Protection of the Environment by Handling, Treating and Disposal of Wastes on Dairy Farms

SESSION 2 C. Environment and the farm

Abstract

The impact of the whole chain of milk production process (from farm to table) to the environment includes all conditions from farm level to the Dairy and after until the product reaches the customer. In a dairy farm different types of wastes are produced: from urine and faeces (mainly methane, hydrogen sulfide and ammonia emissions), mixed with bedding materials (mainly wheat straw) and more or less diluted with rain waters, to dirty waters (a mixture of water, rejected milk, detergents and disinfectants) coming from cleaning and disinfecting of milking machines, cans and bulk milk cooling tanks. Agronomic use of the wastes should be reserved mainly to those with high content of nutrients and dry matter (solid phase), in order to reduce the costs of transportation and to increase the fertilizing benefits. The other wastes (liquid phase) should be treated totally or partially in order to allow them to be discharged continuously into surface water or surrounding fields. Different solutions have been tested in different countries for manure treatment. The aim of this presentation is to project some technical and regulatory information existing in different countries for handling, treating and disposal of these wastes.

INTRODUCTION

Consumers in developed countries all around the World are increasingly concerned about the environmental aspects. Referring to food production chain, people are more and more concerned that production line is undertaken in harmony with the environment. In milk production chain the main concern is that farmers produce milk in a way, which minimizes any negative effect to the environment.

A dairy farm produces different types of wastes, from urine and faeces (methane emissions), more or less mixed with bedding materials (mainly wheat straw) and more or less diluted with rain water, to dirty waters (a mixture of water, some milk, detergents and disinfectants) coming from cleaning and disinfecting of milking machines, cans and bulk milk tanks. Agronomic use of farm wastes should be reserved only to those with high content of nutrients and dry matter, in order to reduce the cost of transportation and to increase the fertilizing benefits. Other farm wastes should be treated totally or partially in order to be acceptable for discharging them continuously into surface water recipients or surrounding fields according to environmental legislation, which is becoming stricter in different countries nowadays.

COW FARMING AND THE QUALITY OF THE ENVIRONMENT

The problems caused to the environment by manure are of different nature. These problems are not like the problems caused by other means - sources, like it is industrial pollution, radioactive materials, car emissions, or others. Manure should be treated like any other by-product in the milk producing chain that includes certain good value in it. Its value has been recognized over the years as of an excellent quality, very friendly to the environment natural soil fertilizer.

A. Environmental Problems

• Smell. It is mainly referred to neighbouring residential areas and to cow farm personnel.
• Bad taste. It is referred to pasture plants. These problems are caused when non-treated manure is spread on the leaves of plants in a pastureland and gives the sense of bad taste to grazing animals.
• Plant “burning”. When untreated manure is spread on growing leafy plants could cause damage to leaves (e.g. spinach), which are turned brown and loose their value.
• Weed seeds spread out. Seeds of weeds that are swallowed by grazing cows are passing through the digestive tract, spread out along with untreated manure and then are grown on the soil.
• Hygiene. In cases where contaminated manure is coming from sick animals, infected by contagious diseases such as bovine fever, foot-and-mouth disease, etc.
• Antibiotics and various chemicals. Problems of this nature comply mainly with manure coming from monogastric animals such as pigs, hens, broilers that may receive growth-promoting factors like copper sulphate or antibiotics. In case of cow farming this is true only when rejected milk from mastitis suffering cows containing antibiotics goes together with manure and also in the case of various chemicals washed out when used for cleaning and disinfecting cow barns.
• Over fertilization. This happens in cases where manure is spread out on farmlands, in excess. The problem is serious when manure from pig houses, treated or untreated, is spread out on farm land as a fertilizer for pasture fields containing residues from copper sulphate used as growth promoting factor added in the feed of fattening pigs. It is known that grazing animals are sensitive when their feed contains copper.
• Water pollution. This is a serious problem if and when it happens. Any possible effort should be done in order to avoid such problems. No 1 step in this case is to never collect and keep manure in earthen lagoons, but only in concrete pits. In case of simply collecting manure in lagoons opened on the ground, lagoon bed should be covered by a thick and of good quality plastic sheet in order to avoid solids to penetrate deeper to the underground waters.

B. Managerial Problems

• Manure removal from inside the barn within a maximum of 12 hours (6 hours during hot weather). This is necessary in order to avoid anaerobic conditions to be developed and induce production of anaerobic gases,
• Synchronizing in & out. It is a managerial problem for the farmer who needs to synchronize and coordinate various transportation, cleaning, milking or other works that need to be done daily in a cow farm. Manure handling, removal, treatment and recycling are additional problems to his everyday activities.

C. High Investment Cost Problems

• Investment for BOD (5) reduction will be higher but necessary in cases where treated liquids go to environmentally sensitive recipients instead of being used for crop irrigation and fertilization,
• Investing for proper manure treatment will increase the fertilizing value of manure by the means of its higher content in nutrients, such as nitrates and sulphates instead of anaerobic ammonium, methane and hydrosulphate which are lost gases in the air and at the same time create a smell and an air pollution problem.

D. Social Problems

These problems are referred to the working personnel in the farm. Some of these problems are inevitable as far as smell is concerned. Other such problems could be caused when not taking all appropriate hygiene precautions and could be avoided by taking all necessary steps for regular cleaning and disinfecting the barn. The problems of this nature are:

PROCESSING AND TREATING OF DAIRY FARM WASTES

A compact installation for treating cow manure could be either anaerobic or aerobic. Anaerobic treatments lead to the production of biogass (methane), which could be used as combustible gass. By aerobic treatment organic matter of manure is oxidized and nutrients such as NO3, SO4 remain in manure for fertilization of soils. Five aerobic Solutions (from I to V) for manure handling and treatment are given below as they were elaborated in our Laboratory and are mostly suitable for Greece and for Countries having similar climatic conditions. These Five Solutions are grouped and standardize as ready answers to cow farmers according to the size of farm, its location (neighboring installations and residential areas, nature of the recipients for treated liquids, etc), financial status of the farm and local regulations. First, are given some simple answers to solve problems for handling and treating manure in small cow farms in a none expensive way, with no heavy equipment and installations required (pictures 1, 2 &3) :

FIVE GROUPED COMPACT SOLUTIONS FOR AEROBIC MANURE TREATMENT IN COW FARMS

Solution I: It is a solution suitable for average size cow farms. As it is shown in following picture 4, the installation consists of a collecting - homogenizing pit, of an aeration pit and of a depositing pit. The equipment included here is a submersible pump and a powerful floating aerator.

The working time cycle is 7 days. Fresh manure is pumped to the aeration pit once per week. The temperature needed for growth of thermophilic microorganisms is reached in 3 - 5 days. The temperature is maintained for 2 - 3 days and then starts dropping progressively. The 50% of aeration pit’s content is then pumped out to the reserve pit. This quantity of manure is replaced from collecting pit through the submersible pump. The temperature now is reached much faster, given that:

Solu tion II: For average to big size cow units. As it is seen in pictures 5 & 6 below it is the same way working solution to previous Solution I. Its function is based on the same principle. The main difference as compared to previous one is that in this solution there are two aeration pits (with two aerators), which communicate by an opening port for better and continuous two level aeration. It is a continuously functioning solution.

The degradation of biomass in manure starts at first aeration pit and continues more intensively at the second one. It is possible to have also a third aeration pit connected by the same way to the second one. As fresh manure is brought in the system from collection pit the same quantity of treated manure is overflowing from the last aeration pit to the depositing pit and remains there until is needed to be spread in fields. The capacity of depositing pit is calculated according to demands for fertilization and size of the farm. Only small quantities of fresh manure are pumped in aeration pits (10% of capacity of the first aeration pit) every 3 hours maximum, so heat losses from the system are minimized. As soon as working temperature is reached after 3 - 4 days, then it remains stabile. This system is functionally more economical as compared to Solution I, because it is continuous.

The end product is reserved in concrete or earthen reserve lagoons for up to 12 months to be used for fertilizing. Treated manure contains all nutrients in it, as all organic substances are oxidized and remain instead of being lost in the air.

Solution III: A solution adapted to bigger cow farms. Manure treated so much as to be used as fertilizer. There are two treatment levels:

Solids are removed by a screen separator (for 5 or more m3 manure/day) or by a centrifugal or squeeze separator (for more than 25 m3/day). Solid phase contains 18 - 35% dry matter by the time of separating, whilst could increase to 45 - 50% after composting for 4 - 5 weeks.

Solid phase  is then composted for a period of 35 - 40 days or it is simply turned over once a week, in order to have more oxygen within its biomass for aerobic process. Liquid phase is undergoing a thermophilic treatment in the two aeration pits and then it is reserved for later use as fertilizer, within a period of 12 months. BOD5 in liquid phase is reduced considerably, but liquid phase couldn’t, even after treatment, be rejected in sensitive recipients as lakes, rivers etc. Measurements of treated liquid phase gave pH = 8 - 8.5, D.M. = 2 - 2.5% and BOD5 around 450 mg/l.

Solution IV: This is an alternative solution for very big, industrial type cow farms that are located close to environmentally sensitive areas (tourist installations, recreation areas, beaches, lakes, etc) and don’t own land available for fertilizing. Treated liquids should be directed to surface recipients. Liquids after such an intensive treatment could be pumped to a lake, or sea waters since its BODs is very low (<20 mg/lit). The target of manure processing in these installations is to have BOD5 as low as possible.

Treated end liquids could be used, according to the potentialities and needs of the specific area where unit is located:

• to be pumped into a recipient, such as lake, sea or river,
• to be used in the farm for cleaning and washing machinery and equipment,
• to be used for nearby land irrigation, if possible.

In following picture 8 is shown Solution IV and its main equipment and installations:

Solution V: Solution V is suitable for very big, industrial type cow farms or average to big size units that their target is to reduce smell, reduce BOD5, make manure suitable for fertilizing and irrigation to their big proprietary crop land, enough surface for using all treated manure, solid and liquid, all year round. 

Solution V includes two steps:

Here below in pictures 9 & 10 it is shown a complete installation for cold aerobic treatment of manure (temperature in aeration pit no higher than 18o C in wintertime). The work cycle of this system goes as follows: All fresh manure plus waters and other liquids are collected in a collection - homogenization pit which has a capacity for two days’ collected manure. After homogenization, manure is pumped to the separator. Separated liquids with dry matter content of 2.5 - 5% are directed to a high capacity rectangular aeration pit for continuous, non-intensive aeration process. Capacity of this pit might be calculated from 1 to 9 months storage time according to the needs of the particular cow unit of using treated liquid phase for croplands irrigation. Solid phase is treated and stored in the same manner. Floating aerators might be used for aeration - stirring of liquid phase in last pit.

All above solutions proposed for aerobic treatment of manure are worked out to be the most economical and appropriate solutions for corresponding cow farm sizes.

SELECTED REFERENCES

- Ganniotis S., G. Lamprinos, 1987. Farm Machinery & Equipment. Athens. Greece.

- Kervina F. et al., 1976. System Solutions for Dairy Cows. Publ. Alfa Laval. Tumba. Sweden.

- Nikita - Martzopoulou Ch., 1985. Animal Housing. Construction & Equipment. Thessaloniki. Greece.

- Poupoulis, C. D., 2001. Handling and Treating of Animal Wastes. Recycling. TEI. Thessaloniki.- Greece.

- Proceedings from Int’l Symposium on Livestock Wastes, 1971. Livestock Waste Management and Pollution Abatement. American Society of Agricultural Engineers. Michigan. USA.

- Qasim, S. R., 1985. “Wastewater Treatment Plants, Planning, Design and Operation”, Holt, Rinehart and Winston, New York. USA.

- Reed, S. C. et al., 1995. Natural Systems for Waste Management and Treatment. McGraw-Hill. New York, 2nd Ed. USA.

- Stamoudis, B. X., 1991. Instrumental Environmental Organic Analysis (I & II). Argonne National Laboratory. Illinois. USA.

- Taiganides, E. P., 1977. Animal Wastes. Elsevier Applied Science
Pub. London. UK.

- Vogiatzis, Z. S., I.A. Stamiou, 1986. Basic principles nd designing of sludge treatment plants. T.T.E. Athens. Greece.

IDF/FAO international symposium on dairy safety and hygiene Cape Town, March 2–5, 2004, South Africa