DISPOSAL OF COMPOST

Te Awamutu Courier, Volume 77, Issue 6568, 20 September 1948, Page 5

DISPOSAL OF COMPOST

UTILISATION OF ORGANIC WASTES

MUNICIPAL SCHEME AT DANNEVIRKE

[Written by Mr H. A. Truman, borough engineer at Dannevirke, and reprinted from “Board and Council.**]

It was referred to by Mi T. H. Millar, town clerk, at last week’s meeting of the Te Awamutu Borough Council ■when he (along with the Mayor, Mr G. Spinley) reported on their visit to Dannevirke recently.

Modern civilisation has taught us to look upon all kinds of town wastes as something to dispose of as quickly and conveniently as possible,, and modern sanitation has erred badly in thinking in terms of sewage and refuse disposal instead of sewage and refuse reclamation or utilisation.

There is, however, a small but steadily growing body, comprising scientists, engineers, agriculturists, medical practitioners and laymen, who have been drawing attention to the great quantity of organic wealth which is being lost from our dust bins and sewage works. Parallel with this small body of opinion concerned with the waste that is taking place by modern methods of sanitation there is another small but well-informed and influential group drawing attention to the lack of humus in the soil and the consequent need for the building up of the humus content of the soil by every means possible in order to maintain soil fertility. Soil Fertility Soil fertility is of paramount importance in the world of to-day, especially with the grave food situation; in fact, it could be argued that soil fertility may well be more important to us than social security, for a pension is of very little, value after all, if there is not enough food to buy. Dr Hugh Hammond Bennett, the chief of the Soil Conservation Service, United States Department of Agriculture, stated on 24th June, 1943: “Many people believe the world’s supply of productive soil is practically endless. Nothing 'could be further from the truth. “Actually, the available supply of productive land for all mankind is severely limited. “Only about 11 per cent, of the earth’s total land area is capable of cultivation now or in the immediate future.

“Thus the world to-day faces a scarcity of productive soil. Some two billion people depend for sustenance on only four billion acres. “Moreover, the supply, already so limited is steadily shrinking. “And that isn’t all; by no means all of this four billion acres of land is good land. Millions of acres have been practically exhausted by centuries of continuous cultivation and

erosion.” A perusal of the foregoing statement by Dr H. H. Bennett should convince any thinking person that the problem of improving the fertility of the soil is one, of urgency and demands immediate action. It therefore behoves all who can in any way contribute to the solution of this problem, no matter how small their contribution may be, to do so, as neglect could have disastrous consequences even in the lifetime of the present generation. It is becoming almost universally recognised that humus is an integral part of soil fertility; this contention is supported by acknowledged authorities on soil fertility all over the world. As humus is so important in relation to the soil the question naturally arises in one’s mind as to what attempt, if any, could be made to increase the much needed supply of humus. At this stage it would be of interest to examine the, opinion of a few reliable authorities on the subject of orthodox methods of the disposal of municipal organic wastes and the possibilities of returning these wastes to the land. Lieut.-Col. F. C. Temple, C.1.E., V.D., M.lnst.C.E., M.LMech.E., F.1.5.E., F.R.San.I., a leading British consulting engineer, stated as follows in 1936: “. . . . that engineers who had to deal with sewage or town refuse were not doing their job properly until they got products from both back on to the land.” The British Ministry of Agriculture Bulletin, 1936, entitled “Manures and Manuring,” and published in 1936, contained the following statement: “When account is taken of the large sum that is spent annually on the collection and disposal of refuse, more towns might well afford to devote some money to the conversion of this material into fertilisers.” The New Zealand Economist and Taxpayer, under date of May, 1942, in an editorial entitled “The War Against Waste,” pointed out that the war against waste appeared never to have been taken seriously in New Zealand, and among other things stated as follows:—“There is, however, one serious problem looming up and that is the waste of household refuse that is going on still. Kitchen refuse is being destroyed when it should be conserved to be turned into compost. “Unfortunately the machinery for destroying refuse is now limited by reason of the shortage of manpower and as a result the increase in blue bottles and rats is becoming noticeable.

\ “From a health standpoint the > dumping of waste material on open ground, roadways and riverbanks should be discouraged by close inspection and heavy penalties. “But that is only a negative way of dealing with the problem. A more radical plan should be pursued.” The article then goes on to suggest that the men employed on the then No. 13 scheme should have been diverted to the collection of kitchen refuse from municipalities for the purpose of composting this material. Then under date of November 17th, 1943, this paper (i.e., “Board and Council”) in an editorial stated as follows: — “The fact .that the Humic Compost Club, formed only in 1941, has now a surprisingly large membership for an organisation so young is ample proof that more and more New Zealanders are becoming compost minded. If local bodies and the State would put their

weight behind a movement of this sort by enforcing the saving of waste, then there should be a vast improvement in the condition of the soil. It is understood that the Department of Scientific and Industrial Research is working on humus as a fertiliser of soils, but so far as is known, most local authorities have not interested themselves as yet. A great number of them are still throwing rubbish into pits or into the furnace. Great Britain is converting vast amounts of waste into humus and returning it to the soil with remarkable results, and the local bodies are mainly responsible. What an opportunity to help raise the standard of health in New Zealand the local bodies are overlooking.” The foregoing opinions, which are but a few of many that could be quoted, should suffice to arouse some interest in this important subject. Modern Methods of Disposal Compared

Ample technical literature is available on refuse, and sewage disposal. Only a few points will be touched on here.

(1) For smaller boroughs, controlled tipping is usually a very expensive and uneconomic method. Firstly, because considerable quantities of soil have to be carted for cover. (In Dannevirke the top soil is very shallow and difficult to obtain in large quantities.) Secondly, in order to run a controlled tip efficiently at least one man must be on the job the whole time. In the smaller towns there is not'.sufficient work to keep a man fully employed, but should he be taken away, a load of refuse may be dumped and not immediately sorted and covered. The system then breaks down, as it is no longer controlled tipping. (2) Where low-lying or waste land can be reclaimed and put to a useful purpose, controlled tipping is preferable to incineration, but in many ways less desirable than composting. (In Dannevirke there is little land suitable for reclamation although there is adequate land available to meet the development of the town for many years to come.) (3) Sewerage sludge is difficult to dispose of because of its very high moisture content.

Possibilities of Utilisation The statement by Lieut.-C'ol. Temple quoted earlier caused the author to give much thought to the matter. From the three points enumerated it appeared that controlled tipping was usually superior to incineration, hut that composting would be a still better method.

Moreover, composting required a good deal of moisture, and a composting scheme using sewage sludge and effluent appeared the logical method of utilising the major part of the borough wastes. Small Scale Experimental Work

In 1943-44 small scale municipal composting was started on the Dannevirke Domain, using slaughterhouse, and fish shop wastes, hotel garbage and garden wastes from the Domain. The compost produced gave excellent results when used on the Domain flower beds. It was obvious, however, that considerable modification would be required to the technique used in this experimental work, before such materials as fish waste, and offal could be safely handled. Further no sludge could be used at this site. Large Scale Experimental Work

In October, 1946, further experimental work was commenced on a large scale. At the new site the whole output of sludge and effluent from the borough’s one septic tank can be gravitated to the heaps.

It should be stressed that although the present operations have been most successful, nevertheless, they are still definitely in the experimental stages. The system was evalued primarily as a means of disposing of difficult municipal organic wastes. However, the possibility of producing an organic fertiliser with a market value was also envisaged. At this stage it is apparent that the scheme has definite economic possibilities, also that it affords a most satisfactory and hygienic means of disposing of three unpleasant and refractory municipal wastes, i.e., sewage sludge, town refuse and slaughterhouse waste; also that a valuable organic manure results, which is readily saleable. Type of Materials Used

Abattoir and slaughterhouse waste. Fish shop garbage. Hotel and boardinghouse garbage. General town refuse. Sewage sludge and effluent from borough septic tank. Street grass and cleanings. Dead animals, i.e., horses, cows, cats, dogs, etc. Skin pieces and trimmings from wool stores. Waste paper from departmental stores and shops. Sawdust and shavings. Domain refuse, i.e., lawn clippings, leaves, weeds and hedge clippings, etc. Wood ash. In fact, anything which is organic in its origin. All the above wastes have been successfully composted in the Dannevirke scheme. Of particular interest in this connection is the disposal of omasums, or more commonly known as “bibles” or “books,” these being the third stomach of a beast and occur in slaughterhouse wastes. Normally, these are particularly difficult to dispose of and cannot be successfully destroyed by ordinary burial or burning. Omasums were exhumed after six years of burial and were found to have undergone very little change in structure during that period, whereas when disposed of by composting were completely decomposed, as were dead horses, cows and fish shop garbage, in six weeks. Methods Adopted The basic idea behind composting is that raw material is decomposed outside the soil, an imitation of soil conditions being arranged in the heap or pit. The conditions are: Aeration, non-acidity, moisture, but not sodden wetness, warmth and nitrogenous food for the bacteria. The various schemes for composting are based upon the provision of these favourable conditions. The great advantage of the compost heap over decomposition within the soil is that the heap can preserve, even in winter, very much higher temperatures, so that the speed of humus production is much accelerated. Raw organic matter in the soil will be very slowly decomposed during the winter months. It is the author’s experience that

much higher temperatures are generated and maintained over long periods in the Dannevirke heaps than could be expected in either the small domestic compost heaps or in the soil, naturally. Generally, the method used is an adaptation of the Indore system as pioneered by the late Sir Albert Howard.

Heaps are built above, ground level and are provided with adequate ventilation, using 4in and 6in field tiles. The average size of each heap is 10 to 12 feet wide by 30 feet in length, and it is built to a height of from 5 to 6 feet. The actual size of a heap is very largely determined by the material available at the particular time.

These heaps are contained in sod walls obtained from the. grading of the flanks of streets; these walls are 2ft 6in high. It is hoped to replace these sod walls with either brick or concrete.

The material is placed in the bins in thin layers and dusted with carbonate of lime and soil, followed by a covering of sawdust, shavings or partially matured compost, then moistened with sludge and effluent from the borough septic tank. Upward of 50,000 gallons of sewage has been applied to the heaps. Temperatures in the vicinity of 150 degrees F.-160 degrees F. are registered and maintained for long periods of up to four months, both summer and winter.

The maximum temperature registered is 184 degrees F. Each heap is turned at least twice and the material is ready for disposal after some six months when its temperature is down to 60 degrees F. At this stage numerous earthworms are to be found in the piles. The necessity of turning heaps has, on numerous occasions, been clearly demonstrated. To take one instance only, this heap after it was completed did not register a temperature of more than 90 degrees F. for two months; it was then decided to turn it and immediately on turning the temperature rose to 150 degrees F.-160 degrees F., where it remained for two months. The author is of the opinion that a regular turning is an essential feature of the process and the success of municipal composting depends very largely on this factor. The turning is carried out by means of a specially-designed power-operated machine. The heaps are moistened with effluent and sludge from the borough septic tank as each layer of material is put down, also immediately after turning and as is found necessary to maintain a moisture content of 50 per cent, to 60 per cent., also to maintain the temperature in the heap. Cost of Sales The cost of establishing and operating the scheme to date is as follows:

It should be pointed out that the above costs cover a considerable amount of experimental work, In order to improve the working conditions and generally increase the efficiency of the plant it is proposed to expend a further £lOOO. The whole of this expenditure is in the form of capital expenditure and is of a nonrecurring nature.

The material is selling very readily both in the borough and the surrounding district. Actually an offer has been received from a mercantile firm to take the whole output.

The present selling price is £2 per cubic yard or 5s per manure bag, both prices including delivery within the borough. There are approximately 24 bags to one ton and ton lots are being sold at £5. It is expected that some 600 to 800 cubic yards will be manufactured this year. When it is possible to organise for the collection of the whole of the available organic refuse in the borough the annual manufacture will be in the vicinity of 1200 to 1600 cubic yards. The organic portion of the ordinary household refuse has not so far been handled, as during 1942, in order to conserve petrol, only the ashes, bottles and tins were collected.

Arrangements are now almost completed for the reinstatement of the full service. It is proposed that a “dual tin” system be used, which will involve the provision of an additional tin for the organic portion of the refuse. A large quantity of rubbish cans has been prepared for sale to householders at a reasonable cost. The dual tin system has worked successfully in England and America; in fact, the latter country has a triple, tin system. The author has been informed that a dual tin system was operated with success in the city of Nelson in connection with a municipal pig farm. It is not, therefore, anticipated that any difficulties in instituting the method of collection and separation will be experienced. Agricultural Aspect The results obtained by the use of the compost as an organic manure have been very satisfactory, the author himself having obtained good results in both the vegetable and flower garden. This experience is shared by others in the town. Also tests carried out in the growing of lettuces from seed by the soil survey division, Department of Scientific and Industrial Research, Wellington, proved that Dannevirke composts gave quick responses far in excess of those given by equivalent quantities of dried blood or sodium nitrate. As the stock of fully matured compost available at the. commencement of the current planting season was somewhat limited, consequently sales were also limited. It is, however, anticipated that a heavy demand Will be made on the product in the autumn, particularly by farmers in the Central Hawke’s Bay area. General From the results so far obtained it is quite apparent that the venture will earn a return for the ratepayers, which return should more than cover the expenditure incurred in the collection and composting of refuse and sludge. In considering the adoption of a municipal composting scheme the two following factors are of paramount importance: — 1. Local conditions must first be thoroughly investigated to establish

the need and possibilities of composting and the ultimate potential value to the area.

2. The scheme must be established by some competent person and thereafter operated under close supervision by properly-trained personnel. The author’s experience and knowledge would suggest that the latter factor is of the greater importance and cannot be over-stressed, while it would be incorrect to say that the process cannot be carried out without creating both a fly breeding and smell nuisance. On the other hand unless very close and careful attention is given to this aspect the creation of a serious nuisance would most certainly result. The large scale work carried out in Dannevirke has definitely proved that municipal composting is practicable without creating a nuisance of any kind—in fact, this aspect has been largely instrumental in convincing many hitherto sceptics. It should also be mentioned that there is a total absence of rats.

However, as mentioned above, this has only been achieved by very rigid supervision of the work as it was found that at any.stage., particularly in the first two or three months, the potentialities of creating a nuisance were great. The experimental work carried out in Dannevirke has attracted widespread interest. The author has had numerous inquiries from local authorities throughout New Zealand, also as ‘far afield as England, Australia and Fiji. Some three hundred persons from all over New Zealand have visited the site. They comprise a very general cross-section of the community, such as borough, city and county engineers, councillors, farmers, ochardists, market gardeners, chemists, doctors, health officials, Government officials representing State Departments of Ministry of Works, Public Works, Health, Agricultural and Department of Scientific and Industrial Research and laymen, etc. Some criticisms have been made of the scheme, one being that selected refuse is being used. This is incorrect, as any and all kinds of organic refuse are being used, as will be seen from the list given earlier. Another and more general criticism is the, amount of nitrogen recoverable by municipal composting. It should, however, be pointed out that it is the production of humus which is of importance.

'The physical and bacteriological condition of humus may well prove to be of greater importance than its chemical composition. In any case it is an acknowledged fact that fertilisers cannot take the place of humus in soil fertility, although they may be required to supplement it. Further, the chemical aspect of composts is not as yet well established. Again it is not. a question of how much or how little humus or compost can be produced; the vital point is, that by existing methods of disposal; huge quantities of organic matter are being wasted at a time when it is known that humus is required for soil fertility. Why, then, should municipalities be permitted to go on pouring sewerage into the sea and rivers and burning or burying refuse at con-siderable-cost to the ratepayers when these materials could be utilised and a financial saving made for the ratepayers—apart from any consideration of the likely benefit to the land and thus to animals, plants and humus. This latter aspect is incidental to the main issue, but none the less important. Further, pouring of sewerage into the sea and rivers has led to pollution, and the burning of refuse is likely to create a smoke nuisance. Progress, or the less controversial term, natural evolution, causes changes of habit, while prejudices which are of significance in one age become music hall jokes of another. Conclusions From the experience gained in Dannevirke the position can be summarised as follows: 1. Municipal composting provides a sound and hygienic method for the disposal of difficult organic wastes. 2. Municipal composting improves both public amenity and sanitation. 3. Municipal composting should earn a return for the ratepayers. 4. Municipal composting, makes it possible to return to the land both town refuse and town sewerage, by way of available organic manure which should be the ultimate, aim of all who are responsible for the disposal of these valuable wastes. 5. Municipal composting appears to be a practical possibility for most towns. MUNICIPALCOMPOSTING (Editorial Comment in “Board and Council,” December' 10, 1947.) In spite of the ruination which history has taught us follows from an inadequate return to the. land of organic waste matter, it is only in recent years that much heed has been paid in New Zealand to the question of preserving the humic content of the soil. Most towns in the, Dominion have sewage schemes, hut activities have been directed to the problem of disposal rather than of utilisation of wastes. The ancient cities which foundered on the exhaustion of their soil fertility, had sewers too. The deserts on the coastlands of North Africa, so well known to New Zealand soldiers, were once the rich and fertile plains of Carthage. Such devastating changes as this have been brought about through the delinquencies of mankind—deforestation, overcropping and failure to maintain soil fertility. To combat soil erosion in its various forms catchment boards have been set up in New Zealand, but to deal with the just as vital matter of soil fertility, no such definite move has yet been taken. The setting up of a Royal Commission to investigate the problem has been approved by Parliament, but Cabinet approval is still awaited. In the meantime the idea of municipal comppsting as a means of providing some return to the soil of the much-needed humus, is gaining in popularity. A valuable lead in this direction has been given by the Dannevh'ke Borough engineer, Mr Truman, a description of whose scheme is published elsewhere in this issue (reprinted above). The value of municipal composting is now fairly well recognised. The main factors preventing schemes from being undertaken seem to be questions of finance,

suitable sites and the availability of plant. The way in which* these have been overcome at Dannevirke suggests that they present no serious obstacle.. The costs of and returns from the Dannevirke scheme, which is still only in the experimental stages, point to a financial gain rather than a burden on the ratepayers. This is further emphasised by experience overseas; in fact, all the conclusions drawn by Mr Truman from experience in Dannevirke are borne out by overseas experience. The Municipal Association has already endorsed the principle of municipal composting and the newlyelected councils should make the matter one of the first for immediate action. All the evidence on the subject clamours against the present war being waged against Nature, and demands instead a war against waste.

Labour .. £549 19 1 Plant and Materials .. 435 14 9 Miscellaneous Cost ... 29 4 9 £1014 18 7