Distillery Effluents Utilisation in Agriculture
By Dr. Yashpal Singh
For other topics related to the Distillery Sector and a review based on more than 350 publications covering Indian Distillery Industry, Manufacturing Process, Composition of Effluents, Environmental Impacts, Treatment Technologies, Utilization of Spent Wash In Agriculture, Impact On Soil, Crops And Yield, Pre-Sown Land Application, Ferti-Irrigation, Bio Composting, Soil Reclamation, International Practices in The Utilization of Spent Wash in Agriculture, Major Provisions of The Environment, Forest and Pollution Control Laws in India, Environmental Performance Rating, Major Policy Interventions and The Views Of The Honorable NGT On Sustainable Technology Adoption see Singh Yashpal 2020, Distillery Spent Wash and Its Utilization in Agriculture. Publisher – The Wealthy Waste School India. ISBN No. 978-93-5396-249-4. Pages 1 to 360 (Available at Amazon and Kindle Books)
Use of Waste Waters in Agriculture
Water security has emerged as a vital issue for India and the World. Climate change projections forecast an imbalance in water availability and a consequent adverse impact on agriculture productivity. Sugar cane a water intensive crop is expected to suffer a yield reduction of 30% in India because of water related issues. It is in this context that waste waters emerge as a potential source for meeting the water demand after essential treatment. Many industrial effluents contain variable amounts of plant nutrients. If gainfully utilized in agriculture, they have the capacity to replace the use of synthetic fertilizers which are a major environmental concern. Effluent irrigation offers a low cost alternative where both the fertilizing and irrigation aspects of the waste can be utilized and the receptors (Land, air, water etc.) and communities protected against pollution. Nitrogen, phosphorous and potassium are valuable nutrients. Waste water irrigated fields generate great employment opportunities also. Effluent reuse has been recognized as an impending reality in developing countries. Aerobic composting, vermi-culture, ferti-irrigation and one time land application have also been recognized as emerging technologies by the CPCB. Reuse in agriculture benefits nations in less pollution, avoidance or reduction of cost of treatment, savings in cost of fertilizers and reduced water management stress and costs. Sugar mill effluents increased the Electrical conductivity, Organic Carbon, Na+, K+, Ca2+, Mg2+, Fe2+, TKN, Pon3-, So42-, Zn, Cd, Cu, Mn and Cr of the soil in both the winter and summer season. The change in soil characteristics improved the fertility and enhanced the nutrient status at lower concentrations of Sugar mill effluent irrigation.
Post methanated effluents have a lower C:N ratio and degrade more swifty in soil as compared to untreated spent wash.
Controlled land application of spent wash helps in restoring soil fertility, enhances soil micro flora and improves the physical and chemical properties of soil. The saturated hydraulic conductivity and pore space of the spent wash leached soils have been observed to increase significantly with simultaneous reduction in bulk density and water disposable clay. The availability to N,P,K,S,Zn, Cu, Fe, and Mn in the spent wash amended soils was found to increase significantly. Conjoint application of spent wash and other organic amendments like farm yard manure, green leaf manure and bio compost has been tried and found beneficial under dry land conditions. Waste waters from different industries could cater to the irrigation needs of various crops.
Use of Distillery effluents as a liquid fertilizer
Ttraditionally the spent wash was used for irrigation of crops and for composting with press mud from sugar mills, as filler material. The Central Pollution Control Board (CPCB) has prescribed protocols for use of S.W. for irrigation. Two sets of norms have been developed for irrigation, one for standing crops (ferti-irrigation) and another for once a year land application before sowing of a crop (Pre-sown irrigation) with the view to standardize procedures for utilisation of spent wash for agriculture and at the same time ensure protection of the environment. Like wise requirements for surface or aerobic composting process have also been prescribed.
Distillery spent wash is a potential source of renewable energy. It does not contain any toxic heavy metals and being of plant origin and because of its rich nutrient contents may serve as a good fertilizer for crops, more effective than inorganic or mixed fertilizers being used by farmers. Distillery effluents were once regarded as the most highly polluting effluents. The energy, fertilization and irrigation potential of distillery effluents has helped the industry to build immense social acceptability now. Distillery effluents are a rich source of Nitrogen, Phosphorous and Potassium. Potassium is the most richly represented. It also has appreciable quantities of micro nutrients. Being organic in nature, the nutrients are more rapidly taken up by plants from soil. They also contain large amounts of Ca, Mg, Na, S and Chlorides which can be used as a resource for crop production and reduce the use of inorganic fertilizers. It has been stated that alternate methods of clarification in place of “Milk of Lime” in Sugar Mills may improve the quality of molasses by reducing Potassium and Sodium, rendering the usability of bio methanated spent wash (after further treatment) for agricultural applications. Some authors have observed that spent wash irrigation may also lower the incidence of insect pests. Distillery effluents have been found to be more effective than a mixture of inorganic fertilizers and cow dung manure. The current technologies of concentration incineration and concentration need heavy expenditure and the potash and other salts present may create a fouling in the evaporators and boiler heat transfer sections. The rich organic and inorganic constituents allow it to bring remarkable changes in the physical, chemical and biological properties of soil. Distillery effluents are used as a supplement to mineral fertilizer in Brazil. Nutrient recycling through the application of vinasse and filter cake to sugar cane crops in Brazil has reduced the consumption of fertilizers as compared to other crops and in other countries. The use of Urea mixed distillery spent wash is widely prevalent in Australia as a single application. Post methanated spent wash application to growing crops is discouraged, instead land application before planting is suggested to be a better option. In Australia spent wash is blended with additional crop nutrients and sold as manure. Spent wash could also be used for composting the trash in fields. Sugar mill effluents may be used as a suitable diluent for spent wash to reduce the pollution load and subsequently used in fertigation with a 1:1 dilution ratio, the BOD has been expected to come down to 3600 mg/L from 51023 mg/L, COD to 62075 MG/L from 90179 mg/L and TDS to 32700 mg/L from 72090 mg/L.
Nutrients present in the Vinasse and those obtained from the supplements in the anaerobic treatment can be recycled by using the effluents in fertigation and sludge for plant fertilization. Although Fertigation is the most feasible option for the management of stillage but the intensity of impacts depends on the characteristics of the soil and climate of the fertigated area. Appropriate time, space and rate of application of vinasse in agriculture has added significant amount of nutrients, improved the soil quality of degraded lands and increased crop yields. However, detailed management plans have been recommended to be drawn up.
Uncontrolled continuous land application has been however cautioned against as being detrimental to soil conditions.
It has been claimed that the 290 odd distilleries in India produce 40 billion liters of effluents (spent wash) per annum with an annual value of Rs. 500 crores in terms of N, P, K, and S; 150 crores for micro nutrients and organics; a Rs. 100 crores saving in the annual environmental cost; Rs. 100 crores in terms of loss to fisheries; 500 crores savings in water treatment costs, 100 crores in public health and another 100 crores in landscape costs. Energy savings in respect of the secondary and tertiary systems of treatment could be as high as Rs. 1400 crores per annum. In downstream moral areas of Vadodara in Gujarat, waste water supports annual agriculture production worth Rs. 266 million.
By using spent wash at different levels some authors have observed a substitution of 40-90% of the inorganic fertilizer cost. Some have also observed that in terms of Presown land application followed by irrigation, net returns in the treatment with only potassic fertilizer was Rs. 64630/- per ha and increased to Rs. 76183 per ha due to substitution of 50% of recommended dose of Potassium with spent wash. Spent wash application above 50% level was not beneficial.
Effect on Crops
Distillery effluents have been observed to bring about increases in yield indicators for wheat and rice. Sugarcane has been observed to withstand the application of concentrated distillery effluent without showing reduction in yield instead application of spent wash has been observed to bring about an increase in the yield. Long duration crops may need nutrients over a longer period of time. Spent wash meets the long term requirement for nutrients. Biomethanated spent wash application has found to enhance the yield in maize also. A need to balance nutrients by supplementing with other fertilizers has also been suggested. The application of spent wash has not only benefited the maize crop in supplying nutrients throughout its growth period but also favoured the growth of microbial biomass. It has generally been established that crop nutrition through chemical fertilizers is inferior to spent wash irrigation. Sunflower, soybean and grasses have all responded positively to spent wash irrigation. The application of digested spent wash to the soil either along with irrigation or as soil amendment has a beneficial effect on soil nutrients thereby increasing the uptake of nutrients by the crop and ultimate increase in crop productivity. Along with irrigation water, lower concentrations suitably supplemented with N and P appear to be more beneficial than higher concentrations. Positive yields in crop productivity have been observed in pulses. In oil seeds an increase in the protein and oil content has also been reported. Some countries have reported an increase of 45-100% in the yield of grasses, maize, fodder and beet using distillery effluents. The application of spent wash has also been demonstrated to be beneficial for the worms and insects that are essential for germination and nutrient availability. Distillery effluents have been reported to significantly increase the grain yield in maize. An ideal application was a conjunctive use of spent wash along with chemical fertilizer better than only spent wash or only chemical fertilizers.
Impact on Groundwater
In the absence of sufficient surface leaching, the use of undiluted spent wash may result in increased salinity of soil and ground water. Some authors believe that there is no consequent nitrate pollution in ground water even after sustained use of spent wash over years. Nevertheless, utilization of spent wash for irrigation needs to be pursued with caution because of the possibilities of leaching. Ground water needs to be constantly monitored as also suggested by the CPCB Protocol.
Impact on Physical Properties of soil
Diluted spent wash irrigation has been observed to improve the physical and chemical properties of the soil and also to increase the soil micro flora. When effluents are applied on soil, some contaminants get fixed in soil, others are held as exchangeable complexes where plants could utilize them, while some may leach to the water table below. An increase in the mean weight-diameter of water stable aggregates, moisture retention and available water capacity of the soil has also been reported. The soil organic carbon and potassium content along with the uptake of nutrients has registered improvements. The soluble carbon present in spent wash acts as a carbon source and also as a chelating agent supplying all required nutrient. It also binds soil particles, forms stable aggregates and improves the structure, aeration and water holding capacity. Some authors have held that tropical soils are generally deficient in organic carbon content and any addition of organic carbon is always beneficial. III effects if any are temporary and after a certain time the system gets stabilized through the degradation of organic acids. Authors have also observed that generally post harvest soils have not been recorded to exhibit any adverse impacts.
Impact on Chemical Properties of soil
The application of spent wash has been observed to increase the pH, EC, cations, anions, Sodium Adsorption ratio, Potassium Adsorption ratio, exchangeable Na and K and exchangeable Ca and Mg. Microbial degradation of organic matter in soil has also been held responsible for increased pH and nitrogen availability in soils treated with distillery effluents. The mineralization of organic matter results in an increased availability of plant nutrients including soil nitrate availability. Spent wash not only adds to the soil but also enhances the mineralization of N from organic N pool in soil. Application of distillery effluents to alkali soils increases the available P content of soil, the acidic spent wash being responsible for solubilizing the insoluble soil ‘P’ in alkali soils. Available micronutrients like Fe, Mn, Zn and Cu have been observed to progressively increase with the graded application of diluted spent wash. This is due to the direct contribution from the effluent as also the solubilisation and chelation affect of organic matter supplied by the effluent. Damaging impacts on soil chemistry at doses of 300 m3/ha or lower has generally not been observed. All observations indicate that distillery effluents are rich in plant nutrients and improve the soil nutrient status if applied on soil. Some authors have stated that in post harvest soils, pH increased by 5%, organics 48%, humic acid carbon by 16%, fulvic acid carbon by 53%, N by 48%, P by 21%, K by 320%, Ca by 221% and Mg by 90%.
Impact on Biological Properties of soil
The biological activity of soils is positively affected by the application of distillery effluents. Bacteria, Actinomycetes, Azotobacter and fungi showed significantly higher counts than in unamended soils. The amylase, dehydrogenase, phosphatase and cellulase activities have been observed to increase but the urease activity remained unaffected. When applied to the soil the color of the effluents is amenable to microbial and photo-degradation without deteriorating the biological composition of soil. Some authors have also found the presence of appreciable amounts of growth promoters like Gibberellic acid and Indole Acetic Acid in the distillery spent wash. Application of spent wash has also been observed to reduce the in cadence of some plant pests.
Impact on Nutrients and Nutrient Uptake
Spent wash application in agriculture improves the uptake of nutrients from the soil. Distillery effluents used by themselves or as supplements to other fertilizers (N and P) has resulted in the increased uptake of N, P, K, Ca and Mg from soil. Leaching of nitrate from the soil was also reduced when distillery residues were used in soil. Some authors have also observed that the application of diluted spent wash increased the uptake of Zn, Cu, Fe and Mn. Higher uptake levels have been reported at lower dilution levels. Mineralization of organic matter and nutrients in soil has been held responsible for the increased uptake.
Procedures, Practices and Guidelines
In spite of an overall beneficial impact of the use of distillery effluents in agriculture, the application has to be attempted with caution. The characteristic of effluents and the environmental impacts of utilizing in agriculture have to be carefully assessed. A continuous vigil on soil, water and crop quality needs to be maintained. Doses of fertilizers and effluents have to be fixed on crop and soil requirements. Utilisation of treated industrial effluents in agriculture has great potential as an alternate source of irrigation water. Proper treatment of effluents and agronomic management strategies have to be developed for use on a long term basis.
- Indian Distillery Industry, Manufacturing Process, Composition of Effluents, Environmental Impacts, Treatment Technologies
- Using Distillery Spent Wash For One Time Controlled Land/Presown Land Application
- Using Distillery Spent Wash For Ferti Irrigation
- Using Distillery Spent Wash For Bio-composting
- Some International Practices on the Use of Distillery Spent Wash in Agriculture
- Using Distillery Spent in Sodic Land Reclamation