nitrogen comprises KNO3, nitric acid (11N03) or a mixture thereof Preferably, thc source of nitrogcn comprises NI-14N01 Preferably, the methods comprise applying BCP and P solubilising inocula.

Preferably, thc P soluhilising inocula arc selcctcd from Aeromonac, ,4cinetohacter, Arthrobacter, Aspergillus, Azospirillurn, Bacillus, Burkholderia. Enterobacter, Escherichia, Eupenicill/um, KIebsiella, Pantoea, Microbacterium, Mycoplana, Paecilomyces, Pen/c/Ilium.

Pseudomonas, Rhizohia and Serralia genera.

Preferably, the hiodiesel co-product and the one or more nutrients are applied at the same time.

Alternatively, the hiodiesel co-product is applied before or after the one or more nutrients.

Preferably, the methods comprise applying biodiesel co-product and a source of nitrogen to soil.

Preferably, the hiodiesel co-product and the source of nitrogen are applied at the same time.

Alternative, the biodiesel co-product is applied before or after the source of nitrogen.

Preferably, the methods comprise applying a composition comprising (i) hiodiesel co-product and (ii) one or more nutrients to soil.

Preferably, the one or more nutrients are selected from one or more of N, P, K, Ca, S. Mg, Mn, Si, 13, Cl, Mn, Fe, Zn, Cu, Co. Mo, Ni, Se and Na, or a salt, complex or chelate thereof.

Preferably, the one or more nutrients are from an inorganic source of one or more of said nutrients or an organic molecule containing derivatives of one or more of said nutrients.

Preferably, thc one or more plant nutrients comprise a source of nitrogen.

Preferably, the one or more nutrients comprise NO3 or NH4 salts of nitrogen, acids containing nitrogen (e.g. nitric acid), urea, amino acids, peptides. or N rich wastes.

Preferably, the source of nitrogen comprises KNO3, nitric acid (HNO3) or a mixture thereof Preferably, the source of nitrogen comprises N114N03.

Preferably, the methods comprise delivery of sufficient nitrogen to the soil such that the required changes in microbial activity to increase P availability to plants is supported.

Preferably, the methods comprise applying at least about 1250mg BCP per kg of soil.

In one embodiment, the methods comprise delivery of insufficient nitrogen to the soil such that a non-lethal retardation of weed growth results.

According to another aspect of the present invention, there is provided a composition for use in a method described herein. Preferably, the composition comprises (i) biodiesel co-product and (ii) one or more nutrients.

Preferably, the one or more nutrients arc selected from one or more of N. P, K, Ca, S. Mg, Mn, Si, B, Cl, Mn, Fe, Zn, Cu, Co, Mo, Ni, Se and Na. or a salt, complex or chelate thereof Preferably, the one or more nutrients are from an inorganic source of one or more of said nutrients or an organic molecule containing derivatives of one or more of said nutrients.

Preferably, the one or more nutrients comprise a source of nitrogen.

Preferably, the one or more nutrients comprise NO3 or NH4 salts of nitrogen, urea, amino acids, peptides, or N rich wastes.

Preferably, the source of nitrogen comprises KNO3. nitric acid (HN03) or a mixture thereof Preferably, the source of nitrogen comprises NH4N(3 Preferably, the C:N ratio of the composition is between about 1:1 to about 1:5. about 1:5 to about 1:25 or about 1:25 to about 1:100, depending on soil and other environmental conditions.

N can be omitted from formulation for use in soils where a large enough available pool of N pre-exists.

Preferably, the composition is applied to soil as an emulsion.

Preferably, the composition is applied to soil as an aqueous solution.

Preferably, the composition is an aqueous solution.

Preferably, the composition is applied to soil by co-dissolution in irrigation water.

Preferably, the composition comprises irrigation water.

Preferably, the composition is applied undiluted to the soil surface.

Preferably, the composition is contained in prills adsorbed into a solid matrix, or as a colloidal pellet.

Preferably, the composition is a fertilizer composition.

Preferably, the hiodicscl co-product comprises glycerol.

Preferably, the biodiesel co-product is the co-product formed when the alcohol reacts with the fatty acids of the triglycerides to form the alkyl ester and the biodiesel co-product.

Preferably, the hiodiesel co-product is obtainable by transesterification of a triglyceride with an alcohol.

Preferably, thc biodicscl co-product is untreated biodicscl co-product.

Preferably, the pIT of the biodiesel co-product is reduced prior to application to the soil.

Preferably, the pH is reduced to a level that does not cause formation of a precipitate.

Preferably, the pH is reduced to between about pH6.5 and about pHlO. preferably between about p117 and about p1110, between about p117 and about p119, between about p117 and about pHX, or reduced to approximately pH7.

More detailed information regarding the biodiesel co-product is provided below in the detailed description. It will be appreciated that all possible features of the biodiesel co-product described below arc preferred features of the hiodicscl co-product for usc in the present invention.

The nitrogen source may be inorganic, for example a nitrate, nitrite or ammonium, or organic.

Preferably, the source of nitrogen is selected from one or more of a salt of nitrogen, a metal salt of nitrate or ammonium. ammonium nitrate, acid containing nitrogen (e.g. nitric acid), multivalent inorganic salts of nitrogen, organic sources of nitrogen including urea, amino acids, peptides, or N rich wastes (e.g. fish meal, blood, and organic residues).

DETAILED DESCRIPTION

Example embodiments of thc present invention will now he described with reference to the accompanying Figures, in which Figure 1 shows that BCP maximises production of microbial EPS.

Figure 2 shows that BCI maximises production of soluble microbial products (SMP).

Figure 3 shows that the application of BCP to soil with N114N03 as a source of N increases availability of P. The present invention relates to methods for increasing the availability of P in soil and for increasing microbial production of EPS in soil, comprising applying to soil hiodiesel co-product.

The present invention describes co-formulation of BCP and nutrients such as salts of nitrogen (N) to permit application of compound bio-fertilisers' to actively growing crops (or germinating seed). Staggering the timing of the plant-available pool of N reduces the number of fertilisations required, improves nutrient use efficiency, thus minimising the carbon footprint of agriculture.

Within this specification embodiments have been dcscrihcd in a way which enables a clear and concise specification to he written, hut it is intended and will he appreciated that embodiments may be variously combined or separated without parting from the invention.

Within this specification, the term about means plus or minus 20%, more preferably plus or minus 10%, even more preferably plus or minus 5%, most preferably plus or minus 2%.

Within this specification, the term "complex" in the context of a complex of a nutrient means a chemical compound formed through bonding of ligands (non-nutrients) to a central nutrient.

the resulting molecule is often of greater soluhility or hioavailahility than the nutrient in uneomplexed form.

Within this specification. the term "chclatc" means a chemical compound (or "complex") in the form of a hctcrocyclic ring containing a metal ion aftachcd by coordinate bonds to at least two non-metal ions.

Within this specification. the term "derivative" means a compound that is derived from a similar compound by means of sonic chemical or physical process.

BCP is any waste product or by-product that is obtained when biodiesel is produced by transesterifleation of renewable lipids. Thus. BCP is also known as biodiesel waste product (BWP) and biodicsel by-product (BBP). Co-product, by-product and waste product mean any product obtained by transesterification of renewable lipids except the hiodiesel that is separated from the product of the transesterification process to he used as a fuel. BC' is largely a non-ester product.

Biodiesci is a fuel comprising C8 to C25 chain mono-alkyl esters, such as methyl ester, propyl ester and ethyl ester for use in compression ignition (diesel) engines.

Biodiesel is produced by transesterilication of renewable lipids including oils and fats, such as animal oil and plant oil including seed oil, nut oil and vegetable oil, for example, rapeseed oil and soybean oil. The transesterification process can occur without catalysation. In one example, the transesterification process is catalysed by a base, such as a strong alkaline catalyst including potassium or sodium hydroxide or an acid catalyst, such as sulphuric acid.

When the transesterification process is not catalysed. the reaction is carried out under a pressure (typically between 10 and 20 MN).

The renewable lipid can be filtered prior to use to remove any non-oil material such as dirt or charred food. In addition, water can be removed from the renewable lipid before use. This can he achieved by heating the lipid or adding a drying agent, such as anhydrous magnesium sulphate.

[he transesterilication process is the reaction of a triglyceride that is present in the renewable lipid with an alcohol, such as ethanol or methanol, to form esters and glycerol. Triglycerides are esters of free fatty acids with the trihydric alcohol, glycerol. [he alcohol reacts with the fatty acids of the triglycerides to form the alkyl ester i.e. biodiesel and BCP. BCP may contain quantities of alcohol used in excess to produce the biodiesel. Thus. BCP is obtainable by transestcritication of a triglyceride with an alcohol.

The catalyst is typically sodium hydroxide (caustic soda) or potassium hydroxide (potash), which is dissolved in the alcohol. The alcohol/catalyst mix is then added to a closed container, such as a rcaction vessel, that contains renewable lipids. The reaction mix is kept between 50°C and 300°C to speed up the reaction, with 75°C being the upper limit of un-pressurised vessels. The recommended reaction time varies from a few seconds to 8 hours depending on temperature and pressure.

Once the reaction is complete, two phases exist: hiodiesel and BCP. I'hc BCP phase is denser than the biodiesel phase and therefore the two phases can be gravity separated, with BCP simply drawn off the bottom of the settling vessel. A centrifuge can be used to separate the two materials at a faster rate.

Subsequently, residual BCP can be removed from the hiodiesel phase by washing the biodicscl phase with water. Thus. BCP in accordance with the invention includes biodicsel wash water. Wash water is the same as wastewater.

Residual I3CP can he removed from the hiodicsel phase by static washing, mist washing and bubble washing, or sorption onto an ion exchange resin (followed by removal). Static washing involves placing biodiesel and water in a tank without mixing. BCP moves from the hiodiesel phase to the water over a period of time, for example, 2 hours or over, het%vecn 2 hours and 48 hours and 4 hours or over. Mist washing involves spraying water over the top of the diesel and letting the water settle down through the biodicscl collecting BCP. Bubble washing involves adding a layer of water beneath the hiodiesel and forming air bubbles in the water. I'he water is dragged up into the hiodiesel in a small layer around the air bubble, which falls back down through the hiodiesel, collecting BCP, when the bubble bursts at the top of the tank.

Excess alcohol may he reclaimed from the BCP before the BCP is applied to soil, for example, by distillation and this alcohol can later he used for further hiodiesel production.

BCP is water soluble and comprises glycerol, preferably between about 10% and about 95% glycerol. In one embodiment, UCP comprises about 20% or more glycerol, preferably between about 30% and about 95%, between about 40% and about 95%, between about 40% and about 60%. between about 50% and about 90%, between about 50% and about 80%, between about 50% and about 70%. between about 60% and about 90%. between about 60% and about 70% or between about 70% and about 80% glycerol.

BCP can also be defined as glycerol that comprises about 0.Olwt% to about SOwtVo impurities preferably about 0.01 wt% to about 45wt%, about 0.OSwt% to about 4Swt% or about I wt% to about 45wt%.

BCP can additionally comprise potassium or sodium salts of thc organic acid from thc triglycerides i.e. soap, alcohol and/or hiodiesel. Quantity varies between about 1% and about 20% depending on the free fatty acid (F'F'A) content of the feedstock lipids, degree of water contamination, and the catalyst used.

The non-water component of BCP comprises from between about 40% and about 80% carbon. Tn one embodiment of the invention, the non-water component of BCP comprises between about 20% and about 70% carbon, preferably between about 30% and about 60%, between about 30% and about 55%. between about 40% and 55%, between about 20% and about 60%. between about 30% and about 70%, between about 40% and about 70%. or between about 50% and about 80% carbon.

BCP including watcr can comprisc up to about 80% carbon. In onc embodirncnt. BCP including water comprises between about 5% and about 80% carbon, preferably, between about 10% and about 80%, between about 10% and about 70%, between about 20% and about 70%, or between about 20% and about 60% carbon.

The application of BCP to soil can correspond to the addition of about 100, about 150, about 200, about 300, about 400, about 500, about 1000 or more mg C kg' soil.

In one embodiment of the invention, the pIT of the BCP is reduced prior to application to the soil. The p1-I can be reduced to between about pH6.S and about pHlO. preferably between about pH 7 and about pH 10, between about pH7 and about pH9, between about pH7 and about pHS, or reduced to approximately pH7. Acids containing nitrogen, including nitric and nitrous acids can be uscd to reduce thc pH. The pH of the BCP can be ncutraliscd.

BCP can be diluted before application to the soil, for example, by water. In addition. BCP can be combined with wastewaters from other sources before application to the soil, for example, olive oil mill wastewater.

The BCP and compositions of the present invention can he applied to soil at any time of the year. In one embodiment, I3CP is applied to soil in the first or second month after crops are harvested. In regions that experience seasonal fluctuations in climate. BCP can be applied to the soil when the climate is turning cooler following the warmer period of the year i.e. in autumn. Autumn means approximately September, October and November in the northern hemisphere. In the southern hemisphere, auLumn means approximately March, April and May. In all regions including regions that do not have seasons, such as territories near the equator. BCP can equally be applied to the soil after (i.e. one, two or three months after) crops are harvested, or immediately preceding, or simultaneous to the sowing of a crop or at any time of the year.

The BCP and compositions of the present invention can be applied to any type of soil, such as sandy soil, silty soil, clay soil and loamy soil. In particular, the BCP can be applied to soil that is used to grow crops i.e. arabIc or agricultural soil, garden soil and forest soil, for

example.

The BCP and compositions of the present invention can also be applied to soil that is not used to grow crops at the time of application of the BCP. For example, in the northern hemisphere, the BCP can he applied in the autumn or the beginning of the winter, even in the absence of crops.

The present invention shows that application of BCP to soil increases BPS and SMP production and leads to an increase in the availability of. p is a non-rencwable resource, the acquisition of previously unavailable P from soil minerals means that less phosphate is required in fertiliser formulations.

As described herein, UCP has been shown to increase microbial production of extraeellular polymeric substances (EPS) in soils and to increase available of P. Increased EPS production can lead to increased phosphate availability through two mechanisms: (i) EPS and SMP are rich in charged polysaccharides. proteins, and amino sugars and DNA which can substitute (previously unavailable) inorganic phosphorus from iron, calcium and aluminium minerals.

(ii) The EPS and SMP moieties ehelate the cations bound to the phosphorus -thereby increasing its hioavailahility.

iii) Furthermore. EPS enhances the lifespan and functioning of microbial enzymes. Examples of enzymes which can cleave inorganic phosphate from organic matter include phytases, nucleases and phosphatases.

In this way, BCP increases available phosphate from both organic and inorganic reserves in soil.

Increasing EPS in soil can also have beneficial effects on soil structure and on moisture retention.

[he present invention provides a cheap, readily available, soluble material that can he applied to soil to improve soil quality, decreasing the cost of applying annual fertilizer to crops, increasing soil organic matter, so improving soil structure, thereby decreasing tillagc costs and increasing carbon sequestration, so decreasing overall COn footprint.

Compositions of the present invention can he delivered to soil via irrigation or tractor-mounted dribble bars/trailing hoses.

By way of illustration and summary, the following scheme sets out a typical process in which BCP can he applied to soil: BCP, obtained as a by-product when biodiesel is produced by base-catalysed transcsterification, is separated from the hiodiesel. [he catalyst may he dissolved in methanol, in which case, after the reaction, sonic or all of the methanol is reclaimed from the BCP. The biodicscl is then washed with water to remove traces of BCP and the wash-water, which is also BCP. is stored in an open container to allow some of the methanol to evaporate.

Optionally, the BCP (both the BCP initially scparatcd from thc biodiesel and the BCP wash-water) can be adjusted to pH 7. If the pH is adjusted then it is preferred that this does not result in formation of a precipitate. The BCP initially separated from the biodiesel can be combined with the BCP wash-water, although equally, both sources of BCP may he utilised separately, depending on processing setup and suitability at the location. The aqueous or undiluted BCP is then applied to soil, with or without one or more nutrients.

EXAMPLE 1

the results on EPS production and soluble microbial products (SMP) production obtained after applying BCP and glycerol to soil are shown in Figures and 2. Each treatment was given at rates of 20 mg BCP-C or Glycerol-C g1 soil. All treatments included co-application of N (1.5 mg g1 soil). The soil was a sandy Cambric Arenosol 1.69% Organic C content.

After incubating for 8 days in the dark at 25 degrees C, flushing daily with a leaching solution. SMP was extracted using dilute calcium chloride extractant. EPS was extracted using cation exchange resin. Total EPS is given as the sum of proteinaceous and saccharidic material. Increases were of high statistical significance (p <0.01).

EXAMPLE 2

The results on available P obtained after applying BCP to soil, with NH4NO3 as a source of N arc shown in Figure 3. BCP was applied at rates of 0, 125, and 1250 rng BCP kg' soil, and incubated for 1 week. Soils were then placed in glass tubes and water passed through at a 1:1 ratio. P in the water was quantified and reported as a concentration in soil (rng P kg' soil).

the concentration of available P at the highest I3CP concentration was greater than the other two treatments by a statistically significant margin (greater than the least significant difference after ANOVA; p < 0.05).

It should he understood that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the present invention and without diminishing its attendant advantages. It is therefore intended that such changes and modifications are covered by the appended claims.

Claims (17)

1. CLAIMSI. A method of increasing availability of phosphate (1') in soil, comprising applying hiodiesel co-product (BCP) to soil.
2. 2. A method of increasing microbial production of extracellular polymeric substances (EPS) in soil, comprising applying biodiesel co-product to soil.
3. 3. A method according to claim 2, wherein the method comprises increasing microbial production of soluble microbial products (SMP).
4. 4. A method according to any preceding claim, comprising applying hiodiesel co-product and one or more nutrients to soil.
5. 5. A method according to claim 4, wherein the one or more nutrients comprise a source of nitrogen.
6. 6. A method according to any of claims I to 4, comprising delivery of insufficient nitrogen to the soil such that a non-lethal retardation of weed growth results.
7. 7. A method according to any preceding claim, wherein the biodiesel co-product is the co-product formed when alcohol reacts with fatty acids of triglycerides to form alkyl ester and hiodiesel co-product.
8. 8. A method according to any preceding claim, wherein the pH of the biodiesel co-product is reduced prior to application to the soil.
9. 9. A method according to claim 8. wherein the pH is reduced to a level that does not cause formation of a precipitate.
10. 10. A method according to claim H or 9, wherein the pH is reduced to between about pH6.5 and about pHI ft
11. 11. A method according to any of claims 5 to 10, whcrcin thc sourcc of nitrogen is selected from one or more of a salt of nitrogen, a metal salt of nitrate or ammonium, ammoniurn nitrate, acids containing nitrogen (e.g. nitric acid), multivalent inorganic salts of nitrogen, organic sources of nitrogen including urea, amino acids, peptides, or N rich wastes.
12. 12. A composition for use in a method according to any preceding claim.
13. 13. A composition according to claim 2, comprising (i) hiodicsc! co-product and (ii) onc or more plant nutrients.
14. 14. A composition according to claim 13, whercin thc one or morc plant nutricnts comprise a source of nitrogen.
15. 15. A composition according to claim 14, wherein the source of nitrogen is selected from one or more of a salt of nitrogen. a metal salt of nitrate or ammoniurn, ammoniurn nitrate, acids containing nitrogen (e.g. nitric acid), multivalent inorganic salts of nitrogen, organic sources of nitrogen including urea, amino acids, peptides, or N rich wastes.
16. 16. A composition according to any of claims 12 to 15, whcrcin thc composition is for application to soil as an aqucous solution.
17. 17. A composition according to claim 16, wherein the composition is an aqueous solution.

    IS. A fertilizer composition according to any of claims 12 to 17.