LIVING ON WASTE
War is Hell. So said Sherman, and it is a verdict with which the whole
world will agree. But war is also a powerful educating force. If
any convincing testimony upon this point were required we have only
to reflect upon the effective manner in which the recent European
conflagration caused the British nation to revise its methods and
practices. The stress of war, ravages by submarines, depletion of
transport facilities by sea, road, and rail, and the shortage of crops
and labour, compelled the community to consider the food question in a
light totally different from that with which it was regarded during the
days of cheapness and plenty. We were forced to digest lessons which
under normal conditions we would have ignored in contempt. Whether the
changes wrought in our complex social and commercial life are destined
to be permanent in character is another question, but the continuation
of high prices is tending to consummate this end, the process being
assisted by the reflection that the good old days are destined never to
return, at least not for many years to come.
In the previous chapter I have recounted how the engineer is now
striving to conserve rather than to destroy what we throw to one side
as of no further use. By inventive ingenuity he is endeavouring to
bring home to our local authorities how to extract further utilitarian
value from what the household discards. The question immediately arises
as to what extent this tendency towards preservation and construction,
as opposed to destruction and loss, is being supported in a practical
manner by the authorities concerned.
It is to be feared that, considered on the whole, the seeds which are
being sown are falling on barren ground. However, here and there our
civic and municipal authorities, especially those who evince a distinct
pride in being numbered among the pioneers of progress, are fully alive
to the possibilities of the problem, and are leaving no stone unturned,
nor sparing any exertion, to bring home to the public at large that
refuse is merely matter in the wrong place. In some instances this
reversion to rigid economical methods is not of modern record, the
practice of salvage or recovery of abandoned products having been
practised along more or less comprehensive lines, as indicated by
scientific thought, for many years past.
The city of Glasgow is able to point to a convincing record of what
can be achieved in this direction. In the years 1908-9 the fathers
of the progressive Scottish city derived £41,000--$205,000--from
this source, while during the ten years ending 1918 what is commonly
regarded as rubbish and useless has been induced to yield no less than
£50,300--$251,500. Surely what can be achieved in one city is equally
possible of attainment in every other community throughout the British
Isles to a greater or lesser degree!
Glasgow has evolved its own organization for retrieving and utilising
the city refuse and in accordance with the conditions which obtain in
the locality. Speaking generally, the system may be described as one
of separating the saleable from the unsaleable. Previous to the year
1917 efforts were devoted mainly to the preparation of fertiliser from
the contents of the domestic dust-bin, as well as the recovery of
tins, but, owing to the high prices which other so-called waste was
commanding, and in deference to the national appeal towards greater
economy, the reclamation of other materials was taken in hand with
highly gratifying results.
The refuse of the city is collected in the usual manner and conveyed
to the depot. It is weighed upon receipt. It is then dispatched up
an inclined roadway to a tipping floor, where the vehicles discharge
their loads through shoots. Beneath the latter are disposed horizontal
revolving riddles of conical form. The fine refuse and cinders escape
through the grids, but the bulky material is carried forward to be
ejected on to a travelling conveyor.
The ashes and cinders which fall through the open mesh of the first
riddles are caught by a second and stationary screen. The mesh of
this sieve being finer only allows the dust to escape to fall into
a mixing machine. Here it is combined with a regulated quantity of
excrementitious matter drawn from an overhead tank. The materials
are thoroughly blended, and the mixture ultimately falls direct into
railway wagons. In this way all intermediate handling is obviated. This
material constitutes a first-class fertilizing agent, is keenly sought
by farmers, and accordingly meets with a ready sale.
The cinders, arrested by the secondary stationary screen, are collected
in a similar manner. They are not sold, but dumped into the bunkers
of the works to fire the boilers, thereby assisting materially in the
generation of the power necessary to drive the plant.
The bulkier material remaining in the revolving conical grid is
discharged on to a conveyor. While being moved forward all material
of value, such as waste-paper, tins, scrap-metal, waste-food, rags,
bones, glass and so on are picked off by hand to be thrown into bins.
The manual labour employed to carry out this task of segregation may be
considered to be an adverse cost factor. But against this expenditure
for separation by hand must be set that formerly entailed in the
destruction or other disposal of this material. Accordingly, all things
considered, it may be accepted that the revenue derived from this
source virtually represents money saved.
In addition to the recovery of paper from the above-mentioned
refuse the Cleansing Department also maintains a special service
for the collection of such waste from offices, warehouses, and
private residences throughout the city area. This procedure has been
in operation for many years, but, owing to the scarcity of paper
encountered during the war, and the need which consequently arose
to display accentuated enterprise in this direction, an auxiliary
collecting service was inaugurated. It was conducted by the members of
the Women’s Volunteer Reserve, who received a percentage of the profits
arising from the sale of the waste-paper thus gathered.
So far as the waste-metal--light scrap, tins, and other odds and ends
of a metallic nature--is concerned this was formerly sold in the form
of detinned compressed billets. Under the present contract this is
delivered to the contractor in the condition in which it is received.
But it is quite possible that, at some future date, there may be a
reversion to the baling process which formerly obtained. In view of
this fact it has been deemed advisable to bale a certain proportion
of the recovered metal merely in order to maintain the hydraulic
compressing plant in good working conditions. The practice is to
separate and to classify metallic material under one or other of six
headings--bright tins, galvanized metal, light iron (black), cast iron,
enamelled ware, and burned tins respectively.
While the Cleansing Department hitherto has not devoted any attention
to the recovery of garbage from the refuse for conversion into
pig-food, it is possible that this issue may be undertaken at a future
date. The authorities have the suggestion under serious consideration
with a view to its adoption.
The clinker question commands the attention of the Glasgow authorities,
as it does all other communities equipped with facilities for carrying
out refuse destruction by incineration. But, so far as this city
is concerned, the problem does not bristle with perplexity as is
invariably the case. The residuum from the furnaces of the Corporation
works is mechanically screened into five varying grades, to meet the
requirements of contractors who find it eminently adapted to their
particular needs. No difficulty has yet been experienced in regard to
the disposal of this article, a ready sale always having prevailed for
the stocks available.
That the reclamation of the utilitarian contents of the domestic
dust-bin is distinctly remunerative to the Glasgow civic authorities is
reflected from a perusal of the revenue derived from the recovery and
disposal of the city’s refuse during the year ended May 31, 1918. The
sales’ record is as follows:--
---------------------------+---------------+---------
Materials. | £ s. d. | $
---------------------------+---------------+---------
Waste-paper | 8,993 14 5 | 44,969
Old tins, light iron, etc. | 2,684 17 9 | 13,425
Clinker | 718 10 10 | 3,592
Sundries | 72 14 5 | 363
---------------------------+---------------+---------
Total | £12,469 17 5 | $62,349
---------------------------+---------------+---------
To the above total there remains to be added the revenue derived
from the sale of the prepared manure, arising from the admixture of
the finely-screened dust and excremental material. This realized
£6,718 17s. 8d.--$33,594--bringing the grand total to £19,188 15s.
1d.--$95,943. In this return the cinders are totally ignored, but,
seeing that they constitute a highly serviceable fuel, the saving
in the coal-bill, which their use secured, should be taken into
consideration.
It is necessary to explain that, inasmuch as the thorough separation of
the material is only of recent date, previous operations having been
confined to the recovery of paper, old metal and the preparation of
the fertilizer as already mentioned, the item “Sundries” cannot extend
any criterion as to the results now being recorded, nor of the revenue
derived from the recovery and disposal of the additional articles.
The successful conversion of the volume of dust, comprising about 50
per cent. of the aggregate, into a marketable fertiliser, offers a
satisfactory solution of a complex and perplexing problem. But when the
dust is coarser and yet deficient in “bite” or gritty characteristic,
its disposal is not so readily consummated because its possible
applications are thereby severely narrowed down in number.
Speaking generally, the utilization of the fine dust may be said to
present a vexatious question. While it forms an excellent ingredient
for a compounded fertilizer, it is not a simple matter to discover an
inexpensive, and preferably second, refuse constituent of approved
manurial value with which to associate it. The majority of the
ingredients advocated as complying with the desired requirement possess
too high an independent fertilizing value for such an application.
In itself the dust is of very low soil-feeding power, and so active
investigation is being pursued in anticipation of the discovery of a
satisfactory adjustment to this question.
Another enterprising illustration of what can be achieved with
domestic, office and warehouse refuse, both organic and inorganic,
is extended by the Port of Liverpool. Here, again, the developments
to be recorded in this connection are not attributable to the war,
although the last-named factor was responsible for the conduct of the
reclamatory process upon a more intensive scale. Liverpool is somewhat
peculiarly situated among the importing centres of the United Kingdom
seeing that it is probably the largest distributing centre for American
foodstuffs for this country. Consequently, as is only to be expected,
very considerable quantities of food which have suffered such damage
during transit or demurrage as to become unfit for human consumption
have to be handled. Under the old _régime_ all organic waste of this
character was either consigned right away to the destructor, or was
perfunctorially treated to be sold as manure. Neither science nor
brains was displayed in its disposal. The shortest way out of the
difficulty was accepted as being the most effective in the public
interests. But Liverpool was not the only port to follow such summary
practice. It was common to all ports of the country in greater or
lesser degree. The public loses heavily from the observance of such
deprecatory measures, especially when it is borne in mind that such
traffic runs into tens of thousands of tons during the course of the
year. But under pre-war conditions, owing to the plentitude of supplies
and the wide distribution of the losses incurred, the financial effect
was scarcely felt by the unit of the population.
During the war a loud wail went up because a number of hams and a
quantity of bacon had been found in a decomposed condition at a certain
port. Had this occurred during pre-war days not a word would have found
its way into the public press, and the destructor alone would have
known of the incident. But because under war conditions the public
was directly affected--was clamouring for this particular article of
food--the wastage was declared to be intolerable. Fortunately, in this
instance, owing to our having become more enlightened, the spoiled food
was not totally lost. The fat was reclaimed, while the residue was
turned to its most profitable account.
At Liverpool, as at other centres where a vigilant eye is maintained
upon the clock of progress, it was speedily discovered that the methods
of handling such refuse were distinctly deprecatory. It was decided to
introduce improved practice. One material was treated as an experiment,
and the process was found to be profitable. Gradually other condemned
articles of food were taken in hand. This logical development of
salvage was continued, until to-day there is very little material
entering into the composition of the Liverpool dust-bin which does not
find some one or other useful application.
It was learned from studied investigation that waste-food products
collected with the refuse of the city might be classified into five
broad divisions, namely butchers’ and fishmongers’ offal, damaged fruit
and vegetables, damaged eggs, damaged canned foods, such as meat, fish,
milk and so forth, as well as warehouse sweepings. Over and above this
assortment, of course, came the miscellany to be found in every ash-bin
drawn from the home. To ensure the receipt of the offal from tradesmen
a special and separate collection from all retail shops dealing in fish
and greengrocery was inaugurated. Subsequently, to prevent the wastage
of swill suitable for the sustenance of pigs, a special collection from
private houses was introduced.
In every city the isolation of the swill from the general material
consigned to the dust-bin though freely urged is a somewhat difficult
issue to carry into practice. Segregation at the source is imperative
to ensure the maximum results being attained. But the Liverpool
authorities overcome the obstacle very satisfactorily. The residents
were notified of the intention of the department charged with this
duty, while officials were detailed to visit and to explain to
residents the proposals, and to extend advice upon what, and what
should not, be thrown into the dust-bin. Moreover, the City Fathers
undertook to provide each house with a special receptacle for the
swill, and to collect it at frequent intervals. Experience proved that
collection twice a week sufficed to meet every requirement.
But, as a rule, when the suggestion is made that local authorities
should provide special receptacles for swill, demur is made on the plea
that such a procedure must entail further capital expenditure. Yet it
can be carried out along very inexpensive lines if attacked in the
proper spirit. So far as Liverpool has been concerned it was even found
possible to turn a waste article to such account. Among the flotsam and
jetsam sent to the corporation depots for disposal were thousands of
tins measuring 9 × 9 × 13 inches, originally used for the conveyance of
oil to this country. Examination revealed the circumstance that these
discarded receptacles could readily be converted into swill-pails,
their dimensions and construction admirably adapting them to such
a duty. Forthwith they were cleaned, one or two minor alterations
carried out, and then painted. The cost of adaptation was less than
1s.--25 cents--per tin. These were then issued to the residents who
expressed readiness to co-operate with the efforts of the authorities,
and proved a complete success. It has often been advanced by local
authorities that the residents will never collaborate in such schemes
of segregation at the source, declining to be bothered, but the
experience gained at Liverpool does not support such a contention. The
inhabitants of the city astride the Mersey responded very promptly to
the request to save and segregate their swill, the result being that
enormous accumulations of potential and valuable pig-food were secured.
Swill supplies being assured, the next step was to handle this waste
at the depot, and to prepare it for the piggeries. The City Engineer,
Mr. John A. Brodie, M.Inst.C.E., advanced a complete solution to this
problem and along economical lines. A number of old pitch boilers
and other plant was lying idle at the depot. This was turned out,
overhauled, rigged up and coupled up to the steam generating equipment
of the destructor. The household swill was cooked in these vessels,
and in this manner a first-class pig-food was produced. To ensure the
consumption of the swill thus obtained the Corporation installed its
own piggeries and poultry runs upon its farms. The swill, while still
hot, was conveyed to the piggeries in the municipal motor wagons and
doled out. Private pig-raisers were also at liberty to obtain the swill
in the heated condition if they cared to fetch it. This facility was
readily accepted, inasmuch as it saved the pig-keepers the trouble and
time of conducting collection from houses in the conventional manner
and then boiling it upon their farms for their animals.
Continuous development of the reclamation of waste problem has been the
policy of the Liverpool civic authorities. Satisfied with the pecuniary
and other results attending their initial efforts the City Engineer
installed an inexpensive and complete plant working upon the Scott
system, described in another chapter, for the full reclamation of the
material contained in the city refuse. It was laid down at the central
depot primarily to treat the meat, fish, and other organic offal,
increasing quantities of which were forthcoming. The plant in question
comprises a digester, dryer, vacuum pump, disintegrator and fat tanks.
Electric drive is employed throughout, the necessary power being drawn
from the municipal generating station.
The digester, made of steel, 7 feet long by 3 feet in diameter, is of
sufficient capacity to receive one ton of refuse at a time, and works
at a pressure of 60 lb. It is charged from the top and emptied from the
bottom. It works upon the jacket principle, and the necessary steam may
be admitted both at the top and bottom as desired. Top and bottom cocks
are fitted for drawing off all fatty and oily liquid for the fat tanks,
and also to draw off the liquor. About four hours are required to treat
the charge.
The vacuum dryer is a drum, 4 feet 6 inches deep by 5 feet in diameter,
and is also able to receive a charge of one ton. Top and bottom
facilities, for charging and emptying respectively, are provided.
Within the vessel rotating blades are disposed to keep the contents in
agitation during treatment, these blades making about 25 revolutions
per minute. All foul gases arising during the process are drawn off
by a vacuum pump, and are led to the furnaces to be consumed, thereby
being rendered innocuous before escaping into the atmosphere.
The disintegrator is a cast-iron cylinder provided with a continuous
automatic feed. Within the vessel are set a number of steel arms which
run at a very high speed--about 2,500 revolutions per minute--which
break up and thoroughly disintegrate the refuse introduced until it is
able to pass through the meshes of the screen placed at the bottom of
the machine.
The process is very simple. The refuse is dumped into the digester
which, upon being filled, is sealed. Steam is turned on, and the
resultant cooking releases all the oleaginous constituents of the
contents, which are floated off through the cock to be led to the
fat-recovery tanks. The cooking is continued until the raw waste has
shed every drop of recoverable oil and grease. The digester is then
emptied, pressed, and the cooked material passed to the dryer to be
dried, thence to the disintegrator to be pulverized or ground to the
required degree of fineness.
The fatty and oil liquors drawn from the digester fall into a tank,
and the fat and grease collecting on the surface are skimmed off to
be passed to a lower tank. All tanks are kept at a certain degree of
temperature by means of a steam-heated coil. The fat and oil reclaimed
in this manner are subsequently treated for their yield of glycerine,
the final residue entering into the preparation of soap and other
articles.
The solid residues recovered from the disintegrator, representing the
fibres from the meat, fish offal and other solid matter, constitute an
excellent poultry food. According to the analyses which have been made
it is rich in the albuminoids and phosphates.
While the foregoing naturally represents the foremost and greatest
phase of salvage activity pursued by the Liverpool Corporation it
by no means exhausts their efforts in this direction. Other refuse
is recovered and treated for some one or other specific commercial
purpose. All bones are collected, washed, and boiled to secure the fat,
the solid matter afterwards being ground into meal. Vegetable refuse,
of which large quantities are forthcoming, especially from the markets,
are dried and stored, having been found useful as a constituent for
poultry foods. Fish, both offal and unsold inedible surplus, is
converted directly into fertilizer. Wooden refuse, recovered from
dust-bins and other sources, is heated at low temperature to allow
carbonization for sale as charcoal. Large quantities of straw,
both clean and soiled, are also brought in, being recovered from
packing-cases and crates. The clean straw is segregated to be chopped
finely, and as such meets with a ready sale among poultry-raisers
because it constitutes a very effective scratching material. The dirty
straw, together with soiled paper and old wooden boxes incapable of
other treatment, as well as other light refuse, are burned in a special
furnace which has been installed, care being observed to collect the
ash. As the latter contains approximately 12 per cent. potash it
forms a first-class fertilizer. Banana stalks are likewise rich in
potash, and so, by submitting the stalks, large quantities of which
are forthcoming from the fruit markets under normal conditions, to a
special treatment, this potash is recovered and is turned over to the
soap-makers. Oyster shells are washed, calcined, and then ground for
sale as grit to poultry-raisers.
Damaged and condemned eggs are frequently received in large quantities
from the docks, warehouses and wholesale establishments. One
consignment numbered no fewer than a quarter of a million. Instead of
being used as fuel for the destructor, these eggs are boiled, then
chopped, dried and together with the shells are finely ground into meal
for use as chicken food.
Consignments of ham and bacon are often received in heavy quantities at
times from the docks. This inedible food is submitted to treatment to
secure the various commercial by-products such as oil and grease, the
residue being ground up into meal.
From the foregoing it will be realized that Liverpool is not
permitting much waste of any commercial character to find its way to
the incinerator. The wise policy now being pursued is bearing fruit.
The prices which have been, and still are being, realized, render
the trouble and effort expended well worth while. The meal made from
fish offal, after the extraction of the oil, has fetched as much as
£25--$125--per ton, while the butchers’ offal, after similar treatment,
has commanded an equally satisfactory price. Even the refuse gathered
from the households of the city, and capable of being turned into
poultry-meal, which exceeds 20 tons a week, is promptly sold at prices
ranging up to £15--$75--per ton. The possibilities attending systematic
collection from private residences have also been conclusively
established, and at the moment the Corporation is gathering a round
1,000 tons of such waste from certain houses in the course of the
year. Reclaimed tins, after being washed and dried, have realized up
to £8--$40--per ton, while, to meet the enhanced request for organic
manure, an excellent fertilizer is being prepared from certain
materials which come into the hands of the authorities, or accrue from
the practice of waste-reclaiming. The Corporation are able to dispose
of this fertilizer with comparative ease at the rate of 50,000 tons
during the year.
Other towns are able to point to comparable achievements in connection
with the exploitation of waste incurred within their areas. Some of
the small communities are even able to produce some startling records
in this connection. If all our civic and municipal authorities could
be brought into line and raised to the productive level of Glasgow or
Liverpool, the cumulative benefits to the nation would be enormous and
far reaching. But, as yet, only a fraction of what might be secured is
being turned to useful account. For instance, it is computed that 3,000
tons of first-class pig-food could be recovered from London alone every
week--this in itself would show a heavy yield of fats and greases if
properly treated--but at present it is being wasted.
Merely because foodstuffs--meat, fish, eggs, fruit, and other
commodities innumerable of a perishable nature--are condemned as being
unfit for the service of man, that is not to say they have completed
their mission in the scheme of things ordained by a so-called high
civilization. Doubtless they assist in the manufacture of excellent
paving-stones, but although we are in dire need of houses and this is
the concrete age, that is not a sufficiently reasonable excuse for
withdrawing nitrogenous products from the cycle of Nature.