the effluents, discharged from distillers in which alcohol is produced by molasses of sugar factory, contain plenty of contaminants. these effluents cause serious pollution when they are drained into rivers. with more and more emphasis on environmental protection in modern society, some molasses alcohol plants have to stop production or decrease its output. for many years, the treatment of these effluents has been an important problem for the world's technologists. on the other hand, these effluents contain quite much organic substances and nitrogen, potassium and phosphate, as well as some kinds of trace elements. as it is well known, these components are useful materials if they can be made into fertilizer. however, the production of fertilizer from these effluents is still not applied commonly since this process involves some complicated technical problems that are quite difficult to solve in practice.

with the cooperation of the environment protection organization, our specialists have made extensive researches on this problem for many years. several processing methods and different kinds of equipment have been tried and applied. based on the settlement of the relative problems, a new technique has been developed and put into production successfully. up to now, several thousand tons of solid organic basis fertilizer and organic compound fertilizer to meet the needs for different crops have been produced. five-year application tests on vast fields of several main crops have proved that these fertilizers are effective for the growing of crops. obviously, the production of organic fertilizer from alcohol effluents, converting harmful wastes into useful materials, has a positive effect both on environmental protection and increasing the wealth of society.  

1. principle situation

13-16 tons of effluent is discharged from the distiller while 1-ton alcohol is produced from molasses. it has a dark brown color, and is acidic with a ph 3.8-4.5, contains 9-13% of dry matter with a very high cod and bod as 50000-100000 and 20000-50000 respectively. the dry matter existing in this effluent is mostly organic substance, which mainly consist of carbohydrates and yeast cell, as well as plenty of nitrogen and potassium. their contents vary with the soil and fertilizing conditions and the variety of sugar cane.

putting these effluents into the process of concentration, degradation of high molecular substances by acid, neutralization by alkaline and then drying, it turns into a good organic basic fertilizer, which usually contains 20-28% of humic acid, 5-7% of nitrogen, 4-6% of k₂o and some phosphate. when applying as a fertilizer, it makes the soil loosening, more porous and less hardening, enhances the activity of fungus and nitrogen-fixing bacterium, and increases the fertility of the soil, improves the nutrition conditions of the crops, increases its yield.  furthermore, according to the needs of various crops (such as sugar cane, fruit tree, rice, vegetables and flowers), different kinds of organic compound fertilizer can be produced by adding proper amount of inorganic fertilizer to raise the content of n, p, k to suitable extent, and a little trace element component such as borax, zinc sulfate and ammonium molybdate, much better results can be achieved.  

2. production process

the basic procedure of producing organic fertilizer from these effluents is described as follows:

1. the effluents drained from the distiller enters a clarifier in which the insoluble matter settles down by itself, then the clear liquid flows out from the upper level. the mud is added to the fertilizer in the later stage.

2. the clear liquid is pumped to multi-effect plate-style evaporators to concentrate to a density of 65-70ºbx.

3. a suitable proportion of sulfuric acid is added to the thickened liquid. hydrolysis occurs under proper conditions, which makes the high-molecular organic substances degrading.

4. the digested liquid is neutralized with adding alkaline, and then mixed evenly with suitable amount of bagacillo and other solid additives.

5. the mixture is dried in a dryer by hot air coming from an air oven burning coal, getting organic basic fertilizer.

6. this basic fertilizer can either be packed as product for sale, or be further processed into organic compound fertilizer by mixing it in a double-shaft mixer with proper proportion of inorganic fertilizer and trace elements, according to the composition required, and then pressing into pellets by a pellet-press.

7. the fertilizer is packed in the plastic-weaving bag with an internal pvc bag, each containing 40 or 25 kg.

there exist complicated technical problems in these processes. our new methods solve them well, and lower the equipment and operating cost.

the sorts of product and their ratio should be decided in accordance with the local requirement. generally, basic fertilizer is recommended during the first stage and compound fertilizer can be developed later.

3. consumption of main raw materials and utilities

3.1 organic basic fertilizer

        effluent                                             4-6 m3

        sulfuric acid (industrial grade)              0.03-0.05 tons

        neutralization agent                            0.05-0.07 tons

        solid additives                                   0.2-0.25 tons

        steam                                               1.5-2 tons

        electric power                                    45-55 kwh

        coal                                                  0.1-0.13 tons

        water                                                22-25 m3

        packing bag                                        25 pieces

3.2 general organic compound fertilizer

the ingredient of this fertilizer is depended on the crop variety and the local soil condition. the fertilizer used for paddy and vegetables usually contains 6% of humic acid, 12% of n, 4% of p₂o₅ and 8% of k₂o; and that used for cane, 10% of n, 6% of p₂o₅ and 11%of k₂o. therefore, the formulation in the fertilizer production has to be decided in accordance with the composition of the local effluent. generally, 250-300 kg of basic fertilizer is needed for making one ton of compound fertilizer, with other inorganic component and additives.

the special formulation for each crop is decided separately.

4. the application of organic fertilizer from effluents on crops

the organic fertilizer made from alcohol effluents has been used in several sorts of crops such as sugar cane, orange trees, rice, vegetables, tea trees and flowers etc., and good results have been achieved in every application.

trials have been made to compare the effects in large area of cane fields by using different fertilizer with the same level of n, p, and k, under the same conditions. for stubble cane, the average output of cane per hectare was 132 tons when adopting effluents fertilizer, comparing that of 103.5 tons of cane for common fertilizer, showed an increment of 27%. and for plant cane, the average sugar content reached 15.04% when adopting this fertilizer, comparing that of 13.46% for common fertilizer, obtained an increment of 11%.

the trials in orange fields indicated that the output raised 3.9-8.5% by adopting effluent fertilizer at the same level of n，p，k added. analysis of the n，p，k content in the trees and leaves showed that the absorbing efficiency of these elements increased when effluent fertilizer was used, and that of n raised 7.2%, p 3.1%, k 15.5%.

tests were made with 150 pots of orchid that were divided into 3 groups applying different sorts of fertilizer separately, and the results showed that the group applying effluent fertilizer grew best.

the application of this fertilizer to the tea trees and several sorts of vegetables fields also got satisfactory effects.

in the past decades, more and more chemical fertilizer were produced and used in many countries, while the application of traditional organic fertilizer (such as excretes of animals and green fertilizer) apparently reduced.  hence, large areas of soil contained less organic substances, and the situation of soil got worse and even hardening. these led to a significant reduction of crops output. on the other hand, as the soil situation changed, more fertilizer flowed out from the soil when raining. this reduced the efficiency of the fertilizer used and brought about pollution. for this reason, many agriculture specialists have emphasized much in recent years that it is very important to use more natural organic fertilizer and green fertilizer to improve the soil situation. the alcohol effluents provide very rich resources of organic substances. from 1 million tons of sugar cane, the alcohol effluent can produce 25-30 thousand tons of organic basic fertilizer, getting great benefit.

summary

the production of organic fertilizer from effluents solves the difficult problem of its pollution, and recovers a lot of effective materials:  organic substances, nitrogen, potassium, phosphate and other trace elements, provides large amount of cheap and high effective fertilizer for the soil to increase the out put of crops.  this forms an ideal circle in nature. this new technique has been used in industry and agriculture successfully. obviously, it is of great significance and has vast prospects.