The yield from the individual ton may seem to be too small to be worth considering. But reflect upon the normal consumption of bananas in this country! The annual importation ranges from 7,000,000 to 8,000,000 bunches, which represents an equal number of stalks—mere refuse. According to Mr. Ellis, under normal conditions the stalks average a round 4,000 in number weekly in Leeds alone. When stripped, the average weight of the stalk is 4 lb., so that there are 16,000 lb. of stalk wasted every week in the Yorkshire city. Properly treated, about 1,340 lb. of dried matter, rich in potash, could be secured therefrom to feed the land.
Applying the reclamation process to the whole of the country, it should be possible to secure from 28,000,000 to 32,000,000 lb. of banana stalk, giving from 2,350,000 to 2,700,000 lb. of dried matter containing 13·7 per cent. of potash—from 321,000 to 370,000 lb. of potash—during the year. If the stalks were carbonized they would yield from 675,000 to 771,428 lb. of ash containing from 320,000 to 366,000 lb. of pure potash. This may represent but a small fraction of the total agricultural consumption of 22,000 tons per annum, but it would be a contribution from a waste product which now has to suffer destruction with the total loss of all beneficial values. The primary difficulty, of course, would be in connection with the recovery of the stalks, but a reorganization of our selling methods, such as the compulsory return of the denuded stalks to the fruit markets for ultimate bulk collection, would go a long way towards the solution of this problem. The question arises as to whether we should not find it advisable to dispose of all vegetable and fruit waste along individual lines, inasmuch as other refuse of this character contains potash in varying proportions. By the establishment of a small, inexpensive and suitable furnace in the markets for the treatment of all waste it would be possible to recover valuable fertilizing ash in sufficient quantities to allow bagging and sale upon the spot. Such treatment would be no more expensive than that in operation to-day, involving transport to, and combustion in, the destructor.
Tobacco is another product rich in potash, particularly the ash. Here recovery would prove an exceptionally difficult task, but it has been suggested that the conservation of ash and the discarded ends of cigars and cigarettes from clubs, hotels, and other centres possessing smoking-room amenities might be encouraged. The total during the year would be impressive. Certainly collection from such quarters would not be attended with difficulty, while the price payable for the residue might be made sufficiently attractive as to induce the attendants to garner this residue.
So far as the exploitation of waste for potash content in this country is concerned only one established practice, which is extremely precarious, has ever met with recognition upon a limited scale. This is the extraction of the precious substance from kelp, or vraic, to mention two of the names under which the familiar seaweed is known. The treatment of this waste is conducted along crude lines, but it is doubtful whether our available knowledge could suggest a more skilled method. British seaweed does not resemble that recovered off the coasts of Japan and the Pacific seaboard of the United States, where the recovery of potash from this residue from the sea has become an established industry.
Yet Britain need not pay a further penny tribute to Germany. We are able to free ourselves entirely from the German yoke, and can confidently look forward to such a happy state of affairs so long as the steel age reigns. The raw material dumped into the blast-furnaces carries a certain proportion of potash. But it has always been permitted to escape. Being associated with the fine dust it was borne through the flues, a certain proportion being deposited therein, but at least 90 per cent. was irretrievably lost. Threatened famine compelled us to devote attention to the possibility of arresting this fugitive potash, and our efforts have met with success. The furnace flue dust is trapped to be passed through a special plant for further treatment. Previous to the war the economical and fiscal conditions would not have permitted such a practice with profit. The requisite plant is necessarily somewhat costly to install and to operate. Had we decided upon such a course of action the Germans would promptly have forced the process into bankruptcy by resort to price-cutting tactics. The Potash Syndicate was exceedingly powerful, and it never hesitated to wield its power, as the United States of America have every occasion to remember when, a few years ago, it came into conflict with the German Government in regard to inter-trading, and was brought full tilt against the potash ace of trumps. Had we ventured to dispute the German monopoly by any attempt to exploit our flue-dust we should have upset a pretty kettle of fish and should have been bludgeoned into surrender. It is to be hoped that the authorities will hesitate to play so completely into the enemy’s hands again, although this is fortunately very unlikely because the Teuton monopoly has been broken effectively by the restoration of Alsace-Lorraine to France which carries, among other numerous advantages in raw materials, the immense potash deposits which the Germans worked so profitably to their own ends. Still, even this achievement should not dissuade us from continuing to exploit the waste dust recovered from our blast-furnaces. Immense quantities of the essential material are forthcoming, the potash content of which varies from 3 to 13 per cent. As output increases it should be capable of recovery at a decreasing figure and at one which should enable the indispensable product to be placed upon the market at a competitive figure.
The foregoing does not exhaust the list of potash-yielding wastes possible of exploitation. It is recoverable from wool in the washing process; feldspar also contains potash; farmyard manure will yield it in attractive proportions—from 9 to 15 lb. per ton; while liquid manure also carries it to the extent of 40 to 45 lb. per 1,000 gallons. Thus it will be seen that we need never suffer from an actual famine in potash if we but resolve to exploit our wastes to the utmost.
I have referred in a previous chapter to the value of leather waste as a fertilizer. Five years ago we did not pursue this problem along determined lines, mainly because we did not really understand its preparation, while our farmers did not regard the product then marketed with favour. But to-day there is a welcome change both in productive methods and the agricultural attitude. Some large plants for the treatment of the leather waste have been laid down and are being brought into operation. Two distinctive treatments are being followed. In the one instance the curried leather—sheer residue from the boot factories possessing no other possible use—is being submitted to treatment for the extraction of the greases and fats used in the dressing processes. In the second system these fats, owing to their low grade and as yet absence of possible industrial use, are being ignored, although they disappear for the most part from the product in the course of treatment. Otherwise the two methods are broadly identical. The leather is carbonized and then reduced to a dark greyish powder. In this form it meets with the full approval of the farmer, and, as its nitrogen content is said to range up to 9 per cent., it is meeting with ready disposal, the demand at the present moment being far in excess of supply. At one works an output of 60 tons a week is being recorded, which incidentally indicates the quantity of leather waste incurred in our boot-producing factories.
I have also drawn attention to the extent to which fish scrap is now being treated, and here again highly satisfactory developments are to be narrated, the trade, especially in regard to the production of fertilizer, being in a flourishing condition. Fish guano appeals to the farmer, owing to its high content of ammonia and phosphate which aggregate approximately 20 per cent. At one fish waste reducing factory the output is 20 tons every 24 hours, the plant being run on continuous lines, but arrangements are being completed to double the capacity to secure an output of 40 tons during the 24 hours. Hitherto the farmer has not been completely enamoured of fish manure because in certain instances, notably in the treatment of the oily fish, such as the herring, the grease content, which was as anathema to him, was somewhat heavy. But the perfection of the solvent extraction process which I have described, and whereby the oil contained in the finished fertilizing meal can be reduced to as low as 1 per cent., has completely removed this disability.
As is well known, bone-meal is a popular fertilizer. In this instance, although the fatty content of the crude bones may be high, the processes of degreasing have been advanced to such a stage of perfection as to bring about virtually the total elimination of this objectionable constituent. The fertilizer, if properly prepared, will not carry more than 1 per cent. of grease. The bones undergo a very thorough treatment, because this waste is able to feed several industries.
Sewage is also coming more widely into favour as a fertilizer, as I explain in another chapter, while residues incurred in other ramifications of industry are now being carefully collected instead of being permitted to dissipate into the air or to pass to the furnaces for combustion. The dust arising from the reduction of woollen rags into shoddy forms an excellent hop manure. Dried blood is another first-class fertilizer—in fact it would be difficult to enumerate all the wastes which can now be profitably exploited for their soil-nourishing values. Speaking broadly, it may be stated that any refuse which, upon investigation, is able to yield 3 or more per cent. of nitrogen demands further examination for the discovery of the cheapest ways and means to reduce it to a fertilizer for sale at an attractive figure. If price be right no apprehensions need be entertained concerning disposal; the farmer will absorb the plant food, to nourish his crops, with eagerness.