FARM WASTE DISPOSAL PROJECT BEGIN

Press, Volume CXIV, Issue 33513, 19 April 1974, Page 8

FARM WASTE DISPOSAL PROJECT BEGIN

Professor J. Pos, of the faculty of the School of Engineering at the University of Guelph in Canada who leaves Christchurch today on the way back home, has set up a research project at Lincoln which he hopes will help New Zealand farmers in the satisfactory return of liquid animal wastes to the soil.

He has been at the agricultural engineering department at Lincoln College and the New Zealand Agricultural Engineering Institute at Lincoln under a fellowship from the college to help with the development of an academic and research programme in waste management. Professor Pos said this week that he agreed that farm wastes should be put back on the land but this should be done in such a way as not to contribute to pollution of the air, water, including ground water, and the soil. While not a lot of water was derived from bores in Canterbury he said that people- were looking at underground water as a source of further water supply and consequently care had to be taken to ensure that such supplies were not polluted. Similarly there was now a Clean Air Act and people could have legitimate complaints about odours resulting from mismanagement of waste management systems.

The next question that would obviously be raised by farmers, he said, would be how farm effluents or wastes should be returned to the land. On the basis of discussions he had had with students in the presentation of an academic course in w’aste management and from observations in the field. Professor Pos sasd that he had found that farmers would prefer to do this through irrigation than by way of field tankers, which was contrary to North American practice, but many fanners already had irrigation systems and wished to use them for this purpose also.

But unfortunately from what he had seen in New Zealand a farmer set up his irrigation equipment to distribute effluent but was then somewhat remiss or negligent in shifting it. The result was that he sealed the surface of the soil with solids so that the effluent w'as ponded on the paddock, and under conditions of anaerobic decomposition foul odours were generated. If such a farmer’s property was close to an expanding municipality the citizens would have legitimate cause of complaint. Some of the larger farmers, he added, also did not have sufficient irrigation equipment to carry these materials far from the cowshed. for instance, so that it was only the paddocks nearby that received treatment.

In North America, Professor Pos said that in general wastes had to be returned to the land, but to avoid pollution they could not be applied when the ground was frozen and that was for three or four months of the year, so that there had to be storage of the wastes. Professor Pos said that in New Zealand also he did not think that wastes should be distributed every day. There would be times, for instance, when soils were at field capacity for moisture.

And also to recover some money from the handling of the material it should be treated as an organic fertiliser to supplement commercial fertiliser and there

must be times of the year when a growing crop was best treated with fertiliser. In North America they liked to feel that the spring and the fall or autumn were the best times to spread this material, so that many farmers had sufficient storage to hold effluent for six months.

This sort of operation meant that farmers could share equipment for its distribution or use contracting services, which could as well as being able to distribute the effluent have customers that would take the material if the farmer himself did not wish to have it spread on his own property. Under New Zealand conditions Professor Pos believes that there should he at least limited storage for, say, at least two w'eeks. This would overcome one of the problems involved with irrigation of effluent. Animal manures have 25 to 40 times the solids content of raw' domestic sewage and with this high solids content there is a problem with blockages of irrigation equipment. In storage there is a breakdown of these solids so that a reduction of blockages in irrigation systems could be expected.

But if such wastes are held without some treatment the decomposition of the material under anaerobic conditions will produce

foul-smelling odours, but if oxygen can be introduced into the material the decomposition that takes place under aerobic conditions produces no methane gas and very much less foul-smelling hydrogen sulphide and thereby offensive odours can be controlled.

initially experiments were carried out at Lincoln using a model tank holding 60 litres of liquid and some : 15 different models of surface aerators were used to introduce air, including oxygen, into the liquid. Some problems were ; faced in developing a satis- . factory system. Equipment : used for this purpose in i domestic sewage is in- , adequate in farm wastes because of the very much greater solids content. It was also necessary to develop a surface aeration system that would operate at varying levels of material in the tank. This problem has been overcome by use of an aerator that floats, so adjusting itself to the level of the material. Because of the solids content of farm wastes it also has to be self-cleaning so that it does not clog up.

Now the “model” system is being applied in a prototype tank of 24,000 gallons set up on the research farm at the college. Piggery wastes are likely to be the first to be used in it. An 800-gallon tanker has been built to move the wastes, and if necessary to spread them as well as by irrigation on adjoining paddocks. This work will now be carried on by Dr David Hills. Professor Pos says that he was disappointed with the response to a questionnaire that he sent out to farm advisory officers involved in the engineering aspects of waste disposal soon after he arrived. At the time he was hoping for information about field problems that would help in de-

veloping a meaningful research programme. He found that the majority did not acknowledge that there were any problems, and he said it seemed a shame

that people in the Government service were not able to anticipate impending legislation in the pollution area and the impact that it might have on their regions. Following classification of natural waters, which would be completed in a year, he said that the likelihood was that manyfarmers would not be able to continue to discharge effluents into natural waters and farm advisory officers would be receiving many requests from farmers for assistance with their waste disposal problems and about the alternatives that might be available to them. Some such officers, he added, were however attempting to solve these problems. After a pollution confer-;

ence in June last year at Wairakei when more than 50 technical papers were presented by representatives of many different organisations, Professor Posi

said he had been impressed: by the awareness of the! problem in this country, but he had been disappointed at the lack of; follow-up since and he says! that ' scientists seem to have gone back to working in isolation. He associates this with the subsequent establishment of the Ministry of the Environment and “die backing off” of the Department, of Scientific and jndustrial Research which had seemed to be providing, the leadership at Wairakei. In ' a . cereal producing! area like Canterbury Pro-! fessor Pos sounds a note of! warning that there could be. a dramatic heightening of: animal waste disposal problems in the future with al

concentration of animals like pigs and also cattle in feedlots based on grain feeding.